Introduction to Cisco Gigabit Ethernet SFP Module

Gigabit Ethernet represents a merging of 8022.3 Ethernet and ANSI X3Tll fiber channel technology. There are five physical layer standards for Gigabit Ethernet using optical fiber (1000BASE-X), twisted pair cable (1000BASE-T), or shielded balanced copper cable (1000BASE-CX). Among them, 1000BASE-X is used in the industry to refer to Gigabit Ethernet transmission over fiber, where options include 1000BASE-SX, 1000BASE-LX, 1000BASE-LX10, 1000BASE-BX10 or the non-standard -EX and -ZX implementations. Cisco, the largest networking company in the world, provides a range of SFP transceivers for Gigabit Ethernet applications, including 1000BASE-T SFP, 1000BASE-SX SFP, 1000BASE-LX/LH SFP, 1000BASE-ZX SFP, or 1000BASE-BX10-D/U SFP on a port-by-port basis. This post mainly introduces these five Cisco Gigabit Ethernet SFP modules for your reference.

Cisco 1000BASE-SX SFP

The 1000BASE-SX SFP is compatible with the IEEE 802.3z 1000BASE-SX standard. It operates on legacy 50 μm multimode fiber links of up to 550 m and on 62.5 μm FDDI (Fiber Distributed Data Interface ) grade multimode fibers up to 220 m. It can support up to 1 km over laser-optimized 50 μm multimode fiber cables. GLC-SX-MM and SFP-GE-S are the two earliest configurations of Cisco 1000BASE-SX SFP. Later GLC-SX-MMD (as shown in following picture) with DOM functionality appears.

Cisco 1000BASE-LX/LH SFP

The 1000BASE-LX/LH SFP is compatible with the IEEE 802.3z 1000BASE-LX standard. It operates on standard single-mode fiber optic link spans of up to 10 km and up to 550 m on multimode fibers. When it is used over legacy multimode fiber type, the transmitter should be coupled through a mode conditioning patch cable. This transceiver is joint with dual LC/PC connector. And the transmit and receive wavelength ranges from 1270 nm to 1355 nm.

Cisco 1000BASE-EX SFP

The 1000BASE-EX SFP operates on standard single-mode fiber optic link spans of up to 40 km. A 5-dB inline optical attenuator should be inserted between the fiber optic cable and the receiving port on the SFP at each end of the link for back-to-back connectivity. And the transmit and receive wavelength ranges from 1290 nm to 1335 nm.

Cisco 1000BASE-ZX SFP

The 1000BASE-ZX SFP operates on standard single-mode fiber optic link spans of up to approximately 70 km. This transceiver provides an optical link budget of 21 dB, but the precise link span length depends on multiple factors such as fiber quality, number of splices, and connectors. When shorter distances of SMF (Single-mode Fiber) are used, it might be necessary to insert an inline optical attenuator in the link to avoid overloading the receiver. A 10-dB inline optical attenuator should be inserted between the fiber optic cable plant and the receiving port on the SFP at each end of the link whenever the fiber optic cable span loss is less than 8 dB.

Cisco 1000BASE-BX10-D/U SFP

The 1000BASE-BX-D/U SFP is compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standard. It operates on a single strand of standard SMF. A 1000BASE-BX10-D device is always connected to a 1000BASE-BX10-U device with a single strand of standard SMF with an operating transmission range up to 10 km. The communication over a single strand of fiber is achieved by separating the transmission wavelength of the two devices. That is to say, the 1000BASE-BX10-D transmits a 1490-nm channel and receives a 1310-nm signal, whereas 1000BASE-BX10-U transmits at a 1310-nm wavelength and receives a 1490-nm signal. Then a WDM (Wavelength Division Multiplexing) splitter integrates into the SFP to split the 1310-nm and 1490-nm light paths.

Conclusion

These Cisco SFP transceivers offer a convenient and cost effective solution for the adoption of Gigabit Ethernet in data center, campus, metropolitan area access and ring networks, and storage area networks. Besides, Cisco also provides other transceiver modules with high performance, such as 40GBASE-CSR4 QSFP+ transceiver (Cisco QSFP-40G-CSR4), 40GBASE CFP transceiver (Cisco CFP-40G-LR4), 100GBASE CXP transceiver (CXP-100G-SR10), etc. These Cisco transceivers can support Ethernet, Sonet/SDH and Fiber Channel applications across all Cisco switching and routing platforms.

40G QSFP+ Direct Attach Copper Cabling Solutions

With the wide growth of network capacity and transmission speed in data centers, 40G QSFP+ direct attach copper cables are becoming more and more popular. Being compact, lightweight with low power, 40G QSFP+ direct attach copper cables are suited for 40G Ethernet, and other datacom and high-performance computing applications. Generally 40G QSFP+ direct attach copper cables can be divided into two types: 40G QSFP+ to 4 SFP+ direct attach breakout copper cables and 40G QSFP+ to QSFP+ direct attach copper cables. This post will firstly make an overview of 40G QSFP+ direct attach copper cables, then introduce two main types of 40G QSFP+ direct attach copper cables.

An Overview of 40G QSFP+ Direct Attach Copper Cables

The 40G QSFP+ direct attach copper cables are designed for a short distance and high density cabling interconnect system capable of delivering an aggregate data bandwidth of 40Gb/s. They are suitable for in-rack connections between QSFP+ ports of switches. These cables consist of cable assemblies that connect directly into two QSFP+ modules, one at each end of the cable. They use integrated duplex serial data links for bidirectional communication and are designed for data rates up to 40 Gbps. 40G QSFP+ direct attach copper cables are cost effective solutions for interconnecting high speed 40G switches with existing 10G equipment or 40G switches.

40G QSFP+ to 4 SFP+ Direct Attach Breakout Copper Cables

The 40G QSFP+ to 4 SFP+ copper direct-attach breakout cables connect a 40G QSFP+ port of a switch on one end to four 10G SFP+ ports of a switch on the other end. By using these cables, one may deploy switches that have 40G Ethernet ports while the servers still have 10G Ethernet ports. These cables use high-performance, integrated duplex serial data links for bidirectional communication. They comply with QSFP+ mechanical, optical, and electrical specifications (SFF-8436), and the SFP+ electrical (SFF-8431) and mechanical interface (SFF-8432) standards. Currently, these breakout cables come in lengths of 1, 3, and 5 meters and active cables in lengths of 7 and 10 meters. They are suitable for very short distances and offer a very cost-effective way to connect within racks and across adjacent racks.

40G QSFP+ to QSFP Direct Attach Copper Cables

The 40G QSFP+ to QSFP+ direct attach copper cables, such as QFX-QSFP-DAC-3M or QFX-QSFP-DAC-1M, connect a 40G QSFP port of a switch on one end and to another 40G QSFP port of a switch on the other end. Supporting similar applications to SFP+, these four-lane high speed interconnects were designed for high density applications at 10Gb/s transmission speeds per lane. Usually the QSFP+ to QSFP+ direct attach copper cable links are equivalent to 4 SFP+ cable links, providing greater density and reduced system cost. There are passive and active QSFP+ to QSFP+ direct attach copper cables. Active QSFP+ to QSFP+ direct attach copper cable assembly is capable of distances of up to 10 meters. While passive QSFP+ to QSFP+ direct attach copper cable assembly is suitable for shorter distances for 40G links. Designed for short length and high speed interconnects, 40G QSFP+ to QSFP+ direct attach copper cables offer a cost-effective alternative to fiber optic cable assemblies. They are also intended for short distance applications such as point-to-point in-rack and across rack network switch/server connections.

Conclusion

With the increasing deployment of 40 Gigabit Ethernet system, many fiber optic vendors worldwide deal with direct attach copper cables because of their low cost, low power consumption and high performances. 40G QSFP+ direct attach copper cabling solutions, either 40G QSFP+ to 4 SFP+ or QSFP+ to QSFP+ direct attach copper cables, help improve the availability of data center networks and support mission-critical applications.

Three Common Methods for Fiber Optic Cable Termination

Fiber optic cable termination is the addition of connectors to each optical fiber in a cable. There is a common misunderstanding that fiber optic cable termination is time-consuming and highly specialized. With the development of termination technology, fiber termination systems now require less training and produce high quality fiber connections in less time than it takes to terminate coaxial cables. Generally, there are three common fiber termination methods available to installers: pre-polished connector systems, epoxy and polish fiber termination and splice-on pigtail connectors. This article will make a brief introduction of these termination methods for your reference.

Pre-polished Connector Systems

Many installers choose pre-polished connector systems for their fiber optic terminations. Fiber optic termination kits for modern pre-polished connector systems enable installers who have never worked with optical fiber, to become proficient at terminating fiber optic cables in a short amount of time. These fiber termination systems are ideal for installers who need to add connectors quickly when installing fiber optic equipment. This method does not require adhesives and polishing for field termination. Instead it uses a factory terminated connector with a stub fiber in the ferrule and a mechanical splice to terminate the fiber. Termination only requires preparing the cable, cleaving the fiber, inserting it in the connector and fixing it with a special tool. Insertion losses for modern fiber termination systems are approximately 0.2 dB, or a maximum of 0.5 dB for systems using a precision cleaver. However, the manufacturing process makes each connector more expensive and the good kits with quality cleavers are more expensive than polish fiber termination.

Epoxy and Polish Fiber Termination

When installing a complete, structured wiring system, many fiber installers prefer the epoxy and polish method of fiber termination. This process is more involved and requires bonding of the connector to the end of the fiber using an epoxy or anaerobic process. Once cured, the connector end is polished to a fine, flat surface. This method provides the lowest loss, greatest reliability, highest yield and the lowest cost of any termination type. For single-mode fiber, it is virtually the only method of termination that can provide the precise end finish necessary for the low loss and minimal reflectance required for high speed networks. While termination of multimode connectors is much less critical, especially where reflectance is concerned. One drawback to this method is that these additional steps of curing and polishing can increase the time required for installations. The following picture shows the fiber optic polishing machine used for this method.

Splice-on Pigtail Connectors

Splice-on connectors are an alternative to either the pre-polished connector systems or the epoxy method of termination. Fiber pigtails are usually built as fiber optic cable jumpers, either single-mode or multimode fiber jumpers, and then cut in two. A factory-polished connector with a fiber optic jumper is spliced onto the existing fiber using a fusion splicer. A splice tray and enclosure are used to protect the spliced fibers. The splice-on pigtail connectors combine the quality of fusion splicing, enabling technicians to use their existing equipment. This method allows technicians to run drop cables to an end user, cut off exactly the length they need, attach the splice-on connector, and plug it in. The splice-on connectors also enable technicians to manage exactly the cable weight they require without any shorts or excesses. The main drawback of this method is the cost of the connectors and the fusion splicing equipment. Also, specialized skills are needed to operate fiber splicing equipment.

Conclusion

Since the late 1970s, various fiber optic cable termination methods have been brought to market. The goal for each new termination method is to have better performance and be easier, faster, and less expensive. The above three fiber termination methods all have their advantages and disadvantages. After having a better understanding of these termination methods, you can select your termination method more easily.

Five Steps to Consider When Designing A Fiber Optic Network

Designing fiber optic network is a specialized process for a successful installation and operation of a fiber optic network. It requires working with higher level network engineers usually from IT departments and cable plant designers as well as contractors involved with building the project. Actually, the fiber optic network design involves many complicated steps, such as determining the type of communication system, considering requirements, making actual component selection, testing, troubleshooting and network equipment installation and start-up, etc. Generally there are five basic steps to consider when designing a fiber optic network. The following article will introduce them one by one.

Step One: Select Optic Fibers

When deciding which type of optic fibers you need, you should take the range of the link into consideration. Most fiber optic products offer several versions that cover different ranges. Usually, short links use multimode fibers and LED sources, while long links use single-mode fibers and lasers. Alternately, if you already have fiber optic cable plant installed, select a product that will operate over your fiber optic cable plant, considering both fiber type and distance.

Step Two: Select Fiber Optic Cables

The working environment of the fiber optic cable plant affects the selection of fiber optic cables. Whether your application is in office environment, on factory floor, above ceiling or in the outdoor, the fiber optic cable must be appropriate for the application. For example, loose tube armored cables can provide superior performance in outside plant applications such as ducts, conduit and aerial lashed. So they are ideal for use in telecommunications, data trunk, and long haul networking. While tight buffered distribution cables are water-blocked, UL rated and ready for indoor/outdoor use. So they are recommended for applications such as campus backbones, inter building installations, data centers and ducts between buildings.

Step Three: Choose Fiber Optic Connectors 

As fiber optic cables need terminations to interface with other fiber optic equipment, connectors or patch cords compatible with the other fiber optic equipment will be needed. Actually, there are various types of fiber optic connectors and the connector type on both ends of a fiber optic patch cable can be the same or different, such as SC to SC fiber cable, or ST to LC patch cable, etc. Besides, fiber optic connectors have several termination methods, some using adhesives and polishing, some using splicing, which have tradeoffs in performance. Before making your choice, you’d better discuss connectors with both manufacturers and installers.

Step Four: Plan Ahead on Splicing Requirements

Generally, long lengths of cables may need to be spliced, as fiber optic cables are rarely made in lengths longer than several kilometers due to weight and pulling friction considerations. If fibers need splicing, you should determine how to splice the fibers, either fusion or mechanical, and what kind of hardware like splice closures are appropriate for the application.

Step Five: Calculate Link Loss

Once the basic design of the network is done, the next step is to do a “Link Loss Budget”. Loss budget analysis is the verification of a fiber optic system’s operating characteristics. This encompasses factors such as routing, circuit length, fiber type, number of connectors and splices, wavelengths of operation and communications optoelectronics specifications. You can compare the link loss to the link margin for the communications products you have chosen.

Conclusion

Fiber optic technology has revolutionized worldwide communications by increasing bandwidth and distance requirements in carrier and enterprise fiber optic networks. With the improvement of technology, the fiber optic network design continues to find a home in mobile backhaul, cloud services, data center, and other high-speed network applications. Proper design of fiber optic network will not only lead to highly reliable systems, but also save money. These five basic steps may guide you when you are designing your fiber optic system.

How to Tell Different Types of Connectors?

Fiber optic connectors terminate the ends of fiber optic cable jumpers, either single mode or multimode fiber jumpers, and enable quicker connection and disconnection than splicing. They adopt the mechanical optical means for cross connecting fibers and linking to fiber optic transmission equipment. Fiber optic connectors are the most widely used optical passive components in fiber optical transmission, optical distribution frame, optical test instruments and instrument panels. There are numerous types of fiber optic connectors available today. Generally, we can divide fiber optic connectors into various types according to different standards. This paper will introduce three methods for the classification of fiber connectors according to fiber core size, connector structure, and end face preparation.

Fiber Core Size

According to the fiber core size, fiber optic connectors can be divided into common silicon-based single-mode and multimode optical fiber connectors. As the name implies, the single-mode connector is connected with SM (single-mode) patch cable with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550 nm. While the multimode optical fiber connector is used for MM (multimode) cable which has a little bit bigger diameter, with common diameters in the 50 or 62.5 microns. Besides, some fiber optic connectors can be both single mode and multimode types. For example, LC connectors can be used with single-mode and multimode fiber-optic cables.

Connector Structure

Since 1980s, various manufacturers have developed a dozen types of fiber optic connectors. A fiber connector mainly includes a dust cap, connector housing, ferrule, crimp eyelet and boot bare buffer, etc. The mechanical design varies a lot among different connector types, thus we can get various connectors, such as FC, SC, ST, LC, MT, etc. For example, SC connector is built around a long cylindrical 2.5 mm diameter ferrule. A 124 to 127 µm diameter high precision hole is drilled in the center of the ferrule, where stripped bare fiber is inserted through and usually bonded by epoxy or adhesive. The end of the fiber is at the end of the ferrule, where it typically is polished smooth. While ST connector, simplex only, is twist-on mechanism. It is the most popular connector for multimode fiber optic LAN applications with a long 2.5 mm diameter ferrule. It mates with a interconnection adapter and is latched into place by twisting to engage a spring-loaded bayonet socket.

End Face Preparation

The connector end face preparation can determine what the connector return loss, known as back reflection, will be. Minimizing back reflection can provide high-speed and analog fiber optic links. In accordance with connector end face preparation, the connectors can be classified into PC polish, UPC/SPC polish, and APC polish connectors. PC polish connectors are typically polished with a slight curvature when the connectors are mated the fibers touch only at their cores. UPC polish types, improvement to the PC connectors, refer to the radius of the end face polishing administered to the ferrule, the precision tube used to hold a fiber in place for alignment. APC connectors have a curved end face which is angled at an industry-standard eight degrees. Only APC connectors can consistently achieve return losses of 60 dB. The following picture demonstrates their difference.

Conclusion

Fiber optic connector manufacturers offer various kinds of fiber optic connectors, including FC connectors, LC connectors, SC connectors, ST connectors, etc. Choosing the suitable fiber optic connector for any installation not only provides perfect performance for your job, but also saves time. Next time when you make a selection of fiber optic connectors, this article may give you a general idea of how to choose them.

Five Common Types of Fiber Optic Cables

Fiber optic cables refer to cables containing one or more optical fibers that are used to carry light. They are widely used in the Internet, telephone systems, cable TV, etc. There are various fiber optic cables based on different classification standards, such as single mode and multimode optical fiber cable according to fiber core size. And they can be terminated at both ends with the same or different fiber optic connectors to form fiber optic jumper cables, like LC to LC fiber cable, ST to LC patch cable. It is crucial to choose fiber optic cables carefully as the choice will affect the installation, termination and also the cost. This paper will introduce five commonly used fiber optic cables and their own special applications, including: tight buffer cables, loose tube cables, ribbon cables, armored cables and aerial cables.

Tight Buffer Cables

Generally, tight buffer cables are used indoors where cable flexibility and ease of termination are important to satisfy the diverse requirements existing in high performance fiber optic applications. In tight buffer cables, each buffer has one fiber to ensure excellent mechanical and environmental protection. Besides, there are no needs for gel filling, cleaning and stiff strength member for tight buffer cables. They are also easy to terminate with no breakout kits or splicing required. Simplex and zip cord, distribution cables and breakout cables all belong to tight buffer cables.

Loose Tube Cables

Loose tube cables are the most widely used cables for outside plant trunks because they offer the best protection for the fibers under high pulling tensions and can be easily protected from moisture with water-blocking gel or tapes. These cables are composed of several fibers together inside a small plastic tube. Unlike tight buffer cables, gel filling, cleaning and stiff strength member are all needed in loose tube cable constructions. In addition, loose tube cables are difficult to terminate and breakout kits and splicing are required.

Ribbon Cables

Ribbon cables are preferred where high fiber counts and small diameter cables are needed. These cables have the most fibers in the smallest cable, since all the fibers are laid out in rows in ribbons, typically of 12 fibers, and the ribbons are laid on top of each other. Ribbon cables deliver the highest fiber density in the most compact cable package possible. In addition, streamlining fiber termination used for ribbon cables can save time and money with easy mass-fusion splicing.

Armored Cables

Armored cables are deployed in direct buried outside plant applications where rugged cables are needed and/or rodent resistance. These cables withstand crush loads well. There are mainly two applications for armored cables. One is that they can be directly buried in areas where  rodents are a problem. Because they have metal armoring between two jackets to prevent rodent penetration. The other application of armored cables is in data centers, where cables are installed underfloor and one worries about the fiber cable being crushed. Because armored cables are conductive, they must be grounded properly.

Aerial Cables

Aerial cables are for outside installation on poles. They can be lashed to a messenger or another cable, common in CATV, or have metal or aramid strength members to make them self supporting. These cables have steel messengers for support. Like armored cables, they also must be grounded properly. OPGW (Optical Power Ground Wire), which is a high voltage distribution cable with fiber in the center, is one of the widely used aerial cables. In aerial cable constructions, fibers are free from being affected by the electrical fields. These cables are usually installed on the top of high voltage towers but brought to ground level for splicing or termination.

Conclusion

Actually, there are more complicated fiber optic cables types except the above five fiber cables because every manufacturer has its own specialties and sometimes their own names for common cable types. Various material combinations and layers are used to create cables that meet the demands of the customers' application on the casino floor, in the windmill, across the factory’s automation network, tethered to robots, or throughout the oil field.

Three High-Speed Copper Solutions

With the development of fiber optic technology, the copper wire technology shows some shortcomings, such as low bandwidth, short transmission distance, and poor durability and security, etc. While the combination of transceiver module and copper cabling can not only push the limits of copper, but also make it a good solution for short range applications. Typically there are three copper solutions for high performance network communications platforms: copper transceivers, loopbacks and DACs (direct attach cables).

Copper Transceivers

There are many optical transceivers that can achieve data transfer rates rivaling fiber-optic speeds while utilizing existing copper infrastructure and switch equipment, such as SFP (Small Form-factor Pluggable). 1000BASE-T copper SFP transceiver is based on the SFP Multi Source Agreement (MSA). It is compatible with the Gigabit Ethernet and 1000BASE-T standards as specified in IEEE 802.3z and 802.3ab. 1000BASE-T SFP transceiver can plug into standard SFP interface allowing for 1000Base-T Gigabit transmission over standard Category 5 twisted pair copper for links of up to 100 meters. This innovative copper SFP module solution provides a simple and cost-effective option for Gigabit Ethernet applications. The following picture shows a 1000Base-T SFP copper transceiver.

Loopbacks

Loopbacks can be used in both copper and optical ports. Generally, there are QSFP+, CXP, SFP, SFP+, and XFP copper loopbacks for testing and diagnostics with high speed networks and system protocols. They are specifically designed to support copper implementation of Fiber Channel and other serial data applications which require extremely high data transfer rates over long distances. They can provide up to 12 pairs of transmit data channels connected to the corresponding receive channels. Some loopbacks, such as QSFP+ form can offer a cost effective alternative to test with optical links.

Direct Attach Cables

DAC is a form of high-speed cable with transceivers on either end used to connect switches to routers or servers. Seeing from the material of the cable, DAC can be classified into direct attach copper cable and active optical cable (AOC). Direct attach copper cables can either be passive or active, while AOC cables are always active. Today’s direct attach copper cable can support higher data rates than traditional copper interfaces—from 10Gbps to 40Gbps and even 100Gbps per channel. Direct attach copper cable is designed to use the same port as an optical transceiver, but compared with optical transceivers, the connector modules attached to the cable leave out the expensive optical lasers and other electronic components, thus achieving significant cost savings and power savings in short reach applications.

Direct attach copper cables are commonly used in 10G and 40G networks. For 10G networks, SFP+ direct attach copper cable, or 10g copper SFP, with SFP+ connector modules permanently attached to each end of the cable, can transmit and receive 10Gbps data through one paired transmitters and receivers over a thin twinax cable. It provides high performance in 10 Gigabit Ethernet network applications. For 40G networks, QSFP+ to QSFP+ copper cables and QSFP+ to 4 x SFP+ copper cables are widely applied. These cables are compliant with SFF-8431 and SFF-8436 specifications. QSFP+ to 4 x SFP+ copper cables provide connectivity between devices using QSFP+ port on one end and multiple SFP+ ports on the other end. They can fill the expanding need for cost-effective data center interconnects.

Conclusion

Although fiber optic cables have many advantages than copper cables, such as low cost, great bandwidth, high speed and long reach, good reliability and perfect security, copper cables have their unique applications. Generally, copper solutions provide savings of 50% or more compared to optical alternatives for short-range requirements. They can also allow switch makers to utilize open architecture and give end users the choice between expandable copper or optical products. With the improvement of copper technology, copper can also be widely used as fiber optic cables.

Two Important Methods for Fiber Optic Splicing

Fiber optic splicing is an important method of joining two fiber optic cables together. It is a preferred solution when an available fiber optic cable is not sufficiently long for the required run. Besides, splicing is designed to restore fiber optic cables when they are accidentally broken. Nowadays, fiber optic splicing is widely deployed in telecommunications, LAN (Local Area Network) and networking projects. Typically, fiber optic splices can be undertaken in two ways: fusion splices and mechanical splices. This paper firstly illustrates the specific process of fusion splicing method and mechanical splicing method, then makes a comparison of the two methods for your reference.

Fusion Splicing Method

Fusion splicing is a permanent connection of two or more optical fibers by welding them together using an electronic arc. It is the most widely used method of splicing as it provides for the lowest loss, less reflectance, strongest and most reliable joint between two fibers. When adopting this method, fusion splicing machines are often used. Generally, there are four basic steps in fusion splicing process as illustrating in following one by one.

Step 1: strip the fiber

The splicing process begins with the preparation for both fibers ends to be fused. So you need to strip all protective coating, jackets, tubes, strength members and so on, just leaving the bare fiber showing. It is noted that the cables should be clean.

Step 2: cleave the fiber

A good fiber cleaver is crucial to a successful fusion splice. The cleaver merely nicks the fiber and then pulls or flexes it to cause a clean break rather than cut the fiber. The cleave end-face should be perfectly flat and perpendicular to the axis of the fiber for a proper splice.

Step 3: fuse the fiber

When fusing the fiber, there are two important steps: aligning and melting. Fist of all, aligning the ends of the fiber within the fiber optic splicer. Once proper alignment is achieved, utilizing an electrical arc to melt the fibers to permanently welding the two fiber ends together.

Step 4: protect the fiber

A typical fusion splice has a tensile strength between 0.5 and 1.5 lbs and it is not easy to break during normal handling. However, it still requires protection from excessive bending and pulling forces. By using heat shrink tubing, silicone gel and/or mechanical crimp protectors will keep the splice protected from outside elements and breakage.

Mechanical Splicing Method

If you want the splices to be made quickly and easily, the mechanical splice is a better choice. A mechanical splice is a junction of two or more optical fibers that are aligned and held in place by a self-contained assembly. A typical example of this method is the use of connectors to link fibers. This method is most popular for fast, temporary restoration or for splicing multimode fibers in a premises installation. Like fusion splice, there are also four basic steps in mechanical splice.

Step 1: strip the fiber

Fiber preparation here is practically the same as for fusion splicing. Just removing the protective coatings, jackets, tubes, strength members to show the bare fiber. Then ensuring the cleanliness of the fiber.

Step 2: cleave the fiber

The process is the same as the cleaving for fusion splicing. It is necessary to obtain a cut on the fiber which is exactly at right angles to the axis of the fiber.

Step 3: mechanically join the fiber

In this step, heating is not used as in fusion splice. Simply connecting the fiber ends together inside the mechanical splice unit. The index matching gel inside the mechanical splice apparatus will help couple the light from one fiber end to the other.

Step 4: protect the fiber

Once fibers are spliced, they will be placed in a splice tray which is then placed in a splice closure. Outside plant closures without use of heat shrink tubing will be carefully sealed to prevent moisture damage to the splices.

Which Method is Better?

Both fusion splicing and mechanical splicing method have their advantages and disadvantages. Whether choosing fusion splice or mechanical splice depends on the applications.

The fusion one provides a lower level of loss and a higher degree of permanence than mechanical splicing. However, this method requires the use of the expensive fusion splicing equipment. In view of this, fusion splice tends to be used for the long high data rate lines that are installed that are unlikely to be changed once installed.

The mechanical splicing is used for applications where splices need to be made very quickly and where the expensive equipment for fusion splices may not be available. Some mechanical fiber optic splice easily allows both connection and disconnection. In this way, a mechanical splice may be used in applications where the splice may be less permanent.

Conclusion

Fiber optic splicing is an essential method in the installation of fiber optic networks. Choosing the suitable method, whether fusion splice or mechanical splice relying on its applications, can not only saves money but also improves efficiency. When doing fiber splicing, it is necessary to following the specific instructions strictly for perfect splices. Besides, keeping all splicing tools clean is also very important.

This article originates from  http://www.fiber-optic-solutions.com/two-important-methods-for-fiber-optic-splicing.html.

An Overall Understanding of Fiber Optic Connectors

When installing a brand new fiber optic network, it is necessary to join two fibers together with low signal attenuation. Typically, there are two ways to link optical fibers: fusion splicing by using splicing machines and mechanical splicing by using of connectors. The fusion splice is a permanent connection which directly links two fibers by welding with an electric arc and aligning best possible both fiber cores. While by using connectors, you can connect two fibers more easily and quickly than splicing. Fiber optic connectors adopt the mechanical and optical means for cross connecting fibers and linking to fiber optic transmission equipment. They are the most widely used optical passive components in fiber optical transmission, optical distribution frame, optical test instruments and instrument panels. This paper will make a review of fiber optic connectors from the structure, advantages and common types.

Structure

Since 1980s, various manufacturers have developed a dozen types of fiber optic connectors. Although the mechanical design varies a lot among different connector types, the most common elements in a fiber connector are the same, such as dust cap, connector housing, ferrule, crimp eyelet and boot bare buffer, etc, as shown in following diagram. Among them, the ferrule, body and mating adapter are the most components in a fiber optic connector.

Ferrules are made of ceramic, metal, glass or plastic, among which ceramic ferrules or ceramic ferrules with metal inserts are most widely deployed. It is the most crucial element of the connector plug used for the precise alignment and centering of the optical fiber. Typical ferrule size is the 2.5 mm used in the SC, ST, and the FC plugs. The 1.25 mm ferrule is used in the small form factor LC plug. But in MTP and MPO connectors based on MT ferrule, it can allow quick and reliable connections for up to 96 fibers.

The body of the plug holds the ferrule, the coupling mechanism, and the boot. The coupling mechanism mates the plug with the mating adapter, allowing the connector to mate in only one position. At the end of the plug body is the boot which serves as a bend radius limiter for the cable entering the plug body.

The mating adapter is also an essential component in a fiber optic connector. It can hold the connector bodies and let them snap into place. For example, when mating two MTO connectors. the MPO connectors form a “plug and jack” style connector, where the plug is a no-pin connector and a jack is a pin connector with mating adapter. The adapter also aligns the MPO connector keys, which may be up or down in relation to the numbering of the fibers.

Advantages

Due to the demands of fast, efficient and safe performance in communication networks, more accurate and precise connections of the fiber ends are required. Fiber optic connectors just provide the right solution for complex systems. There are many advantages of fiber optic connectors. First of all, you can choose any types of connectors according to the application field of the system. Besides, the connection is removable that you can either connect and disconnect two fibers hundreds to thousands times without damaging the connectors.

Common Types

There are numerous types of fiber optic connectors available today. The most common are ST, SC, FC, MT-RJ and LC style connectors. Generally, there are three methods for the classification of fiber optic connectors according to transmission media, head structure, and end face preparation.

According to the transmission media, fiber optic connectors can be divided into common silicon-based single-mode and multimode optical fiber connectors. As the name implies, the single-mode connector is connected with SM (single-mode) patch cable, while the multimode optical fiber connector is used for MM (multimode) cable. Of course, they can have other options, for example, single-mode LC to ST fiber patch cable or multimode FC to SC fiber patch cable.

In addition, we can get various connectors based on head structure, such as FC, SC, ST, LC, MT, etc. ST, SC, FC fiber optic connectors are the standard form which are developed earlier than other connectors. They have different applications. ST connector is commonly used in wiring device, SC and MT for network equipment, FC for telecommunication network, etc.

In accordance with connector end face preparation, the connectors can be classified into PC polish, UPC/SPC polish, and APC polish connectors. The connector end face preparation can determine what the connector return loss, known as back reflection, will be. The back reflection is the ratio between the light propagating through the connector in the forward direction and the light reflected back into the light source by the connector surface. Minimizing back reflection can provide high-speed and analog fiber optic links. The following picture shows the difference between PC polish, UPC/SPC polish, and APC polish connectors.

Conclusion

It is not an easy task to select the right connector for different applications because there are so many choices available today. Choosing the suitable fiber optic connector for any installation not only provides perfect performs for your job, but also saves time. Next time when you make a selection of fiber optic connectors, this article may give you a general idea of how to choose them.

This article originates from http://www.cwdm-dwdm-oadm.com/blog/a/75/-An-Overall-Understanding-of-Fiber-Optic-Connectors.

Why We Choose Fiber Over Copper Cable?

When installing the network cable, which one do you prefer? Copper cable or fiber optic? Both of them have their advantages and unique characteristics. Copper has already existed in many places and it is cheap in network devices connection. While the fiber optic cable is more enticing cable infrastructure solution than its copper counterpart. However, with the dramatic reduction of cost of optical deployment, the fiber optic cable shows more advantages over copper and has a better prospect in the future market. This paper presents five reasons for the choice in fiber rather than copper cable from cost, bandwidth, transmission speed and distance, durability and security.

Cost

A few years ago, the overall price of fiber cables was 100% to 200% higher than coppers, but now the price between fiber and copper has little difference as the cost of fiber cable, components, and hardware has steadily decreased. Generally, electrical power transmission over copper is, and will likely remain, cheaper than laser power transmission over fiber. But most people overlook the cost of the wiring closet in copper networks. Per closet includes the costs of conditioned UPS (Uninterruptible Power Source) power, data ground, HAVC (Hybrid Automatic Voltage Control) and floor space. These costs generally exceed the extra cost of fiber equipment in a centralized fiber architecture. Besides, fiber usually has better performs, thus costing less to maintain. So, an all-fiber LAN (Local Area Network) is really more economic than copper for new construction and major renovations.

Bandwidth

The copper has very limited bandwidth, which is perfectly adequate for a voice signal. While fiber provides standardized performance up to 10 Gbps and beyond. Fiber links provide over 1000 times as much as copper and go more than 100 times further as well. A typical bandwidth-distance product for multimode fiber is 500 MHz/km, so a 500 m tether can transmit 1 GHz. While twisted pair optimized for high data rates (Cat 6) can transmit 500 MHz over only 100 meters over the same product. Besides, the signal losses over 500 m in fiber are negligible, but copper has very high losses at high frequencies.

Transmission Speed and Distance

Fiber optic versus copper transmission can be viewed as the speed of photons versus the speed of electrons. Photons travel at the speed of light, whereas electrons used in copper travels at less than one percent of the speed of light. Although fiber optic cables do not reach the speed of light, they are only about 31% slower. So you can see that there is a huge inherent speed difference between fiber and copper. In addition, fiber does not have the 100-meter distance limitation which belongs to the unshielded twisted pair copper without a booster. Therefore, distance can range from 550 meters for 10 Gbps multimode and up to 40 kilometers for single-mode cable.

Reliability

Fiber optic cable is much less susceptible to various environmental factors than copper cable. For example, copper will experience a great deal of degradation in quality over a distance of two kilometers, using fiber optic cable over the same distance can provide extremely reliable data transmission. What’s more, fiber is also immune to temperature fluctuations than copper and can be submerged in water. You can deploy fiber cable next to industrial equipment without worry.

Security

Since optical fiber does not transmit electricity, it does not radiate signals and cannot be tapped. While the copper using electricity is easy to be tapped, which will cause the entire system to fail. Besides, a broken or damaged optical fiber can be detected extremely quickly by monitoring either the actual power transmission or the transmission of a pilot signal. On the other hand, the copper carrying a current and could cause a fire concern if it is old or worn without such efficient monitoring.

Conclusion

The advent of optical cables, with their low cost, great bandwidth, high speed and long reach, good reliability and perfect security, has replaced coppers in all aspects of networking. Now fiber optic cable becomes one of the most popular mediums for both innovative cabling installations and upgrades, including backbone, horizontal, and even desktop applications. With the improvement of fiber optic connectivity, fiber construction will become more convenient.

This article originates from http://www.fiber-optical-networking.com/2016/05/17/why-we-choose-fiber-over-copper-cable/.

The Evolution of MMF

MMF (Multimode Fiber) is a type of optical fiber mostly used in LAN (Local Area Network) backbones and data centers due to its high transmission data rates and low operating costs. Typically, MMF supports the data rates and distance of 100Mbit/s for distance up to 2 km, 1 Gbit/s up to 1000 m, and 10 Gbit/s up to 550 m. MMF has evolved from OM1, OM2, OM3, OM4 to WBMMF (WideBand Multimode Fiber) since it entered into the market. With the improvement in transmission rates, MMF has been optimized from multi-megabit per second transmission utilizing LED (Light Emitting Diode) light sources to multi-gigabit transmission using LCSEL (Vertical Cavity Surface Emitting Laser) sources. Since the proposal of 100G-NG, 200G/400G and 1T Ethernet, traditional MMF becomes a bottleneck for the further development of Ethernet networks for its limits in fiber cores and transmission distance. However, WBMMF can overcome these limits by providing not only more efficient support for future applications to useful distances, but also complete compatibility with legacy applications. This paper will review the history of MMF to give a thorough understanding of WBMMF.

MMF

In the early 1980s, MMF with a light-carrying core diameter was first deployed in telecoms networks. It was a practical solution to the alignment challenges by enhancing the efficiently getting light into and out of the cabling. Later, SMF (Singlemode Fiber) began to be used in public networks, as alignments achieved micron accuracy and laser diodes became available. MMF was mainly deployed in Enterprise networks, supporting applications such as PBXs (Private Telephone Switches), data multiplexers and LANs because easier alignment was cheaper and low-cost LED sources were available.

OM1 and OM2

As Ethernet and fiber applications grew dramatically in LANs and SANs (Storage Area Networks), MMF became the primary media for backbone and other applications whose capabilities exceed copper twisted pair cabling. When data rates surpassed 100 Mb/s, 850nm VCSEL (Vertical Cavity Surface Emitting Laser) gave way to LED sources due to its high cost. This sparked a conversion of MMF core diameter from 62.5 µm (OM1 cabling) to 50 µm (OM2 cabling) because 50 µm design could provide higher bandwidth to better support transmission at hundreds of megabits per second.

OM3 and OM4

With the coming of the Gigabit era, the limitations with the bandwidth measurement techniques became clear in late 1990s. The old measurement made with overfilling launch conditions no longer provided reliable indication for the concentrated under-filling launches of VCSELs. Then the new measurement, known as LOMMF (Laser Optimized Multimode Fiber) came into being. The fist LOMMF, or OM3, provided a bandwidth of at least 2000 MHz km at 850 nm. In late 2000’s, OM4 appeared, offering at least a 4700 MHz km in anticipation of 25 Gb/s per lane applications. Today, OM3 and OM4 are the main fiber media deployed for Ethernet and Fiber Channel applications.

WBMMF

WBMMF is a new fiber under deployment to extend the capability and transmission distance of traditional OM4. With a 50 µm core and 125 µm cladding, WBMMF will be physically compatible with existing multimode fiber connectivity. It is designed for transmitting up to a range of wavelengths from 850 nm to 950 nm. This will be at least quadruple the current information carrying capacity of multimode fiber. Besides, WBMMF solution can also provide the most cost-effective platform to support higher speeds with fewer fibers at greater distances.

Conclusion

The emergence of WBMMF is a great revolution in the large data center. It breaks the bottleneck of traditional MMF which uses parallel transmission technology and has limited transmission rate. WBMMF can offer high-speed transmission rate with fewer fibers and lower cost because it uses the short wavelengths. Therefore, WBMMF will find widespread application in the coming large data centers in 100G, 400G and 1T connectivity.

This article originates from http://www.fiber-optical-networking.com/2016/05/14/the-evolution-of-mmf/.

A Smart Revolution of FTTH

FTTH (Fiber to the Home) is the most advanced technology for constructing the next generation of communication networks around the world. Until now, more than 200 million homes have deployed fiber connections. Many European countries, such as Lithuania, Norway, Denmark, Sweden and Latvia are approaching near universal access to fiber. Outside Europe, USA, China and Japan have been reaching more FTTH subscribers. In April of 2016, the FTTH Council Europe, an industry organization dedicated to accelerating the availability of fiber-based, ultra-high-speed access networks, has set its main objectives to support the wide adoption of FTTH in the further. It seems FTTH is not only about speed, but a revolution in optical networks. This article will present a review of FTTH to depict a smart revolution of FTTH applications.

What Is FTTH?

FTTH can be defined as the installation of optical fiber from the final connection to the individual premises to provide unprecedented high-speed Internet access. FTTH is very different from FTTB (Fiber to the Building). FTTB is an access network architecture using optical fiber to connect the subscriber’s building, but a physical medium to connect individual subscriber premises. While FTTH provides direct connection to individual premises, thus dramatically increases the connection speeds available to computer users. Recently, the improved procedures, innovative tools and components, and labor-saving methods greatly reduce the investment requirements of FTTH. Besides, the growing maturity of the industry and its supply chain also contribute lots. With reduction of deployment cost, it is promising that FTTH can expand the worldwide sooner.

Why We Need FTTH?

FTTH is the only type of fixed-line access network solution that is truly proofed against all future developments and eventualities. FTTH is unique because it removes all the bottlenecks that slow the performance of other types of network. It can offer higher speed, better reliability, greater bandwidth as well as lower operating costs.

Can you imagine that downloading large files in the time it takes you to make a bag of microwave popcorn? Well, the FTTH with a 1Gbps connection has made it possible. With FTTH, you can achieve at least 10 times faster on download speeds and 20 times faster on upload speeds than with ADSL networks.

In addition, the broadband over copper cables in cable television networks or telephone networks is very unreliable and it is difficult and time-consuming to solve the problem when a fault occurs. But fiber can overcome this problem. An all-fiber network can easily detect the fault and pinpoint the cause and even the location of the fault remotely without the need to dispatch a technician.

Besides, FTTH can also meet the increasing bandwidth requirements per household as more activities are carried out online. The four members in a connected family can watch video, play online games or just chatting to friends over the Internet by using different devices separately at the same time, such as a television, tablet, computer or smart phone. With the deployment of FTTH, the number of applications and devices that require machine connectivity is ever increasing.

In further construction, fiber costs about the same as copper. So why not consider FHHT with high speed, good reliability and great bandwidth? In addition, these superior qualities of FTTH result in lower operating costs without paying technicians on standby to fix problems.

Application of FTTH in the Future

The development of smart system has become essential for utilities and consumers to support load growth, new environmental standards and keep consumer costs at reasonable levels. FTTH is a key element to connect smart consumer devices to the local utilities smart network. With the deployment of FTTH, more smart applications can be found in health care, entertainment and cities.

Health Care

Have you ever imagined being able to access a personal trainer online? Or having medical consultation in your home? Or in-home monitoring without the need for nursing home care? All of these can be achieved in FTTH solutions. This idea can not only reduce health care costs, but also makes it easier for patients to access medical services. It is the best choice to distribute medicinal resources and share digital patient information.

Entertainment

In the new world of entertainment, you can watch anything you want on any screen at any time. Linear and broadcast television are being replaced by video-on-demand. Fiber access is vital for the future of television to accommodate the growing bandwidth demand generated by on-demand entertainment. Optical technology not only provides extremely high audio and video quality with an unlimited number of channels, it also offers interactivity and makes additional features possible. Multiple streams can be viewed and recorded simultaneously and video-on-demand is easily accessible.

Cities

Many European cities aspire to smartness by linking inhabitants and systems, transporting information seamlessly, reliably and instantly. FTTH solution is the right way to support smart cities with the reliability and the scalable capacity. In smart cities, real-time traffic information is sent to an ambulance driver; the location of underground gas mains to a construction foreman; remote access to lessons are helpful for a sick at-home ten-year-old child; the arrival time of the next bus is told; the location of the nearest taxi or nearest parking space can be guided, and etc.

Conclusion

Optical technology with unlimited speeds can empower the development of a flow of new services and content that enhances the quality of life, contributes to a better environment and increases competitiveness. We believe that FTTH, the only ac knowledgeable future-proof technology, is a revolution for a sustainable future when it comes to speed, reliability, bandwidth capacity and operating costs.

This article originates from http://www.cwdm-dwdm-oadm.com/blog/a/74/A-Smart-Revolution-of-FTTH.

400 Gigabit Ethernet Solution in the Future

Network carriers continue to face the bandwidth and capacity challenges in metro, regional and long-haul networks, as the traffic grows driven by more and more video streaming and proliferation of cloud computing, internet of things, data centers and mobile data delivery, etc. According to the prediction of IEEE (Institute of Electrical and Electronics Engineers), the wold's largest technician professional organization dedicated to advancing technology for the benefit of humanity, the network traffic would increase one hundred times by 2020. As the main carrier of network traffic, the optical transmission network has to expand its capacity and flexibility to meet customers' demands. Thus, 400 GbE solutions will be needed to support this increasing demands.

What Is 400 Gigabit Ethernet?

With the business needs for short and long term bandwidth requirements, the IEEE Industry Connections Higher Speed Ethernet Consensus group met in 2012 September and chose 400 GbE as the next generation goal. In March 2013, IEEE 802.3 formed 400 Gb/s Ethernet Study Group working on the 400 Gbit/s generation standard and later published its results on March 27th, 2014. Subsequently, the IEEE 802.3bs Task Force started working to provide physical layer specifications for several link distances, which are expected to be published in December 2017.

According to IEEE 802.3 Industry Connections Ethernet Bandwidth Assessment reports, the objectives of 400G solutions are as follows:

• Support full-duplex operation only
• Preserve the Ethernet frame format utilizing the Ethernet MAC
• Preserve minimum and maximum Frame Size of current Ethernet standard
• Provide appropriate support for OTN (Optical Transport Network)
• Specify optional EEE (Energy Efficient Ethernet) capability for 400Gb/s PHYs
• Support optional 400 Gb/s Attachment Unit Interfaces for chip-to-chip and chip-to-module applications

400G Implementation Options

At this time, 400G modulation has not yet been defined, but the industry has launched many options that enable much higher data rates and improved compensation for optical impairments. Among these modulation format options for 400G super-channels, three of them are commonly used: 100GPDM-QPSK, 200GPDM-16QAM, and 400GPDM-32QAM.

Currently, the widely deployed 100G long-haul optical systems are all based on PDM-QPSK (Polarization Division Multiplexed Quadrature Phase-Shift keying). This modulation is mature and widely used in 100G networks, which provides a good solution for 400G systems by combing four bands of 100G PDM-QPSK. 100GPDM-QPSK modulation is available with long distance application but it has low spectral efficiency and high power consumption.

QAM (Quadrature Amplitude Modulation) is one of higher-level implementation options. Typically, there are two ways to achieve 400G solutions with QAM. One of them is 200GPDM-16QAM that employs 2 sub-channels at 200 Gb/s each, with PDM-16QAM modulation at 32 Gbaud, and Nyquist channel spacing (32 GHz). This modulation can greatly increase spectral efficiency by 168% with higher system integration, lower volume and little power consumption. It is a perfect solution for short distance, but limited in remote distance.

The other is 400GPDM-32QAM using single carrier 400Gb/s system with baud rate of 61. This modulation can enhance spectral efficiency by 300% and has high system integration. It seems this solution with the highest spectral efficiency is the best scheme among the three modulations. However, the solution is not promising in long distance transmission because of its complex technology, high cost and shorter span.

Challenges of 400G

400G solutions are most probably the next phase in the 100G core era. This is encouraging because 400G transport may inherit some advantages from recent 100G efforts. However, we have to notice that there are huge uncertainties that remain in 400G marketing and product design strategies. These uncertainties are of three varieties.

The first uncertainty is associated with understanding how much the current enthusiasm over 400G transport trials can translate into actual deployment. That’s to say, the technology needs to be invented for a shift to a transport network infrastructure operating with 100G pipes can be reused to some extent at 400G.

Another is the relative absence of agreed standards for 400G public network transport. Although IEEE has made great efforts to do precisely this in its report, the issue of which application layer environment available with 400G solutions is more complicate in reality.

The final uncertainty turns out the most worrisome: how 400G transport platforms can respond to a rapidly evolving service environment. As the ability to create low-bandwidth voice traffic was always in the hands of millions of individuals, it is very difficult for 400G transport equipment to respond to the changeable service environment.

Conclusion

Although 100 Gigabit Ethernet is just at the beginning of widespread uptake, there is already plenty of talk in the market about the need for 400GbE in the enterprise. However, 400GbE is not yet mature and is still under the testing phrase in the laboratory and the network. How to improve the advanced spectral shaping and multiplexing technology? And can we break the limits of Shannon Theory to adapt the Flex-grid technology with a variety of spectral bandwidth? These problems are required to be solved to better service the 400 GbE solutions.  

This artilcel originates from http://www.fiber-optic-solutions.com/400-gigabit-ethernet-solution-in-the-future.html.

WDM Transponder

Globally increasing level of bandwidth and capacity requirements forces the optical communications industry to produce new products that are faster, more powerful, and more efficient. Particularly, WDM (Wavelength Division Multiplexing) transponders, known as OEO (optical-electronic-optical) converters, meet the demands for high capacity and fast transfer speeds for a longer distance. This article presents WDM transponder from two aspects: its 3R functions and advantages.

WDM Transponder 3R functions

WDM transponder is the element that sends and receives the optical signals over a single fiber. It performs an optical-electrical-optical operation. WDM transponders originally served to transmit wavelength of a client-layer signal into one of the DWDM system’s internal wavelengths in the 1550 nm band. However, they barely have the required frequency stability tolerances nor have the optical power necessary for the system’s EDFA (Erbium-doped Fiber Amplifier). In the mid-1990s, WDM transponders rapidly took on the additional function of signal regeneration. Signal regeneration in transponders quickly evolved through 1R to 2R to 3R and into overhead-monitoring multi-bitrate 3R regenerators. Now I will introduce 3R one by one.

1R

1R represents retransmission. The earliest transponders had little flexibility and are more like “garbage in garbage out”. Their output was nearly an analogue “copy” of the received optical received optical signal, nearly without signal cleanup occurring. Because the signal had to be handed off to a client-layer receiver (likely from a different vendor) before the signal deteriorated too far, the reach of early DWDM systems is limited. In addition, signal monitoring was basically confined to optical domain parameters such as received power.

2R

2R means re-time and re-transmit. Compared with 1R transponders, transponders of this type utilized a quasi-digital Schmitt-triggering method for signal clean-up before re-transmitting. Based on these analogue parameters, some rudimentary signal quality was done by such transmitters.

3R

3R is the combination of re-time, re-transmit and re-shape. 3R transponders can more closely monitor signal quality. Because many systems offer 2.5 Gbit/s transponders, the transponders are able to perform 3R regeneration to report signal health. Besides, full multi-rate 3R in both directions can be achieved.

Advantages of WDM Transponder

WDM transponders perform dual fiber to single fiber conversion and wavelength conversion within the WDM frequency domain to increase capacity. They provide an extended number of services for both CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) with numerous advantages.

Multiprotocol Support

WDM transponders are designed for most of the equipment operating directly with pluggable optics. They offer dedicated wavelength transport for a comprehensive mix of data, storage, TDM, video protocols including Ethernet, Fiber Channel and FICON (Fiber Connection), SONET (Synchronous Optical Networking), and SDH (Synchronous Digital Hierarchy). Thus, WDM transponders facilitate a wide variety of applications, such as broadcasters and cable operations, data networks, telecommunication room, and etc.

Performance Monitoring

WDM transponders provide efficient network monitoring and enhanced operations, because many performance metrics in of OAM (Administration and Maintenance) and SLAs (Service Level Agreements) are available.

Automatic Rate Detection

WDM transponders automatically detect incoming data rates so user provisioning is not required. In addition, they can supports 3R operation at all supported rates between 125 Mbps and 4.25 Gbps.

High Capacity and Low Cost

WDM transponders can not extend fiber optic links by hundreds of kilometers, but also provide high capacity. They are the cost-effective solution for a broad range of protocols.

Conclusion

From the above introduction of WDM transponders, you may gain a better understanding of their 3R functions and advantages. Besides, there are many other important devices in WDM systems, such as WDM filter, optical amplifier and dispersion compensation module and so on. All of them, including WDM transponders, are widely used in WDM networks.

This article originates from http://www.cwdm-dwdm-oadm.com/blog/a/73/WDM-Transponder.

Tutorial of OADM

OADM (Optical Add-Drop Multiplexer) is one of the intelligent techniques for the handling of communications signals. According to a new study from ElectroniCast, OADMs and their components are destined for continued market prosperity. In fact, The global consumption of OADM has been rising rapidly from 1998 until now. Then what makes OADM so popular? This paper will make a review of OADM to help you better understand it.

What Is OADM?

OADM is a critical device used in wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of a single mode fiber. It is the fundamental constructional block of optical telecommunications networks. OADM has passive and active mode depending on the wavelength. In passive OADM, the add and drop wavelengths are fixed beforehand. But in dynamic mode, OADM can be settable to any wavelength after instillation. OADM can be deployed for both expensive remote core networks and shorter distance networks, which are also called metro networks.

Structure of OADM

There are three stages in a traditional OADM: an optical demultiplexer, an optical multiplexer, and between them a method of reconfiguring the paths between the optical multiplexer and a set of ports for adding and dropping signals. The multiplexer is used to couple two or more wavelengths into the same fiber. Then the reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the optical multiplexer or to drop ports. The demultiplexer undoes what the multiplexer has done. It separates a multiplicity of wavelengths in a fiber and directs them to many fibers. The following diagram shows the working principle of OADM.

FOADM VS ROADM

Generally, OADM can be divided into two types: FOADM (Fixed Optical Add-Drop Multiplexer) and ROADM (Reconfigurable Optical Add-Drop Multiplexer).

• FOADM

The FOADM is a traditional wavelength arrangement scheme that can only input or output a single wavelength via the fixed port. FOADM is used to add or drop a certain set of wavelengths dedicated for specific DWDM channels. It allows the manufacturer to customize the number of channels, filter specifications, and power equalization but require excessive transporters at each node. Besides, in FOADM systems, manual adjustments are required because channels are added or dropped. And optical-to-electrical and electrical-to-optical alterations are also necessary. Normally FOADM is built with thin-film filters (TFFs) fiber bragg grating (FBG) and integrated planar arrayed waveguide gratings (AWG). The operational cost is high for FOADM because of the stationary nature of the arrangements and the requirement of manual changes.

• ROADM

The ROADM is a dynamic wavelength arrangement scheme, which allows for dynamic wavelength arrangement scheme. It uses a Wavelength Selective Switch (WSS). The WSS has an 8-dimensional cross-connect and provides quick service start-up, remote cross-connect and WDM mesh networking. The ROADM scheme also allows inputting or outputting a single wavelength or wavelength group via the fixed port. In ROADM systems, we don’t need to convert the optical signals to electrical signals and route those signals by using conventional electronic switches then convert back again to optical signals just like FOADM does. ROADM can configure as required without affecting traffic. It’s also used for remote configuration or reconfiguration via the NMS (Network Management System). This type of OADM is very flexible in rerouting optical streams, bypassing faulty connections, allowing minimal service disruption and the ability to adapt or upgrade the optical network to different WDM technologies.

Conclusion

OADM is an essential element compatible with both LAN (Local Area Network) and long haul networks. It enables carriers to exploit fiber bandwidth, improve network reliability and reduce the cost of providing broadband services. With the development of the metropolitan network, demand for cheap devices is the primary motivation. And OADM is a potential candidate for providing such cheap devices. The OADM market will grow steadily, propelled by large numbers of OADMs deployed in WDM systems.

This article originates from http://www.fiber-optic-solutions.com/tutorial-of-oadm.html.