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.