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.