A transceiver is a combination of a transmitter and a receiver in a single device where they function independently for bidirectional communication. Furthermore, transceiver modules are hot-swappable I/O (input/output) devices which plug into module sockets. The transceiver acts to connect the electrical circuitry of the module with the optical or copper network. There are multiple types of transceivers available on the market, which makes people feel confused about how to choose the right one for their own device. In today’s article, we describe different aspects of transceivers that need to be known before purchasing a transceiver module. I hope it will be a good reference source for the new telecom technicians.

The form-factor specified by MSAs, is needed so that the transceiver can mechanically and electrically fit into a given switch, router etc. Transceiver MSAs define mechanical form factors including electric interface as well as power consumption and cable connector types. There are various MSA types: SFP, SFP+, XFP, CFP, CFP2, CFP4, QSFP and so on.

Always remember to protect the module by inserting clean dust covers into them after the cables are removed because getting dust and any contaminants into the module will greatly affect the normal operation. In addition, please be aware that the regular removal and installation a SFP transceiver can shorten its useful life. For this reason transceivers should not be removed or inserted more often than is required.

Last but not least, transceiver modules are sensitive to static, so always ensure that you use an ESD wrist strap or comparable grounding device during both installation and removal.

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We are quite familiar with difference between single-mode fiber (SMF) and multi-mode fiber (MMF), but we know little about single-mode and multi-mode transceiver. So what are they? And how to choose between them. Actually single-mode and multi-mode fiber are the transport media of a transceiver module. Besides this, here are certain things you need to know before making that decision which can prevent additional costs in the future.

The key differences between single-mode and multi-mode transceiver lie in the following expects—distance and cost, speed, how they work and compatibility issue. The following text will explain them one by one.

The cost difference between single-mode and multi-mode transceiver mainly arises from the cost difference between single-mode fiber and multi-mode fiber. It is known that the optic for single-mode is nearly twice the cost of multi-mode fiber. But the cost of a single-mode transceiver is negligible when installed as part of a project. Therefore, multi-mode transceivers are typically used when the distance involved is not long.

In contrast, multi-mode fiber has a much bigger core and uses a longer wavelength of light, resulting in MMF having higher numerical apertures which means they are better at collecting light than single-mode fibers. In fact, this refers to the optics is cheaper. Due to the modal dispersion in the fiber, multi-mode fiber has higher pulse spreading rates than single mode fiber, limiting multi-mode fiber’s information transmission capacity. Thus multi-mode transceiver can only support shorter distance.Figure 2 shows a compatible CiscoGLC-SX-MMDand a multi-mode patch cable.

We all knew that single-mode fiber and multi-mode fiber are not compatible. The main reason is that they possess distinct wavelength of the laser and core size of the fiber. Take Cisco SFP as an example, there is a type of SFP transceiver module (GLC-LX-SM-RGD) which can support both single-mode and multi-mode fiber. But amode conditioning patch cableis always required when using single-mode transceiver (likeGLC-ZX-SMD) with 62.5-micron MMF, and only at distances that would have worked using multi-mode transceivers. It does not work when we are exceeding the distance specified for multi-mode fiber. The result could be an elevated bit error rate.

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Figuring out X2 transceivers is not as difficult as it seems, but it requires knowing all of the facts first. It is known that X2 transceiver is a hot swappable products designed for 10Gbps fiber optic transceiver applications. But in order to have a better understanding of the X2 transceiver module, some detailed information about X2 transceiver will be provided in this article.

X2 transceiver is a hot pluggable in the Z-direction module that is workable in typical router line card applications, Storage, IP network and LAN and compliant to XENPAK MSA. XENPAK transceiver is a fully integrated 10.3Gbqs optical transceiver module that is made up of 10.3Gbqs optical transmitter and receiver, XAUI interface, Mux and Demux with time and data recovery(CDR).

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When talking about fiber optic transceivers, we may encounter a term — MSA (Multi-Source Agreement). But what is MSA? It seems likes an universal organization that defines all the fiber optic transceivers and many other telecom products. However, this understanding of MSA only stays at the surface. In this passage, a clearer introduction to MSAs and why they are so important to fiber optic transceiver vendors will be presented. Just read the following text and you will gain somethings from it.

MSAs strictly define the operating characteristics of these optical transceivers so that system vendors may implement ports in their devices that allow MSA compliant transceivers produced by name brand, as well as third party vendors, to function properly. That is, transceivers may be purchased from any of the multiple sources in the open market, like Fiberstore. This gives end users more choice when selecting module vendors, which serve to drive down cost through economies of scale.

The most common scheme is to write a unique code into some of the undefined memory in the EEPROM of each fiber optic transceivers. When the transceiver is inserted into the host switch, its EEPROM is read, and, if the code is "incorrect” the module is rejected as "incompatible”. Though the unique code seems like a barrier for the 3rd party transceiver suppliers, many module vendors have determined how to generate and program certain parts with proper codes. Because of this, they are not distinguishable from the brand name parts of the host systems. System vendors will use the tactics to protect consumers from grossly inflated prices. They also introduce standards to support and encourage creation and standards.

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There are two standards for single mode patch cable — OS1 and OS2. The dissimilarity between them is largely a matter of cable construction rather than fiber optic performance. Customers must find their way to see how these cables will improve the functionality of the device. Here is some information related to the differences between the cable construction.

Category OS1 is designed for internal situation where the maximum distance is 2000 meters. This cable type will allow speeds of over one to 10 gigabit Ethernet. However, category OS2 cable is designed for all users where a maximum distance of 5,000 to 10,000 meters, which will also allow a distance of one to 10 gigabit Ethernet. 

OS1 has a greater loss per kilometer than the OS2 outdoor fiber. In general, there is a 1.0 db/km for OS1 compared to 0.4 db/km for outdoor cables. Cables are cheaper with higher loss levels. That’s why many designers prefer OS1 fiber. Slight interoperabilty will be experienced if either the OS1 SM fiber cable or OS2 SM fiber cable is created by splicing or patching. Replacement may be a better option if you decide to incorporate either of these standard fiber optic cable options into your design. 

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