Fiber optic transceivers are transmitter/receiver modules that are pre-packaged in a standardized form. They offer convenience and the low cost of mass production, are widely used in backbone networks and access networks to support Internet services and enterprise applications that require broadband transmission.
In the fiber optic field, ITU-T is mainly responsible for procedures and IEC is mainly responsible for products. Although these organizations cooperate, they remain separate and were established with different objectives, so some products and procedures, such as optical fibers, must be specified in each organization. Therefore, the two organizations cooperate to avoid producing conflicting specifications.
A standardized fiber optic transceiver is adapted to provide an optimal PCIe expansion over a fiber optic medium. Signal buffers are utilized to translate and fine-tune standardized PCIe traffic to a level of low voltage differential signaling (LVDS) that is comprehensible to a wide range of fiber optic transceivers over a wide range of interface bandwidths. The intended use for such a high-speed LVDS buffer is to strengthen and enable PCIe signals over metal (copper) cable or metal printed circuit board (PCB) traces for large PCBs, such as backplanes, server motherboards, etc. By disposing the PCIe buffer used for metal (copper) cable between the PCIe bus and the fiber optic transceiver, one can achieve the signal conditioning and translating required to allow PCIe signals to pass over the fiber optic medium.
The SFP transceiver is not standardized by any official standards body, but rather is specified by a multi-source agreement (MSA) between competing manufacturers. The SFP was designed after the GBIC interface, and allows greater port density (number of transceivers per cm along the edge of a mother board) than the GBIC, which is why SFP is also known as mini-GBIC. The related Small Form Factor transceiver is similar in size to the SFP, but is soldered to the host board as a through-hole device, rather than plugged into an edge-card socket. However, as a practical matter, some networking equipment manufacturers engage in vendor lock-in practices whereby they deliberately break compatibility with “generic” SFPs by adding a check in the device’s firmware that will only enable the vendor’s own modules.
Fiber Optic Transceiver design issues nowadays include the following:
Mechanical compatibility of connector interfaces;
Cross-talk between transmitter and receiver electronics;
Electronic noise (EMI) issues, both with respect to emissions and susceptibility;
Ease of manufacture (i.e. manufacturability);
With the potential for providing high-speed and broadband characteristics, research and development of technologies related to fiber optic transceivers started. As a result of these demands and applications that require high-speed data transmission, new issues have arisen related to delay in the electrical connection network and physical wiring space in and between equipment. In order to deal with these issues, standardization activities for optical circuit boards and sc/apc fiber connectors for circuit board attachment have started in TC91 (Electronic assembly technology).
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