SR multi-mode optics
Author:Utoptical Date: 10/18/2018
SR multi-mode optics
Numerous data centers possess structured cabling on which the fiber infrastructure is installed in pipes and under floors, being integrated into optical patch panels that are used to reconfigure the fiber's operational endpoints by hands. Occasionally, fibers run into other system, rooms, floors, or even other buildings, requiring the ability to disconnect the fiber from the transceivers installed in the system. This is not possible with DAC and AOC integrated cables because the wires or fibers are integrated at the plug or transceiver end. This article will focus on Short Reach (SR) multi-mode optics.
SR stands for Short Reach, SR transceivers are almost always multi-mode and optimized for high speeds over relatively short distances.Short reach optics are not new and have a long history of different fibers, connectors and transceiver types at different data rates ,modern data centers use SFP/LC and QSFP/MPO form-factors. SR transceivers usually applied over OM3 and OM4 cablings to give a more structured optical cabling used in large buildings. And the transmission distance respectively are 300m and 400m.
10GBase-SR is the original multimode optical specification and is still the most commonly used. SR transceivers use large core diameter, 50 micron fiber, which can be easily connected to lasers and detectors, so the cost is much lower than with 9 Single mode optics for micron core diameter fibers. However, SR laser pulses tend to spread into multiple transmissions in large diameter fibers and become unavailable after about 100 m, so the IEEE standard body sets the limit to 100 m, assuming four connectors in operation. Multimodes can reach up to 400 meters, but require specialized lasers, fiber optics and connectors.
Multimode optics use a laser called VCSEL (Vertical Cavity Surface Emitting Laser). The lasers are produced in the vertical cavity of a semiconductor wafer and are emitted perpendicular to the surface of the chip. Multimode optics use an 850 nm wavelength infrared laser located in the optically transparent window of the fiberglass.
SR Transceiver features:
● Support Multi Rate 4.9152 Gbps to 10.3125 Gbps
● SFI electrical interface
● 2-wire interface for integrated Digital Diagnostic monitoring
● Hot pluggable
● Very low EMI and excellent ESD protection
● +3.3V power supply
● Power consumption less than 1.0W
SR Transceiver Application:
● 10G Ethernet
● 10X Fiber Channel
SR multimode optics is the lowest-priced optical interconnect on the market, using optical connectors to separate the transceiver from the fiber. Although both support a range of 100 meters, AOC is much cheaper than SR optics, but the former is used as a complete cable and the transceiver side cannot be separated from the fiber. Multimode fibers have large optically-carrying fiber cores that are easier and less expensive to manufacture than single-mode optics, while single-mode optics have tiny fiber cores that are difficult and expensive to construct. For these reasons, multimode short-range optics are very popular in modern ultra-large-scale, enterprise and storage data center applications.
Utoptical offers short reach multi-mode optics in 10Gb/s and 25Gb/s line rates single as well as four-channel configurations enabling 10Gb/s to 100Gb/s of link bandwidth. These are available in SFP and QSFP connector form-factors that use LC optical connectors and MPO optical connectors respectively.
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