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While 100GBASE-LR4 muxes four channels into different wavelengths between ~1295 to ~1310nm, 100GBASE-CWDM4 uses between ~1271nm and ~1331nm. CWDM stands for coarse wavelength division multiplexing. We are actually showing 100GBASE-CWDM4 modules instead of LR4 modules since those are what we expect most of our readers will use more of. The LR4 is rated for 10km on single-mode OS2 fiber. In terms of distance, the SR4 is usually rated for 100m on OM4 multi-mode fiber and 70m on OM3 multi-mode fiber. As such, one only needs two fibers (usually via a LC duplex cable) to run 100GBASE-LR4 versus eight for 100GBASE-SR4. With 100GASE-LR4, each single strand of fiber carries four signals slightly offset from the 1310nm wavelength to avoid interference (SR4 uses 850nm.) Each of the four transmit sides are muxed to go over one fiber simultaneously while they are then demuxed at the other end to be received. We are going to quickly note here that there is something called 100GBASE-SR10 that uses MTP-24 using 10 fibers for transmit and 10 fibers for receive with four remaining dark. MTP 12 Close 800įour are used for transmit and four are used for receive while the remaining four remain dark. Commonly MPO/ MTP-12 cable is used that has twelve fibers. As such, a connection requires eight fibers to transmit 100Gbps speeds. In SR optics, these are kept as distinct pairs. These four pairs of transmit and receive go over fiber using two different methods. This is also why we can break out a 100GBASE-SR4 connection into four 25Gbps connections with SFP28 transceivers on the other end. The same is for the 25Gbps modules found in many 25GbE installations that have one 28Gbps electrical interface and are thus SFP28 modules. A -SR4/ -LR4 module has four electrical interfaces and each runs at 28Gbps. With a 100Gbps optical interface, the 4 means that we need four pairs of transmit and receive, each providing roughly 25Gbps. While the data rate may seem self-explanatory, some of the other parts may not. 4 – This means that we are using four transmit/ receive pairs.LR/SR – The quick way to think about these is to remember SR is short for short-range while LR is short for long-range.100GBASE – In this part, we can look at the 100G and remember 100Gbps.We are going to focus on the 100Gbps QSFP28 option here, but this also applies to the 40Gbps 40GBASE-SR4 and 40GBASE-LR QSFP+ optics. Differences Behind 100GBASE-SR4 and 100GBASE-LR4 Opticsīoth the 100GBASE-SR4 and 100GBASE-LR4 are 100Gbps / 100GbE/ Infiniband optics and how they operate is in some ways similar, but also quite different in an important aspect. This is a quick guide to answer that question. One of the key questions those getting into optics may ask is what is the difference between a 100GBASE-SR4 and 100GBASE-LR4 optic. As part of our fiber guide series, we need to start talking not just about cables, but also optics.
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