Other 10GigE Transceiver Markets – ER, LX4 and LRM

Some of you may have noticed that in my last post I neglected to talk about three other 10-Gigabit Ethernet variants – LX4, LRM and ER. That’s because the content was already long enough and I wanted to focus on the volume data center applications. Now, I’ll discuss the others.

10GBASE-ER runs over SMF at 1550nm for up to 40km. While there are a few service providers that might choose to do this, the vast majority of them choose WDM through the OTN instead. There may be some private networks that have need for this variant as well which is what prompted the IEEE include it in the standard. These transceivers are priced out of typical budgets for the average enterprise at over $4000.

10GBASE-LX4 was originally introduced to address installed base of FDDI-grade (not laser-optimized) MMF, but can also be used with higher-grades of LOMF as well as SMF. It uses CWDM to send four wavelengths (thus the X4) between 1269.0 to 1355.9nm running at data rates of 2.5 Gbps each. LX4 modules are available in both X2 and XENPAK form factors and from at least a couple of sources such as Emcore and Hitachi Cable. As you can imagine, because these devices have four lasers and four detectors with their associated electronics, they cost appreciably more than either the SR or LR transceivers. The module alone retails for about $2000, which means that the per port cost would probably around $2500. But, you most likely wouldn’t fill your switch with these modules of course; you would only use them as needed where you wanted to re-use existing installed fiber.

In response to the high priced LX4, 10GBASE-LRM variant was developed. It was enabled by chip companies such as Clariphy and Scintera with some new technology, electronic dispersion compensation (EDC), that could push 10G serial to longer distances on MMF. It took a while to develop the standard and the consequence was that LX4 really took much of the market it was intended for. However, once products were released and supported by the top-tier transceiver manufacturers (Avago, Finisar, Opnext), it has really taken much of the business away from LX4. LRM modules are now available in SFP+ packages as well, which clearly indicates the vendors think there will be an ongoing market for them.

One note of caution – if you intend to use either the LX4 or the LRM modules, you need to make sure that both ends of your channel have them, otherwise it won’t work.