On 10/19/23 22:24, Chad Lamb via NANOG wrote:
XKL is still here ... Some caveats on 400G ZR/ZR+ devices: - They are power hungry, cooling is a challenge. 800G even more so. The OSFP package for 800G looks like the better choice than QSFP-DD for this reason. We'll see, we need more mileage on this. - For the ZR devices, not all vendors are equal. Some support 4x100GE as well as 400GE, if that matters to you. Some have integrated BERT and encryption, some do not. - Do not plan on inter-operating different vendors of ZR+ devices. They will interoperate only in ZR mode. - Plenty of filter options out there if you are putting the ZR/ZR+ in your router. I'll throw a plug in for the Coherent free space DWDM filter. Free space technology has the best IL and isolation numbers. Coherent hasn't packaged it in a module for easy racking yet (XKL can provide that). So if you aren't adding an EDFA, the lowest IL you can get helps your reach. - If you have at least a few 400G channels, add an EDFA and use the Tx = -10dBm devices, rather than the Tx = 0dBm devices. This is cost effective. The EDFA also extends the reach considerably. You can launch each channel up to +10dBm or more, for a modest number of channels, without getting in trouble with fiber non-linearities (four-wave mixing).
Many thanks, Chad. Glad to hear XKL are still in business, and doing well :-). Mark.