Google seeking to study the Coherent-Lite method for "800G-LR" with a reach distance of 10 km

How do you realize the standard standard of 10km at 800g?

Continuing from the last time, the story of the July 2021 meeting.The period, which can be freely proposed, is approaching the end, and even though it is not a hurry, various detailed proposals have become noticeable.

First of all, Google's Cedric F."Coherent-lite for beyond 400GBE" by LAM, Xiang Zhou and Hong Liu.He pointed out that the specification of 800g is 10 km, but has not yet been considered how to achieve that 10km.

Google has pointed out that the traffic on the company's campus has expanded 10 times in the last four years, and the network distance in the campus has expanded to 10 km.In short, we want to set a standard standard that can reach 10km for 800g to use it in -house.

Now, it is already known that 10km is difficult with CWDM4.Chromatic Dispersion Limit, if you dare to translate it into Japanese, it will be a color distributed limit, but in the case of CWDM, the wavelength of the four lights used expands considerably.The 800g PlugGable MSA plan to achieve 500m FR4 with CWDM4 is "1 with PSM4 and CWDM4..It is introduced in "800g PlugGable MSA", which extends the reach while realizing 6TB/SEC.

However, the "CWDM4 MSA" introduced in "25Gbps x 4 is integrated into one SMF 1 piece, and 100Gbps is realized, and" CWDM4 MSA "with a reach distance of 2 km and" 4WDM MSA "on 10/20/40km.CWDM4 is composed of 1271/1291/1311/1331nm and 4 wavelengths in 20nm increments.

With this CWDM4 MSA, it is 25Gbps per wavelength, and the reach is still 2 km.For long distances on 10/20/40km, "4WDM MSA" is responsible for long distances, but this is only 10km diverted CWDM4, but 20/40km uses DWDM.

As described in "100G 4WDM-10/20/40", which aims for the reach of 10/20/40km in 100Gbps, the wavelength is 1295..56-1309.14nm and 4.The chopped width is reduced to around 5nm, and this suppresses the variation in characteristics due to the difference in wavelength.

A similar story naturally occurs here, and if it is 100g, you may be able to go to nearly 5km, but if it is 200g, it will be around 1km, and it will be a dream again.

If the charp control is properly performed, the reach will increase, but this time the signal loss will be too large, so the receiving side will be difficult.In short, CWDM4 is about giving up.So DWDM?That is not the case, Google has proposed "Coherent-Lite".