As optical networking vendors announce fifth-generation coherent DSP chips, supporting higher capacity wavelengths, some confusion has developed over the actual performance of 800G wavelengths in real-world WDM networks, as opposed to highly controlled and optimized field trials or lab experiments. Over standard single-mode fiber, carriers should expect 100 – 220 km optical reach in most WDM applications. While that’s significantly less than some of the industry grabbing 800G headlines, the differences are easily explained through a short review of the factors affecting optical reach performance.
The new fifth-generation coherent DSPs represent significant technical achievements and push wavelength capacities close to the Shannon theoretical limits. However, the real benefit may be less about 800G wavelengths and more about enabling 400G to 600G wavelengths over regional to subsea distances.