[Moved]: Do we have termination for optical interconnects?

I have a basic question regarding optical interconnects. Like electrical serial links, do we need to have termination resistors like 50 ohms for optical interconnects assuming that the electrical-optical conversion (and vice-versa) blocks are placed near the chip without any long electrical links?

Re: Do we have termination for optical interconnects?

Yes, optical fiber connectors have their own designations for return loss, the (inverse) optical correspondent to electrical reflection, resp. adaption (e.g. by a 50Ω resistor in a 50Ω transmission line)

High return loss means low amounts of reflection at the interface

Click to expand...

... see here.

However grade 1 return loss means the best adaption, grade 5 the worst (IEC standard 61753-1), and these designations apply to the connection quality between the optical glass (or plastic) fiber glued to the semiconductor photodiode's surface, i.e. the quality of an optical adaption of the refraction indices between fiber, glue and semiconductor surface, avoiding an air gap in between. These refraction indices essentially determine the return loss, i.e. the adaption quality corresponding to an electrical termination "quality".

There's no such thing as an "optical 50Ω adaption resistor" of course. However you could perhaps construct such an element from the refraction indices respectively from the insertion loss and return loss values of the fiber.