So my personal story: I was somehow unable to use the optical in of my audio interface for SPDIF audio from a synthesizer module.
But I DID have a coaxial SPDIF audio input that could be used.
It was recommended to me to look for a simple coax/spdif switch box and this one so far has worked out almost perfectly.
Not much I can say other than: it works, it works well and without issues if you're in a similar situation to myself.
There's a switch to switch between input sources: coax or Toslink, and the output can also be switched freely.
The power supply you get with this has a modular plug that allows you to attach many regional types of connectors, which are also included.
US, UK, Europe and such.
I haven't noticed any stuttering or jitter while using optical SPDIF through this box, and being able to change between two synths for both coaxial and optical SPDIF at the flick of a switch is a massive boon for clean audio recording and a smooth workflow.
Great stuff, would recommend for anyone with a small home studio.