Satisfied after processing

The device is built very solid - but may require rework.
The design principle of the switch is ideal for audio amplifier with only one optical input on which you want to connect to multiple sources without having to swap each optical cable.
Data transmission was unfortunately at first only for a device (Samsung TV) properly. The sound from the Media Receiver ENTERTAIN showed dropouts, the sound from the HDMI Ligawo decoder never came through.
I could not tell me that the 10cm additional optical cable in the switch would bring much additional attenuation to cause this deterioration. Especially with long or extended optical cables everything worked.

The works shown below are recommended only for precision engineering savvy professionals (hobbyist?).
I decided to disassemble the switch - which due to its solid construction was fortunately not a problem.
I found that the surfaces (faces) of the optical fiber were very uneven. I decided to grind these areas plan. I used to grit sandpaper 1200 (in paintshops usual). In addition, I polished with "Paris Red" after (maybe not necessary).
After assembling all switch positions functioned smoothly.
The manufacturer I can only recommend to plan and polishing of the optical fiber in the production process with take. For lay people the unit (transmit and receive performance of opto-components depend) not to be used under certain circumstances as.