External USB audio card with optical S/PDIF POF interface

The purpose of the project was to create an external USB audio card, which could be able to:
1) serve as usual external USB audio card with headphone/line output and audio line input
2) can transmit the digital audio data at relatively long distance (20m -100m)
3) can receive and process the digital audio data send by the similar card and either transfer it through the USB to the PC, or convert it to analog audio signal
As long distance transfer media was chosen the POF.
A short explanation of the POF technology will be presented:

What is POF?
POF stands for plastic optical fiber with the term plastic being used a vulgarization for polymer materials.
The 1mm fiber diameter is about 500 times thicker than a glass optical fiber. 96% of the cores cross section conducts modulated light for data transmission similar to glass optical fiber applications. The maximal transmission distance amounts to about 100m without active repeaters. Polymer fibers are used for high speed data network in homes, commerce and industry as well as in cars and airplanes. POF is often regarded as an optical home network because POF is easy to install. The fiber is thin, can be shortened to the desired length by a sharp knife and requires no connectors on its ends. Anyone can set up a robust, high performance and Ethernet compatible network without any special tools.
 
For more detail: External USB audio card with optical S/PDIF POF interface