Using optical filter for ethernet

Just saw a demonstration that claimed that introducing an ethernet-optical-ethernet filter would filter out lots of radio frequency interference that comes from the web, your modem, and your ethernet devices like a NAS where you store your music. Basically a pair of optical ethernet converters back to back. Cost under $100. The demo at last year's Denver Audio Fest claimed it makes a sound quality difference. Call it an optical filter. I think its ListenUp who gave the demo. As an example they suggest you put this filter between your streamer and your NAS. Bacically any components connected via ethernet cable evan within your network, not just to the outside world. Any thoughts or experience?