Fiber optic link for digital audio interface

摘要

A description is given of a fiber optic link for digital audio interfaces that is able to transmit 3 Mb/s biphase signals up to 10 m with the pulse-width distortion at less than +or-25 ns. The fiber optic transmitting module consists of a GaAlAs light-emitting diode emitting at 660 nm wavelength, and a transmitting IC. These chips are mounted on a lead frame and molded by a clear resin. This molded unit is assembled into a receptacle that has a self-tapping hole for easy attachment to the rear panel of audio equipment. It also has preformed pins for presetting to the printed circuit board before soldering. The fiber-optic receiving module consists of a Si-p-i-n photodiode, and a receiving IC, and is assembled with these chips in the same way as the transmitting module. The conductive receptable electromagnetically shields the receiving module, but a nonconductive spacer attached to the receptacle electrically isolates it from rear panel. The link is intended for use in compact disk (CD) players, digital audio tape (DAT) recorders, video cassette recorders (VCRs), and digital receivers.