An Optical Repeater with High-Impedance Input Amplifier

An Optical Repeater With HighImpedance Input Amplifier By J. E. GOELL (Manuscript received September 14, 1973) A 6.3-Mb/s repeater for fiber optic communication systems is described which incorporates a high-impedance input amplifier. It is shown that by utilizing an input circuit with a time constant which is long compared to the bit interval and equalizing after the signal has been sufficiently amplified to set the signal-to-noise ratio, thermal noise can be decreased. As a result, a reduction can be realized in the required signal and, with an avalanche detector, in the optimum gain. The repeater, which was realized in a compact form employing standard integrated circuits, utilizes a GaAs light-emitting diode as its optical source. Other features include automatic gain and threshold controls and recovered timing.