Optical heterodyne receiver with a six-port fibre coupler.

摘要

In a conventional optical heterodyne receiver with a standard six- port fibre coupler, a loss of sensitivity occurs compared with an optical heterodyne receiver with a 90 DEG hybrid and, furthermore, laser amplitude noise is inadequately suppressed. Therefore, according to the invention, the receiver with a six-port fibre coupler (K) is designed as a pair of balanced receivers, so that the photocurrent amplifiers connected behind the photodiodes (PD1, PD2, PD3), through suppression of the DC components in the photocurrent, receive only the differences in current between the photocurrents of in each case two photodiodes.