VERFAHREN ZUR UEBERWACHUNG DES SIGNAL/ RAUSCH-VERHAELTNISSES AUF OPTISCHEN UEBERTRAGUNGSSTRECKEN

摘要

A method of monitoring an amplifier in an opto-electrical circuit, comprising the steps of comparing with a reference value the value of an automatic gain control signal to control the degree of amplification of an optically derived information signal in the amplifier, and applying the difference between the two values to indicate the deviation from a predetermined value of the signal-to-noise ratio in the amplifier. The difference between the two values can be so applied as to cause the amplifier to emit an alarm signal when the value of the gain control signal in the amplifier exceeds a reference value. Alternatively, the difference between the two values can be applied to indicate the deviation from a predetermined value of the bit error rate in the optically derived signal.