Frequency discriminator and heterodyne receiver provided with the frequency discriminator for coherent lightwave communications

摘要

In a frequency discriminator in which it is adapted such that a signal to be subjected to frequency discrimination is divided into two signals and mixed together after one of the divided signals has been given a delay time, the frequency discriminator disclosed is additionally provided with a filter, of which cutoff frequency is set up according to the delay time, disposed in the front stage and, thereby, both improvement of accuracy in frequency identification and expansion of the capture range can be attained.