| 摘要 |
Frequency shift keying (FSK) is advantageous for optical heterodyne reception, since no additional modulator is required in the transmitter. However, according to the present state of the art, signals subjected to frequency shift keying cannot be demodulated with homodyne receivers. In order to reduce expense in the transmitter and, where the transmission of high bit rates is involved, in the receiver also, an optical heterodyne receiver is proposed which, following on from a 90 DEG optical-electrical hybrid (H) on the input side, contains one or two demodulators (DEM1, 2) connected in parallel on the input side, in each case comprising two branches which contain an analog multiplier (M1) and a delay component (T1) and in which the signals of the branches are combined by an adder or a subtracter (SUB1). <IMAGE> |
