HIGH-SPEED PULSED HOMODYNE DETECTOR IN OPTICAL COMMUNICATION WAVELENGTH BAND

摘要

The invention aims to raise operational frequency and S/N ratio of a pulsed homodyne detector to measure the quadrature amplitude of the signal pulse light. The local pulse light in telecom band is yielded at repetition rate of 80MHz. Two output lights are generated by interference of the local pulse light and the signal pulse light. A first photodiode and a second photodiode are connected differentially. The first photodiode converts one side output light to an electric signal. The second photodiode converts the other side output light to another electric signal. An M-derived low-pass filter eliminates the third harmonics of the local pulse light. Moreover, the higher frequency components than triple frequency of the repetition rate are eliminated. In this way, even when it is operated at high repetition rate of 80MHz at maximum, the quadrature amplitude of the signal pulse light can be measured with high quantum efficiency of about 90% and with S/N ratio of more than 10dB.