OPTICAL TRAMSMITTER

摘要

PROBLEM TO BE SOLVED: To simultaneously transmit an AM modulation signal which is frequency-multiplexed and the other signal at low cost by setting a difference between the center frequencies of a local oscillation light and a light signal which is frequency-modulated to be larger than the sum of the half value of the occupied frequency bandwidth of the light signal which is frequency-modulated and the occupied frequency bandwidth of a signal different from the light signal. SOLUTION: A collective FM modulator 3 is provided with an optical frequency modulation part 31, an optical frequency local oscillation part 32, an optical multiplexing part 33 and an optical heterodyne detection part 34. The difference between the center optical frequencies of local oscillation light and the light signal which is frequency-modulated is set to be larger than the sum of the half value of the occupied frequency bandwidth of the frequency-modulated light signal and the occupied frequency band of the second signal different from the frequency modulated light signal. The signal can be multiplexed without being overlapped with the second signal by setting the intermediate frequency of batch frequency modulation to be larger than a value obtained by adding the occupied frequency bandwidth of the second signal to the half value of the occupied frequency bandwidth of the batch FM video signal. Thus, the AM modulation signal and the other signal can simultaneously be transmitted.