| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the temperature drift of a Mach-Zehnder type photosynthesis phase difference for transmitting a high-frequency signal by using an optical fiber. SOLUTION: An unbalance Mach-Zehnder type external optical modulator 3 subjects the optical carrier wave from a light source 1 to double sideband modulation suppressing the carrier wave by the high-frequency signal of a frequency f and outputs the same to an optical fiber transmission path 7. The output light from this optical modulator 3 is partly branched by an optical branching device 10 and is converted by a photodetector 11 to an electric signal. The high-frequency signal of the frequency f is extracted by a band-pass filter 12. A mixer 13 subjects this extracted high-frequency signal to coherent detection with the high-frequency signal of the frequency f from a signal source 14 which is delayed by a delay line 15. This detection output is smoothed by a low-pass filter 16 and a control signal is formed. This control signal is biased by the DC voltage of a DC power source 7 and is superposed on the high-frequency signal from the signal source 14 by a bias T circuit 18.</p> |
