| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect lock of an input optical signal and a beat optical signal in an optical phase locked loop apparatus. <P>SOLUTION: The optical phase-locked loop apparatus 1 is provided with a first phase detector 10 for outputting a first phase comparison signal between the input optical signal and the beat optical signal, a loop filter 20 for shaping the first phase comparison signal, and an optical voltage-controlled oscillator (OVCO) 30 for outputting the beat optical signal on the basis of the shaped first phase comparison signal. The apparatus 1 is provided with a π/2 shifter 130A as a phase shifter for shifting the phase of the beat optical signal, and a second phase detector 140 for outputting a second phase comparison signal between the input optical signal and the beat optical signal subjected to phase shift. When the phases of two optical signals to be compared in the second phase shifter 140 are synchronized with each other, the π/2 shifter 130A applies phase shift to the beat optical signal by π/2 in which its phase comparison signal does not become zero. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
