| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical DQPSK receiver further inexpensive and reduced in size and in power consumption, the receiver performing phase control upon an optical DQPSK signal using a Costas loop, and a phase control method thereof. <P>SOLUTION: Photodetectors 31, 32 are disposed in outputs of an optical interferometer 27 for I-phase signal demodulation and an optical interferometer 28 for Q-phase signal demodulation. An electric signal outputs of the photodetectors 31, 32 is partially extracted and connected to limiting amplifiers 33, 34 and low-pass filters (LPFs) 35, 36. LPFs 37, 38 are connected to outputs of the limiting amplifiers 33, 34. An output of the LPF 35 and an output of the LPF 38 are input to a multiplier 39, and an output of the LPF 36 and an output of the LPF 37 are input to a multiplier 40. Outputs of the multipliers 39, 40 are input through averaging circuits 41, 42 to arithmetic circuits 43, 44, inversion processing 45 is applied thereto along a one-side route, and results thereof are connected to inputs of driving circuits 46, 47 for controlling phase adjusters. The driving circuits 46, 47 perform feedback control upon phase adjusters 29, 30, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT |
