| 摘要 |
PROBLEM TO BE SOLVED: To provide a differential phase modulation-signal demodulation circuit that can remarkably reduce loss of signal information due to an optical nonlinear effect of an optical waveguide by easily demodulating a signal subjected to differential phase modulation into intensity information and further enables optical transmission over a long distance, and to provide a demodulation method thereof.SOLUTION: The center of a differential filter is aligned with a center frequency ωof a spectrum extended on a focal surface of a slab waveguide 204. Continuous light from a DFB laser 101 is subjected to differential phase modulation by a phase modulator 102 using an NRZ waveform. The differential phase signal is transmitted through an optical fiber 103 and incident on an array waveguide grating 105 through an optical circulator 104. The transmitted phase modulation signal is differentiated by the differential filter 106 disposed on the focal surface of the array waveguide grating 105, so that a phase variation point is subjected to intensity modulation, and thus converted to an RZ signal of 40 Gbps that can be received by an ordinary photodiode. |
