| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical reception system that utilizes an advantage of differential phase modulation-direct detection (DPSK-DD) by relaxing the limitations of a frequency characteristic of a Mach-Zender interferometer. SOLUTION: In this system, transmission/reception for coherent light communications is conduced by receiving a differential coded phase modulated light and demodulating it. The system is provided with an encoder 13 that encodes an NRZ code input signal by converting a signal 0 into a space, while equally dividing 1 bit signal into 2n parts (n is a natural number), setting one of first equally divided two slots to a mark, the other slot to a space and coverting the remaining (2n-2) slots in the similar sequence so that a mark and a space are repeated sequentially, and with a Mach-Zender interferometer 14 that branches a phase modulated light in response to a signal coded by the encoder 13 into two, delays one signal light by 1/(2n) bits, makes both the signals interfered to convert them into an intensity modulated light. |
