| 摘要 |
PROBLEM TO BE SOLVED: To achieve a demodulation method capable of detecting a multi-level signal at a high S/N ratio from an ultra high-speed coherent light time division multiplex signal obtained by modulating an amplitude and a phase of a light pulse simultaneously and performing acceleration by time division multiplex.SOLUTION: A receiving part has: a local oscillator; a light phase synchronization circuit synchronizing phases of a light pulse signal after transmission and local oscillation light with each other; a light demultiplexing circuit demultiplexing a high-speed light pulse into 1/N; and a homodyne/heterodyne detection circuit demodulating and detecting a coherent light signal. By using a CW light source as the local oscillator, a coherent light time division multiplex pulse signal is light-demultiplexed, and then, the light pulse is converted into CW light by using a dispersed medium and a light phase modulator. Further, coherent detection is performed on the local oscillation light by using the CW light. Thereby, a multi-level signal is demodulated at a high S/N ratio. |
