Demultiplexed detection of ultrafast optical signal using interferometric cross-correlation technique

A novel demultiplexing method using the interferometric cross-correlative technique is described and experimentally demonstrated for detecting ultrahigh-speed optical signals. In the proposed technique, cross correlation between the local pulse is observed through the first-order mixing of lightwaves to detect the existence of signal pulses. The only factor limiting the bit rate is the pulse width of the local oscillator's light: the responses of all other phenomena including detector's electrical circuits do not affect the maximum signal detection speed. Several characteristic of the detection method are clarified through the theoretical investigation. In an experiment, the demultiplexed detection of a 25 Gb/s pulse train is successfully demonstrated, for the first time to the author's knowledge, using the proposed method.