Properties of bit-rate-independent pulse timing measurement technique using optical heterodyne cross correlation

A novel technique for detection of the time delay between optical input signal data and a clock, suitable for applications to phase-locked loops, is investigated. This pulse timing measurement scheme, which is based on heterodyne cross correlation employing passive optical mixing, does not rely on any characteristic time associated with an optical nonlinearity, and is virtually independent of the bit rate. Experimental results on self-heterodyne correlation of mode-locked laser pulses as well as detailed theoretical analysis indicate that the timing measurement method investigated is characterized by high sensitivity.