An Allan variance real-time processing system for frequency stability measurements of semiconductor lasers

A real-time frequency stability measurement system for semiconductor lasers was developed. Since the frequency of the input signal is measured successively without clearing the counter, measurements of the Allan variance made with this system are more accurate than those made with conventional instruments. The Allan variance can be measured for integration times τ from 1 μs to 10000 s, and the number N of measured frequencies averaged over the integration time τ can be arbitrarily selected up to N=707 for each integration time. The highest measurable frequency was 90 MHz. It was demonstrated experimentally that this system can be used for measurements of the frequency stability of semiconductor lasers