Cleaved-coupled-cavity-laser-driven system for measuring small signals.

摘要

A laser-driven interferometric signal sensing system has a cleaved-coupled cavity laser (10) with separate stabilization servo loops (12-16, 20-29) of different time constants for the modulator (11) and laser (18) sections thereof. The laser section is biased (14) above lasing threshold, and its stabilisation loop is operated at a frequency twice the frequency of laser section bias current modulation. A laser loop feedback error signal (from 32) is a function of predetermined, environmental-type, parameter variations in the sensing location and is processed (31, 32, 36) to be a function of the second derivative of intereferometer output intensity with respect to laser section current. That error signal is applied to modify (20) laser section bias current in a direction to zero out the feedback signal.