Simple circuit for feedback stabilization of a single-mode optical fiber interferometer

Single-mode optical fiber interferometers used with fiber hydrophones and other types of fiber sensors must be feedback stabilized to achieve maximum sensitivity and linearity in the presence of differential phase drift in their arms resulting from temperature fluctuations and other types of disturbances. A simple and effective electronic circuit for stabilizing such interferometers is described. The bandwidth of the feedback loop is 5 kHz, sufficiently wide to include information signals in addition to the drift correction signals. A high pass filter is used to remove the drift correction signals from the information signals.