Feature

Intrinsic Thermal Phase Noise Limit in Optical Fiber Interferometers

Keith H. Wanswer, Alan D. Kersey and Anthony Dandridge

Optical fiber interferometers are used for several high sensitivity measurement applications, such as acoustic sensors, magnetometers, accelerometers, and gyroscopes. variety of noise sources limit the phase shift detection sensitivity attainable using fiber interferometric sensors. The most often quoted (and desired) intrinsic minimum detectable phase shift in interferometric optical systems is the shot, or quantum noise limit. In interferometric optical fiber sensors, the shot noise limit often can be realized; minimum detectable phase shifts of a few μrad/Hz at frequencies above a few hundred Hz are readily achieved with modest detectable power levels of a few microwatts. When shot noise dominates, minimum detectable phage shift performance improvements can be obtained simply by increasing the detected power levels.