| This dissertation develops a new fiber optic interferometer and signal processing scheme which compensates for large environmental noise fluctuations in the same frequency band as the measurand. The interferometer is a two-loop Mach-Zehnder configuration, and the signal processing is a time-multiplexed direct-phase demodulation. A minimum detectable phase shift of 670 $mu$rad/$rm sqrt{Hz}$ is detectable at 1 Hz. The interferometer can also extract very slow optical phase changes, such as those caused by dissolution and diffusion of a solute into a solvent, from noise levels which would otherwise completely obscure the measurand. |
