Thesis:

Active phase stabilization of a distance-scalable fiber-optic interferometer

We present the design and implementation of an active phase-stabilization system for adistance-scalable Mach-Zehnder interferometer aimed to incorporate a 10.8km underground optical fiber link at Fermilab. The system employs a coherent self-homodyne detection scheme with a 90-degree optical hybrid to generate In-phase (I) and Quadrature (Q) signals, which provides an error signal for a high-bandwidth feedback loop. A low-latency, Field-Programmable Gate Array (FPGA) controller executes a Proportional-Integral-Derivative (PID) control algorithm, applying real-time phase corrections via an Electro-Optic Modulator (EOM) to counteract environmental phase noise. We present a full characterization of the free-drifting phase noise and demonstrate a significant reduction, quantified by using its standard deviation and Power Spectral Densities (PSDs). The successful implementation of this feedback system is expected to achieve robust, long-term phase locking, establishing a stable interferometric platform for future quantum networking experiments and many other applications requiring precise phase control over long fiber links.