Parker Johnston

Project: Exploring Polarization Stability in Next-Gen Optical Links

Lab Group: Schow Group

Graduate Mentor: Aaron Wissing

Abstract: The rapid expansion of artificial intelligence and cloud computing has intensified the need for high-bandwidth, energy-efficient optical communication systems. Although optical fiber supports the propagation of two orthogonal polarization states, existing data center optical links use single polarization intensity modulation and direct detection (IMDD). Coherent and IMDD modulation formats exploiting dual-polarization can be used in future optical links to meet the growing bandwidth demands on data centers. However, the sensitivity of these systems to mechanical disturbances presents a critical challenge for stable deployment in dynamic data center environments. To investigate polarization stability under mechanical stress, we conducted impact testing on an optical fiber using a calibrated weight-drop system with varied impact tip diameters and discrete drop heights. Each condition was repeated 50 times. Prior to each impact, a polarization scrambler randomized the state of polarization (SoP). SoP trajectories were tracked in real time using a polarimeter positioned downstream of the impact zone, and impact force was captured via a sensor plate beneath the fiber. Across all conditions, we consistently observed abrupt, high-speed SoP shifts immediately following impact. Ultimately, higher drop heights and smaller tip diameters led to increasingly pronounced polarization changes. The experimental results will inform the requirements of polarization control schemes for future data center links exploiting dual-polarization.