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Updated: Jun 12, 2026

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements
Published on: February 28, 2016
Research on fiber coupling characteristics of linearly polarized modes in coherent free space optical communication
Abstract:
This study examines the influence of relative motion-induced angular deviations on fiber coupling and communication performance in high-speed coherent free-space optical systems. Simulations reveal that higher-order modes experience a steeper drop in coupling efficiency than the fundamental mode as the incident angle grows. Using a spatial light modulator (SLM) and fast steering mirror (FSM) to generate higher-order linearly polarized (LP) modes and emulate angular tilt, the coupling behavior was experimentally validated. Within 0-1.2 mrad deflection, the LP01 mode's bit error rate (BER) increased from 4.978 × 10-13 to 1.302 × 10-6, accompanied by an error vector magnitude (EVM) rise from 8.65% to 10.73%. In comparison, the LP31 and LP03 modes reached EVMs of 11.89% and 16.92%, respectively, underscoring their heightened sensitivity to angular misalignment. These findings underscore the critical role of mode selection and tolerance design in high-capacity spatial optical receivers under angular mismatch.
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