Line monitoring system having frequency modulation for noise reduction

The FM-OTDR system addresses SNR degradation in undersea optical communication systems by shifting beating frequencies out of the baseband, enhancing signal sensitivity and improving Rayleigh backscattering detection through frequency modulation and Golay codes.

WO2026039230A1 Publication Date: 2026-02-19SUBCOM LLC
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Patent Information

Application Number
PCT/US2025/040634
Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
Priority Date
2024-08-15
Filing Date
2025-08-05
Publication Date
2026-02-19

AI Technical Summary

Technical Problem

Existing line monitoring equipment in undersea optical communication systems face significant signal-to-noise ratio (SNR) degradation due to signal-signal beating noise, particularly in high-loss loop-back systems, which hampers effective detection of Rayleigh backscattering signals.

Method used

Implementing a Frequency Modulated Optical Time-Domain Reflectometry (FM-OTDR) system that uses frequency modulation to shift beating frequencies out of the signal baseband, employing chirp subcarriers and Golay codes to enhance signal sensitivity and reduce interference noise.

Benefits of technology

The FM-OTDR system effectively reduces signal-signal beating noise, improving the signal-to-noise ratio and enabling more accurate detection of Rayleigh backscattering signals, even in long-distance undersea optical communication systems.

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Abstract

A sensing system. The sensing system may include a transmitter to launch an outbound optical signal, a clock to generate a clock signal, and a chirp subcarrier coupled to the clock and configured to generate a chirp. The sensing system may further include a code generator coupled to the clock and configured to generate a code; and an intensity modulator, arranged to modulate the outbound optical signal and coupled to receive an intensity modulator signal that is derived at least in part from the code generator.
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