Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes.

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Telecommunications

Background:

• Distributed optical fiber sensing relies on monitoring optical phase changes for applications like vibration detection.
• Accurate estimation of fiber response is crucial and depends heavily on light modulation and optical field capture methods.
• Existing methods like pulse-cloning or spectral-sweep can be complex and limited in performance.

Purpose of the Study:

• To enhance the performance of distributed optical fiber sensing systems for detecting mechanical events.
• To introduce a simpler and more effective setup by leveraging telecommunication techniques.
• To improve the sensitivity and bandwidth of coherent phase-sensitive optical time-domain reflectometry (ϕ-OTDR) systems.

Main Methods:

• Utilized techniques from coherent optical transmission in telecommunications.
• Developed a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences.
• Applied sequences simultaneously in phase and quadrature on two orthogonal polarization states to estimate the fiber Jones matrix.
• Achieved perfect channel response estimation of the sensor array under specific conditions.

Main Results:

• Demonstrated enhanced sensitivity and bandwidth for coherent ϕ-OTDR systems.
• Achieved a linear response in the sensor array.
• Showcased bandwidth coverage up to 18 kHz.
• Successfully tested with a sensor array comprising 10 fiber Bragg gratings (FBGs).

Conclusions:

• The proposed method, leveraging telecommunication techniques, offers a simpler setup and superior performance for distributed optical fiber sensing.
• The novel probing technique enables accurate fiber response estimation, significantly enhancing sensitivity and bandwidth.
• This advancement is crucial for applications requiring precise detection of acoustic signals and vibrations.