Ultra-long range optical frequency domain reflectometry using a coherence-enhanced highly linear frequency-swept...

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Sensing
• Metrology

Background:

• Optical Frequency Domain Reflectometry (OFDR) is crucial for fiber optic sensing and network monitoring.
• Achieving both ultra-long range and high spatial resolution in OFDR remains a significant challenge.
• Nonlinearity and limited coherence in laser sources restrict OFDR performance.

Purpose of the Study:

• To develop an ultra-long range OFDR system with enhanced spatial resolution.
• To demonstrate a novel fiber laser source for improved OFDR performance.
• To enable real-time monitoring and sensing in extensive fiber optic networks.

Main Methods:

• Utilized a coherence-enhanced, highly linear frequency-swept fiber laser source.
• Implemented an optoelectronic phase-locked loop (OPLL) to stabilize the laser.
• Locked the laser to an all-fiber Mach-Zehnder interferometer (MZI) to suppress nonlinearity and boost coherence.
• Achieved a 1 GHz linear frequency sweep over 25 ms.

Main Results:

• Demonstrated 10 cm spatial resolution at a 20 km fiber link within 25 ms.
• Achieved 72 cm spatial resolution over a 200 km fiber link within 5 ms.
• The developed OFDR system exhibits high coherence and linearity.

Conclusions:

• The proposed OFDR system offers a high-performance solution for ultra-long range measurements with high spatial resolution.
• This technology is suitable for field real-time fiber network monitoring and sensing.
• The coherence-enhanced laser source is key to overcoming previous OFDR limitations.