Distributed OTDR-interferometric sensing network with identical ultra-weak fiber Bragg gratings

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Acoustic Measurement Technologies

Background:

• Distributed sensing networks are crucial for monitoring physical parameters.
• Ultra-weak fiber Bragg gratings (uwFBGs) offer unique sensing capabilities.
• Phase-sensitive optical time domain reflectometry (φ-OTDR) is an advanced technique for fiber optic sensing.

Purpose of the Study:

• To demonstrate a novel distributed sensing network for acoustic measurement.
• To investigate the performance of ultra-weak fiber Bragg gratings (uwFBGs) in a φ-OTDR system.
• To achieve simultaneous demodulation of phase, amplitude, frequency response, and location information.

Main Methods:

• Implementation of a distributed sensing network with 500 identical uwFBGs.
• Utilizing a balanced Michelson interferometer with phase-sensitive optical time domain reflectometry (φ-OTDR).
• Employing passive 3 × 3 coupler demodulation for data acquisition.

Main Results:

• Successful demodulation of distributed acoustic signals in laboratory experiments.
• Achieved a pressure detection limit of 0.122 Pa.
• Obtained an acoustic phase sensitivity of approximately -158 dB (re rad/μPa) with a flat frequency response from 450 Hz to 600 Hz.

Conclusions:

• The demonstrated system effectively performs distributed acoustic sensing using uwFBGs and φ-OTDR.
• The system offers high sensitivity and a wide frequency response for acoustic measurements.
• This technology has potential applications in various acoustic monitoring scenarios.