Multiple vibrations measurement using phase-sensitive OTDR merged with Mach-Zehnder interferometer based on frequency...

Area of Science:

• Optoelectronics and Photonics
• Sensing Technology
• Signal Processing

Background:

• Accurate measurement of multiple high-frequency vibrations is crucial for various industrial and scientific applications.
• Existing sensing techniques often suffer from limitations such as dead zones or restricted frequency ranges.
• Combining different optical sensing principles offers potential for enhanced performance.

Purpose of the Study:

• To develop and demonstrate a novel measurement scheme for simultaneous detection of multiple high-frequency vibrations.
• To integrate phase-sensitive optical time domain reflectometry (Ф-OTDR) with Mach-Zehnder interferometry (MZI) for vibration analysis.
• To achieve high spatial resolution and a wide detectable frequency range without sensing dead zones.

Main Methods:

• A hybrid sensing system combining Ф-OTDR and MZI based on frequency division multiplexing was designed.
• A light source was modulated using an acousto-optic modulator (AOM) with a 200 MHz frequency shift for the Ф-OTDR.
• Vibration frequency was demodulated by the MZI, while vibration location was determined by the Ф-OTDR system.

Main Results:

• The system achieved a spatial resolution of 10 meters over a 3 km sensing fiber.
• Detectable vibration frequencies reached up to 40 kHz.
• The proposed scheme demonstrated simultaneous measurement of multiple high-frequency vibrations using frequency spectrum mapping, with no dead zones observed.

Conclusions:

• The novel combined Ф-OTDR and MZI system effectively measures multiple high-frequency vibrations with high spatial resolution and broad frequency detection.
• The developed technique overcomes the dead zone limitation inherent in some previous optical sensing methods.
• Experimental results validate the system's performance and its potential for advanced vibration monitoring applications.