Condensed Matter Physics Seminar: A new dynamic method for long distance acoustic sensing using fiber optic, based on OFDR

Abstract:

The many advantages of fiber optic sensors (FOS) have made it a popular topic for research in the last 40 years. These sensors are capable of measuring a great variety of different physical phenomena from temperature to acceleration.

A novel method for phase sensitive quasi-distributed vibration and acoustical sensing is presented. The method is based on double Optical Frequency Domain Reflectometry (OFDR) interrogation of a sensing fiber, with an array of discrete weak reflectors. The method's effectiveness was presented theoretically and experimentally.

The second part of the work deals with the crosstalk phenomenon. A mathematical model for a general acoustical perturbation in an OFDR system was formulated, showing that the perturbation causes parasitic phenomena, generating both a frequency shift and a frequency modulation. These effects are known as crosstalk. The proposed model in the general case were the optical phase changes in the fiber are faster than the laser's scan rate was experimentally substantiated. The use of a high pass filter was shown to improve and even overcome the influence of this crosstalk phenomenon.

This work adds a new practical and feasible technique to the fiber optics sensors toolbox.

Seminar Organizer: Prof. Sasha Gerber