Physical Electronics Dept.

** Seminar **

Amit Isseroff

(M.Sc. student under supervision of Prof. Avishay Eyal,

School of EE, Dept. of Physical Electronics)

Advanced Signal Processing and Algorithmic Techniques for Improved

Implementation of Low Loss Interferometric Sensor Arrays

Improvements on a previously proposed implementation of a low-loss interferometric sensor array are discussed in this work. The sensor array is based on a single Hi-Bi fiber divided into sections, each acting as a Mach-Zender interferometer. The signal processing algorithm relies on a periodic polarization frequency response of the array. In order to achieve a periodic frequency response, the segments’ lengths must be identical. In order to cope with this requirement, we developed a new method for creating coupling between the segments, based on placing removable mechanical pressure couplers along a single un-spliced fiber. In addition a new signal measurement and processing technique is presented, which allows exact measurement of segment lengths. These two innovations improve the overall sensor performance, since they allow a segment’s length calibration procedure to be conducted. The new coupling method is implemented on two systems. One of the systems is then used for field experiments in order to test overall applicability of the interferometric sensor array as an underground acoustic sensor. The second system which is composed of 14 segments with total length of ~210[m], is used in laboratory conditions in order to demonstrate the calibration procedure.

            Another significant improvement in system performance is demonstrated in this work by adding a reference interferometer that allows compensation of wavelength errors caused by non-ideal and non-linear wavelength sweeps that are used for interrogating the polarization frequency response.

Finally a modified “layer-peeling” algorithm, which allows for frequency dependence of elements in the array that were previously assumed as frequency independent, is suggested and evaluated using the implemented system.