סמינר מחלקתי אלקטרוניקה פיזיקאלית : איתי שפאץ

You are invited to attend a lecture

Implementation and Characterization of Lumped Rayleigh Reflectors

By:

Itai Shpatz

MSc student under the supervision of Prof. Avishay Eyal

Abstract

Distributed Acoustic Sensing (DAS) via optical fibers makes use of Rayleigh backscattering for detection of acoustic waves which interact with the fiber along its entire length. The random nature of Rayleigh backscattering and the low mean power of the backscattered light lead to non-uniform performances. In addition, distance-dependent Signal to Noise Ratio (SNR) degradation is always present due to propagation loss. In contrast, arrays of discrete reflectors (such as weak FBGs with equal center wavelengths) provide a higher mean power of backreflected light, and the use of them offers deterministic performance which can be designed to be uniform along the fiber.

In this work, an easy-to-implement and accessible approach for implementing Rayleigh-based discrete reflectors which can offer enhanced detection performance in selected regions. It is based on enclosing sections of the fiber in acoustically insulated boxes to create Lumped Rayleigh Reflectors (LRRs). The suggested discrete reflectors are made from the fiber itself, with no need for splicing or adding a specially designed fiber.

The LRR method is studied through mathematical formulation and experiments. Besides diminishing the randomness in detection sensitivity, the method enables increasing the detection SNR far beyond the typical value for Rayleigh-based DAS and obtaining sensitivities comparable with discrete reflectors. The proposed method is successfully tested and demonstrated via experiment, where an SNR improvement is obtained in a setup in which the signal source is located after 25km of fiber.

On Wednesday, July 25, 2018, 11:00

Room 234, ‘Wolfson’ building