An underground fiber cable discrimination method based on laser interferometer

TL;DR

This paper introduces a laser interferometer-based method for underground fiber cable discrimination, addressing limitations of existing vibration sensing techniques like DAS, and demonstrates its effectiveness over a 40-km urban fiber link.

Contribution

The paper proposes a novel laser interferometer approach for fiber cable discrimination, overcoming DAS limitations and enabling practical underground cable identification.

Findings

Laser interferometer method provides clear knock event detection.

DAS method is ineffective for long-distance underground cable discrimination.

The proposed method is practical for urban fiber network maintenance.

Abstract

The maintenance and repair of optical fiber networks often requires the discrimination of underground cables among a group of buried ones. Presently, the methods commonly used are either inefficient or harmful to the fiber cable. In this paper, we evaluate the effectiveness of fiber optic vibration sensing method on underground fiber cable discrimination. We find that the typical vibration sensing method-distributed acoustic sensing (DAS) is not suitable for fiber cable discrimination. Especially for long distance scenario, due to "frequency grafting" effect, the DAS method will give a false response on the spectrum of knock events during cable discrimination process. In response, we propose an underground fiber cable discrimination method based on laser interferometer, and demonstrate it on the 40-km urban fiber cable connecting Tsinghua University and Yongding Road. It can give an obvious and real response to the knock event, and can be used in practical applications.