A Low-Frequency Tone Sweep Method for in-Service Fault Location in Sub-Carrier Multiplexed Optical Fiber Networks

TL;DR

This paper introduces a novel low-frequency tone sweep method for accurately locating faults in optical fiber networks by analyzing the frequency response of backscattered signals, overcoming traditional spatial resolution limits.

Contribution

The proposed technique reconstructs the fiber transfer function in the frequency domain, enabling precise fault detection without relying on Fourier Transform-based methods.

Findings

Fault location accuracy within 10 meters of standard OTDR

Effective detection of non-reflective faults

Overcomes spatial resolution limitations of traditional methods

Abstract

We demonstrate an optical fiber fault location method based on the frequency response of the modulated fiber optical backscattered signal in a steady state low-frequency step regime. Careful calibration and measurement allows for the reconstruction of the fiber transfer function, which, associated to its mathematical model, is capable of extracting the fiber characteristics. The technique is capable of identifying non-reflective fault events in an optical fiber link and is perfectly compatible with previous methods that focus on the reflective events. The fact that the recuperation of the complex signal is performed in the frequency domain and not via a Fourier Transform enables the measurements to overcome the spatial resolution limitation of Fourier Transform incoherent-OFDR measurements even with frequency sweep ranges down to 100-100000 Hz. This result is backed up by a less than 10 meters difference in fault location when compared to standard OTDR measurements.