A novel method for location of buried optical cables, where an incident EM wave modulates the polarization of guided light, using the Faraday effect

Abstract

This paper presents results and detailed theoretical analysis of a novel method to locate the position of buried optical cables. A travelling EM wave (RF), generated from above ground, modulates the state of polarization of the light propagating in the single-mode fibre to be located. The magnitude and phase of this modulation are detected at the end of the fibre route and the results are relayed to the operator of the locator. By observing the amplitude of this modulation, the lateral position of the buried service can be determined. We have demonstrated an 18 dB signal-to-noise ratio, at a buried depth of 1.5 m, in wet clay soil, using a radiated RF power of 38 W at 144 MHz.