An investigation of Rayleigh backscattering: utilizing coherent laser sources for enhanced IFOG performance

Interferometric fiber-optic gyroscopes (IFOGs) are usually interrogated by broadband incoherent light sources instead of narrow linewidth coherent lasers. One of the main reasons is the problem of Rayleigh backscattering into the fiber, whose components sum up coherently for lasers and incoherently for broadband sources. In this work we investigate the possibility to use an amplitude modulated laser for interrogating an IFOG, which brings to a strong Rayleigh backscattering noise suppression. For this purpose, light is sent as short pulses of 1.86 <i>&mu;s</i> width and 18.6 <i>&mu;s</i> period in a 2-km fiber loop, which ensures the least temporal overlap between the forward-propagating and backscattered light. This technique reduces the cumulative backscattered power and its negative effect on system performance. The experimental investigation into pulse modulation presented here clearly demonstrate that pulse modulation improves stability and precision up to an order of magnitude, with critical timescales of noise levels lowered by a factor of ten, improving the performance of IFOG systems.