Pulsed laser fiber-optic gyroscopes

Interferometric fiber-optic gyroscopes interrogated with narrow-linewidth lasers are highly sensitive to Rayleigh backscattering. Commonly used broadband incoherent sources can strongly suppress it, but are responsible for extra noise and instability. Here we propose and experimentally demonstrate an interrogation scheme based on a pulsed laser beam generated by time-domain power gating, which allows to strongly suppress the backscattered light, up to three orders of magnitude in the Fourier frequency window between 10^-2 and 10³Hz. We use a highly coherent continuous wave laser, amplitude-modulated by an acousto-optic modulator, generating pulses that illuminate only about 2% of a 2 km-long interferometer. A pulse-width optimization, aimed at identifying the best trade-off between backscattering noise suppression and signal-to-noise ratio, demonstrated performances comparable to those of an amplified spontaneous emission source above 1 Hz. In our setup, this limit is only set by the pulse generation scheme based on a commercial fiber-optic modulator. Importantly, in our experiment, the devised interrogation approach proved a competitive alternative to suppress the long-standing issue of fiber backscattering. Furthermore, it is worth noting that the use of coherent lasers for fiber-optic gyroscope interrogation would not only provide better performance in terms of wavelength and intensity stability but could also pave the way to the implementation of non-classical coherent quantum sources.