Patent ID: 8797538

Claim:
A fiber-optic interferometer, including: a wideband optical source ( 1 ) capable of emitting an incident optical beam with a central wavelength λ and a spectral width Δλ FWHM , having a decoherence time τ DC =λ 2 /(c·Δλ FWHM ), a coil with N turns of a single-mode optical fiber ( 5 ) of total length L, said fiber ( 5 ) having a first and a second ends, optical means capable of splitting the incident beam into a first and a second beam and of coupling the first beam to the first end and the second beam to the second end of the optical fiber ( 5 ), respectively, so that the first beam travels through the optical fiber ( 5 ) in a first direction and the second beam travels through the optical fiber ( 5 ) in a counter-propagating direction, said optical means being capable of combining into an output beam the two beams emerging respectively from the two ends after propagation through the fiber ( 5 ), a detector capable of detecting the interference of the output beam, characterized in that the optical fiber ( 5 ) is a high polarization mode dispersion (PMD) optical fiber, the length L of the optical fiber coil ( 5 ) is higher than twice the correlation length of the fiber ( 5 ), L>2·L c , so that the fiber ( 5 ) operates in coupled PMD regime and the group propagation time differential (DGD) between two orthogonal polarization states cumulated over the length L of the fiber ( 5 ) is higher that the decoherence time of the source: DGD>τ DC .