SYSTEMS AND METHODS FOR SAGNAC INTERFEROMETRY

A system for fibre-optic Sagnac interferometry, the system comprising: an optical source; an optical splitter configured to split light from the optical source into a first optical beam and a second optical beam; an optical circuit comprising a first modulation unit, a second modulation unit, and an optical fibre operatively coupled between the first and second modulation units, wherein the optical circuit is operatively coupled to the optical splitter such that the first and second optical beams traverse the optical circuit in opposite directions, the first optical beam being modulated by the first modulation unit before being modulated by the second modulation unit, and the second optical beam being modulated by the second modulation unit before being modulated by the first modulation unit, wherein the first modulation unit is configured to modulate light passing through it with a first modulation code, and the second modulation unit is configured to modulate light passing through it with a second modulation code which is different from the first modulation code; an optical detector configured to detect the first and second optical beams after the first and second optical beams have traversed the optical circuit; and a processing system configured to receive from the optical detector an interference signal, which is indicative of an optical phase difference between the first and second optical beams, and to determine the optical phase difference by demodulating the interference signal based on the first and second modulation codes; wherein a correlation of the first modulation code with a time-shifted version of itself is maximum for a zero time shift; and wherein a correlation of the second modulation code with a time-shifted version of itself is maximum for a zero time shift.