Process for measuring rotation speeds about several axes, and a multiplexed multi-axial gyrofiber allowing this measurement

Process for measurement of rotation speeds about N axes, where N is not less than 2, using a fiber optic interferometric gyroscope comprising N interferometers I.sub.i in Sagnac ring, two counter-propagating waves propagating in each of the said interferometers I.sub.i, the wave propagation time between their separation and recombination being .tau..sub.i, the said duration .tau..sub.i associated with interferometers I.sub.i being approximately equal to a common transit duration .tau., the said process being such that:

• signals are emitted by a common light source to all interferometers I.sub.i,
• the said signals are detected after passing through interferometers I.sub.i in a common photodetector,
• phase modulators generate controlled modulation phase differences .delta..PHI..sub.c,i between the counter-propagating waves propagating in each of interferometers I.sub.i,
• modulators are controlled, signals originating from the photodetector are demultiplexed and demodulated, and rotation speeds of interferometers I.sub.i are extracted by a processing unit, the said signals emitted by the source reaching all interferometers I.sub.i, then photodetector, almost simultaneously,
• wherein the said controlled modulation phase differences .delta..PHI..sub.u,j generated by modulators comprise biasing components .delta..PHI..sub.m,i with a common modulation period T.sub.m approximately equal to twice 2.tau. the common transit duration .tau., and with common amplitude equal to a phase bias that is not a multiple of .pi., the value of each biasing component .delta..PHI..sub.m,i at time t being opposite to the value of the said component at time t+T.sub.m /2, each half-period T.sub.m /2 being divided into at least N time intervals 67 t.sub.i and wherein a sign change is produced in the biasing component .delta..PHI..sub.m, associated with each interferometer I.sub.i at the beginning of one and only one time interval .delta.t.sub.i, such that a signal arriving at the processing unit is affected simultaneously by Sagnac phase shifts .delta..PHI..sub.s,i representing rotation speeds of the set of interferometers I.sub.i, and is added to the modulation phase differences .delta..PHI..sub.c,i, the said Sagnac phase shifts .delta..PHI..sub.s,i being extracted by the processing unit by sampling the said signal on the N .delta.t.sub.i time intervals .delta.t.sub.i.