Patent ID: 8189200

Claim:
Apparatus for multiplexing and demultiplexing Fiber Optic Interferometric Sensors (FOISs), said apparatus comprising: means ( 1 ) forming an optical source for providing l×n distinct trio {ν qj , F j , τ j } for the interferometric interrogation of l×n×m sensors, wherein the optical source comprise n optical emitters ( 4 qj ) organized in p groups (S j ) of nip optical emitters each, for providing n lights of distinct light frequencies ν qj for 1≦j≦p and 1≦q≦n/p where F j is a RF carrier frequency generated upon the lights of the n/p emitters emitting at the frequency ν qj , and τ j is a time window where the light of the nip emitters are on, at least one sensing cable ( 100 ) comprising n groups ( 5 qj ) of m fiber optic interferometric sensors ( 54 qj,k ) each, and means ( 6 qj ) for dedicating a unique given trio {ν qj , F j , τ j } to the interrogation of a unique group ( 5 qj ) of m fiber optic interferometric sensors; at least one wavelength demultiplexing system ( 40 ) for separating the n frequencies ν qj into nip outputs ( 33 q ) containing respectively the lights of wavelength bands B q for 1≦q≦n/p, where B q contains the p wavelengths ν qj for 1≦j≦p, each output ( 33 q ) having at least one photo-detector ( 7 q ) followed by one demodulator scheme ( 8 q ) receiving interference signals of at least two groups ( 5 qj ) of m fiber optic interferometric sensors each and born by the carrier frequencies Fj for a given group ( 5 qj ) of sensors for 1≦j≦p; a calibration system for determining an absolute time foot-prints of the interference signals of said at least two groups ( 5 qj ) of m fiber optic interferometric on the qth photo-detector ( 7 q ).