Fiber optic interferometric sensor array with increased multiplexing density

Abstract

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

Dependencies are inferred from the claim text.