Differential fiber optical sensor with interference energy analyzer

A differential fiber optical sensor, comprising:

• a test fiber with a plurality of double-fiber grating elements positioned along the test fiber, all fiber gratings having overlapping reflection spectra, and each said double-fiber grating element consist of two fiber gratings, separated by a unique distance inherent for this element only,
• a light source to radiate light inside a measurement wavelength range, said light source producing a beam of light propagating along test fiber;
• an optical filter connected to the light source having possibility to change its central transmission wavelength inside said measurement wavelength range, the output radiation of said optical filter having a coherence length, which exceeds distance between Bragg gratings in any one element;
• a fiber optic beamsplitter having a first port connected to the optical filter, a fourth port connected to the test fiber, so as beam of light emitted by broadband light source and passed through optical filter is launched in test fiber, and a second and a third ports;
• an optical reflection detector to receive the light flux, connected to the second port of optic beamsplitter so as to detect the reflected from the test fiber light flux, the said reflection detector being operable to sense changes in the intensity of the reflected from the test fiber light flux inside the measurement wavelength range,
• an interference energy analyzer connected to reflection detector, said interference energy analyzer calculate the energies of the interference patterns separately for each double-Bragg grating element, interference patterns are created by beams reflected from double-Bragg grating elements.