Enhanced spatial resolution of quasi-distributed weak fiber Bragg grating array sensor based on wavelength- division resonance frequency mapping

We demonstrated the novel quasi-distributed optical fiber sensor with tens of cm spatial resolution based on the wavelength-division resonance frequency mapping technique. To interrogate a weak fiber Bragg grating (FBG) array with a reduced interval length below ~1 m, a wavelength-division optical delay system was employed to separate the adjacent reflections. In our scheme, the sensing head consists of three Bragg wavelengths in the FBG series, which are repeatedly located 15 times along the optical fiber. Thus, 45 weak FBGs can be successfully interrogated using three channels without decreasing the dynamic range of the measured strain or temperature.