Patent ID: 7589312

Claim:
A physical quantity measuring system, comprising: an optical fiber in which a plurality of fiber Bragg gratings having different reflection wavelength changing bands are formed along said optical fiber in a longitudinal direction; a light source which outputs a broadband light covering the reflection wavelength changing bands of all of said fiber Bragg gratings into said optical fiber; an arrayed waveguide grating which divides a light reflected by said fiber Bragg gratings and outputted from said optical fiber into a plurality of divisional wavelength bands having a constant wavelength interval, and which outputs the divided lights to output channels, respectively; a plurality of light-receiving elements that receive output lights from the output channels, respectively; and an operating portion which detects a change of a reflected center wavelength of each fiber Bragg grating by a change of an output of each of the light-receiving elements, and which calculates a physical quantity and a position thereof given to said optical fiber, said operating portion capable of detecting light from adjacent output channels, wherein a difference between adjacent output channels in a characteristic of an amount of a light output with respect to a wavelength based on a superposition of a reflection loss characteristic of said fiber Bragg gratings with respect to a wavelength and a transmission loss characteristic of said arrayed waveguide grating with respect to a wavelength, is kept within a dynamic range of said operating portion with respect to the band of the reflection wavelength change of said fiber Bragg grating.