METHODS OF ACHIEVING ULTRA NARROWBAND OF SENSOR AND INCREASING NUMBER OF SENSORS CONNECTABLE TO SYSTEM IN DISTRIBUTION TYPE MEASUREMENT SYSTEM USING LIGHT WAVELENGTH DETECTION METHOD

摘要

PPROBLEM TO BE SOLVED: To solve the problems that a signal-to-noise ratio is small because variation of a reflected light amount is very little even when a central wavelength is varied in an optical fiber Bragg grating (hereinafter referred to as FBG) used in an optical fiber distribution measurement system and a measurement value of the central wavelength extremely fluctuates due to external electromagnetic noise to a light reception element in a wavelength detector. PSOLUTION: Sensors reflecting one narrowband reflective spectrum and emitting a flat spectrum in a wavelength region other than the reflective band of the FBG are used, in which a first ring resonator of narrowband FWHM and a second ring resonator having the built-in FBG of FWHM wider than the FWHM in the ring resonator are connected by an optical directional coupler, and the first ring resonator and an optical fiber of a signal transmission line are connected by another optical directional coupler. Thus, the optical fiber distribution measurement system having a sufficient signal-to-noise ratio is achieved without reducing the number of sensors. PCOPYRIGHT: (C)2009,JPO&INPIT