VERFAHREN UND GERÄT ZUR FERNABFRAGE DER DOPPELBRECHUNG VON AUF BRAGGGITTERFASERN BASIERENDEN SENSOREN

A method for measurements of the orthogonally polarized minimum and maximum Bragg wavelengths of one of several birefringent fiber Bragg grate FBG sensors, and alternatively a method for eliminating errors in FBG sensor measurements caused by undesired grating birefringence, using an FBG wavelength interrogation apparatus, where the light from a polarized wavelength swept narrowband source (1) is passed through an electrically controllable polarization controller (2), operated in either a scanning mode or a tracking mode to find the two orthogonally polarized reflection spectra of the birefringent FBGs (6) with corresponding minimum and maximum Bragg wavelength gammanx and gammanx, where a low-birefringent reference FBG with known wavelength (5) and a low-birefringent fixed Fabry-Perod interferometer (8), generating frequency equidistant peaks are used in combination to provide accurate and readable wavelength measurements.