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Canon laser Doppler velocimeters , equipped with diffraction gratings , take advantage of an optical system ( diffraction laser light Doppler method ) that will not dependent on the laser wavelength . Fiber optic sensors utilizing Bragg gratings are increasingly being used for temperature and strain measurements . In recent years the technology for recording second-generation holographic gratings has matured sufficiently to warrant serious consideration by the astronomical community . FUSE and HST / COS both capitalize on the performance enhancements provided by first-generation holographic gratings , aberration-corrected gratings recorded with spherical wave-fronts . To avoid these pit falls we have installed in X-GEF two gratings which serve as efficiency references .