Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave\nlasers provide broadband coherent sources with high power per line and independent control of line\nspacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and\noptimized sources for the interrogation of other sensors based on wavelength change or wavelength\nfiltering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation\nsystem based on a single laser and two optical-phase modulators is presented. This architecture\nallows for the configuration of multimode optical source parameters such as the number of modes\nand their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping\nthe optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation\nscheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are\npresented for dual-comb operation under optimized control. The optical modes are mapped onto\ndetectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz).\nMeasurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system.\nUltrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg\nwavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum.\nThe amplitude modulation of two counterphase tones is detected to obtain a differential measurement\nproportional to the ultrasound signal.
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