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Sensors (Basel). 2016 Nov 26;16(12). pii: E2007.

Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs.

Author information

1
Department of Electronics Technology, Universidad Carlos III de Madrid, Av. Universidad 30, E-28911 Leganés, Madrid, Spain. jposada@ing.uc3m.es.
2
Department of Electronics Technology, Universidad Carlos III de Madrid, Av. Universidad 30, E-28911 Leganés, Madrid, Spain. jsouto@ing.uc3m.es.
3
Department of Electronics Technology, Universidad Carlos III de Madrid, Av. Universidad 30, E-28911 Leganés, Madrid, Spain. dpoiana@ing.uc3m.es.
4
Department of Electronics Technology, Universidad Carlos III de Madrid, Av. Universidad 30, E-28911 Leganés, Madrid, Spain. pag@ing.uc3m.es.

Abstract

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

KEYWORDS:

dual optical frequency comb; dynamic measurements; fiber Bragg gratings; sensor interrogation; ultrasounds

Conflict of interest statement

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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