Dual-Polarization Distributed Feedback Fiber Laser Sensor Based on Femtosecond Laser-Inscribed In-Fiber Stressors for Simultaneous Strain and Temperature Measurements

• Published in: IEEE access Vol. 8; pp. 97823 - 97829
• Main Authors: Guo, Kuikui, He, Jun, Xu, Gaixia, Wang, Yiping
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Automation; Axial strain; Beat frequencies; Birefringence; Bragg gratings; Cladding; Doped fibers; Dual polarization (waves); Erbium; Erbium-doped fiber lasers; Feedback; Fiber gratings; Fiber lasers; Infrared lasers; Laser beams; Lasers; Manufacturing engineering; Optical fiber polarization; Optical fiber sensors; Orthogonality; Polarization; Robotics; Sensors; Smart structures; Strain; Temperature measurement; Temperature sensors; Ultraviolet lasers
• DOI: 10.1109/ACCESS.2020.2997918
• ISSN: 2169-3536

We propose and experimentally demonstrate a novel dual-polarization distributed feedback fiber laser (DFB-FL) sensor based on femtosecond laser-inscribed in-fiber stressors. The resonant cavity of the DFB-FL sensor consists of a phase-shifted fiber Bragg grating (PS-FBG) in the fiber core of a section of heavily erbium-doped fiber (EDF), together with two stressors in the fiber cladding around the PS-FBG. The PS-FBG was fabricated by means of a scanning UV laser beam and shielded phase mask technique. The two in-fiber stressors, i.e. a sawtooth stressor and a straight stressor, were directly inscribed at two orthogonal planes in the EDF cladding using a near-infrared femtosecond laser. The two stressors could precisely adjust the fiber birefringence in the laser cavity, and hence the DFB-FL sensor can operate in two polarization modes. Moreover, simultaneous measurement of axial strain and temperature was demonstrated by detecting the polarization beat frequency <inline-formula> <tex-math notation="LaTeX">\nu _{\mathrm {B}} </tex-math></inline-formula> and lasing wavelength <inline-formula> <tex-math notation="LaTeX">\lambda </tex-math></inline-formula> of the dual-polarization DFB-FL sensor. Experimental results exhibit strain sensitivities of 34.5 kHz/<inline-formula> <tex-math notation="LaTeX">\mu \varepsilon </tex-math></inline-formula>, 1.25 pm/<inline-formula> <tex-math notation="LaTeX">\mu \varepsilon </tex-math></inline-formula> and temperature sensitivities of 684.6 kHz/°C, 11.5 pm/°C, respectively. As such, the proposed dual-polarization DFB-FL sensor could be used for simultaneous strain and temperature measurements, and hence is promising for application in many areas, such as smart structures and intelligent robotics.