Simultaneous Measurement of Strain and Temperature by a Sawtooth Stressor-Assisted Highly Birefringent Fiber Bragg Grating

• Published in: Journal of lightwave technology Vol. 38; no. 7; pp. 2060 - 2066
• Main Authors: Guo, Kuikui, He, Jun, Shao, Laipeng, Xu, Gaixia, Wang, Yiping
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-04-2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Automation; Birefringence; Bragg gratings; fiber Bragg gratings; Fiber gratings; Fiber lasers; Fiber optics sensors; laser materials processing; Manufacturing engineering; Robotics; Sensitivity; Smart structures; Strain; Strain measurement; Temperature measurement; Temperature sensors
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2019.2959671

We propose and demonstrate a highly birefringent fiber Bragg grating (Hi-Bi FBG) fabricated for the simultaneous measurement of strain and temperature. A birefringence of up to 2.96 × 10 −4 was created in the FBG by inscribing a sawtooth stressor near the fiber core with femtosecond laser irradiation. This provides a method for measuring the strain and temperature simultaneously, using one Hi-Bi FBG with two parameters (i.e., the Bragg wavelength <inline-formula><tex-math notation="LaTeX">\lambda _{B}</tex-math></inline-formula> and the birefringence-induced wavelength difference <inline-formula><tex-math notation="LaTeX">\lambda _{D}</tex-math></inline-formula>). Such a sawtooth stressor-assisted Hi-Bi FBG exhibits strain sensitivities of 1.24 pm/μϵ in <inline-formula><tex-math notation="LaTeX">\lambda _{B}</tex-math></inline-formula> and 2.14 × 10 −2  pm/ μϵ in <inline-formula><tex-math notation="LaTeX">\lambda _{D}</tex-math></inline-formula>, and temperature sensitivities of 9.52 pm/°C in <inline-formula><tex-math notation="LaTeX">\lambda _{B}</tex-math></inline-formula> and 0.13 pm/°C in <inline-formula><tex-math notation="LaTeX">\lambda _{D}</tex-math></inline-formula>. Moreover, the proposed sawtooth stressor can significantly increase the sensitivities of the birefringence to the applied strain and temperature. The strain and temperature sensitivities in <inline-formula><tex-math notation="LaTeX">\lambda _{D}</tex-math></inline-formula> of the proposed sawtooth stressor-assisted Hi-Bi FBG are of several orders of magnitude, higher than those (i.e., 6.07 × 10 −5  pm/μϵ and 9.42 × 10 −3 pm/°C in <inline-formula><tex-math notation="LaTeX">\lambda _{D}</tex-math></inline-formula>) of a straight stressor-assisted Hi-Bi FBG. Consequently, the proposed sawtooth stressor-assisted Hi-Bi FBG sensors are promising in many areas, such as smart structures and intelligent robotics.