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

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 λ
_B
and the birefringence-induced wavelength difference λ
_D
). Such a sawtooth stressor-assisted Hi-Bi FBG exhibits strain sensitivities of 1.24 pm/με in λ
_B
and 2.14 × 10
^-2
pm/ με in λ
_D
, and temperature sensitivities of 9.52 pm/°C in λB and 0.13 pm/°C in λ
_D
. 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 λ
_D
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 λ
_D
) 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.