Femtosecond Laser Inscribed Multiwavelength Cascaded FBG Array Using Point‐By‐Point Method for Temperature Sensing Based on Swept Laser Demodulation Technique

A femtosecond laser inscribed quintuple‐wavelength cascaded fiber Bragg grating (FBG) array for temperature sensing system based on swept laser source was proposed and experimentally demonstrated. In the proposed system, five cascaded 2‐mm length FBGs were inscribed using the point‐by‐point method with a grating spacing of 2 cm through fiber acrylate coating. In addition, the demodulator based on swept modulated grating Y‐branch (MG‐Y) laser source was constructed. In the experiment, the FBG array was hold on temperature platform for heating and cooling test during 30∼90°C range, and sensitivity was more than 8.9 pm/°C with a linearity of 0.989.