Four-channel high-speed strain measurement based on VT-DBR laser

Wavelength-shifting interferometry (WSI) based technology enables simultaneous high-speed demodulation of four channels of strain sensors. The four sensors are based on extrinsic Fabry-Perot interferometry (EFPI), which are constructed by splicing a section of hollow-core fiber (HCF) of about 500µm between two single-mode fiber (SMF) segments. Each sensor corresponds to one demodulation channel. We use a vernier-turned distributed Bragg reflector (VT-DBR) laser for high-speed wavelength switching, which introduces a phase shift in the wavelength domain. Based on five-step phase-shifting algorithm, phase recovery is performed with any five adjacent phase-shifting signal to achieve high-speed and stable phase demodulation. Experimental results show that this measurement system can be well applied to high-speed measurement of strain.