Cascaded Optical Fiber Sensor Based on Efpi and Few-Mode Fiber Mzi for Simultaneous Measurement of Ultraviolet Light Intensity and Temperature

A new cascaded optical fiber sensor, which can measure Ultraviolet Light Intensity and Temperature simultaneously was designed and verified by experiment, which consists of an extrinsic Fabry-Perot interferometer (EFPI) with benzocyclobutene (BCB) and a few-mode fiber Mach Zehnder interferometer (MZI). By performing a Fourier transform and applying a frequency domainband-pass filter, the polymer-EFPI and few-mode fiber MZI spectra were separated from superimposed spectra of cascaded structure. The sensing characteristics of temperature and ultraviolet (UV) light intensity were tested and analyzed in detailed, respectively. By constructing a sensitivity matrix, the distinction between UV light intensity and temperature in the proposed hybrid sensor was resolved. The UV light intensity and temperature sensitivities are 0.0035nm/ (mW/cm2) and 0.2122nm/°C, respectively. In addition, the cascaded structure is insensitive to the change of ambient refractive index (RI), which can effectively avoid the cross-interference of RI.