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In this work, a theoretical study was conducted on temperature sensing in Ge-Sb-Se multimode fibre Bragg grating (MM-FBG). The sensing characteristics of the designed MM-FBGs with different fibre parameters and operating wavelengths were calculated using a coupled model method. The temperature sensitivity of this MM-FBG was found to improve significantly by shifting the operating wavelength from telecom range to mid-infrared (MIR) and utilizing the wide transmission range of Ge-Sb-Se glasses. The temperature sensitivity of the proposed Ge-Sb-Se MM-FBG was calculated to be 0.0758 nm/°C at 1550 nm, which is 7.58 times higher than silica FBGs at 1550 nm, and the temperature sensitivity was calculated to be more than 0.16 nm/°C at 3390 nm, which is 2.2 times higher than that at 1550 nm. In addition, the proposed MM-FBGs provided multi-peak information, and the sensitivity of each peak was calculated to be comparable to the single-mode FBG. The proposed Ge-Sb-Se MM-FBG has great potential for temperature sensing in MIR because of its advantages of simple preparation, high coupling efficiency, multi-peak information and wide working window. [ABSTRACT FROM AUTHOR]

Fibers exhibiting flattened and decreasing dispersion are important in nonlinear applications. Such fibers are difficult to design, particularly in soft glass. In this work, we develop a preliminary design of a highly nonlinear tapered hybrid microstructured optical fiber (TH-MOF) with chalcogenide glass core and tellurite glass microstructure cladding. We then numerically studied its dispersion, loss, and nonlinearity-related optical properties under fundamental mode systematically using the infinitesimal method. The designed TH-MOF exhibits low chromatic dispersion that is similar to a convex function with two zero-dispersion wavelengths and decreases with fiber length from 2 to 5 μm band. The potential use of the TH-MOF in nonlinear applications is demonstrated numerically by a supercontinuum spectrum of 20 dB bandwidth covering 1.96–4.76 μm generated in 2-cm-long TH-MOF using near 3.25-μm fs-laser pump. [ABSTRACT FROM PUBLISHER]