Experimental and numerical study on refractive index sensors based on fibre Bragg gratings inscribed in multimode fibre

Abstract

In this work is reported the experimental and numerical results of the refractive index response of etched fibre Bragg gratings written in a graded index multimode fibre. The responses of the modes coupled by the grating inscribed in a multimode fibre are compared with the mode coupled by a grating inscribed in single mode fibre. The results of this study show that the refractive index sensitivity and the dynamical range of etched fibre Bragg gratings written in multimode fibres are higher than the ones verified in single-mode fibres. The determination of oil-biodiesel blend concentrations are also compared as an example of practical applications. It is shown that a greater core diameter of the multimode fibre enables the Bragg gratings to exhibit enhanced sensitivity without requiring further fibre diameter reduction.

A Comprehensive Review of Optical Fiber Refractometers: Toward a Standard Comparative Criterion

“…Moreover, in ref. [], it is proved that it is possible to get an improved sensitivity to the SRI with a smaller reduction of the multimode fiber (MMF) diameter when compared with FBGs inscribed in single‐mode fiber (SMF), providing a mechanical robustness improvement for the sensor. This conclusion is important since nearly all research is being devoted to SMF fiber.…”

Long-Period Grating Based Coupler for Multi-Core Fiber Systems

“…We expect that the etching process will produce a final SMF radius whose experimental error will be less than 0.5 µm [24]. To take into account this error, we calculated the modes power evolution along the proposed SMF to MCF coupler for three cases, the best scenario found (r SMF = 46.3 µm) and the ones for which the SMF cladding radius was 0.5 µm below and above the selected SMF cladding radius (45.8 µm and 46.8 µm).…”

“…Reducing the cladding radius may lead to a higher similarity, in terms of the propagation constants, between modes of different fibers and also enhance the evanescent field of the cladding modes [9], which may increase the coupling between fibers and decrease the coupling distance. Experimentally, this reduction can be achieved by chemical attack of the fiber [24]. We have considered only the reduction of the cladding of the SMF, because the SMF core is farther from the exterior than the cores in the MCF, which makes its mode less affected by the cladding reduction.…”

A plastic optic fiber sensor with temperature compensation for glucose concentration measurement

“…Among the variously existent concentration sensors, optical fiber sensors have gained popularity due to their high stability, free from electromagnetic interference, high repeatability and sensitivity, multiplexing, and rapid response. So far, researchers have developed a variety of fiber optic concentration sensors, including interferometer structures [1-3], fiber grating structures [4][5], and surface plasmon resonance (SPR) structures [6][7]. All of the sensors with the structures mentioned above performed great in terms of concentration sensing.…”