Control of Excitation of Cladding Modes by Tapering an Insertion of Special Fiber

Abstract

A method for controlling the excitation of cladding modes by tapering special fiber insertions made of SM450 and coreless fibers is proposed. The coupling coefficients between the core mode and the cladding modes of the tapered fiber insertion are calculated. For the calculation, changes in the effective refractive indices and phases of the fiber core and in the cladding modes upon tapering are found. The field distribution of the core mode of the standard fiber transmitted through fiber insertion is obtained. The transmission characteristics of insertions of SM450 and coreless fibers during tapering are simulated and compared with the experiment. The possibility of controlling the transmission and excitation of various cladding modes is confirmed experimentally.

A Review of Sensitivity Enhancement in Interferometer-Based Fiber Sensors

“…High-order modes are usually more sensitive to the change of the surrounding environment and the excitation of high-order cladding modes can be controlled by changing the waveguide structure such as tapering single-mode fibers and coreless fibers [ 74 ]. A fiber refractometer based on a tapered multimode fiber between two single-mode fibers was proposed with a sensitivity better than 1900 nm/RIU [ 75 ].…”

High Sensitivity Fiber Interferometric Strain Sensors Based on Elongated Fiber Abrupt Tapers

“…On the other hand, a longer interaction length is also advantageous to improve the strain sensitivity. To date, there have been various kinds of excitation methods proposed to excite the high-order core or cladding modes based on blaze gratings, long-period gratings (LPFG), core mismatched splicing, fiber Bragg grating (FBG), abrupt tapering, up tapering [ 18 , 19 ], and so on. As a strain sensor, LPFG has high sensitivity and low back reflection, but it may block the spectral response due to its high bending sensitivity [ 20 ].…”