Characteristics of electric field from a coupled mode inside an optical fiber under perturbation by three-dimensional (3D) printed long-period fiber grating (LPFG) device have been observed in this work by the experiment and simulation. The various periodic index differences referring to the weights of perturbation by 3D printed LPFG device are applied on the single-mode fiber. The experimental results show that the resonant wavelength shift is a linear function of the grating period with the maximum coefficient of determination R2 of 0.9995. Some of resonant wavelengths are chosen to run simulations to investigate the electric field distribution. The scattering direction of the electric field states the magnitude of leaking optical power when the light transmits through the grating region applied to the single-mode fiber. Both the experimental and simulation results demonstrate that our proposed scheme can usefully be applied to selective tunable filters, intruder sensors, etc.

The rectangular-structured resin with one of its triangular long-period fiber grating surface is designed and printed out by using a high resolution 3D printer, so called long-period fiber grating (LPFG) resin. This LPFG resin is directly pressed on the bare single-mode fiber by a digital force meter to filter out partial band of light inside the fiber. The grating period is expanded by tilting the resin from the initial fiber axis. The optical filter is observed as resonant wavelengths from the broadband wavelength. The results show that the resonant wavelength shift is a linear function of the grating period with the coefficient of determination over 0.99. The proposed scheme has a great potential to be employed as a sensor such as a selective optical filter and a buried intrusion sensor.

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