Slanted multimode fiber gratings and applications

Abstract

In this paper, we investigated in detail the characteristics of slanted multimode fiber Bragg gratings (MFBGs) both theoretically and experimentally. Our analysis clearly revealed the significant effect of slanted angels on the transmission spectra and the characteristics of MFBGs. On a 2° slanted MFBG, both experimental and theoretical results showed that the strain and temperature sensitivities were almost the same for different transmission dips. Utilizing this property, switchable and tunable multi-wavelength fiber ring lasers were realized. The configurations were simple and multipurpose. Our results showed that the lasers can generate single-, dual-, three-, four-, and five- wavelength lasing; and a 4.2 nm continuous wavelength tuning range was achieved. On a 3° slanted MFBG, a novel and simple sensor was developed for simultaneous temperature and refractive index measurement. The 3° slanted MFBG showed two wavelength groups in its transmission spectrum: one group, due to the coupling from one core mode to cladding modes, was sensitive to both surrounding refractive index (SRI) and temperature, and, the other, due to the coupling from one core mode to other core modes, was sensitive only to temperature. Utilizing this property, two parameters can be distinguished and measured simultaneously using one slanted MFBG.