Studies on strain and temperature characteristics of a slanted multimode fiber Bragg grating and its application in multiwavelength fiber Raman ring laser

Detailed strain and temperature characteristics of a 2° slanted multimode fiber Bragg grating (MFBG) are developed theoretically and observed experimentally. Results show that the strain and temperature sensitivities are almost the same for different transmission dips of the 2° slanted MFBG. Utilizing two characteristics of the 2° slanted MFBG, namely 1) resonant wavelength intensities strongly affected by excited mode propagating before the grating and 2) uniform strain sensitivities of different resonant wavelengths, a switchable and tunable multiwavelength fiber Raman ring laser is realized. The configuration is simple and multipurpose. Results show that the laser can generate single-, dual-, three-, four-, and five-wavelength lasing by switching between each operation if a mode scrambler (MS) that is inserted in front of the slanted MFBG is adjusted; furthermore, a 4.2-nm continuous wavelength-tuning range is achieved by straining the slanted MFBG when the MS is fixed.