Tunable and switchable six-wavelength erbium-doped fiber ring laser

A tunable and switchable six-wavelength erbium-doped fiber ring laser based on a fiber Bragg grating based FP filter (FBG-FPF) and a polarization-maintaining fiber Sagnac loop (PMFSL) is proposed and demonstrated experimentally at room temperature. The FBG-FPF with low insertion loss is used to generate dense multiwavelength output. The PMFSL acts as a comb filter and frequency stabilizer. Through adjusting the squeezed fiber polarization controllers, six kinds of single-wavelength with the tunable range of 11 nm, eleven kinds of dual-wavelength, three kinds of triple-wavelength and one kind of six-wavelength can be obtained and switched with one another. All lasing lines with 3 dB linewidth of less than 0.29 nm and optical signal-to-noise ratio of more than 22 dB locate in the range of C- and L-bands of the optical communication waveband.