Multi-wavelength linear-cavity tunable fiber laser using a chirped fiber Bragg grating and a few-mode fiber Bragg grating.

A novel and simple multi-wavelength linear-cavity tunable fiber laser source using a chirped fiber Bragg grating (CFBG) and a few-mode fiber Bragg grating (FMFG) is demonstrated using erbium-doped fiber (EDF) as the gain medium. In our linear-cavity configuration, the FMFG acts as full-reflecting mirror and wavelength selector while the CFBG with the 3-dB bandwidth of over 30 nm acts as a broadband partially reflecting mirror. The number of lasing wavelengths can be controlled by changing the state of polarization inside the cavity using a polarization controller. The large bandwidth of the CFBG enables continuous tuning of the lasing wavelengths by application of mechanical strain or thermal heating on the FMFG.