Wideband Tunable Erbium-Doped Fiber Ring Laser Using Switchable Parallel Fiber Bragg Gratings
Jianling Yang, Swee Chuan Tjin and Nam Quoc Ngo
A wideband wavelength tunable Erbium-doped fiber laser using a unidirectional traveling-wave fiber ring combined with a novel switchable fiber Bragg grating (FBG) array is presented. The switchable FBG array consists of a 1×3 optical switch and three parallel discrete FBGs. The central reflection wavelengths of these three discrete FBGs are 1534 nm, 1549.15 nm and 1559.4 nm, respectively. The corresponding reflectivities are 90%, 99% and 99.8%, respectively. The wavelength of each grating can be continuously tuned in a range of over 16 nm by stretching (7 nm) and compressing (8 nm) the FBG. Therefore a fiber ring laser with a very large wavelength tuning range has been successfully demonstrated. In our experiment, the wavelength tuning range of the Erbium-doped fiber ring laser is 38 nm, from 1527 nm to 1565 nm. Within this tuning range, the total output power is about 7-8 dBm, the 3-dB linewidth is 0.01 nm, and the side mode suppression ratio is more than 48 dB. This tunable fiber ring laser can also work in the mode-locking mode when an amplitude modulator is inserted in the cavity. By applying the driving frequency matching the round-trip frequency or its multiples to the modulator, active mode-locking is realized. The highest harmonic order achieved is 125, the repetition rate and pulse-width of the mode-locked pulses are 1.00475 GHz and 539 ps, respectively.