Dual-wavelength Erbium-doped Fiber Laser Based On Fiber Bragg Grating Linear Cavity And Its Applications

Fiber Bragg grating dual-wavelength erbium-doped fiber laser, with the advantages of low threshold, wide gain bandwidth, narrow linewidth, wide tuning range, simple and compact structure, has broad application prospects in the field of optic communication and fiber sensing. In this dissertation, A tunable dual-wavelength fiber laser using an external-injected DFB laser and asymmetric fiber Bragg grating Fabry-Perot cavity is proposed and experimentally demonstrated, and the applications of a dual-wavelength fiber laser in generation of tunable microwave/millimeter waves and temperature sensor are presented. The main contents are outlined as follow:1. the undetermined coefficient function of the erbium-doped fiber ASE spectrum is theoretically derived by the Atomic semi-classical theory. The ASE spectrum of a 25cm length erbium-doped fiber pumped by 980nm LD is measured, and the empirical formula of the ASE spectrum of the erbium-doped fiber is obtained by using the the L-M Algorithm and least square method. It is demonstrated that the ASE spectrum of the erbium-doped fiber has two peak wavelength of 1530.951nm and 1555.964nm. The Good of Fit (R-square) of 0.98072 and the residual sum of squares of 4.44769×10-9 are achieved.2. The transmission characteristics of the fiber Bragg grating is researched. The function of fiber grating transmission spectrum is derived by the couple-mode theory. The numerical simulation of fiber grating transmission spectrum function is carried out by matlab. Erbium-doped fiber amplified spontaneous emission spectrum, serving as a light source, was launched into the cascaded fiber Bragg gratings, and the transmission spectrum of cascaded fiber Bragg gratings is achieved. When the working temperature of FBG is changing, the change of cascaded fiber Bragg gratings transmission spectrum is analyzed. The spacing of transmission spectrum center wavelength showed a good linear relationship with the working temperature of FBG. and the temperature coefficient of 1.27×10-5/℃ is calculated out.3. A tunable dual-wavelength fiber Bragg grating laser using an external-injected DFB laser proposed and experimentally demonstrated. A DFB laser used as the injection laser is injected into the fiber Bragg grating cavity, a piece of highly Er-doped fiber (EDF) with length of-25 cm placed in the cavity is used as the gain medium. The wavelength spacing can be tuned by adjusting the operation temperature of the DFB laser. When the DFB works at 25℃, a dual-wavelength simultaneous oscillation at 1 549.67nm and 1553.44nm with wavelength spacing of 3.77nm is achieved.4. A switchable dual-wavelength fiber laser based on asymmetric fiber Bragg grating Fabry-Perot cavity with a SESAM is proposed and experimentally demonstrated. a couple of identical uniform FBGs are used as the cavity mirrors, and the third uniform FBG is used as intracavity wavelength selector by changing its operation temperature. the Q-switching mechanism is that the SESAM is used as a saturable absorber to adjust the losses of oscillating modes in the cavity. Keeping the two identical uniform FBGs at the same temperature of 35℃, and changing the operation temperature of the third FBG, a dual-wavelength simultaneous oscillation at 1549.488nm and 1549.960nm with wavelength spacing of 0.472nm is achieved.5. Based on the dual-wavelength Er-doped fiber laser with asymmetric fiber Bragg grating Fabry-Perot cavity, a novel photonic tunable microwave generation is proposed and experimental demonstrated. By changing the operation temperature of the fiber Bragg grating,stable dual-wavelength pulse with tunable wavelength spacing are achieved, and wavelength spacing of 0.354-0.472mn, corresponding to millimeter wave signals of 42.3-59.1 GHz can be obtained at the photo detector. Meanwhile, temperature sensor based on DFBL injection dual-wavelength fiber laser with wavelength and temporal domain demodulation is proposed and demonstrated experimentally. If the temperature sensor is demodulated by the spacing of dual-wavelength, he temperature coefficient of the DFB laser is 7.2×10-5/℃. If the temperature sensor is demodulated by the ring-down time in time domain, the temperature coefficient of the FBG is 1.75×10-7 /℃.