Fiber Bragg Grating Fabry-Pérot Cavity Continuous Wave And Q-switching Laser

Er-doped fiber Bragg grating(FBG) laser has attracted considerable interests for its potential applications in wavelength division multiplex optical communication systems, spectroscopy, fiber optic sensing, optical generation of microwave and millimeter waves and other fields. Fiber grating Fabry-Perot cavity continuous wave and Q switching fiber lasers are proposed and experimentally demonstrated with emphases on CW single- and dual-wavelength fiber lasers, Q-switched Er-doped fiber laser, the transform limits of Lorentz and super-Gaussian rectangular line-shape ultrashort pulse laser and temporal coherence, effect of fiber nonlinearity, and application of FBG laser in temperature sensing and optical generation of microwave and millimeter wave signals, etc. The major and innovation work is as following.1. The propagating characteristics of FBG and cascaded FBGs are investigated theoretically by using coupled mode theory and system analysis method and demonstrated experimentally. An analytical method to deal with a nonlinear FBG Fabry-Perot(FP) cavity is proposed by introducing a nonlinear phase term in the transmission function of FBG FP cavity. The effects of different parameters of nonlinear FBG-FP cavity on the optical bistability behaviors are investigated. The FBG laser is modelled by using rate equation theory. It shows that the Bragg wavelengths of two FBGs at different operation temperature are different, their propagating functions modulate each other, two reflect peak values can be observed at minor wavelength mismatch. When two FBGs with different operation temperature sre used as laser cavity mirrors, dual-wavelength lasing can be achieved.2. A novel Er-Yb co-doped fiber grating laser using two fiber gratings as cavity mirrors is proposed, its output and temperature performance are experimental demonstrated, the spontaneous spectrum of Er-Yb co-doped fiber and transmission spectrum of fiber grating are given, and the effect of the operation temperature of fiber grating on the central wavelength of laser is discussed.3. A novel dual-wavelength fiber laser with asymmetric fiber Bragg grating(FBG) Fabry-Perot(FP) cavity is proposed and experimentally demonstrated. The fiber laser uses a couple of uniform FBGs as the cavity mirrors, and the third FBG is used as intracavity wavelength selector by changing its operation temperature. Experiment shows that by adjusting the operation temperature of the intracavity wavelength selector, a tunable dual-wavelength laser emission can be achieved.4. A linear-cavity passively Q-switched Bragg fiber grating Er-doped fiber laser using a semiconductor saturable absorber mirror (SESAM) is proposed and demonstrated experimentally, which does not use polarization controller to control the polarization state of laser and simplify the structure of passively Q-switched Bragg fiber grating Er-doped fiber laser. Q-switching is observed with the output power produced at a slope efficiency of 1.2% with respect to the absorbed pump power, the central wavelength is 1549.975nm, and the threshold power is 143mW. The pulse repetition frequency obtained can be turned from 5.431 kHz to 9.778 kHz. The pulse energy of 0.128nJ has been obtained at the pump power of 155mW, and the pulse width is 40μs with repetition frequency of 6.538 kHz.5. The transform limits of Lorentz and super-Gaussian rectangular line-shape ultrashort pulse laser are calculated by using Fourier transform method. It demonstrates that the transform limits of Lorentz and super-Gaussian rectangular line-shape ultrashort pulse are 0.221 and 0.443, respectively. The results obtained can be used to analyze the actual Lorentz and super-Gaussian rectangular line-shape ultrashort pulses. According to coherence theory and Mandel’ definition of coherence time, the analytical expressions for the complex degree of temporal coherence and coherence time of chirped Gaussian pulses are derived. The relations can be expressed as a function of the laser’s chirp factor C and delay factor τ, the phase of complex degree of temporal coherence is not zero, and the influence of the laser’s chirp factor is investigated. Finally, obtained the coherence time-bandwidth product for chirped Gaussian pulses.6. A temperature sensor based on FBG laser is reported, the analytical expression for the shift of the Bragg wavelength with temperature is derived, the effect of operation temperature of fiber Bragg grating on the central wavelength of fiber Bragg grating laser is discussed experimentally. The result demonstrates that the central wavelength of laser is a function of the operation temperature of FBG, and the temperature coefficient of the fiber Bragg grating is 1.27×10-5/℃. Secondly, we report and demonstrate the technical feasibility of a novel optical generation of microwave and millimeter wave signals by using asymmetric fiber Bragg grating Fabry-Perot cavity fiber laser, dual-wavelength emission can be achieved with wavelength separation of 0.68nm corresponding to the millimeter wave signal at 85GHz. By appropriately adjusting the operation temperature of intracavity fiber Bragg grating, the frequency of millimeter wave signal generated can be tunable.