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Investigation Of Novel Narrow Linewidth Fiber Laser And Fiber Sensor

Posted on:2017-03-28Degree:DoctorType:Dissertation
Country:ChinaCandidate:B YinFull Text:PDF
GTID:1108330485960330Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
As one of the most important components of optical fiber technology, fiber grating has been experiencing an active and fast development, numerous applications of which have been extended to optical fiber based sensing and laser areas. For one thing, the fiber gratings based sensors are compact, flexible and free of electromagnetic interference, making state-of-art sensing technology with multiple functions as well as high integration density. For another, single-longitudinal-mode(SLM) narrow linewidth fiber laser can be exploited for a wide range of intriguing applications, such as coherent communication, laser intensity direction and ranging (LIDAR), Terahertz sources and so on. In this work, fiber gratings with several different structures are systematically investigated with both theory and experimental characterization. The proposed fiber gratings are applied for sensing and laser applications. By using the home-made Erbium doped optical fiber, different kinds of cavity based Erbium doped fiber lasers are studied theoretically and experimentally. The highlights of this work are summarized as follow:1. Spectral characteristics and the filtering properties of fiber grating are analyzed by the coupled-mode theory. Analytical models for the tapered (cases including a single-mode(SM) and a polarization-maintaining(PM) chirped fiber gratings are proposed by the transfer matrix method. The tapered chirp fiber gratings(SM and PM) corresponding spectral and filtering characteristics are intensively analyzed with both theory and measurements. The effects of grating’s parameters and taper’s parameters on spectral and filtering characteristics are discussed. An attenuation factor caused by tapering is introduced to modify the analytical models. Additionally, the influences of the polarization state of the tapered PM chirp fiber gratings on spectral and filtering characteristics are studied.2. A 2D spatial position sensing system based on a series of uniform fiber gratings is demonstrated. The principle relies on axial stress sensor using fiber grating, as the resonant wavelength of fiber grating can be modulated by stress. Intensity of the designed resonant wavelength would be varied with the different position of stress by OSA.3. Based on the PM tapered chirp fiber grating as well as PM long period fiber grating, a multi-functional sensor is proposed and experimentally realized. For the PM tapered chirp fiber grating, the effects of external perturbations (including strain, temperature and twist) on transmission peaks and depths of polarized states are carefully investigated, achieving a multi-functional optical fiber sensor. For PM long period fiber grating, the transmission peaks and depths of coupling between core mode and different higher order modes in cladding are studied. Moreover, the influences of external perturbations (including temperature, refractive index and twist) on transmission peaks and depths of polarized states of the proposed PM tapered long period fiber grating are investigated. It is concluded that the sensors with two configurations introduced above can measure strain, temperature and twist in the meanwhile.4. According to the theory of tapered chirp fiber grating, the linear-cavity SLM narrow linewidth fiber laser based on the fiber filter and a saturable absorber is proposed. The single wavelength output is achieved by the narrow fiber filter and the saturable absorber, and the Lorentz fitted 20dB linewidth is around 27.7kHz. Further, according to the theory of the tapered PM chirped fiber grating, a tunable dual-wavelength ring-cavity fiber laser based on the fiber filter and a saturable absorber is proposed based on tapered chirp fiber grating with two narrow transmission band.The SLM narrow linewidth laser output is achieved. The working principle of the self-injection locking technology is theoretically and experimentally studied. A SLM narrow linewidth DFB fiber laser based on tapered fiber grating and the hydrogen-loaded heavy concentration Erbium doped optical fiber. In order to improve the quality of output laser, the self-injection locking method is applied here. Furthermore, considering the laser is associated with the self-injection locking method, the 20dB linewidth is nearly 10.3kHz by the delay self-heterodyne method; otherwise, the value of 20dB bandwidth increases to 52.3kHz.5. The spectral and filtering characters of fiber grating based single-or multi-cavity Fabry-Perot(F-P) filters are analyzing. And different producing filter in the experiment are contrasted. From the theory of multi-cavity F-P filter based on PM uniform fiber grating, a switchable dual-wavelength SLM narrow linewidth ring fiber laser is proposed. Additionally, results show the Lorentz fitted 20dB bandwidths of laser outputs are 4.8kHz and 4.5kHz. Further, the spectral and filtering characters of chirped fiber grating based single- or multi-cavity F-P filters are analyzing by the transfer matrix method. Benefit from the polarization dependency of ultra-narrow filtering properties of PM chirp fiber grating base single-cavity F-P filter, a tunable or switchable dual-wavelength SLM narrow linewidth ring fiber laser at room temperature is demonstrated. The measured results show the 20dB bandwidths of two output wavelengths are 16.9kHz and 17.1kHz, respectively, corresponding to the 3dB linewidth about 0.845kHz and 0.855kHz.
Keywords/Search Tags:Fiber Bragg grating, F-P resonant cavity, Polarization-maintaining fiber, Narrow linewidth fiber laser, fiber sensor
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