Investigation On Fiber Bragg Grating & Widely Tunable Erbium-Doped Fiber Laser

Today, our society has gone into an age of information. Optical fiber has been widely used as the most important transmission medium in the telecommunication networks. Various optical fiber devices have been developed, which greatly enhance the flexibility of the network. In this thesis, fiber Bragg grating (FBG) and Erbium-doped fiber laser (EDFL), being important passive and active fiber devices, have been investigated theoretically and experimentally. Tuning techniques for FBG wavelength and bandwidth have been studied and developed. Widely tunable EDFL within the C-band and L- band has been achieved both in ring and linear cavities. The output characteristics as functions of several cavity parameters have been studied. The main contents are listed as follows.1. The characteristics of FBG have been studied by means of the coupled-mode theory and the transfer matrix approach. Reflectivity and dispersion of several types of FBG, such as uniform period FBG, adapted FBG, phase-shifted FBG, and phase-shifted chirped FBG have been demonstrated by numerical modeling.2. The principles and techniques of the wavelength tuning of FBG have been studied. Electrical techniques by using a metal tube and Aluminum vacuum coating have been proposed. High tuning rate of 2.1×10-3nm/(mA)2 has been obtained. Furthermore, this technique has successfully been used to change the mode of a FBG external cavity semiconductor laser, resulting in choosing of a laser wavelength electrically among six modes that cover 5nm range.3. For the first time, a temperature-compensated FBG displacement sensor based on cantilever beam structure has been demonstrated. The cantilever was formed by sticking one end of a polymer beam onto an aluminum baseplate. By attaching a FBG orthogonally on the joint section, displacement of the beam's end and temperature can been measured simultaneously due to the different responses of the two FBG. Sections. Resolutions of the sensor, limited by the spectral resolution of the optical spectral analyzer (0.1nm), are 0.08mm and 3.1°C (in the case of no displacement, it will be 0.73°C). A maximum range of 10.5mm has been achieved without any damage to the FBG.4. For the first time, a linear chirping technique for FBG without center wavelength...