Optimization of C-Band Erbium Doped Distributed Feedback Fiber Laser

<p>Distributed Feedback fiber lasers (DFB FL) are robust narrow linewidth laser sources with its signal generated in optical fiber and can be delivered across a substantial distance through the fiber. Moreover, DFB fiber lasers are relatively small and thus much easier to implement in many transducers. These advantages make DFB excellent for high accuracy sensing of pressure, temperature, and other physical parameters, as the narrow linewidth of DFB fiber lasers allows for high precision measurements. DFB fiber lasers are widely used in many important applications such as high precision meteorology, gravitational wave detection, and coherent LIDAR. These characteristics and applications have made DFB fiber lasers an important topic for research and development. The goal of this research is to improve the performance of DFB fiber lasers. The parameters in focus are the slope efficiency, linewidth, noise spectrum, and the stability of the emission wavelength to temperature variation. A passive athermal compensation package was also designed to stabilize the lasing wavelength with fluctuating temperatures, as well as to reduce the relative intensity noise (RIN). Implementation of these improvements will be discussed in this thesis to make linewidth narrower, RIN noise lower, and lasing wavelength insensitive to thermal fluctuations in normal operation. The measurement techniques for the laser linewidth and RIN etc. will be presented. Many DFB lasers were fabricated and tested. Among them, an Erbium doped fiber laser was made which operates at 1550 nm, with an approximate 1 kHz linewidth at -3 dB. This narrow linewidth was achieved with the use of an asymmetrical double super-Gaussian apodization mask to write the œÄ-phase shifted grating for the DFB. The asymmetrical double super-Gaussian mask also lets almost all the power to be emitted from only one end of the fiber cavity. The passive thermal compensation package decreased the Shot-noise floor of the RIN spectrum down to -150 dB/Hz from -140 dB/Hz. The slope efficiency of the laser almost doubled in comparison with the DFBs apodized with a single Gaussian profile. The thermal compensation packaging improved the emitting wavelength stability under varying temperatures by a factor of 14 from 9.8 pm/°C down to 0.69 pm/°C. The improvements proposed in this thesis can be applied to the DFB fiber lasers made with other gain fibers such as with Yb-doped and Tm-doped fibers.</p>