Mode Locking Pulse Fiber Laser And Its Application In Optical Sensing And Optical Microwave Generation

Active mode locking fiber laser (AMLFL) is one of the most important technologies in high-speed optical communications because of its ability to generate ultra-short optical pulse source. Fourier domain mode locking (FDML) has been demonstrated to provide swept source laser without speed limitations. This thesis focuses on research of mode locking fiber laser technologies and their application in photonic generation of microwaves and optical sensing system. Experimental research on channel coding is also demonstrated in order to improve information transmission performance in optical communication systems.To begin with, we introduce and summaize the history and the development trend of ultra-short pulse generation, mode-locked fiber lasers, and applications of mode-locked fiber lasers..Then, the principles of AMLFL and FDML fiber laser are investigated. Besides, the generation of short pulse in the AMLFL cavity is theoretically analyzed and the principle of FDML fiber laser’s application in optical sensing system is generally introduced.Following, the technologies for pulse equalization, compression and shaping are discussed based on the studies of AMLFL. Pulse equalization is realized based on a rational harmonic mode-locked (RHML) fiber laser incorporating a Mach-Zehnder interferometer (MZI) filter to effectively suppress the low-order harmonics. Pulse compressor which consists of comb-loke dispersion-profiled fiber (CDPF) and Raman gain media is introduced and experimentally analyzed to realize a compression-factor-controllable optical pulse compressor. A novel all-fiber dynamic method for pulse shaping using a fiber loop based circulating structure is first time presented.Subsequently, AMLFL’s application in optical microwave generation is investigated and several different approaches based on fiber lasers are proposed to obtain microwaves in the optical domain. A simple and stable approach to generate high-purity microwave signals based on a rational harmonic mode-locked fiber laser is achieved by incorporating an external cavity Mach-Zehnder interferometer filter. By using a fiber loop based photonic processing structure, we experimentally generate a high linearity and fast fall time sawtooth pulse train at a tunable repetition rate. By utilizing the microwave photonic filter technique, optical generation of microwave signal is achieved based on an AMLFL. Moreover, we use a compound-cavity multiwavelength Brillouin erbium fiber laser incorporating a fiber Bragg grating filter to select the desired Stokes signal and beat it with the optical carrier at a photodetector to obtain frequency-switchable microwaves.Furthermore, FDML fiber laser’s application in optical sensing system is developed. The principle of spectrum-limited FDML fiber laser is investigated. The ultra-long-distance FBG sensor system using a Raman amplifier based on a SL-FDML fiber laser is proposed for the first time and strain sensing based on such an ultra-long distance FBG sensor system is demonstrated. Meanwhile, we develop a quasi-distributed FBG sensor system based on this FDML fiber laser.Finally, we introduce another key technology in optical transmission system named channel coding. We experimentally evaluate the BER performance of a nonbinary LDPC-coded modulation scheme against that of the corresponding conventional (binary) LDPC-coded scheme and demonstrate the superiority of the former in terms of net coding gain.This experimental research-based thesis, supplemented by theoretical simulation research, aims to realize technical programs of mode locking fibe lasers and their application. I believe that encouraging results in this thesis will stir further interest on mode locking fiber laser and its application for current and future high-speed optical communications.