Studies On Multi-wavelength Fiber Laser And External Electrical Tuning

Multi-wavelength fiber lasers are widely used in front areas, such as fiber optical communication, fiber optical sensor, microwave photonics. A multi-wavelength fiber laser based on semiconductor optical amplifier (SOA) is ulteriorly optimized on aspects of linewidth-narrowed and output power-equalized in this thesis. Meanwhile, a novel mechanism of external electrical tuning for multi-wavelength fiber laser is proposed. The preliminary theories and experiment studies on the wavelength tuning technology are carried on. The main contents are summarized as follows:1. The theory studies on multi-wavelength fiber laser.1) A basic mathematical model for the multi-wavelength fiber laser is constructed. The steady-state output results with different injected currents of SOA are numerical simulated by the segmentation model of the SOA's active area.2) The comb filter and linewidth-narrowed mechanism with un-pumped EDF are theoretically analysed. The methods to measure linewidth of single and multi longitudinal mode lasers are demonstrated.3) Power-equalized mechanisms with passive optiacal feedback and active optival feedback are discussed respectively.2. The experiment investigations on multi-wavelength fiber laser.1) Narrow linewidth F-P filter and a high birefringence fiber loop mirror (Hi-Bi FLM) are used as the filtering devices in the multi-wavelength fiber laser. The differences between them are compared.2) Different lengths of un-pumped EDF are used as the linewidth-narrowed mechanism in the multi-wavelength fiber laser. The laser linewidth is narrowed to 199MHz using this mechanism.3) The passive-feedback mechanism, active-feedback mechanism and cascaded SOAs technique are proposed to improve the output channel power equalization. And the output 31, 36 and 38 wavelengths spacing on 100GHz within±3dB are obtained respectively. Furthermore, the output 32 wavelengths spacing on 100GHz within±1.5dB are achieved using the passive-feedback mechanism and cascaded SOAs.3. Studies on external electrical tuning of multi-wavelength fiber laser.1) The principle of single-sideband (SSB) modulator is analysed theoretically. A novel experimental method to achieve tunable wavelength fiber laser using SSB modulator with radio frequency (RF) resource is proposed.2) The experimental studies on single-wavelength shifting by SSB modulator are carried out. Optical SSB modulations of 8GHz, 10GHz and 12GHz single-tuning wavelength with side mode suppression ratio (SMSR) more than 20dB are experimentally obtained.3) The experiment studies on external electrical tuning are carried out. Experiments indicate that the effects of tuning are equal for each wavelength. The frequency tuning range is from 10MHz to12GHz, and the tuning precision is decided by the linewidth of multi-wavelength fiber laser and RF singal frequency tuning precision. Optical SSB modulations of 8GHz, 10GHz and 12GHz overall-tuning wavelengths with side mode suppression ratio (SMSR) more than 20 dB are experimentally obtained.