Research And Design Of Multi-wavelength And Narrow Line-width Fiber Laser

With the continuous development and mature of laser technology, the application field oflaser has greatly expanded. It is initially only served as the light source of wavelength divisionmultiplexing (WDM) in optical fiber communication system. Now, its application can befound in many fields such as industry, medicine, radar, sensing, and space flight and so on.Apart from the advantages in the traditional semiconductor lasers, fiber lasers have theirunique superiority, for instance, narrow line-width, multi-wavelength，simple structure, roomtemperature operation, and low cost.Based on traditional Erbium-doped fiber lasers (EDFLs) and related analysis andcalculation，this paper designed novel multi-wavelength and narrow line-width EDFLs. Noveloptical filters were proposed according to the characters of lasers. The following are the detaildescriptions of the work:1. The research background and the present situation of multi-wavelength and narrowline-width fiber laser and corresponding theory were introduced.2. The filtering technologies，structures，principle，and transmission performance of severalclassical optical filters were in multi-wavelength and narrow line-width fiber laser werediscussed.3. Dual-wavelength and multi-wavelength fiber laser with a narrow bandwidth, based on ahigh finesse fiber ring filter were proposed. The structure of the high finesse optical filterwas analyzed. Simulation and experiment had also been done to demonstrate its validity.The proposed filter was introduced into Dual-wavelength and multi-wavelength fiber laser.Under980nm laser diode (LD) pumped, the maximum output of the Dual-wavelength wasrespectively7.224dBm and4.496dBm, at the room temperature.4. A Dual-wavelength and narrow-linewidth fiber laser based on a Fabry-Perot (F-P) fiberfilter was been proposed. Polarization maintaining fiber Bragg grating (PM-FBG) and F-Pfiber filter are introduced in to the traditional laser structure. PM-FBG is used as thewavelength selection device. The fiber F-P filter consists of two optical couplers and asection of un-pumped Erbium-doped fiber (EDF). Due to the delay of the cavity and theloss generated by the EDF, the filter has comb spectral response. The incorporation of thefiber F-P filter leads to the suppression of undesirable modes. At the room temperature,the maximum output of the two wavelengths is respectively－0.259dBm and0.568dBm.5. A tunable and switchable multi-wavelength Erbium-doped fiber laser based on a novelnonlinear polarization rotation (NPR) structure was proposed. The improved NPRstructure makes use of3dB optical coupler to split into two channels of polarizationcontrollers. With the structure, when the optical signal circle one time in the cavity，thepolarization states will change double times. It has a higher efficiency than the traditional NPR structure. Experiment has achieved tunable single－wavelength laser output，tunableand switchable Dual-wavelength laser output and tunable multi-wavelength laser outputThe maximum output power is8.5dBm，and the tunable scale is4nm. After introduced5km single mode fiber (SMF),22wavelengths are simultaneously observed on the opticalspectrum analyzers. The interval of wavelengths is0.364nm. The pump used in theexperiment is976nm LD. When pumping power is128mW, With4hour’s observation,the22wavelengths output power fluctuation is less than0.5dB.