Research On Single Mode Fiber Laser And Applications Of Coherent Optical Communication

With the development of laser technology and fields like coherent optical communication,the requirements for the single-longitudinal-mode lasers are increasing.Because of its many advantages such as high beam quality and power density,good thermal dissipation and anti-interference performance,fiber laser has been favored by researchers.It has wide potential application in optical fiber communication,optical sensing,industrial,medical and military fields,so it has been extensively studied in recent years.In this thesis,the basic principles of fiber laser are analyzed,and the work we have done is followed below:?1?We introduce fiber laser with different structure.The basic working principle of Er³⁺-doped fiber laser is summarized,and the three level and four level systems are both described.The output characteristics of Er³⁺-doped fiber laser are analyzed.Different single longitudinal mode selection methods of lasers are introduced.Different factors that influence the output linewidth of lasers are analyzed.?2?A single longitudinal mode selection scheme is proposed by using the method of waveguide resonant ring.The function of the waveguide resonant ring is theoretically derived and simulated,and it is proved that it has the function of selecting the longitudinal mode.The scheme of using waveguide resonant ring to build the optical fiber waveguide hybrid laser is proposed,and the parameters are selected reasonably.?3?According to the design,a fiber waveguide hybrid laser which has the 1535nm output with single longitudinal mode operation is fabricated and its performance is tested.We make the desired waveguide ring based on the silicon waveguide.By using the single core fiber array,the successful coupling of the optical fiber and the waveguide is realized.We use FBG with the bandwidth of 0.1nm as cavity reflector,the EDF150LD high concentration erbium doped fiber produced by OFS Corporation as the gain medium,and LC962UF76P-20R semiconductor laser produced by Oclaro Company as the pump source.When the pumping current was 1.0A,the peak output power is measured 3.5mW.By utilizing a photoelectric detection to receive the output light,single-longitudinal-mode operation is successfully verified according to the characteristics of the beat signal.In order to ensure that the temperature of the resonator is under control,the whole resonant cavity is fabricated in the copper,and the refrigeration function is realized by using TECs.?4?We introduce the research background and basic principles of coherent optical communication.The performances of homodyne and heterodyne coherent optical communication are compared in several aspects.The process of coherent optical communication is analyzed and the factors influencing it are also introduced.In addition,effects of noise on coherent optical communication is also analyzed and noise of the laser made by us is tested.Finally,we propose to use optoelectronic feedback circuit in order to depress the noise level.