Research On External Cavity Tunable Laser Applied In Coherent Optical Communication

Due to the rapid growth of data, video, and other business, the higher transmissioncapacity of the communication bandwidth network has been indispensible. Intensitymodulation and direct detection technology(IM-DD) systems facing a higher transfer rate,chromatic dispersion, nonlinearity have been unable to meet the transmitted increasinglygrowing of network capacity. Coherent optical is expected to be the best solution forhigh-speed signal transmission, and thus will necessarily become the future selection ofhigh-speed large-capacity transmission network. Large-scale application of densewavelength division multiplexing (DWDM) in optical fiber communication system makesthe industry’s increasing demand of tunable lasers. Recently, coherent detection technologyused in DWDM optical fiber communication system constantly refresh the record in termsof transmission speed, capacity and transmission distance. Among them,100Gbit/stechnology based on DWDM system maturation and large-scale application is the best proof.Due to coherent detection technology higher requirements on laser linewidth, narrowlinewidth tunable laser is particularly important as one of the core optical devices incoherent optical communication system. In a variety of tunable lasers, external cavitytunable laser because of its narrow linewidth, wide tuning range and high output power, iswinning the widespread concern.The main work of this paper are as follows: after a comprehensive, systematicintroduction to principle of the external cavity tunable laser, a Micro-Electro-Mechanical-Systems（MEMS）-based external cavity tunable laser is proposed. The influences of the keyelements in the structure on the output characteristics of the device are analyzed, the actualthe device is prepared and given the appropriate design of the drive circuit. The theoreticalanalysis of the noise characteristics of the laser, and test methods are also developed. Theactual development of the laser assembly has excellent output characteristics. To furthervalidate assembly performance, finally performance of the laser assembly in a100Gb/spolarization multiplexed quadrature phase shift keying and optical orthogonal frequency division multiplexing experimental platform is studied. The test results show that theexternal cavity tunable laser can be used as an ideal choice of light source in coherentoptical communication.