Research On Optical Signal Generation And Transmission Technology Based On Chirp-Managed Laser

The advent of the 5G communication era has higher and higher requirements for the data transmission rate and communication bandwidth of optical networks.Due to the limitation of transmission bandwidth,traditional microwave communication methods are gradually unable to meet the requirements of high-speed information exchanging which has dozens to hundreds of Gbps rates.Space laser communication has great advantages in communication bandwidth and speed,and is an irreplaceable transmission method in future data communication.Therefore,it has also become a research hotspot at home and abroad.The future development of laser communication will be towards high-speed,miniaturization and integration,network,all-optical and other directions.Realizing the small-integrated communication terminals is of great significance in the application field in the future.The chirp-managed laser is getting lots of attention for it has respectively combined the advantages of DML and EML,which has simpler structure and easier integration and can transmit optical signals at a higher rate and lower BER.In view of the development needs of miniaturization and integration of space laser communication terminals,we studied the direct modulation of OOK and RZ-DPSK according to the principle that chirp can modulate optical signals.This technique with no external modulator greatly simplifies the transmitter system.The reliability of the scheme is fully verified through theoretical analysis,experimental construction and field performance testing of the technical scheme.The main contents are as follows:1.Firstly,the development history of space laser communication and the current research status at home and abroad are described in detail.And next,we introduced the structure and characteristics of the space laser communication system.Furthermore,the international research status and future plans are explained.In addition,we studied the development and application of commonly used modulated lasers.2.The rate equation of the semiconductor laser and the frequency chirp theory are deduced.Based on this theory,the working principle and application of the chirp-managed laser are studied.We particularly clarified the principle of intensity modulation and phase modulation of the chirped-managed laser,which lays a theoretical foundation for the next experimental scheme.3.Based on the modulation principle of the chirp-managed laser,an experimental scheme was designed,and an experimental system was built,which completed the direct modulation of 2.5Gbps,5Gbps OOK signal and RZ-DPSK signal,and tested the eye diagram and constellation of the signal.Graphs,spectrograms and other characteristic parameters to analyze and optimize its performance.At the same time,the bit error rate of the external modulation transmitter is compared,and the results show that when the bit error rate is 10^-3,the bit error rate of the optical signal transmitted by the CML-based transmitting system is higher than that of the external modulation system,indicating that the signal quality of the direct modulation is better.it is good.In addition,the structure of the transmitter is simpler,which is beneficial to the integrated development of space laser communication.4.In order to simulate the transmission effect of the optical signal transmitted by the CML in the satellite-ground link,the space transmission experiment was carried out on the directly modulated transmitter,and the direct modulation transmitter based on the chirp management laser was tested when the modulation rate was 2.5Gbps and 5Gbps.The receiver sensitivity of the RZ-DPSK signal after 1km of space transmission,and the bit error characteristics of the RZ-DPSK signal transmitted back-to-back at the same rate are compared to verify the feasibility and advantages and disadvantages of the chirp-managed laser directly modulating the optical signal in space.