| The measurement of wind speed is one of the most important projects in climatology. Improving the accuracy of wind speed measurement has great importance in some fields. Such as rocket launching, aircraft taking off and landing, and some military uses. Based on the technology of balance detection, dual-balanced heterodyne detection system has stable environment adaptability and excellent performance of signal-to-noise ratio(SNR). And the intensity, frequency, phase and polarization of the signal can be realized as well. As a result, dual-balanced heterodyne detection has wide value of the application in the field of coherent laser radar, coherent optical communication and heterodyne interferometry. The research of dual-balanced heterodyne detection has great significance to improve the detection sensitivity of 2μm coherent laser radar.The main work of this paper: 1. The principle of dual-balanced heterodyne detection is introduced in Chapter 2.1. The principle of dual-balanced heterodyne detection is introduced in Chapter 2. Established the mathematical model of dual-balanced heterodyne detection using matrix optics method. By comparing the balanced optical heterodyne detection and general coherent detection, we theoretically proved dual-balanced heterodyne detection has superiority on eliminating oscillator intensity noise and improving signal-to-noise ratio. 2. Optisystem( an optical communication simulation software) is used to build the double balanced detection system model in Chapter 3. By substituting actual device parameters, the simulation experimental results verified feasibility of dual-balanced detection in demodulating signal amplitude, frequency, phase and polarization. 3. Chapter 4 Analysised the cause of actual balance detector two branch currents not matching.By numerical simulation, we knew the influence of attenuation of the branch on the system SNR. Used the Opti System simulation calculation, put forward optimized scheme and the optimization parameters. 4. From collimating loss angle and optical path difference, chapter 5 discussed the space mismatch problem in dual-balanced heterodyne detection. The conclusion is, balance detection isn’t sensitive to optical path difference. However, it’s very sensitive to the alignment straight mismatch angle. As a result, dual-balanced heterodyne detection has very high requirement in assembly precision. 5. Based on the former dual-balanced heterodyne detection structure, chapter 6 proposed the new model of fiber dual-balanced heterodyne detection graph structure. The structure was also built and simulated by using Opti System simulation software. The simulation results prove the feasible of new design fiber dual-balanced detection structure. Introduced recent special fiber optical device, which is suitable for the research. This paper is the foundation for the future fiber dual-balanced heterodyne detection. |
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