Research On The Key Technology Of 2-6GHZ Broadband Microwave Signal Coherent Optical Transmission

Broadband microwave optical links transmit the microwave signal through optical fiber, which combines the advantages of microwave technology and optical fiber transmission technology, such as large bandwidth, small volume, light weight, resistance to electromagnetic interference and so on, so in many specific field have be studied. Coherent optical transmission are cutting-edge technology in microwave optical link, in the digital signal transmission system, the coherent detection of optical signal technique has been one of hot topics in the research of people, but the coherence of the analog signal transmission is difficult, while it is possible to solve some problems-such as receiving sensitivity is low, power limited-of traditional direct detection links, but the coherent microwave transmission technology is not very mature.This paper makes a detailed study on the performance of the coherent optical link, through the intensity modulation-heterodyne coherent detection, intensity modulation-homodyne coherent detection, phase modulation-heterodyne coherent detection, three different structure coherent optical link, have a theoretical derivation about parameters of the link,such as links gain, noise performance, dynamic range, and the comparative analysis of different structure. From the analysis results, the performance of the system is mainly composed of signal light and intrinsic optical power, system bandwidth and excitation system parameters such as noise, the signal-to-noise ratio of Intensity modulation-homodyne coherent detection link have improved 3dB than intensity modulation-heterodyne detection, and the signal-to-noise ratio of phase modulation-homodyne detection higher about 6 dB than intensity modulation-homodyne detection is, can achieve about 45 dB; also Phase modulation-homodyne detection link the spurious-free dynamic range is bigger than the other two structure, also can achieve about U2dB·Hz2/3.On the basis of theoretical analysis with optical simulation software optisystem simulation test for microwave coherent optical transmission system, by contrast, use of homodyne detection than heterodyne detection methods such as RF gain and noise figure performance have improved, but its implementation is difficult; Phase modulation than intensity modulation link at the same time, the performance is relatively improved. Consistent with theory analysis. Finally, because of the complexity of the microwave signal coherent optical transmission link and with high cost, have major technical hurdles to overcome, still need to further research and development.