High Performance Microwave Photonic Link Study

As the demand of information capability is going up quickly, and the high-speed development of the fiber technology, optoelectronics and microwave integrate circuit, microwave photonics appeared, which processes microwave signal with photonic technologies. As the hard core of optical processing, microwave photonic links (MPL) are being used increasingly to conveying RF signals, thus they can realize many functions, such as transmit, distribution, and delay. Compared with the conventional microwave links, MPL offer high bandwidth, low loss and low weight. This thesis mainly studied factors that influenced the performance of MPL, to reduce the noise figure and enhance the dynamic range.First, this paper has introduced the principle of MPL and modeled them, get the mathematical models of directly and externally modulator links, and analyzed the factors which influenced the performances of MPL, such as the relative intensity noise (RIN), the loss of fiber, the turn rate of E/O and O/E, and the frequency of microwave. Several experiments were performed to demonstrate the above analysis.In order to compress the noises of the system, this thesis used coherent balanced detection for MPL, and balanced detection can reduce the relative intensity noise of the laser. This thesis had established the noise mode of the system, analyzed and calculated the formula of the system's gain and noise figure (NF). The result verified balanced detection can deduce about 9.7 dB in the NF.To improve the dynamic range of MPL, a single sideband suppressed-carrier (SSB-SC) technique was used in the thesis. The sideband was suppressed by means of a fiber Mach-Zehnder interferometer with amplitude electro-optical modulator in each branch. The attenuation of the carrier was achieved by proper biasing of the integrated modulator, and suppression of 34.6 dB in the carrier and 47.5 dB in the sideband were obtained. At last, we combined the single sideband suppressed-carrier and balanced detection together, and simulated the system.