光载无线通信链路拉格朗日乘子线性度优化

Nonlinear distortion is identified as a major factor affecting the operating bandwidth and spurious-free dynamic range (SFDR) of radio-over-fiber link. Combining with the RF power ratio, polarization multiplexing and bias control techniques, a multi-channel radio-over-fiber link with high dynamic range and octave-spanning bandwidth is constructed for distributed antenna system (DAS). A model of linearity optimization for the proposed link is developed using a Lagrange multiplier method optimization model, and the best trade-off among RF output power, polarization incident angle and RF power ratio can be obtained. Thus, the optimization of link linearity can be achieved on the premise that the third-order intermodulation distortion (IMD3) and second-order harmonic distortion (HD2) are suppressed simultaneously. The simulated and experimental results show the proposed scheme is effective and feasible.