带前置光放大的星间微波光子链路建模及性能优化
摘要
An optical preamplifier is applied to increase the signal-to-noise ratio (SNR) of inter-satellite microwave photonics links considering the large signal loss in distant propagation. An optically preamplified intersatellite microwave photonics links model is established and an analytical expression of SNR is derived with the method of expanding Bessel series and Graf addition theorem. The dominant noise components influence the link performance is confirmed, given the desired SNR, the direct current (DC) bias phase shift of modulator can be optimized so as to minimize the output power of laser diode (LD) under different gain of optical preamplifier, and the effects of the optical preamplifier gain on the minimum output power of LD and optimal DC bias phase shift is also examined. According to the numerical results, the output power of LD needed to achieve the required SNR decreases while increasing the gain of preamplifier, and the corresponding optimal DC bias phase shift decreases first and then increases. For QPSK modulation signal, the output power of LD needed to achieve the SNR of 15.56 dB (BER=10<sup>-9</sup>) is at least 45 dBm without an optical preamplifier, while the output power of LD is required only 22.57 dBm as the gain of preamplifier is 15 dB.