为了研究高速1550 nm微波光纤链路的高精度外调制特性,针对多量子阱分布反馈激光器的物理模型讨论了输出功率、阈值电流与温度的依赖关系,建立了相应的恒温恒功率控制电路,使激光器输出功率稳定在±0.005 dB以内,调制输出3 dB谱宽为0.5 nm,边模平坦,边模抑制比大于30 dB。另外设计了自动增益控制电路和附加相位调制电路,对外调制阶段的光功率进行控制。实验结果表明,采用1550 nm激光器及上述控制电路构成相应的外调制微波光纤链路系统,可有效地提高光发射模块输出光功率的稳定性,克服了直接调制带来的光谱展宽和消光比不稳定的缺点,实现了微波信号的高线性低失真传输。

To study high precision external modulation characteristics of high speed 1550 nm microwave fiber link, the relation of output power, threshold current and temperature is disucssed based on the physical model of multiple quantum well-distributed feedback (MQW-DFB) laser diode (LD). A corresponding power and temperature control circuit is set up to ensure the output optical power fluctuation within ±0.005 dB and the modulated output with 0.5 nm of 3 dB spectrum width. Its side modes are planar and the side mode suppression ratio is more than 30 dB. In addition, the automatic gain control circuit and accessional phase modulation circuit are designed in order to control light power on the stage of external modulation. Experimental results shows that the external modulation microwave fiber link system composed 1550 nm MQW-DFB laser diode and corresponding driving circuits can effectively improve output light power stability of light emitting module. It overcomes the disadvantages of light spectrum expansion and unstable optical extinction ratio due to direct modulation and realizes fiber transmission of microwave signal with high linearity and low distortion.