基于IM/DD体制的星间激光通信测距技术

随着当前低轨卫星组网星座计划的日益增加，对卫星间高精度校时、测距需求也越来越迫切。提出基于直调直检IM/DD（Intensity Modulation with Direct Detection）的测距技术的实现方法，使其能同时兼顾测距精度及系统成本。基于IM/DD的测距是利用高精度的秒脉冲到达时间来测量距离。使用IM/DD光通信的数据传输方式，在正常的数据帧传输中插入少量的测距信息，无需中断正常的通信模式，也无需网络时钟频率同步，数据帧的发送周期也无需与秒脉冲保持同步关系，即可使用双向单程测距方法进行测距。使用秒脉冲对本地时钟进行频率测量，对测距过程参数进行修正，只需要采用普通晶体振荡器作为本地时钟源，不需要使用高精度测距通常所需的全网络同步时钟信号或者高稳定度时钟源，便可以达到IM/DD通信码元时间量级的测距准确度和精确度，同时降低了时频同步系统的复杂度、对元器件的要求以及整个通信测距系统的成本，解决了现有技术中测距精度及系统成本不易同时兼顾的问题。

Research on laser communication and ranging based on IM/DD mode

With the increasing constellation plan of low-orbit satellite networking, the demand for high-precision time calibration and ranging between satellites is becoming more and more urgent. This paper proposes the implementation of IM/DD to balance the ranging accuracy and system cost. Distance measurement of high precision pulse of time based on IM/DD is used to measure the distance. It employs the data transmission method of direct modulation and direct detection optical communication, inserts a small amount of ranging information into the normal data frame transmission, without interrupting the normal communication mode, and without the need to synchronize the frequency of the network clock, and the transmission period of the data frame has no need to be related to the second pulse. Keeping the synchronization relationship, the two-way one-way ranging method can be used for ranging. It uses the second pulse to measure the frequency of the local clock and correct the parameters of the ranging process. It only needs to use the ordinary crystal oscillator as the local clock source, and does not need to use the full network synchronization clock signal or high stability usually required for high-precision ranging. The clock source can achieve the ranging accuracy and precision of the time level of the direct adjustment and direct detection of the communication symbol, and at the same time reduce the complexity of the time-frequency synchronization system, the requirements for components and the cost of the entire communication ranging system. The problem in the prior part that ranging accuracy and system cost are not easy to be taken into account at the same time is solved.