相干光通信技术是利用了相干调制和外差检测技术。所谓相干调制，就是利用要

相干光通信技术是利用了相干调制和外差检测技术。所谓相干调制，就是利用要传输的信号来改变光载波的频率、相位和振幅（不像强度检测那样只是改变光的强度），这就需要光信号有确定的频率和相位（不像自然光那样没有确定的频率和相位），即应该是相干光，激光就是一种相干光。所谓外差检测，就是利用一束本机振荡产生的激光与输入的信号光在光频器中进行混频，得到与信号光的频率、位相和振幅按相同规律变化的中频信号。相干光通信在发送端对光载波进行幅度调制（ASK）、额率调制（FSK）或相位调制（PSK），在接收端则采用零差检测或外差检测等相干检测技术进行信息接收，光源发出频率为f的光脉冲，通过调制器将已经变成电信号的信号源调制到光脉冲包络上，通过长距离传输后，到达接收端；接收端采用外差技术，首先通过耦合器将光信号和本振光信号同时送到光电检测器，信号光和本振光在满足波前匹配和偏振匹配的条件下混频，得到顿率为fm的中频信号，然后该信号经过放大滤波后送到解调器解调，最终到达接收电路完成通信过程。由于中频滤波器的带宽可以做得窄面陡，因此相干光通信的信道选择性很好。相干光通信的最新进展在数字信号处理（DSP）中，进行了综述。基于DSP的相位和振管理技术使相干检测变得稳健实用。通过相干检测，接收信号的复场为完全恢复，允许补偿线性损伤，包括使用数字滤波器的色散和偏振模色散。在此外，光纤非线性也可以通过反向使用数字领域的传播。

相干光通信技术是利用了相干调制和外差检测技术。 所谓相干调制，就是利用要传输的信号来改变光载波的频率、相位和振幅（不像强度检测那样只是改变光的强度），这就需要光信号有确定的频率和相位（不像自然光那样没有确定的频率和相位），即应该是相干光，激光就是一种相干光。 所谓外差检测，就是利用一束本机振荡产生的激光与输入的信号光在光频器中进行混频，得到与信号光的频率、位相和振幅按相同规律变化的中频信号。 相干光通信在发送端对光载波进行幅度调制（ASK）、额率调制（FSK）或相位调制（PSK），在接收端则采用零差检测或外差检测等相干检测技术进行信息接收，光源发出频率为f的光脉冲， 通过调制器将已经变成电信号的信号源调制到光脉冲包络上，通过长距离传输后，到达接收端；接收端采用外差技术，首先通过耦合器将光信号和本振光信号同时送到光电检测器，信号光和本振光在满足波前匹配和偏振匹配的条件下混频， 得到顿率为fm的中频信号，然后该信号经过放大滤波后送到解调器解调，最终到达接收电路完成通信过程。 由于中频滤波器的带宽可以做得窄面陡，因此相干光通信的信道选择性很好。 相干光通信的最新进展在数字信号处理（DSP）中，进行了综述。 基于DSP的相位和振管理技术使相干检测变得稳健实用。 通过相干检测，接收信号的复场为完全恢复，允许补偿线性损伤，包括使用数字滤波器的色散和偏振模色散。 在此外，光纤非线性也可以通过反向使用数字领域的传播。

Coherent optical communication technology uses coherent modulation and heterodyne detection technology. The so-called coherent modulation is to use the signal to be transmitted to change the frequency, phase and amplitude of the optical carrier (unlike intensity detection, which only changes the intensity of the light). This requires that the optical signal has a certain frequency and phase (unlike natural light, which has no certain frequency and phase), that is, it should be coherent light, and laser is a kind of coherent light. The so-called heterodyne detection is to use a laser produced by the local oscillation and the input signal light to mix in the optical frequency device, so as to obtain the intermediate frequency signal which changes according to the same law as the frequency, phase and amplitude of the signal light. Coherent optical communication carries out amplitude modulation (ask), amplitude rate modulation (FSK) or phase modulation (PSK) on the optical carrier at the transmitting end. At the receiving end, coherent detection technology such as zero difference detection or heterodyne detection is used for information reception. The light source sends out optical pulse with frequency of F, and modulates the signal source that has become electrical signal to the optical pulse envelope through the modulator. After long-distance transmission At the receiving end, heterodyne technology is used. First, the optical signal and local optical signal are sent to the photoelectric detector through the coupler at the same time. The signal light and local optical are mixed under the conditions of wavefront matching and polarization matching, and the IF signal with the frequency of FM is obtained. Then the signal is sent to the demodulator for demodulation after amplification and filtering, and finally reaches the receiving circuit to complete the communication process 。 Because the bandwidth of IF filter can be narrow and steep, the channel selectivity of coherent optical communication is very good. The latest development of coherent optical communication is summarized in digital signal processing (DSP). The phase and vibration management technology based on DSP makes coherent detection robust and practical. Through coherent detection, the complex field of the received signal is fully recovered, allowing compensation for linear damage, including dispersion and polarization mode dispersion using digital filters. In addition, fiber nonlinearity can also be propagated through reverse use of the digital domain.<br>