Research On The Key Control Technology In System Of Microwave Stabilized Phsae Transmission Over Optical Fiber

Microwave transmission system via optical fiber can achieve the effect of long-distance transmission,therefore,widely applied with the advantages of low loss,large transmission bandwidth,electromagnetic compatibility and so on.additional phase jitter will be generated as with the ambient temperature,stress and other factors form fiber refractive index and fiber length,resulting in the receiver signal phase instability.Aiming at the key technology of field stability control in microwave optical fiber transmission,the method of reciprocating phase correction was utilized to mainly study in several aspects of phase detection,phase compensation and adaptive phase control.(1)Phase detection:According to the principle of reciprocating phase compensation,the phase module was adopted to detect the phase difference between microwave signal in the local transmitter and the signal feedback from the receiver.And then,the phase detector output voltage signal,through the embedded processor from the analog-to-digital conversion for signal sampling and data processing,thus completing the microwave signal phase detection.Meanwhile,the special power supply regulator module was designed,in order to suppress the noise caused by power supply and microwave device so as to improve the accuracy of phase recognition.(2)Phase compensation:The system takes advantage of analog voltage-controlled microwave phase shifter to compensate for the phase.The processor converts the acquired phase difference information into an analog voltage output through a digital-to-analog conversion module,thereby adjusting the control voltage of the phase shifter to compensate for the phase.As the direct adjustment of the laser modulation of the microwave signal for the phase correction of the signal,the receiver uses a photodetector for direct detection after fiber transmission,so that the demodulation of the microwave signal phase and the transmitter side of the microwave signal phase synchronization.(3)Adaptive phase control:Since the voltage output from the analog-to-digital conversion module acquisition phase module has twice the phase jitter information in the transmit-end stable-phase control system,the digital-analog conversion output voltage is controlled in real time by the adaptive control algorithm Doubling the phase jitter,so as to control the phase of the microwave signal automatically.Finally,The system test link was set up in the laboratory,and the steady-state control system of 2.4GHz microwave signal transmission 50km single-mode fiber was tested.It is measured that the signal phase jitter is less than 1.7ps in 2000 seconds;with the stress applied,the signal phase jitter in less than 100 seconds is less than 4.8 ps.