Study On High-precision Sampling Of Weak Optical Signals

In recent years,high-tech technologies such as quantum information technology and biotechnology have developed rapidly.As an important component of these technologies,weak optical signals,how to collect information on weak optical signals with high speed and high precision,are related to the overall performance of the system.Different from the acquisition of strong light signals,the weak optical signal requires higher resolution and sampling rate of the sampling module in the information extraction process.However,it is difficult to meet the requirements of high resolution and high sampling rate of weak optical signal sampling in an actual sampling system.In order to solve this problem,this paper designs and implements an equivalent sampling system based on high-speed ADC chip.The specific contents are as follows:1.This paper analyses the contradiction between the high sampling rate and the high resolution in the conventional sampling system,and provides a solution as equivalent time sampling to avoid this matter.This method utilizes programable time delay chip to delay the sampling clock with equal step length,so that the equivalent time sampling can be achieved.2.After identifying the problem,the circuit of the card is subsequently designed.The circuit of the card is composed of 5 modules,they are clock-generate module that uses LMK03806 chip,programmable time-delay module that uses MC10EP195 chips,ADC sampling module that uses high-speed ADS54RF63 chips,cards using FMC_LPC as interface and data interaction module as well as the power supply module that connect the card and the FPGA.Lastly,the PCB board is drawn and the card is fabricated.3.The performance of the card after fabricating is thoroughly conducted to testify whether it can satisfy the requirement of sampling weak light signal.First,the clock module is tested,which successfully verify the two functions that it can support the writing from the FPGA to the clock register,output stable clock with high frequency.The other function is it can achieve the clock synchronization between the transmitter and the receiver,avoiding the sampling drifting.Next,the sampling module of the ADC sampling module is tested,by designing program the metastability is mitigated.The test manifests that the card can generate a at least 9.25 bits significant digit under the 200MHz of sampling rate.By controlling the MC10EP195 chip,the sampling clock of 100MHz can accomplish a real time time-delay,which equals a 2GHz of sampling frequency.The main purpose of this paper is to design a daughter card for high-precision sampling of weak optical signals,which can meet the high-speed and high-resolution requirements of high-precision sampling technology.And the solution of equivalent sampling by means of programmable delay chip is relatively simple and can be widely used.