| With the development of science and technology,the accuracy of atomic clocks has been improved to the order of 10-19,and it has played a great role in many fields of scientific research and life.Traditional frequency transmission methods have fallen into a bottleneck.In order to achieve higher accuracy and long-distance frequency transmission,optical fiber has become the best way to transmit frequency.It has the characteristics of low price,low loss,small size,and strong antielectromagnetic interference ability.When optical fiber is actually used for frequency transmission,it also exposes some weaknesses of optical fiber as a transmission medium,such as being easily affected by various environmental factors,resulting in noise in the transmission process,which eventually leads to a decrease in the stability of frequency transmission and the quality of the signal received by the user will also decrease.Therefore,we need to study how to eliminate the impact of phase noise as much as possible.This paper mainly focuses on laser offset frequency locking based on the unbalanced interferometer structure.By using the frequency discrimination function of the unbalanced interferometer structure,the laser is feedback-controlled to complete frequency stable transmission.The main work of the paper includes the following aspects:1.Basic theoretical research.During the free running process of lasers,the laser frequency will drift due to interference from the external environment,so the basic theoretical aspects of stable frequency transmission of lasers are analyzed,including frequency transfer performance evaluation,frequency measurement techniques,basic structural classification of interferometers,and the use of delay lines interferometer completes the basic structural principle of frequency locking.2.Experimental program research.Research on how to realize the stable transmission of laser frequency,respectively studied the frequency locking based on the electric delay line interferometer structure and the frequency locking based on the optical delay line interferometer structure.We analyzed the two technical principles and their typical schemes,and propose two experimental designs based on these two schemes.3.Experiment setup process and experiment result analysis.After completing the experimental construction part,the principles and uses of the equipment needed for each part are introduced in detail.In the experiment based on the electric delay line interferometer,the fractional frequency instabilities of coarse frequency locking are calculated to be 2.6×10-12/@1s and 2.0×10-11/@10000s respectively,and the fractional frequency of fine frequency locking is not The stability is 1.1×10-15/@ls,2.6×10-18/@10000s respectively,the stability has been greatly improved,and the possible influence of each experimental device has been tested and analyzed.In the experiment based on the optical delay line interferometer,it can be seen that the fractional frequency instability when locked is improved by 2 orders of magnitude compared with unlocked. |
