| High-precision time frequency plays an important role in basic research fields,such as fine structure constant variation in precision measurement,gravitational redshift,gravitational wave detection,etc,and in applied research fields,such as satellite emission monitoring and aerospace in the field of defense,communications,power transmission and monitoring in the market economy.Long-distance and high-precision time-frequency transmission and comparison techniques are absolutely technical components for the establishment and maintenance of microwave clock,optical clock performance comparisons and international atomic time(TAI).At present,the traditional frequency time comparison methods in the world mainly include GPS Common-View Comparison,GPS+GLONASS binary-star common-view Comparison,and Two-Way Satellite Time-Frequency Transmission(TWSTFT).The most accurate of these traditional remote time-frequency comparison methods has a day-level instability of 10-16 and a second-level instability of 10-13.However,since the instability of the current optical clock has reached the level of 10-19,the traditional remote time-firequency comparison method can't meet the requirements of the optical clock comparison.The transmission and comparison of the current optical clock is realized through the optical fiber link,and the optical fiber has the advantages of low loss and strong anti-interference ability at the communication wavelength.In 2012,Physikalisch-Technische Bundesanstalt(PTB)and Max-Planck-Institut(MPI)fur Quantenoptik in Germany accomplished 920 km optical clock comparison through fiber optic link,and the long-term instability is less than 4×10-19.In 2016,Germany's PTB and France's LNE-SYRTE realized remote comparison of Sr optical clock through 1415 km of long optical fiber,the comparison accuracy of 1000 s is better than 3×10-17.In the process of optical clock comparison,the frequency stability of the optical clock must be transmitted to the communication wavelength of 1.5 ?m by optical comb.This paper mainly introduces the design of some circuits needed in the process of laser frequency measurement and transmission using optical comb.The main contents of the thesis are as follows:(1)Introduce traditional time comparison methods,such as GPS Common-View Comparison,GPS+GLONASS binary-star Common-View Comparison,Two-Way Satellite Time-Frequency Transmission(TWSTFT).Introduce the development of time-frequency comparison based on fiber transmission and our experimental scheme.(2)Noise filtration of hydrogen clock signal(HCS)after transmission.The hydrogen clock signal is the indispensable reference for physics experiments of precision measurement.We introduces a scheme for filtering HCS after transmission,which reduces the phase noise and improves the short-term instability of the HCS.After the filtering circuit,the power of the HCS was amplified from-4.4 dBm to 5 dBm,the phase noise background of the HCS was reduced about 10 dB,and all disturbance at higher than 1 Hz were eliminated.(3)Design of microwave scaling circuit.We introduces a scheme to complete the frequency instability transmission by scaling the microwave signal.The MCU receives the PC control command words and data,which was transferred via USB.And the MCU controls the DDS's operation,write or read DDS data.Writing controls the DDS ratio of the input signal,and reading can get the frequency control word inside the DDS,and then transfer the frequency instability to other frequency by the phase-locked loop and the I2D circuit. |
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