Coherent optical frequency transmission relay system and relay method

Abstract

The invention relates to a coherent optical frequency transmission relay system and a relay method. The system amplifies the optical frequency reference signal transmitted over a long distance throughan optical fiber link of the upper stage by a coherent optical receiving device of the first stage with low noise, and returns the amplified optical signal to the optical fiber link of the upper stage. The amplified optical signal is outputted to the next optical fiber link through the coherent optical receiving and noise compensating means of the second stage, the input return optical signal islow noise amplified, and the phase noise introduced when the optical frequency standard signal is transmitted in the next optical fiber link is compensated, so that the phase of the optical frequencyreference signal received at the remote end is locked to the phase of the optical frequency reference signal at the transmitting end. The technical scheme of the invention solves the problems of the limit of the phase-locked bandwidth of the ultra-long distance optical frequency reference signal transmission loop and the attenuation of the signal, and greatly improves the single-span amplificationdistance and the transmission precision of the optical frequency reference signal transmission.

Description

Technical field [0001] The invention relates to a relay system and a relay method for optical signal transmission in an optical fiber link. In particular, it relates to a coherent optical frequency standard signal transmission relay system and relay method. Background technique [0002] High-precision frequency standard transfer technology has very important meaning in time-frequency metrology and precision measurement of basic physical quantities. The remote comparison of optical clocks requires the transmission accuracy of the optical frequency transmission system to reach 10 on the thousand-second time scale. -18 The magnitude, which far exceeds the performance of frequency comparison using satellite links as the transmission medium. Therefore, optical fiber-based high-precision optical frequency transmission technology came into being. [0003] At present, fiber-based frequency transmission technology has made it possible to transmit and compare optical frequency standards on...

AI Technical Summary

Problems solved by technology

[0003] At present, optical fiber-based frequency transmission technology has made it possible to transmit and compare optical frequency standards on the order of thousands of kilometers, but this technology still has the following problems in long-distance transmission: 1. This solution needs to transmit to the far-end The optical signal returns to the local end to obtain the phase noise introduced by the optical frequency standard signal in the transmission of the optical fiber link. As the distance increases, the feedback bandwidth of the system will decrease. The feedback bandwidth will be reduced to tens of Hz, which greatly reduces the transmission accuracy of optical frequency standard signals; 2. It is necessary to place multiple bidirectional erbium-doped fiber amplifiers (EDFA) or fiber Brillouin amplifiers (FBA) in the link to Compensate for lost optical power

However, there are still two defects in this relay station structure: 1. This relay station structure only considers the amplification of the input optical signal of the previous stage, and does not amplify the optical signal transmitted by the optical fiber link of the next stage, so The single-span amplification distance is still limited. In the 1100km optical clock comparison experiment in France, three bidirectional EDFAs need to be placed between two relay stations 280km apart for auxiliary amplification, which will inevitably affect the signal-to-noise ratio of the optical signal. A certain degree of degradation; 2. When amplifying the input optical signal of the previous stage, the optical phase-locked loop scheme is adopted to lock the output phase of a high-performance narrow-linewidth laser in the system to the input optical frequency standard signal, The price of this narrow linewidth laser is usually high, adding significantly to the cost of this repeater

Images