Time synchronization method and system for coherent optical communication terminals under extremely low optical signal-to-noise ratio
A technology of time synchronization system and coherent optical communication, applied in time division multiplexing system, transmission system, multi-frequency code system, etc., can solve the problems of unresearched performance, unsuitable frame synchronization sequence, etc., and achieve low computational complexity , the effect of reducing hardware complexity and algorithm calculation, high noise immunity
Active Publication Date: 2022-03-15
HUAZHONG UNIV OF SCI & TECH
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The modified FSA shows better performance, but its performance on signals with very low OSNR has not been studied so far
Recently, Fractional Fourier Transform (FrFT)-based FSAs have been proposed for optical OFDM multi-carrier and 16QAM single-carrier systems, which have better noise immunity, but the frame synchronization sequences used by these FSAs are not suitable for BPSK and QPSK alphabets
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[0032] In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings, tables and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.
[0033] The invention provides a time synchronization system under extremely low optical signal-to-noise ratio, which includes a clock synchronization module and a frame synchronization module, and is suitable for the environment in FSOC with extremely low optical signal-to-noise ratio and strict power consumption requirements.
[0034] Such as figure 1 Shown is a schematic structural...
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The invention proposes a time synchronization method and system for a coherent optical communication terminal under an extremely low optical signal-to-noise ratio. The system includes clock synchronization and frame synchronization modules. In the clock synchronization module, a new clock error detector which does not need multiplication and whose output characteristics are insensitive to the change of optical signal-to-noise ratio is adopted. A multifunctional frame synchronization method based on Q‑chu pilot sequences and a novel timing metric function is implemented in the frame synchronization module. The combination of the two modules can realize the time synchronization between the transmitting and receiving ends under the conditions of extremely low optical signal-to-noise ratio and a large dynamic range, or time synchronization between multiple space-diversity coherent optical receivers, and can also realize the local oscillator Frequency offset estimation for lasers. The invention can significantly improve the noise tolerance and stability of the time synchronization system, reduce the requirement on the processing capability of the digital signal processing chip, and reduce its power consumption. It has a good application prospect in space optical communication system and optical fiber communication system.
Description
technical field [0001] The present invention relates to the technical fields of optical fiber communication, free space optical communication, coherent detection and digital signal processing, and more specifically, relates to a time synchronization method for a coherent optical communication terminal under extremely low optical signal-to-noise ratio. Background technique [0002] With the improvement of communication speed and capacity requirements, coherent detection technology has become a key technology in the next generation optical communication system and has been widely used. [0003] Due to the large-scale relative motion of terminals, changes in atmospheric channel conditions, and large transmission loss, free-space optical communication (FSOC) signals usually have larger dynamic range and lower OSNR compared with optical fiber communication signals. Therefore, flexible digital coherent receivers (DCRs) that can adapt to different channel conditions have attracted ...
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IPC IPC(8): H04B10/61H04J3/06H04L27/26H04B10/25H04B10/11
CPCH04B10/6164H04L27/2656H04J3/0638H04B10/25H04B10/11
Inventor 崔晟唐剑威谷云峰程前刘德明
Owner HUAZHONG UNIV OF SCI & TECH