Time synchronization method and system for coherent light communication terminal under extremely low optical signal to noise ratio
A technology of coherent optical communication and optical signal-to-noise ratio, applied in time-division multiplexing systems, transmission systems, multi-frequency code systems, etc., can solve problems such as unstudied performance and unsuitable frame synchronization sequences, and achieve low computational complexity The effect of reducing the complexity of hardware and algorithm calculation and wide estimation range
Active Publication Date: 2020-04-14
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology
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] like figure 1 Shown is a schematic structural di...
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The invention provides a time synchronization method and system for a coherent light communication terminal under an extremely low optical signal to noise ratio. The system comprises a clock synchronization module and a frame synchronization module. The clock synchronization module adopts a new clock error detector which does not need multiplication and is insensitive to the change of an optical signal to noise ratio in output characteristic. A multifunctional frame synchronization method based on a Q-chu guide sequence and a novel timing metric function is adopted in the frame synchronizationmodule. Through the cooperation of the two modules, the time synchronization of a transmitting end and a receiving end or time synchronization among multiple spatial diversity coherent optical receivers can be realized under the conditions of extremely low optical signal-to-noise ratio and extremely large dynamic change range, and the frequency offset estimation of a local oscillator laser can berealized at the same time. According to the invention, the noise margin and stability of the time synchronization system can be remarkably improved, the requirement on the processing capacity of thedigital signal processing chip is reduced, and the power consumption is reduced. The system has good application prospects in a space optical communication system and an 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