Frequency offset estimation method based on multi-step interpolation for coherent light communication systems

Abstract

The invention relates to a frequency offset estimation method based on multi-step interpolation. The method comprises the following steps: performing biquadrate MQAM modulation format or M power MPSK modulation format operation on a sampling value L with a certain length, selecting a small segment of data N0 therein to serve as FFT, and figuring out the frequency corresponding to the maximum frequency spectrum value to serve as a coarse frequency offset estimation value; respectively carrying out DFT by using N0 sampling points at a position + / -0.5 away from the coarse frequency offset estimation value to acquire two frequency spectrum values, calculating a frequency offset estimation error via the two values, and correcting the coarse frequency offset estimation value to acquire a frequency offset estimation value after one-step interpolation; respectively carrying out DFT by using 2N0 sampling points at a position + / -0.5 away from the frequency offset estimation value after one-step interpolation to acquire two frequency spectrum values, calculating the estimation error via the two values, and correcting the coarse frequency offset estimation value to acquire a frequency offset estimation value after two-step interpolation; and so on, until carrying out DFT interpolation by using L sampling points to acquire a final frequency offset estimation value. The algorithm has low complexity and is suitable for all coherent light communication systems.

Description

technical field [0001] The present invention relates to the communication field, and more specifically, relates to a frequency offset estimation scheme based on multi-step interpolation in a coherent optical communication system. Background technique [0002] In order to improve spectrum utilization and communication capacity, high-order modulation formats are used to modulate signals in optical communication, and the amplitude and phase information of optical carriers are utilized at the same time. Signals in this high-order modulation format require coherent demodulation to recover the signal. Therefore, a coherent receiver is required at the receiving end. A local laser is provided in the coherent receiver for coherent demodulation of the received signal. [0003] For the homodyne coherent detection method, the local laser at the receiving end is required to have the same wavelength as the laser at the transmitting end. However, due to the manufacturing process of the ...

AI Technical Summary

Problems solved by technology

The present invention improves this algorithm and proposes the idea of ​​gradually increasing sampling points and performing multi-step interpolation. This algorithm can achieve the same estimation accuracy as the original traditional DFT interpolation algorithm, but the complexity is greatly reduced.

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