Optical Intradyne Coherent Receiver Frequency Domain Compensation
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Solution Overview
Problem
High-speed optical transmission systems face complexity in signal reception due to carrier frequency offset and optical dispersion, requiring efficient compensation methods that reduce computational burden and resource usage.
Innovation Solution
Implementing frequency domain compensation for carrier frequency offset and optical distortion, utilizing Fourier Transform and Inverse Fourier Transform to shift and equalize signal spectra, thereby reducing the need for complex multiplications and additions, and allowing simultaneous compensation of chromatic and polarization mode dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time domain inverse rotation is used to compensate carrier frequency offset, then frequency offset compensation is achieved, but computational complexity increases significantly with high symbol rates
Solution Approach 1:
The patent transforms the frequency offset compensation from time domain to frequency domain by applying FFT to convert the time-domain signal to frequency-domain spectrum. The frequency offset is then compensated by simply shifting the spectral components, which is computationally much simpler than time-domain inverse rotation that requires multiple multiplications and additions per sample.
2Reliability
If multiple independent compensations (frequency offset and equalization) are performed separately, then each compensation is effective, but receiver structure becomes complex
Solution Approach 1:
The patent combines frequency offset compensation and optical distortion equalization into a unified frequency-domain processing framework. Both compensations are performed on the spectral components obtained from FFT, allowing simultaneous execution of multiple compensation functions within a single processing pipeline rather than requiring separate independent processing stages.
Solution Approach 2:
The frequency-domain processing approach serves multiple functions: it compensates for carrier frequency offset through spectral shifting, performs chromatic dispersion compensation through frequency-dependent phase correction, and enables polarization mode dispersion equalization. A single frequency-domain processing stage thus accomplishes what would otherwise require multiple separate compensation mechanisms.
Data Source
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AI summary
A method for carrier frequency recovery in an optical coherent transmission system is provided in which at least one kind of equalization of a received signal is performed in frequency domain, the method comprising: performing a frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset; obtaining the signal with the frequency offset compensated. Further, an optical coherent receiver is provided comprising: an equalization unit, adapted to perform at least one kind of optical distortion compensation of a received signal in frequency domain; a frequency offset compensation unit, adapted to perform the frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset to obtain the signal with frequency offset compensated. The method and the receiver provided by the present invention in carrier frequency recovery need only a frequency shift of the signal spectrum, reducing the computation complexity dramatically thus the processing is speed up and the resources needed are very much saved.