Signal Processing Device Frequency-Domain Equalization
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Solution Overview
Problem
In digital coherent type optical communication, the computation amount required for noise removal in reception devices is substantial, hindering communication speed improvement.
Innovation Solution
A signal processing device with a compensation unit that performs Fourier transform, equalization, and inverse Fourier transform on polarization-multiplexed and multi-value-modulated optical signals, using an equalization coefficient matrix W(f) set based on specific equations to reduce computation for noise removal, considering band limit and wavelength dispersion conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional equalization methods are used for noise removal in digital coherent optical communication, then noise removal performance is maintained, but computation amount becomes excessively large
Solution Approach 1:
The patent transforms the equalization problem from time domain to frequency domain by applying Fourier transform, changing the parameter domain where the equalization operation is performed. This allows the use of simple multiplication in frequency domain instead of complex convolution in time domain, significantly reducing computation amount while maintaining equalization performance for noise removal
Solution Approach 2:
The patent replaces the traditional time-domain convolution-based equalization method with a frequency-domain multiplication-based method. By substituting the mechanical convolution operation with Fourier transform followed by simple multiplication and inverse Fourier transform, the computational complexity is dramatically reduced, enabling faster processing speed
2Measurement precision
If complex equalization processing is performed to handle wavelength dispersion and band limit conditions, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent incorporates wavelength dispersion and band limit conditions into the equalization coefficient design by using Fourier transform to convert these physical constraints into frequency-domain parameters. The equalization coefficient is designed to simultaneously compensate for wavelength dispersion and satisfy band limit conditions through frequency-selective filtering, achieving signal quality improvement without increasing device complexity
Solution Approach 2:
The patent designs a universal equalization coefficient that simultaneously handles multiple functions: compensating for wavelength dispersion, satisfying band limit conditions, and performing noise removal. By combining these functions into a single frequency-domain multiplication operation, the patent avoids the need for separate processing stages, thereby reducing device complexity while maintaining signal quality
Data Source
AI summary
A transfer function calculation unit (522) calculates a diagonal matrix G(f) on the basis of a band limit condition g(t) used in a transmission device (20). A transfer function calculation unit (524) calculates a diagonal matrix C(f) on the basis of a wavelength dispersion amount c(t) incurred in an optical transmission path. A transfer function combination unit (526) combines the diagonal matrix G(f) with the diagonal matrix C(f) so as to calculate a diagonal matrix H(f)=G(f)×C(f). An equalization coefficient calculation unit (528) calculates an equalization coefficient matrix W(f)=H(f)H(H(f)HH(f)+(1/Es)×Φη)−1 used in a multiplication unit (506) by using the diagonal matrix H(f). Here, H(f)H is a Hermitian transposed matrix of a matrix H(f), Es is power of an optical signal, and Φη is a diagonal matrix with N rows and N columns.