Optical Receiver Equalizer for Low Power DSP
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Solution Overview
Problem
Digital signal processing (DSP) in optical communication systems faces high power consumption due to the need for high sampling rates in ADCs, which introduces aliasing noise when reduced, making it challenging to develop commercially viable transceivers for data rates above 100 Gbps.
Innovation Solution
An optical receiver with an equalizer that generates and applies a subset of non-zero equalization coefficients to the signal, zeroing out coefficients corresponding to specific frequency components, thereby reducing the number of complex multiplications and power consumption without introducing aliasing noise, using a chromatic dispersion compensator and adaptive channel equalizers like CMA or LMS algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the sampling rate of ADC is reduced to reduce power consumption, then power consumption is reduced, but aliasing noise is introduced into digital signals
Solution Approach 1:
The patent extracts and removes the anti-aliasing filter from the analog domain and replaces it with a digital equalizer that processes signals after ADC conversion. This allows the system to operate at lower sampling rates without introducing aliasing noise, as the equalizer compensates for the effects of undersampling in the digital domain rather than relying on analog filtering before conversion.
Solution Approach 2:
The patent substitutes the traditional analog anti-aliasing filter (mechanical/electrical system) with a digital equalizer (electronic/digital system). This replacement enables the system to achieve aliasing noise rejection without the complexity and cost of stringent analog filter specifications, while allowing operation at reduced sampling rates for lower power consumption.
2Use of energy by moving object
If ADC sampling rate is reduced from 2 SPS to 1.P SPS, then power consumption is reduced by approximately (2-1.P)/2, but aliasing noise is introduced because signal bandwidth exceeds Nyquist limit
Solution Approach 1:
The patent employs feedback mechanisms through adaptive equalizers (such as CMA or LMS algorithms) that continuously adjust equalization coefficients based on signal characteristics. This feedback allows the system to compensate for aliasing effects and maintain signal integrity even when operating at reduced sampling rates below the Nyquist limit.
Solution Approach 2:
The patent changes the parameter of equalization coefficients dynamically to adapt to varying signal conditions. By adjusting these coefficients in response to signal characteristics, the system can maintain optimal performance and signal integrity while operating at lower sampling rates, effectively managing the trade-off between power consumption and reliability.
3Reliability
If equalization coefficients are applied to all frequency components, then complete signal equalization is achieved, but computational complexity and power consumption increase
Solution Approach 1:
The patent segments the frequency spectrum into different components and applies equalization selectively rather than uniformly across all frequencies. By identifying and processing only the most critical frequency components, the system achieves adequate signal equalization while significantly reducing the number of complex multiplications required, thus lowering power consumption.
Solution Approach 2:
The patent applies partial equalization by selectively processing only the most significant frequency components rather than all components. This partial action approach provides sufficient signal quality improvement for practical purposes while reducing computational burden and power consumption, accepting that not all frequency components require full equalization treatment.
Data Source
AI summary
An optical receiver includes an equalizer to generate a plurality of equalization coefficients corresponding to a plurality of frequencies of an optical signal received by the optical receiver. The equalizer zeroes out a first subset of the equalization coefficients corresponding to a first subset of the plurality of frequency components and applies a second subset of non-zero equalization coefficients to the first signal. The optical receiver may also include a chromatic dispersion compensator to generate inverse chromatic dispersion coefficients corresponding to the plurality of frequency components, and to zero out a first subset of the inverse chromatic dispersion coefficients corresponding to the first subset of the plurality of frequency components and further to apply a second subset of non-zero inverse chromatic dispersion coefficients to a second optical signal.