Interleaved ADC Receiver with Channel-Dependent Equalization
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Solution Overview
Problem
Implementing 10G optical communication systems over multi-mode fibers is challenging due to high dispersion and variability, which requires complex and costly components, particularly high-speed analog-to-digital converters (ADCs), and existing solutions often compromise on cost or reliability.
Innovation Solution
A receiver with an interleaved ADC coupled to a multi-channel equalizer that uses a lookahead pipelined architecture, open-loop residue amplifiers, and adaptive calibration, along with a multi-channel equalizer based on feedforward equalization and Viterbi decoding, to compensate for channel-dependent impairments and variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed ADCs are used to achieve 10G optical communication, then data rate is improved, but device complexity and cost increase
Solution Approach 1:
The receiver is divided into multiple parallel sub-receivers, each operating at a lower clock rate (e.g., 1.25 GHz for 10G systems). Each sub-receiver includes its own ADC, equalizer, and detector operating independently. This segmentation allows the use of simpler, lower-speed ADCs while maintaining the overall 10G data rate through parallel processing.
Solution Approach 2:
The patent transitions from a single high-speed serial processing dimension to multiple parallel processing dimensions. By using N parallel sub-receivers instead of one high-speed receiver, the system achieves the same throughput through spatial parallelism rather than temporal speed, effectively adding a dimensional approach to solving the speed-complexity contradiction.
2Speed
If high-speed ADCs are used to achieve 10G optical communication, then data rate is improved, but cost increases
Solution Approach 1:
By segmenting the high-speed conversion task into multiple lower-speed ADCs, the patent reduces the cost of each individual ADC component. Lower-speed ADCs are more成熟 and less expensive to manufacture, and the parallel architecture allows using standard, cost-effective components rather than specialized high-speed devices.
Solution Approach 2:
The patent uses multiple copies of identical or similar sub-receiver modules, each with its own ADC. This copying approach allows mass production of standardized, lower-cost modules rather than custom high-speed components, reducing overall system cost through economies of scale and standardized manufacturing.
3Reliability
If complex components are used to compensate for dispersion and variability, then communication reliability is improved, but device complexity increases
Solution Approach 1:
The equalization function is segmented and distributed across multiple parallel equalizers, each operating at lower speed with simpler circuitry. Each sub-receiver's equalizer handles a portion of the dispersion compensation task, and the combined effect of all parallel equalizers achieves the required reliability without requiring any single component to be overly complex.
Solution Approach 2:
The patent employs adaptive equalization with feedback mechanisms in each sub-receiver, where the equalizer coefficients are continuously adjusted based on received signal quality. This feedback allows the system to adapt to channel variations and maintain reliability using relatively simple, adjustable components rather than complex fixed-design components.
Data Source
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AI summary
A receiver (e.g., for a 1OG fiber communications link) includes an interleaved ADC coupled to a multi-channel equalizer that can provide different equalization for different ADC channels within the interleaved ADC. That is, the multi-channel equalizer can compensate for channel-dependent impairments. In one approach, the multi-channel equalizer is a feedforward equalizer (FFE) coupled to a Viterbi decoder, for example a sliding block Viterbi decoder (SBVD); and the FFE and/or the channel estimator for the Viterbi decoder are adapted using the LMS algorithm.