ADC Sampling Rate Adjustment for Coherent Optical Signal Integrity

Solution Overview

Problem

High-speed optical communication systems face challenges in maintaining signal integrity due to increased bandwidth and complex modulation formats, particularly in sampling and processing high-frequency data streams, where existing methods either lead to aliasing effects or require excessive processing power and size.

Innovation Solution

The implementation of analog-to-digital converters (ADCs) sampling analog data streams at a rate nominally twice or greater than the symbol rate, followed by digital filtering to output filtered streams at an effective sampling rate less than the sampling rate but greater than or equal to the symbol rate, mitigates aliasing while reducing processing demands, using digital filters to achieve this without the need for analog anti-aliasing filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ADCs sample analog data streams at a rate twice or greater than the symbol rate, then aliasing effects are mitigated, but processing power and system size increase

Engineering Contradiction:

Improvesignal integrityVSAvoidprocessing power

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies preliminary action by performing digital filtering after ADC sampling to reduce the sampling rate before subsequent processing. The digital filter removes aliasing components introduced by the high-rate sampling, allowing the system to maintain signal integrity while reducing the burden on downstream processors. This preliminary filtering action enables efficient downsampling without losing critical signal information.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the sampling rate parameter dynamically through digital filtering. After initial high-rate sampling at twice the symbol rate or greater, the system applies digital filtering to effectively reduce the sampling rate to just above the symbol rate for subsequent processing. This parameter transformation maintains the benefits of high-rate sampling while eliminating the need for all downstream components to operate at the higher rate.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If ADCs sample analog data streams at a rate twice or greater than the symbol rate, then aliasing effects are mitigated, but system size increases

Engineering Contradiction:

Improvesignal integrityVSAvoidsystem size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent applies preliminary action by performing digital filtering after ADC sampling to reduce the sampling rate before subsequent processing. The digital filter removes aliasing components introduced by the high-rate sampling, allowing the system to maintain signal integrity while reducing the burden on downstream processors. This preliminary filtering action enables efficient downsampling without losing critical signal information.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the sampling rate parameter dynamically through digital filtering. After initial high-rate sampling at twice the symbol rate or greater, the system applies digital filtering to effectively reduce the sampling rate to just above the symbol rate for subsequent processing. This parameter transformation maintains the benefits of high-rate sampling while eliminating the need for all downstream components to operate at the higher rate.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If digital filtering is applied to reduce effective sampling rate, then processing load is reduced, but aliasing effects may increase

Engineering Contradiction:

Improveprocessing efficiencyVSAvoidaliasing effects

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by performing digital filtering after ADC sampling to reduce the sampling rate before subsequent processing. The digital filter removes aliasing components introduced by the high-rate sampling, allowing the system to maintain signal integrity while reducing the burden on downstream processors. This preliminary filtering action enables efficient downsampling without losing critical signal information.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful aliasing effects into a beneficial filtering opportunity. By intentionally sampling at a rate that introduces aliasing (twice the symbol rate or greater), the system creates predictable spectral images that can be cleanly removed by subsequent digital filtering. The aliasing components become identifiable artifacts that the digital filter can eliminate, leaving only the desired signal band.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentEP3136624B1Processing data in a coherent optical communication system

Publication Date: 2018.12.12 JUNIPER NETWORKS INC

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AI summary

This disclosure describes techniques to sample electrical data streams in coherent receivers. For instance, an analog-to-digital converter (ADC) samples the received electrical data stream at a sampling rate that is nominally twice or greater than twice the symbol rate of the electrical data stream that the ADC receives. A digital filter receives the digital data stream from the ADC, and digitally filters the digital data streams to output a filtered digital electrical data stream at an effective sampling rate that is less than the sampling rate and less than twice the symbol rate, and greater than or equal to the symbol rate.