Wavelength Dispersion Compensation Circuit Design

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Solution Overview

Problem

Current methods for estimating and compensating wavelength dispersion in optical fiber transmission systems are inefficient, requiring long setup times and prone to errors due to variations in accumulative dispersion and interference from polarization mode dispersion, leading to increased error rates and reduced reliability.

Innovation Solution

A method involving iterative adjustments of dispersion compensation amounts based on digital clock signal strength measurements, shifting the compensation amount in both positive and negative directions, and averaging clock detection values to determine the optimal compensation setting, allowing for rapid and accurate estimation of wavelength dispersion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional wavelength dispersion estimation methods are used, then the system can detect dispersion amounts, but the setup time becomes excessively long and error rates increase

Engineering Contradiction:

Improvewavelength dispersion estimation accuracyVSAvoidsetup time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-calculating and storing dispersion compensation filter coefficients for various dispersion amounts before actual communication begins. During setup, the system only needs to estimate the dispersion amount and retrieve the pre-computed coefficients, avoiding time-consuming real-time calculations and reducing setup time while maintaining accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical adjustment mechanisms with digital signal processing. Instead of physically adjusting filters or components, the system uses digital algorithms to estimate dispersion amounts and applies corresponding digital filter coefficients, significantly reducing setup time and improving precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If dispersion compensation is adjusted to improve accuracy, then measurement precision improves, but the system complexity increases

Engineering Contradiction:

Improvedispersion compensation accuracyVSAvoidcompensation circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the dispersion compensation process into distinct functional modules: dispersion amount estimation module, coefficient selection module, and compensation filter application module. This segmentation allows each module to perform its specific function efficiently without requiring the entire system to be complex, simplifying the overall device architecture while maintaining accuracy

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the approach from adjusting physical filter parameters to changing digital coefficient parameters. By storing multiple sets of filter coefficients corresponding to different dispersion amounts and selecting the appropriate set based on estimated dispersion, the system achieves high compensation accuracy without complex physical adjustments

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If exhaustive search methods are used to find optimal compensation, then measurement precision improves, but productivity decreases

Engineering Contradiction:

Improveoptimal compensation detection accuracyVSAvoidsystem setup speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent implements feedback by using the estimated dispersion amount to select appropriate pre-computed filter coefficients. The system continuously monitors communication quality and adjusts the selected coefficient set based on feedback regarding actual dispersion conditions, achieving optimal compensation efficiently without exhaustive searching

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary computation of dispersion compensation filter coefficients for various dispersion scenarios before actual operation. This pre-computation eliminates the need for time-consuming exhaustive searches during setup, as the system only needs to estimate the current dispersion amount and retrieve the corresponding pre-computed coefficients, significantly improving productivity

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8971703B2Wavelength dispersion amount estimation method, wavelength dispersion compensation circuit, and reception device

Publication Date: 2015.03.03 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

A wavelength dispersion amount estimation method, a wavelength dispersion compensation circuit, and a receiving device which rapidly estimate and set a wavelength dispersion amount to compensate with high accuracy at the receiving device which compensates waveform distortion at an optical fiber transmission path. The wavelength dispersion compensation circuit includes an analog-digital converter which converts an optical analog waveform received from the optical fiber transmission path to a digital signal, a digital signal processor which compensates waveform distortion of the digital signal output from the analog-digital converter due to wavelength dispersion at the optical fiber transmission path with a dispersion compensation amount estimated with the wavelength dispersion amount estimation method, and a symbol clock extractor which extracts a symbol arrival timing clock of received data contained in the digital signal output from the analog-digital converter and outputs strength of the symbol arrival timing clock as the clock detection value.