Coherent Receiver Chromatic Dispersion Estimation via Clip Rate

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Solution Overview

Problem

Existing coherent optical transmission schemes face challenges in estimating chromatic dispersion without transmitting or receiving a training signal sequence, particularly when the baud rate and modulation format are unknown, leading to increased costs and reduced throughput.

Innovation Solution

A reception apparatus and method that utilize a dispersion compensation unit, clip rate measurement unit, and control unit to estimate chromatic dispersion by varying compensation amounts and measuring clip rates, allowing for optimal compensation without prior knowledge of signal parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If digital signal processing is used to compensate for chromatic dispersion, then signal quality is improved, but device complexity increases due to the need for measuring instruments or advanced parameter analysis

Engineering Contradiction:

Improvesignal qualityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The receiving apparatus performs self-diagnosis by autonomously estimating chromatic dispersion amount through clip rate measurement of received signals, eliminating the need for external measuring instruments or complex training sequences. The system serves itself by using the received signal characteristics to determine compensation parameters.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces physical measuring instruments and complex training sequence transmission with a digital signal processing method that uses clip rate analysis. This substitutes hardware-based measurement systems with a software-based estimation approach that is simpler and more integrated.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If training signal sequences are transmitted for chromatic dispersion estimation, then measurement precision is improved, but productivity decreases due to reduced throughput

Engineering Contradiction:

Improvechromatic dispersion estimation accuracyVSAvoidthroughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The system continuously estimates chromatic dispersion using the received signal itself without interrupting data transmission for training sequences. The clip rate measurement is performed on ongoing communication signals, maintaining continuous useful action and maximizing throughput while achieving accurate dispersion estimation.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The received signal serves multiple functions: it is both the data being transmitted and the measurement probe for chromatic dispersion estimation. The same signal carries both information and diagnostic functionality, eliminating the need for separate training sequences.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If dispersion compensation is performed without knowing baud rate and modulation format, then adaptability is improved, but measurement precision deteriorates

Engineering Contradiction:

Improveadaptability to unknown signal parametersVSAvoidchromatic dispersion estimation accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from baud rate or modulation format-dependent metrics to clip rate, which is independent of these parameters. By measuring the proportion of clipped samples in the received signal, the system achieves parameter-independent chromatic dispersion estimation that works across different signal configurations.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables accurate estimation and compensation of chromatic dispersion without the need for training sequences or prior knowledge of baud rate and modulation format, reducing costs and improving transmission efficiency.

Implementation Method 1

coherent reception is performed on a receiving side... converts the received light into an electrical signal by using a photoelectric conversion element such as a photodiode

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

coherent reception is an optical reception scheme that uses a local oscillation light source to cause received light and local oscillation light to interfere with each other

Methodology Applied

Scientific EffectCoherent interference: Interference

Data Source

PatentUS11258512B2Receiving apparatus and receiving method

Publication Date: 2022.02.22 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

A reception apparatus includes a dispersion compensation unit configured to acquire an electrical signal resulting from conversion of an optical signal and perform, on the electrical signal, dispersion compensation with a predetermined compensation amount, a clip rate measurement unit configured to measure a clip rate for the electrical signal subjected to the dispersion compensation, and a control unit configured to detect the compensation amount that minimizes the clip rate.