Non-linear FIR Filter Pre-compensation for DML Distortion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Directly Modulated Lasers (DMLs) like Vertical Cavity Surface Emitting Lasers (VCSELs) face performance limitations at higher data rates due to distortion, which reduces signal-to-noise ratio and limits transmission distances, as conventional linear filters fail to provide optimal compensation for the non-linear distortion introduced by these devices.

Innovation Solution

A non-linear finite impulse response (FIR) filter is used to pre-compensate the drive current for DMLs, employing multiple taps with adjustable weights and biasing circuits to address the non-linear distortion, allowing for efficient and compact analogue hardware implementation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If linear filters are used to compensate for distortion, then some distortion compensation is achieved, but optimal compensation for non-linear distortion is not achieved

Engineering Contradiction:

Improvesignal qualityVSAvoiddistortion compensation accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent transforms the linear filter parameters into non-linear parameters by applying a non-linear transformation function to the filter coefficients. This allows the filter to adapt its response characteristics dynamically, enabling optimal compensation for non-linear distortion while maintaining signal quality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional linear filtering mechanism with a non-linear filtering mechanism that uses non-linear transformation functions. This substitution enables the system to handle non-linear distortion more effectively than traditional linear approaches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If DML operates at higher data rates, then data throughput increases, but distortion increases limiting transmission distance

Engineering Contradiction:

Improvedata rateVSAvoiddistortion

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by using the non-linear filter to pre-compensate for distortion before the signal is transmitted through the DML. The filter predicts and counteracts the non-linear distortion effects in advance, allowing higher data rates to be achieved without the harmful distortion limiting transmission distance.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS11664639B2Device having non-linear filter

Publication Date: 2023.05.30 SEMTECH CANADA

AI summary

A circuit is disclosed having a component having repeatable distortion characteristics; and a drive circuit for providing a drive signal and comprising a non-linear filter for pre-compensating for distortion introduced by the component having repeatable distortion characteristics in response to the drive signal, the distortion having a non-linear response to the drive signal.