Differential Signal Coupling Module for Common-Mode Voltage Matching

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Solution Overview

Problem

Existing methods for coupling optical transceivers and processing modules in optical communication devices face issues with common mode voltage mismatch, leading to inefficiencies such as capacitive coupling not providing appropriate DC response and bus transceivers introducing jitter, and are not adaptable to different types of optical transceivers.

Innovation Solution

A coupling module that splits differential signals into high-pass and low-pass filters, with op-amp based low-pass filters adjusting common mode voltage and feedback circuits ensuring compatibility across varying input voltages, while maintaining signal integrity and bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If capacitive coupling is used to shift common mode voltage, then voltage level compatibility is achieved, but DC response is inadequate and burst mode operation fails

Engineering Contradiction:

Improvevoltage level compatibilityVSAvoidDC response and burst mode operation

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The signal path is segmented into multiple parallel channels: a capacitive coupling path for AC signal transmission and a resistive path for DC signal transmission. This segmentation allows each path to handle specific signal components appropriately, with the capacitive path handling AC coupling and the resistive path maintaining DC levels, thereby resolving the contradiction between voltage compatibility and DC response reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A resistive path is introduced as an intermediary element to work in parallel with the capacitive coupling path. This intermediary provides a direct DC signal transmission channel that bypasses the limitations of capacitive coupling, enabling both AC signal transfer and proper DC level maintenance simultaneously

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If bus transceivers are used to shift common mode voltage, then voltage level compatibility is achieved, but signal jitter is introduced

Engineering Contradiction:

Improvevoltage level compatibilityVSAvoidsignal jitter

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The active bus transceiver mechanism is replaced with a passive resistive path that operates in parallel with the capacitive coupling path. This substitution eliminates the active components that generate jitter while maintaining the voltage level shifting function through passive voltage division and signal combining, thereby resolving the contradiction between voltage compatibility and signal quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If fixed coupling method is used, then simple implementation is achieved, but adaptability to different optical transceiver types is lost

Engineering Contradiction:

Improveimplementation simplicityVSAvoidcompatibility with different transceiver types

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The coupling module is designed with a universal parallel architecture combining capacitive and resistive paths that can accommodate multiple types of optical transceivers. This multi-functional design allows the same circuit structure to handle different voltage levels and signal characteristics from various transceiver types without requiring redesign, resolving the contradiction between implementation simplicity and adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 jitter-free, high-speed signal transmission with compatible common mode voltage levels, supporting a wide range of input voltages and types of optical transceivers.

Implementation Method 1

The coupling module includes a high-pass filter and a low-pass filter

Methodology Applied

Scientific EffectHigh-pass filter: Filter (electronic)

Implementation Method 2

The coupling module includes a high-pass filter and a low-pass filter

Methodology Applied

Scientific EffectLow-pass filter: Filter (electronic)

Implementation Method 3

op-amp based low-pass filters adjusting common mode voltage

Methodology Applied

Scientific EffectOperational amplifier:

Data Source

PatentEP3991003B1Systems and methods for communicating high speed signals in a communication device

Publication Date: 2025.10.22 ADTRAN INC

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AI summary

A coupling module can be used to communicate high speed signals between an optical transceiver and a processing module of an optical communication device, such as an optical line termination (OLT) or an optical network unit (ONU). The coupling module can adjust the common mode voltage level of a differential signal output by the optical transceiver to the common mode voltage level required by the processing module. In addition, the coupling module splits each of the differential output signals from the optical transceiver and passes the split signals to both a high-pass filter and a low-pass filter that are connected in parallel. The outputs of the high-pass filter and the low-pass filter from different paths of the differential signal are cross-coupled and combined to provide a differential signal to the processing module.