Optical Transceiver Bias Line Layout for EMI-Resistant Reception

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Solution Overview

Problem

High-density optical transceivers with multiple channels suffer from electromagnetic interference (EMI) noise due to closely arranged signal lines, which degrades the sensitivity of optical receivers, particularly when large currents are switched near faint signal lines.

Innovation Solution

The optical transceiver incorporates a bias supply system with RC filters and a specific arrangement of internal and external bias lines, including a shorter first internal bias line connected to a filter unit with a resistor and capacitor, and additional filter units with capacitors and resistors to effectively eliminate EMI noise, while a dummy line is used to further shield bias lines from noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If signal lines for optical transmitter and receiver are closely disposed to achieve high density assembly, then device integration is improved, but electromagnetic interference noise increases

Engineering Contradiction:

Improvedensity of component assemblyVSAvoidEMI noise affecting receiver sensitivity

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

A ground line is introduced as an intermediary element positioned between the transmitter signal line and receiver signal line. This ground line acts as a shield to block electromagnetic interference from the transmitter side from affecting the receiver side, while maintaining the high-density assembly configuration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The signal transmission paths are segmented into distinct regions with different impedance characteristics. By dividing the transmission line structure and introducing ground references at specific segments, the patent creates isolated zones that prevent EMI propagation while maintaining signal integrity for high-density integration.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If multiple bias lines are provided for multiple photodiodes, then multi-channel reception capability is improved, but EMI noise propagation between channels increases

Engineering Contradiction:

Improvemulti-channel reception capabilityVSAvoidEMI noise generated by bias lines affecting other channels

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The harmful EMI noise component is extracted and directed to a dedicated ground line separate from the signal-carrying bias lines. By separating the noise path from the signal paths, each channel's bias line can maintain its function without interfering with other channels, enabling multi-channel operation with reduced mutual interference.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Ground lines are positioned as intermediary elements between adjacent bias lines for different channels. These ground lines serve as shields that prevent EMI noise generated by one channel's bias line from coupling into neighboring channels, thereby maintaining signal integrity across multiple channels.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If capacitors are inserted in bias lines to eliminate noises, then receiver sensitivity is improved, but device complexity and component count increase

Engineering Contradiction:

Improvereceiver sensitivityVSAvoidnumber of components in bias line circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of adding multiple capacitors to each bias line, the patent uses ground lines as intermediary shield elements. This approach achieves noise elimination through electromagnetic shielding rather than through RC filtering components, thereby improving receiver sensitivity without significantly increasing device complexity or component count.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This configuration reduces EMI radiation between bias lines, enhancing the sensitivity of the optical receiver by minimizing noise interference and maintaining signal integrity across multiple channels.

Implementation Method 1

The first internal bias line includes a first filter unit having a resistor and a capacitor which constitute a first RC filter. The other internal bias lines include other filter units each having a resistor and a capacitor constituting RC filters.

Methodology Applied

Scientific EffectRC filtering: Filter (electronic)

Implementation Method 2

The optical receiver module de-multiplexes the other wavelength multiplexed signal into receiving optical signals, and converts the receiving optical signals into receiving signals by photodiodes (PDs).

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS9768872B2Optical transceiver outputting wavelength multiplexed signal and receiving another wavelength multiplexed signal

Publication Date: 2017.09.19 SUMITOMO ELECTRIC INDUSTRIES LTD

AI summary

An optical transceiver that provides a receiver optical module including a plurality photodiodes (PDs) each biased through internal bias lines, signal lines carrying driving signals to an optical transmitter module, and external bias lines each connected to the internal bias lines. One of the internal bias lines connected to one of the external bias lines arranged closest to the signal lines has a length shorter than lengths of the other internal bias lines so as not to affect EMI noises induced from the signal lines to the other internal bias lines.