Modulator Drive Circuit Adjustable Bias Voltage Control

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Solution Overview

Problem

Existing modulator drive circuits have high component counts, large size, and thermal issues due to high power dissipation, especially when integrated on a single substrate, and require separate DC bias signals and bias tee circuits, which restricts integration and increases transmission line effects.

Innovation Solution

A modulator drive circuit with adjustable voltage supply that eliminates the need for a separate DC bias signal, using a variable or adjustable voltage to bias the modulator drive circuitry, allowing for integration of multiple circuits on a single substrate with reduced size and power consumption, and incorporating a controller for AC component amplitude control via a digital serial interface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bias circuit is provided in the signal path of the modulator driver output, then the modulator can be biased to ensure efficient modulation, but the component count increases and the physical size becomes large

Engineering Contradiction:

Improvemodulator bias controlVSAvoidcomponent count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the bias control functionality directly into the modulator driver circuit by providing a second output that generates the bias voltage. This merging eliminates the need for separate external bias circuits (capacitors, inductors, and resistors), thereby reducing component count while maintaining reliable modulator bias control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The modulator driver is designed to perform multiple functions: it generates both the main output signal for modulation and the bias voltage signal simultaneously. This multi-functionality eliminates the need for separate bias circuitry, reducing both component count and physical size while ensuring proper modulator operation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a bias circuit with capacitor and inductor is provided, then the modulator bias can be controlled, but the physical size of the circuit becomes large

Engineering Contradiction:

Improvemodulator bias controlVSAvoidcircuit physical size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The bias control functionality is merged into the modulator driver circuit itself, eliminating the need for separate external bias components (capacitors, inductors, and resistors) that would occupy significant physical space on the substrate.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts and eliminates the bulky passive components (capacitors and inductors) from the signal path by implementing bias control through active circuitry within the modulator driver, thereby significantly reducing the physical footprint of the overall circuit.

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If multiple modulator drive circuits are integrated on a single substrate, then network carrying capacity increases, but the transmission line effects increase due to longer signal paths

Engineering Contradiction:

Improvenetwork carrying capacityVSAvoidtransmission line effects

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent removes the external bias circuit components from the signal path, allowing the modulator driver to be positioned closer to the modulator without requiring long transmission lines for bias signal delivery, thereby reducing transmission line effects.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If a bias tee circuit is provided in the signal path, then the modulator can be biased, but the integration of multiple circuits on a single substrate is restricted

Engineering Contradiction:

Improvemodulator bias controlVSAvoidintegration capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The bias control functionality is merged into the modulator driver circuit itself, eliminating the need for separate external bias circuits. This integration enables multiple modulator drive circuits to be fabricated on a single substrate without requiring external bias tee components, thereby enhancing scalability and integration capability.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7848369B1Optical modulator drive circuit with integrated low power output bias voltage control

Publication Date: 2010.12.07 INFINERA CORP

AI summary

A modulator drive circuit provides a modulator drive signal to modulate an optical signal for transport across a network infrastructure. The modulator drive circuit powered by an adjustable voltage source, such that the modulator drive signal is generated from a data signal and the adjustable voltage source, an AC component of the modulator drive signal being derived from the data signal while a DC component of the modulator drive signal being derived from the adjustable voltage source. An array of such modulator drive circuits are provided on a single substrate.