DPSK Demodulator Phase Control with Piezo and Thermal Units

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Solution Overview

Problem

Conventional optical communication systems using DPSK demodulators face challenges with slow optical phase modulation speeds, leading to long system activation times and reduced interferometer lifetime due to the limitations of temperature control and Piezo actuator degradation.

Innovation Solution

A DPSK signal demodulator is designed with a combination of a Piezo actuator for fast optical phase modulation and a silicon monocrystal or other phase modulation units like liquid crystals or expanding components, allowing for rapid phase adjustments while minimizing power consumption and extending the interferometer's lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If temperature control is used for optical phase modulation, then the interferometer can maintain stable operation, but the system activation time becomes very long

Engineering Contradiction:

Improvestable operationVSAvoidsystem activation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The optical phase modulation function is segmented into two independent units: a first optical phase modulation unit (Piezo actuator) for fast activation and a second optical phase modulation unit (temperature control) for stable operation. This segmentation allows each unit to specialize in one aspect, resolving the contradiction between speed and stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between two phase modulation mechanisms based on operational phase: during activation, the Piezo actuator provides rapid phase adjustment, while during normal operation, temperature control maintains stability. This dynamic approach optimizes performance across different operational states.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If Piezo actuator is used for optical phase modulation, then the system activation time is shortened, but the interferometer lifetime is reduced due to actuator degradation

Engineering Contradiction:

Improvesystem activation timeVSAvoidinterferometer lifetime

Core Design Contradiction:

Loss of timeVSDuration of action of stationary object

Solution Approach 1:

The Piezo actuator is activated periodically only during system initialization and wavelength switching events, rather than continuously. This periodic usage pattern minimizes wear and degradation of the actuator while still providing the fast response needed for activation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The phase modulation function is divided between two units with different operational characteristics. The Piezo actuator handles fast, intermittent adjustments during activation, while the temperature-controlled unit handles continuous, stable operation, thereby protecting the Piezo actuator from continuous degradation.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If a single optical phase modulation unit is used, then the device complexity is reduced, but the system cannot achieve both fast activation and long lifetime

Engineering Contradiction:

Improvenumber of phase modulation unitsVSAvoidsystem activation time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The phase modulation function is segmented into two specialized units rather than using a single general-purpose unit. This segmentation enables each unit to be optimized for its specific function, achieving both fast activation and long lifetime despite the increased component count.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the operational parameters of different phase modulation units based on the operational phase: during activation, the Piezo actuator operates at high speed with large phase shifts, while during normal operation, the temperature-controlled unit operates at stable, low-speed conditions. This parameter optimization justifies the dual-unit architecture.

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

This configuration enables fast optical phase modulation during system activation and maintains a long interferometer lifetime by using a Piezo actuator for initial rapid adjustments and slower, less deteriorating phase modulation units for continuous operation, reducing activation time and extending the system's operational lifespan.

Implementation Method 1

adjustment of phase difference between the first and second split lights is performed by using a first phase adjust means such as a Piezo actuator

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a second optical phase modulation unit such as a silicon monocrystal which operates slower than the first optical phase modulation unit

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8861982B2Interferometer, demodulator, and optical communication module

Publication Date: 2014.10.14 CAMBRIDGE IND USA INC

AI summary

When designing a demodulator for a DPSK-modulated signal, it is required that optical phase modulation is performed fast and the demodulator has a long lifetime. To achieve this object, a delay line interferometer inside the demodulator performs adjustment of phase difference between two split lights caused to interfere, using a first optical phase modulation unit such as a Piezo actuator and a second optical phase modulation unit such as a heating element that operates slower in modulation speed than the first optical phase modulation unit and is slower in deterioration speed.