Photonic Crystal Optical Sensor for Aerospace Structural Health Monitoring

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Solution Overview

Problem

Current optical interrogation systems for aerospace vehicles are costly, complex, and sensitive to environmental factors, making them unsuitable for robust and miniaturized structural health monitoring in harsh environments.

Innovation Solution

A photonic crystal-based optical sensor system with a single mode optical fiber and a photonic crystal mounted on its end face, which is simpler to manufacture and less sensitive to temperature changes, combined with a lightweight, failure-tolerant optical interrogation apparatus using MEMS switches and tunable semiconductor lasers for efficient data conversion and processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional optical sensors (Fabry-Perot, long-period grating, fiber Bragg grating) are used, then sensing capability is achieved, but the system becomes large, costly, and complex

Engineering Contradiction:

Improvesensing capabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and integrates the sensing function directly into the optical fiber itself through photonic crystal structures, eliminating the need for separate, bulky sensor components. This integration reduces system complexity while maintaining sensing capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The photonic crystal structure is nested within the optical fiber architecture, with the sensing functionality embedded inside the fiber structure. This nesting approach miniaturizes the overall system while preserving sensing performance.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If conventional optical sensors are used, then sensing function is provided, but cost increases and miniaturization is prevented

Engineering Contradiction:

Improvesensing functionVSAvoidsystem weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent merges the optical transmission function and sensing function into a single integrated fiber structure. This combination eliminates separate components, reducing weight and enabling miniaturization while maintaining full sensing functionality.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If Fiber Bragg Grating devices are used, then structural health monitoring is achieved, but temperature sensitivity requires additional compensation equipment

Engineering Contradiction:

Improvemonitoring capabilityVSAvoidcompensation equipment

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a reference optical fiber as an intermediary element that experiences the same temperature environment but does not carry the mechanical sensing function. This reference fiber mediates the temperature compensation by providing a baseline signal for comparison, eliminating the need for complex active compensation equipment.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If piezoelectric transducers are used, then sensing is achieved, but cost increases due to expensive materials and EMI susceptibility

Engineering Contradiction:

Improvesensing capabilityVSAvoidEMI susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces piezoelectric transducers with an all-optical sensing system based on photonic crystal structures in optical fibers. This substitution eliminates the mechanical and electrical components that are susceptible to EMI, while maintaining sensing capability through optical measurements of strain and pressure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

5Reliability

If strain gauges are used, then resistance change measurement is achieved, but installation and reading accuracy become difficult

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidinstallation ease

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent segments the sensing function into distributed photonic crystal structures along the optical fiber. This segmentation allows the sensing capability to be distributed throughout the structure being monitored, simplifying installation as the fiber can be routed along structural members without requiring separate gauge installations at multiple points.

Inventive Principle:

Principle #1Segmentation

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

The system provides a lightweight, miniaturized, and cost-effective solution for structural health monitoring in extreme environments, reducing complexity and sensitivity to temperature changes while maintaining high reliability and scalability for various sensing applications.

Implementation Method 1

a photonic crystal coupled to the terminating end surface of the optical fiber

Methodology Applied

Scientific EffectPhotonic crystal: Photonic Crystal

Data Source

PatentUS9772539B2Optical sensor and method of manufacture

Publication Date: 2017.09.26 THE BOEING CO

AI summary

An optical sensor and method of manufacture are provided herein. The optical sensor includes an optical fiber comprising a terminating end surface, and a photonic crystal coupled to the terminating end surface of the optical fiber.