Phase Quadrature Four-Wavelength Demodulation for F-P Cavity Sensors
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Solution Overview
Problem
Current optical fiber F-P cavity sensor demodulation methods, such as single-wavelength, dual-wavelength, and three-wavelength demodulation, face limitations in precision, stability, and cost, particularly in real-time demodulation of dynamic variables, with phase demodulation being costly and slow.
Innovation Solution
A phase quadrature four-wavelength demodulation system using a flat ASE broadband light source, optical fiber circulator, dense wavelength division multiplexer, and photoelectric detector, which decomposes reflected light into four narrowband beams for precise cavity length change measurement, reducing system cost and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase demodulation method is used, then demodulation precision and stability are improved, but system cost increases and measurement speed decreases
Solution Approach 1:
The broadband light source spectrum is segmented into multiple wavelength bands using a wavelength division multiplexer, with each band processed by dedicated photodetectors. This segmentation allows parallel processing of different wavelength components, achieving high-precision phase demodulation through multi-wavelength interference patterns while avoiding the need for expensive swept-source equipment.
Solution Approach 2:
The patent replaces the mechanical swept-source phase demodulation system with a static multi-wavelength detection system. Instead of mechanically sweeping through wavelengths sequentially, the system uses a wavelength division multiplexer to simultaneously route multiple fixed wavelength bands to parallel photodetectors, substituting mechanical movement with optical circuit routing.
2Measurement precision
If phase demodulation method is used, then demodulation precision is improved, but measurement speed decreases
Solution Approach 1:
The broadband light source continuously emits across the entire wavelength range simultaneously, and the wavelength division multiplexer continuously routes all wavelength bands to photodetectors in parallel. This continuous parallel operation eliminates the sequential scanning process, maintaining uninterrupted measurement and improving real-time detection capability while preserving high precision through multi-wavelength interference analysis.
Solution Approach 2:
The system uses periodic modulation of the broadband light source or reference signal to enable synchronous detection at each wavelength channel. By modulating at distinct frequencies and using lock-in detection, the system can rapidly extract phase information from each wavelength band simultaneously, achieving high-speed precision measurement through frequency-domain multiplexing.
3Measurement precision
If three-wavelength demodulation using three laser light sources is used, then demodulation capability is improved, but device complexity and cost increase
Solution Approach 1:
A single broadband light source performs the function of multiple narrowband laser sources by providing continuous spectral coverage that is then divided into multiple wavelength bands. The wavelength division multiplexer acts as a universal routing component that distributes signals to multiple photodetectors, replacing the need for multiple specialized laser sources and reducing overall system complexity while maintaining multi-wavelength demodulation capability.
Solution Approach 2:
The patent merges multiple wavelength sources into a single broadband light source, and merges multiple detection channels into a unified photodetector array system. By combining the spectral output of one broadband source and using a wavelength division multiplexer to route different wavelength bands to parallel detectors, the system achieves three-wavelength (or more) demodulation with fewer physical components than using three separate laser sources.
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 achieves improved demodulation precision and stability with reduced costs and technical complexity, enabling a larger dynamic range of adjustable cavity length and real-time measurement of external environment changes.
Implementation Method 1
a flat amplified spontaneous emission (ASE) broadband light source
Implementation Method 2
the optical fiber F-P cavity sensor is configured to generate reflected light
Implementation Method 3
the dense wavelength division multiplexer is configured to decompose the received reflected light into four beams of narrowband light of different wavelengths
Implementation Method 4
the photoelectric detector is configured to perform a photoelectric conversion on the four beams of narrowband light of different wavelengths
Data Source
AI summary
Provided are a phase quadrature four-wavelength demodulation system and method of an optical fiber F-P cavity sensor. The phase quadrature four-wavelength demodulation system of the optical fiber F-P cavity sensor includes a flat ASE broadband light source, an optical fiber circulator, a dense wavelength division multiplexer, a photoelectric detector, and a data acquisition processing unit. The flat ASE broadband light source is connected to the optical fiber circulator, the optical fiber circulator is connected to the dense wavelength division multiplexer, the dense wavelength division multiplexer is connected to the photoelectric detector, and the photoelectric detector is connected to the data acquisition processing unit.