Optical Fiber Moisture Sensor Using Lossy-Mode Resonance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrical sensors are prone to electromagnetic interference and cannot operate effectively in high temperature or microwave environments, limiting their ability to accurately measure moisture and humidity, especially in industrial settings like food processing where they are often needed.
Innovation Solution
A fiber optical moisture sensing device with a side-polished optical fiber coated with a 200-nm metal dioxide layer, specifically tin oxide, that uses lossy-mode resonance to detect moisture levels, providing real-time measurements immune to electromagnetic interference and capable of withstanding high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electrical sensors are used for moisture sensing, then ease of use and signal interpretation are improved, but electromagnetic interference from ambient waves and motors reduces measurement faithfulness or makes measurement impossible
Solution Approach 1:
The patent replaces electrical sensing mechanisms with optical sensing mechanisms. Specifically, it uses an optical fiber with a side-polished surface and a metal oxide coating that interacts with moisture, detecting changes through optical properties rather than electrical signals. This substitution eliminates susceptibility to electromagnetic interference while maintaining sensing capability.
Solution Approach 2:
The patent introduces an optical fiber as an intermediary medium between the sensing target and the detection system. The optical fiber transmits light signals that interact with the metal oxide coating and moisture, converting environmental interactions into optical signals that are immune to electromagnetic interference, thus preserving measurement faithfulness.
2Reliability
If electrical sensors are deployed in harsh environments, then sensing capability is maintained, but high heat and corrosive environments reduce sensor survival and reading accuracy
Solution Approach 1:
The patent employs a composite structure consisting of an optical fiber core with a metal oxide coating layer. The optical fiber provides mechanical strength and environmental resistance, while the metal oxide coating (such as tin oxide or zinc oxide) provides selective interaction with moisture and resistance to harsh chemical environments. This composite approach enables operation in high heat and corrosive conditions.
Solution Approach 2:
The patent utilizes changes in optical parameters (wavelength, intensity) in response to environmental conditions. The metal oxide coating's optical properties change when exposed to moisture, allowing detection through optical spectrum analysis. This parameter-based detection method maintains sensing capability across varying temperature and environmental conditions.
3Reliability
If optical fiber sensors are used to achieve electromagnetic immunity, then measurement faithfulness in microwave environments is improved, but device complexity increases due to specialized coating and polishing requirements
Solution Approach 1:
The patent employs a porous metal oxide coating structure that enhances moisture interaction while maintaining a relatively simple fabrication process. The porous structure increases surface area for moisture adsorption, improving sensitivity without requiring complex device architecture. This approach balances electromagnetic immunity with manufacturing simplicity.
4Ease of operation
If conventional electrical sensors are used in food processing, then ease of operation is maintained, but microwave sources and metal structures interfere with sensing signals
Solution Approach 1:
The patent replaces electrical sensing with optical sensing, using light propagation through an optical fiber as the sensing mechanism. Since optical signals are not affected by microwave radiation or magnetic fields from metal structures, the sensor can operate reliably in food processing environments with microwave sources and metal equipment, while maintaining ease of operation through straightforward optical detection.
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 optical fiber sensor offers high sensitivity and robustness, enabling accurate moisture and humidity measurements in harsh environments, including those with microwave interference, and can be used in narrow spaces, addressing the limitations of conventional electrical sensors.
Implementation Method 1
A fiber optical moisture sensing device includes an optical fiber having a side-polished end defining a flat sensory sidewall coated with an around 200-nm metal dioxide layer that support a special optical mode called a lossy mode resonance (LMR) coating
Implementation Method 2
A reflective coating on an end face of the optical fiber serves as a mirror and reflects the optical signal in the same fiber
Implementation Method 3
the LMR wavelength shifts provide measurements of the moisture around the tip of the fiber
Data Source
AI summary
A fiber optic sensing device includes an optical fiber having a polished end defining a flat sensory portion coated with a lossy-mode-resonance (LMR) coating. A reflective coating on an end face of the optical fiber facilitates propagation of a return signal. An optic circuit for identifies a wavelength attenuated by the LMR coating from the return signal reflected by the reflective coating based on a moisture presence at the sensory portion. Various gaseous parameters may be detected based on the coating on the sensory portion. An LMR coating of tin oxide (SnO2) is employed for moisture sensing.