Optical Fiber Humidity Sensor Using Brillouin and Rayleigh Shifts
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Solution Overview
Problem
Conventional humidity measurement systems in agriculture face challenges in achieving distributed and real-time measurement over large areas due to issues like heat generation from electric sensors, long measurement times, and interference from temperature changes in optical fiber-based methods.
Innovation Solution
A monitoring humidity measurement system using an optical fiber with a humidity detection layer and a reference optical fiber, coupled with an optical signal processing device to calculate Brillouin and Rayleigh frequency shifts, allowing for the separation of humidity changes from temperature influences and enabling rapid frequency shift measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric sensors are used for humidity measurement, then measurement capability is provided, but heat generation in electric wires influences environmental variables and power supply is needed
Solution Approach 1:
The patent replaces electric sensors with optical fiber-based sensing technology. The optical fiber measures humidity through changes in light propagation characteristics (refractive index, attenuation) caused by water vapor absorption, eliminating the need for electric wires and power supplies while avoiding heat generation issues associated with electric sensors.
Solution Approach 2:
The patent introduces an intermediary substance (hygroscopic material or water-soluble polymer coating) on the optical fiber that mediates the interaction between humidity and the measurement system. This intermediary absorbs water vapor from the environment, causing measurable optical changes without requiring direct contact between the optical fiber and the humid environment, thus protecting the fiber while enabling measurement.
2Adaptability or versatility
If optical fiber with hygroscopic material is used for humidity measurement, then distributed measurement is enabled, but measurement time is long (four to ten hours to reach saturation)
Solution Approach 1:
The patent changes the physical or chemical parameters of the hygroscopic material or polymer coating to optimize the measurement response time. By adjusting parameters such as material composition, coating thickness, or polymer properties, the system achieves faster response to humidity changes while maintaining distributed measurement capability through optical fiber deployment.
3Adaptability or versatility
If optical fiber measurement is used, then distributed measurement is enabled, but temperature change influences measurement and separation from humidity effect is difficult
Solution Approach 1:
The patent segments the measurement function into separate components: one for humidity detection and another for temperature detection. By using multiple optical fibers or multiple sensing regions with different characteristics, the system independently measures both humidity and temperature effects, allowing mathematical separation of the humidity signal from the temperature interference to improve measurement precision.
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 system enables distributed and real-time humidity measurement over large areas by eliminating temperature interference and shortening measurement times, facilitating precise and efficient agricultural data collection.
Implementation Method 1
calculate and obtain Brillouin frequency shift and Rayleigh frequency shift from backscatter light of a laser beam entering from the laser light source into each optical fiber
Implementation Method 2
calculate and obtain Brillouin frequency shift and Rayleigh frequency shift from backscatter light of a laser beam entering from the laser light source into each optical fiber
Implementation Method 3
a humidity measurement optical fiber including a first optical fiber and a humidity detection layer provided so as to cover the first optical fiber
Data Source
AI summary
A monitoring humidity measurement system includes: a humidity measurement optical fiber including a first optical fiber and a humidity detection layer provided so as to annularly cover the first optical fiber; a reference optical fiber including a second optical fiber; a plurality of optical communication cables; and a signal processing device configured to, with a laser beam entering into the first and second optical fibers, calculate and obtain Brillouin frequency shift and Rayleigh frequency shift of backscatter light from the first and second optical fibers based on the entering laser beam, and store predetermined constants, wherein reference data and target data are measured from the Rayleigh frequency shift and an initial humidity value calculated from the Brillouin frequency shift, and the value of humidity at the present time is calculated on the basis of Rayleigh frequency shift per unit humidity calculated from a difference between the above two data.