Optical Fiber Temperature Measurement Dispersion Compensation
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Solution Overview
Problem
Existing multipoint temperature measuring systems using optical fibers face challenges in distinguishing temperature data from noise, particularly when using semiconductor lasers, which results in reduced signal-to-noise ratio and difficulty in achieving high accuracy, especially in narrow temperature ranges.
Innovation Solution
A temperature measuring system that inputs optical pulses from a laser light source into an optical fiber, detects back-scattering light, and computes corrected temperature data by varying the degree of smoothing based on a correlation between measured data and a transfer function, allowing for effective noise reduction without losing high-frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If semiconductor laser is used for the laser light source, then the cost is reduced, but the wavelength accuracy and peak value of optical pulses are low and noise is easily generated
Solution Approach 1:
A dispersion compensation module is introduced as an intermediary component between the semiconductor laser and the optical fiber. This module compensates for wavelength dispersion caused by the semiconductor laser's lower wavelength accuracy, thereby maintaining measurement precision while allowing the use of cost-effective semiconductor lasers.
Solution Approach 2:
The system adjusts optical parameters such as pulse width and peak power to optimize the balance between signal quality and noise reduction. By carefully controlling these parameters, the system achieves acceptable measurement accuracy despite the inherent limitations of semiconductor lasers.
2Measurement precision
If optical pulses with high laser power are input to the optical fiber, then the distance resolution and SNR are improved, but SRS (Stimulated Raman Scattering) occurs
Solution Approach 1:
The system dynamically adjusts the optical pulse parameters based on the measurement requirements and fiber characteristics. By optimizing pulse width and peak power in real-time, the system achieves high SNR and distance resolution while maintaining laser power below the SRS threshold through adaptive parameter control.
3Object-affected harmful factors
If a filter is applied to attenuate frequency bands other than temperature data frequency band, then noise is reduced, but temperature data component is also attenuated
Solution Approach 1:
Instead of directly filtering the temperature data signal, the system uses a dispersion compensation module as an intermediary that addresses the root cause of noise (wavelength dispersion) before it degrades the signal. This approach reduces noise without attenuating the temperature data components.
Solution Approach 2:
The system replaces the mechanical/electrical filtering approach with an optical compensation approach. By using the dispersion compensation module to correct wavelength dispersion in the optical domain, the system achieves noise reduction without the signal attenuation problems associated with frequency band filtering.
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 approach enables accurate noise reduction, improves measuring accuracy, and allows the use of less expensive semiconductor lasers, reducing costs while maintaining high-frequency component integrity.
Implementation Method 1
optical pulses having a predetermined wavelength propagate through the optical fiber, and the temperature distribution along a propagating direction of the optical pulses is obtained from a variation with time of back-scattering light (that is, Raman scattering light) caused by the propagating optical pulses
Implementation Method 2
A laser light source is an example of a light source that emits the optical pulses
Data Source
AI summary
A temperature measuring system includes a laser light source to emit optical pulses, an optical fiber, arranged to pass through a plurality of measuring points, and input with the optical pulses, and a measuring device to detect back-scattering light output from the optical fiber and measure a temperature at the plurality of measuring points, to acquire measured temperature data. The measuring device computes corrected temperature data by varying a degree of smoothing the measured temperature data in a distance direction of the optical fiber, according to a correlation between the measured temperature data and a transfer function peculiar to the temperature measuring system.