Optical Fiber Temperature Measurement with Loss Ratio Correction
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Solution Overview
Problem
Accurate double-ended measurement of temperature distribution along an optical fiber is challenging due to variations in the total Raman loss ratio (Ltotal), which can be affected by phenomena like 'darkening', making it difficult to maintain precise temperature measurements.
Innovation Solution
An optical fiber temperature distribution measurement apparatus that performs double-ended measurement by calculating the total length loss ratio using intensity ratios from both ends of the optical fiber, with a constant-temperature unit maintaining temperature stability near the ends and a reference thermometer for correction, allowing for accurate temperature distribution calculation regardless of Ltotal variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If double-ended measurement is performed to improve temperature distribution measurement accuracy, then measurement precision is improved, but the measurement becomes sensitive to variations in total Raman loss ratio which worsens measurement reliability
Solution Approach 1:
The patent implements feedback by measuring the total Raman loss ratio (Ltotal) using the constant-temperature sections and reference thermometers, then using this measured Ltotal value to correct the temperature calculations throughout the optical fiber. This feedback mechanism allows the system to adapt to Ltotal variations and maintain measurement accuracy.
Solution Approach 2:
The patent introduces constant-temperature sections as intermediary reference points within the optical fiber system. These sections serve as mediators that allow measurement of Ltotal without being affected by external temperature variations, thus providing a stable reference for correcting temperature measurements along the rest of the fiber.
2Measurement precision
If constant-temperature sections are added to measure total loss ratio, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The constant-temperature sections serve multiple functions: they provide stable reference temperatures for measuring Ltotal, act as calibration points for the temperature distribution measurement, and enable correction of attenuation effects. This multi-functionality justifies the added structural complexity.
3Reliability
If reference thermometers are placed in constant-temperature sections, then reliability of Ltotal measurement is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses reference thermometers in constant-temperature sections to create a copy or representation of the temperature condition, which then serves as a reference for correcting measurements throughout the system. This copying approach allows reliable Ltotal measurement without requiring direct measurement at every point.
Data Source
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AI summary
The present apparatus includes: an intensity ratio calculation unit configured to calculate a first and a second intensity ratios which are ratios of Stokes light intensity to anti-Stokes light intensity obtained when a light pulse is output to a first end and a second end of an optical fiber, respectively; a temperature calculation unit configured to calculate a temperature distribution along the optical fiber based on a reference temperature, the first and the second intensity ratios, and a total length loss ratio, which is a loss ratio of Stokes light to anti-Stokes light with regard to a total length of the optical fiber; and a total length loss ratio calculation unit configured to calculate the total length loss ratio based on the first and the second intensity ratios with regard to a location in a predetermined section close to both ends of the optical fiber whose temperature is kept constant.