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The Fantastic Journey of Raman Scattering: How Light Reveals Hidden Heat?
With the advancement of technology, distributed temperature sensing systems (DTS) are becoming an increasingly important tool in industrial applications. These systems use optical fiber as a linear sensor to measure temperature and are able to provide measurement distances up to 30 km with accuracy up to ±1°C, making them critical across a wide range of industries.
Distributed temperature sensing systems can obtain continuous temperature profiles through optical fiber measurement, not just point-to-point measurements.
Measurement principle: Raman effect
The core of the DTS system lies in the Raman scattering phenomenon. When the fiber is subjected to thermal changes, this causes local changes in the refractive index within the fiber. These changes in turn induce inelastic scattering of light, known as Raman scattering. Thermal energy in optical fibers exists in the form of molecular or lattice vibrations, and these high-frequency (10 THz) molecular vibrations play a decisive role in Raman scattering.
The light scattered by Raman produces a spectral shift compared to the incident light, and this shift is an indicator of temperature.
Technical Principles: OTDR and OFDR Technology
In distributed sensing technology, OTDR (Optical Time Domain Reflectometry) and OFDR (Optical Frequency Domain Reflectometry) are two basic measurement principles. The use of OTDR technology makes it possible to locate temperature events by analyzing the scattered light, while OFDR technology uses more complex frequency measurements to perform precise temperature profiling.
The core of these technologies is to use the scattered light to transmit back and then infer the temperature change.
System Integration and Fiber Optic Design
The DTS system design includes components such as laser source, pulse generator and receiving unit, and uses standard telecommunication optical fiber as sensor. This design not only reduces costs but also improves installation flexibility. Since the optical fiber itself has no moving parts, its service life can also exceed 30 years, further reducing maintenance and operating costs.
Safety and Operational Considerations
When using optical DTS systems, laser safety requirements must be considered. Many systems use low-power lasers and are highly safe, while some high-power systems require operation by a certified safety officer. Such design considerations enable DTS to be safely used in hazardous areas.
Application Areas
Distributed temperature sensing has a wide range of applications, including oil and gas exploration, industrial fire monitoring, and environmental monitoring. Whether it is underground monitoring in oil fields or fire detection in tunnels, the DTS system provides unparalleled advantages.
Recently, DTS systems have also been applied to environmental monitoring, such as water flow temperature and groundwater source detection.
In summary, distributed temperature sensing technology is realizing value in all walks of life with its high efficiency and accuracy. But as our understanding of environmental change deepens, how will this technology develop and affect our lives in the future?
