The working principle and application of distributed temperature sensing fiber and temperature sensing grating

Fiber optic temperature sensor, Intelligent monitoring system, Distributed fiber optic manufacturer in China

Distributed fiber optic temperature measurement technology

Distributed optical fibers are based on Raman scattering and optical time domain reflection measurement techniques to obtain spatial temperature distribution information. By laying a temperature sensing optical fiber on the surface of the tested object, such as a pipeline, collecting and analyzing the time and intensity information of Raman backscattered light generated by the propagation of light pulses within the temperature sensing optical fiber, corresponding position and temperature information can be obtained. After obtaining the temperature and position information of each point, a temperature curve about different positions of the entire optical fiber can be obtained. The conventional distance measurement can reach up to 30 kilometers, and the spatial positioning can reach the order of meters, enabling uninterrupted automatic temperature measurement. It is particularly suitable for applications that require long-distance, large-scale, and multi-point measurement. At present, FJINNO distributed fiber optic temperature measurement technology has many application cases in temperature detection, fire alarm systems, and power cable temperature monitoring in production workshops of tunnels, oil depots, dangerous goods depots, military and mining enterprises.

Application of Temperature Sensing Fiber in Distributed Fiber Optic Temperature Measurement System in Rail Transit

With the rapid development of rail transit, it not only facilitates public travel, reduces traffic congestion, but also reduces environmental pollution caused by car exhaust. Currently, it has become the mode of transportation for the vast majority of citizens. However, the rapidly developing rail transit industry has brought about huge problems of passenger flow accumulation and dispersion. Without a complete fire evacuation system, fires can occur during operation, which can easily cause major casualties and huge economic losses. The fiber optic temperature measurement system can detect the temperature of fires inside the station, which is particularly important for the evacuation of personnel in case of interval fires and fire alarms. Nowadays, most of these situations are detected using temperature sensing optical fibers. The traditional installation and laying of temperature sensing optical fibers in tunnels can cover them naturally parallel to the steel wires, and a stainless steel wire buckle is used to fix the detection optical fibers and steel wires per meter. Special tunnel sections can be appropriately increased; The detection fiber can be fixed directly below the steel wire.

The composition of a distributed temperature sensing fiber optic measurement device

The distributed fiber optic temperature measurement device can be composed of fiber optic slots, bidirectional couplers, splitters, lasers, avalanche photodiodes, amplification circuits, lasers, synchronous controllers, data acquisition cards, etc.

The working principle of temperature sensing optical fibers

Install organic internal optical fibers and high-precision temperature sensing chips in the fiber optic groove. When in use, the external optical fibers are connected to the internal optical fibers through the fiber optic groove. When a light pulse is emitted from one end of the fiber into the fiber, it propagates forward along the fiber. As the inner wall of the fiber resembles a mirror, the light pulse reflects at every point during propagation, with a small portion of the reflected light pointing in the opposite direction of the incident light (also known as backward). There is a certain correlation between the intensity of this backward reflected light and the temperature of the reflection point in the light. The higher the temperature of the reflection point (the ambient temperature of the fiber optic at that point), the greater the intensity of the reflected light. That is to say, the intensity of backward reflected light can reflect the temperature of the reflection point. By utilizing this phenomenon, if the intensity of the backward reflected light can be measured, the temperature of the reflection point can be calculated.

Working principle of temperature sensing grating

Temperature sensing gratings have emerged in recent years due to the widespread use of fiber optic temperature sensors, using fibers as transmission channels and gratings as temperature sensing devices. The principle is that temperature changes affect the grating period or refractive index of the fiber core, resulting in wavelength shift of the grating Bragg signal. By detecting the change in Bragg wavelength, the temperature change around the fiber Bragg grating is obtained. The composition of temperature sensing gratings mainly consists of fiber optic grating probes, transmission fibers, connecting fibers, fiber optic connectors, signal processing machines, etc.

Fiber Bragg Grating Temperature Sensor

With the popularity of fiber optic grating arrays and weak grating arrays, fiber optic grating sensors are increasingly being applied in distributed temperature measurement scenarios. In many temperature monitoring scenarios, temperature sensors are required to have high accuracy and response speed, while also being able to identify the specific position of the grating. Fiber optic grating temperature sensor is a passive sensing device with significant advantages such as no self heating, anti electromagnetic interference, high sensitivity, lightweight and flexible, multi parameter composite sensing, and large-scale distributed measurement. It has a wide range of application prospects in the field of fiber optic temperature sensing.

FJINNO provides fiber optic temperature measurement and fiber optic grating temperature sensing fire detection systems at reasonable prices. We welcome agents to cooperate and contact us.