The optical fiber temperature sensor is based on the principle that the absorption spectrum of some substances changes with temperature. A polymer temperature-sensitive material that matches the refractive index of the optical fiber is coated on the two fused optical fibers to make the light energy The root fiber is input to the reflecting surface and another fiber is output. Because this new temperature-sensitive material is affected by temperature, the refractive index changes, so the output optical power is a function of temperature.
There are many types of fiber optic temperature sensors. In addition to the fluorescence and distributed fiber temperature sensors introduced above, there are fiber grating temperature sensors, interferometric fiber temperature sensors, and fiber optic temperature sensors based on bending loss. Because of their many types, applications The development is also very extensive, for example, applied to the power system, construction, aerospace and marine development fields.
The Internet of Things technology has been widely used at this stage. It uses various technologies to perceive, transmit, process and feedback information. Its biggest feature is the diversity, decentralization, intelligence and real-time nature of perception. Diversity is manifested by many perception objects, many perception parameters, and large capacity; decentralization means that people and things, things and things are usually more scattered; intelligence means that data needs to be analyzed and processed; practicality means real-time perception, transmission and Processing information.
The current Internet of Things is different from the earlier Internet of Things. The early Internet of Things recognized the static characteristics of items through RFID technology. The current Internet of Things obtains various information through various information-aware devices, such as RFID, photoelectric sensors, and global positioning systems, and transmits and processes information based on the Internet to achieve human and The communication and interaction of things, things and things. The Internet of Things involves multiple disciplines and technologies, and needs advanced communication technologies as support.
Optical fiber communication and optical fiber sensing technology will play an important role in the field of Internet of Things. The optical fiber has broadband characteristics, and various sensors can be reused in one optical fiber for detection and transmission. Optical fiber sensor has the advantages of small size, light weight, strong durability, anti-electromagnetic interference, no power supply for the sensor head, safe use (good insulation, no risk of fire and explosion), remote telemetry, multi-point multiplexing, distributed measurement, etc. As a sensor, fiber optic materials have unique advantages.
The principle of optical fiber sensing is to detect changes in external physical quantities by detecting changes in the intensity, phase, frequency / wavelength, and polarization of light waves transmitted in the optical fiber. Fiber optic sensors can be made into discrete, quasi-continuous and distributed sensor measurement systems. Various variables such as temperature, displacement, acceleration, pressure, strain, electric field, magnetic field, rotation, gas concentration, flow rate, corrosion, etc. can be measured.
As early as 2008, IBM proposed the concept of "smart earth" and suggested that the government invest in the construction of a new generation of smart infrastructure. The next stage of the IT industry's mission is to apply a new generation of information technology to various industries, embed and equip sensors into various objects such as power grids, transportation, bridges, tunnels, buildings, dams, water and oil pipelines, urban infrastructure, etc. , And connected through the network to form the "Internet of Things".
The application range of fiber optic sensors is very wide, mainly in the following aspects:
The application of interferometric gyroscopes and grating pressure sensors in bridges, dams, oil fields, etc. in urban construction. Fiber optic sensors can be pre-buried in concrete, carbon fiber reinforced plastics, and various composite materials to test stress relaxation, construction stress, and dynamic load stress to evaluate the structural performance of the bridge during the short-term construction phase and long-term operation.
In the power system, parameters such as temperature and current need to be measured, such as the detection of the temperature in the stator and rotor of high-voltage transformers and large motors. Because electrical sensors are susceptible to interference from electromagnetic fields, they cannot be used in such occasions and can only be used Fiber Optic Sensor. For example, the distributed optical fiber temperature sensor is a high-tech that has been developed in recent years to measure the spatial temperature distribution in real time.
Used for temperature measurement of the production process and equipment of flammable and explosive materials. The optical fiber sensor is essentially a fire and explosion-proof device. It does not require explosion-proof measures and is very safe and reliable. Compared with electrical sensors, it can both reduce costs and increase sensitivity.
In addition, it can also be used in railway monitoring, rocket propulsion systems, and oil well detection.
In short, the Internet of Things and optical fiber sensing have a complementary and mutually reinforcing role. Optical fiber also has the significant advantages of broadband, large capacity, long-distance transmission, and the realization of multi-parameter, distributed, and low energy consumption sensing. Optical fiber sensing can continuously absorb new technologies of optical fiber communication (such as new semiconductor light sources, new optical fibers), new devices, and various optical fiber sensors are expected to be widely used in the Internet of Things. Optical fiber technology has a very broad application prospect in the Internet of Things. The all-optical Internet of Things is expected to appear in the future and become a new form of Internet of Things.
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