Optical fiber temperature sensors use the principle that the absorption spectrum of some substances changes with temperature, and a polymer temperature-sensitive material matched with the refractive index of the optical fiber is coated on the outside of the two fusion-spliced fibers to make light energy. The input of the root fiber to the reflecting surface leads to another fiber output. Since the new temperature-sensitive material is affected by the temperature and the refractive index changes, the output optical power is a function of temperature.
There are many types of optical fiber temperature sensors. In addition to the fluorescence and distributed optical fiber temperature sensors described above, there are optical fiber grating temperature sensors, interferometric fiber temperature sensors, and optical fiber temperature sensors based on bending losses, etc., due to their many types and applications. The development is also very extensive, for example, applied to the power system, construction industry, aerospace industry, and marine development fields.
The Internet of Things technology has been widely used at this stage. It uses various technologies to sense, transmit, process, and feed back information. Its greatest feature is the diversity, dispersivity, intelligence, and real-time nature of perception. The diversity manifests as many perceptual objects, many perceptual parameters, and large capacity; dispersiveness means that people and things, things and things are usually dispersed; intelligence means that the data needs to be analyzed and processed; practicality can be perceived, transmitted and Processing information.
The current Internet of Things is different from the early Internet of Things. The early Internet of Things identified the static characteristics of items through RFID technology. Now, the Internet of Things acquires various kinds of information through various kinds of information sensing devices, such as RFID, photoelectric sensors, global positioning systems, etc., and carries out information transmission and processing based on the Internet. The communication and interaction of things, things and things. The Internet of Things involves multiple disciplines, multiple technologies, and requires advanced communication technologies as support.
Optical fiber communications and fiber-optic sensing technologies will play an important role in the Internet of Things. The optical fiber has wideband characteristics and can be used to detect and transmit a variety of sensors to a single optical fiber. Optical fiber sensor has the advantages of small size, light weight, strong and durable, anti-electromagnetic interference, sensor head without power supply, safety (good insulation, no explosion risk), remote telemetry, multi-point reuse, distributed measurement, etc. Optical fiber materials have unique advantages as sensors.
The principle of fiber-optic sensing is to sense the changes in the physical quantity of the outside world by detecting the intensity, phase, frequency/wavelength, and polarization changes of the optical wave transmitted in the optical fiber. Optical fiber sensors can be made into discrete, quasi-continuous and distributed sensory measurement systems. Can measure temperature, displacement, acceleration, pressure, strain, electric field, magnetic field, rotation, gas concentration, flow rate, corrosion and other variables.
As early as 2008, IBM put forward the concept of "smart earth" and proposed that the government invest in building a new generation of smart infrastructure. The next phase of IT industry's task is to apply a new generation of information technology to various industries, embed and equip sensors in various objects such as power grids, transportation, bridges, tunnels, buildings, dams, water and gas pipelines, and urban infrastructure. , and through the Internet connection, the formation of "Internet of Things."
Optical fiber sensors have a wide range of applications, mainly in the following areas:
The application of interference gyroscopes and grating pressure sensors in bridges, dams, and oil fields in urban construction. Fiber-optic sensors can be embedded in concrete, carbon fiber-reinforced plastics, and composites to measure stress relaxation, construction stress, and dynamic load stress, thereby assessing the structural performance of bridges during short-term construction and long-term operating conditions.
In the power system, it is necessary to measure parameters such as temperature and current, such as the temperature of the stator and rotor in high-voltage transformers and large motors. Since electrical sensors are susceptible to electromagnetic field interference, they cannot be used in such applications and can only be used. Fiber Optic Sensor. For example, a distributed optical fiber temperature sensor is a new technology developed in recent years for real-time measurement of spatial temperature field distribution.
Temperature measurement of production process and equipment for flammable and explosive materials. The optical fiber sensor is essentially a fireproof and explosion-proof device. It does not require explosion-proof measures and is very safe and reliable. Compared with electrical sensors, both cost and sensitivity can be improved.
In addition, it can also be applied to railway monitoring, rocket propulsion systems, and well testing.
In short, the Internet of Things and fiber-optic sensors are complementary and mutually reinforcing. Optical fiber has the advantages of wideband, high capacity, long-distance transmission and multi-parameter, distributed, low-power sensing. Optical fiber sensing can constantly capture new technologies for optical fiber communications (such as new semiconductor light sources, new optical fibers) and new devices. Various optical fiber sensors are expected to be widely used in the Internet of Things. Optical fiber technology has a broad application prospect in the Internet of Things. All-optical IoT is expected to emerge in the future and become a new form of Internet of Things.
Optical fiber temperature sensors use the principle that the absorption spectrum of some substances changes with temperature, and a polymer temperature-sensitive material matched with the refractive index of the optical fiber is coated on the outside of the two fusion-spliced fibers to make light energy. The input of the root fiber to the reflecting surface leads to another fiber output. Since the new temperature-sensitive material is affected by the temperature and the refractive index changes, the output optical power is a function of temperature. 
