Features and advantages of fiber optic sensors:
Optical fiber sensors have the advantages of extremely high sensitivity and accuracy, good inherent security, anti-electromagnetic interference, high insulation strength, corrosion resistance, integration of sensing and transmission, and compatibility with digital communication systems. It can be summarized as follows:
(1) High sensitivity;
(2) Light, flexible and easy to install and bury;
(3) Electrical insulation and chemical stability. Optical fiber itself is a kind of highly insulating and chemically stable substance, which is suitable for harsh environments such as high-voltage isolation and flammable and explosive in power systems and chemical systems;
(4) Good security. The optical fiber sensor is a passive component of electricity, so when it is used in the measurement, there is no hidden danger of leakage and electric shock;
(5) Anti-electromagnetic interference. In general, the frequency of light waves is higher than the frequency of electromagnetic radiation, so light propagates in optical fibers without being affected by electromagnetic noise;
(6) Distributed measurement. One optical fiber can realize long-distance continuous measurement and control, and can accurately measure the strain, damage, vibration, and temperature information at any point, and thus form a monitoring area with a wide range and improve the detection level of the environment;
(7) Long service life. The main material of the optical fiber is quartz glass, which is covered with a polymer material cladding, which makes it have greater durability than metal sensors;
(8) Large transmission capacity. The optical fiber is used as a bus, and the bulky multi-core underwater cable is replaced with a large-capacity optical fiber to collect and store the information of each sensing point, and the distributed optical fiber sensor monitoring is realized through multiplexing technology.
Distributed fiber optic sensor
Distributed optical fiber sensing technology was proposed in the late 1970s. It developed with the emergence of optical time domain reflection (OTDR) technology, which is still widely used in fiber optic engineering. In these ten years, a series of distributed optical fiber sensing mechanisms and measurement systems have been produced, which have been gradually applied in many fields. At present, this technology has become one of the most promising technologies in fiber optic sensing technology.
Distributed optical fiber sensor is a sensor that uses unique distributed optical fiber detection technology to measure or monitor the spatial distribution and time-varying information along the optical fiber transmission path. Utilizing the transmission characteristics of light waves in optical fibers, continuous sensing can be measured along the length of the optical fiber (such as temperature, pressure, stress, and strain). Optical fibers are both sensing media and measured transmission media. It arranges the sensing fiber along the field, and can obtain the spatial distribution of the measured field and the change information over time at the same time.
Distributed optical fiber sensors have the following characteristics:
1) The sensing elements in a distributed optical fiber sensing system are only optical fibers;
2) One measurement can obtain the measured one-dimensional distribution map in the entire optical fiber area, and by setting the optical fiber into a grating, the measured two-dimensional and three-dimensional distribution can be determined;
3) The spatial resolution of the system is generally on the order of meters, so only the average value can be observed for changes measured in a narrower range;
4) The measurement accuracy and spatial resolution of the system generally have a mutual constraint relationship;
5) The detection signal is generally weak, so the signal processing system is required to have a higher signal-to-noise ratio;
6) Since a large number of signal addition averaging, frequency scanning, phase tracking and other processing are required during the detection process, it takes a long time to achieve a complete measurement.
Because fiber-optic cables are not susceptible to electromagnetic interference, distributed fiber-optic temperature sensing systems are usually used for temperature monitoring and measurement of hot spots in power cables. The grasp and management of harsh environments and the need to improve the field environment are the main reasons for the steady growth of the distributed optical fiber temperature sensing system market. At the same time, the technical difficulties of sensor cable deployment are also the main obstacles facing the development of this market. With more and more applications, distributed fiber optic sensors are now mainly used in 6 areas, including structural inspection of pipelines and offshore oil platforms; leak detection of liquid pipelines and dams; road icing detection, railway monitoring; System detection, power cable monitoring; fiber optic communication production monitoring; environmental monitoring and long-term temperature measurement.
Finally, I will introduce three kinds of optical fiber sensors with various functions imported from Industrial Mining Network from foreign countries. The first is the optical fiber temperature sensor-FOT-L-SD. Such extreme environments include low temperature, nuclear environment, microwave, and high-intensity RF. FOT-L combines all the excellent features you expect from an ideal sensor body. Therefore, this type of sensor can still provide high-precision and reliable temperature measurement even under extreme temperature and adverse environment.
Then there is the optical fiber pressure sensor-FOP-M, FOP-M is specially designed for the high temperature field of aerospace and defense. FOP-M can withstand high temperatures of 150 ° C (302 ° F). Unlike most traditional pressure sensor designs, FOP-M uses a unique silicon crystal diaphragm deflection design. FOP-M is the best choice for harsh environmental pressure measurement. The sensor is completely immune to electromagnetic and radio frequency interference, and its inherent reliability is suitable for hazardous and high temperature environments.
Finally, the optical fiber refractive index sensor-FRI, is a unique sensor design based on the length change of the liquid Fabry-Perot optical cavity to accurately determine the refractive index of the fluid. The length of the flushing Fabry-Perot optical cavity is directly proportional to the refractive index of the fluid sample. Therefore, the refractive index can be measured by measuring the length of the Fabry-Perot cavity using white light interference technology. Even in harsh temperature, EMI, humidity environments and variable calibration conditions, fiber optic signal conditioners still have the ability to measure refractive index. The FRI optical fiber refractive index sensor provides better and more reliable refractive index measurement for existing applications in the industry. At the same time, the sensor also has the new expansion capability of continuous online monitoring of the refractive index of fluids under harsh conditions.