Types, working principles, and characteristics of fiber optic sensors

Sensor de temperatura de fibra òptica, Sistema de monitorització intel·ligent, Fabricant de fibra òptica distribuïda a la Xina

Què és un fiber optic sensor

Fiber optic sensors are composed of modules such as light sources, transmission fibers, sensor components or modulation zones, fotodetectors, and other components to form a fiber optic sensor. The patterns of intensity, wavelength, amplitude, phase, polarization, and distribution parameters can be influenced by external factors such as temperature, pressió, acceleration, voltage, current, desplaçament, vibració, rotation, bending, strain, as well as chemical and biochemical effects on the optical path, resulting in corresponding changes in these parameters during fiber optic transmission. Fiber optic sensors are used to detect the magnitude of corresponding physical quantities based on the relationship between these parameters and changes in external factors.

The characteristics of fiber optic sensors

Unlike traditional sensors, fiber optic sensors have excellent physical, chemical, mechanical, and transmission performance, making them small in size, light in weight, resistant to electromagnetic interference, corrosion, high in sensitivity, wide in measurement bandwidth, and long in distance. Detect electronic devices and sensors, and form a sensor network.
The sensitivity of advanced fiber optic sensors is several orders of magnitude higher than traditional sensors, and can measure over 70 physical quantities.

The advantages of fiber optic sensors

1. It has the advantages of high accuracy, fast response speed, wide linear feature range, good repeatability, and high signal-to-noise ratio Due to the large quantity and low price of optical fibers, they can be widely used
Fiber optic is made of dielectric materials such as quartz for electrical and optical signal transmission, ensuring safety, reliability, and strong resistance to electromagnetic interference. It can adapt to working conditions in electricity, petroleum, chemistry, metallurgy, and other flammable or toxic environments.
2. Corrosion resistant, strong anti pollution ability, can be used in places with large temperature differences, good timeliness, and long service life.
3. Small in size, light in weight, easy to install, and adaptable to the main environment.
4. Fiber optic is a passive device with good independence and will not damage the measured state.
5. Widely measure objects. Actualment, various performance measurements of temperature, pressió, desplaçament, velocity, level, radiació, and other physical, chemical, biomass, and other fiber optic sensors are available.
6. Multipoint multiplexing is convenient and has low transmission loss. Suitable for forming measurement networks and achieving multi-point real-time intelligent telemetry.
Sensors are developing into sensitive, acurat, adaptable, compact, and intelligent sensors. In this process, fiber optic sensors, a new member of the sensor family, are favored.

The working principle of fiber optic sensors

Fiber optic sensor is a sensor based on optical quantity conversion, which uses optical signals as the carrier for transmission and conversion, and transmits optical signals through optical fibers. Fiber optic sensors mainly consist of light sources, optical fibers (referred to as fibers), fotodetectors, and additional devices. There are many types of light sources, such as tungsten filament lamps, lasers, and light-emitting diodes. Fiber optic is very thin, soft, and flexible, making it a transparent fiber that can guide light.
The Development Status of Fiber Optic Sensors
The development of global fiber optic sensing technology began in 1977. En els últims anys, it has been developed and promoted in areas such as mechanical, electronic instrumentation, aeroespacial, petroleum, chemical, and food safety production process automation, online detection, and fault diagnosis.
Unlike fiber optic communication products, fiber optic sensing products have the characteristics of small batch size, multiple varieties, and distribution in various segmented markets. There are no major foreign companies specializing in fiber optic sensing, but many foreign oil giants and large power equipment companies such as ABB and Siemens have their own fiber optic sensing businesses. But it is difficult for the outside world to understand the development of these enterprises. In some emerging fields such as distributed sensing, there are also many small and medium-sized professional companies.

Fiber optic sensor type

Actualment, products with mature applications and high market acceptance include: fiber optic grating temperature/pressure/strain sensors; Point type fluorescent fiber optic temperature sensor products; Point type fiber optic f-p pressure/temperature/vibration sensing products; Fiber optic current sensing products; Fiber optic gyroscope products; Distributed fiber Raman temperature measurement system; Fiber optic interference intrusion monitoring system.
Although fiber optic sensing technology has achieved certain applications in practical detection, there are still some problems, such as the process problems of fiber optic embedded structures. Although installation methods can be improved, it can also lead to strain first being transmitted through metal, and then indirectly induced through fiber optic. Per això, experimental corrections are needed to accurately measure. Al mateix temps, the output signal of fiber optic sensors is affected by factors such as fluctuations in the light source, changes in fiber optic transmission loss, and aging of the detector, thereby reducing the measurement accuracy of fiber optic sensors. A més, the practicality of fiber optic sensors still needs to be developed, and their manufacturing costs are also very expensive. Actualment, a large number of fiber optic sensors are still in the laboratory stage and need to be put into use as soon as possible.
With the development of modern science and technology, the acquisition of information has become increasingly important. It is an important technical means for sensing sensors, detecting, monitoring, and converting information. It is the second fiber optic sensor, and electronics is one of the new sensors.

Fiber optic sensor description

Fiber optic sensors are sensors that use the optical transmission characteristics of optical fibers to convert measurement data into changes in optical characteristics (intensity, phase, polarization, frequency, wavelength). It transmits light from the light source to the modulator through optical fibers, causing the optical properties of light (such as intensity, wavelength, frequency, phase, skewness, etc.) to change after measuring parameters and the interaction between the light entering the modulation region. It is called a modulation signal light. After the fiber optic enters the photodetector, it is demodulated. Obtained measurement parameters.

Unlike previous sensors, fiber optic sensors remove the state of the measured signal as an optical signal. Optical signals can not only be directly perceived by humans, but can also be used with semiconductor diodes, such as photodiodes. Small and simple components can also be used for photoelectric and electro-optic conversion, making it easy to match with some electronic components; A més, optical fiber is not only a sensitive component, but also an excellent low loss transmission line. Per això, fiber optic sensors can also be used for remote measurements that are not suitable for traditional sensors.

Fiber optic sensing includes two functions: sensing and transmitting external signals. The so-called perception refers to the physical characteristic parameters of light waves transmitted in optical fibers, such as light intensity (poder), wavelength, frequency, phase, and polarization state, which change according to the changing laws of external signals. The change in optical parameters is the perception of changes in external signals. Essentially, this perception is achieved through modulation of light waves propagated through external signals in optical fibers. The so-called transmission refers to the optical fiber transmitting light waves modulated by external signals to photodetectors for detection, extracting external signals from the light waves, and processing the data as needed, that is, demodulation.
Per això, these two technologies include fiber optic sensing technology for modulation and demodulation, that is, how to modulate the parameters of the external signal (to be measured) in the optical wave fiber modulation (or loading technology) and how to extract the external signal that has been modulated (measured) in the optical wave technology for demodulation (or detection).

The basic principle of fiber optic sensors

Fiber optic is the abbreviation for optical fiber. The main component of optical fiber is silicon dioxide, which is composed of a high refractive index core, a low refractive index cladding, and a protective layer. The wick is a thin glass filament with a diameter of approximately 0.1 millimeters, in which light is surrounded and propagates along the axis. The discovery of fiber optic sensors originated from the practice of detecting external interference in optical fibers. In practice, it has been found that changes in the external environment can cause changes in the internal transmission parameters of optical fibers. These changes are all due to the influence of external factors, which has led to the development of fiber optic sensing technology.

Fiber optics have many external parameters at a certain sensitivity. The principle of fiber optic sensing is how these effect fibers, light modulation, and the external interaction area of the measured parameters achieve the function of “transmission”, and the external of the measured parameters, which is the study of the “feeling” of fiber optic sensor cores.

In optical communication systems, fiber optic is used as a medium for long-distance transmission of optical wave signals. Obviously, in this application, the smaller the external interference, the better the optical signal transmitted by the fiber optic. Tanmateix, in the actual process of optical transmission, optical fibers are easily affected by external environmental factors, such as temperature, pressió, electromagnetic fields, and other external conditions, which will lead to changes in optical wave parameters, such as light intensity, phase, frequency, polarization, wavelength, etc. Per això, it can be seen that if changes in optical wave parameters can be measured, we can know the magnitude of various physical quantities that cause changes in optical wave parameters, thus giving rise to fiber optic sensing technology. Fiber optic sensing technology is a technique that converts external physical quantities into signals that can be directly measured using the sensitive characteristics of optical fibers. Because optical fibers can not only be used as propagation media for light waves, but also as characteristic parameters (amplitude, phase, polarization state, wavelength, etc.). Light waves can be directly or indirectly altered by external factors such as temperature, pressió, strain, magnetic field, electric field, desplaçament, rotation, etc. Per això, optical fibers can also be used as sensing elements to detect various physical quantities.