In this process, fiber optic sensors, a new member of the sensor family, have gained favor. Fiber optics possess many excellent properties, such as: resistance to electromagnetic interference and atomic radiation; small diameter; flexibility; and lightweight mechanical properties; insulating and non-inductive electrical properties; and water resistance, high-temperature resistance, and corrosion resistance. These properties allow them to function as eyes and ears in places inaccessible to humans (such as high-temperature areas) or harmful environments (such as nuclear radiation zones), and can also transcend human physiological limits to receive external information imperceptible to humans. What are the principles and characteristics of fiber optic vibration sensors?
1. Fiber Optic Sensor Principle
Based on sensing principles, fiber optic sensors can be divided into two categories: light-transmitting (non-functional) sensors and sensing (functional) sensors. In fiber optic sensors, the optical fiber serves only as the light transmission medium, with other sensing elements used to sense the measured signal. The output and input fibers in the sensor are discontinuous; the modulator between them is a spectral change sensing element or other sensing elements. In sensing fiber optic sensors, the optical fiber is sensitive to both the measured signal and the transmission of the optical signal. The "sensing" and "transmitting" fibers in the sensor are continuous. Due to its high-frequency response characteristics, this structure is an ideal solution for computer disk drives, magnetic tapes, ultrasonic equipment, and production lines. In the sensor, the transmitting and receiving fiber bundles are arranged opposite each other. The fiber reaches the receiving fiber through the edge of the target being measured.
Based on different modulation principles, fiber optic sensors can be classified into intensity modulation, phase modulation, polarization modulation, frequency modulation, wavelength modulation, etc. To date, fiber optic sensors can measure more than 70 physical quantities.
2. Characteristics of fiber optic sensors
(1) High sensitivity
Since light is an electromagnetic wave with a very short wavelength, its optical length is obtained through its phase. Take a fiber optic interferometer as an example. Because the diameter of the optical fiber used is very small, even a small change in external mechanical force or temperature will cause a change in optical length, resulting in a large phase change. If a 10m fiber is used, a 1℃ change will result in a minimum detectable phase change of 0.01 ard within 1000 ard. Therefore, the minimum temperature change that can be measured is 10℃, indicating its high sensitivity.
(2) Fast measurement speed
Light has the fastest transmission speed and can transmit two-dimensional information, making it suitable for high-speed measurements, radar, and other signals.
The analysis requires a very high detection rate, which is difficult to achieve using electronic methods. This can be solved by high-speed spectral analysis using optical diffraction.
(3) Suitable for harsh environments
Optical fiber is a medium that is resistant to high pressure, corrosion, and electromagnetic interference, allowing it to be used in harsh environments where other sensors cannot operate. Furthermore, fiber optic sensors are lightweight, small in size, easy to wind, can measure a wide range of objects, are highly reusable, and are low in cost.
What are the principles and characteristics of fiber optic vibration sensors? Fiber optic sensors use light as the carrier of sensitive information and optical fiber as the medium to transmit that information. They possess the characteristics of fiber optic and optical measurement, and have a series of unique advantages: good electrical insulation, strong resistance to electromagnetic interference, high non-invasiveness, high sensitivity, easy remote monitoring of the measured signal, corrosion resistance, explosion-proof, flexible optical path, and easy connection to a computer.
