Fiber Optic Sensor
With the development of modern science and technology, the acquisition of information becomes more and more important. Sensors are just an important technical means for sensing, detecting, monitoring and transforming information. Fiber optic sensor is a new type of sensor following optics and electronics.
The optical fiber sensor is a sensor that uses the light transmission characteristics of the optical fiber to convert the measured light characteristics (intensity, phase, polarization, frequency, wavelength). It sends the light from the light source to the modulator through an optical fiber, and after the parameter to be measured interacts with the light entering the modulation area, the optical properties of the light (such as light intensity, wavelength, frequency, phase, deviation, etc.) are caused. The change, called modulated signal light, is sent to the photodetector through the optical fiber, and after demodulation, the measured parameter is obtained.
Different from the previous sensors, the optical fiber sensor takes the state of the measured signal in the form of light signal. The optical signal can not only be directly sensed by people, but also can be used for photoelectric and electro-optical conversion by using small and simple components such as semiconductor diodes such as photodiodes, which can be easily matched with some electronic assemblies. In addition, optical fiber is not only a sensitive component, but also a An excellent low-loss transmission line. Therefore, fiber optic sensors can also be used for long-distance measurement that traditional sensors are not suitable for.
Fiber optic sensing includes two functions: perception and transmission of external signals (measured). The so-called perception means that the physical characteristic parameters of the light wave transmitted in the optical fiber, such as the intensity (power), wavelength, frequency, phase, and polarization state, change according to the external signal according to its change law. Measuring the change of the optical parameter means that the external signal is sensed. Variety. This perception is essentially the modulation of light waves propagating in the optical fiber by external signals. The so-called transmission means that the optical fiber transmits the light wave modulated by the external signal to the photodetector for detection, extracts the external signal from the light wave and performs data processing as required, that is, demodulation.
Therefore, optical fiber sensing technology includes two aspects of modulation and demodulation technology, that is, how the external signal (measured) modulates the modulation technology (or loading technology) of the light wave parameter in the optical fiber and how to extract the external signal from the modulated light wave (Measured) demodulation technology (or detection technology).
