Comparison between optical fiber sensor and traditional sensor

At present, in the Chinese market, fiber Bragg grating (equipped with ASE broadband light source) and distributed sensor based on optical time-domain reflection are the most widely used optical fiber sensing technologies. This technology can basically meet the needs of the medium and low end general market and is well known by industry insiders. The single-frequency fiber laser with spectral linewidth as narrow as 2 kHz and the latest generation of optical sensing technology introduced now are completely different from the optical fiber sensing we now know. This new technical solution can fully meet the higher demand for ultra-long distance, ultra-high precision and ultra-high sensitivity in the high-end market, which cannot be completed by electric sensing and general optical fiber sensing. However, this technology is still in the stage of project approval and pre-research in China. Compared with traditional sensing technology, fiber-based sensors have the following major advantages: 1. Light weight, compact structure, easy to reuse in multiple ways; 2. Resistance to harsh environment, electromagnetic interference and chemical corrosion; 3. There is no need for electricity at the sensing point, and long-distance distributed sensing is possible; 4. Low cost mass production After optical fiber communication, optical fiber sensing has also ushered in an important development opportunity. It has extensive and huge application value in security, military, oil/gas, electricity and scientific research, especially in western developed countries. The optical principle of single-frequency fiber laser for optical sensing is optical frequency time-domain reflection.



Structure principle and classification of optical fiber sensor

1. Structure principle of optical fiber sensor The traditional sensor based on electricity is a device that converts the measured state into measurable electrical signals. Its power supply, sensitive components, signal receiving and processing system and information transmission are all connected with metal wires. Optical fiber sensor is a device that converts the measured state into a measurable optical signal. It is composed of optical transmitter, sensing element (optical fiber or non-optical fiber), optical receiver, signal processing system and optical fiber. The light emitted by the optical transmitter is guided to the sensitive element through the source optical fiber. At this time, a certain property of the light is modulated by the measured, and the modulated light is coupled to the optical receiver through the receiving fiber, so that the optical signal is converted into an electrical signal, and finally the desired measured signal is obtained through signal processing. It can be seen that the optical fiber sensor is essentially different from the traditional sensor based on electricity in measuring principle. Traditional sensors are based on mechanical-electrical measurement, while optical fiber sensors are based on optical measurement. Light is a kind of electromagnetic wave, whose wavelength ranges from 1 mm in the far infrared to 10 nm in the far ultraviolet. Its physical and biochemical effects are mainly caused by the electric field. Therefore, when discussing the sensitive measurement of light, we must consider the vibration of the electric vector E of light, namely A - amplitude vector of electric field E; ω—— Vibration frequency of light wave; φ—— Optical phase; T - propagation time of light. It can be seen that as long as one of the parameters such as the intensity, polarization state (direction of vector A), frequency and phase of the light changes with the change of the measured state, or is modulated by the measured state, then the required measured information can be obtained by adjusting the intensity modulation, polarization modulation, frequency modulation or phase modulation of the light. 2. Classification of optical fiber sensors Note: MM multimode; SM single mode; PM polarization maintenance; a. B, c functional type, non-functional type, pickup type



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