| The hydraulic pressure sensor is a device used to measure the depth of seawater,which is usually used in ocean engineering,marine scientific research,marine resource exploration and other fields.As the depth of the ocean increases,the hydraulic pressure will also increase.In order to meet the safety of working equipment in the deep sea environment,accurate measurement of seawater pressure is also crucial to ensure the safety of equipment in deep-sea environments.Additionally,in areas such as underwater oil and gas extraction and marine seismic monitoring,the hydraulic pressure sensor plays an indispensable role in monitoring changes in underwater pressure.It provides essential data support for work in the marine domain and is a significant pillar in the national development plan for the marine economy during the "14th Five-Year Plan" period.As a new type of sensing device,the optical fiber sensors have the characteristics of high sensitivity,high reliability,and strong anti-interference capability.In this paper,we design and propose a hydraulic pressure sensor integrated in a dual-core hollow optical fiber and a capillary single core fiber based on SPR for hydraulic pressure sensingThe main research content and innovation points of my dissertation include:1.An integrated Mach-Zehnder interferometer(MZI)for hydraulic pressure sensing is designed and proposed.Using D-type hollow double core(DHOF),a type of special optical fiber,the traditional discrete Mach-Zehnder interferometer is integrated in a single fiber to reduce the size and power consumption of the sensor.In order to obtain better sensing sensitivity,sensing range and stability,two commercial optical simulation software,are used to simulate the fiber model and obtain its transmission spectrum,effective refractive index and sensitivity of the proposed sensor at the broad-spectrum light incidence.Combined with the analysis of the simulation results,a better sensing performance is obtained by adjusting the geometric structure of the sensor.The simulation results show that the effective refractive index of the fiber core can be influenced by adjusting the residual thickness of the cladding between the fiber core and the D-shaped platform,as well as the relative distance between the two fiber cores.This adjustment leads to variations in the effective refractive index changes between the two fiber cores.Additionally,we have observed that the sensitivity of the MZI(Mach-Zehnder Interferometer)can be affected by adjusting the length of the MZI’s sensing arm.However,the relationship between the length of the sensing arm and the sensitivity is not simply linear.It requires careful and repeated adjustments and trials to determine the optimal length of the sensing arm.2.Based on the above DHOF,a dual platform hollow dual core fiber(DDHOF)is proposed for hydraulic pressure measurement.Based on the DHOF,the fiber core away from the D-sharp platform was moved to the right side of the central air hole and another D-platform was designed next to it.It has the advantage of further increasing the asymmetry of the fiber structure and reducing the distance between the cores and the external environment,which makes the pressure effect more obvious.The calculation results show that the pressure sensing sensitivity of DDHOF is significantly improved compared with that of DHOF.3.A hydraulic pressure sensor based on surface plasmon resonance(SPR)is designed and proposed,and the SPR effect is innovatively applied to the field of hydraulic pressure sensing.In this paper,a D-type hollow optical fiber with a nano-gold film deposited inside the central air hole is used to excite the SPR effect.The proposed hydraulic pressure sensor based on the SPR effect can demodulate the pressure value acting on the sensor by detecting the shift of the peak in the confinement loss spectrum.The effect of the bilayer structure incorporating a polycarbonate film on the sensing sensitivity is also compared,and the calculation results show that the sensing sensitivity of the SPR seawater pressure sensor based on the bilayer structure is 3.4 times higher than the previous one. |
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