Abstract
In this paper, an optical fiber pressure sensor cascading a diaphragm-assisted Fabry-Perot interferometer (FPI) and a fiber Bragg grating (FBG) is proposed and demonstrated. The sensor comprises an optical fiber, a fused-silica ferrule, and a fused-silica diaphragm. We use a femtosecond laser firstly to fabricate a pit on the end face of the ferrule and then investigate the laser heat conduction welding and deep penetration welding technology for manufacturing the seepage pressure sensor of the all-fused-silica material. We develop a sensor based on a monolithic structured FPI without adhesive bonding by means of all-laser-welding. The pressure characteristics of the sensor have good linearity at different temperatures. Also, the monolithic structured sensor possesses excellent resolution, hysteresis, and long-term stability. The environmental temperature obtained by the FBG is employed to compensate for the difference in seepage pressure at different temperatures, and the difference in seepage pressure responses at different temperatures is shown to be very small after temperature compensation.
Highlights
The failure of a levee can cause flood damage, posing a serious threat to human residential areas and infrastructures
Even if the diaphragm-assisted Fabry-Perot interferometer (FPI) optical fiber sensor configurations are made up of a kind of material, the current common bonding adhesive of epoxy [21] will influence the performance of sensor, and the adhesive of epoxy will decompose at high temperatures
Fabrication of all-laser-welding of FPI leads to the formation of a monolithic structure of all-fused-silica materials as the seepage pressure sensor
Summary
The failure of a levee can cause flood damage, posing a serious threat to human residential areas and infrastructures. Even if the diaphragm-assisted FPI optical fiber sensor configurations are made up of a kind of material, the current common bonding adhesive of epoxy [21] will influence the performance of sensor, and the adhesive of epoxy will decompose at high temperatures This will cause a large temperature dependence due to the adhesive of epoxy having a different CTE from the materials of the sensor. Fabrication of all-laser-welding of FPI leads to the formation of a monolithic structure of all-fused-silica materials as the seepage pressure sensor. The FPI possesses an open FP cavity due to the CO2 laser deep penetration point welding between the single mode optical fiber (SMF) and the fused-silica ferrule, which eliminates the undesirable pressure on the inside surface of the diaphragm and improves the temperature stability of the sensors.
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