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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.

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The mol­ecule of the title compound, C10H13NO3, is approximately planar (maximum deviation 0.1424 Å). In the crystal, mol­ecules are linked into inversion dimers by pairs of N—H⋯O hydrogen bonds, and the dimeric units are linked by non-classical C—H⋯O hydrogen bonds, forming a layered structure.