摘要:
A fiber grating pressure sensor includes an optical sensing element which includes an optical fiber having a Bragg grating impressed therein which is encased within and fused to at least a portion of a glass capillary tube and/or a large diameter waveguide grating having a core and a wide cladding. Light is incident on the grating and light is reflected from the grating at a reflection wavelength null1. The sensing element may be used by itself as a sensor or located within a housing. When external pressure P increases, the grating is compressed and the reflection wavelength null1 changes. The shape of the sensing element may have other geometries, e.g., a nulldogbonenull shape, so as to enhance the sensitivity of shift in null1 due to applied external pressure and may be fused to an outer shell.
摘要:
An optical sensing device including a force-applying assembly for providing a force and a Fabry-Perot (FP) element including a large-diameter waveguide having a core and having a cavity in line with the core, the cavity having reflective surfaces and having an optical path length related to the distance between the reflective surfaces, the FP element being coupled to the force so that the optical path length changes according to the force, the FP element for providing an output optical signal containing information about a parameter that relates to the force. Sometimes the large-diameter waveguide is formed by collapsing a glass tube, having a bore and having an outer diameter of about one millimeter, onto a pair of optical fibers arranged in tandem in the bore and separated by a predetermined distance, and respective end faces of the optical fibers form the cavity and are coated with a wholly or partially reflective material.
摘要:
A fiber grating pressure sensor includes an optical sensing element 20,600 which includes an optical fiber 10 having a Bragg grating 12 impressed therein which is encased within and fused to at least a portion of a glass capillary tube 20 and/or a large diameter waveguide grating 600 having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light 14 is incident on the grating 12 and light 16 is reflected from the grating 12 at a reflection wavelength null1. The sensing element 20,600 may be used by itself as a sensor or located within a housing 48,60,90,270,300. When external pressure P increases, the grating 12 is compressed and the reflection wavelength null1 changes. The shape of the sensing element 20,600 may have other geometries, e.g., a nulldogbonenull shape, so as to enhance the sensitivity of shift in null1 due to applied external pressure and may be fused to an outer shell 50. At least a portion of the sensing element may be doped between a pair of gratings 150,152, to form a compression-tuned laser or the grating 12 or gratings 150,152 may be constructed as a tunable DFB laser. Also, the axial ends of element 20,600 where the fiber 10 exits the tube 20 may have an inner tapered region 22 and/or a protruding tapered (or fluted) axial section 27 to provide strain relief or improved pull strength for the fiber 10. A temperature grating 270 may be used to measure temperature and allow for a temperature-corrected pressure measurement. The sensor may be suspended within an outer housing 112, by a fluid, spacers, or other means. The invention may also be used as a force transducer.