Abstract: An improved fiberoptic pressure sensing system is disclosed by tapering the tip end of an optical fiber, or alternatively, by tapering or bundling a fiber or group of fibers within a connector. By selectively joining together fibers with a taper while tailoring numerical apertures of the connected fibers, a fiberoptic pressure sensing system is provided with an enhanced ability to increase sensitivity and signal-to-noise performance.

Abstract: An apparatus for determining pressure at one or a number of intermediate points along a catheter inserted into a closed cavity. Fiberoptic cables extend from the proximal end of the catheter to the intermediate points at which pressure measurements are taken as well as to the distal tip of the catheter. The fiberoptic cables transport light signals injected at the proximal end and said light signals are illuminated in the direction of a flexible, reflective membrane. A pressure sensing coupler interconnects proximal and distal sections of the catheter sheath and also houses the pressure sensor. The pressure sensing coupler includes a plurality of radial ports which provide communication between the fluid in the cavity and a pressure sensing chamber, which is also in communication with the reflective membrane. The pressure sensing coupler also enables the passage of inner catheters through axial passageways for interconnection to other distally located pressure sensors.

Abstract: An improved intensity-encoded fiber optic sensor incorporating novel drift correction and filtering means is disclosed. The first embodiments of the invention relate to means for removing unwanted higher-order core and cladding modes from an intensity-encoded signal in an optical fiber using mode strippers and mode filters located strategically at various points in the sensing system. The second set of improvements in the invention relate to an improved technique for long-term temporal drift cancellation in a fiber optic pressure sensor by periodically applying pressure to the sensor tip in order to ascertain the measured voltage at which the sensor diaphragm contacts other elements of the sensor. This measured voltage is subtracted from an initial calibration voltage, and the result is applied to the measured signal as a constant correction term.

Abstract: A fiberoptic based sensor for patient care use. The sensor includes a catheter placed transcutaneously into a blood vessel which is connected to an external measuring head. A sensing tip of the catheter includes a pressure sensing element and an oxygen saturation measuring element. Features of the invention include novel tip designs, measuring head features, and approaches for enhancing measurement though correlation of the saturation and pressure readings.

Abstract: The invention is related to numerous improvements for fiber optic measuring systems, and principally those utilizing a deformable diaphragm for sensing pressure. One aspect of the invention is providing temperature compensation for diaphragm characteristics. Temperature measurement can be achieved by using a light signal having a wavelength distribution which overlaps the cut-off characteristics of a filter positioned at the fiber sensing end. Shifting in the cut-off characteristic in response to temperature modulates the intensity of the reflected back temperature compensation signal. In another approach, temperature is measured through its differential effect on light signals having different launching conditions. With either approach, the temperature measurement is used to calibrate the output of the pressure sensitive diaphragm.

Abstract: An improved intensity-encoded fiber optic sensor incorporating novel drift correction and filtering means is disclosed. The first embodiments of the invention relate to means for removing unwanted higher-order core and cladding modes from an intensity-encoded signal in an optical fiber using mode strippers and mode filters located strategically at various points in the sensing system. The second set of improvements in the invention relate to an improved technique for long-term temporal drift cancellation in a fiber optic pressure sensor by periodically applying pressure to the sensor tip in order to ascertain the measured voltage at which the sensor diaphragm contacts other elements of the sensor. This measured voltage is subtracted from an initial calibration voltage, and the result is applied to the measured signal as a constant correction term.

Abstract: Serveral improvements in fiber optic sensing systems are disclosed. One improvement incorporates a dielectric filter applied directly to the sensing end of an optical fiber detector which has the characteristic that it reflects back a reference light beam of one wavelength while passing a sensing signal of a different wavelength which is modulated in some predetermined fashion beyond the filter. Both light signals are reflected back through the fiber and are, accordingly, attenuated in the identical or nearly identical fashion in response to various noise sources. The ratio of the intensity of the two signals is proportional to the sensed parameter and renders the system essentially self-compensating. The dielectric filter is preferably directly coated onto the exit end of the fiber through vapor deposition techniques.

Abstract: A system and method for initializing and calibrating a fiber optic pressure transducer so that a measured intensity of light which varies as a function of pressure can be accurately translated to the value of pressure which produces that value of light intensity. The transducer includes an enclosed sensor tip having a diaphragm which is exposed to atmospheric pressure on the inside and the pressure to be determined on the outside as measurements are taken, the resulting pressure differential producing a related attenuation in light intensity. Calibration according to the present invention is performed by exposing the diaphragm to atmospheric pressure on the outside and sub-atmospheric pressure on the inside while transmitting light through the fiber in the usual manner. The sub-atmospheric pressure is changed gradually as simultaneous measurements are made of the intensity of light returned through the fiber and the actual value of the sub-atmospheric pressure at a number of discrete times.

Abstract: A miniaturized pressure transducer, particularly suited for intravascular blood pressure measurement, utilizing a single optical fiber for transmitting light both to and from a flexible diaphragm having a light-reflecting surface on one side, the opposite side being exposed to and deflected in accordance with the pressure being measured. The end of the fiber through which light is transmitted to and reflected light received from the diaphragm is ground to form a spherical lens integral with the fiber, whereby light passing through the end of the fiber is focused at a predetermined focal point. The fiber is axially positioned so that the center of the diaphragm, which coincides with the lens axis, is at the focal point when the diaphragm is at maximum deflection, i.e., when its opposite surface is exposed to a predetermined, maximum anticipated pressure.

Abstract: A miniaturized pressure transducer is disclosed wherein light transmitted through a single optical fiber is reflected by a diaphragm exposed to and deflected in accordance with the pressure being measured. The terminal end of the fiber is covered by a light absorption layer having a plurality of discrete openings through which light may pass for reflection by the diaphragm with the proportion of light passing back through the openings and the fiber varying in accordance with the distance between the end of the fiber and the diaphragm, as determined by the pressure exerted thereon. The diaphragm is incorporated in a disposable tip which is threaded to an elongated tube which holds a ferrule containing the fiber and fixedly positioning the terminal end thereof for predetermined spacing from the diaphragm. The disclosure also includes a novel method of mass producing the end-coated fibers in assembled relation with the ferrules.