Showing papers on "Fiber optic sensor published in 1978"

Fiber optic light delivery apparatus and medical instrument utilizing same

Abstract: Disclosed is a fiber optic fiber transmission line which transmits light a distance from its source and is terminated, at its light delivery end, by a second fiber optic fiber of a larger diameter than the first fiber. An interlocking connector keeps the first and second fiber in positive contact in an efficient light energy transmission relationship. A plurality of second fibers form a set of tips for use in causing light convergence or divergence at the transmission line output.

Viabilities of the Wavelength-Division-Multiplexing Transmission System Over an Optical Fiber Cable

Abstract: This paper describes the feasibility and the applicability of the Wavelength-Division-Multiplexing (WDM) system with two types of preliminary WDM transmission experiments. Through this study, it has become clear that WDM technologies play a major role in optical fiber systems and have the possibilities of realizing the various optical fiber transmission systems.

Fiber-optic acoustic sensor

Abstract: An optical fiber acoustical sensor for detecting sound waves in a fluid mum. An optical fiber coil through which a light beam is transmitted is placed in a fluid medium. A sound wave propagating through the fluid medium and incident on the optical fiber coil changes the index of refraction and the length of the optical fiber at the area of incidence. These changes cause a shift in the transmitted light which is detectable to denote the presence of the sound wave.

Monitoring arrangement utilizing fiber optics

Abstract: An arrangement for monitoring a particular condition, specifically temperature in a preferred embodiment, is disclosed herein and includes a sensor in the form of at least one optical fiber. This optical fiber cooperates with a light source and detector for sensing changes in the temperature being monitored and is accomplished by selecting the fiber such that the amount of light which passes through it varies with changes in temperature.

Fiber optic temperature sensor using liquid component fiber

Abstract: This invention provides apparatus for remote temperature sensing by means of fiber optics in which the sensor is optical and passive, with no electrical power required at the sensor. The temperature-sensing section of the fiber optic makes use of a transparent liquid as core or cladding and in which the transparent liquid has a temperature-dependent index of refraction.

Fiber optic heterodyne interferometer for vibration measurements in biological systems

Abstract: An optical heterodyne interferometer utilizing a fiber optic target probe and a digital phase compensation system is described. Optical performance and the effect of background motions on output are described. Maximum sensitivity for a simulated biological target in aqueous medium is 0.05 A Hz−1/2 for a signal‐to‐noise ratio of unity.

Fiber-optic circuit element

Abstract: A fiber-optic circuit element is provided of the type for coupling signal ght from a first optical fiber to at least one second optical fiber wherein at least one of the optical fibers has a free end which is controllably movable to be in or out of alignment with the other fibers. Movement of the free end of the fiber is achieved by an expansion layer applied to the fiber and acting as a heatable bimetallic element. Heating of the expansion layer can be achieved by absorption of electromagnetic radiation, including an independent source of control light and/or a portion of the signal light itself. Electrical heating mechanisms can also be used. This circuit element can be advantageously used without limit in optical switches, astable multivibrators, bistable multivibrators, optical resonators, and environmental temperature and pressure detectors.

Optical time domain reflectometer: comment

Abstract: Barnoski et al. developed a very useful method for mea­ suring the attenuation of optical fiber waveguides and the location and insertion loss of connectors or faults. In a recent paper they found experimentally that the power Pr Fresnel-reflected from the end of a step-index fiber was 12 dB above the power Ps backscattered from volume elements at the fiber end. For an ideal cleave they expected a value of 14 dB. The purpose of this Letter is to point out that this last statement is incorrect. The ratio of the power reflected Pr to the power backscat­ tered Ps is given by

Measurements in fiber optics

Abstract: Recent advances in optical-fiber technology dictate that attention must be given to establishing accurate and precise measurement techniques. In this paper measurements currently employed to determine the characteristics of optical fiber waveguides are reviewed. Included in the review are techniques for measuring attenuation, delay distortion, refractive-index profile, fiber diameter, and mechanical strength. Since establishment of accurate measurement procedures cannot be accomplished without some knowledge of the physical mechanisms controlling the parameters to be measured, a brief review of the dominant causes of attenuation and modal delay in fibers is also included.

Radiation characteristics of a tapered cylindrical optical fiber

Abstract: Output coupling of light from a conically tapered optical fiber is investigated. Such a technique may be used to provide “wide-angle” illumination from a single fiber of low numerical aperture. Experimental results for a series of fibers of varying taper angles are presented. It is found experimentally that light which is coupled out of a taper is widely dispersed when the taper angle is large. Based upon modified geometrical optics we present a theory which qualitatively predicts the experimentally measured radiation intensity patterns.

Optical fiber acoustical sensors

Abstract: This invention relates to an optical fiber acoustical sensor for sensing acoustic vibrations and in combination with an incoherent or coherent source of light such as a LED or a laser and a photo detector to determine the frequency and amplitude of the sound pressure variations. The invention consists of an element of optical fiber without cladding surrounded by a liquid or plastic potting material permeable to sound pressure and having an index of refraction slightly less than the fiber. The intensity of a light beam transmitted by means of fiber optic waveguides, single or multi-mode, from a source of light through the sensor to a photo detector varies with the variation of sound pressure to which the sensor is subjected. If the sensor is in water, the transmitted light intensity varies with the acoustical pressure in the water because the changes in liquid or plastic index of refraction changes with the sound pressure. Generally the fiber sensor is in an element preferably surrounded by a fluid which has an index of refraction close to but less than that of the fiber, and the coil thickness is small relative to the wavelength of the sound to be detected.

Fiber optic hydrophone for use as an underwater electroacoustic standard

Abstract: A fiber optic hydrophone for use as an underwater electroacoustic standard. The hydrophone includes a fiber optic acoustic wave detector in one end of the hydrophone which is subjected to incident acoustical waves. A similar fiber optic is in an acoustically isolated compartment where the optic fiber is not affected by the incident acoustical wave. Comparison of light passing through each coil will determine incidence of an acoustical wave on the detector fiber.

Parallel image transmission by a single optical fiber

Abstract: A nonscanning technique in which an image of a two-dimensional input transparency is transmitted in parallel through a single, round, step-index optical fiber is described. To ensure that the output display is not smeared, the input light distribution is first spectrally and spatially coded, and after transmission through the optical fiber it is decoded. Both coding and decoding operations are achieved solely by means of conventional, passive optical components.

Fiber optic loop signal coupler apparatus

Abstract: Fiber optic rotary coupler apparatus is disclosed in which a light signal formed in a continuous ring in a plane is transmitted between a barrel and a surrounding sleeve within which the barrel is rotatably mounted. The light signal ring is produced by a light source and an associated light transmitting fiber wound on the barrel in at least one complete circular loop of a radius such that a portion of a light signal introduced into an end thereof is transversely radiated from the fiber. Light detector means, which may include a further optical fiber for transmitting light signals to a remote detector, is carried on the sleeve. In one embodiment, a plurality of optical and electrical signal channels are incorporated into a single device.

Re-Entrant Fiberoptic Approach To Rotation Sensing

Abstract: We are investigating a new approach to inertial rotation sensing which we refer to as an active re-entrant Sagnac system (ARS). It is aimed at rotation rates extending to very low values, as required in such amplications as navigation, guidance and geophysical measurements. It employs a multiturn fiber optic loop containing an internal optical amplifier, and uses pulsed optical signals introduced by an external laser oscillator which make multiple recirculations around the loop. Its output signal is a time-sampled sinusoidal waveform having the same frequency as the beat frequency in a standard oscillating ring laser gyro (RLG) having the same loop diameter. Like the RLG, it is basically an integrating rate gyro, in which digital cycle counting is used to determine the angle turned through. It is basically free of the mode locking effect encountered with RLG's, and has prospect for higher sensitivity to rotation. Experiments using cw light are described, which include new re-sults on removing instabilities and environmental sensitivities from fiber gyros. Initial experiments on pulsed recirculation without an amplifier are described, which affirm the basic recirculation principle. Work is beginning on development of a fiber amplifier for use in a full ARS experiment.

Fiber Optics For Radar And Data Systems

Abstract: The application of fiber optics (FO) to modern radar system design is examined This paper presents the more conventional uses of fiber optics to transmit wideband signals as well as the less common use of their stable transmission delay characteristics to form active circuit elements within a radar The stable delay characteristics of fiber optic devices are exploited in the design of such radar circuits as a high frequency oscillator, phased array antenna, precision pulse generator, AID converter, MTI system and chirp generator The capability of fiber optics to transmit wideband information over long distances is being exploited to develop a radar remoting system for control, power, status, voice and video signals Three hundred signals are time division multiplexed over seven optical fibers for a distance of 1200 feet Future development of new materials for fiber optics will permit operation at IR frequencies and lower line loss for new applications

Applications of dual function electro-optic transducer in optical signal transmission

Abstract: A bidirectional optical fiber cable assembly that has electrical connectors on each end and a data bus employing same are disclosed, thereby facilitating the implementation of optical fiber communication links. The bidirectional optical fiber cable assembly uses a dual function diode which functions both as a light emitter and as a detector of optical signals. This diode, which is contained within an electrical connector at the end of the cable assembly, is connected by wires to the electrical terminals of the connector and is positioned against the end of an optical fiber, which transmits the signal along the fiber cable. The use of such a cable assembly in a data bus allows the design of a data bus in which the function of signal transmission is conducted by optical signals, a function for which they are best suited by virtue of resistance to electrical interference, and in which connection and distribution of signals is done electrically, a function for which electronics is better suited than is optics. A bidirectional optical communication system that communicates directly along a path in the air is also facilitated by the use of a dual function diode.

Fiber optics duplex module

Abstract: A duplex module for simultaneous bidirectional transmit-receive communication with the end of an optical fiber or fiber bundle. The end face of an optical fiber in optical coupling registry with one end of a common bidirectional transmit-receive optical path is tilted to divert any transmit signal back-reflected from such end out of such path. The other end of the transmit-receive path is affiliated with signal receiver and transmitter means via a beam splitter.

Optical fiber switch driven by PZT bimorph

Abstract: Optical fiber communications need optical switches. For a multimode fiber system, an optical fiber switch is suitable for a low switching loss. At present, an optical fiber switch has low switching speed. Short switching time in a system results in increased traffic handling capacity. In this Letter, an optical fiber switch driven by PZT bimorph is presented as one attempt at switching speed improvement. Chattering, which is one cause of low switching speed, is reduced by applying a multistep voltage. The 1 × 2 optical switch consisted of one movable optical fiber and two fixed optical fibers, as shown in Fig. 1. The movable optical fiber was driven by a PZT ceramics bimorph. The optical fiber used in this experiment was a multimode fiber of the step-index type with a 60-μm core diam and 150-μm outer diam. The bimorph was constructed with two Fig. 1. Optical fiber switch description.

Optical field mapping using single-mode optical fibers

Abstract: A new method of measuring the complete optical field distribution (optical field mapping) is proposed and is applied to the measurement of Gaussian beam distribution at its beam waist. This method utilizes an interference technique and uses two single-mode optical fibers as flexible paths. The interference pattern caused by the output beams from the reference fiber and pickup fiber directly gives the relative phase distribution at the input end. For the intensity and phase distribution measurements the experimental ambiguity is as small as 0.1 microm and 1/10 of the wavelength, respectively. Stability of the interference fringe against the distortion of the fiber is also examined experimentally.

End-butt optical fiber coupler

Abstract: An optical waveguide coupler having intersecting deep and shallow grooves in a planar solid substrate, in which the deep groove accommodates an alignment fiber for fine vertical alignment of an optical fiber with another optical fiber or with an optical component such as a switch, modulator, multiplexer or source of light. The shallow groove accommodates the optical fiber. The alignment fiber may be tapered or have any configuration such that its manipulation causes the alignment fiber to contact the underside of the optical fiber for raising or lowering the optical fiber. There may be a plurality of shallow and deep grooves for coupling more than one optical fiber.

Lightwave fiber tap

Abstract: This paper describes a device which samples the optical signal in an optical fiber for use in source stabilization via feedback control. This device incorporates a beam splitter formed on the fiber ends to deflect a portion of the light traveling down the fiber into a P-I-N photodetector. Advantages of this device include low insertion loss, an output that is relatively independent of the modal distribution within the fiber, and is a rugged small package.

Two-way single fiber optical communication system

Abstract: An injection laser diode is at one end of an optical fiber to direct modulated optical radiation into the fiber. At the other end of the fiber is a detector, such as a semiconductor photodetector, for the modulated radiation. Between the other end of the optical fiber and the detector is a reflecting shutter which is adapted to periodically reflect some of the radiation, at a lower frequency rate, back along the optical fiber to the injection laser. The radiation reflected back into the injection laser causes a variation in the characteristics of the laser so that the laser operates as a detector for the reflected radiation.

Optical fiber refractometry by interference microscopy: a simplified method.

Abstract: Index of refraction profiles of optical fibers are obtained by a new interference technique closely related to Mach-Zehnder microscope interferometry. Data are obtained from specially prepared samples using a conventional reflected light microscope. Excellent agreement is obtained with the results using the Mach-Zehnder method but at a considerable reduction in the cost and complexity of instrumentation.

Strain measuring method for optical fiber

Abstract: PURPOSE: To measure the mechanical strain toward lengthwise of the fiber by tensile strength, by measuring the delay in the propagation time of the light of fiber at cable manufacture. CONSTITUTION: The pulse from the generator 18 modulates the light of the light source 14, the modulated light reaches the photo detector 16 through the propagation in the fiber 10, the detection output is introduced to CRT 22, the output pulse of the generator 18 is delayed 20 and is given to CRT 22, and stationary pulse is pictured on the CRT. Next, when the fiber 10 is pulled toward lengthwise by using the tension unit 12, the output of the photo detector 16 is delayed in proportion to the elongation of the fiber and the delay in the propagation time can be observed on the CRT. COPYRIGHT: (C)1980,JPO&Japio

An Optical Fiber Diameter Measurement System Using Forward Scattered Light

Abstract: Forward scattering of light by an optical fiber produces an interference fringe pattern in which the fringe spacing is inversely proportional to the fiber diameter. An electrooptic system has been developed to produce and detect this scattering pattern, thus providing a measure of fiber diameter.

Optical microphone with rectangular fiber optics

Abstract: An acousto-optic transducer which may be employed in a telephone subscriber instrument is described in which movement of a diaphragm varies the degree of coupling between the ends of two rectangular optical fibers having rectangular cross sections and which are coupled to the diaphragm for linearly amplitude modulating light signals passing between the fiber ends.

Parallel transmission of a one‐dimensional light distribution by a single optical fiber

Abstract: A technique, based on the preservation of the axial angle, for transmitting one‐dimensional light distribution through a single multimode step‐index optical fiber is described. Extension to transmission of two‐dimensional pictures is demonstrated.