The use of optical fiber ring resonators to detect energy impulses is explored. These structures have limitations to their frequency response set by their dimensions and the speed of sound. For energy impulses which are slowly varying with respect to this intrinsic response time, the ring resonator generates a string of optical pulses. The frequency of this optical pulse train is a measure of the energy deposition rate and the total number of pulses is a measure of the total energy deposited. However, for energy impulses short compared to this intrinsic response time, the ring resonator behaves as a shock excited mechanical oscillator. Under these conditions the amplitude of oscillation is proportional to the total energy contained in the impulse. The sensitivity to various forms of energy can be optimized by a suitable choice of coating.

An RF optical modulation technique for multiplexing and self-referencing a number of transmissive analog fiber optic intensity sensors has been extended to work with reflective fiber optic sensors and switches. Two sensor configurations, each utilizing a linear RF ramped optical signal, were investigated. In the first "star" configuration, reflective optical transducers were located at the ends of a multiport splitter, representing 3 bits of digital data and one signal used for intensity self-referencing. The second configuration involved using self-referencing reflective sensor modules connected in series. Light in each module was coupled out of the transmission line, passed to the reflective transducers, reflected, and reinjected into the transmission line. In each system, the reflective sensor's return signals were detected and electrically mixed with the input resulting in beat signals of different frequencies corresponding to the sensor arms' differing path lengths. Self-referencing compensated for source fluctuations and varying optical loss characteristics between the sensor modules and the signal processing location. The theoretical basis of the technique is presented and experimental results are given.

An intrinsic multimode fiber-optic pressure sensor that is capable of measuring a specified range of dynamic (fast rise time) high-pressure impulses is discussed analytically and empirically. The sensor uses the pressure-induced microbend loss phenomena incurred by propagation modes of multimode fiber as its primary sensing mechanism and a pressure-induced refractive index change as a secondary effect. Several related variations of this fiber-optic pressure sensor are presented and compared in relation to their (1) pressure sensitivity, (2) ease of construction, (3) durability, and (4) environmental versatility. Two other measurement schemes are also discussed. Moreover, a high-impulse pressure-shock tube that is currently under construction will be discussed, along with a composite summary of the experimental results.

Optical fibers have an inherent capability of transmitting high bandwidth analog and digital signals. To apply this property of fiber optics to remote sensing, special sensing heads as well as signal processing electronics have to be developed. In systems employing intensity modulating sensors, there is also a need for a referencing technique to compensate for changes in the transmission of the connecting fibers and light source intensity. This paper discusses fiber optic sensing systems using intensity sensors incorporated in sensing heads of a special configuration. Different modes of operation as well as resonant conditions are explained. Theoretical and experimental analyses are also given.

This paper explores the use of a new velocity measurement technique that has several advantages over existing techniques. It uses an optical fiber to carry coherent light to and from a moving target. A Fabry-Perot interferometer, formed by a gradient index lens and the moving target, produces fringes with a frequency proportional to the target velocity. This technique can measure velocities up to 10 km/s, is accurate, portable, and completely noninvasive.

We have developed a radiation-to-coherent light converter (RCLC) with a monolithically integrated semi-conductor chip that consists of a chromium-doped GaAs photoconductor detector and a GaA1As laser diode. When irradiated, the electric pulse generated by the photoconductor detector modulates the laser diode, which has been biased above the lasing threshold, thus converting a radiation pulse to an electric pulse and then to a light pulse. The laser pulse is then transmitted to a fast recorder through a high-bandwidth optical fiber. In the absence of a single-step x-ray pumped laser, our converter appears to be the first integrated device that can efficiently convert x-ray flux into coherent light. This device has been tested successfully with the 50-ps electron beams of a 17-MeV linear accelerator and with 50-ns x-ray pulses from a Z-pinch plasma source.

Photoconductive x-ray detectors are becoming an important x-ray diagnostic as a result of their small size, fast response time, and high sensitivity. We are developing a discrete array of neutron-damaged GaAs detectors to be used in an imaging x-ray spectrometer, and we describe herein the techniques we use to fabricate and characterize them for an upcoming experiment. Using a 225-ps x-ray pulse from a laser-produced plasma, we measured the sensitivity and time response of the detectors to be 7.1 mA/W and on the order of 150 ps FWHM, respectively. The carrier mobility is 741 cm2/V.s at a bias of 2 x 104 V/cm.

Because the time resolution requirements of experiments at the Nevada Test Site exceed the capabilities of traditional electrical analog cable, fiber optic analog diagnostics systems have become attractive. A number of different instrumentation systems are possible using commercially available laser-diode transmitters. In addition, the fiber optic systems designer has a choice of receivers, operating wavelengths, and fiber types. We will compare the system performance of 810-nm systems with both single-mode and multimode fiber as well as 1300-nm single-mode fiber systems with both a photodiode oscilloscope and a laser-diode streak-camera receiver.

A 3-GHz bandwidth fiber optic analog transmission system has been prototyped using directly modulated 1.3 μm InGaAsP semiconductor laser diodes. The low loss dispersion-free window in singlemode fiber at 1.3 p.m allows the signal to be transmitted almost ideally. A high bandwidth photodiode/amplifier pair converts the signal back to an electrical form where it is recorded on a 6-GHz transient digital oscilloscope.

A high-bandwidth analog data link using a Mach-Zehnder integrated optic modulator has been constructed. We discuss the parameters involved in the system design, the major problems encountered, and the particular solutions at which we have arrived. The present system uses a diode-pumped YAG laser at 1300 nm and a low-loss Mach-Zehnder interferometer to achieve a large, low-noise optical signal. An InGaAsP photodiode detector followed by a 20-dB wide-band amplifier converts this to an electrical signal for recording on a Tektronix 7250 oscilloscope. We also present some preliminary measurements of the system performance.

We present preliminary data on the fidelity of an analog optical data link operating at 830 nm. This data link encodes an electrical signal on an optical carrier by the action of a commercially available integrated-optic modulator, a 2x2 switch, from Crystal Technology, Inc.(CTI) An optical streak camera is used to record the modulated optical carrier. With this single-shot system a precision of 2-5% is realized. The dynamic range of the system is approximately 30 dB (power). The present system bandwidth is limited to 3 Ghz by the CTI modulator. New modulator designs using travelling wave structures will soon extend the system bandwidth to around 10 Ghz. We discuss the potential for development of a high-fidelity multichannel analog link based upon this technology and the potential impact on instrumentation for the measurement of ultra-fast single-transient phenomena.

A wide band (> 1 GHz) fibre optic data link for measuring fast radiation signals has been developed. The system operates at the 1300 nm fibre optic transmission window and uses Cerenkov radiation as the radiation-to-light conversion process. At the recording end of the fibre p-i-n diode detectors and broad band amplifiers are used to give high sensitivity and bandwidth.

A new method for wideband signal processing using a reflectively tapped fiber delay-line is described. Dielectric mirrors as taps are incorporated into a continuous length of optical fiber by an electric fusion splicing technique. Demonstration of this processor as a frequency filter in the gigahertz regime is described. A variable tap technique based on fiber Fabry-Perot interferometers is suggested.

A spark gap trigger monitor (SGTM) system has been developed to monitor the relative timing accuracy of up to 12 spark gaps. The SGTM employs light from the spark gaps to provide timing information. The SGTM is now in use on a six-stage Marx generator. In addition to monitoring normal performance, the SGTM also helps diagnose problems and faults in the trigger system.

In order to provide optical to electrical conversion of high speed analog signals, an avalanche photodiode receiver must be optimized for several parameters. Among these parameters are receiver amplifier noise, APD noise, and bandwidth.

The realisation of high speed, high gain, wide dynamic range analog optical receivers requires to optimize the receivers structure and the components choice. At the beginning will be discussed the constraints to make high speed, high gain, wide dynamic range analog optical receivers, the way to choose different constitutive elements and their influence on performances. Emphasis will be put on avalanche gain, transimpedance value and optical coupling in reference with dynamic range. As an application of this, the description of a field receiver will be given, showing some technological solutions. As a conclusion, some informations on the measurement equipments dnd methods will be given.

By using general LPE technique, the 1.3 um double carrier confine (DCC) structure laser with high Tο value. Composition matching of two active layers, doping concentration and growing condition are strictly controlled. The radiative recombination probability of super hot carriers which are generated by Auger recombination and leaked process from the first active layer is increased, so that the carriers leak into InP clad layer are decreased. Tο of DCC structure InGaAsP/InP semiconductor laser is as high as 150 K in the operating range of 293-343 K. The relationship between spontaneous emission spectrum and injected current density for DCC laser is discussed. The influence of active layers composition matching and thin sandwich layer thickness on the threshold current density and T. are analysed. Far-field pattern of 1.3 um InGaAsP/InP DCC structure laser is calculated by strong coupling method. Experimental data agree with the theoretical results and the FAHP beam divergence Q<30°. The space coherence property of this double active layers DCC waveguide structure laser is good.

An isotropic, photonic electric-field meter (PEFM-15) having 15 cm resistively tapered dipole elements and Pockels effect electro-optic modulators is used to measure electric fields of 10 to 100 V/m from 10 kHz to beyond 1 GHz. The probe's frequency response is flat within ±3 dB from 30 kHz to 100 MHz except for a region between 1 and 10 MHz where acoustic resonances occur in the LiNbO3 modulator crystals. For a 3 kHz detection bandwidth, the noise equivalent field is approximately 7 V/m, thereby giving a calculated linear dynamic range of 68 dB in field power density. The probe's isotropic response is flat within ±2 dB, and the response of each dipole closely follows the curve predicted by theory. An optical-beam switch that connects the individual dipoles to a laser source and optical receiver is also described.

The edge of a transmission window for a GaAs Bragg cell starts about lum, which allows this material to be used for infrared fiber-optic applications, especially at 1.3um and 1.5um. The single crystal of GaAs is acoustically anisotropic and has the highest figure of merit, M2, along <111> direction for a longitudinal mode sound wave. Recently, Brimrose has designed and fabricated an acousto-optic modulator from GaAs operating at a carrier frequency of 2.3 GHz with a diffraction efficiency of 4%/RF watt.

Theoretical studies of backward collinear acousto-optic interactions (BCAOI) in bulk single crystals and single mode glass fibers are described. At very high acoustic frequencies the acoustic wavenumber ka of the guided acoustic waves can be twice of the optical wavenumber ko of the guided optical modes. Thus the incident optical mode propagating in the forward direction is. coupled to that in the backward direction dud to the index grating induced by the guided acoustic mode propagating in the collinear direction if ka = 2 ko. High efficiency is a achieved due to excellent matching between profiles of the electromagnetic fields of incident, diffracted optical beam and the acoustic displacement as well as long interaction length. On- and off- line fiber optic signal processing devices such as frequency shifters, tunable filters, switches and modulators may be built using such BCAOI. Practical considerations for these devices are discussed.

We have qualitatively tested four prototype streak cameras designed and built by Kentech Instruments, Ltd. of London. The unique design of each camera incorporates an intensified image tube and all of the supporting electron-ics into a small package. This paper presents test data obtained to date; the state-of-the-art measurement techniques used; the test results, which graphically demonstrate photocathode sensitivity, useful dynamic range, static and dynamic fidelity, and gating-extinction ratio; and other information.

We have developed a high-bandwidth, photon-counting, x-ray detector for x-ray imaging experiments. It consists of an x-ray photocathode, an optional microchannel plate (MCP), optional electrostatic optics, and a subnanosecond phosphor. The detector can be used for two-dimensional imaging with a subnanosecond framing camera or one-dimensional imaging with a Reticon or streak-camera readout. Several versions of the one-dimensional detector have been developed. The MCP version employs a photocathode on the front surface of the MCP, and the transmission-photocathode version consists of a photocathode deposited on a thin polypropylene foil. The output electrons from the MCP or the transmission photocathode are accelerated into a fast phosphor deposited on a coherent fiber-optic faceplate. Both detectors can be enhanced with the use of electrostatic electron optics to compress the output electrons in one dimension. The best parameters achieved to date are a time resolution of 400 ps, spatial resolution of 100 ,um, and electron compression of 10:1. Quantum efficiencies of 40% have been achieved. Effective quantum efficiencies greater than 100% have been achieved with the one-dimensional electrostatic optics. Data are presented on the efficiency, time response, and spatial resolution of the one-dimensional detectors.