A brief overview is presented on the subject of the development of more radiation tolerant fiber optic waveguides. Data are presented for both polymer clad silica (PCS) and all silica fibers. The effects of new compositional variations on radiation response in both the core and cladding glasses are reported. Recent photobleaching measurements on irradiated fibers are also summarized. The spectral variation of the observed radiation--induced losses are given for a variety of state of the art fibers during and following exposure to ionizing radiation.

Damage sustained by optical fibers from exposure to ionizing radiation has generally been determined by transmission measurements with the data reduced to induced absorption of signal as dB/km. Thermoluminescence (TL) has been used in conjunction with transmission measurements to determine the depth of the traps responsible for the absorption increase in aluminum jacketed waveguide. In Si02-Ge02-P205 fibers, two TL peaks have been found. One is transient at 403°K and the other is permanent at 653°K. These peaks have been found after 30K rads (Si) dose of gamma rays from a 60Co source. Following the paper by van Gorkum, the kinetics for the TL emission from the "permanent" peak has been determined as 2nd order. The "attempt to escape" frequency, S, has been calculated to be 7 x 109 sec-1. This would seem to imply that there is a non-radiative emptying of traps, and repopulation of emptied traps at the elevated temperatures. Spectral evidence indicates that most of the emitted light is in the 0.450-0.480 μ region. Transmission tests at 0.82 μ taken in situ during the irradiation show that the induced absorption is linear with dose. The induced absorption losses are lower than previously reported for low phosphorus content fibers. The transmission measurements indicate that a peak in radiation sensitivity occurs at around 1-2% (mol) P205. Fibers with 10-15 mol % P205 show markedly lower radiation damage, as evidenced by relatively low induced loss, and lower TL peak height. This research is partially supported by the U.S. Army Research Office under Contract DAAG-29-80-C-0139.

Transient absorption in optical fibers has been studied with emphasis on fast absorption components. Radiation damage was induced with a Febetron 706 electron accelerator, modified to deliver an electron pulse width of 1.1 ns. Dye lasers were synchronized to the accelerator to provide a light pulse through the fiber during the radiation pulse. The output light pulse was detected with a biplanar vacuum photodiode. Four scope traces were used on each electron pulse to monitor the Febetron output, the input drive pulse, and two records of the output pulse on two sweep speeds. Detailed data were acquired for times less than 100ons after irradiation. An insulated enclosure was used to vary fiber temperature from -30 C to +250 C. Several fibers were studied with emphasis on ITT T303 PCS fiber. Data were acquired at 600 and 850 nm. Theoretical modeling of the data will be presented.

A set of eight polymer clad silica (PCS) fibers from Quartz & Silice with varying water content, cladding thickness, and cladding material type have been exposed to 50 nsec wide X-ray pulses at different temperatures (-45°C, -25°C, 0°C, +25°C) in order to study the effect of fiber parameters and temperature on the extent of X-ray induced transient attenuation at typical LED wavelengths (820 nm, 900 nm, 940 nm, 1060 nm). Our results indicate that, relative to other fiber parameters, the presence of water suppresses the transient attenuation in these fibers especially at the longer wavelengths and lower temperatures. Both the peak transient attenuation, ap, and the normalized transient attenuation, α (t)/αρ, increased with decreasing temperature as one might expect for thermally-limited recovery processes. The peak trans-ient attenuation also increased with decreasing wavelength, with the wavelength dependence being stronger in the wet fibers. Within the limits of this experiment, the cladding characteristics had no effect on the fiber response to irradiation. Thus, in spite of the fact that the presence of water leads to greater intrinsic fiber attenuation between 900 nm and 1000 nm, its presence is beneficial to low temperature fiber behavior in an ionizing environment.

Germanium phosphosilicate and germanium borosilicate,fibers doped with cerium were fabricated and tested for their responses to steady-state Co60 radiation at -55°C, +20°C and +125°C. A fiber with germanium, boron and phosphorous in the silicate core and doped with antimony in the core and clad was similarly tested. All of the fibers showed significant improvements in radiation hardness at 20°C compared to undoped fibers of the same base composition. At -55°C, however, all except the cerium doped germanium phosphosilicate were very radiation sensitive and also showed increases in the rate of induced loss at +125°C. The cerium doped germanium phosphosilicate fiber showed virtually no change in radiation sensitivity at the temperature extremes and could prove useful in applications requiring relatively short lengths of fiber.

Measurements were performed on gamma irradiated plastic clad silica (PCS) and all-glass fibers over the temperature range 23°C to -60°C. The effects of temperature, [OH] content and low dose, long term radiation are examined on various fibers. Particular emphasis is placed on the induced optical attenuation and recovery behavior for a carefully controlled sample of PCS fibers.

The effect of steady-state ionizing radiation on glass-clad fiber-optic waveguides is discussed as a function of wavelength and temperature. Doped-silica and pure-silica core fibers are considered. Fibers showing reduced radiation-induced losses are identified for use at various operating wavelengths over a wide range of temperatures. Attention was given to fiber composition and fabrication technique. The radiation effects data are discussed in terms of signal transmission length of fiber for various information data rates.

Fiber-optic cables are being considered for use in environments where they will be exposed to a potentially damaging thermal radiation pulse. Recognizing the seriousness of this problem, the Harry Diamond Laboratories (HDL) initiated a program designed (a) to test cables in pulsed thermal environments, (b) to identify the damage modes and damage levels of these cables and (c) to develop hardening measures. Tests were performed at the White Sands Solar Facility (WSSF) by Baba, Share, and Wasilik1 on a limited number of fiber-optic cables; results indicated that cable damage--breaching of the cable jackets--occurred in the 30 to 80 cal/cm2 range. Based on these results, hardening techniques were developed; these techniques use thin aluminum and/or white Teflon tape either wrapped over the outer cable jacket or placed under transparent cable jackets. Since these initial tests, other commercial cable types have been tested; in addition, other nonmetallic hardening techniques, which use thin silicone rubber, glass cloth, PVC, or polyimide, have been investigated at thermal fluences up to 150 cal/cm with an associated maximum thermal flux around 80 cal/cm2s. The tests were performed at WSSF and at a Quartz Lamp Bank facility (QLB). All but the thickest cable jackets were found to be "thermally thin" for most of the pulse widths used in this investigation; thus, variations in flux, pulse shape, and pulse width generally had no appreciable effect on damage if the fluence and spectrum were constant. However, much larger fluences (by a factor of 2 to 3) were required at the QLB to produce damage equivalent to that observed at the WSSF. It was concluded that these large differences in damage fluences were due to the differences in spectra between the two sources.

In addition to their small size and light weight, the unique properties of fiber optic cables such as immunity to EMI/EMP, high data capacity and ability to be non-conductive are frequently of value in applications where the environment can be termed severe. Environments of severe nature are encountered in military field communications, underground nuclear testing, oil refinery instrumentations, electric utility installations and submarine telecommunications. This paper discusses two specific applications where severe environment is encountered and reviews the fiber optic cable design in each case.

Graded-index fiber in a loose-sheath cable experiences optical power losses due to bending at cold temperatures. This bending is due to the more rapid. contraction of the loose sheathing relative to the fiber. The bending produces localized. changes in the density of the glass which disturb the waveguiding effect of the graded-index fiber and decrease the transmitted optical power. In recent experiments fiber optic cables have been tested at temperatures ranging from -100°C to +23°C. Significant but reversible optical power losses and a marked hysteresis have been observed. when SIECOR 122 and 222 cables have been gradually cooled from room temperature to -100°C and then returned to room temperature. Cables ranging in length from 9 to 24 m have been tested, giving an average increase in attenuation at -100°C of 0.150 db/m.

Optical communication via hair-thin silica waveguides has revolutionized the telecommunications industry. Because its uses are spreading beyond telephony, with its relatively benign environments, to more exotic undersea and space applications, a new emphasis is now placed on optical fiber strength and fatigue characteristics. This paper will trace the historical development of optical waveguides strength/fatigue experiments and a recent attempt to determine the material fatigue constant "n" of modern silica waveguides. Stressing practical application, detailed derivations have been purposely left out for the sake of brevity.

The development of long distance optical fibers and electro-optical components have made new approaches for ocean-laid telemetry systems possible. One such approach being investigated at the Naval Ocean Systems Center (NOSC) is an air-deployed fiber optic system (ADM utilizing a small diameter, repeatered, fiber optic communication cable, 1600 kilo-meters in length. This paper addresses the problems associated with the development of such a cable system, designed to be deployed by an aircraft over deep oceans and provide a telemetry path for information data exchange. Rather than discuss electro-optical issues, this paper discusses the issues associated with deploying a cable; 1 mm in diameter, and repeaters from an aircraft flying at 130 - 150 knots. The simulation of high-speed cable deployment, including hardware descriptions of winding apparatus and pullout test equipment, are also presented. Problems associated with laying small, ruggedized optic fiber on the ocean floor and the design of a small, ruggedized optical cable for such ocean deployment are discussed.

This paper reports on photodiode structures designed and fabricated to reduce unwanted ionizing-radiation induced noise currents without significantly reducing the optical sig-nal currents. For the optical wavelength range from 0.7 µm to 1.4 μm, we have studied three types of photodiode structures fabricated from GaAlAs/GaAs, GaAlSb, and InGaAsP compound semiconductor materials. In addition, we compare the results of testing these specially designed direct bandgap photodiodes with commercially available direct and indirect hand qap photodiodes in an ionizing-radiation environment.

Concurrent with the development of optical fibers for telecommunication applications many different coating (buffer) systems have been utilized. Each system has sought to preserve the optical characteristics of the fiber as well as fiber strength. Composite UV-cured acrylate coatings were developed to meet these requirements. This paper reports the results of environmental testing. The benefits of acrylate coated fibers to both the cable manufacturer and end user are discussed including practical stripping techniques.

The Army is actively engaged in the development of fiber optics for tactical communications. Efforts have been underway in the development of fiber optic components that satisfy the unique requirements of the military environment. The major issues related to survival of fiber optics in the field are discussed. The militarized cable and connector, and underlying needs for high strength, fatigue resistant optical fibers able to survive the tactical nuclear environment are presented.

Fiber optics offers many advantages over conventional wire systems; they include low weight, large bandwidth capacity, simple architecture for data bussing, EMI invulnerability, and cost effectiveness. However, present-day fiber optic technology cannot meet the requirements of the most adverse space environments. The adverseness of the environment is primarily attributable to high-dose radiation and temperature extremes in a space vehicle. The technology to compensate for these problems is presently available, but developmental money would be needed, since commercial applications do not require survivability in such an environment. Initial development costs, along with the lack of sufficient reliability data, are deterring the adoption of fiber optics in space programs.

This paper describes two complementary fiber-optic experiment packages that are under development for orbital exposure on the Shuttle Long Duration Exposure Facility. The intent of the experiment is to take the first step toward providing the experimental confidence and design data necessary for application of optical fiber technology on NASA spacecraft and military. satellites. Four active fiber links will be monitored at predetermined intervals on each experiment, and other components and fibers will be exposed passively. Results from the experiment will be presented in planned future publications.

Wavelength multiplexing will be described as a concept for civil aviation fiber optics data distribution systems. Characteristics of the lasers, transmitters, optical coupler multiplexer, dielectric filter-beam splitter demultiplexer, and receiver will be described.

A fiber optic data bus topology is introduced which avoids both the "central failure point" problem that afflicts single star topologies and the intermessage dynamic range problem evident in systems using directional couplers.

A review of NASA programs which focus on the use of fiber optics for aircraft engine/inlet control is presented. Fiber optics for aircraft control is attractive because of its inherent immunity to EMI and RFI noise. Optical signals can be safely transmitted through areas that contain flammable or explosive materials. The use of optics also makes remote sensing feasible, eliminating the need for electrical wires to be connected between sensors and computers. Using low level optical signals to control actuators is also feasible when power is generated at the actuator. For engine/inlet control applications, fiber optic cables and cornectors will be subjected to nacelle air temperatures. These temperatures range between -55°C to 260°C. Each application of fiber optics for aircraft control has different requirements for both the optical cables and optical connectors. Sensors that measure position and speed using slotted plates can use lossy cables and bundle type connectors if data transfer is in the parallel mode. If position and speed signals are multiplexed cable and connector requirements change. Other sensors that depend on changes in transmission through materials require dependable characteristics of both the optical cable and optical connectors. A variety of sensor types are reviewed, including rotary position encoders, tachometers, temperature sensors, and blade tip clearance sensors for compressors and turbines. Research on a gallium arsenide photoswitch for optically-switched actuators that operate at 250°C is also described.

Scintillators have been employed for several years as ionizing radiation-to-light converters in plasma diagnostic experiments that utilize fiber optics. Until recently, nano-second and subnanosecond scintillators were available only in the near ultraviolet.1 However, the bandwidth and transmission properties of fiber optics both strongly favor operation at longer wavelengths. More recently, nanosecond and subnanosecond scintillators with emission peaks around 480 nm have been reported.2 A time-resolved plasma-imaging experiment using one of these scintillators and 100 channels of graded-index fiber, each 500 m long, has been successfully tested on a nuclear event at the Nevada Test Site. During the past year we have developed several new scintillator systems with emission wavelengths more compatible with fiber optics and with response times in the nanosecond andsubnanosecond time region. One scintillator, based on Kodak dye 14567 (DCM), has an emission maximum at 650 nm and a response time (FWHM) of 1.2 ns. Experimental data on system sensitivity and bandwidth versus fiber length are presented for three fluor-fiber systems. Data on fluor formulation, response time, and linearity-of-response are given, and a model for scintillator nonlinearity, based on solvent, radiation-induced, transient absorption, is presented.

Optical fibers coupled to a scintillator and a photosensitive device are incorporated into our plasma diagnostic instruments to investigate subnanosecond high energy CO2 laser-target interactions. These detectors incorporate features for miniaturization and high temporal resolution. However, we are faced with the serious problem of radiation generated in the fibers by relativistic electrons and high energy x rays. Use of spectral filter and relay optics, and appropriate signal subtraction, it is possible to overcome some of the difficulties and obtain useful information.

The use of fiber optics in the diagnosis of hostile nuclear environments has brought about a pressing need for the development of suitable radiation-to-light converters. These converters must meet stringent diagnostic requirements of linearity and time response while having a wavelength of emission that is compatible with transmission over relatively long lengths of optical fibers. In this paper we describe initial investigations of two, near-infrared-emitting semiconducting materials--CdTe and GaAs. Data are presented on the wavelength of emission, linearity, time response, and relative efficiency of these semiconductors. Most data were taken at 77 K because of a dramatic increase in efficiency at this temperature. Measurements show that the intensity-vs-dose curves are linear over several decades of useful input levels. Measurements indicate that GaAs has an efficiency and time response that promise to be useful in diagnostic systems. Radiation-damage effects are briefly discussed. Finally, the future direction of these investigations and possible applications in nuclear-test diagnostic systems are reviewed.

A system for high-frequency recording of plasma diagnostics has previously been reported. Substantial improvements have been made in the system response, dynamic range, and calibration of the system. Plastic-clad silica fiber is used as a radiation-to-light converter using the Cerenkov process. A spectral equalizer device is used to compensate for the material dispersion in the fiber, increasing the frequency response (,1 GHz-km) and the dynamic range (a factor of >20 over a FWHM 1 nm, 50% transmitting interference filter). The calibration system uses a pulsed injection laser diode (<100 ps FWHM) injected into the fiber at the radiation end of the fiber and detected by a microchannel plate photomultiplier tube on the recording end. The injection laser diode is triggered by a synchronous trigger delay unit, which also triggers a sampling or real time scope after as much as 10 μs delay with <50 ps jitter. The system improvements will be desribed in more detail and the utility of these components in other plasma diagnostic systems will be discussed.

This report gives the preliminary results on work done to find a scintillator that is compatible with high-bandwidth, long-distance fiber-optic transmission. The requirements for such a scintillator are 1) emission in the near-IR; 2) linear output over 2-3 decades of input excitation; 3) time response <2 ns; and 4) immunity to radiation damage. The behavior of single crystal cadmium sulfide (CdS) and cadmium selenide (CdSe) was examined under electron and laser excitation. Both crystals emit in the deep red, however, time response was found to be slower than 2 ns. Neither crystal exhibited good linearity over the entire range of input excitation.

Fiber-optic transmission lines are being used with increasing frequency in the demanding environment of nuclear device diagnostic tests at the Nevada Test Site. Previous reports have described diagnostic experiments that utilize properties of fiber-optic cables to provide capabilities that are extremely difficult to obtain with coaxial cable systems.1 This paper describes an imaging experiment conducted during the last quarter of 1980 at the Nevada Test Site involving 152 -0.6-km long GI fibers in 18 cables. An imager cell sensitive to neutron and gamma radiation was located at -8 m from the source. Individual elements of the fluor were coupled by -10 m PCS fibers (for radiation damage resistance) to the GI fibers used for the uphole and surface lines to the detector station. Light from the imager cell in a 9-nm band, centered at 540 nm, was detected by photomultipliers and the electrical signals then recorded on oscilloscopes. Overall system bandwidth, including the fluor, was -80 MHz. Due to the complexity of the experiment and the conditions associated with field testing, the PCS and GI fibers were cut and terminated under laboratory shop conditions prior to installation at the field site. Procedures used for quality assurance of the fiber assemblies as well as procedures used in checking fiber throughput during installation are described. The application of a large star coupler (5 input x 200 output fibers) used for system time and amplitude calibration and an attempt to "shutter" fibers with neutrons for a multiplexing application are also discussed.

Two neutron imaging experiments using fiber optics have been performed at the Nevada Test Site. In each experiment, an array of scintillator fluor tubes is exposed to neutrons. Light is coupled out through radiation resistant PCS fibers (9-m long) into high-bandwidth, graded index fibers. For image reconstruction to be accurate, common timing differences and transmission variations between fiber optic channels are needed. The calibration system featured a scanning pulsed dye laser, a specially designed fiber optic star coupler, a Tektronix 7912AD transient digitizer, and a DEC PDP 11/34 computing system.

Fiber optic cables were selected to transmit the command and data signals for a new EMP simulator, which will test the vulnerability of electronic systems to high intensity pulse electro-magnetic fields. The transient fields generated by the simulator induce large pulse currents in all coaxial cable and power wiring, and on the surfaces of all electronic enclosures in the vicinity of the EMP simulator sufficient to burn out unprotected electronics. Since no conductive current is induced on the all dielectric fiber optic cables, a major source of spurious signals and circuit damage was eliminated. The transmitters and receivers were essentially EMP hardened to protect from currents induced on the electronic enclosures. Two fiber optic data links transmit individual trigger signals with 1 ns rise times from the command and control center to the two Marx generators situated on either side of the center of the horizontal dipole antenna of the simulator. Two additional fiber optic links transmit, back to the command and control center, the output from probes measuring the voltage developed across the Marx generators. These analogue data links have a 5 ns rise time and a 40:1 signal to peak noise ratio. The data links are 450 m long.

The report describes a wideband linear response fiber optic transmission link designed to telemeter signals from a system being irradiated in a space/radiation simulator. The environment is severe: the transmitter must withstand an x-ray pulse delivering 109 rad(Si)/sec (surface dose rate), beams of 300 - 1000 KeV electrons, hard vacuum, and liquid nitrogen temperatures without degradation or even momentary upset. Radiation hardness is achieved by a combination of circuit design and high-Z shielding, including an optical fiber shield made of non-conducting lead-loaded. polyethylene. Special heat. conducting and insulating measures are employed to maintain temperature. The transmitter measures 15 x 8.5 x 9.5 am and operates on self-contained batteries. Signal bandwidth is greater than 10 KHz to 400 MHz with approximately 35 dB, of dynamic range. Signal inputs ranging from one millivolt to several volts are accommodated; four single-or double-ended inputs are provided, with remote selection. The single-fiber coupled remote control also allows adjusting input. attenuation, power and calibrator control, and verification of transmitter function. The single-mode laser used as the high frequency optical source is microwave dither-blased1 to reduce modal noise.

The potential advantages of fiber optic systems in adverse environments have generated considerable interest in the development of data links for use in ionizing-radiation environments. One important facet of this application area is the desirability of being able to operate under moderate to high dose-rate conditions. This paper discusses the problems involved in the design of fiber optic transmitters and receivers for use in such environments. Experimental data on several fiber optic transmitters and receivers, which were designed for operation in transient environments, will be presented. These experimental tests were performed using a flash x-ray machine at dose-rates up to and exceeding 109 rads/sec.

The development and use of two optical fiber systems for the Antares 40 kJ CO2 laser is described. In the Antares power amplifier, electron guns produce a discharge sustaining 8 kA beam of 500 kV electrons. Eight 300 kJ, 3 μs Marx pulsers provide a direct electrical pumping discharge through the laser gas. The electro-optic systems developed allow the measurement of pulsed analog waveforms and trigger timing information within the laser and power systems by a computer based control and data acquisition network.* Each fiber optic system consists of a signal powered transmitter, a fiber optic cable, and an optical receiver that interfaces through a CAMAC module to the data acquisition network. The data channels are capable of operating with 1.2 MV of common mode voltage in the electromagnetic interference environment, 500 kV/m and 50 kA/m, produced by the Marx pulsers. The analog transmitters send 10 MHz bandwidth information to CAMAC waveform digitizers in the data acquisition system. About 200 data channels monitor voltage and current in the pulsers and current density in the laser power amplifiers. The laser transmitters send 2 ns resolution timing information from each stage of the Marx trigger amplification and the Marx output to CAMAC time-to-digital converters. These 120 channels of information are processed to provide prefire diagnostics for the energy storage systems.

A large number of fiber optic cables were used in support of a neutron imaging experiment at the Nevada Test Site. This paper describes the quality control testing of fiber compo nents used on this experiment. The principle reason for quality control testing was to ensure reliable, high transmission fibers; a secondary reason was to gain data on a large sample of fiber cables in the field. Also described is the instrumentation developed for carrying out these field measurements. The design of the quality control instrumentation was a compromise between accuracy and simplicity of use.

A system is being developed to record temporally and spatially resolved data after transmission through 1 km of optical fiber. Wavelength multiplexing techniques are used to transmit many spatial points over each 62 1m fiber. Light from the output end of each fiber is de-multiplexed back into a spatial line. Four lines of data are focused sequentially across the input face of an RCA streak tube. System sensitivity is increas-ed by coupling a microchannel plate image intensifier to the streak camera output. The image intensifier output is recorded on film. The streak camera gives 200 spatial points at a 25% CTF over a dynamic range of 20 db. The total usable streak length is 120 ns with a resolution of 600 ps.

A cost effective fiber optic uplink for video information has been designed and successfully tested in a shallow water (i.e. < 20 meters) environment. The camera and transmitter are operated within a diver held underwater light housing. A novel fiber optic housing penetrator has been designed and tested down to a depth of 1200 meters. The receiver on the surface can drive a monitor or video tape recorder. As tested the system provides ample margin for much longer link distances. Quantitative information (e.g. heading or depth) can be superimposed on the video data for display. A preliminary design expanding the link to include a bidirectional capability allowing a lower frequency (control data) downlink is also discussed.

This paper reviews the application of fiber optics in the high voltage substation environment. Present applications as well as future uses for fiber optics are discussed. The larger scale use of fiber optics for data transmittal to a transient monitoring laboratory from a variety of remote primary transducers and the use of optical fiber as a data link from line potential to ground are highlighted as applications presently in service. These applications are used in projects sponsored by the Electric Power Research Institute. Rationale behind the use of optical fibers in several applications are presented along with the authors' practical observations of the advantages and obstacles of using fiber optics and electro-optics in the utility environment.

Commercial fiber optic cables, both bundled and single-fiber, were evaluated for application in an in-line photometer being developed for monitoring uranium and plutonium concentrations in high radiation environments in nuclear fuel reprocessing plants. The attenuation of the optical signals due to both the radiation damage and to the couplings between lengths of optical cable was determined for specimen cables. An ultraviolet enhanced fiber bundle demonstrated good radiation resistance to a total dose of 108 rad, which is the dose estimated to be received during a 1-y lifetime of the in-cell portion of the photometer. The loss in signal transmission at cable junctions was greater in the fiber-bundle cable than in a 1-mm-diam, silica, single-fiber cable: a loss of 6 dB across each junction in the fiber-bundle cable vs 3 dB in the single-fiber cable. Attenuation in the single-fiber cable after a dose of 106 rad was 2.5 times greater at 500 nm than that of a fiber bundle of similar length. However, the single-fiber cable was still usable at a dose greater than 107 rad. The photometer was designed to use a single-fiber optical cable with adequate radiation shielding.

A control and monitor system has been developed for a nuclear Thermal Radiation Simulator (TRS) which uses a unique fiber optic data link. The system will operate up to nine TRS arrays that are positioned at various remote locations. Each array is operated by a local microprocessor that performs control and monitor functions. Master system control and monitor functions are performed by a central minicomputer. Communications between the local microprocessors and the central minicomputer are performed via three 2200-meter fiber optic data links. Each data link will operate up to three TRS arrays. A newly developed optical coupler supports simultaneous duplex data transmission on a single fiber. The fiber data link operates at 150 kilobits per second, with the capability of operating in excess of 2 megabits per second, at a bit error rate of < 10-9. The system uses low cost step index fiber, LED transmitters and PIN diode receivers in addition to the optical couplers. The coupler boasts parameters of < 2 dB receive input loss, < 1.5 dB transmitter output loss, and transmitter-to-receiver isolation of 40 dB when operated at 820 nanometers.

A modified Voitenko compressor generated a Mach-l30 air shock in an outlet pipe open to the atmosphere. Fiber optics transmitted luminosity associated with propagation of the air shock to an external display board, which was scanned with a high-speed streaking camera. We describe the computerized microdensitometer scanning technique for converting the film records to pseudo-3D, isodensity, and density profiles. The isodensity contours can be displayed using different colors to facilitate analysis. This technique can achieve resolutions of 1 ns and 2 pm. We give examples of the pseudo-3D, isodensity, and density profile plots for the experiment. The microdensitometer output was digitized for input to data display programs run on a CDC 7600. These results were used to provide submicrosecond accuracy for shock propagation over 5 m of the outlet pipes. In addition, we obtained information about gas flow behind the shock front. Other current or possible applications for the technique are measurement of: target implosion in laser fusion, flash x-ray data in hydrodynamic and ballistic experiments, temperature profiles for high energy (>105 K) gas dynamics, and dynamic events in weapons testing.

Fiber-optic probes can be placed directly into solid explosives in order to obtain accurate measurement of the detonation velocity. In the case of two-phase fuel-air explosions, however, such measurements become difficult as the fiber optics can receive radiant energy from the reaction front well before and after the passage of the reaction front. Nevertheless, appropriate design and placement of the fiber-optic probes and discrimination of the signals makes this technique useful. Furthermore, a5 the distance between the shock and reaction fronts becomes significant in two-phase fuel-air detonations, the concomitant measurement of arrival times at co-located fiber-optic probes and piezoelectric pressure gages of the reaction and shock fronts, respectively, allows characterization of induction time/distance information as a function of the system parameters. Application of this technique to the detonation of aluminum powder in air resulted in induction times of 14 to 48 lisec. Such variation was attributed to variations in the concentration of aluminum powder in air. This compares with an induction time of about 3 psec in the case of ethylene-air homogeneous gas-phase detonations.