Sulphide and telluride fibers have been fabricated using the rod-in-tube (RIT) process. The minimum optical losses of the polymer clad and unclad fibers are 0.047 and 0.11 dB/m, respectively. However, the glass clad fibers possess minimum optical losses of 0.6 and 0.7 dB/m, respectively. The difference is attributed to interfacial scattering. The bending strengths have been measured in water, air and liquid nitrogen. While the strength in liquid nitrogen approaches 200 ksi, the results indicate that water has a detrimental effect on the strength, presumably due to a stress corrosion mechanism.

The advances in parallel optical transmitter and receiver array technologies for large computing applications are described. Parallel data lines with 16 and 32 channels, with each channel operating at 1 Gb/s and 500 Mb/s respectively, have been demonstrated.

When Cassini's Huygens probe descends through the atmosphere of Saturn's moon Titan early next century it will send back pictures and data to the researchers at the University of Arizona's Lunar and Planetary Laboratory from a very unique camera, a camera called DISR. The descent imager/spectral radiometer, as the name implies, is responsible for not only sending pictures but both radiometric and spectroscopic data from the near UV through the visible and into the near IR parts of the EM spectrum. Unlike conventional cameras, however, DISR has not one aperture but thirteen, including nine separate image channels that share a single CCD. The optical manifold carrying these images from the input lens assemblies to the CCD is a fused fiber image bundle that will allow scientists to see all nine views at once, including two views through a visible spectrometer. This paper outlines some of the engineering and manufacturing challenges in making an image conduit assembly for the application of planetary exploration.

This paper presents an overview of the near-earth, space-radiation environment, its effects on space craft that must exist in it, and means of quantifying and reducing these effects. Other aspects of the space environment are touched on for completeness and because they can impact both the consequences of radiation damage and the damage itself. Of necessity, the overview of such a large field in a small space must be cryptic. The goal is to familiarize at least a small portion of the opto-electronics community with the space and spacecraft-manufacturing environment in which they will be contributing their technology to an ever-increasing extent.

The strength degradation of lightguide fibers has been studied over a range of elevated temperatures and at room temperature. Using these data we show that accelerated testing can be used to predict ambient temperature behavior. An activation energy of approximately 90 kJ.mol^-1 describes the shift in corresponding times.

High speed strength testing of proof test level flaws in optical fiber was accomplished using a conventional belt slide and a piezoelectric load cell. Stressing rates of 10,000 kpsi/s were achieved and fractographic analysis of fracture surfaces confirms the measured strengths. Even at such high stressing rates, little evidence of the inert strength was found. However, significant curvature in the log strength versus log stressing rate data suggests the presence of region II crack velocities.

The two-point bending technique has been used to measure the strength of both polymer coated and bare fibers in liquid nitrogen after the fibers were first aged in an aggressive environment followed by a drying process. The results show that some strength recovery occurs upon drying of polymer coated samples while continuing degradation was seen when drying bare samples. The healing process observed for coated fiber is thought to be caused by condensation of the hydrated surface layer formed during aging.

It is known that silica fiber strength and fatigue are sensitive to such environmental parameters as humidity and pH. However, there is no complete understanding of the mechanisms of their action. For this reason, static fatigue measurements with pH-value being controlled were performed. The results are interpreted in terms of activation of water molecules by OH- groups.

The intrinsic strength ((sigma) _i) is defined as the strength in the absence of slow crack growth or fatigue. It is of general interest in the study of brittle fracture, but it is of particular importance in the evaluation of lightguide fiber lifetimes since it is required for the calculation of the constant B. In this work we review the existing literature relating to the inert strength, indicate the limits that can be proposed for and suggest possible approaches to more satisfactory estimates of value(s) of (sigma) _i. It is suggested that reasonable values of the inert strength may be obtained by taking 85 - 90% of the liquid nitrogen strength.

Stress free corrosion such as chemical dissolution of silica optical fibers is normally assumed to be a pure pH dependent reaction. In our investigation we have found that it is not only the pH values that influence the lifetime of the fiber in water, but also the ionic strength of the water in contact with the fiber. We have seen that the lifetime of the normal dual coated fibers is severely reduced in seawater compared to the lifetime in deionized water. Carbon coated fibers show better results in these harsh conditions; but the experiments also demonstrate that the carbon coated fibers begin to fail before they have had a sufficient lifetime. A chemical explanation of the results, based on dissolution of glass in water and influence from the ions in question, is given. In this paper, experimental results from long term static fatigue tests on fibers in different liquid environments is shown. In the laboratory we have samples still living after almost four years in different environments. We have buffered water at pH values from 3 to 11, artificial seawater and deionized water. The fibers in the tests are both commercially available dual coated and carbon coated fibers and carbon coated test fibers.

In this report, we present an experimental analysis of the mechanical behavior of fused silica standard telecommunication fibers aged in hot air and hot filling compound. Our measurements at standard room temperature conditions after the aging treatments indicated tensile strength increases of up to 5% at 85 degrees Celsius and 15% in filling compound after one- to six-month aging. The dynamic fatigue for the fibers aged in the filling compound also improved (n-values from 17 - 20 to 25 - 30) in parallel with the fiber strength while the fiber static fatigue tests gave large n-value increases from 30 to 140. In order to examine the effects of the aging treatments on the fiber coatings, we used dynamic mechanical analysis to measure the coating mechanical properties, storage modulus E' and loss tangent tan (delta) . In general, we have found that aging in hot air and in the filling compound results in a significant decrease in E' and increase in tan (delta) , thereby suggesting an aging-related increase in the capacity of the coating to absorb substantial amounts of mechanical energy. A qualitative theoretical analysis of the coating contribution to the fiber crack growth and mechanical behavior in conjunction with our experimental results suggests that the coatings' ability to absorb more mechanical energy during aging contributes to increased fiber strength and improved fatigue behavior. Thus, our results to date provide the first experimental evidence that a fiber coating can stabilize cracks on fused silica surfaces and contribute in a significant way to fiber mechanical behavior.

Optical glass fibers can exhibit a transition in slope of their static fatigue behavior ('knee' phenomenon). This effect was previously supposed to reduce fiber lifetime. The 'knee' phenomenon as well as the phenomenon of abrupt increase of the flaw size ('pop-in') are re- examined in this paper. It is shown that under normal proof-test conditions these two effects have no tangible impact on the fiber service life estimations.

The principle factors affecting arc fusion splice strength are discussed, which collectively lead to splices having greatly improved strengths.

Two formulations based on perfluorinated polymer were prepared for use as UV-curable optical cladding for silica fibers. In the first formulation an adhesion promoting agent based on fluoroacrylate resin was synthesized and mixed with the experimental product Defensa 7702⁺+ in order to promote wetting and chemical adhesion to the silica fibers. In the second formulation, wetting and physical adhesion between the liquid coating and the silica fibers were achieved by increasing the viscosity of the starting coating by addition of unsaturated perfluorinated polymer into Defensa. Both formulations were used as primary coatings on dual coated silica optical fibers. The mechanical behavior of the formulations was characterized by the strip test, the pull-out test and zero stress aging in 90 degrees Celsius pH 7 buffer. The results show that both formulations exhibit better wetting-adhesion characteristics than unmodified starting coating and that the strength degradation during zero- stress aging was lower for the fiber coated with the formulation of higher viscosity.

Hermetic aluminum-coated fused silica fibers can withstand high stress levels without failure for prolonged periods of time in water-containing environments. Aluminum-coated fibers from several sources exhibit differences in strength. The aluminum and silica surfaces have been examined using SEM and AFM in order to understand this variation. Differences in the interfacial interaction between aluminum and glass and in the microstructure of the coatings were considered, but were not unequivocally identified as being responsible for the differences in strength observed for the various aluminum-coated specimens.

Vickers indentation has been used to introduce controlled flaws in fused silica optical fiber in order to model the behavior of 'weak' defects encountered in practice. Novel techniques are used in order to conveniently examine indentations over a broad range of residual strength; these include the use of flat fiber which facilitates specimen alignment during indentation and subsequent strength measurement in bending. The strength of indented silica fiber measured in pH 7 buffer reveals a bimodal behavior at the threshold for radial crack formation which is related to the 'pop-in' of radial cracks after indentation or during strength testing. An unusually low value of the stress corrosion parameter for subthreshold indentations of n approximately equals 11 is observed in pH 7 buffer. This suggests that under some conditions the usual assumption of n approximately equals 20 may lead to an overestimation of fiber reliability.

With the increasing number of optical networks comes a growing demand for hardware to allow management of interconnections. One of the important elements in a network is the cross-point switch. In this presentation, we describe a GaAs 3 multiplied by 3 optoelectronic switch based on a monolithic optoelectronic integrated circuit which combines a receiver array of MSM photodetectors and three transimpedance amplifiers providing gain for the three output channels. The 3 multiplied by 3 matrix of photodetectors acts at the switching element. The three electrical output channels from this receiver are amplified further by MIC circuits using chip amplifiers. This restores the signal to a level sufficient to drive semiconductor lasers thereby converting the electrical signal back to an optical signal for use as an optical- optical router. A critical step in the switch construction is the delivery of the optical signals to the photodetectors. A special mount was designed and fabricated to support and align the 9 fibers in front of their respective detectors. The switch was evaluated in terms of the responsivity, the isolation and the cross-talk. The overall responsivity exceeds 20 A/W with a bandwidth of 400 MHz, limited by the speed of the detectors. The isolation varies between 33 and 55 dB and depends on the device selected and on the bias condition of the detector in the off-state. The operation of the switch was demonstrated using three television signals.

An optically powered fireset has been developed for the Procyon high explosive pulsed-power generator at Los Alamos National Laboratory. The fireset was located inside the generator where large magnetic fields are compressed to create amplified current pulses. No energy sources were allowed inside the experiment and no wire connections can penetrate through the wall of the experiment because of the high magnetic fields. The compression was achieved with high explosives in the experiment. The fireset was used to remotely charge a 1.2 (mu) F capacitor to 6500 V. The capacitor was charged by using two 7 W fiber coupled GaAlAs laser diodes to illuminate two fiber coupled 12 V solar cells. The solar cell outputs were connected in parallel to the input of a dc-dc converter. The voltmeter, powered by illuminating a third 12 V solar cell with 1 W laser diode, was used to monitor the charge on the capacitor. The voltage was measured with a divider circuit, then converted to frequency in a V-F converter and transmitted to the control room over a fiber optic link. A fiducial circuit measured the capacitor firing current and provided an optical output timing pulse.

This paper describes the development of a prototype onboard baseband switch for use in advanced satcom systems. The modular switch is designed to accommodate different types of satcom services and/or carriers. The selected architecture utilizes a high-speed fiber optic ring for the I/O interconnections of the satcom channels handling both circuit- and packet-type traffic. Whereas, an optical star topology is used for onboard clock distribution. The onboard baseband switch design makes maximum use of photonics, VLSI, and standard cell/gate array technologies to implement the hardware/firmware required for a power-efficient, light-weight, reliable payload with a flexible switch architecture. Relevant optical technologies, active and passive components, and systems considerations to ensure a high reliability operation are discussed. To assess its viability in potential commercial applications, the state-of-the-art of photonics technology and future prospects for economical large capacity multi-channel services are briefly reviewed.

The 'apparent' microbend sensitivity of 62.5/125 micrometer graded index multimode fiber was examined as a function of both cure temperature and oxygen concentration present during cure for three UV curable acrylate coatings. The 'basketweave' test was used to quantify the microbending loss. Two coating materials cured under elevated temperature conditions exhibited increased microbending loss response at ambient test temperatures. One of the two coatings cured as a function of decreasing oxygen concentration exhibited increased loss at both ambient and low test temperatures. The microbending loss for both experiments was time dependent. Potential mechanisms responsible for the loss behavior observed in both experiments were proposed and supported with strip force and fiber friction force data.

Two types of hybrid gels based on silica and perfluorinated polymers have been prepared. The first type involves a perfluorinated polymer containing acrylate groups. Perfluoropolyether diol diacrylate (PFDA) was functionalized by reacting it with (3-mercapto-propyl) trimethoxysilane by a Michael addition. The resulting silyl derivative (PFDAS) was able to copolymerize with a silica precursor, tetraethylorthosilicate (TEOS), resulting in perfluorinated polymer/silica hybrid gels. For the second type, perfluoroalkylsilane (FAS), vinyltriethoxysilane (VTES), and TEOS were polymerized in one step. In both cases, the gels were transparent, crack-free and water repellent. Since the inorganic and organic components are covalently bonded to each other, these materials can be classified as organic/inorganic copolymers.

Discrete reflections are produced by physical discontinuities at connectors, mechanical splices, or at fiber-to-component connection points in fiber-optic systems. Even a small amount of reflected light arriving at the source laser can affect its modulation performance and increase the relative intensity noise. Consequently, the link signal-to-noise ratio deteriorates, causing a power penalty in both analog and digital systems. Multiple reflections aggravate the situation. The accepted solution is to restrict the component reflectances to below a certain maximum. This paper reports our findings on the accuracy of optical continuous wave reflectometry (OCWR) and optical time domain reflectometry (OTDR) techniques down to minus 70 dB reflectance. If the reflected power is estimated by integrating under the reflection peak, the OTDR is more accurate at low reflectances; it enables measurements down to minus 62 dB with an accuracy of plus or minus 1.0 dB or down to minus 65 dB with an accuracy of plus or minus 2.0 dB. The sensitivity of the measurements to the pulsewidth and to the characteristics of the optical lead-in fiber were also evaluated.

Some recent service-affecting field failures in cold weather raised concerns about the low- temperature performance of loose tube fiber optic cables. These failures occurred predominantly in aerial transmission lines operated at 1550 nm. Field OTDR (optical time domain reflectometry) analyses and laboratory measurements established that the increased attenuation at low temperature resulted from fiber microbending caused primarily by the thermal contraction of buffer tubes. Cable structure tightness based on a model of mechanical coupling between cable elements and excess fiber length-to-buffer tube inner diameter ratio emerged to be two key parameters to control the magnitude of this temperature-induced cable loss (TIC). Based on our analyses, we developed a clamping device for re-termination of affected cables in the telecommunications network.

In a single mode optical fiber two series of dispersive effects are observed: the chromatic dispersion and the polarization mode dispersion (PMD). The polarization mode dispersion generates a limitation in high speed digital transmission and also in high quality analog systems. The polarization mode dispersion is induced in an optical fiber principally by core birefringence and index core axis variations. The stresses along the fiber depend on fiber packaging and manufacture, they induce random index variations in the fiber. So in CNET we have analyzed the PMD on different fibers. After a comparison of measurement methods we have tested the fibers under different environments and packaging. The results obtained are analyzed. Using a new axial strength set up able to receive long lengths of fibers we have tested the PMD dependance of the fiber concerning bending, microbending, axial strength and coating effects. Some concatenation measurements have also been made. Complementary measurements are still under study. In conclusion the results of our investigations concerning PMD are given and analyzed. Using those results we have defined the maximum PMD value for the detail specification for our G652 single mode optical fiber required in France Telecom Network.

In this paper we present the results of the development of single mode 1 by 2 and 1 by 3 broadband 1550 nm optical fiber splitters with miniature package length of 25 mm for fiber optic gyroscope applications. Also presented are the reliability test results for the optical splitters.

This paper provides an overview of fiber optic system reliability in adverse environments. Systematic analysis of fiber optic components leads to a low risk test approach to system level testing. Complete system testing provides pass/fail criteria for immediate introduction of an operational system into a given adverse environment.

We have studied the effects of radiation on the performance characteristics of laser diodes. The laser diodes were exposed to radiation of continuous electron beams at the Lehigh University Van de Graaff Radiation Facility.

We have studied the effects of radiation on the performance characteristics of optical fibers. These fibers were exposed to radiation of a continuous electron beam of the Lehigh University Radiation Facility. Results of light transmission as a function of radiation dose for various fiber configurations, as well as anneal results, are presented.

We have studied the effects of radiation on the performance characteristics of CCD devices. The CCDs were exposed to radiation of the continuous electron beam of the Lehigh University Van de Graaff Radiation Facility.

We have measured the effects of radiation on various electro-optical devices used as communication components. The measurements were performed with 2.5 MeV electrons from the Lehigh University Van de Graaff. The performance of the devices was monitored both during irradiation and after irradiation. We report here the results of irradiation on various electro-optical devices used for optical communications. These devices include simple waveguide couplers, optical waveguide switching devices, transistors, and total amplifier systems. The 3 MeV High Voltage KN3000 Van de Graaff at Lehigh University was used for the irradiations. The machine provided beams of electrons which could be directly used or gamma rays from the electron beam bremsstrahlung. We looked for slowly changing time effects using a continuous beam as well as transient effects with a pulsed beam arrangement. We now review the results obtained with various electro-optical components.

Several fiber optic systems have been designed and implemented for the high energy density experiments at Pegasus II. The main fiber optic system developed for Pegasus II remotely controls both the charging and discharging of the capacitor discharge unit (CDU). This fiber optic system is also used to distribute the timing and firing information specific to each experiment to the operators and experimenters. The timing and firing information includes the voltage on the CDU as it is being charged, a confirmation signal indicating the CDU has discharged and common timing signals based on the output signals on the load ring of the CDU. Various fiber optic systems were implemented to transfer diagnostic information related to the discharge of the main capacitor bank to the control room. The diagnostics include the current, electric field, and vacuum pressure at the target area. Not only do these fiber optic systems provide the control and monitor signals for the experiments at Pegasus II, they have the added value of preventing premature firing of the capacitor bank, eliminating ground loops between the test area and the control room and providing overall increased operator safety.