This paper overviews genera types of polymeric coating systems which have been used on glass optical fibers. Performance requirements responsible for the utilization of these different coatings systems are discussed.

The long-term performance of optical fibers strongly depends on the mechanical properties of fiber coatings. A dynamic mechanical analysis technique, commonly used for polymeric materials, was adapted to optical fibers for direct measurements of storage modules (E')/loss tangent (tan (delta) ) - temperature profiles of coatings. This technique involved testing a parallel array of optical fibers in single cantilever bending. The measured fiber modulus profiles showed only a 50% drop through a glass transition region that was centered at about 30 degree(s)C, intermediate between the coating transitions measured on free films in tension. The fiber modulus profiles calculated from individual coating profiles are in agreement with the measured profiles. The dynamic mechanical analysis technique demonstrated in this report allows one to measure coating properties directly on fibers for failure analysis and investigations of aging effects.

The attenuation of signal in dual coated optical fibers is sensitive to a number of parameters related to glass design (mode field diameter, cutoff wavelength, etc.), to environment (temperature, stresses), to cable design and fabrication (loose tube, ribbon, crossovers, point stresses, etc.), and to coating properties. The coating properties, principally the temperature dependent modulus of the primary (buffer) coating, and geometry are shown to determine the sensitivity of the attenuation to many of these variables.

Large optical losses in singlemode fibers have been reported in loose tube fiber optic cables exposed to extremely low temperatures (-20 degree(s)C to -40 degree(s)C). These losses have occurred predominantly at 1550 nm (although some transmission systems at 1310 nm have also been affected) in aerial cables and were confined to the cable section adjacent to a splice closure. Optical transmission measurements on commercial fiber optic cables that were subjected to temperature cycling in an environmental chamber indicated that thermal contraction of buffer tubes at low temperature was the major contributor to fiber bending-induced loss. While the buffer tube thermal shrinkage occurs, optical fibers contained in the tube undergo nearly zero contraction. Consequently, the fibers buckle against the buffer tube inner wall, causing bending-induced losses. Cables with an initially low fiber excess length-to-buffer tube inner diameter ratio, and strong buffer tube-to-central member coupling exhibit minimal loss. It has been demonstrated in the laboratory that the low-temperature optical loss can be suppressed by effective coupling of the cable sheath to the central member.

A method to measure the permeability to moisture of fiber optic coatings is presented along with the results of such tests. The resistance of optical fibers to fatigue and strength degradation with high temperature and humidity is shown to be strongly dependent of the permeability of the secondary coating in a dual coating system.

The most critical variable effecting the strength of silica lightguides is the availability of water to the fiber surface. At very low temperatures (T < 77 °K) and at high vacuum (PH2O < i07 torr) the thermodynamic activity of water is so low that mechanical failure of the fiber occurs by the direct breaking of Si-O-Si bonds. In this case very high strength (- 12-14 GPa) and very slight time dependence (formula available in paper) are expected. Also an activation energy comparable to the SiO bond energy is observed (- 100 kcals/mol). On the other hand, under normal conditions (T - 0- 100°C and normal relative humidity), the strength and time dependence are controlled by the combination of stress and the reactivity of water with the fiber surface: SiO2 + H2O = SiOH HOSi. In this case the time dependence of strength is very much greater (n 20) and the activation energy is approximately 30 kcaI/mol.2 Because of this rather extreme time dependence, the short time tensile strength (say tf = 10 sees) is only about 5.5 GPa and will be reduced again by a factor of 2 (to = 2.8 GPa) in about one week. A subject which continues to be discussed and studied is the proper analytical description of this time dependence. In this regard, Bubel and Matthewson3 have studied the behavior of several proposed models for time dependence. They find that the differences in predicted lifetimes from the models differs significantly. In particular they suggest that the universal use of the optimistic power law is not appropriate.

Models exist to describe the mechanical lifetime of an optical fiber. All models, also those that include zero stress aging, make use of a power law to describe stress corrosion. This law is a good approximation because the stress and speed of the crack tip are comparable for fatigue tests (high strength mode) and service life (weak flaws). For high strength (pristine) fibers the description with finite crack size needs, however, further examination. Since one bond rupture has a large effect on the strength of such a fiber, the continuum model of fused silica must also be compared with discrete modeling. In this paper an analysis with discrete bond ruptures is performed. The theory is used to fit measured static fatigue data from high strength fibers. It is concluded that discrete modeling results in almost the same effective corrosion susceptibility n as for the continuum model. Furthermore the effective Weibull parameter m of 75, following from an initial pristine surface, is physically interpreted and corresponds well with measurements.

The role of three different adhesion promoters in the primary coatings of optical fibers on the resistance of fibers to aging in water has been investigated. The use of an acid phosphate ester as adhesion promoter gave fibers higher strength and n-value prior to aging when compared to standard silane adhesion promoters and copolymerizable silane coupling agents. After 6 months of zero stress aging in water of 60 degree(s)C, no change in strength was found for all fibers except for 1 fiber. The high n-value of fibers with the phosphate ester adhesion promoter gave fibers improved resistance (or longer time to failure) to high stresses in the static fatigue test in water of 85 degree(s)C. Tn this test, the time to failure for low applied stresses, where zero stress aging determines lifetime, was not depending on the type of adhesion promoter. other aspects of the coating as the level of adhesion to the glass, the chemical composition and the mechanical characteristics are playing a role as well in the resistance of fibers to stress free aging and static fatigue in water.

The factors limiting the maximum strength of carbon coated fibers are considered. In spite of the variations in the inert strength, at room temperature the strength of fibers under investigation depends not on the drawing conditions, but on the properties of the carbon coating. The strength of weak carbon coated fibers with melted-in zirconia particles is also investigated. It grows with increasing carbon thickness (i.e. decreasing of fiber electrical resistance). When the carbon coating is thick enough (electrical resistance is less than 10 kOhm/cm), the fiber strength practically does not depend on the coating thickness and environment humidity and is more than two times higher than that of polymer coated fibers.

In this paper we report on the effect of hydroxyl (OH) groups on the photoluminescence in the near IR (1.5 and 1.3 micrometers ) in rare earth (Er, Pr)-doped glasses. The 1.5 micrometers emission of Er-doped phosphate glasses was studied, before and after a special heat treatment. The luminescent lifetime of the 1.5 micrometers emission increases substantially, typically from 3 ms up to 7.2 ms for a 2 mole% Er₂O₃-doped phosphate glass, due to the controlled heat treatment. The increase in lifetime is ascribed to a decrease in OH- concentration, which is confirmed by IR-absorption spectroscopy. The quenching by OH is described by a simplified quenching model, which predicts the 1.5 micrometers emission lifetime as a function of Er- concentration with the OH-concentration as parameter. It appears that the larger part of the OH groups is coupled to Er ions and thus acts as quenching center. Photoluminescence quenching by OH groups is also reported for the 1.3 micrometers emission of Pr in GeS₂-glasses: In pure OH-free GeS₂ glass the 1.3 micrometers emission lifetime is as high as 350 microsecond(s) , for a 400 ppm dopant level. In GeS₂ glasses containing only small amounts of OH (approximately 100 ppm), this lifetime is less than 200 microsecond(s) . Both examples demonstrate that for the fabrication of efficient glass optical amplifiers at the telecommunication windows 1.3 and 1.5 micrometers , the OH-impurity level of the host glass must be kept as low as possible.

We have fabricated stable chalcogenide glasses containing up to 35 at. % tellurium and these glasses do not exhibit crystallization upon reheating up to the fiber draw temperature. The physical properties such as Tg, packing density, and Vickers Hardness decreases while the mass density and CTE increase with Te content and these are attributed to the weaker delocalized metallic-bonding character introduced with Te. We have drawn unclad fibers with a minimum attenuation of 0.11 dB/m at 6.6 micrometers which represents the lowest loss reported for a chalcogenide glass containing high levels of Te. Preliminary core/clad fibers have been drawn with a minimum loss of 0.7 dB/m at 6.6 micrometers . Improvements in glass quality and processing will lead to lower losses. We also present data demonstrating the use of unclad fibers for evanescent sensing of numerous organic and inorganic liquids and their mixtures in the 3-12 micrometers region.

We have designed an input coupler to couple light into the core of a single mode optical fibers without severing the fiber. This design uses two coupling steps. The light is first diffracted into a planar waveguide constructed on the surface of the fiber using diffraction gratings. The light in the planar waveguide is then coupled to the core of the optical fiber through directional mode coupling.

Nature of excess optical loss in fibers with high (up to 35 mol.%) GeO₂ content silica core was studied experimentally. The absorption and scattering loss dependences on the drawing conditions were studied as well as the behavior of germanium-related oxygen- deficient centers (GODC) absorbing in UV spectral region. The peculiarity of such fibers was found to be in the drastic increase of the absorption and scattering loss when the core diameter diminish up to 3-3.5 micrometers . According to the excess loss analysis the absorption loss is caused by the enhanced GODC formation and the Ge-related drawing-induced defects. The excess scattering loss which dominates is assumed to be due to azimuthal and longitudinal core inhomogeneities caused by hydrodynamical instabilities of viscous glass during the fiber drawing. The germanium diffusion effect on optical loss is discussed.

Advances in electro-optical (EO) polymer device development continue to take place at a rapid rate. Presented here is an overview of this progress with a focus on device fabrication and processing, including poling, optical cladding, temperature stability, and electrical properties. The impact of material types and device applications upon the design and fabrication requirements will be addressed. Future directions and requirements will also be discussed.

Samples of PMMA (Poly-(Methyl-Meth-Acrylate)) in combination with various substrates have been modified by ionizing radiation in order generate regions of increased refractive index. These waveguiding structures were used to build passive devices such as Y-branches, couplers and Mach-Zehnder-interferometers. The refractive index and beam profil and the attenuation at different wavelengths of the generated waveguides were measured.

Ti:LiNbO₃ optical switches, directional couplers and modulators are of interest in areas such as optical communications, sensing, and signal processing. It is important that their operation should be stable and reliable over a wide range of temperatures. It has been suggested that temperature changes of -25 degree(s)C did not produce any appreciable changes in symmetric directional couplers response. We have investigated the temperature effects on commercially available Z-cut Ti:LiNbO₃ directional couplers/switches. Measurements over temperature range between 19 degree(s)C-27%DGRC showed that temperature affected the transfer characteristics (TC) by shifting them toward lower biasing voltage. The average shift in bias voltage was measured to be about 3 V/ degree(s)C. However, no appreciable changes in switching voltage, crosstalk or coupling ratio were observed. This sensitivity to temperature changes is believed to be due to thermo-optic effect and therefore enhanced by the asymmetry of the waveguides.

Recently, concerns have been raised about the performance of mechanical fiberoptic splices in high humidity environments. These have arisen due to the introduction of lower-cost, free-breathing splice enclosures, which, since they are not sealed, allow the entry of moisture, and potentially allow condensation on the splices. In order to determine whether or not high humidity is a reliability issue, we conducted two series of laboratory tests with a variety of different splices, including both fusion splices and mechanical splices. In addition, we made visual observations of the effect of a high humidity environment on simulated splices, which were assembled using gel-filled glass capillary tubes. Our laboratory tests exposed the splices for prolonged periods to a high-temperature, high-humidity environment of 75 degree(s)C/95% relative humidity (RH), with periodic excursions down to 25 degree(s)C/95% RH, and to -25 degree(s)C with uncontrolled humidity. We found some splice failures that could be correlated to the onset of high humidity, and we conclude that some types of mechanical splices potentially could fail in such an environment. In this paper we will describe our experimental setup and data collection process, and present the results of the experiments.

UV (ultra-violet)-curable adhesives were identified as the underlying cause for failure of devices subjected to accelerated aging conditions. These adhesives must be resistant to degradation and dimensional/mechanical instabilities such as creep. We examined two UV-curable adhesives and found that thermal post-curing caused some shrinkage and degradation. However, post-curing also raised the adhesive glass transition temperature, thereby reducing the reliability risk associated with mechanical instability. We investigated the dimensional/mechanical stability of UV adhesives by measuring thermal expansion/contraction and creep compliance. We found that the adhesive thermal expansion and creep compliance are large enough to pose device reliability risk. Raising the glass transition temperature of UV-curable adhesives by thermal post-cure can improve optical device reliability by lowering the creep compliance.

This paper presents both the theoretical and experimental results of the performance characterization in the emerging technology of stub fiber connectors. A stub fiber connector, consisting of two closely spaced joints, shows negligible modal noise. However, modal interference at such a connector joint results in a wavelength dependent oscillations in insertion loss. It is shown that this phenomenon is strongly affected by the cutoff wavelength of the stub fiber and the losses at both joints. Amplitude of the loss oscillations depends on each joint loss and on the polarization angle between the two interfering beams. A measurement method is also presented to characterize the insertion loss of such connectors.

A key component to be used in PON systems is the power splitter. There is little information available on the reliability and lifetime of this component either under realistic field conditions or from accelerated stress testing. In the RACE^a project FIRST (Fibre to the Residential Subscriber Terminal) a selection of accelerated lifetests have been performed on a small number of currently-available splitters, in order to make a preliminary evaluation of the suitability of such devices and the technologies they utilize. Outlined briefly are the main technologies used in the manufacture of optical splitters: fused-fiber, deposited silica planar waveguides, and ion-exchange planar glass waveguides. Samples from one manufacturer of each of the three technologies have been purchased for testing. An understanding of the component construction and materials allowed the relevant ageing tests to be chosen. The optical measurements, the reliability test procedures and the equipment used are described. A review of the initial results shows the key points of interest for each technology. The preliminary results of the accelerated testing are that none of the splitter designs tested here has shown an adequate reliability to meet a target specification.

The modelling of optical fiber reliability has been extensively discussed, but there is little understanding of how the fatigue of deployed fiber due to stress corrosion and environmental corrosion contributes to the reliability of a telecommunications network. There are a number of models that can be used to calculate or predict the lifetime of optical fibers for both pristine conditions and conditions where zero stress ageing occurs (water immersion, high temperature, high humidity and the presence of chemicals). The failure rates for fiber can be combined with the failure rates for the other network components to give a figure for the network reliability which will indicate whether the network will be able to meet its Quality of Service (QoS) targets. A method for calculating fiber failure rates will be presented and the results for various environments will be compared with previous assumptions and with the failure rate due to cable dig-up. The increasing demand for tight bending of fiber in customer premises will be mentioned and its effect on network reliability discussed.

The first experimental optical fiber network (fiber to the home CATV and video-phone) was installed in BIARRITZ (France) at the beginning or 1980. Some parts of the first optical links have now been removed. FRANCE TELECOM decided to stop field trial services, it appeared interesting to evaluate and expertise fiber reliability after more than 10 years of aging in a real adverse field environment. In this paper we give a short description of the layed down links, and indicate how we have carefully removed the individual fibers from the cables. After a first measurement of the mechanical parameters using normalized dynamic and static tests, we compared the results obtained with those of the equivalent tests used to evaluate these fibers before their installation on the field. The tests used are the same than those used in the 80 th. In conclusion, the paper gives the ageing results measured on the BIARRITZ optical fibers after more than 10 years of service in real environment and evaluate it by comparison with the results before installation.

Fused silica optical fiber tested in aggressive environments can exhibit a 'knee' in both the zero-stress aging and the fatigue under stress; degradation proceeds at an accelerated rate beyond the knee. This behavior leads to shorter lifetimes than predicted from short term data and to strength degradation even in the absence of an applied stress which can result in handleability problems. While the first observation of this behavior was for a humid environment, later work only reported the knee in liquid aqueous environments. This paper reports the observation of a pronounced fatigue and aging knee for a fiber tested in 85 degree(s)C, 85% relative humidity, clearly indicting this phenomenon can occur in more benign environments. Surface roughness measurements using atomic force microscopy also show an abrupt increase in roughness indicting that, for this fiber at least, the development of surface roughness before the knee can not be used as a precursor for predicting the position of the knee.

The reliability of long lengths of fibers in optical cables is determined by the presence of weak spots which are infrequently produced by normal fiber production methods. Particles from the atmosphere may cause weak spots on the fiber surface during the drawing process. Abrasive damage of the fiber surface may occur when physically contacting the drawing equipment. Finally, interior weakening of the fiber may occur during preform manufacture because of voids and particles, embedded inside the preform. Four representative types of such flaws have been studied with respect to their mechanical fatigue in normal atmosphere, 23 degree(s)C, and 50% relative humidity. The results are summarized in this paper. Fatigue of zirconia induced weak spots was observed in rapid tests, being significantly less or absent, at lower stress rates. No fatigue was observed in fiber with particles of chromium oxide deeply embedded in the glass. The effect of the size of particles was also studied, by comparing tensile test results with a theoretical strength distribution, based on an assumed relation between particle size and fiber strength. The size of particles appeared to have no significant influence on the atmospheric fatigue of fiber. A significant time-dependence of strength was found in weak spots caused by physical contact with glass during drawing. The static fatigue is apparently the same as for flaw-free fiber. No fatigue was found of weak spots originating from abrasive contact with metal, in the coating die.

Several different optical fibers have been aged in 21, 60 and 85 degree(s)C water under essentially zero stress conditions. Included are fibers with both synthetic and natural quartz glass surfaces and also different coating materials. During aging samples have been taken out and both two-point bending and tensile strength tests have been made. Results indicate that there is no clear difference between synthetic and natural glass strength after aging. On the other hand the coating material has a significant effect on the strength of similarly prepared glass fibers.

Dynamic breaking strength measurements have been carried out on hermetically coated fibers taken out of a cable, after the cable was stored in water at 70 degree(s)C for 4 months. The cable was a slotted core construction, not including any metallic water barrier. More than 200 specimens with a gauge length of 9.5 m have been tested, so that the effective length of fiber tested is in excess of 2 km. The reference for this test was measurements on a similar population on as-received fiber. Tensile strength measurements have also been performed on non cabled fibers stored in water at 70 degree(s)C. Here, fiber specimens have been tested periodically within a period of 6 months. The experiments reported show that the hermetically coated fiber will maintain its good mechanical properties. Pit formation and strength reduction due to stress free ageing, as reported for standard coated fibers, have not been observed for cabled hermetically coated fibers after being aged 4 months in water at 70 degree(s)C nor bare fibers stored 6 months in water at the same temperature. The hermetic coating thus protects the silica glass surface against the environment, and no corrosive chemical interaction between coating and glass surface occur.

The strength of flaw-free silica fibers in the absence of water is of the order of 12-14 GPa and is essentially independent of time. (Formula available in paper). On the other hand, in the presence of water, the time dependence is very much more serious (n - 20) and even at relatively short testing times (tf 10 secs), the measured strength is <6 GPa. The development of a completely satisfactory hermetic coating which will allow the realization of the above 'water-free' strengths is not simple, however, while the advantages of a polymer coating in mechanically protecting the fiber and at the same time isolating it from microbending losses is well-known, no water-impermeable viscoelast.ic coating has yet been proposed. Two other types of coatings have been proposed and each is successful to some extent as an hermetic coating. These materials and their behavior are quite different and will be described below.

Spectral temperature measurements were made of the DIAMOND FORTUNE event at the Nevada Test Site. A large core fiber was used to gather light from the fireball produced in a large diameter cavity. To correct these spectral data for radiation effects on the fiber, a Fiber Monitor consisting of another fiber optic cable identical to that used to gather fireball light (but made blind to it) was used to measure changes in the fiber optic spectral transmission during the event. The data on the Fiber Monitor show a narrow induced-light pulse, followed by a long (approximately equals 1.5 ms) decay fluorescence signal. Following these induced signals a reduction in the preshot transmitted signals, caused by fiber darkening, was measured. DIAMOND FORTUNE event data will be presented and compared with data obtained from the Sandia National Laboratories (SNL) Hermes III gamma simulator and the SNL SPR III pulsed neutron facility. The radiation-induced fiber darkening thus determined will be presented.

The effects of ionizing radiation on fiber optical materials and components can be quite dramatic and can adversely affect their transmission and loss in the optical and infrared. The effects of both weakly (gammas) and strongly (low energy protons) ionizing radiation exposure on the optical, infrared and dielectric properties of fully dense silica (quartz) and porous, alkoxide based sol-gel silica (aerogels) have been measured using transmission from the ultraviolet through the infrared (200-900 nm and 1.8-25 micrometers ), and complex dielectric properties from 45 MHz to 20 GHz. Aerogels are both disordered and complex and contain structural features (connected pore structure) whose size varies from a few angstroms to several microns. Both their structure and topology (large surface area) as well as intrinsic impurities (cation, hydroxyl and inhomogeneities) affect their optical, IR and dielectric properties. No change in UV, optical, IR or dielectric properties was observed for the porous sol- gel (aerogel) materials with radiation dose (up to 20 MRad gammas and 3 MRad 2 MeV protons). However, formation of color center absorbing defects in fully dense quartz was observed in the UV under small (0.25 MRad) gamma irradiation. It is postulated that sufficient OH radical impurity concentration mask or prevent significant color center formation in the aerogel materials. Also, the effects of moisture on the infrared and dielectric properties has been quantified. These results are contrasted with thermal annealing experiments.

The effects of radiation on fused biconical taper wavelength division multiplexers are presented. The polarization sensitivity of these devices before and after irradiation is discussed. Preliminary results on the effects of irradiating different regions of the device, and comparisons between the effects of proton and Co⁶⁰ radiation sources are also given. A theoretical model that takes into account the index change in the Ge-doped cores of the optical fibers used to make these devices agrees well with experimental observations. This indicates that index changes in the fiber may be primarily responsible for the effects of radiation on these devices.

AlGaAs light emitting diodes were irradiated in a mixed neutron/gamma environment produced by a research reactor operating at steady state power levels. Changes in the DUTs power and spectral output were measured following an annealing period of 24-30 hours. The LED's total output power decreased with increasing fluence, and the device's spectral output/full width half maximum peaks shifted. Initially, the LED radiated light at two output peak wavelengths of 820 and 890 nm. Following a cumulative irradiation of approximately equals 10¹⁶ n/cm² (GaAs), the second radiation peak was reduced to less than 0.5% of the DUT's total output power, and the lower peak shifted to a longer wavelength of 833 nm.

Optical fiber sensors are finding wider use in all types of applications involving adverse environments, including exposure to radiation. In order to effectively characterize and evaluate the performance of a fiber sensor system for a radiation environment, such as within a nuclear power plant or in a radioactive waste storage/disposal facility, it is beneficial to develop standard test procedures. Science & Engineering Associates (SEA) has developed two such procedures for the American Society for Testing and Materials (ASTM) which address the testing of optical fibers for remote Raman spectroscopic and broadband sensor applications in a steady state radiation environment.

Optical fibers are currently under consideration for use in spacecraft systems as an essential component of rotation sensors and fiber optic gyroscopes. Many of these spacecraft systems will encounter substantial radiation doses over the mission life. These applications require the use of single-mode polarization-maintaining fiber. Prior to use in space, the radiation response of these fibers must be known. This paper investigates the radiation sensitivity of a type of PM fiber, based on elliptical wave guide principles rather than stress- induced birefringence, up to a total dose of 225 krad. The results indicate that applications utilizing the new fibers will survive the long term radiation environment in space.

Efficient low loss components that are compatible with optical fibers are essential for the successful implementation of many single mode fiber optic sensor systems. In this paper we investigate the use of Langmuir-Blodgett (LB) films as waveguiding overlays evanescently coupled to side polished optical fibers which result in useful in-line wavelength selective elements. We demonstrate the use of two LB film- forming materials: firstly a simple fatty acid is used for a passive channel dropping device and secondly it is shown that hundreds of layers of a more complex electro-optic molecule may be successfully deposited onto fibers prepared using an alternative polishing technique, which does not require extensive surface preparation.

Simultaneous coupling of the beam from one laser source into many optical fibers or fiber bundles is of interest for many applications. We developed a coupling scheme based on lens arrays to reduce transmission losses. The laser beam is splitted into focused partial beams. Positioning of an optical fiber near each focus allows multiple fiber coupling with similar efficiency as obtained for a single fiber. A prototype designed for coupling of excimer laser radiation into fiber bundles is presented.

This paper first shows the basic idea about the mass production technology of AlGaAs laser diodes using Molecular Beam Epitaxy (MBE) technique. 'GaAs passivation technique' is the key to realize the stable mass production of self-aligned structure laser diodes. This paper, then, describes the designing concept and performance of a novel laser diode for short-haul optical data communications which we have recently developed. It has a high relaxation oscillation frequency, around 3 GHz, which is favorable to transmit data at a rate of 600 to 1200 Mbps. The lifetime (MTTF) is above 100,000 hours under 3 mW cw operation at 60 degree(s)C.

Optoelectronic component costs are often dominated by the costs of attaching fiber optic pigtails-especially for the case of single transverse mode devices. We present early results of our program in low-cost packaging. We are employing machine vision controlled automated positioning and silicon microbench technology to reduce the costs of optoelectronic components. Our machine vision approach to automated positioning has already attained a positional accuracy of less that 5 microns in less than 5 minutes; accuracies and times are expected to improve significantly as the development progresses. Complementing the machine vision assembly is our manufacturable approach to silicon microbench technology. We will describe our silicon microbench optoelectronic device packages that incorporate built-in heaters for solder bonding reflow.

Polymer waveguide exhibits an easy connection with a fiber optic network and low coupling loss. Due to the large bandwidth and short signal delay time, polymer optical interconnects are gradually replacing metal interconnections. This paper presents a roof-shape polymer waveguide by using embossing method. The propagation characteristic of polymer roof-shape waveguide is analyzed by triangular-element finite-element method. The experimental fabrication shows a promising result to develop roof-shape organic polymer optical interconnection by using embossing method.

We present a device which has potential for use as a fiber sensor. The device is formed by leading two of the output ports of a 3 X 3 optical fiber flat fused coupler back to two of the input ports to form a double ring resonator structure. A 3 X 3 flat fused coupler with coupling coefficient Kl equals 0.173 II and an excess loss of about 1 dB was fabricated. The double ring resonator was formed as described. By modulating one ring with Pz element, the finsse of the device was approximately 36. Therefore; the two rings may provide one ring as a reference arm and the other ring as a sensing arm. Thus the device may have potential for use as a sensitive optic fiber sensor.

Although optical splices are protected from fluid immersion during their service life, unanticipated exposures have occurred. For this reason, Bellcore generic requirements include a water immersion test to determine whether splices can tolerate a short-term water exposure and still perform adequately. Mechanical splice failures have been observed in the field and in laboratory experiments. Almost all mechanical splices use index-matching gel, and failures were believed to result from fluid migration along the fiber/gel interface, or fluid diffusion through the gel. We used a photographic analysis to provide direct evidence for these failure modes. We immersed simulated splices in a variety of contaminated fluids and observed that the most rapid mechanism, and the one we consider most likely to result in splice failure, was fluid migration. In addition, we measured loss and reflectance performance for actual splices immersed in contaminated fluids, correlating performance to the results of our photographic analysis. We show that immersion in contaminated water representative of the outdoor plant environment accelerates splice failures.

The easily melting fluorine containing borophosphate glasses for construction knots have been obtained and investigated. The unique optical properties i.e. low refractive index - n_D equals 1.41-1.45, wide spectral transparency region from 200 to 2000 nm as well as extended temperature application range from - 70 to +300 degree(s)C, thermostability and mechanical properties determine possibility to use fluorine containing borophosphate glass as optical glue. The process of structure formation within temperature range 20-1000 degree(s)C has been investigated in details. It has been determined by IR and X-ray methods that the development of glass network begins with decomposition of components at 500 degree(s)C with further formation of glass elements within temperature range 625-675 degree(s)C. The stable glassforming area is determined by P-O-B groups. The role of fluorine in structure development depends on its depolymerizator behavior, on the other hand it has some glassforming ability. Latter is based on ability of fluorine to move from boron to phosphorus coordination sphere. For the compositions under research the formation of monofluorophosphate groups at higher temperatures have been determined. The ratio P:B equals 1, 2:2 defines obtaining of stable glass without devitrification within the temperature range from 300 to 700 degree(s)C. The interfacial processes between fluorine containing melts and quartz fiber have been investigated.

Accurate measurement of the optical loss of SCF is helpful to selecting high quality SCF and determining optimal growth conditions. By means of the SCF optic characteristic measurement set which made by ourselves, we have measured absorption spectra, fluorescence spectra and positional scatter spectra of Al₂O₃, Nd:YAG and other kinds of fibers, and some important factors which cause scattering loss have been researched. These factors include undulation of diameter, microdefects and surface wrappers of the fiber. In addition, the control of the growth conditions and improvement of the fiber qualities are mentioned.

Optical fiber gyro coils are commonly wound in a quadrupole pattern to reduce errors associated with thermal gradients and vibration. The quadrupole pattern, which is accomplished by beginning at the center of a fiber length and winding alternately from two feed reels each containing half the length, requires a complex winding machine configuration. Additional constraints on gyro coil winding are: the fiber must be wound at very low tension; the winding precision must be flawless; and winding layer transitions must be made in a way which does not degrade winding precision or induce sharp bends in the fiber. In order to satisfy all of the constraints, gyro coils are currently wound by skilled winding machine operators, using hand held implements to make small corrections to the winding produced by the machine. This painstaking manual process is costly and allows undocumented variances in the process, which can become a reliability concern. In work reported here, steps were taken to: provide machine functions required to produce a quadruple-pattern-wound gyro coil; eliminate hand contact associated with transfer between the two feed reels; maintain a consistent low tension during all stages of the winding; automated the correlated motions of product spool rotation and product spool axial traverse for maintaining a constant fiber feed angle; and develop fiber guides which reduce the requirement for manual corrections to the winding. The fiber guide studies investigated low- friction contact surfaces held in light sliding contact with fiber just behind the point of first contact with the wound coil.

The purpose of this EMPI program was to design an Automatic Coil Winding Station (ACWS) for winding Fiber Optic Gyro (FOG) sensor coils through the use of TQM, QFD, etc., followed by use of Taguchi an other statistical techniques to optimize the coil winding process. Four phases were involved: Process Definition, Critical Factor Identification, Variability Reduction, and SPC Implementation. Winding FOG coils is both difficult and fragile in that it is a quadrupole wind - as apposed to the conventional thread wind - compounded by the requirement for low tension precision, high-fiber packing density, and always risk of damage to the delicate fiber itself. The critical factor identification in the quadrupole winding process was reduced to fiber crossover - a significant detrimental influence on gyro performance - which, in turn, was closely identified with fiber gap control. The station was completed and deployed to the field where production coils are currently being wound. The ACWS not only lowered the required labor skill but succeeded in reducing the winding cycle time to 1 hour (from 24 hours) and touch labor time to 0.3 hours (from 24 hours) while improving the yield and performance through improved process control.

Assembly of a fiber optic gyros (FOG) is currently a very labor intensive process and requires extreme accuracy in assembling the components. Efforts on this Air Force program to establish the manufacturing processes and supplier base required for affordable production the tactical grade interferometric FOGs will be presented. Specific objectives of the program are three fold: demonstrate a unit production cost of $1000/axis, with a goal of $500/axis, process capability as measured by process control indices (Cp and Cpk) which must be 1.33 or higher for key processes, and a robust interferometric FOG industrial base achieved through teaming arrangements with material, component and equipment suppliers. There are eight task areas addressed in this program: optical source, couplers, integrated optic chips (IOC), optical fiber, sensing coil, electronics, assembly and test.

This task addresses the optical source and thermoelectric cooler used for tactical grade fiber optic gyros. Efforts to implement and demonstrate process improvements in such areas as screening, diode to fiber coupling, testing, process automation, and packaging will are addressed.

The availability of low cost optical fiber is essential to the commercial success of the Interferometric fiber optic gyro (IFOG). Current single mode and polarization maintaining fiber designs can meet IFOG technical requirements, but substantial cost reductions are required to meet the stringent cost goals required for the IFOG to be competitive with established gyroscope technologies. The Air Force sponsored Manufacturing Technology (Mantech) program for the Fiber Gyroscope addresses this need through the optical fiber subtask. This paper discusses the program plan for this subtask as well as appropriate cost reduction methodologies.

Automation of IFOG coil winding process for cost reduction, quality control and performance enhancements will be covered. The results of a program to develop an automation testbed are presented. The program developed a prototype quadrupole winding suitable for testing a variety of winding automation mechanisms. The effort to develop and test automation techniques is discussed. This effort will serve as a basis for Optelecom's continuing winding automation effort under the ManTech program. The ongoing effort under the ManTech program will be discussed.

The Fiber Optic Gyros (FOG) automatic optical assembly station that automates fiber preparation, splicing, rejacketing, and strength testing will be covered in this paper. The station will also encompass a console/work area where an operator can interface with the machine. By ergonomic design of the auto optical assembly station, an operator can easily gain access to the optical tray and work in parallel while the station is in the automatic mode. The goal is to reduce labor content from 160 minutes to 20 minutes per FOG triax for splicing.

We have successfully grown InGaAs detectors on the silicon substrate using the special technique of selective epitaxy. Small diameter (50 micrometers ) selective area depositions of In_0.5Ga_0.5As on silicon have exhibited a lower dislocation density, and hence, better electrical performance. These InGaAs detectors are grown by Molecular Beam Epitaxy (MBE). The final goal is to monolithically integrate InGaAs detectors with a silicon CMOS switched capacitor integrator. We have designed a CMOS switched-capacitor integrator (SCI) to realize a linear current-to-voltage conversion over a wide voltage range (-5 to +5 V) with low noise characteristics. The SCI circuit consists of an operational amplifier with a feedback capacitor and a reset switch. The SCI circuit uses +/- 5 V dual power supply and one -5 to +5 V voltage pulse generator. The circuit was simulated using PSPICE and the chip layout was done with the Mentor Graphics.