Recent experiments have demonstrated the feasibility of both low and high speed 800 nm transmission on 1300 nm optimized single-mode fiber. Such a system is desirable for the local distribution network because it combines the high performance of single-mode fiber with the low cost of short-wavelength optoelectronic devices. This paper provides an overview of this technology. System design considerations, including splice and connector requirements to minimize mode coupling and modal noise at misaligned joints, and the choice of sources to optimize the trade-off between modal noise and material dispersion, are discussed.
A fully automated aeronomical observatory, whose main optical instruments are a field-widened Fabry-Perot interferometer and a tilting filter photometer, is described. The closed-loop control, data acquisition, and recording systems are based on the Zilog Z80A system of microprocessors and supporting components. The compact system, occupying the living room area of an Airstream trailer, is readily transportable to remote sites for unattended operation, where its operation can be remotely commanded and checked via a telephone link. The optical instrumentation, electronic control system, and operating procedures are discussed, and examples are given of data obtained from such an observatory recently located at Millstone Hill, Massachusetts. The operating experience with this observatory during its two years in the field is described.
We describe plasma-enhanced chemical vapor deposition for decomposing liquid chlorides and gaseous hydrides to yield Ge-Se and Ge-S glasses. We discuss deposition conditions for both nonisothermal glow discharge plasmas and isothermal high temperature plasmas. Our samples were examined by optical, thermal, and structural analysis to check their compositions, glass transition temperatures, and degree of microcrystallinity.
An experimental technique is presented for subjecting cracks to high rates of shear (mode-II) loading. The dynamic crack tip loading conditions are investigated for both the phase of loading and the subsequent phase of failure by means of the shadow optical method of caustics. Results that show the failure behavior observed at different rates of loading are reported.
This paper discusses the principles of a large-aperture, long-path interferometer consisting of two mirrors. Its merits include a characteristic of differential interference, a relatively relaxed requirement on optical material, high resistance to disturbance and vibration, and high accuracy of fringe location. It can operate in such adverse circumstances as an explosion field, a rocket exhaust plume field, and other transient processes. Interferograms of various flames, of the near-field structure of a rocket exhaust plume, and of a shock wave field are obtained with this interferometer.
The characterization of atmospheric turbulence at and above the two candidate sites for the 15 m National New Technology Telescope (NNTT) has required the development of specialized measurement techniques. The equipment used to measure astronomical seeing, microthermals, water vapor, and temperature is discussed, along with sample data and calibration results. By use of instruments with overlapping altitude coverage, it has been possible to "bookkeep" qualitatively all of the sources of innate degradation, especially near the ground.
An image processing system has been developed around an APOLLO workstation, tailored to the needs of processing images of photo-elastic models. Using this system, the author has made a comparative study of image processing algorithms in the analysis of a disk of araldite resin loaded in diametral compression. A differential zero-crossing algorithm has been developed, and the results obtained are compared with those from the other algorithms. The algorithms used are described, and an analysis of their effectiveness in this problem is presented with the aid of a fringe analysis system developed to analyze output from the image processing system. The results are compared with those from a mathematical solution.
This paper presents a new holographic interferometry technique, called the "cylindrical fringe carrier technique," in which the carrier fringes are not equally spaced. This technique not only eliminates the ambiguity in interpretation of holographic fringes that occurs when the carrier fringes are equally spaced, but it also can detect larger deformations and yield the required fringe spacing without precise adjustment of the object beam.
Recently, a method has been developed that uses computer vision to determine the deformations of subsets of an object. Although the method has been used successfully in a variety of applications, to date there has been no critical assessment of the key parameters in the system and their effect on the accuracy of the measured deformations. The present work presents the results of initial studies of this system. The system components are modeled, and a representative intensity pattern is chosen and deformed by known amounts. Then, the effects of varying the various parameters in the model are analyzed numerically. The most significant parameters are found to be (1) the number of quantization levels in the digitization process (i.e., the number of bits in the A/D converter), (2) the ratio of the frequency of the signal to the frequency of the sampling, and (3) the form of the intensity interpolation function.
The special flatness requirements of hard disks are discussed. Color schlieren and grazing incidence interferometry, the two methods currently dominating the market, are compared with the more recently developed moire deflectometry method. We show that since the color schlieren does not detect vital disk flatness information and since interferometry is too vibration sensitive and relatively expensive, moire deflectometry is a superior method for flatness analysis of hard disks.
The optical implementation of binary logic is desirable since many bits can be processed in parallel. Spatial filtering is an optical method that can be used for performing binary logic operations optically. In this paper we quantitatively investigate the space-bandwidth product and the crosstalk as measures of quality for several variations of this spatial filtering method. The quality parameters depend on the encoding scheme used for translating the binary information into optics.
Because sequels seem to be very popular in the movie-making business, I decided to write a sequel to an editorial that appeared in the July 1988 issue of this journal. That editorial presented some statistics related to the length of time it takes for papers to be published in Optical Engineering. As you may recall if you read it, slightly more than half of the total time required for publication is taken up by the review phase, and the excessive length of the review phase is often caused by delinquent referees. In the present editorial I give some hints for authors that may help reduce the delinquent referee problem.
The performance of image coding techniques can be enhanced through the utilization of a priori knowledge. Critical features of the image are first identified and then treated more favorably in the encoding process. In aerial surveillance imagery, thin lines and point objects constitute critical features of interest whose preservation in the encoding process is important. For the human visual system, coding degradation at low rates is more detrimental for these features than for the edges that constitute boundaries between regions of different contrast. A highly nonlinear, matched-filter-based algorithm to detect such features has been developed. Pre-enhancement (highlighting) of the detected features within the image prior to coding is shown to noticeably reduce the severity of the coding degradation. A yet more robust approach is to pre-enhance the slightly smoothed image, giving rise to an image in which all critical thin lines and point objects are crisp and well defined at the cost of nonessential edges in the image being slightly rounded off. For the transform coding techniques, distortion parameter readjustment and variable-block size coding are promising alternatives to the pre-enhancement approaches. In the former, subblocks containing any part of the detected critical features are kept within a low distortion bound by means of the local rate adjustment mechanism. The latter approach is similar except that the image is partitioned into various size subblocks based on the extracted feature map.
The noninteraction of photons makes free-space optics for optical interconnections an important asset to the digital optical computer. In this paper, we describe a space-variant optical system and apply it to the case of an optical interconnection network. As experimental proof of the device's merit, the so-called inverse perfect shuffle interconnection network is shown in one and two dimensions. Considerations regarding the demonstrated system's limitations are also presented.