Two-Dimensional Optical Buses for Massively Parallel Processing

We report the formation of an optical bus using compression-molding technique. The linear dimension of such a waveguide is well beyond that of a microlithographically defined waveguide. Theoretical calculation based on the effective index method was used to determine the optimal dimension of the molding tool design for single- and multimode waveguides. A molded photolime gel-based polymer optical bus with a linear dimension of 45 cm was fabricated and then tested at 0.6328-μm wavelength. Waveguide propagation loss from 0.5 to 2 dB/cm was determined using the two prism method. As a result of this long interconnection distance, board-to-board optical interconnects through backplane can be realized using the technology.

In the production of 60-inch anti-aircraft searchlight reflectors by the electroforming process, convex parabolic forms are used as molds. To avoid production of reflectors with excessive spherical aberration, it is necessary to know the inherent spherical aberration of each mold. To obtain this information, an apparatus has been devised to measure the spherical aberrations of the convex surface of a paraboloid of revolution. The optical system of the apparatus consists essentially of a collimator, a plane mirror, and a photographic plate used in the following manner. A narrow beam of light parallel to the optical axis of the mold to be tested is projected from the collimator onto a designated spot of a particular zone on the mold which is in a horizontal position. The beam of light is reflected from the mold as if it were coming from the virtual focus for the designated spot. The reflected light strikes the plane mirror, vertically placed in a predetermined position and is re-reflected so that the beam of light intersects the optical axis of the mold at a distance above the mold equal to the focal length for the designated spot in the mold being examined. The photographic plate is placed horizontally at a distance above the mold equal to the nominal focal length of the mold. The beam of light intercepts the photographic plate and produces a specified image. Eight such images are photographed on one plate at equally spaced intervals around the periphery of the zone being tested. A required number of zones are tested. Simple interpretation of the photographs yield the amount of aberration present. An important feature of this apparatus is that the interpretations of the photographs are identical to those obtained for testing concave parabolic reflectors. This apparatus aids reflector production in that it determines the abberation characteristics of the convex mold directly, thus eliminating the previous practice of making a reflector from a mold to determine the mold’s accuracy indirectly.

On the law of the partial polarization of light by reflexion

Low latency, high bandwidth interconnection networks that directly link arbitrary pairs of processing elements without contention are very desirable for parallel computers. Most communication networks in parallel machines have made compromises due to the limitations of electronics. Many of the optical interconnection schemes proposed have simply replaced the point-to-point copper wiring with fiber optics and have not made use of the unique properties of optics. This paper proposes an optical interconnect architecture for over a hundred processors, which contains a dedicated channel for each processor to eliminate global arbitration and to provide bandwidth that scales with the number of processors in the machine. Unlike electrical buses, this architecture is not limited by the medium (fiber optics) used to connect the transmitters and receivers. Each processor has an array of receivers, one receiver for each processor channel. The architecture of the receiver array permits a variety of different parallel programming models to be efficiently supported.

The miniaturization and integration of in-plane micro-lenses into microfluidic networks for improving fluorescence detection has been widely investigated recently. This article describes the design and demonstration of an optofluidic in-plane bi-concave lens to perform both light focusing and diverging. The concave lens is hydrodynamically formed in a rectangular chamber with a liquid core liquid cladding (L 2) configuration. In the focusing mode, an auxiliary cladding stream is introduced to sandwich the L 2 configuration for protecting the light rays from scattering at the rough chamber wall. In the diverging mode, the auxiliary cladding liquid changes its role from avoiding light-scattering to being the low-refractive-index cladding of the lens. The focal length in the focusing mode and the divergent angle of light beam in the diverging mode can be tuned by adjusting the flow rate ratio between core and cladding streams.

SUMMARY A simple method which can be applied in seismic codes to determine the critical angle of seismic incidence and the corresponding peak response of structures subjected to two horizontal components applied along any arbitrary directions and to the vertical component of earthquake ground motion, is proposed in this paper. The seismic components are given in terms of response spectra that may be equal or have di⁄erent spectral shapes. The structures are discrete, linear systems with viscous damping. The method, which is based on the response spectrum method of analysis, requires the solution of standard cases of seismic analysis and therefore can be easily implemented in standard computer programs. For the general case of three arbitrary response spectra, the method requires the solution of five seismic loading cases, two for each horizontal component and one for the vertical component. If the horizontal response spectra have the same shape or if there is only one horizontal component, it is then required to solve just two seismic loading cases for the horizontal components and one for the vertical component. It can be shown that the formulas derived for the critical angles and the peak response are essentially identical to the ones obtained earlier by Smeby and Der Kiureghian using random vibration theory. The application and the accuracy of the method is illustrated by means of numerical analysis of buildings, comparing the results with those obtained using other proposed methods. For the specific case of two horizontal spectra with identical shape and an arbitrary vertical spectra, the critical angle neither depends on the spectral ratio of the two horizontal components nor on the vertical spectrum. For the special case of equal horizontal spectra, the structural response does not vary with the angle of incidence and it is an upper bound for all possible responses. ( 1997 by John Wiley & Sons, Ltd.

We demonstrate a simple and versatile method for generating various configurations of optical vortices from a Gaussian light beam by using glass plates and an astigmatic mode converter (AMC). The glass plates are inserted into the Gaussian beam to imprint nodal lines along the edges, and the AMC then transforms the beam with the nodes into a vortex beam. The procedures are discussed in terms of a transverse-mode expansion of the paraxial light beam, in which each Hermite-Gaussian mode is converted into the corresponding Laguerre-Gaussian mode by the AMC. We generated several vortex configurations, and the results show good agreement with the theoretical predictions.

A simple method of interferometric measurement of angular displacement utilizes the change of optical path produced by rotation of a plane parallel glass plate., The main drawback of the method is that, its sensitivity is dependent on the angle of incidence at the plate, The sensitivity has a maximum value for a particular angle of incidence dependent upon the refractive index of the glass plate used. We report here the results of measurement of the change of path difference with angular rotation upto 40 minutes for a plane parallel glass plate at angles of incidence near that for maximum sensitivity. It is shown that at the maximum sensitivity the relation between path difference and angular displacement shows good linearity and that the departure from linearity is less than 1 second of arc. This makes the method suitable for calibration of some angle measuring devices and practical applications of the method are suggested.

Due to many experimental data required and a lot of calculations involved, it is very complex and cumbersome to model prism-based liquid-refractive-index-measuring methods. By use of the feature of TE-polarized wave and TM-polarized wave and differential measurement principle, we developed a new method of mathematical modeling for measuring refractive index of a liquid based upon Fresnel formula and prism internal reflection at incident angle less than critical angle. With this method only two different concentrations measurements for a kind of solution can lead to the determination of computational model. It introduces the principle of an optic-fiber sensor system based on prism-coupler for measuring refractive index of a liquid, and it contains the configuration picture of the sensing optical path, the spectrogram of the semiconductor laser and the structure block diagram of measuring system, the system is mainly made up of the semiconductor laser with 1654.14nm in wavelength, 1×2 optical switch, Y-shaped photo-coupler with coupled rate 50:50, the detector based on isosceles prism-coupler, the data process and control system based on AT89C51 and photoelectric transformer. For TM-polarized wave and TE-polarized wave, theoretical simulations show that the ratio of sensitivity is 1.11, therefore, the beam that the component of TM-polarized wave is more than the one of TE-polarized wave is advantageous to heightening the systemۥs measurement sensitivity. Measurements are performed to examine the validity of the theoretical model and four theoretical models are given, and these results indicate the feasibility of four theoretical models with an error of 3%. In this study, a beam of light is broken down into two beams in the coupler of Y-shaped coupler, the one acts as the reference optical path, the other is known as the sensing optical path, consequently the method can limit well the fluctuation of the light source, the variation of the photodiodeۥ s dark-current of photodiode and many other interfering factors and can be used for real-time detection and online analysis of liquid refractive-index. The method is also capable of measuring even smaller changes in the optical refractive index of the material on a metal surface by the surface plasma resonance sensing techniques.

To overcome the shortcomings of the existing optical axis determination method’s optical path is a complex, cumbersome operation with difficulty in identifying criteria. According to Huygens’ drawing principle, this paper establishes a mathematical model between incident light and the outgoing distance of o-light and e-light, analyzes the optical system between the incident angle and refraction angle, deduces the relationship between the incident angle and the distance between two beams of light, designs a distinction scheme between o-light and e-light, proposes a distance method to determine the optical axis based on the difference between the two optical mathematical models, and verifies that although e-light does not meet the refraction law in birefringence, its optical path is reversible. The designed optical axis determination method is simpler, easier to operate, and simpler in identifying criteria than the existing optical path. The validity of the analysis is verified by experiments.

The drastically reduced costs and improved performance of fiber optic components in recent years offers an opportunity to economically incorporate high-bandwidth optical communication links within a large-scale multiprocessor system. In this paper, the design, implementation, and initial performance of a fiber optic bus for a tightly coupled multiprocessor system are discussed. This optical bus ulitizes a multiple fiber-multiple star configuration with data rates of up to 80 MHz. It transmits bus control line information by repetitively scanning the control lines and transmitting their states as a packet of bits. It is currently being used for a 30-processor system called the Heidelberg Polyp, which has a custom bus design. However, the design approach is a general one that could easily be adapted to other buses, especially asynchronous buses such as the VME bus.

Polymer waveguides have attracted a great deal of attention for their potential applications as optical components in optical communications, optical interconnections and optical sensors because they are easy to manufacture at a low temperature, and they have a low processing cost. Hot embossing is powerful and effective tools to produce a large volume of waveguides and structure high-precision micro/nano patterns of thin polymer films using a stamp for optical applications. In this work, fabrication techniques of hot embossed polymeric optical waveguides for parallel optical interconnection module, multi-channel variable optical attenuator and optical printed circuit boards are demonstrated. The single- and multi-mode waveguides are produced by core filling and UV curing processes. New approaches to fabricating single-mode polymeric waveguides with the high thermal stability in thermosetting polymers and two-dimensional multi-mode polymeric waveguides for high-density parallel optical interconnections as well as a simultaneous fabrication of single-mode polymeric waveguides with micro pedestals for passive fiber alignment are also reported.

Measurements of the polarization of visible light by transmission through glass plates are discussed as being worthwhile undergraduate laboratory experiments. At the introductory level, the experiments are to becarried out at Brewster's angle of incidence, for which a simple polarization formula is derived without use of Fresnel's equations. At the more advanced level, familiarity with the latter permits the data to be analysed at arbitrary angles of incidence, and allows a single correction to be made for reflections. Examples of data taken with the present apparatus are presented and the results compared with theory.

The autocorrelation, or the Wiener-Khintchine, theorem plays a pivotal role in optical coherence theory. Its proof derives from the time-frequency Fourier theorem. The derivation requires either dropping the cross-products (interference terms) between the different filed amplitudes corresponding to different frequencies, or taking time integration over the entire duration of the signal. The physical interpretation of these mathematical steps implies either (i) non-interference (noninteraction) between different frequencies, or (ii) the registered data is valid for interpretation when the detector is set for long time integration. We have already proposed the generic principle of Non-Interaction Waves (NIW), or absence of interference between light beams. The hypothesis of non-interaction between different frequencies was used by Michelson to frame the theory behind his Fourier Transform Spectroscopy, which is correct only when the detector possesses a long integrating time constant like a human eye, a photographic plate, or a photo detector circuit with a long LCR time constant. A fast detector gives heterodyne signal. So, the correlation factor derived by the prevailing <i>coherence</i> theory, and measured through fringe visibility, is essentially the quantum property of the detecting molecules compounded by the rest of the follow-on instrumentation. Low visibility fringes (low correlation factor) does not reflect intrinsic property of light alone; it is a light-matter joint response characteristics. So, we re-define <i>coherence</i> by directly referring to the key characteristics of light beams being analyzed as: (i) <i>spectral correlation</i> (presence of multi frequency), (ii) <i>temporal correlation</i> (time varying amplitude of light), (iii) <i>spatial correlation</i> (independent multi-point source), and (iv) <i>complex correlation</i> (mixture of previous characteristics).

Staggered circular cylinders immersed in a uniform planar shear flow