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We introduce and demonstrate a method for expanding the field of view of a typical imaging system by multiplexing images encoded onto different polarization states and recovering them from a limited number of measurements. [c] 2010 Optical Society of America OCIS codes: 110.1758, 110.5405.

Recent theoretical investigations have shown important radiometric disadvantages of interferential multiplexing in Fourier transform spectrometry that apparently can be applied even to coded aperture spectrometers. We have reexamined the methods of noninterferential multiplexing in order to assess their signal-to-noise ratio (SNR) performance, relying on a theoretical modeling of the multiplexed signals. We are able to show that quite similar SNR and radiometric disadvantages affect multiplex dispersive spectrometry. The effect of noise on spectral estimations is discussed. OCIS codes: 300.0300, 300.6300, 060.4230, 170.1630.

A method to expand the viewing window for the integral floating display by twofold through time multiplexing is proposed. The viewing window of the integral floating display can be expanded by enlarging the elemental image area for each elemental lens, by which the viewing angle of the integral imaging system is determined. Also, the difference between the effects of elemental image area expansion on the viewing characteristics of images reconstructed by the integral floating display and the integral imaging system is investigated. The experimental results verify the enhancement of the viewing window for the three-dimensional images displayed by the proposed scheme. OCIS codes: 100.6890, 110.2990.

We propose a multichanneling encryption method by using multiple random-phase mask apertures in the input plane based on a joint transform correlation scheme. In the proposal, this multiple aperture arrangement is changed as different input objects are inserted and stored. Then, during the decryption step, the appropriate use of the random-phase mask apertures can ensure the retrieval of different information. This approach provides different access levels. Computer simulations show the potential of the technique and experimental results verify the feasibility of this method. OCIS codes: 100.1160, 090.4220.

Two-dimensional (crossed) diffraction gratings with sinusoidal or truncated pyramidal (trapezoidal) profiles are proposed to have diffraction efficiency almost independent of the incident polarization inside the optical communication spectral window 1.5-1.6 [micro]m The gratings are characterized by different periods in the two orthogonal directions, chosen to support only one dispersive diffraction order in addition to the zeroth (specular) one. OCIS codes: 060.4230, 050.1950, 050.2770.

The identification (ID) data reproduction was computationally examined for the compatibility with the aperture multiplexing and the telecentric system. The mask for the multiplexing caused shade in the reproduced ID data cell. The shading tolerance was improved by modulating the phase of the original image so that the ID data holograms diffract the light in the oblique direction or with the concentrating. The telecentric system reproduced all ID data cells in the same position of the image sensor and made a distinction among the cells impossible. This was solved by reproducing the cell point symmetrically from the corresponding ID data hologram in each 3 x 3 ID data block. OCIS codes: 210.2860, 090.1760.

The exposure schedule for partially coherent hologram multiplexing, in which data pages are multiplexed by multiple signal beams and a single reference beam, is investigated in detail for the case of a [pi]/2 phase-shifted photorefractive medium. We found that the optimum recording schedule for partially coherent multiplexing cannot be determined by the classical recording schedule theory because of timeconstant errors induced by partially coherent interaction between a reference beam and self-diffraction signal beams. To overcome the issue, we derive a modified recursion equation that accounts for the time-constant errors, and we also propose a novel iterative recording-schedule correction algorism for finding the optimum solution. In the calculation with hologram multiplicity of 30 and photorefractive coupling strength of 3.0, we could successfully obtain a flat diffraction-efficiency profile aider the second recursion. OCIS codes: 190.5330, 090.4220, 210.2860.

We replace the traditional grating used in a dispersive spectrometer with a multiplex holographic grating to increase the spectral range sensed by the instrument. The multiplexed grating allows us to measure three different, overlapping spectral bands on a color digital focal plane. The detector's broadband color filters, along with a computational inversion algorithm, let us disambiguate measurements made from the three bands. The overlapping spectral bands allow us to measure a greater spectral bandwidth than a traditional spectrometer with the same sized detector. Additionally, our spectrometer uses a static coded aperture mask in the place of a slit. The aperture mask allows increased light throughput, offsetting the photon loss at the broadband filters. We present our proof-of-concept dispersion multiplexing spectrometer design with experimental measurements to verify its operation. OCIS codes: 120.620, 090.1970.

A reflection-type holographic disk memory system with random phase shift multiplexing is proposed. The experimental results show that a binary data page of 18 X 17 bits is recorded successfully at intervals of 4 [micro]m in a Fe:LiNb[O.sub.3] crystal with a thickness of 0.5 mm when six data pages are superimposed. Numerical results show that random phase modulation can improve the shift selectivity in shift multiplexing recording as well as in data security. Experimental and numerical results show that reflection-type holographic disk memory has a high potential for terabyte storage capacity as in transmission-type memory. OCIS codes: 210.2860, 090.7330.

Hadamard multiplexing is a measurement strategy that yields best sensitivity improvements over scanning measurements for signal-independent detector noise. The presence of photon noise degrades the performance of Hadamard multiplexing because of the increase of photon noise by the superposition of multiple signals. I derive the reduction of the sensitivity gain of a Hadamard measurement and an upper limit for the gain of any cyclic multiplexing strategy in the presence of photon noise. This upper limit clearly exceeds the reduced Hadamard gain and can be achieved by multiplexing sequences that differ from Hadamard S sequences but also share some similarities with respect to their autocorrelation. Examples of such sequences are given. As the analysis shows, the presence of photon noise limits the gain of multiplexing strategies to a finite value, which depends on the ratio between photon noise and detector noise and cannot be exceeded by increasing the number of multiplexed channels. In addition, only switching multiplex schemes, which superpose either all the light or no light of individual channels, can achieve the upper limit of the gain. OCIS codes: 230.4110, 350.6980, 120.3940, 270.5290.

Thin-film filters used for dense wavelength division multiplexing (DWDM) applications are processed by a variety of deposition techniques, including ion-beam sputtering. Ion-beam sputtering produces high-quality coatings and provides flexibility of coating materials. However, DWDM filters consisting of oxide films that are reactively deposited by ion-beam sputtering, as in most sputter techniques, typically exhibit high levels of compressive stress. This affects the optical characteristics of the filters. Details of the filter passband characteristics and wave-front distortion illustrate the influence of the stress. Spatial variation of the stress on the filter surface causes the filter center wavelength to have spatial variation, and it causes the filter to have an asymmetric passband characteristic. OCIS codes: 060.0060, 060.1810, 310.6860, 310.1860, 310.6870.

We present a polarization-multiplexed optical memory with urethane-urea copolymers. The side chains of the urethane-urea copolymers induce cis-trans isomerization by illumination of blue or green light, and they align perpendicular to the linear polarization of the illuminated light, thus producing optical anisotropy. We found that the material showed selective anisotropy for the particular direction that was perpendicular to that of the recording beam polarization. By use of the anisotropic property three different data pages were multiplexed at the same spot of the medium. Erasure of the recorded bit data is also demonstrated.

A design for an all-optical crossbar network utilizing wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) technology and a combination of free-space optics and compact optical waveguides is presented. Polymer waveguides route the optical signals from a spatially distributed array of processors to a central free-space optical crossbar, producing a passive, all-optical, fully connected crossbar network directly from processor to processor. The analyzed network could, relatively inexpensively, connect local clusters of tightly integrated processors. In addition, it is also believed that such a network could be extended, with wavelength reuse, to connect much larger number of processors in a multicluster network.

Dispersion of the phase shift upon reflection of the reflectors is used to narrow the spectral bandwidth of an all-dielectric bandpass filter for wavelength division multiplexing. The bandwidth is altered by the shifting of the order numbers of the spacer layers (of multiple half-wave optical thicknesses).

The generalized Wigner function is able to represent light distributions that contain spatial and temporal information. The use of such a generalized Wigner distribution function for analysis and understanding of temporally restricted superresolving systems is demonstrated. These systems gain spatial resolution by conversion of the temporal degrees of freedom to spatial degrees of freedom.

Optical space code-division multiple access is a scheme to multiplex and link data between two-dimensional processors such as smart pixels and spatial light modulators or arrays of optical sources like vertical-cavity surface-emitting lasers. We examine the multiplexing characteristics of optical space code-division multiple access by using optical orthogonal signature patterns. The probability density function of interference noise in interfering optical orthogonal signature patterns is calculated. The bit-error rate is derived from the result and plotted as a function of receiver threshold, code length, code weight, and number of users. Furthermore, we propose a prethresholding method to suppress the interference noise, and we experimentally verify that the method works effectively in improving system performance. OCIS codes: 060.0060, 060.2340, 200.4560.

We report on the implementation of an optical crossbar interconnect consisting of a centralized free-space beam-steering subsystem, a distributed array of vertical-cavity surface-emitting lasers and photoreceivers, a fiber image guide, and a large-core polymer fiber array. The interconnect can in principle handle more than 350 cross-bar channels, but our implementation demonstrated only 240 channels. Transmissions of 500-Mbit/s per channel were demonstrated. Approximately 12.7-dB end-to-end optical channel attenuation was measured. Details of component design, packaging, system integration, and testing are presented and discussed. OCIS codes: 060.2330, 060.4230, 160.5470, 200.4650.

We demonstrate the storage of 1000 holograms in a memory architecture that makes use of different wavelengths for recording and readout to reduce the grating decay while retrieving data. Bragg-mismatch problems from the use of two wavelengths are minimized through recording in the image plane and using thin crystals. Peristrophic multiplexing can be combined with angle multiplexing to counter the poorer angular selectivity of thin crystals. Dark conductivity reduces the effectiveness of the dual-wavelength method for nonvolatile readout, and constraints on the usable pixel sizes limit this method to moderate storage densities. Key words: Volume holographic memory, dual-wavelength method, nonvolatile readout, peristrophic multiplexing, exposure schedule.

We propose and test experimentally a new scheme to implement spatially multiplexed multiwavelength holographic memory. An electro-optically modulated phase grating array on LiNb[O.sub.3] substrate is used as a guided-wave interconnect to activate the reconfigurable reference beam. The object beam is provided by free-space interconnect. An electro-optic modulation efficiency of 18 [+ or -] 2.5% is achieved with an applied voltage of 100 V. The reference beams with different diffraction angles can implement the angle-multiplexing holographic recording. We believe this is the first report of the implementation of guided-wave electro-optic interconnect together with free-space interconnect in holographic memory applications. Key words: Guided-wave interconnect, free-space interconnect, electro-optically modulated phase grating array, modulation efficiency, holographic memory, angle multiplexing.

The performance of Fourier-transform profilometry is enhanced by a new technique that is based on spatial frequency multiplexing combined with the Gushov-Solodkin phase unwrapping algorithm. The technique permits the three-dimensional shape measurement of objects that have discontinuous height steps and/or spatially isolated surfaces, which has not been possible by conventional Fourier-transform profilometry. An important feature of the technique is that it requires only a single fringe pattern; the single-shot recording makes possible the instantaneous three-dimensional shape measurement of discontinuous objects in fast motion. Experimental results are presented that demonstrate the validity of the principle. Key words: Phase unwrapping, profilometry, fringe analysis, optical metrology, heterodyne interferometry, Fourier transform.

We describe an encrypted holographic data-storage system that combines orthogonal-phase-code multiplexing with a random-phase key. The system offers the security advantages of random-phase coding but retains the low cross-talk performance and the minimum code storage requirements typical in an orthogonal-phase-code-multiplexing system. Key words: Holographic data storage, encryption, phase-code multiplexing.

We propose and demonstrate an effective two-stage modified signed-digit optical computing technique (in contrast to previous three-stage techniques) based on spatial data encoding, polarization multiplexing, and multiple imaging. Our proposed reduction in operation stages requires a reference operation in addition to the transformation and weight operations common to three-stage systems. In our system's first stage a transformation (or weight) operation and a reference operation are implemented in parallel by use of four distinct polarization-multiplexed kernel operations. In the second stage the final desired result (e.g., addition and subtraction) and its complement are obtained in parallel with a single kernel operation. The operation speed of our two-stage modified signed-digit computing method is 33% faster than previous three-stage modified signed-digit algorithms.

We demonstrate the integration, in a single glass substrate, of a 1.48/1.55-[[micro]meter]-wavelength multiplexer and a 1.30/1.55-[[micro]meter]-wavelength multiplexer followed by a 1/8 splitter by using potassium- and silver-double-ion-exchange processes. The wavelength multiplexers are based on nonsymmetric three-port Mach-Zehnder interferometers, and symmetrical Y junctions are used for achromatic splitting. The facet-to-facet excess loss in both the 1.48/1.55-[[micro]meter] multiplexer and in the integrated 1.30/1.55-[[micro]meter] multiplexer and 1/8 splitter is less than 2.7 dB. The device can be used, in connection with an erbium-doped fiber, in future wavelength division multiplexing subscriber networks in which amplification is needed in the 1.55-[[micro]meter]-wavelength region.

A method is described for arrangement of channels from different stages of a three-dimensional shuffle/exchange network so that only a single set of optics is needed to perform the two-dimensional shuffles. This arrangement is based on our earlier one-copy algorithm. It requires a feedback system and is an example of a space-multiplexed optical multistage network. We discuss the design issues and experimental results.

A single-transmission holographic optical element capable of broadband five-channel demultiplexing in multimode fiber is described. A holographic optical element demultiplexer combines a hologram on dichromated gelatin with a computer-generated hologram. A design of the demultiplexer with a nonspherical wave front based on ray tracing and the optimization technique perfectly permits five cross-talk isolations by reducing the aberrations of multiple focused spots caused by a recording-readout wavelength shift. Such a system has a channel separation of 300 micrometers (20 nm in wavelength difference) between adjacent fibers in an operating laser diode wavelength region of 0.8-0.88 micrometer. Experiments demonstrating the feasibility of this demultiplexer with a 780-nm laser diode source are presented.

A partially multiplexed fiber-optic-based sensor network based on low coherence interferometry is reported for which the scanning interferometer simultaneously sweeps the coherence-matched region of each sensor. The advantage of this approach is that the signal-to-noise ratio is maximized while the cross talk between sensors is minimized. The normal requirement that each sensor must be fabricated with a different length also does not apply. The concept is demonstrated by multiplexing two bulk optic Michelson interferometers. A resolution of equivalent to 50 nm with an operational range of 200 micrometer was achieved in the prototype system.

The advantages and limitations of data storage in holograhic materials by implementing a pure phase-encoding method of the reference beam are studied. We show that if deterministic orthogonal binary phase addresses are used, such a system is theoretically able to store as many images as the usual angular multiplexing method. However, we demonstrate that imperfections of available optical components generate optical noise and limit the storage capacity. We propose an improved recording technique to overcome some of these limitations.

We use d-dimensional shuffle patterns to describe optical frequency division multiplexing. A complexity measure is derived from the geometry of common shuffle patterns and is extended to evaluate d-dimensional shuffle patterns. The least complexity of the generated patterns is determined with respect to the size and the dimension of the data sets. Trade-offs between the dimension of the data sets and the frequency-conversion-based processing of the the pattern generation are discussed. A comparison of multiplexing on vectors and arrays is presented. The relation of the complexity analysis to the design of optical frequency division multiplexing systems is briefly discussed. Key words: Photonic switching, d-dimensional shuffle, maximum skew, complexity, optical frequency division multiplexing, frequency conversion, subdivided multiplexing, laser tuning, crossing of channels.

A narrow-band ten-channel optical multiplexer and demultiplexer for densely spaced wavelength division multiplexing in multimode fiber communication systems are discussed. These devices consist of a Fourier diffraction grating having very high diffraction efficiency (85%), a telecentric lens system with low aberration, and a unique fiber array. The devices had a very narrow channel spacing of 1.9 nm and low dependence on polarizations in the range from 831.6 to 848.5 nm. The multiplexer had a bandwidth of 0.7 nm and the demultiplexer had a bandwidth of 1.1 nm. Key words: Optical multiplexer/demultiplexers, Fourier gratings.

Based on the diffractive properties of a transmission-type phase volume hologram, a new type of polarization-division multi/demultiplexer for optical communications is presented.

A new dynamic model for gain-clamped fiber amplifiers is presented. The model can simulate the transient behavior of a gain-clamped erbium-doped fiber amplifier as a function of its controlling parameters. Results show the detailed dependence of the amplifier gain dynamics on launched pump power and reveal the pump-power penalty incurred in implementing gain control with minimal transients to power disturbances. The effect on the transients of varying the laser cavity feedback coupling is also presented. Model accuracy is verified by the excellent quantitative agreement with dynamic measurements over a range of operating conditions. Results show how an increase in pump power can effectively suppress both the dynamic and the steady-state signal power transients in wavelength-division multiplexing channel add-drop operations. [C] 2000 Optical Society of America OCIS codes: 060.0060, 060.2320, 140.3280, 060.2410.

For analysis of effective phase-code multiplexing in a holographic memory system four types of phase code are generated and used as a reference beam. In computer simulations the size of the address beam is fixed at 32 x 32 pixels, and 0%, 5%, 10%, 15%, 20%, and 25% phase-error rates in a pixel are purposely added to the real phase values for consideration of the nonlinear phase-modulation characteristics of a practical spatial light modulator. Cross talk and signal-to-noise ratios (SNR's) are comparatively analyzed for these phase codes by calculation of the autocorrelation and the cross correlation. The pseudorandom code (PSR) has the lowest cross-correlation mean value of 0.067 among the four types of phase code, which means that the SNR of the PSR is higher than with other phase codes. Also, the standard deviation of the PSR, indicating the degree of recalled data degradation, has the lowest value, at 0.0113. [C] 2000 Optical Society of America OCIS codes: 210.0210, 210.2860, 210.4590, 210.4680.