This PDF file contains the editorial “Web of Science” for OE Vol. 42 Issue 06

Multilayer storage in a shift-multiplexed holographic disk is proposed. We consider the longitudinal shifting selectivity of the reference beam as another degree of freedom available for multilayer multiplexing storage. A novel optical readout head comprising a fiber array is designed to replace the longitudinal translation stage.

This paper presents some of the most important features of the Miró code, which is a laser propagation program for high-peak-power laser setups. The main propagation models are discussed: the paraxial nonlinear Schrödinger approximation, broadband computation including dispersion effects, and spatial and temporal Talanov transforms are described, as well as the main optical components: a four-level multipass amplifier including both saturation and narrowing effects; broadband and noncollinear frequency conversion; the grating, including high-order dispersion effects; and laser damage effects. Some elementary examples of Miró computation are also provided.

We present a method for automatic camera calibration that requires only that a planar pattern be visible by the camera from a few (at least three) different views. A major issue is how to obtain the projection of an absolute point using the planar pattern. In the calibration, we can move either the camera or the planar pattern and no knowledge about the motion is required. We consider and resolve both linear and nonlinear parameters. In testing the proposed methods, satisfactory results are achieved in the simulation and in real data experiments.

Chaotic sequences are potentially attractive in a range of engineering applications such as broadband communication, radar application, and pattern recognition. Most such applications require, as a minimum, an accurate estimation of the actual chaotic sequence from a noisy signal. Classical signal-processing techniques are not adequate for this class of signals, which behave like noise although they are deterministic in nature. Consequently it is important to develop new algorithms for robust and efficient estimation of these signals in noise. Some such algorithms are currently available. Most are limited to ideal situations with very high signal-to-noise ratios. This paper presents a novel algorithm to estimate the initial condition of a chaotic signal (and hence the chaotic sequence if the mapping function is known). It is a general algorithm that can be of broad use. It is also shown to outperform standard algorithms that are in current use. This split-region approach is applicable for a wide range of signal-to-noise ratios, and provides reasonable estimates down to 5 dB.

We describe the incremental computing method for making localized changes to a computer-generated hologram to rapidly modify the 3-D image it reconstructs. The method populates a scene with holographic primitives, tracks scene-based changes, and updates the diffractive contributions of only affected primitives. Changes are rapidly incorporated into the hologram via simple arithmetic operations, and only affected regions of the hologram are updated at each simulation time step. The method can accommodate different holographic primitive representations, is designed to be suitable for hardware assistance, and is also compatible with computer-graphics-style techniques for smooth shading, texture mapping, and reflections.

Data fusion is the study of optimal information processing in distributed multisensor environments with the benefits of more reliable detection and higher immunity to noise and sensor failures. We investigate applications of the data fusion principle to the handoff problem in popular code-division multiple access (CDMA) cellular wireless communication networks. When a mobile station traverses a cell boundary, cell handoff is required to make the transition of a mobile between cells smoother without degrading performance. CDMA multiple access allows soft handoff, in which the signal strength of the mobile is detected and tracked by the searchers from more than one base station. The cell receiving the strongest signal strength handles signal processing. We demonstrate that the signal detection quality in the handoff region can be further improved by fusing the detected results from multiple base stations. A new fusion handoff strategy is designed, and its error performance measures are derived analytically in the presence of log-normal shadowing. Theoretical fading margin analysis shows that the fusion handoff approach offers better network performance over conventional hard and soft handoffs.

We implement a fully phase encryption system, using fractional Fourier transform to encrypt and decrypt a 2-D phase image obtained from an amplitude image. The encrypted image is holographically recorded in a barium titanate crystal and is then decrypted by generating through phase conjugation, a conjugate of the encrypted image. The decrypted phase image is converted into an amplitude image by the phase contrast technique using an electrically addressed spatial light modulator. Experimental results in support of the proposed idea are presented.

The fabrication of an electric field detector using an electro-optic LiNbO₃ (LN) single crystal is studied for an application to check the electric field of a conductively patterned panel. When this electric field detector moves on the surface of the panel, a constant air gap, which is close enough for the given field intensity and resolution, must be maintained so as not to damage the surface patterns. For the effective detection of electric field change in this air gap state, an LN single crystal is selected because of its relatively high electro-optic coefficient, transmittance, and low dielectric constant. X-cut LN and Z-cut LN structures are selected to estimate the applicability of LN by simulation on the optical intensity variation and electric field distribution of various structures. At an air gap of 10 μm in the Z-cut LN structure, Vπ is about 100 to 150 V and optical intensity variation with unit voltage (Q) is 6.7%/V larger than that of the X-cut LN structure. From these characteristics, the Z-cut LN structure proves to be applicable for the electric field detector because the variation of optical intensity (0.8 μW) is sufficient in the ac driving voltage region (∓20 V) of a real system.

Low-reflectance fiber Bragg gratings (FBGs) can be interrogated in real time with a high-resolution optical time-domain reflectometry (OTDR) technology. The technique allows interrogation of a series of FBGs with the intensity change based on the OTDR pulse spectral characteristics and the FBG reflection. Experimental results are presented for multiplexing of dual-wavelength FBG sensors to produce referencing calibration in sensor measurement. With this structure, the influence of the source power fluctuations and fiber bend losses can be greatly reduced. This scheme can be applied to the practical measurement of distributed temperature or strain.

We develop a compact automated fiber cross-connect module with micro-optical connectors that uses a fiber-handling robot to cross-connect any of 100 input optical fibers to any of 100 output fibers. The micro-optical connectors and fiber-handling robot make the module about a quarter of the size of a conventional automated cross-connect module. Experimental results show that the module's average cross-connection time is about 1 min and the initial insertion loss is less than 0.7 dB.

We present an update on the progress of the development of the Naval Research Laboratory's (NRL's) multiple-quantum-well retromodulators for compact, low-power communications. We report results for data-in-flight on a small, unmanned aerial vehicle at up to 5 Mbps, in preparation for real-time video transfer using an array of devices. This data was taken at Chesapeake Bay Detachment. We also report transference of color video using wavelet compression at 15 and 30 frames/s, at 4 to 6 Mbps in the lab, at eye-safe intensity levels. The unit is a corner cube modulator using a 980-nm shutter. A five-element array was used for the data-in-flight. First results of our 1550-nm devices are also presented as progress in a "cat's eye retromodulator."

The striae quality grades defined by the U.S. military standard MIL-G-174B, the ANSI/OEOSC OP3.001-2001 standard, and the ISO 10110-4 standard are evaluated to determine if they can be used to specify optical glass for high-quality optical elements. The evaluation is done by using each standard to determine the striae quality grades of 26 samples. The samples are representative of the striae quality grades, called shadowgraph grades here, defined by Schott Glass Technologies and used daily to control production of optical glass and to select glass for high-quality optical elements. The results show that all three standards need to define additional striae quality grades in order to specify glass for high-quality optical elements. The additional grades should be equivalent to the best shadowgraph grades: the Precision, A, and B grades.

In digital holography, it is necessary to know the distance of the object from the recording charge-coupled device camera to obtain a correct numerical reconstruction process. The presence of a plane parallel plate along the path of the object beam, such as a beamsplitter cube, often used in interferometers, affects the actual reconstruction distance. This effect, to our knowledge, has never been discussed in the literature despite the fact that it adds a contribution that cannot be ignored in the reconstruction process. We evaluate the effect for a spherical object wavefront as well as in the case of an extended object.

We have demonstrated that it is possible to fabricate the conical multiplex hologram as an image-plane hologram using a simple optical system. Based on ray tracing, the imaging properties of lenses, and coordinate transformation, a theory directly relating the observed image point to the original object point is formulated, which facilitates numerical simulation of the whole observed image. A search over the holographic parameters shows that a condition for the least-distorted image, limited by the particular shape of the hologram, can be obtained. Numerical simulation is given, together with some experimentally reconstructed images of a real object. The result shows that it indeed eliminates the so-called picket-fence effect as encountered in the traditional multiplex holography.

We present a wavelet packet image coding algorithm combined with the actual coding costs. It is composed of five parts: (1) wavelet packet decomposition and best basis selection based on a new cost function, which is designed to be combined with the actual coding costs so as to select a sequential coder-friendly wavelet packet basis; (2) uniform quantization for all the wavelet packet coefficients; (3) a quadtree classifying procedure, used to code the significance map as well as to classify the wavelet packet coefficients; (4) the universal trellis coded quantization (UTCQ), used to code the classified coefficients; and (5) the entropy coder, used to code the indices of the universal trellis coded quantizer's output, the significance map coding output, and the wavelet packet decomposition structure. The image coding results, calculated from actual file sizes and images reconstructed by the decoding algorithm are either comparable to or surpass previous results obtained through much more sophisticated and computationally complex methods for texture-rich images, such as "Barbara" and fingerprints.

Digitized images are used widely in current industrial applications; however, digital images cost a huge storage capacity, leading to transmission bandwidth constraints. Therefore, an image compression technique was developed to solve this drawback. Differential pulse code modulation (DPCM) is the most widely used method among predictive image coding schemes. It is based on the notation of quantizing a prediction error signal after the prediction operation to reduce the original data complexity. The design of the predictor influences the performance of the whole DPCM. Therefore, the predictor constitutes a central topic in the DPCM system. We make efforts toward the design of a predictor by using a genetic algorithm (GA). By the operations of crossover and mutation, several predictor coefficients are yielded after hundreds of generations. The predictor generated by the GA outperforms the current eight different predictive schemes in Joint Photographic Experts Group lossless (JPEG-LS) still image compression standard. Because the JPEG-LS compression scheme is currently the most widely used lossless compression method, our results contribute to the applications of compression.

We present a novel vector filtering technique for color image restoration that incorporates a new fuzzy inference system for noise detection. This is combined with a switching scheme to select between an identity filter output and the output from a proposed L-filter design. The proposed L-filter is designed to exploit the ordering techniques of the vector median filters, and thus it requires only a set of two coefficients. These coefficients are trained using a constrained least-mean squares approach, which is capable of converging to the optimum set within a short period of time. The new algorithm treats the intensity and color of each pixel individually until the final output is to be calculated, thus, the optimal magnitude and direction of the pixel vectors are used.

We describe multispectral image processing with three visible bands and a near-infrared band, whose pictures are taken by the multispectral sensor. We have improved multispectral classification for remote sensing to detect the target. The improved method features the division of the measured image by the target signature to remove the effect induced by illuminance change. The multispectral vector is transformed to angular space, so that the target position is always in (π/4, π/4) in angular coordinates. Then the translation of the angular coordinate is carried out so that the target position comes to the origin. The target class is determined by setting the decision boundary around the origin. The experiment reveals the effectiveness of this method.

Vessel tracking is an essential step for 3-D reconstruction and quantitative analysis of angiograms. We present a multiresolution vessel tracking method and its application to 2-D coronary angiographic images. The method consists of: 1. multiresolution wavelet decomposition; 2. wavelet denoising; 3. vessel valley map generation in a low-resolution image; 4. vascular tree construction; 5. valley course refinement using a "peg-quiver" algorithm; and 6. lumen diameter calculation using a derivative-free edge detection algorithm. A vessel valley map consisting of all vessel valley points can be generated using a star-scan scheme, followed by local minima detection along each scanline. The vessel paths and vascular trees are then constructed by using a recursive "depth-first" searching scheme on the valley map. A peg-quiver refinement algorithm produces optimal valley courses in high-resolution images by alternatively pegging and quivering the control points and the interpolated points. With high-resolution valley courses, vessel boundary is defined by exploiting vessel cross-section profiles. Compared to centerline-based vessel tracking, the vessel-tracking scheme using valley courses exhibits more simplicity, effectiveness, and stability.

A new approach describing the behavior of the infrared (IR) images of natural terrain is presented. The model takes into account the nonisotropic nature of the terrain and the image diurnal changes due to sun motion. The model constructs the spatial autocorrelation function (AF) of terrain images, its nonisotropic nature, and the diurnal variations of the parameters describing this function. The proposed model assumes that the AF is composed of a superposition of two terms, one representing the shadowing effect, while the second represents the clutter inherent physical properties. Both are represented by an elliptical AF that is characterized by three parameters: (1) the power coefficient (the relative strength of each process), (2) the axis orientation in the horizontal plane, and (3) the aspect ratio between the two major axes. An analysis of measured and simulated images shows that the shadowing term follows the diurnal sun motion. At sunrise its power coefficient is very high (it "turns on" in a very short time), and its major axis orientation correlates very well with the sun azimuth. The aspect ratio of the two axes is influenced by the sun elevation angle. On the other hand, the inherent term has almost a constant aspect ratio and orientation angle.

An electronic circuit is developed for automating the implementation of a laser frequency-locking technique based on wavelength modulation spectroscopy. The locking scheme uses a zero-crossing as a reference point to line center generated by a derivative-like error signal. Prior implementations have suffered from a limitation in that the zero-crossing must be manually distinguished from the zero signal encountered when the laser is tuned far from line center. This disadvantage is eliminated by developing a circuit that automatically searches the laser's tuning range for an absorption peak and then engages the frequency lock. Both solid state and diode lasers are locked to absorption lines of gases including water vapor and carbon dioxide, with a long-term stabilization to within a few percent of the absorption linewidth.

The surface profile of an Al thin film and its thickness are observed by electronic speckle pattern interferometry (ESPI). The Michelson interferometer is used as our basic interferometric system to obtain interference fringes on a CCD camera. These interference fringes depend on the path differences due to the surface contours of the thin film. The interference fringes are analyzed with the fast Fourier transform method and a wrapped phase is obtained. An unwrapping procedure is used to obtain a continuous phase. Results on thickness measurement are presented.

A polychromatic speckle pattern can be understood as an addition of N independent speckle patterns. We use the simple model for polychromatic speckle contrast, with some modifications, to evaluate the number of independent speckle patterns that contribute in the image plane. These speckle patterns may have different mean intensities depending on the surface heights distribution function. We derive a formula for the addition of multiple independent speckle patterns with different mean intensities and calculate the contrast for a surface with Gaussian statistics versus a surface with uniform distribution of the surface heights.

The design of a triple-field-of-view optical system for 3- to 5-μm infrared focal-plane arrays is described. Preliminary calculations are done to determine the first-order parameters of the narrow-, medium-, and wide-field-of-view modes. An optical configuration based on the combination of axial motion of a lens group and the rotate-in motion of two separated lens groups is used. Diffractive and aspheric surfaces are employed to control the color and monochromatic aberrations, thereby decreasing the total number of lenses used. Paraxial and real-ray modeling of the narcissus effect, which plays an important role in the optical design of infrared systems, is explained. The final optical designs along with their aberrations curves and polychromatic modulation transfer function plots are presented, showing acceptable performance in all fields of view.

We describe the use of an optical fringe projection method to measure the dynamic response of small components. In this method, sinusoidal fringes are projected on a small component using a programmable liquid crystal display (LCD) projector and a long-working-distance microscope (LDM). The image of the fringe pattern is captured by another LDM and a high-speed camera and subsequently processed by the fast Fourier transform (FFT) technique. A simple procedure is described that enables calibration of the optical setup for subsequent amplitude and frequency measurement of small vibrating components. A method that enhances the detection range of the system is also included.

Determination of phase difference is important in many applications of optical metrology. Algorithms for temporal phase difference measurement using the Fourier transform and phase shifting methods are available. These algorithms are first shown to be equivalent and then are generalized for spatial phase difference measurements and a spatial carrier phase shifting method. The efficiency of the algorithm is verified by two examples for slope and curvature determination.

The Ronchi test with a LCD amplitude sinusoidal grating is used for testing convergent optical systems. The rulings are computer-generated and displayed on the LCD. By displaying various phase-shifted rulings and capturing the corresponding images, the phase is obtained with the conventional phase-shifting algorithms. For reference, experimental results are compared with those on a commercial Fizeau interferometer.

Fabrication of digital sinusoidal gratings and precisely controlled diffusive flats and their application to calibration-based highly accurate phase-shifting projected fringe profilometry are presented. The main advantages of using digital sinusoidal gratings are (1) high geometrical accuracy (< 1 μm); (2) high contrast ratio; and (3) very low high-order harmonic distortion. In addition, a high-quality diffusive flat with precisely controlled lateral correlation length, fabricated by VLSI processes, offers a good calibration standard. It is found that, by applying these two components to the calibration-based phase-shifting projected fringe profilometry, absolute 3-D surface profile measurement accuracy on the order of microns can be achieved.

Buffering with optical delay lines (ODLs) in optical packet-switching networks is a way to mitigate network contention. We study queueing models of ODLs in synchronous and asynchronous optical packet-switching networks under uniform Bernoulli traffic. We first introduce a Markov chain model for a finite-length ODL forward-buffering system in synchronized networks and calculate the stationary distribution of its queueing length as well as two important queueing parameters: packet loss rate (PLR) and average queueing delay (AQD). We then introduce an asymptotic analysis based on the generating function of an infinite buffering system and present approximate expressions for PLR and AQD. Numerical calculations demonstrate that these asymptotic estimates of PLR and AQD are quite accurate. We then extend the queueing analysis to feedback-buffering ODLs in synchronized networks. We present numerical calculations of PLRs and AQDs for feedback-buffering ODLs. Finally, we introduce queueing models in asynchronous networks for forward buffering or for feedback buffering without multiple recirculations. We carry out the asymptotic analysis to characterize the performance degradation of ODL buffering in asynchronous switching when the traffic load is high.

The time response of optical switching properties of Sb thin films under focused laser pulses is investigated. The results show that the response course can be divided into onset, opening, and closing stages. Formulas for their lengths are given. The onset and opening times decrease with increasing pumping light power density. The closing time is about 150 ns. For optical memory, if the power density of the readout and recording lasers changes from 5×10⁹ to 15×10⁹ W/m², the onset time changes from 2.5 to 0.30 μs, and the opening time is on the nanosecond scale.

Fabrication and characterization of four-layer polymeric optical waveguides with a glass + SAN (styrene acrylonitrile) + polystyrene + air structure is reported. The propagation losses in these multilayer waveguides are reduced by 30% in comparison to single-layer polystyrene-based waveguides. We also present the optimization of other basic waveguiding properties such as index profile, guide thickness, and birefringence.

We design a multichannel polychromatic nonzero-order joint transform correlator (NOJTC). The system is implemented using a general JTC scheme by the design of an ideal reference function and additional power-spectrum subtraction strategy for a multichannel correlator. We test the performance for noise and distorted images in the input. In addition, the introduction of various numbers of images in the training set is investigated. The multichannel polychromatic NOJTC shows better detection ability over conventional systems.

This study investigates the use of low-cost infrared sensors in the differentiation and localization of target primitives commonly encountered in indoor environments, such as planes, corners, edges, and cylinders. The intensity readings from such sensors are highly dependent on target location and properties in a way that cannot be represented in a simple manner, making the differentiation and localization difficult. We propose the use of angular intensity scans from two infrared sensors and present a rule-based algorithm to process them. The method can achieve position-invariant target differentiation without relying on the absolute return signal intensities of the infrared sensors. The method is verified experimentally. Planes, 90-deg corners, 90-deg edges, and cylinders are differentiated with correct rates of 90%, 100%, 82.5%, and 92.5%, respectively. Targets are localized with average absolute range and azimuth errors of 0.55 cm and 1.03 deg. The demonstration shows that simple infrared sensors, when coupled with appropriate processing, can be used to extract a significantly greater amount of information than they are commonly employed for.

We analyze within the first-order approximation the design of a scatterometer with a prolate ellipsoidal mirror that collects the light from a rough surface and a subsidiary optical system that focuses the light onto an image plane.

A new intermediate view reconstruction technique based on the adaptive disparity estimation algorithm is proposed. First, the feature values indicating the local image complexity are extracted from the input stereo image pair by using edge detection and matching algorithms. Then, the matching window size for disparity estimation is adaptively selected depending on the magnitude of these feature values. That is, for the region having larger feature values, the smaller matching window size is selected, while for the opposite case, the larger matching window size is selected by comparison with a predetermined threshold value. This new approach is not only able to reduce the mismatch of the disparity vector, which occurs in conventional fine disparity estimation with a small matching window size, but also can reduce the blocking effect, which occurs in coarse disparity estimation with a large matching window size. Some experimental results show that the proposed algorithm improves the peak signal-to-noise of the reconstructed intermediate view up to 2.93 to 4.09 dB and reduces the execution time to 39.34 to 65.62% on average in comparison with those of conventional algorithms.

The pump beam for an end-pumped solid state laser can likely be fit by a super-Gaussian beam. We normalize the super-Gaussian beam for different orders (m). Numerical temperature solutions are obtained for super-Gaussian beams using the finite element method. We find that these numerical temperature solutions can be fit by a Gaussian function. This is important as all of the subsequent thermal radial and tangential stresses, refractive index changes, optical path differences (OPDs), birefringences and depolarization losses can be solved analytically and they follow Gaussian profiles. Different m have different thermal effects as well as different overlap efficiencies. We analyze the effects of different m on different pump powers, different pump beam sizes, and different rod radii. This analysis could provide valuable data for correcting phase distortions of high-power operation.

Morphological granulometric moments have proven useful for quantification and classification of image texture. This paper proposes using granulometries to provide a comprehensive description of surface roughness. To support this proposition it demonstrates that granulometric surface description includes much of the information carried by conventional roughness measures. It does so by using granulometric moments as inputs to a linear system to estimate six conventional surface roughness measures. The analysis is based on simulations in the framework of the Boolean-random-function model for surfaces. Features are obtained from both opening and closing granulometries. The granulometries are generated by computationally efficient one-dimensional linear and triangular structuring elements. This permits fast implementation using special-purpose algorithms. Estimators with granulometric inputs are designed on training data and applied to test data to analyze their effectiveness as estimators of conventional roughness measures. This is done for both simulated and real images.

We describe experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the temperature interval 21 to 96°C. We present the measured fluorescence spectrum corresponding to the energy levels ²H_11/2 and ⁴S_3/2. This sensor features simple signal detection in a band and its data analysis system, incorporating a power ratio to reduce noise effects. The channel responsivity, power ratio, and sensitivity for a number of possible filters are presented. By using filters transmitting the 527- to 537-nm and 545- to 555-nm spectral bands, the following figures of merit are achieved: the responsivity is greater than 0.2 μW/K, and the sensitivity is 0.0065 K^–1. With a custom-made filter centered on 545 nm, even higher sensitivity is predicted.

The occurrence of spikes in Brewer UV spectra is studied. Use is made of continuous measurement data over several years, comprising more than 90,000 spectra, from one single-monochromator and two double-monochromator Brewers. It is shown that the double monochromators, especially, may suffer from more than 200 spikes per ~5000 annual spectra. The spikes are not always randomly distributed over the wavelength range. The single monochromator is found to have an annual average of only 36 spikes above 300 nm, but it is noted that there were a significant number of spikes at shorter wavelengths, indicating possible bias in the stray light correction unless taken into consideration. The error caused by noncorrected spikes varies greatly from case to case. In an intensive study of 150 spectra measured during one summer week, the effect of one moderate-size spike was found to be more than 5% on a DNA action dose rate and close to 1% on a DNA action daily dose. When high accuracy of in situ UV measurements is required, our results suggest a need to remove spikes from the spectra. A simple statistical approach is employed. The method is applicable to any single- or double-monochromator Brewer spectroradiometer. However, under rapidly changing cloudiness it can be difficult to distinguish between noise spikes and the variation in irradiance due to changes in the state of the sky. Our data show that ancillary radiation measurements may be necessary to interpret the data correctly.

A method is described for using a photosimulation laboratory environment to evaluate the effectiveness of camouflage for military vehicles. There are distinct advantages to acquiring images at the field site and then bringing them back to a laboratory environment for observer testing versus taking the subjects out to the field for estimating detection probability. Laboratory testing using field-acquired imagery provides a repeatable, secure, and relatively low-cost way to generate consistent data for the measurement of the effectiveness of camouflage relative to a baseline vehicle, and the calibration and validation of target acquisition models. A laboratory test procedure is described in which a baseline light armored vehicle (LAV) is compared to a treated LAV in the Tank-Automotive and Armaments Command (TACOM) Visual Perception Laboratory (VPL) using imagery collected from the field in the manner prescribed by an experimental design.

Watermarking is a potential method for copyright protection and authentication of multimedia data on the Internet. The watermarking process can be viewed as a communication task, where the watermark, acting like information, is embedded into a host image, acting like noise, in a communication channel that is susceptible to all kinds of attacks, acting like jamming. In this paper, a novel watermarking scheme using frequency-shift keying (FSK) modulation with high-variance block selection is proposed to achieve superior performance in robustness and imperceptibility. In the proposed scheme, a secret bit is embedded into two rather than one DCT coefficient of a block. This is analogous to the FSK as opposed to the amplitude-shift keying (ASK) modulation in digital communication. High-variance block selection (HVBS) is employed to enhance robustness. In order to solve the synchronization problem caused by HVBS, local block selection and a novel technique called the two-state constraint is implemented. In order to demonstrate the effectness of the proposed scheme, simulations under various conditions were conducted. The empirical results show that our proposed scheme can sustain most common attacks, including JPEG compression, rotating, resizing, cropping, painting, noising, and blurring. A comparison between watermarking with and without HVBS shows that HVBS with the two-state constraint can effectively enhance robustness without the sacrifice of imperceptibility. The enhancement is much more significant for host images with fluctuation characteristics than for those with smooth characteristics. The comparison between ASK and FSK shows that the extracted watermark from the latter deteriorates gracefully and that from the former is blown out as the strength of a JPEG attack rises beyond a threshold. For other common attacks, the ASK and FSK perform about the same except, for the blurring attack, for which the extracted watermark from the latter can be clearly identified while that from the former is blown out.

An analysis of a cross-phase modulation (XPM) wavelength converter integrated with preamplifers for increased input power dynamic range is reported. The performance of the preamplified wavelength converter can be deteriorated by the residual reflectivity of semiconductor optical amplifiers (SOAs) inside the converter. We investigate the trade-off relationship between the internal reflectivity of SOAs and the performance of the XPM wavelength converter with an integrated preamplifier through bit error rate (BER) calculation. The optimal physical and operating parameters of the preamplified XPM wavelength converter are proposed.

In wavelength-division multiplexing (WDM) optical systems, as the number of users is increased, the crosstalk becomes more severe due to imperfections in the passive optical filters (gratings) and nonlinear effects due to the power increasing in the optical fiber. We consider only stimulated Raman scattering (SRS) as the nonlinear degradation in this multichannel system. We propose an adaptive neural network algorithm based on back-propagation networks to mitigate these crosstalk problems. We also show that the back-propagation neural network algorithm has a better performance than the least mean squares (LMS) algorithm.

This PDF contains the communication "Constrained energy minimization and the target-constrained interference-minimized filter."