The decay of higher order solitons in optical fiber, initiated by localized channel perturbations such as a step change in dispersion, a localized loss element, or a bandpass filter, is explored theoretically and experimentally as a means of generating pairs of pulses having wavelengths that are up and down-shifted from the input wavelength. The achievable wavelength separation between the two sub pulses increases with increasing the amount of perturbations. Pulse parameter requirements for achieving useful wavelength shifts while avoiding unwanted nonlinear effects are presented. Experimental studies for N=2 solitons having 1 ps initial width are performed to demonstrate tunable wavelength conversion using a step change in dispersion and using a loss element. Wavelength shifts are tunable by varying the magnitude of a dispersion step or loss element that is used to disrupt the soliton cycle. Competing nonlinear effects, such as cubic dispersion, self-steepening, and stimulated Raman scattering, can be minimized by using input pulsewidths of one picosecond or greater. The separated pulses at two wavelengths can in principle be amplified to form separate higher order solitons. The process repeated to produce multiple wavelength replicas of an input data stream, and may thus be of possible use in multi-casting applications in fiber communication systems. The possibility of soliton recovery is also studied. For soliton recovery, conditions are stringent, in that the precise temporal overlap and phase relationship between sub-pulses that occurred at the point of separation is in principle needed at the reverse perturbation location. Experimental studies on soliton recovery for an N=2 soliton is performed by using a dispersion-compensated intermediate link, and reversing the dispersion step. Detrimental effects on soliton recovery are studied.

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Photonic crystals (PCs) are nano-structured materials in which a periodic variation of the dielectric constant of the material results in a photonic band gap. By introducing defects into PCs, it is possible to build waveguides that can channel light along certain paths. It is also possible to construct micro-cavities that can localize photons in extremely small volumes. In this dissertation, to begin with, we computed the photonic crystals dispersion relations and found the photonic band gap (PBG) by the plane wave expansion method (PWE) in the frequency domain. Then, the finite difference time domain method (FDTD) along with the perfectly matched layer boundary conditions was adopted to solve Maxwell¡¦s equations, equivalent to simulate the movement behavior of the Photonic crystals. By properly varying the size of the defect on the PCs, it could really drop the particular wavelengths and guide them to output channels by PCs waveguides. We proposed the structures that would function as Wavelength-Division-Multiplexer (WDM). Secondly, coupled cavity waveguide of PC was used to control group velocity that achieved the slow light property. By calculating dispersion curve with PWE, we obtained group velocity characteristics in PCs waveguide. Meanwhile, we designed a novel Time-Division-Multiplexer (TDM) system by controlling the group velocity characteristics. Finally, we designed cascade ring resonators and expected to obtain an extendable delay line. Conventional delay line devices are propagating in a long waveguide to obtain the delay line property. An excellent delay line and ultra-small size properties are expected in the proposed structure. Because nano-technology has been making great progress steadily, it surely can be used to demonstrate a practical breakthrough in which the devices based on the PC integrated circuits are realized. These devices will be a potential key component in the applications of ultra-high-speed and ultra-high-capacity optical communications and optical data processing systems.

Light scattering and color shift are two major sources of distortion for underwater photography. Light scattering is caused by light incident on objects reflected and deflected multiple times by particles present in the water before reaching the camera. This in turn lowers the visibility and contrast of the image captured. Color shift corresponds to the varying degrees of attenuation encountered by light traveling in the water with different wavelengths, rendering ambient underwater environments dominated by bluish tone. This paper proposes a novel approach to enhance underwater images by a dehazing algorithm with wavelength compensation. Once the depth map, i.e., distances between the objects and the camera, is estimated by dark channel prior, the light intensities of foreground and background are compared to determine whether an artificial light source is employed during image capturing process. After compensating the effect of artifical light, the haze phenomenon from light scattering is removed by the dehazing algorithm. Next, estimation of the image scene depth according to the residual energy ratios of different wavelengths in the background is performed. Based on the amount of attenuation corresponding to each light wavelength, color shift compensation is conducted to restore color balance. A Super-Rsolution image can offer more details that must be important and necessary in low resolution underwater image. In this paper combine Gradient-Base Super Resolution and Iterative Back-Projection (IBP) to propose Cocktail Super Resolution algorithm, with the bilateral filter to remove the chessboard effect and ringing effect along image edges, and improve the image quality. The underwater videos with diversified resolution downloaded from the Youtube website are processed by employing WCID, histogram equalization, and a traditional dehazing algorithm, respectively. Test results demonstrate that videos with significantly enhanced visibility and superior color fidelity are obtained by the WCID proposed.

Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Stephen E. Ralph. / Vita. Includes bibliographical references (leaves 281-296).

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Optical networks based on Wavelength Division Multiplexing (WDM) technology show many clear benefits in terms of high capacity, flexibility and low power consumption. All these benefits make WDM networks the preferred choice for today’s and future transports solutions which are strongly driven by a plethora of emerging online services. In such a scenario, capability to provide high capacity during the service provisioning phase is of course very important, but it is not the only requirement that plays a central role. Traffic dynamicity is another essential aspect to consider because in many scenarios, e.g., in the case of real time multimedia services, the connections are expected to be provisioned and torn down quickly and relatively frequently. High traffic dynamicity may put a strain on the network control and management operations (i.e., the overhead due to control message exchange can grow rapidly) that coordinate any provisioning mechanisms. Furthermore, survivability, in the presence of new failure scenarios that goes beyond the single failure assumption, is still of the utmost importance to minimize the network disruptions and data losses. In other words, protection against any possible future failure scenario where multiple faults may struck simultaneously, asks for highly reliable provisioning solutions. The above consideration have a general validity i.e., can be equally applied to any network segment and not just limited to the core part. So, we also address the problem of service provisioning in the access paradigm. Long reach Passive Optical Networks (PONs) are gaining popularity due to their cost, reach, and bandwidth advantages in the access region. In PON, the design of an efficient bandwidth sharing mechanism between multiple subscribers in the upstream direction is crucial. In addition, Long Reach PONs (LR-PONs) introduces additional challenges in terms of packet delay and network throughput, due to their extended reach. It becomes apparent that effective solutions to the connection provisioning problem in both the core and access optical networks with respect to the considerations made above can ensure a truly optimal end-to-end connectivity while making an efficient usage of resources. The first part of this thesis focuses on a control and management framework specifically designed for concurrent resource optimization in WDM-based optical networks in a highly dynamic traffic scenario. The framework and the proposed provisioning strategies are specifically designed with the objective of: (i) allowing for a reduction of the blocking probability and the control overhead in a Path Computation Element (PCE)-based network architecture, (ii)  optimizing resource utilization for a traffic scenario that require services with diverse survivability requirements which are achieved by means of  dedicated and shared path-protection, and (iii) designing provisioning mechanism that guarantees high connection availability levels in Double Link Failures (DLF) scenarios. The presented results show that the proposed dynamic provisioning approach can significantly improve the network blocking performance while making an efficient use of primary/backup resources whenever protection is required by the provisioned services. Furthermore, the proposed DLF schemes show good performance in terms of minimizing disruption periods, and allowing for enhanced network robustness when specific services require high connection availability levels. In the second part of this thesis, we propose efficient resource provisioning strategies for LR-PON. The objective is to optimize the bandwidth allocation in LR-PONs, in particular to: (i) identify the performance limitations associated with traditional (short reach) TDM-PON based Dynamic Bandwidth Allocation (DBA) algorithms when employed in long reach scenarios, and (ii) devise efficient DBA algorithms that can mitigate the performance limitations imposed by an extended reach. Our proposed schemes show noticeable performance gains when compared with conventional DBA algorithms for short-reach PON as well as specifically devised approaches for long reach. / <p>QC 20130520</p>

Clinical guidelines dictate that frequent blood glucose monitoring in diabetic patients is critical towards proper management of the disease. Although, several different types of glucose monitors are now commercially available, most of these devices are invasive, thereby adversely affecting patient compliance. To this end, optical polarimetric glucose sensing through the eye has been proposed as a potential noninvasive means to aid in the control of diabetes. Arguably, the most critical and limiting factor towards successful application of such a technique is the time varying corneal birefringence due to eye motion artifact. In the first part of this research, we describe a birefringent ocular model along with a geometric ray tracing scheme to serve as a tool towards better understanding of the cornea’s birefringence properties. The simulations show that index-unmatched coupling of light is spatially limited to a smaller range when compared to index-matched situation. Polarimetric measurements on rabbits’ eyes indicate relative agreement between the modeled and experimental values of corneal birefringence. In addition, the observed rotation in the plane of polarized light for multiple wavelengths demonstrates the potential for using a dual-wavelength polarimetric approach to overcome the noise due to time-varying corneal birefringence. These results will ultimately aid in the development of an appropriate eye coupling mechanism for in vivo polarimetric glucose measurements. The latter part of the dissertation focuses on design and development of a dual wavelength optical polarimeter. The described system utilizes real-time closed-loop feedback based on proportional-integral-derivative (PID) control, which effectively reduced the time taken by the system to stabilize while minimizing the effect of motion artifact, which appears as common noise source for both the wavelengths. Glucose measurements performed in both in vitro and ex vivo conditions demonstrate the sensitivity of the current system. Finally, in vivo results in rabbits indicate that dual-wavelength polarimetry has the potential to noninvasively probe glucose through the anterior chamber of the eye.