Constructing multi-Terabit switches and routers entirely out of electronic cross-bars require multiple racks of switches and huge number of interconnects. The cost and power consumption of such a system is very high and has a limited scalability. The all-optical switching has the problem of buffering and processing and the construction of multi-terabit switches and routers based on all-optical switching is not feasible in the near future. However, based on a hybrid approach, using optical cross-bars with nanosecond switching time and large bandwidth and DWDM interconnects in
conjunction with electrical memory, one can construct huge and highly scalable switches and routers.
Advanced network planning concerns effective network-resource allocation for dynamic and open business environment. Planning methodologies of ASON implementation based on qualitative analysis and mathematical modeling are presented in this paper. The methodology includes method of rationalizing technology and architecture, building network and nodal models, and developing dynamic programming for multi-period deployment. The multi-layered nodal architecture proposed here can accommodate various nodal configurations for a multi-plane optical network and the network modeling presented here computes the required network elements for optimizing resource allocation.
A high-speed optical packet switching node using the WDM all optical switch structure is studied in this paper. Tele-traffic performance of an all-optical IP packet router is simulated under the self-similar (bursty) traffic condition. Four different control algorithms are investigated for the performance and complexity. A simple round-robin algorithm cannot attain an acceptable performance. Finding minimum buffer occupancy and sorting the packets by length are methods used to improve the IP router performance.
Interest in the deployment of Wavelength Division Multiplexing in regional and metropolitan networks has increased recently. We consider an example of regional/metropolitan rings and investigate the interaction of node-induced crosstalk with fiber nonlinearities in it. The phenomenon is studied in two cases, namely the case of Non-Zero Dispersion Shifted Fiber operating in the anomalous dispersion regime and the case of Single Mode Fiber with uniformly distributed segments of Dispersion Compensating Fiber. The dependence of the effect of the crosstalk/nonlinear interaction on the frequency difference between signal and crosstalk carriers and on signal power is examined in detail. It is shown that the node-induced crosstalk can interact with fiber nonlinearities and introduce limitations on transmission performance. This interaction should therefore be taken into consideration in designing regional and metropolitan networks.
The increased data traffic experienced today and the projected increase in the data traffic in the future demand exploration of novel approaches to IP transport such as transport of IP traffic over optics. The bimodal nature of the IP traffic short packets which are typical of transactional-style flows and large packets or bursts which are encountered in the transport of large data blocks requires, design of routers that are capable of routing packets with variable lengths efficiently. In this paper, we discuss the design aspects of such all-optical IP-switches. The broadcast and select architecture is a prime candidate for implementing optical IP routers. Construction of optical routers with buffering, wavelength conversion and multipath routing are considered. The merits and demerits of all these cases and the effect of buffer size, wavelength conversion and multiple-path routing on the blocking probability and probability of packet loss are discussed.
The traditional procedure to synthesize optical devices with specified transmission characteristics is to start from device parameters such as refractive index profile with a known transmission characteristics that is close to the specified characteristics of the device and iteratively change the device parameters until the specified transmission characteristics of the device is achieved. This traditional procedure is time consuming and the choice of initial device parameters that has a transmission characteristics close to the specified characteristics is not always easy. However, techniques based on inverse scattering theory can directly provide the device design parameters given the specified transmission characteristics of the device. The inverse scattering techniques contrasts the traditional design procedure by their ability to yield design parameters in a non-iterative manner. The transmission of electromagnetic radiation in an optical waveguide is governed by vector wave equations which can be simplified to scalar wave equations under the assumption of “weakly guiding” approximation for TE and TM modes. The scalar equations obtained for TE and TM modes can be recast into Schrodinger type of equation that is normally encountered in quantum mechanics. One can draw an analogy between the quantum mechanical problem and the optical device problem. The potential well of the quantum mechanics corresponds to refractive index profile of the optical device problem; the time evolution of wave packets in quantum mechanics corresponds to propagation of optical modes along the axis in an optical device and the existence of discrete bound states in quantum mechanics is analogues to the presence of discrete propagating modes which in the geometrical-optics model corresponds to the modes that satisfy total internal reflection. Now, the refractive index profile; an important device parameter can be reconstructed from an assumed scattering coefficient that characterizes the specified transmission characteristics of the device. An analytical technique based on Gelfand-Levitan-Marchenko integral formulation and an numerical technique that extends the capability of the inverse techniques to provide solutions for generalized reflection coefficients that have been developed by us will be discussed. Design of a class of devices such as intra-chip optical interconnects, all-optical logic devices and efficient guiding structures for integrated optical amplifiers based on the inverse techniques will be discussed. The design of efficient guiding structures for optical amplifiers requires a guiding medium that has same propagation constant for both the signal and the pump. This leads to the inverse theory for reconstruction of energy dependent potentials or wavelength dependent refractive indices. We have solved this problem and we will show you a refractive index profile of a guiding structure obtained by inverse scattering technique that has same propagation constant at 1.55mm and 0.98/mm. The extension of the inverse techniques developed for planar structures to cylindrical structures is not straight forward, rather very cumbersome. However, we have succeeded in developing inverse scattering theory for the design of multimode cylindrical optical waveguides with same propagation constant for all modes and the design of single mode fiber that has the same propagation constants for more than one wavelength. Such structures will find application in image transmission and fiber amplifier design respectively. Our talk will include discussion of these cases.
An inverse scattering theory is used to design gradient-index optical waveguides capable of transmitting images without degradation. The propagation characteristics on N modes each carrying a pixel of the image are specified by a transverse rational reflection coefficient. The Gelfand-Levitan-Marchenko inverse scattering theory is used to obtain the unique solution of the permittivity profile of the waveguide from the reflection coefficient.