Ljubisa Tancevski

Optical routing of asynchronous, variable length packets

We discuss the introduction/implementation of optical IP routers, then we introduce a novel scheduling algorithm incorporating void filling and aimed at optical routing of asynchronous, variable packet length packets. We describe its structure and discuss the complexity issues. Albeit introduced with the purpose of cancelling expensive optical synchronization, we argue that this approach represents the most viable all-optical approach for implementing packets-over-SONET (IP-centric scenario). We also present simulations under self-similar traffic conditions which point to the inefficiency of optical buffering to combat the effects of self-similarity, and we outline alternative strategies for proper buffer dimensioning.

Nondegenerate buffers: an approach for building large optical memories

We describe a new methodology for analyzing optical buffers with nonuniform distribution of the delay lines, the nondegenerate buffers. Coupled with an intelligent scheduling algorithm, it features improved system performance leading to more efficient and larger optical buffers. We demonstrate that the concept under bursty, both time-slotted and asynchronous traffic conditions, can lead to a sizable reduction in buffer depth requirements compared to conventional solutions.

A new scheduling algorithm for asynchronous variable length IP traffic incorporating void filling

We demonstrate that optimum switch performance can be achieved by matching the basic delay line unit in the optical buffer to the degree of self-similarity of the input traffic, in tandem with a scheduling algorithm for void filling.

Massive optical LANs using wavelength hopping/time spreading with increased security

A hybrid wavelength hopping/time spreading all-optical code division multiple access (CDMA) system using extended quadratic congruence codes for spreading and prime codes and their cyclic shifts for hopping is examined. The codes feature excellent correlation properties even in the case of an asymmetric system with random wavelength selection and the number of codes in the family is substantially increased making them attractive for massive, asynchronous LANs with increased security demands.

DEFENSE FRONTIER ANALYSIS OF QUANTUM CRYPTOGRAPHIC SYSTEMS

When a quantum cryptographic system operates in the presence of background noise, security of the key can be recovered by a procedure called key distillation. A key-distillation scheme effective against so-called individual (bitwise-independent) eavesdropping attacks involves sacrifice of some of the data through privacy amplification. We derive the amount of data sacrifice sufficient to defend against individual eavesdropping attacks in both BB84 and B92 protocols and show in what sense the communication becomes secure as a result. We also compare the secrecy capacity of various quantum cryptosystems, taking into account data sacrifice during key distillation, and conclude that the BB84 protocol may offer better performance characteristics than the B92.

WDM fiber delay line buffer control for optical packet switching

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.

Performance of an optical IP router using non-degenerate buffers

We describe optical buffers with non-uniform distribution of the delay lines, so-called nondegenerate buffers. Coupled with an intelligent scheduling algorithm, nondegenerate buffers feature improved system performance leading to more efficient and larger optical buffers for optical IP routers. We demonstrate that the concept under bursty, both time-slotted and asynchronous traffic conditions, can lead to a sizable reduction in buffer depth requirements compared to conventional solutions. The simulations point to the fact that in optical IP routers operating under asynchronous conditions, this would almost be a mandatory solution.

SDN concept: from theory to network implementation

Virtualization and cloud transformation are already revolutionizing the data center environments and are promising to bring the same cloud economics to general networking. Software Defined Networking is a prime enabler for the transition to cloud networking.

Two-dimensional CDMA systems for optical networks with increased security demands

Optical code division multiple is one of the candidates for future broadband optical networks. We investigate here the performance of such systems from the security point of view. We demonstrate that 2D coding can enhance the security aspect while still maintaining the multiuser ability. Analysis of the eavesdropping activity in the presence of multiuser interference is presented and ways to further strengthen the security aspects are discussed.

Submicrosecond transient time responses in cascades of EDFAs

Simple analytical expressions for determining the characteristic time of a single EDFA and evaluating the 1 dB time response of a cascade of EDFA are given in a form of a difference equation. It is shown that the expressions are in remarkable agreement with the results obtained through solving numerically the differential equations for chains of EDFAs. Simulations of the transient time response to channel drop/add are also included.