On the number of wavelengths and switches in all-optical networks

Abstract

Abstract-We consider optical networks using wave-a signal launched from a transmitter may arrive at a valength division multiplexing, where the path a signal riety of receivers on many different wavelengths and/or takes is determined by the network switches, the wavearrive at a receiver on several different wavelengths. length of the signal, and the location the signal originated. Therefore, a signal is routed through a combination of circuit switching and wavelength routing (asthe number of available wavelengths, 1 it will be necessary signing it a wavelength). We present a bound on the to simultaneously assign many transmitters the same waveminimum number of wavelengths needed based on the length. Since two signals using the same wavelength canconnectivity requirements of the users and the number not travel over the same fiber simultaneously, collisions of switching states. In addition, we present a lower bound on the number of switching states in a network using a combination of circuit switching, wavelength must insure that signals do not collide at any intended rerouting, and frequency changing. The bounds hold for ceiver. That is, if receiver m is listening to wavelength A all networks with switches, wavelength routing, and at time t, we must insure that only one signal assigned to wavelength changing devices.Several examples are A at time t arrives at receiver m. If two or more arrive, we presented including a network with near optimal wavelength re-use. say there is contention. In this paper we present bounds, some of which are shown to be tight, on the number of wavelengths required under various user connectivity re-I. INTRODUCTION quirements. The lower bounds allow the possibility of re-We consider all-optical networks (AONs) using wavearranging the wavelengths assigned to active sessions to length division multiplexing, circuit switching and waveaccommodate new session requests. None of the construclength routing (A-routing for short). An advantage of A-tions require rearranging. routing is spatial re-use of wavelengths. We show thatIn section II, we formalize the network model and user there is a limit to the possible amount of wavelength reconnectivity requirements.In section III, we analyze two use.special types of passive A-routing networks. We show that In a A-routing network, the path a signal takes is a funcfor these special cases, the number of wavelengths must be tion of the the wavelength of the signal and the location on the order of the number of active sessions for a broad of the signal transmitter. If the signal paths are under class of user connectivity requirements. control of the network, e.g. through the use of switches We then relax the wavelength routing restrictions used or dynamic wavelength routing devices, we say that the in section III and consider A-routing networks with arnetwork is configurable. Otherwise we say the network is bitrary topology, wavelength changers, and switches. A passive or fixed. In a configurable network, the wavelength lower bound on the number of wave...

Efficient routing in optical networks

“…In a reconfigurable network with w available wavelengths, Barry and Humblet [1994] showed that the number of wavelength-independent 2 ϫ 2 switches required to support permutation routing is ⍀(n log(n/w 2 )). 1 For the special case in which the transmitters are fixed-tuned and the receivers are tunable, Pieris and Sasaki [1993] showed that the number of wavelength-independent 2 ϫ 2 switches required for permutation routing is ⍀(n log(n/w)), and constructed such a network using O(n log(n/w)) wavelength-independent switches.…”

A heuristic for placement of limited range wavelength converters in all-optical networks

“…Similarly, in [20], approximate analytical expressions for overall blocking probabilities have been derived for various network topologies. Barry and Humblet [30] have derived a lower bound on the number of switching states in a network with wavelength converters. In [31], it is shown that wavelength converters causes insigni®cant reduction in blocking probability at light loads, whereas at medium loads, the gain is signi®cant.…”

A new duty cycle based digital multiplexing technique

“…Multiplexing is widely employed due to its capability to increase transmission capacity and to reduce system costs [2]. There are three basic types of multiplexing technique in communication systems; time division multiplexing (TDM) [4][5][6], frequency or wavelength division multiplexing (FDM) [3,7] or (WDM) [8][9][10], and code division multiplexing (CDM) [11][12][13][14][15].…”