Optik 124 (2013) 147–151 Contents lists available at SciVerse ScienceDirect Optik jou rnal homepage: www.elsevier.de/ijleo Blocking probability of algorithms for different wavelength assignment in optical ring network Anuj Singal, R.S. Kaler * Electronics and Communication Engineering Department, Thapar University, Patiala, Punjab, India a r t i c l e i n f o Article history: Received 7 July 2011 Accepted 15 November 2011 Keywords: Blocking probability WDM networks RWA DWDM Lightpath a b s t r a c t The blocking probability of the network is presented based on total number of wavelengths in the eight node ring network. Here, we have varied the number of available wavelength and calculate the blocking probability. Blocking probability varied from 0.8 to 0.2, 0.7 to 0.1 as number of available wavelength changed from 1 to 9 for most used and wavelength conversion algorithm, respectively. So as the number of available wavelength increases the blocking probability decreases in ring network. Also the performance of the wavelength conversion algorithms is best as compared to most used algorithm but there is burden of using expensive hardware. © 2011 Elsevier GmbH. All rights reserved. 1. Introduction Wavelength division multiplexing (WDM) optical networking is enabled by a range of technologies. Optics is clearly the preferred means of transmission, and WDM transmission is now widely used in the network. In recent years, the people have realized that opti- cal networks are capable of providing more function that just point to point transmission. Major advantages are to be gained by incor- porating some of the switching and routing functions that were performed by the electronics into the optical part of the network. In the first generation optical networks, the electronics at a node must handle not all the data intended for that node but network. If the latter data could be routed through in the optical domain, the burden on the underlying electronics at the node would be significantly reduced. This is the one of the key driver for the sec- ond generation optical networks. The optical networks based on this paradigm are now being deployed. We call this network as wavelength-routed network [1]. Routing and wavelength assign- ment problem can be defined as; given the network topology and a set of end-to-end light path requests, determine a route and wave- length(s) for the requests, using the minimum possible number of wavelengths. Routing and wavelength assignment problem is one of the main important problems of WDM optical networks. In lit- erature there are a number of methodologies proposed to tackle the RWA problem. One method is to consider the RWA problem as * Corresponding author. E-mail address: rskaler@yahoo.com (R.S. Kaler). a coupled RWA problem (single compete problem) and the other method is to divide this RWA into the two sub problems i.e. Rout- ing problem and wavelength assignment problem. The solution obtained by dividing this problem in sub problems is suboptimal but is practical to use The RWA problem can be split into two inde- pendent parts, first is find a route from the source to the destination and second is assign a wavelength to the selected route. An end- to-end light path has to be established prior to the communication between any two nodes. To establish a light path, it is required that the same wavelength be allocated on all the links along the path. This limitation is known as the wavelength continuity constraint [2]. In WDM optical networks, there are three main constraints related with wavelength assignment: wavelength continuity con- straint (WCC), distinct wavelength assignment constraint (DWAC), and nonwavelength continuity constraint (NWCC). In WCC, the same wavelength should be used on all the links along the selected route. In DWAC, two light paths cannot be assigned the same wave- length on any fiber and in NWCC; different wavelengths can be used on the links along the selected route but the nodes should have wavelength conversion capability. Wavelength conversion is the ability to convert the data on one wavelength to another wave- length. Eliminating wavelength conversion significantly reduces the cost of the switch, but it may reduce network efficiency because more wavelengths might be required. But several studies reported that the increased efficiency by using wavelength conversion is small as compared to the cost increase [3]. The blocking proba- bility of a lightpath request (or a call) is an important performance measure of a wavelength-routed network. This blocking probabil- ity is affected by many factors such as network topology, traffic 0030-4026/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijleo.2011.11.069