Evaluation of the Energy Consumption per Bit in BENES Optical Packet Switch Abstract—We evaluate the average energy consumption per bit in Optical Packet Switches equipped with BENES switching fabric realized in Semiconductor Optical Amplifier (SOA) technology. We also study the impact that the Amplifier Spontaneous Emission (ASE) noise generated by a transmission system has on the power consumption of the BENES switches due to the gain saturation of the SOAs used to realize the switching fabric. As a matter of example for 32 × 32 switches supporting 64 wavelengths and offered traffic equal to 0,8, the average energy consumption per bit is 2, 34 · 10 −1 nJ/bit and increases if ASE noise introduced by the transmission systems is increased. Keywords—Benes, Amplifier Spontaneous Emission Noise, En- ergy Consumption, Optical Packet Switch. I. I NTRODUCTION Q UANTITATIVE models of energy consumption in a variety of switching devices have been developed and used in a simple model of a large switched network [1]. This model provides an estimate of the lower bound on energy in a global network. Using aggressive estimates of future improve- ments in different technologies, the relative contributions of various network subsystems and components to the overall global network energy consumption has been estimated and it has been demonstrated that the energy consumption of the switching infrastructure is larger than the energy consumption of the transport infrastructure [1]. Over the past decade, several research groups have proposed optical switch fabrics based on Arrayed Waveguide Grating (AWGR) [6] or Semiconductor Optical Amplifiers (SOA) [7]-[8], primary for telecom applications. However, the lack of practical optical buffer technology creates a difficulty; solutions relying on optical buffer delay lines or deflection routing [8] cannot guarantee arbitrary delays and prevent packet dropping. On the other hand, a traditional approach relying on the store-and-forward paradigm can cause most of the bottleneck typical of electrical switches (high latency, large power consumption and a limited number of ports and switching capacity), reducing the benefits offered by optical technology. For lacking of optical buffer, bufferless optical packet switches (OPSs) are promising nodes in reducing the power consumption [9]. To solve output packet contentions they use the wavelength domain. Contending packets are wavelength converted by using Wavelength Converters. Due to the high power consumption of WCs, especially for bit-rate increasing, Optical Packet Switching architectures with shared WCs have been defined [9]. V. Eramo, L. Piazzo, M. Listanti and A. Cianfrani are with the Department of Information, Electronic and Telecommunications Engineering, Sapienza University of Roma, Via Eudossiana 13, 00184 Rome, Italy e-mail: (see http://net.infocom/uniroma1.it/homepages/eramov). A. Germoni is with Co.Ri.Tel., Via Cavour 256, 00184, Rome, Italy In this paper we propose an analytical model to evaluate the average energy consumption per bit of an Optical Packet Switch equipped with a BENES switching fabric realized in Semiconductor Optical Amplifier (SOA) technology. Sophis- ticated analytical models are introduced to evaluate the the power consumption of the devices, in particular SOAs, needed to realize the switching fabric. The introduced models allow us to evaluate the impact that Amplifier Spontaneous Emission (ASE) noise, generated by a transport system, has on the SOA’s power consumption due to the SOA gain saturation. By means of the these models, we are able to evaluate the average energy consumption per bit of the BENES switch as a function of the main system and traffic parameters and versus the characteristic of the transmission system (length, number of amplifiers, . . . ). The remainder of the paper is organized as follows. Section II describes the BENES switch. An analytical model evaluating the average energy consumption per bit in BENES switches versus the offered traffic, the switch parameters and the char- acteristics of the transmission system is described in Section III. The main numerical results are illustrated in Section IV where we provide some results on the power consumption of the BENES switch. Finally Section V provides some final remarks and concludes the paper. II. BENES OPTICAL PACKET SWITCH The studied general switching architecture is reported in Fig. 1. It is equipped with N input/output fibers (IF/OF) where each IF/OF supports M wavelengths channels. Let λ i (i =0,...,M − 1) be the wavelengths carried on each OF. In order to save power consumption, the OPS is equipped with fully shared Wavelength Converters (WC). Packets not requiring wavelength conversion are directly routed towards the Output Fibers (OF). On the contrary packets requiring wavelength conversion will be directed to a pool of WCs, wavelength converted and next routed to the OF to which they are directed. An Optical Packet Switching architecture equipped with BENES switching fabric realized in Semiconductor Optical Amplifier (SOA) technology is studied. The BENES network belongs to a class of rearrangeably non blocking networks with 2 ×2 switching elements. Fig. 2.a shows a 8 ×8 BENES switch using 20 2×2 switching elements. It is one of the most efficient architectures in terms of used number of 2 × 2 switching elements. A P × P BENES switch requires P 2 (2log 2 P − 1) 2 × 2 switching elements, with P being a power of 2 [10]. A single 2 × 2 switch can be realized in SOA technology as shown in Fig. 2.b. It is made by four SOAs, two splitters V. Eramo, E. Miucci, A. Cianfrani, A. Germoni, and M. Listanti World Academy of Science, Engineering and Technology International Journal of Energy and Power Engineering Vol:5, No:9, 2011 1241 International Scholarly and Scientific Research & Innovation 5(9) 2011 scholar.waset.org/1307-6892/15874 International Science Index, Energy and Power Engineering Vol:5, No:9, 2011 waset.org/Publication/15874