All-optical multi-wavelength header recognition using superimposed Bragg gratings based correlators S. Golmohammadi 1, * ,† , V. Akbar Nejad 2 , K. Abbasian 1 and A. Rostami 1,3 1 Nanophotonics Group, School of Engineering-Emerging Technologies, University of Tabriz, Tabriz 5166614761, Iran 2 Department of Engineering, Islamic Azad University, Tabriz, Iran 3 Faculty of Electrical and Computer Engineering, University of Tabriz, Tabriz 5166614761, Iran SUMMARY We have demonstrated that an optical correlator, based on superimposed Bragg gratings, can be used as all-optical multi-wavelength header recognition in optical packet switching networks. The proposed correlator is composed of two superimposed gratings in conjunction with variable delay lines. These superimposed Bragg gratings are used to demultiplex and multiplex the wavelength components of multi-wavelength header bit patterns. The variable delay lines create a wavelength profile that can be matched with any arbitrary bit patterns. Simulation results for all optical recognition of four-bit patterns at 10 Gbps are reported. The results show that when the header bit pattern matches the wavelength profile of the correlator, the generated auto-correlation function will include a high amplitude peak; otherwise, a cross-correlation function with low amplitude peaks will be generated in the output of the correlator. Considering this idea, multi-wavelength header is recognized by using all-optical processing method. Copyright © 2012 John Wiley & Sons, Ltd. Received 3 February 2011; Revised 12 December 2011; Accepted 8 January 2012 KEY WORDS: superimposed Bragg gratings, optical correlators, all-optical header recognition 1. INTRODUCTION Today, by using optical fiber communication technologies, high-speed, long-distance and terabit capacity networks have been developed [1]. With dramatic increasing demand for needed capacity and other performance characteristics, the realization of emerging new services such as voice over IP, video on demand, multi-media services and IP-TV, photonic crystal technology appears to be a strong candidate. To achieve these demands, optical packet switching based optical networks have been developed, where photonic packet switching offers high speed, data rate and format transparency, and configurability, which are some of the important characteristics needed in the future networks supporting different forms of data. Reliable generation and processing of headers is a critical task in all of optical packet switching networks. However, most current schemes still use electronic means and optical–electrical–optical conversions for this purpose, as the associated speed limitations restrict the header recognition and increase processing times [2]. With emergence of more real-time services, the demand for bandwidth increases, and header recognition using electronic common processors may potentially become a bottleneck at any intermediate node along the optical packet switching network. This limitation can be overcome by employing all-optical packet processing technologies in which the header recognition speed is determined primarily by the propagation delay for light traveling through some relatively short photonic structure, for example, a fiber grating or a planar light-wave circuit [2,3]. This technology promises a route to more flexible *Correspondence to: S. Golmohammadi, Nanophotonics Group, School of Engineering-Emerging Technologies, University of Tabriz, Tabriz 5166614761, Iran. † E-mail: sgolmohammadi@tabrizu.ac.ir INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS Int. J. Numer. Model. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jnm.1831 Copyright © 2012 John Wiley & Sons, Ltd.