Optik 124 (2013) 1926–1929 Contents lists available at SciVerse ScienceDirect Optik j o ur nal hom epage: www.elsevier.de/ijleo Design and analysis of all-optical inverter using SOA-based Mach–Zehnder interferometer Pallavi Singh a,∗ , H.K. Dixit a , D.K. Tripathi a , Rekha Mehra b a Department of Electronics and Communication, University of Allahabad, Allahabad 211002, India b Department of Electronics and Communication, Government Engineering College, Ajmer, India a r t i c l e i n f o Article history: Received 1 January 2012 Accepted 29 May 2012 Keywords: Semiconductor optical amplifier (SOA) Amplifier spontaneous emission (ASE) Return to zero (RZ) SOA-based Mach–Zehnder interferometer (SOA-MZI) Cross gain modulation (XGM) a b s t r a c t In this paper an optical Boolean inverter gate has been simulated first time, with SOA-based Mach–Zehnder interferometer (SOA-MZI). The control and continuous clock pulse are properly selected so that SOA is heavily saturated and at the same time the switched out continuous clock pulse are com- pressed by the control pulse present there. To optimize the gate performance, the output contrast ratio (CR) and extinction ratio (ER) have been taken for the optimization criteria and the result is investigated at different Gb/s. However, the operation is limited by SOAs recovery time. © 2012 Elsevier GmbH. All rights reserved. 1. Introduction For years, there has been a desire to realize all-optical comput- ers using digital optical elements. Clearly this is very ambitious since optical elements lack the packing density of electronic gates because of the much shorter interaction length of electrons compared to photons. Nevertheless it is very realistic to aim at simple optical-signal processing in telecommunication networks. The requirements are not for massive processing but rather the possibility of simple optical processing at bit rates close to or beyond the bandwidth of presently available electronics i.e. 40 Gb/s and above. The all-optical processing is especially attractive in the high-capacity core networks where optoelectronic conver- sion is desired to be avoided. For most of these functions, we need simple gates that can be controlled optically. A gate used to modulate a CW signal or a pulse train can function as a wave- length converter or part of an optical regenerator whereas gating of an optical input signal can be used for time de-multiplexing [13]. Moreover, optical elements that can perform simple logic operations such as AND, XOR and inverter operation may be use- ful for routing functions. All optical gates are realized by optical nonlinearities in both glass and semiconductor materials and are relying on mechanisms, such as four-wave mixing (FWM) [14], ∗ Corresponding author. E-mail addresses: Singh.pallavi73@gmail.com (P. Singh), hkdixit@gmail.com (H.K. Dixit), dekt@rediffmail.com (D.K. Tripathi), mehra rekha@rediffmail.com (R. Mehra). cross-gain modulation (XGM), cross-phase modulation (XPM) and cross-absorption modulation (XAM) or combinations of these. Opti- cal signal processing is expected to become increasingly important in future ultra high capacity telecommunication network. The development of all-optical logic technology is important for a wide range of applications in all-optical networks including high speed all-optical packet routing and optical encryption. An important step in the development of this technology is a demonstration of optical logic elements and circuits which can also operate at higher speed. The nonlinear behavior that is a drawback for the SOA as a linear amplifier makes it a good choice for optically controlled optical gates. In 1992 the optically controlled SOA gates were first reported in [8,9]. In both these cases cross-gain modulation (XGM) was explored. The input signal is used to saturate the gain and thereby modulate a CW signal (probe) at the desired output wave- length. Gates with better performance are achieved by placing SOAs in interferometric configurations. An all-optical wavelength converter plays an important role to provide wavelength conver- sion in optical domain without disturbing the input signal [3,5]. Wavelength converter plays an important role for increasing the capacity and flexibility of future broadcast networks. The cross phase modulation (XPM) based converter has high conversion effi- ciency at low input power. In order to improve the efficiency and wideband conversion range, the XPM is increased by optimizing the semiconductor optical amplifiers active region length and bias current [4]. The interferometric wavelength converters have 2R regenerating capabilities. It is however very exciting that XGM and XPM wavelength converter combines with optical clocks lead to 3R regenerative capabilities [11]. Chiaroni has explained how 0030-4026/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2012.05.038