All-optical 4-bit binary to binary coded decimal converter with the help of semiconductor optical amplifier-assisted Sagnac switch Arunava Bhattachryya a , Dilip Kumar Gayen a , Tanay Chattopadhyay b,n a Department of Computer Science & Information Technology,College of Engineering & Management, Kolaghat, West Bengal, India b Mechanical Operation (Stage-II), Kolaghat Thermal Power Station, WBPDCL, KTPP Township, Midnapur (East), 721171 West Bengal, India article info Article history: Received 3 August 2012 Received in revised form 15 November 2012 Accepted 16 November 2012 Available online 20 December 2012 Keywords: Interferometric switches Terahertz optical asymmetric demultiplexer All-optical code conversion Optical signal processing abstract All-optical 4-bit binary to binary coded decimal (BCD) converter has been proposed and described, with the help of semiconductor optical amplifier (SOA)-assisted Sagnac interferometric switches in this manuscript. The paper describes all-optical conversion scheme using a set of all-optical switches. BCD is common in computer systems that display numeric values, especially in those consisting solely of digital logic with no microprocessor. In many personal computers, the basic input/output system (BIOS) keep the date and time in BCD format. The operations of the circuit are studied theoretically and analyzed through numerical simulations. The model accounts for the SOA small signal gain, line-width enhancement factor and carrier lifetime, the switching pulse energy and width, and the Sagnac loop asymmetry. By undertaking a detailed numerical simulation the influence of these key parameters on the metrics that determine the quality of switching is thoroughly investigated. & 2012 Elsevier B.V. All rights reserved. 1. Introduction In digital computer continuous or analog information is con- verted into digital form by means of an analog to digital converter. Conversion of optical data from decimal to binary format is very important in optical computing and optical signal processing. There are many binary code systems to represent decimal numbers, the most common being the BCD and gray code system. There is a wide choice of BCD codes, one of which is a natural BCD having a weighted code of 8421, by means of which it is possible to represent a decimal number with a combination of 4-bit binary digits. BCD is very common in electronic systems where a numeric value is to be displayed, especially in systems consisting solely of digital logic, and not containing a micropro- cessor. By utilizing BCD, the manipulation of numerical data for display can be greatly simplified by treating each digit as a separate single sub-circuit. If there are cases where the calcula- tions are relatively simple working throughout with BCD can lead to a simpler overall operation than converting to binary. The BIOS in many personal computers stores the date and time in BCD format and can be easily converted into ASCII for display. Some computers used BCD to implement floating point arithmetic. Different binary coded decimal operations such as decimal to BCD converter, gray to BCD converter and BCD addition have been proposed by different groups [1–3]. In the information age, technologies seeing a relentless demand for networks of higher capacities at lower costs. Optical communication technology has developed rapidly to achieve larger transmission capacity and longer transmission distance. Such data rates can be achieved if the data remain in the optical domain eliminating the need to convert the optical signals [4–9]. Therefore, in order to achieve higher data rates successfully, advanced optical networks require all-optical ultra-fast signal processing such as conversion [10–17], optical logic and arithmetic processing [18–22], add-drop function [23–25], and so and so forth [26–29]. Among the different proposed schemes, the terahertz optical asymmetric demultiplexer (TOAD)/semiconductor optical amplifier (SOA)- assisted Sagnac gate effectively combines fast switching time and a reasonable noise figure, with the ease of integration and overall practicality that enables it to compete favorably with other similar optical time division multiplexing devices. TOAD are characterized by the attractive features of fast switching time, high repetition rate, low power consumption, low latency, noise and jitter tolerance, compactness, thermal stability and high nonlinear properties, which enable their efficient exploitation in a real ultra-high speed optical communications environment. TOAD has the potential of being integrated, which in turn means that they can be repeatedly and reliably manufactured and massively produced so that they can be of commercial value. In this paper we propose and describe the TOAD based switch to design integrated circuit that can perform binary to binary coded Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optcom Optics Communications 0030-4018/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.optcom.2012.11.079 n Corresponding author. Tel.: þ91 9432075035; fax: þ91 3228231256. E-mail addresses: tanay2222@rediffmail.com, tanayktpp@gmail.com (T. Chattopadhyay). Optics Communications 293 (2013) 31–42