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Implementation of 4 bit electrical gray to optical binary converter using the electro optic effect in the Mach Zehnder interferometer.

INTRODUCTION

In digital communication system, combinational and sequential circuits performs various process like switching, multiplexing, demultiplexing, encoding, decoding, code conversion and basic/complex computational techniques. There are different types of techniques are available to implement the digital combinational and sequential systems. The logic gates can be used to make the basic combinational building blocks, but it may not be efficient. Based on electro-optic effect, MZI has been widely used to implement the optical switching, which can make simpler the mechanism [1]. Based on electro-optic effect, optical switching phenomena in MZI is effectively utilized and it is used to implement the optical full adder and full-subtractor [2]. Implementation of XOR/XNOR and AND logic gates using MZI done [3]. The XOR/XNOR logic gates are the most essential to design various digital function like parity checker and generator, code converters and etc. The optical 1*4 signal router has been implemented with the help of electro-optic effect using number MZI [4]. The signal router design was leads to implement the optical MUX/DEMUX, encoder and decoder using MZI. Based on electrooptic effect, the sequential circuits like D flip-flop, T flip-flop and ripple counter has been implemented using the MZIs [5].

The code converters are important to transfer the information in secure way. In optical domain, there is no loss of information when compared to digital system. Implementation of binary to gray code converter and parity device has been done using electro-optic based MZIs [6]. In this paper, we have implemented electrical gray to optical binary converter with the help of MZI through Beam propagation method (BPM) by computer simulation.

This paper is organized as follows. Section 2 describes the construction of electrical gray to optical binary code converter using the electro-optic effect based MZI structure. Section 3 describes the implementation of the device using OptiBPM software. Section 4 describes the results of the proposed device. Finally, conclusion is given in section 5.

Construction Of Electrical Gray To Optical Binary Code Converter Using The Electro-Optic Effect Based Mzi Structure:

In signal processing, the data can be represented in the form of the specific code such as binary, octal, hexadecimal and ASCII character. The binary numbers can be represented of only two bits '0' and '1'. The representation of larger numbers, we required to apply exact code pattern like excess-3 code, gray code and BCD are suitable for the signal processing system. Straightforward purpose of code converters are very essential to improve the performance of signal processing systems and switching activity. Gray to binary code converters are widely used in digital signal processing systems. As counting continues from one place to another consecutive number, their corresponding binary code changes by one bit. Therefore, binary code improves the speed and power consumption performances. Sometimes, it is also used for the encryption as well as decryption. The truth table of the gray code to binary code can be represented.Using the Table 1, we can obtain the expression for gray to binary code bit ([B.sub.3], [B.sub.2], [B.sub.1], and [B.sub.0]).With the help of k-map, and we can obtain the gray to binary code converter circuit diagram as shown in the Fig. 1. It is interesting to implement the gray to binary code conversion techniques using MZI structure. The corresponding layout diagram for electrical gray to optical binary code converter can be represented as shown in the Fig.2. The proposed 4 bit electrical gray to optical binary code converter consists of 7 MZIs structures arranged in the specific manner.

If we connect two MZI in series then lower output ports of the second MZI behaves as a XOR logic gate, where the input binary bit (logic '1' = 6.75 V, logic'0'=0 V) is applied at the second electrode of first and second MZI. The output optical binary code bits can be converted into the electrical domain by applying appropriate photodetectors, then fed into electrode voltage for corresponding MZI.

[FIGURE 1 OMITTED]

III. Implementation of electrical gray to optical binary code converter using opti-bpm software:

The proposed layout for the gray to binary code converters can be verified using OptiBPM software. The OptiBPM is a user-friendly software, which provides the efficient method to construct the wave guiding environment. Its works on the principle of FD (Finite Difference)-BPM.

[FIGURE 3 OMITTED]

The FD-BPM provides the way to simulate the propagation of light through any waveguide medium. Optical electric signal can be tracked at any point as it propagates along a guiding structure. It is obvious that, optical waveguides are the basic unit in order to perform guiding, coupling, splitting, multiplexing and demultiplexing of the optical signals. Now, it is of great interest to implement the optical code-converters such as 4 bit gray to binary code converters.

The Fig. 3 represents the Opti-BPM implemented layout diagram of 4 bit electrical gray to optical binary code converters. The layout comprises of 7 different MZI. The CW (continuous wave) optical signal is applied at the upper input port of the MZI1, MZI3, MZI5 and MZI7. The output optical binary bits [B.sub.3], [B.sub.2] and [B.sub.1] can be given as input electrode voltage for MZI5, MZI3 and MZI1. Before that, the optical binary outputs are converted into electrical domain by proper photodetector and amplifier. The output bit of B1 and the input bit of G0 is applied at the second electrode of MZI1 and MZI2, respectively. The input and output bits are applied in the form of the electrode voltages, in which logic '1'and logic'0' is represented in the form of the 6.75 V and 0 V, respectively. In the same way, [B.sub.2] and G1 is applied as the electrode voltage at the second electrode of MZI3 and MZI4, respectively. Likewise, the bit B3 and G2 serves as the electrode voltage for the MZI5 and MZI6. Finally, the bit [G.sub.3] is also applied to the second electrode of the MZI7. The proposed arrangement of the 7 MZIs accepts the 4 bit gray input and provides the optical binary code corresponding to the electrical binary input bits [G.sub.3][G.sub.2][G.sub.1][G.sub.0]. The appropriate arrangement of MZIs as shown in the Fig. 3, provides the optical binary code [B.sub.0], [B.sub.1], [B.sub.2] and [B.sub.3] at lower output port of MZI2, MZI4, MZI6 and upper output port of MZI7, respectively.

IV. Results of the proposed device:

Figures 4 & 5 indicates the simulation result of proposed 4 bit electrical gray to optical binary code converters for the input bit sequences [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 0110 and [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 0110, respectively. The input bit sequence [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 0110 is applied in the form of the electrode voltages across the specified electrode of MZI2, MZI4, MZI6 and MZI7. The output sequence [B.sub.3], [B.sub.2] and [B.sub.1] are applied in the form of the electrode voltage across the electrode of MZI5, MZI3, and MZIj in order to get the corresponding binary code. We can observe the substantial output signal at the specified output ports of MZIs, which provides the suitable simulation result for the optical binary code converters. The Fig. 4, shows that the binary code can be obtained as [B.sub.3][B.sub.2][B.sub.1][B.sub.0] [right arrow] 0100.

[FIGURE 3 OMITTED]

Similarly, the proposed structure provides the appropriate result for the electrical gray input sequence [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 1110. Based on the optical signal obtained at the different output ports indicated for the proposed device, we can observe the optical binary code as [B.sub.3][B.sub.2][B.sub.1][B.sub.0] [right arrow] 1011 in Fig. 5. The obtained result using the OptiBPM simulation result can be verified using the Table 1. Likewise, the device provides the proper results for the all other input bit sequences.

Figures 6 &7 represents the MATLAB simulation result for the proposed devices. In Fig. 6 the first row represents the input gray bit pattern [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 1110. The corresponding binary code pattern can be shown in the second row as [B.sub.3][B.sub.2][B.sub.1][B.sub.0] [right arrow] 1011. In the same way, the result for the input bit pattern [G.sub.3][G.sub.2][G.sub.1][G.sub.0] [right arrow] 1110 by the first row and corresponding binary code pattern [B.sub.3][B.sub.2][B.sub.1][B.sub.0] [right arrow] 1011 is represented by the second row of Fig. 7. Also, the results can be verified by the truth table represented in the Table l. The proposed device describes the efficient techniques to convert the 4 bit gray input signal into the corresponding 4 bit binary code conversion in the optical domain. Hence, implementation of electrical gray to optical binary code converter can able to improve the performance of the switching devices by improving the switching speed. Implementation of digital device in optical domain makes the system more realizable. Code converters can able to improve the performances of the encryption and decryption techniques using the optically implemented mechanism.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Conclusions:

The efficient method to implement the electrical gray to optical binary code converter is discussed with the suitable analysis are carried out by Beam Propagation Method and relevant results are verified through MATLAB simulation. The discussed scheme as well as optical combinational and sequential system can be the stepping stone in the field of fast communication, secure information transformation and switching systems.

ACKNOWLEDGMENT

The one of the author would like to thank Dr. A. Sivanantha Raja and Assist. Prof. S. Selvendran, ACCET, Anna University, Tamilnadu, India for encouragement and support during the present project work. The one of the author would also like to thank Ms. N. Hemadevi for support during the preparation of this work. The author also thank the anonymous reviewers for their constructive suggestions.

REFERENCES

[1.] Kumar, S., S.K. Raghuwanshi, A. Kumar, 2013. Implementation of optical switches using Mach-Zehnder interferometer. Opt. Eng. 52(9): 097106(1)-097106(9).

[2.] Kumar, A., S. Kumar, S.K. Raghuwanshi, 2014a. Implementation of full-adder and full-subtractor based on electro-optic effect in Mach-Zehnder interferometers. Opt. Commun. 324: 93-107.

[3.] Kumar, A., S. Kumar, S.K. Raghuwanshi, 2014b. Implementation of XOR/XNOR and AND logic gates by using Mach-Zehnder interferometers. Optik 125: 5764-5767.

[4.] Raghuwanshi, S.K., A. Kumar, S. Kumar, 2013. 1 x 4 signal router using three Mach-Zehnder interferometers. Opt. Eng. 52(3): 035002(1)-035002(9).

[5.] Raghuwanshi, S.K., A. Kumar and N.K. Chen, 2014. Implementation of sequential logic circuits using the Mach Zehnder interferometer structure based on electro-optic effect. Opt. Commun. 333: 193-208.

[6.] Kumar, S., K. Raghuwanshi, 2014. Implementation of optical gray code converter and even parity checker using the electro-optic effect in the Mach-Zehnder interferometer. Opt Quant Electron.

(1) Muppidathi@saravanan.A and (2) Sivanantha raja. A, Selvendran. S

(1) Department of ECE Alagappa Chettiar College of Engineering & Technology Karaikudi, India.

(2) Department of ECE Alagappa Chettiar College of Engineering & Technology Karaikudi, India.

Received 25 February 2016; Accepted 10 April 2016; Available 15 April 2016

Address For Correspondence: Muppidathi@saravanan.A., Department of ECE Alagappa Chettiar College of Engineering & T echnology Karaikudi, India.

E-mail: Muppidathi12@gmail.com
Table 1: Truth Table Of Gray To Binary Code Converter

Gray Code

[G.sub.3]   [G.sub.2]   [G.sub.1]   [G.sub.0]

0           0           0           0
0           0           0           1
0           0           1           0
0           0           1           1
0           1           0           0
0           1           0           1
0           1           1           0
0           1           1           1
1           0           0           0
1           0           0           1
1           0           1           0
1           0           1           1
1           1           0           0
1           1           0           1
1           1           1           0
1           1           1           1

Binary Code

[B.sub.3]   [B.sub.2]   [B.sub.1]   [B.sub.0]

0           0           0           0
0           0           0           1
0           0           1           1
0           0           1           0
0           1           1           1
0           1           1           0
0           1           0           0
0           1           0           1
1           1           1           1
1           1           1           0
1           1           0           0
1           1           0           1
1           0           0           0
1           0           0           1
1           0           1           1
1           0           1           0
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Article Details
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Author:Muppidathi@saravanan.A; Raja, A. Sivanantha; Selvendran, S.
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Date:Apr 1, 2016
Words:2130
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