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Analytical and simulative studies on optical NOR and controlled NOR logic gates with semiconductor optical amplifier
Optik 125 (2014) 1333–1336
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Analytical and simulative studies on optical NOR and controlled NOR logic gates with semiconductor optical amplifier Partha Pratim Sarkar a,∗ , Biplab Satpati b , Sourangshu Mukhopadhyay c a b c
Department of ECE, UIT, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India Department of EE, UIT, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India Department of Physics, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India
a r t i c l e
i n f o
Article history: Received 4 October 2012 Accepted 5 August 2013
Keywords: Non-linear optics reflected semiconductor optical amplifier add/drop multiplexer optical gates simulink
a b s t r a c t Semiconductor optical amplifier (SOA) is used for different successful frequency based switching operations. In this paper the authors describe the simulation study of the performances of SOA in various optical switches like frequency conversion, add-drop multiplexer and frequency encoded optical NOR gate, which is one the most important gates in logic family as it is known as one of the universal logic gates. Again, the controlled optical NOR logic operation with semiconductor optical amplifier is also proposed in this paper. © 2013 Elsevier GmbH. All rights reserved.
1. Introduction
2. Semiconductor optical amplifier based switching
To overcome the speed related problems in electronic or optoelectronic data processing system, all optical data processing are the most promising alternative and successful replacement as light has the inherent character of parallelism [1,2]. Again semiconductor optical amplifier (SOA) is established as a very promising optical device for conducting many all-optical logical operations [3–5]. Intensity encoding [6–8] may produce a bit error problem. If frequency of light is used in place of intensity encoded bit representation problem may be overcome. To use the frequency encoding/decoding technique [9–13] two different states of information can be represented by two different frequencies at the time of data computation. Generally the presence of a specific frequency of light is treated as ‘1’ logic state and other specific one represents as‘0’. Here these ‘1’ and ‘0’ states can be replaced by any suitable value of optical frequencies in C-band, which remain unaltered and unchanged under reflection, refraction and absorption [14,15], etc. Here in this paper the authors describe a simulation study with mat lab programming to verify several optical frequency encoded switching operations of SOA as well as the function of frequency encoded optical NOR gate. The simulative result is also provided in this paper. Here the concept of controlled optical NOR logic operation is first time proposed by the active use of SOA.
Here in this communication the authors use the cross gain modulation character of SOA. A weak probe beam light of wavelength say, 1 = 1540 nm with signal power say −5 dBm and a strong pump beam of wavelength 2 = 1550 nm with signal power say 8 dBm are injected to the input terminals of a properly biased SOA. It is known that in case of a wavelength converter (WC), the strong pump beam transfer its total power to the weak probe beam and then the weak probe beam becomes stronger and comes out to the output, so that the SOA acts as proper wavelength converter. These schemes with simulated results are shown in Fig. 1(a)–(c). In Fig. 1(a) the block diagram of a wavelength converter (WC) is shown, where as in Fig. 1(b) to make it clearer the power and wavelength of inputs and outputs are shown in different channels, where in presence of probe beam and pump beam at the input terminals with their wavelength and power, respectively. At the output it provides the wavelength of probe beam (1540 nm) and power of pump beam (8 dBm). Again optical ADD/DROP multiplexer is a frequency selecting network. It is tuned with a particular biasing current and it reflects a particular frequency of light through it and passes all the rest frequencies of light. The simulated results of ADM with proper output are shown in Fig. 2(a)–(c). In Fig. 2(a) the block diagram of an ADD/DROP multiplexer is shown and in Fig. 2(b) for better understanding frequencies and power of input and output of pump and probe beam are shown through channels in different way. In Fig. 2(b) it depicts that a properly biased (here biasing current say 162 mA is considered as select beam “1”, i.e. 2 ) ADD/DROP multiplexer (ADM), where at the input terminal two
∗ Corresponding author. E-mail addresses: [email protected] (P.P. Sarkar), [email protected] (B. Satpati), [email protected] (S. Mukhopadhyay). 0030-4026/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2013.08.003
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Fig. 1. (a) The block diagram of wavelength converter (WC). (b) The functional model of (WC) block, where power and wavelength are shown in different channels.
Fig. 3. (a) Block diagram of frequency encoded optical NOR gate. (b) Functional model of frequency encoded NOR gate. (c) Truth table of optical NOR gate. (d) Simulated result of frequency encoded optical NOR gate.
different frequencies A and B, respectively, say (A = frequency of 2 × 1014 Hz, say, 2 (2 ) with power = 5 dBm and B = frequency of 1.93 × 1014 Hz say, 1 (1 ), with power = 7 dBm) are applied. Then the ADM reflects the frequency as well as power of A and passes other frequency and power. That is at the reflected terminal of ADM, it emits the frequency and power of A (i.e. frequency = 2 × 1014 Hz and power = 5 dBm) but blocks frequency and power of B (i.e. frequency of 1.93 × 1014 Hz with power = 7 dBm). Different incident happens if the biasing current changes which is shown in fig. 2(c), here, as the biasing current beam shifts from ‘1’ to ‘0’, the ADM reflects the frequency as well as power of B and blocks frequency and power of A. 3. Scheme of realization of frequency encoded optical NOR gate To implement any optical logical operation optical logic gates are considered as the basic building blocks. Here NOR gate is one of the most important basic unit as it is established as a universal logic. For developing the frequency encoded NOR gate, some ADD/DROP multiplexers, wavelength converters (WC)/reflected semiconductor optical amplifier (RSOA), beam splitters (BS) and mirrors (M) are needed. These different blocks are connected such a way that the final model provides the suitable output, which satisfies the truth table of frequency encoded optical NOR gate. This block diagram of NOR gate is shown in Fig. 3(a) and its equivalent functional model with the help of simulink software is presented at Fig. 3(b). To realize the operation of optical NOR gate, here, at the two input terminals, i.e. at ‘A’ or ‘B’ terminal either a beam of 1 frequency corresponding to the wavelength 1 = 1540 nm (in functional model 1 frequency is considered as 1.948 × 1014 Hz with power −5 dBm) or 2 frequency corresponding to the wavelength 2 = 1550 nm (in mathematical model 2 frequency is considered as 1.9355 × 1014 Hz with the power 8 dBm) of light is used. Fig. 2. (a) The block diagram of a ADD/drop multiplexer. (b) The functional model of ADM for a specific biasing current (here considered as ‘1’), where frequency and power of beam A is transmitted and frequency and power of beam B is blocked. (c) The functional model of ADM with other value of biasing current (here considered as ‘0’), where at the output frequency and power of beam B is transmitted and the frequency and power of beam A is blocked.
4. Principle operation of optical NOR gate In case of NOR logic, at first 2 frequency of light beams are applied in both of the input terminals ‘A’ and ‘B’. So the 2 is reflected by both the ADM1 and ADM2 respectively. For terminal ‘A’
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Fig. 4. (a–d) Simulated functional blocks for different combinations of inputs and corresponding their outputs of frequency encoded optical NOR gate.
this 2 frequency is served as the strong pump beam to the RSOA4 and as the constant weak probe beam of 1 frequency of light beam is present here, so a beam of 1 frequency is obtained from the output of RSOA4 and is transmitted to ADM3 , which passes the beam to the output terminal. So at the ‘Y’ output end a 1 frequency of light beam is obtained. Form terminal ‘B’, the reflected 2 frequency of light beam is given to RSOA1 as pump beam, but due to the absence of probe beam, RSOA1 cannot take part under such condition. Now if ‘A’ = 2 and ‘B’ = 1 then ADM1 reflects the light beam to RSOA4 as strong pump beam. So again 1 frequency is obtained from RSOA4 and this 1 frequency of light beam is passed by the ADM3 and is provided at the output as ‘Y’ = 1 . Again, as the probe beam is absent to RSOA3 , so the transmitted 1 light beam from ADM2 (as ‘B’ = 1 ) does not take part. Again, if, ‘A’ = 1 and ‘B’ = 2 , the ADM1 passes the 1 frequency of light beam as the weak probe beam to the RSOA1 and after transmitting form ADM2 the 2 frequency of light beam comes as the strong pump beam to the RSOA1 . So 1 is obtained from RSOA1 and passed to the ‘Y’ terminal of ADM3 , i.e. again ‘Y’ = 1 . Finally if ‘A’ = 1 and ‘B’ = 1 , the transmitted 1 frequency of light beam after divided by the beam splitter is presented as the strong pump beam to the RSOA2 . As the constant probe beam of 2 frequency of light beam is presented here, so 2 frequency of light beam is obtained from RSOA2 and is given as the weak probe beam to the RSOA3 after reducing the intensity of the 2 light beam. Now, as ‘B’ = 1 , so, ADM2 transmits the 1 frequency of light beam and is given as the strong pump beam to the RSOA3 . Here, as both the beams are present, so 2 frequency of light beam is obtained as the output of RSOA3 , this 2 frequency of light beam is reflected by ADM3 as it is tuned by the biasing frequency 2 . So finally the 2 frequency of light beam is collected by the circulator C3 and transmitted at the output terminal ‘Y’, as ‘Y’ = 2 . Thus, if 2 frequency of light beam is considered as binary ‘1’ and 1 frequency of light beam is considered as binary ‘0’, then it can be shown when ‘A’ = 2 and ‘B’ = 2 ; ‘Y’ = ‘0’ which is shown in functional model Fig. 4(a), again, if, ‘A’ = 2 and ‘B’ = 1 ; ‘Y’ = ‘0’, which is shown in functional model 4(b), when ‘A’ = 1 and ‘B’ = 2 ; ‘Y’ = ‘0’, it is shown in functional model 4(c), and finally if ‘A’ = 1 and ‘B’ = 1 ; ‘Y’ = ‘1’, which is shown in functional model 4(d). Again in the graph 3(d) it is shown that output is ‘1’ when both the inputs are ‘0’, if, any one of the input is ‘1’, the output becomes ‘0’, which satisfies the truth table of NOR gate. So, both proposed frequency encoded optical logic gate as well as simulative functional model supports the truth table of universal NOR gate. 5. A new scheme for developing controlled optical NOR logic gate with SOA Here, authors suggested a new scheme for developing controlled optical NOR logic gate with semiconductor optical amplifier. In this model shown in Fig. 5(a), a ADM is taken which is biased with a biasing current 3 , so, this ADM reflects only 3 wavelength based optical frequency. This optical beam is considered as the pump beam input to the two RSOA simultaniously. Now, another input of the both RSOA, respectively, are considered as the probe beam.
Fig. 5. (a) Block diagram of controlled optical NOR gate. (b) Truth table of controlled optical NOR gate.
According to the principle of RSOA, if both pump and probe beam are present, it provides the frequency of the probe beam at the output. So, either, 1 or 2 are uesd at the input of the probe beam of the both RSOA, they provide the same optical beam at the output. Now these output act as the input of the controlled optical NOR gate, and this gate provides the output maintaining the truth table of Fig. 5(b). So, from here, we may conclude that if, pump beam in form of optical beam, 3 is present, then only the optical NOR gate actives. Otherwise the system does not provide any output. So this NOR gate works as the controlled optical NOR gate. 6. Conclusion The output of an all optical frequency encoded superfast NOR logic operation is verified by simulink software. The advantages of frequency encoding operation are fully exploited here. The simulative result of the optical NOR logic gate completely agrees the NOR logic truth table, which supports the operation of NOR logic gate with SOA. Also this proposed functional model may provide a high signal to noise ratio. The originality of this contribution is verification of some important semi conductor optical amplifier based switches by proper computer simulation, where the frequency encoding/decoding technique is incorporated. Again, NOR logic operation is considered as an universal logic, so we have verified operation of frequency encoded NOR logic gate by a computer simulation. The respective algorithm of the concerned software for verification of the frequency encoded switches and the NOR operation are also developed by us. One may implement the simulative software programming for other optical operations like flip-flops, multivibrators, latch, etc. by using the above simulink software. The result of the output agrees the faithful and reliable operation of optical NOR gate with the optical switches. Again, in this paper the authors have proposed a concept of controlled optical NOR logic gate by SOA. The operation of this gate can also supported by simulation using the software (MATLAB) of the SOA based switches. References [1] A.K. Das, S. Mukhopadhyay, General approach of spatial input encoding for multiplexing and demultiplexing, Opt. Eng. 43 (1) (2004) 126–131. [2] K. Roy Chowdhury, S. Mukhopadhyay, Binary optical arithmetic operation scheme with tree architecture by proper accommodation of optical nonlinear materials, Opt. Eng. 43 (1) (2004) 132–136. [3] M.J. Connelly, Semiconductor Optical Amplifiers, Kluwer Academic publishers, New York, 2004. [4] S. Dutta, S. Mukhopadhyay, An all optical approach of frequency encoded NOT based latch using semiconductor optical amplifier, Opt. Soc. India, J. Opt. 39 (1) (2009) 39–45. [5] S. Dutta, S. Mukhopadhyay, Alternating approach of implementing frequency encoded all-optical logic gates and flip-flop using semiconductor optical amplifier, Optik-International Journal for Light and Electron Optics 122 (12) (2011) 1088–1094. [6] T. Yatagai, Optical space-variant logic-gate array based on spatial encoding technique, Opt. Lett. 11 (4) (1986) 260–262.
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[7] L.Q. Guo, M.J. Connelly, A poincare approach to investigate nonlinear polarization rotation in semiconductor optical amplifiers and its applications to all optical wavelength conversion, Proc. SPIE 6783 (2007), Article id: 678325 (1–5). [8] S. Dutta, S. Mukhopadhyay, All optical frequency encoding method for converting a decimal number to its equivalent binary number using tree architecture, in: Presented and Published in the Proceedings of International Conference of Optics and Photonics (ICOP-2009) in Chandigar, 31 October–2 November, 2009. [9] S.K. Garai, S. Mukhopadhyay, A novel method of developing all-optical frequency encoded memory unit exploiting nonlinear switching character of semiconductor optical amplifier, Opt. Laser Technol. 42 (7) (2010) 1122– 1127. [10] S.K. Garai, S. Mukhopadhyay, A method of optical implementation of frequency encoded different logic operations using second harmonic & difference frequency generation techniques in non-linear material, Optik 121 (April (8)) (2010) 715–721.
[11] S.K. Garai, S. Mukhopadhyay, All-optical frequency encoded binary half subtractor using periodically poled lithium niobate waveguide and reflecting semiconductor optical amplifier, Optics Photonics. Letters 3 (1) (2010) 15–22. [12] D. Samanta, S. Mukhopadhyay, A method of maintaining the intensity level of a polarization encoded light signal, J. Phys. Sci. (Vidyasagar University) 11 (2007) 87–91. [13] S.H. Sun, H.Q. Ma, J.J. Han, L.M. Liang, C.Z. Li, Quantum key distribution based on phase encoding in long-distance communication fiber, Opt. Lett. 35 (8) (2010) 1203–1205. [14] Y. Miyoshi, K. Ikeda, H. Tobioka, T. Inoue, S. Namiki, K. Kitayama, Ultrafast alloptical logic gate using a nonlinear optical loop mirror based multi-periodic transfer function, Opt. Expr. 16 (4) (2008) 2570–2577. [15] J.N. Roy, A.K. Maiti, D. Samanta, S. Mukhopadhyay, Tree-net architecture for integrated all-optical arithmetic operations and data comparison scheme with optical nonlinear material, Opt. Switch. Netw. 4 (3–4) (2007) 231–237.
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Analytical and simulative studies on optical NOR and controlled NOR logic gates with semiconductor optical amplifier Partha Pratim Sarkar a,∗ , Biplab Satpati b , Sourangshu Mukhopadhyay c a b c
Department of ECE, UIT, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India Department of EE, UIT, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India Department of Physics, Burdwan University, Golapbag, Burdwan 713104, West Bengal, India
a r t i c l e
i n f o
Article history: Received 4 October 2012 Accepted 5 August 2013
Keywords: Non-linear optics reflected semiconductor optical amplifier add/drop multiplexer optical gates simulink
a b s t r a c t Semiconductor optical amplifier (SOA) is used for different successful frequency based switching operations. In this paper the authors describe the simulation study of the performances of SOA in various optical switches like frequency conversion, add-drop multiplexer and frequency encoded optical NOR gate, which is one the most important gates in logic family as it is known as one of the universal logic gates. Again, the controlled optical NOR logic operation with semiconductor optical amplifier is also proposed in this paper. © 2013 Elsevier GmbH. All rights reserved.
1. Introduction
2. Semiconductor optical amplifier based switching
To overcome the speed related problems in electronic or optoelectronic data processing system, all optical data processing are the most promising alternative and successful replacement as light has the inherent character of parallelism [1,2]. Again semiconductor optical amplifier (SOA) is established as a very promising optical device for conducting many all-optical logical operations [3–5]. Intensity encoding [6–8] may produce a bit error problem. If frequency of light is used in place of intensity encoded bit representation problem may be overcome. To use the frequency encoding/decoding technique [9–13] two different states of information can be represented by two different frequencies at the time of data computation. Generally the presence of a specific frequency of light is treated as ‘1’ logic state and other specific one represents as‘0’. Here these ‘1’ and ‘0’ states can be replaced by any suitable value of optical frequencies in C-band, which remain unaltered and unchanged under reflection, refraction and absorption [14,15], etc. Here in this paper the authors describe a simulation study with mat lab programming to verify several optical frequency encoded switching operations of SOA as well as the function of frequency encoded optical NOR gate. The simulative result is also provided in this paper. Here the concept of controlled optical NOR logic operation is first time proposed by the active use of SOA.
Here in this communication the authors use the cross gain modulation character of SOA. A weak probe beam light of wavelength say, 1 = 1540 nm with signal power say −5 dBm and a strong pump beam of wavelength 2 = 1550 nm with signal power say 8 dBm are injected to the input terminals of a properly biased SOA. It is known that in case of a wavelength converter (WC), the strong pump beam transfer its total power to the weak probe beam and then the weak probe beam becomes stronger and comes out to the output, so that the SOA acts as proper wavelength converter. These schemes with simulated results are shown in Fig. 1(a)–(c). In Fig. 1(a) the block diagram of a wavelength converter (WC) is shown, where as in Fig. 1(b) to make it clearer the power and wavelength of inputs and outputs are shown in different channels, where in presence of probe beam and pump beam at the input terminals with their wavelength and power, respectively. At the output it provides the wavelength of probe beam (1540 nm) and power of pump beam (8 dBm). Again optical ADD/DROP multiplexer is a frequency selecting network. It is tuned with a particular biasing current and it reflects a particular frequency of light through it and passes all the rest frequencies of light. The simulated results of ADM with proper output are shown in Fig. 2(a)–(c). In Fig. 2(a) the block diagram of an ADD/DROP multiplexer is shown and in Fig. 2(b) for better understanding frequencies and power of input and output of pump and probe beam are shown through channels in different way. In Fig. 2(b) it depicts that a properly biased (here biasing current say 162 mA is considered as select beam “1”, i.e. 2 ) ADD/DROP multiplexer (ADM), where at the input terminal two
∗ Corresponding author. E-mail addresses: [email protected] (P.P. Sarkar), [email protected] (B. Satpati), [email protected] (S. Mukhopadhyay). 0030-4026/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2013.08.003
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Fig. 1. (a) The block diagram of wavelength converter (WC). (b) The functional model of (WC) block, where power and wavelength are shown in different channels.
Fig. 3. (a) Block diagram of frequency encoded optical NOR gate. (b) Functional model of frequency encoded NOR gate. (c) Truth table of optical NOR gate. (d) Simulated result of frequency encoded optical NOR gate.
different frequencies A and B, respectively, say (A = frequency of 2 × 1014 Hz, say, 2 (2 ) with power = 5 dBm and B = frequency of 1.93 × 1014 Hz say, 1 (1 ), with power = 7 dBm) are applied. Then the ADM reflects the frequency as well as power of A and passes other frequency and power. That is at the reflected terminal of ADM, it emits the frequency and power of A (i.e. frequency = 2 × 1014 Hz and power = 5 dBm) but blocks frequency and power of B (i.e. frequency of 1.93 × 1014 Hz with power = 7 dBm). Different incident happens if the biasing current changes which is shown in fig. 2(c), here, as the biasing current beam shifts from ‘1’ to ‘0’, the ADM reflects the frequency as well as power of B and blocks frequency and power of A. 3. Scheme of realization of frequency encoded optical NOR gate To implement any optical logical operation optical logic gates are considered as the basic building blocks. Here NOR gate is one of the most important basic unit as it is established as a universal logic. For developing the frequency encoded NOR gate, some ADD/DROP multiplexers, wavelength converters (WC)/reflected semiconductor optical amplifier (RSOA), beam splitters (BS) and mirrors (M) are needed. These different blocks are connected such a way that the final model provides the suitable output, which satisfies the truth table of frequency encoded optical NOR gate. This block diagram of NOR gate is shown in Fig. 3(a) and its equivalent functional model with the help of simulink software is presented at Fig. 3(b). To realize the operation of optical NOR gate, here, at the two input terminals, i.e. at ‘A’ or ‘B’ terminal either a beam of 1 frequency corresponding to the wavelength 1 = 1540 nm (in functional model 1 frequency is considered as 1.948 × 1014 Hz with power −5 dBm) or 2 frequency corresponding to the wavelength 2 = 1550 nm (in mathematical model 2 frequency is considered as 1.9355 × 1014 Hz with the power 8 dBm) of light is used. Fig. 2. (a) The block diagram of a ADD/drop multiplexer. (b) The functional model of ADM for a specific biasing current (here considered as ‘1’), where frequency and power of beam A is transmitted and frequency and power of beam B is blocked. (c) The functional model of ADM with other value of biasing current (here considered as ‘0’), where at the output frequency and power of beam B is transmitted and the frequency and power of beam A is blocked.
4. Principle operation of optical NOR gate In case of NOR logic, at first 2 frequency of light beams are applied in both of the input terminals ‘A’ and ‘B’. So the 2 is reflected by both the ADM1 and ADM2 respectively. For terminal ‘A’
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Fig. 4. (a–d) Simulated functional blocks for different combinations of inputs and corresponding their outputs of frequency encoded optical NOR gate.
this 2 frequency is served as the strong pump beam to the RSOA4 and as the constant weak probe beam of 1 frequency of light beam is present here, so a beam of 1 frequency is obtained from the output of RSOA4 and is transmitted to ADM3 , which passes the beam to the output terminal. So at the ‘Y’ output end a 1 frequency of light beam is obtained. Form terminal ‘B’, the reflected 2 frequency of light beam is given to RSOA1 as pump beam, but due to the absence of probe beam, RSOA1 cannot take part under such condition. Now if ‘A’ = 2 and ‘B’ = 1 then ADM1 reflects the light beam to RSOA4 as strong pump beam. So again 1 frequency is obtained from RSOA4 and this 1 frequency of light beam is passed by the ADM3 and is provided at the output as ‘Y’ = 1 . Again, as the probe beam is absent to RSOA3 , so the transmitted 1 light beam from ADM2 (as ‘B’ = 1 ) does not take part. Again, if, ‘A’ = 1 and ‘B’ = 2 , the ADM1 passes the 1 frequency of light beam as the weak probe beam to the RSOA1 and after transmitting form ADM2 the 2 frequency of light beam comes as the strong pump beam to the RSOA1 . So 1 is obtained from RSOA1 and passed to the ‘Y’ terminal of ADM3 , i.e. again ‘Y’ = 1 . Finally if ‘A’ = 1 and ‘B’ = 1 , the transmitted 1 frequency of light beam after divided by the beam splitter is presented as the strong pump beam to the RSOA2 . As the constant probe beam of 2 frequency of light beam is presented here, so 2 frequency of light beam is obtained from RSOA2 and is given as the weak probe beam to the RSOA3 after reducing the intensity of the 2 light beam. Now, as ‘B’ = 1 , so, ADM2 transmits the 1 frequency of light beam and is given as the strong pump beam to the RSOA3 . Here, as both the beams are present, so 2 frequency of light beam is obtained as the output of RSOA3 , this 2 frequency of light beam is reflected by ADM3 as it is tuned by the biasing frequency 2 . So finally the 2 frequency of light beam is collected by the circulator C3 and transmitted at the output terminal ‘Y’, as ‘Y’ = 2 . Thus, if 2 frequency of light beam is considered as binary ‘1’ and 1 frequency of light beam is considered as binary ‘0’, then it can be shown when ‘A’ = 2 and ‘B’ = 2 ; ‘Y’ = ‘0’ which is shown in functional model Fig. 4(a), again, if, ‘A’ = 2 and ‘B’ = 1 ; ‘Y’ = ‘0’, which is shown in functional model 4(b), when ‘A’ = 1 and ‘B’ = 2 ; ‘Y’ = ‘0’, it is shown in functional model 4(c), and finally if ‘A’ = 1 and ‘B’ = 1 ; ‘Y’ = ‘1’, which is shown in functional model 4(d). Again in the graph 3(d) it is shown that output is ‘1’ when both the inputs are ‘0’, if, any one of the input is ‘1’, the output becomes ‘0’, which satisfies the truth table of NOR gate. So, both proposed frequency encoded optical logic gate as well as simulative functional model supports the truth table of universal NOR gate. 5. A new scheme for developing controlled optical NOR logic gate with SOA Here, authors suggested a new scheme for developing controlled optical NOR logic gate with semiconductor optical amplifier. In this model shown in Fig. 5(a), a ADM is taken which is biased with a biasing current 3 , so, this ADM reflects only 3 wavelength based optical frequency. This optical beam is considered as the pump beam input to the two RSOA simultaniously. Now, another input of the both RSOA, respectively, are considered as the probe beam.
Fig. 5. (a) Block diagram of controlled optical NOR gate. (b) Truth table of controlled optical NOR gate.
According to the principle of RSOA, if both pump and probe beam are present, it provides the frequency of the probe beam at the output. So, either, 1 or 2 are uesd at the input of the probe beam of the both RSOA, they provide the same optical beam at the output. Now these output act as the input of the controlled optical NOR gate, and this gate provides the output maintaining the truth table of Fig. 5(b). So, from here, we may conclude that if, pump beam in form of optical beam, 3 is present, then only the optical NOR gate actives. Otherwise the system does not provide any output. So this NOR gate works as the controlled optical NOR gate. 6. Conclusion The output of an all optical frequency encoded superfast NOR logic operation is verified by simulink software. The advantages of frequency encoding operation are fully exploited here. The simulative result of the optical NOR logic gate completely agrees the NOR logic truth table, which supports the operation of NOR logic gate with SOA. Also this proposed functional model may provide a high signal to noise ratio. The originality of this contribution is verification of some important semi conductor optical amplifier based switches by proper computer simulation, where the frequency encoding/decoding technique is incorporated. Again, NOR logic operation is considered as an universal logic, so we have verified operation of frequency encoded NOR logic gate by a computer simulation. The respective algorithm of the concerned software for verification of the frequency encoded switches and the NOR operation are also developed by us. One may implement the simulative software programming for other optical operations like flip-flops, multivibrators, latch, etc. by using the above simulink software. The result of the output agrees the faithful and reliable operation of optical NOR gate with the optical switches. Again, in this paper the authors have proposed a concept of controlled optical NOR logic gate by SOA. The operation of this gate can also supported by simulation using the software (MATLAB) of the SOA based switches. References [1] A.K. Das, S. Mukhopadhyay, General approach of spatial input encoding for multiplexing and demultiplexing, Opt. Eng. 43 (1) (2004) 126–131. [2] K. Roy Chowdhury, S. Mukhopadhyay, Binary optical arithmetic operation scheme with tree architecture by proper accommodation of optical nonlinear materials, Opt. Eng. 43 (1) (2004) 132–136. [3] M.J. Connelly, Semiconductor Optical Amplifiers, Kluwer Academic publishers, New York, 2004. [4] S. Dutta, S. Mukhopadhyay, An all optical approach of frequency encoded NOT based latch using semiconductor optical amplifier, Opt. Soc. India, J. Opt. 39 (1) (2009) 39–45. [5] S. Dutta, S. Mukhopadhyay, Alternating approach of implementing frequency encoded all-optical logic gates and flip-flop using semiconductor optical amplifier, Optik-International Journal for Light and Electron Optics 122 (12) (2011) 1088–1094. [6] T. Yatagai, Optical space-variant logic-gate array based on spatial encoding technique, Opt. Lett. 11 (4) (1986) 260–262.
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[7] L.Q. Guo, M.J. Connelly, A poincare approach to investigate nonlinear polarization rotation in semiconductor optical amplifiers and its applications to all optical wavelength conversion, Proc. SPIE 6783 (2007), Article id: 678325 (1–5). [8] S. Dutta, S. Mukhopadhyay, All optical frequency encoding method for converting a decimal number to its equivalent binary number using tree architecture, in: Presented and Published in the Proceedings of International Conference of Optics and Photonics (ICOP-2009) in Chandigar, 31 October–2 November, 2009. [9] S.K. Garai, S. Mukhopadhyay, A novel method of developing all-optical frequency encoded memory unit exploiting nonlinear switching character of semiconductor optical amplifier, Opt. Laser Technol. 42 (7) (2010) 1122– 1127. [10] S.K. Garai, S. Mukhopadhyay, A method of optical implementation of frequency encoded different logic operations using second harmonic & difference frequency generation techniques in non-linear material, Optik 121 (April (8)) (2010) 715–721.
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