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International Journal of Science, Engineering and Technology Research (IJSETR) Volume 1, Issue 1, July 2012 All-Optical Logic Gates (AND, OR, XOR) at 10Gbps by using a single Semiconductor Optical Amplifier Chaw Chaw Abstract- All-optical logic gates (AND, OR and XOR) are described at 10 Gb/s using the single semiconductor optical amplifier and several optical Gaussian band pass filter. These logic gates are illustrated in the same power setting but different bandwidth and offset spacing. The cross phase modulation method of semiconductor optical amplifier is used to produce the optical logic gates of the system. All-optical logic gates (AND, OR, XOR) are demonstrated with 0.4dB, 1.2dB and 2.1dB power penalty at 10-9 BER in the same power. Both data signals have a pulse width of 20ps with peak power of 2mW and probe power of 0.1mW is modulated at 10 Gb/s. The bit error rate, Q factor and power penalty are measured for all-optical logic gates. The Q factor is near approximately 6. integration and low power consumption. Two inputs logic gates (AND, OR, XOR) based on single SOA and several optical band pass filters. Two data signals and a probe signal are injected into the SOA at the same time to improve cross phase modulation (XPM) effects. The probe spectrum will be broadened, and designed optical filters are used to filter out different frequency components, which contain different logic output, such as logic (AND, OR, XOR). The bit error rate (BER), Q factors and power penalty are measured for all-optical logic gates. II. SEMICONDUCTOR OPTICAL AMPLIFIER Index Terms—Semiconductor Optical Amplifier, All-optical logic gates, Cross phase modulation, Band pass filter I. INTRODUCTION In the next communications networks, optical explanations to logic applications are expected to present an alternative to current electronic signal processing because of quicker response [1]. The optical logic functionalities in the networks are very simple, i.e. consisting of very few Boolean logic gates. To date many techniques have been illustrated to understand various logic functions (AND, OR, XOR) in optical communication system [2, 3]. Logic gates can enable many improved functions such as all-optical bit pattern recognition [4], all-optical bit-error rate monitoring [5], all-optical packet address and payload separation [6], all-optical label swapping [7] and signal regeneration, addressing, header recognition, data encoding and encryption [8]. All-optical logic device can be produced by the three types of materials such as the nonlinearity based on fibers, wavelength conversion based on a semiconductor optical amplifier and optical waveguides. All of them, the logic gates are produced by using the semiconductor optical amplifier have the more advantages of compactness, monolithic Manuscript received April 30, 2014. Chaw Chaw, Department of Electronic Engineering, and Mandalay Technological University (e-mail: [email protected]). Mandalay, Myanmar. Semiconductor optical amplifiers (SOA) are the key element for the all-optical signal processing applications studied and proposed in this system. The optical signals in SOA is classified via gain and phase change. SOA based non-linear effects: cross gain or phase modulation (XGM, XPM); cross polarization rotation (XPR); and four-wave mixing (FWM). III. CROSS PHASE MODULATION IN SOA Cross phase modulation as the using wavelength converter present more advantages when compared to other schemes: high conversion efficiency and output extinction ration; different techniques can be applied to permit conversion after the SOA temporal response; and the output signal information is logically non-inverted. In a single SOA, the many refractive index change occurs at the wavelength the SOA gain is maximized. Since the changes in the refractive index lead to the desired phase changes which cause cross phase modulation, the maximum gain wavelength is usually chosen to be the operating wavelength of technique relying on such non-linear effect. The frequency of a probe signal at the SOA output is achieved when a pulse is propagated at a different wavelength. When the input signal is at constant power level (either high or low power), the CW probe signal wavelength is unchanged. For the leading edged of an optical pulse, the pump signal shifts to upper wavelengths (a red-wavelength). The trailing edges of the optical pulse occurs a blue wavelength. Continuous wave (CW) probe wavelength shifts to lower value. And so, the probe spectrum is broadened. Nonlinear refractive index seen by one wave depends on the intensity of the other wave as 1 All Rights Reserved © 2012 IJSETR International Journal of Science, Engineering and Technology Research (IJSETR) Volume 1, Issue 1, July 2012 Δn NL = n2 (|A1|2+b|A2|2) Total nonlinear phase shift in a fiber length L ϕNL= (2ПL/λ)n2 [I1(t)+bI2(t)] An optical beam changes its own phase and other phase Nonlinear effect of XPM causes among overlapping optical pulses The output is high only when one or both of the data inputs are at logic high and the output logic is low when both the inputs are low in the OR operation. When both the data inputs are high and one input is high, the modulated probe will receive the red-shift in the strong saturation regime. The band pass filter can be applied to select the red-shift in the strong saturation regime. And so, an OR gate is understood. The output is high when both the inputs are not the same and the output is low when both the inputs are the same in the XOR operation. When one control pulse is high the modulated probe will receive the weaker red-shift. The band pass filter can be applied to select a weaker red-shift caused by one control pulse. And so, an XOR gate is understood. Fig.1. Operation principle of the proposed system IV. OPERATION PRINCIPLE OF THE PROPOSED SYSTEM A probe (continuous wave, CW) and two modulated optical return-to-zero (RZ) control signals (pulsed) are induced into the SOA. The control signals (Data1 and Data2) might be the same wavelength with the different wavelength CW probe. The falling edge of the probe is changed in the SOA as the longer wavelength (red-shift), while the rising edge is changed into shorter wavelength (blue-shift) because of non-linear effect of cross phase modulation method. And so, the probe wavelength spectrum is broadened. As the control pulses produce red-shift for the probe light, an optical filter can be applied to select the red-shift spectrum of the probe light, so that the probe can only pass through the optical filter when the control signal is present. All-optical wavelength conversion at 10 Gbps has been illustrated. The amount of the injected red-shift can be controlled by the power of the level input light (Data1, Data2 and probe). The different logic functions can be understood by adjusting the power levels and the filter centre wavelength. When both the data inputs are high, the output logic is high and when one or both the pulses are low, the output logic is zero in the AND operation. When both the data inputs are high, the modulated probe will receive a much stronger red-shift. The band pass filter is used to select a stronger red-shift caused by two control pulses. And so, an AND gate is understood. 2 All Rights Reserved © 2012 IJSETR Fig. 2 .Simulation model for all-optical logic gates (AND, OR, XOR) in the same input signal powers V. RESULT AND DISCUSSION (a) (b) International Journal of Science, Engineering and Technology Research (IJSETR) Volume 1, Issue 1, July 2012 only when one or both of the data inputs are at logic high and the output logic is low when both the inputs are low in the OR gate operation (d) The output is high when both the input signals are not the same and the output is low when both the input signals are the same in the XOR gate operation (e) When both the data input signals are high, the output logic is high and when one or both the pulses are low, the output logic (c) is zero in the AND operation Logic PCW (mW) P Data (mW) Offsets Bandwidth of BPF (GHZ) AND 0.1 2 1.7 40 OR 0.1 2 0.7 50 XOR 0.1 2 0.3 20 (d) Fig.3. Output optical spectra (a) the output spectrum of the probe signal before BPF, (b)-(d) are the output spectra when the optical band pass filter has a detuning of 0.3nm, 0.7nm, and 1.7nm for the same input signal powers The output spectrum of the probe signal before optical band pass filter is shown in fig. 3. (a). When the optical Gaussian band pass filter is used to select the red-shift at the offset value of o.3nm and the bandwidth of 20GHZ, the best logic XOR gate is achieved in fig. 3. (b). If the optical Gaussian band pass filter selects a red-shift at the offset value of 0.7nm and the bandwidth of 50GHZ, the best logic OR gate is realized in fig. 3. (c). When the optical band pass filter is applied to select a red-shift at the offset value 0f 1.7nm and the bandwidth of 40GHZ in fig.3. (d). Table.1. Parameters for all-optical logic gates (AND, OR, XOR) in the same input signal powers This table is shown as the parameters for all-optical logic gates (AND, OR, XOR) at the same input power setting of the two input signal powers and the CW probe power but different bandwidth and offset spacing by using a single semiconductor optical amplifier and several optical band pass filters. The XOR gate bandwidth is narrow and the time waveform is wide. 2 Data 1 0 (a) 2 Optical Power (mW) Data 2 0 T (b) (a) (b) 60 OR 0 (c) 45 XOR 0 (d) 3 AND (c) (d) (e) 0 2 0 5 8 11 (e) Time(ns) Fig. 4. Simulation results for two- input logic gates, (a) and (b) are input data signals, (c)-(e) are logic OR, XOR and AND gates for the same input signal powers. The simulation results of two-input logic gates are shown as the bit sequences in Fig4 (a) and (b). The time output waveform by the optical time domain (c) The output is high Fig. 5. Eye patterns measured for the RZ format: (a) back-to-back 1, (b) back-to-back 2, (c) XOR gate, (d) OR gate(e) AND gate at in the same power setting. The eye-diagrams show the BER pattern at the same average power of -22.369dBm. Fig. 5. (a) and (b) are the eye patterns of two inputs data signal. The output eye patterns of(c) XOR gate (d) OR gate and AND gate are shown. 3 All Rights Reserved © 2012 IJSETR International Journal of Science, Engineering and Technology Research (IJSETR) Volume 1, Issue 1, July 2012 signal and probe are 1550nm and 1560nm. To improve cross phase modulation effect, the SOA is biased at 500mA. Understanding of the all-optical logic gates will provide not only increased speed and capacity telecommunication systems, but also various applications including optical packet switching, add/drop, decision making, bit extraction, and many other optical applications system. ACKNOWLEDGMENT The author would like to express sincere appreciation to the Rector of Mandalay Technological University for kind Permission to prepare for this journal. The author would also like to give special thanks to my supervisor and all teachers in EC Department and all who willingly helped the author throughout the preparation of the journal. This journal is dedicated to the author’s parents for continual and full support on all requirements and moral encouragement. REFERENCES [1] Fig. 6. BER measurement for all-optical logic gates (AND, OR, XOR) for the same input signal powers AND gate operation is the best result in the BER measurements for all-optical logic gates (AND, OR, XOR) based on single SOA and BPF at the10-9 but it is not good beyond at the 10-12. All-optical logic gates (AND, OR, XOR) are demonstrated with 0.4dB, 1.2dB and 2.1dB power penalty at 10-9 BER in the same input signal power. BER curve are measured back to back1, back to back2, XOR gate, OR gate and AND gate by placing at the same average power. If the input signal is received at the output with the little power, the receiver sensitivity is good. V. CONCLUSION All-optical logic gates (AND, OR, XOR) are described at 10 Gb/s using the single semiconductor optical amplifier and several optical Gaussian band pass filter. All-optical logic gates (AND, OR, XOR) capable of working with 10Gbps RZ modulated data streams based on cross phase modulation effect of the single SOA in the same power setting but different bandwidth and offset spacing. The BER for all-optical logic gates is produced in the same power setting, an AND gate is the best logic gate at10-9 but beyond 10-12 it is not good. All-optical logic gates (AND, OR, XOR) are demonstrated with 0.4dB, 1.2dB and 2.1dB power penalty at 10-9 BER in the same power setting but different bandwidth and offset spacing. Both data signals have a pulse width of 20ps with peak power of 2mW and probe power of 0.1mW is modulated at 10 Gb/s. The bit error rate, Q factor and power penalty are measured for all-optical logic gates. The Q factor is near approximately 6. The wavelengths of two inputs data 4 All Rights Reserved © 2012 IJSETR [2] [3] [4] [5] [6] [7] [8] K. Vahala, R. Paiella, and G. Hunziker, "Ultrafast WDM logic," J. Sel.Top. Quantum Electron. 3, 698-701 (1997) T. Houbavlis, K. Zeros, A. Hatziefremidis, H. Avramopoulos, L.Occhi, G. Guekos, S. Hansmann, H.Burkhard, and R. Dall'Ara, "10Gbit/s all-optical Boolean XOR with SOA fiber Signac gate," Electron. Lett.35, 1650-1652 (1999). X. Zhang, Y. Wang, J. Sun, D. Liu, and D. Huang, "All-optical AND gate at 10 Gbit/s based on cascaded single-port-couple SOAs,"Opt.Express12,361366(2004),http://www.opticsinfobase.org/ oe/abstract.cfm?URI=oe-12-3-361. Stubkjaer, K.E.: ‘Semiconductor optical amplifier-based all optical gates for high-speed optical processing’IEEE Journal on selected topics in quantumelectronics, 2000, 6, (6), pp.1428-1435. Martinez, J.M., Ramos, F., Marti, J.: ‘All-optical packet header processor based on cascaded SOA-MZIs’, Electronics letters, 2004, 40,(14), pp.894-895 Chan, L.Y., Qureshi, K.K., Wai, P.K.A., Moses, B., Lui, L.F.K.,Tam, H. Tam, H.Y.,Demokan, M.S.: ‘All-optical bit-error monitoring system using cascade dinverted wavelength converter and optical NOR gate’, IEEE photonic technology letters, 2003, 15, (4), pp.593-595 Bintjas, C., Pleros, N., Yiannopoulos, K., Theophilopoulos, G., Kalyvas, M., Avramopoulos, H., Guekos, G.: ‘All-optical packet address and payload separation’, IEEE photonic technology letters, 2002, 14, (12), pp.1728-1730. G. P. Agrawal, Fiber-Optic Communication Systems, 3rd ed. (Wiley, (2002) 1. Chaw Chaw received her Bachelor of Technology (B.Tech) degree in 2006 and Bachelor of Engineering (B.E) degree in 2007 in Electronic Engineering from Monywa Technological University, Myanmar. She is now Master of Engineering (M.E) student in Mandalay Technological University, Myanmar. Her research interests include optical fiber communications and digital communications.