HERMITE-GAUSSIAN MODE IN SPATIAL DIVISION MULTIPLEXING OVER FSO SYSTEM UNDER DIFFERENT WEATHER CONDITION BASED ON LINEAR GAUSSIAN FILTER

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 01, January 2019, pp , Article ID: IJMET_10_01_112 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed HERMITE-GAUSSIAN MODE IN SPATIAL DIVISION MULTIPLEXING OVER FSO SYSTEM UNDER DIFFERENT WEATHER CONDITION BASED ON LINEAR GAUSSIAN FILTER Sara Alshwani, 1 Presidency of Kirkuk, Kirkuk University, Iraq Ahmed M. Fakhrudeen, 2Networks Department, College of Computer Science and Information Technology, Kirkuk University, Iraq Mohammed Nasih Ismael 3 Geography Department, College of Arts, Kirkuk University, Iraq Aras Al-Dawoodi 4Computer Science Department, College of Computer Science and Information Technology, Kirkuk University, Iraq Alaan Ghazi School of Human Development & Techno-communication, Universiti Malaysia Perlis, Malaysia. School of Computer and Communication Engineering, Universiti Malaysia Perlis, Malaysia ABSTRACT The wireless telecommunication system of hybrid free-space optics (FSO) utilizes a transmission medium of free space to transmit data at high bit rates. However, it is exposed to various effects of noise in different weather conditions. This paper investigates on compensation for atmospheric turbulence in optical communication systems of 10-channels spatial division multiplexing (SDM) over FSO link under different weather conditions based on linear Gaussian filter (LGF). The performance of a 10-channel transceiver system is evaluated in an SDM-FSO link under the clear sky, haze, and rain weather conditions based on Gaussian filter at the receiver. Furthermore, the simulated system has transmitted 100 Gbit/s up for a distance of 12 km FSO in superbly very clear weather condition. Moreover, it is also transmitted 100 Gbit/s up for a distance of 4.2 km FSO during heavy rain and up to 1.1 km distance editor@iaeme.com

2 Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter FSO during heavy haze. The results show that system capacity is effectively increased with the use of SDM that operate at 1550 nm wavelength. Finally, the validation is conducted based on analyzing eye diagrams, Q-Factor and Bit Error Rates Keywords: Hermite-Gaussian Mode, Few-mode fiber, SDM, linear Gaussian filter. Cite this Article: Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter, International Journal of Mechanical Engineering and Technology, 10(01), 2019, pp INTRODUCTION Free-space optical (FSO) communication system is a growing communication technology, used as an alternate technology where internet service is not a feasible solution. In FSO light signal is sent from the transmitter to the receiver using the air as a transmission medium. FSO systems have several advantages such as, bandwidth scalability, low cost, easy and fast deployment, portability, license-free operation, high transmission security, high bit rates, and full duplex transmission [1, 2]. The wireless telecommunication system of FSO utilizes a transmission medium of free space to transmit optical data at high bit rates. In comparison with the conventional wireless technologies, from its basic development, the technology has been improved remarkably in recent years. FSO system uses a similar optical transceiver, like that of optical communication technology, and it operates through free space, in full-duplex mode. More importantly, its installation can be very swift at a very low cost. However, it is exposed to various effects of noise in different weather conditions [3]. Concurrently, the amount of data that is transmitted keeps increasing. It could be possibly handled by considering several major at the transmitter like minding the modulation techniques [4], suitable light source, estimation of transmitting power levels and wavelength transmission [5]. The demand for bandwidth in support of numerous applications keeps increasing too, over the years [6]. When the bandwidth is expanded, the transmission capacity of the FSO is also accordingly enhanced, which is necessary in the current video-based information dissemination world. In addition, FSO promises to provide unlimited integrated services at substantially high bandwidth and also to support reliability in smart cities with high bandwidth access networks [7, 8]. In order to facilitate medium-sharing infrastructure within wireless networks. In the literature, a number of Multiple-Input Multiple-Output (MIMO) systems have been suggested as options for high bandwidth access networks for the smart city. The exponential increase of data traffic has inspired researchers across the world to explore various multiplexing techniques within access networks to increase its capacity and transmission distance. Most of the multiplexing schemes for access networks are based on time division multiplexer (TDM) [9], wavelength division multiplexer (WDM) [10] have been used besides frequency division multiplexer (OFDM) [11] and optical code division multiple (OCDM) [7]. Amongst many of the multiplexing schemes, spatial division multiplexing (SDM) is a swiftly emerging as a potential candidate for increasing the aggregate bandwidth of current optical fiber systems. Moreover, in order to overcome the limitation in FSO, the researchers have motivated to use SDM. SDM was introduced in FSO which provides higher capacity and a wide coverage area to facilitate a more number of users [12, 13]. Additionally, it is a new scheme that has attracted remarkable attention as an innovative technology which increases the data rate [8, 14, 15]. Besides, SDM multiplexing can support several modes propagate editor@iaeme.com

3 Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, through optical fibers transmission. An SDM is an optical communication method where spatial modes are utilized as information channels carrying independent data streams. Though FSO based on SDM has plenty of advantages, its performance is unpropitiously affected by the atmospheric turbulence. The main causes of interference are haze and rain which changes the characteristics of the transmitted light and as a result decreases the power density of the signal transmitted and the effective distance of the FSO link [16]. Equalizers efficiently mitigate the distortion resulting from noise and atmospheric turbulence [17, 18]. This postprocessing [19] mechanism ensures that the received signal is sufficiently eliminated unwanted noise at the receiver side. Electronic and photonic equalization schemes [12, 18, 20, 21] could possibly be explored and integrated into the system. The electrical equalizer) linear Gaussian filter ( in this paper is used to affect mode filtering in order to clean the signal at the receiver. The rest of the paper is organized as follows. Section 2 describes the research methodology employed to test or model. Section 3 presents data and description of our experiments. In Section 4, this article then concludes with a summary. 2. RESEARCH METHODOLOGY In this section, simulation of SDM over the FSO link under different weather conditions are provided. The simulation aims to achieve the maximum possible medium range of 10- channels. The simulations are carried out on optisystem software [21-27] (as shown in Figure 1). The physical layer components for the FSO based on SDM system consists of three parts: i) a central office which operates as a transmitter; 2) FSO channel; and 3) a receiver with an electrical filter which is the customer premises. Figure 1 Simulation setup of spatial division multiplexing over free-space optics In the transmitter side, the special optical transmitters are used to generate data (binary source) at 10-Gbit/s. Additionally, the data is encoded using modulation is based on nonreturn to zero (NRZ) sequence. The transmitter has a subcarrier over a wavelength (1550 nm) and sends 10-channel goes to ten Hermite-Gaussian (HG) modes. HG modes are HG 01, HG editor@iaeme.com

4 Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter 02, HG 03, HG 04, HG 11, HG 12, HG 13, HG 14, HG 21 and HG 22. These modes are transmitted 100 Gibt/s along FSO under a number of weather conditions. Figure 2 shows the HG modes phase in SDM over FSO. Furthermore, each particular optical transmitter carries an array which emits one HG mode. Given 10 Gbit/s is transmitted based on one wavelength. Thus, with 10-channel based, the total data rate is 10 x 10 Gbit/s = 100 Gbit/s over FSO channel is 14 km long under very clear weather condition. After FSO, the de-multiplexer is made to retrieve the signals from the FSO. Moreover, the presumed the ten Photodetector were used to retrieve the signals with Gaussian filter. Finally, Table 1 lists the rest factors in our simulations. Figure 2 Modes phase of Hermite-Gaussian (HG 0 1, HG 0 2, HG 0 3, 0 4, HG 1 1, HG 1 2, HG 1 3, HG 1 4, HG 2 1, and HG 2 2) modes in SDM over FSO. Table 1 Factors assigned in the simulation. Factor value Parameters of the receive transmitter apertures Laser power 20 cm 20 cm 1 dbm beam divergence 1 µrad [14] 3. RESULTS AND ANALYSIS To verify system performance, three performance components will be examined; the parameters are: i) Eye diagram; 2) Bit Error Rate (BER); and 3) Q-Factor. Specifically, the eye diagram is an oscilloscope block used to display the optical signal noise as electrical signal noise. Additionally, BER is usually used to compute the transmitted bit errors due to editor@iaeme.com

5 Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, signal loss, dispersion, scattering, or noise by matching the transmitted binary data from the transmitter to the receiver in the optical medium. Lastly, The Q-Factor is a dimensionless parameter that describes how under-damped an oscillator. Therefore, the performance of a 10-channel transceiver system is evaluated in an SDM over the maximum distance range FSO under different weather condition. The evaluation is carried out under different weather conditions based on electrical equalization at the receiver for high bandwidth access networks. As listed in Table 2, the examined weather conditions are: i) very clear, ii) clear sky, iii) light rain, iv) heavy rain, v) light haze, and vi) heavy haze. Furthermore, the simulated system has transmitted 100 Gbit/s up for a distance of meters FSO in superbly very clear weather condition with performance results for BER and for the Q-factor. We then transmitted 100 Gbit/s up for a distance of meters FSO during clear sky with performance results in for BER and for the Q-factor. Additionally, transmission is carried up to 8200 meters distance FSO during a light rain with performance results for BER and for the Q-factor. After that, we performed a transmission up to 4200 meters distance FSO during heavy rain with performance results for BER and for the Q-factor. On the other hand, for light haze weather condition, the system transmitted 100 Gbit/s up for a distance of 2300 meters FSO with performance results for BER and for the Q-factor. Additionally, we transmitted up to 1100 meters distance of FSO during heavy haze with performance results for BER and for the Q-factor. Obviously, the performance improves along with the improvement of the bandwidth of the optical wireless communication system. Table 2. BER and Q-Factor values of SDM over maximum distance range FSO under different weather condition. Weather Condition Attenuation (db/km) Max-Link- Range FSO BER Q-Factor Very clear m e Clear sky m e Light rain m e Heavy rain m e Light haze m e Heavy haze m e Figure 3 and 4 illustrate the comparison among the adopted weather conditions for the different distance of FSO based on BER and Q-Factor through different distance starting from 1000 meters to meters. For instant, in distance 1000 meters the results of BER are (0.00E+00, 0.00E+00, 0.00E+00, 0.00E+00, 0.00E+00, and 4.05E-29) and for Q-factor are (147.63, , , , 75.31, and ) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions, respectively. Additionally, in distance 2000 meters the results of BER are (0.00E+00, 0.00E+00, 0.00E+00, 0.00E+00, 1.76E-39, and 1.00E+00) and for Q-factor are ( , , , , , 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions, in distance editor@iaeme.com

6 Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter 3000 meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are (0.00E+00, 0.00E+00, 0.00E+00, 6.90E-89, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , , 0, and 0), in distance 4000 meters the results of BER are (0.00E+00, e-319, 1.72E-224, 5.21E-17, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , , 0, and 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions Furthermore, in the distance 5000 meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are (5.49E-214, 6.60E-172, 4.26E-107, 2.86E-04, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , , 0, and 0), and in the distance 6000 meters the results of BER are (8.81E- 130, 2.29E-98, 6.21E-54, 1.00E+00, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , 0, 0, and 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions. Figure 3 Q-factor values of HG modes in SDM over FSO different weather conditions. Moreover, the results of Q-Factor and BER shown in Figure.3 and Figure.4 in distance 7000 meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are (1.60E-82, 6.71E-59, 1.67E-28, 1.00E+00, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , 0, 0, and 0), in distance 8000 meters the results of BER are (1.70E-54, 1.12E-36, 7.57E-16, 1.00E+00, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , 0, 0, and 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions, in the distance 9000 meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are (3.32E-37, 1.15E-23, 2.45E-09, 1.00E+00, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , 0, 0, and 0), and in the distance meters the results of BER are (3.82E-26, 8.12E-16, 7.05E-06, 1.00E+00, 1.00E+00, and 1.00E+00) and for Q-factor are ( , , , 0, 0, and 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions editor@iaeme.com

7 Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, Additionally, in the distance meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are ( , , , 1.00, 1.00 and 1.00) and for Q-factor are ( , , , 0, 0 and 0), in distance meters the results of BER are ( , , , 1.00, 1.00 and 1.00) and for Q-factor are ( , , , 0, 0 and 0) for very clear, clear sky, light rain, heavy rain, light haze, heavy haze weather conditions and in the maximum distance is meters for weather very clear, clear sky, light rain, heavy rain, light haze, heavy haze conditions the results of BER are ( , , 1.00, 1.00, 1.00, and 1.00) and for Q-factor are ( , , 0, 0, 0 and 0). Figure 5 and 6 illustrate the eye diagram where the eye wide for all channels on the ten HG modes have been widened under very clear weather condition. Figure.5 shows the result of the Q-Factor and BER of (HG 0 1, HG 0 2, HG 0 3, HG 0 4, HG 1 1, and HG 1 2) modes under clear weather case which are ( , , , , , and for the quality factor) and ( , , , , , and for BER), Fig.5 show the result of Q-Factor and BER of which are ( , , , and for the quality factor) and ( , , and for BER) for HG 1 3, HG 1 4, HG 2 1, and HG 2 2 under clear weather case Figure 4 BER values of HG modes in SDM over FSO different weather conditions. As shown in Figure.5, and Figure.6 illustrates the eye diagram where the eye wide for all channels on the ten HG modes have been widened under very clear weather condition. Figure.5 shows the result of the Q-Factor and BER of (HG 0 1, HG 0 2, HG 0 3, HG 0 4, HG 1 1, and HG 1 2) modes under clear weather case which are ( , , , , , and for the quality factor) and ( , , , , , and for BER), Fig.5 show the result of Q-Factor and BER of which are ( , , , and for the editor@iaeme.com

8 Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter quality factor) and ( , , and for BER) for HG 1 3, HG 1 4, HG 2 1, and HG 2 2 under clear weather case. Figure 5 Eye diagram, Q-Factor and BER of the (HG 0 1, HG 0 2, HG 0 3, HG 0 4, HG 1 1, and HG 1 2) modes in SDM over FSO. Figure 6 Eye diagram, Q-Factor and BER of the (HG 1 3, HG 1 4, HG 2 1, and HG 2 2) modes in SDM over FSO editor@iaeme.com

9 Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, 4. CONCLUSION This paper investigated the performance of BER and Q-Factor over different distances of over FSO in different weather conditions based on the linear equalizer. The evaluation aimed to compensate atmospheric turbulence in optical communication systems of 10 modes SDM. The findings showed that the performance improves along with the improvement of the system capacity which can be effectively increased with the use of SDM over FSO that operate at 1550 nm wavelength based on LGF. Furthermore, the results demonstrated that 10 x 10 Gbit/s SDM-FSO system (in different weather conditions) is effective in improving the quality of data in an optical wireless communication system. Finally, the performance has been validated by measuring and analyzing eye diagrams, Q-Factor and BER. REFERENCES [1] Khalighi, M. A., & Uysal, M. (2014). Survey on free space optical communication: A communication theory perspective. IEEE communications surveys & tutorials, 16(4), [2] Prabu, K., Charanya, S., Jain, M., & Guha, D. (2017). BER analysis of SS-WDM based FSO system for Vellore weather conditions. Optics Communications, 403, [3] Zabidi, S. A., Al Khateeb, W., Islam, M. R., & Naji, A. W. (2010). The effect of weather on free space optics communication (FSO) under tropical weather conditions and a proposed setup for measurement. In Computer and Communication Engineering (ICCCE), 2010 International Conference on (pp. 1-5). [4] Wang, Z., Zhong, W. D., Fu, S., & Lin, C. (2009). Performance comparison of different modulation formats over free-space optical (FSO) turbulence links with space diversity reception technique. IEEE Photonics Journal, 1(6), [5] Borah, D. K., & Voelz, D. G. (2009). Pointing error effects on free-space optical communication links in the presence of atmospheric turbulence. Journal of Lightwave Technology, 27(18), [6] G. Li, N. Bai, N. Zhao, and C. Xia, "Space-division multiplexing: the next frontier in optical communication," Advances in Optics and Photonics, vol. 6, pp , [7] Aldouri, M. Y., Aljunid, S. A., & Fadhil, H. A. (2013). Study of the OCDMA Transmission Characteristics in FSO-FTTH at Various Distances, Outdoor. J. Opt. Commun., 34(2), [8] Ahmed, N., Aljunid, S. A., Fadil, A., Ahmad, R. B., & Rashid, M. A. (2011, September). Hybrid OCDMA/WDM system using complementary detection technique for FTTH access networks. In Industrial Electronics and Applications (ISIEA), 2011 IEEE Symposium on (pp ). IEEE. [9] Wang, D., Zhou, W., Li, Z., Chen, Z., Yin, H., Zhu, S., & Li, A. (2016). Research on freespace optical communication based on time-division multiplexing. In Optoelectronic Imaging and Multimedia Technology IV (Vol , p F). [10] Shahidinejad, A., Amiri, I. S., & Anwar, T. (2014). Enhancement of indoor wavelength division multiplexing-based optical wireless communication using microring resonator. Reviews in Theoretical Science, 2(3), editor@iaeme.com

10 Hermite-Gaussian Mode in Spatial Division Multiplexing Over Fso System Under Different Weather Condition Based on Linear Gaussian Filter [11] Amphawan, A., Chaudhary, S., & Chan, V. W. S. (2014). 2 x 20 Gbps-40 GHz OFDM Ro-FSO transmission with mode division multiplexing. Journal of the European Optical Society-Rapid publications, 9. [12] T. Masunda, A. Amphawan, and A. Al-dawoodi, "Effect of decision feedback equalizer taps on 3 6-channel mode-wavelength division multiplexing system performance in multimode fiber," in EPJ Web of Conferences, 2017, p [13] Amphawan, A., Ghazi, A., & Al-dawoodi, A. (2017). Free-space optics mode-wavelength division multiplexing system using LG modes based on decision feedback equalization. In EPJ Web of Conferences (Vol. 162, p ). [14] Prasad, S. B., Saini, J. S., & Singh, K. M. (2009). Investigation of heat transfer and friction characteristics of packed bed solar air heater using wire mesh as packing material. Solar Energy, 83(5), [15] Dhiman, P., Thakur, N. S., Kumar, A., & Singh, S. (2011). An analytical model to predict the thermal performance of a novel parallel flow packed bed solar air heater. Applied energy, 88(6), [16] Rai, A. K., Singh, N., & Sachan, V. (2013). Experimental study of a single basin solar still with water cooling of the glass cover. International Journal of Mechanical Engineering & Technology (IJMET), 4(6), 1-7. [17] Ho, C. D., Yeh, C. W., & Hsieh, S. M. (2005). Improvement in device performance of multi-pass flat-plate solar air heaters with external recycle. Renewable Energy, 30(10), [18] Ho, C. D., Yeh, H. M. and Wang, R. C. (2005). Heat-transfer enhancement in double-pass flat plate solar air heaters with recycles. Energy, 30, pp [19] Yeh, H. M., & Ho, C. D. (2009). Solar air heaters with external recycle. Applied Thermal Engineering, 29(8-9), [20] Fazea, Y., & Amphawan, A. (2018). 40Gbit/s MDM-WDM Laguerre-Gaussian mode with equalization for multimode fiber in access networks. Journal of Optical Communications, 39(2), [21] O. U. Guide, "RSOFT Design Group," ed: Inc, [22] Mahmuddin, M., & Al-dawoodi, A. G. M. (2017). Experimental Study of Variation Local Search Mechanism for Bee Algorithm Feature Selection. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), 9(2-2), [23] Al-dawoodi, A. G. M., & Mahmuddin, M. (2017). An Empirical Study of Double-Bridge Search Move on Subset Feature Selection Search of Bees Algorithm. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), 9(2-2), [24] Ghazi, A., Aljunid, S. A., Noori, A., Idrus, S. Z. S., Idrus, Z. S., & Al-dawoodi, A. (2019). Design & Investigation of 10 x 10 Gbit/s MDM over Hybrid FSO link under Different Weather Conditions and Fiber to The Home. Bulletin of Electrical Engineering and Informatics, 8(1). [25] Masunda, T., Amphawan, A., Alshwani, S., & Aldawoodi, A. (2018, April). Modal Properties of a Varied High Indexed Large Core 4-Mode Photonic Crystal Fiber. In 2018 IEEE 7th International Conference on Photonics (ICP) (pp. 1-3). [26] Aldawoodi, A., Fareed, A., Masuda, T., Ghazi, A., Fakhrudeen, A., M., Aljunid, S. A., Idrus, S.Z.S., and Amphawan, A. Comparison of Different Wavelength Propagations over editor@iaeme.com

11 Sara Alshwani, Ahmed M. Fakhrudeen, Mohammed Nasih Ismael, Aras Al-Dawoodi and Alaan Ghazi, Few-Mode Fiber based on Space Division Multiplexing in Conjunction with Electrical Equalization, International Journal of Electronics and Telecommunications. Vol 65(1) pp(1-6), [27] Aldawoodi, A., MARAHA, H., ALSHWANI, S., GHAZI, A., ALJUNID, S. A. FAKHRUDEEN, A. M., MAJEED, A. A., AMEEN, K. A. Investigation Of 8 X 5 Gb-S Mode Division Multiplexing -Fso System Under Different Weather Condition, Journal of Engineering Science and Technology. Vol 14(2) p.p(1-4), editor@iaeme.com