195 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Power Link Budget Analysis to Run Optic Fiber Cables for Connection Between Mabutsane and Motokwe Villages in Botswana Moses Njovana a* , Sajid Sheikh b a,b Department of Electrical Engineering, Faculty of Engineering and Technology, University of Botswana, Private Bag UB0061, Gaborone, Botswana a Email: njovanamosest@gmail.com b Email: sheikhsm@ub.ac.bw Abstract This paper presents design considerations and field implementation of low-cost optical fiber system to a small village approximately 87 Km to the north of Mabutsane, called Motokwe. The optical power link budget of two single mode Optical Fiber cables were considered and compared. The considerations to be made were the system margin, received power, and input power of either cables. Both cables were simulated using MATLAB and their respective results were obtained. The most suitable system was subsequently selected for the implementation. In this instance, the most suitable system was one that required the least amount of input power, least losses and had a considerably large system margin (at least 10dB). Keywords: Attenuation; Macrobending; Microbending; Optical Fiber; Power Link Budget. 1. Introduction A communication system transmits information from one place to another, whether separated by a few kilometers or by transoceanic distances[1]. An optical Fiber is a thin, flexible, transparent glass cylinder that acts as a waveguide or "light pipe", to transmit light between the two ends of the Fiber. The light may be used as a means of information transmission, making it an optical fiber communication medium [2]. ------------------------------------------------------------------------ * Corresponding author. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 196 The need for connectivity has never been any higher than it is today and it is only expected to rise [3]. Optical fiber cable is a medium of choice because of its high transmission rates (up to 200 Gb/Second for Optical Fiber), large bandwidth, low attenuation over large distances as well as immunity to noise [4]. However, Botswana, like most developing countries has not yet connected optical fiber to most of the remote parts of the country, thus effectively leaving over 30% of the population without access to the internet. Figure 1 below is a Map of Botswana showing the areas of the country currently covered by optical fiber network (indicated in red). As can be seen on the map, the village of Motokwe, like many others does not yet have any Optical Fiber coverage. This paper is about the implementation of an affordable and practical optical fiber system from Mabutsane to Motokwe. This link will act as an optical fiber backbone. The most important aspects for a design engineer is determining which type of optical fiber is most appropriate for the distance to be covered, as well as taking into consideration all factors that might cause his optical signal to be distorted, or not received entirely and plan for them accordingly. The paper is structured as follows: section 2 is the materials and methods. Section 3 gives the results as well as the MATLAB code used for the simulation of the optic fiber system. Section 4 is the discussion and finally Section 5 is the conclusion. Figure 1: Optical fiber coverage in Botswana [5] American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 197 2. Materials and methods In this study, google maps was used to measure the distance between the two villages as well as monitor the proposed route the cable lining was going to take. The cable is set to run just along the main highway that connects Mabutsane and Motokwe. This distance was ascertained to be 87.2Km, and for the entire length the line is generally 1 meter outside of the highway, right of the way line[6]. Along the stretch it was established there were 2 main changes in direction that could be characterized as macro bends. A Macro bend occurs when the curvature of the bend of an optic fiber is much larger than its diameter. This causes light waves to suffer sever loss due to radiation of the evanescent field in the cladding region. As the radius of the curvature decreases, the loss increases exponentially until it reaches at a certain critical radius [7]. For any radius a bit smaller than this point, the losses suddenly become extremely large as illustrated in figure 2 below. Figure 2: Illustration that as the bend tightens, the optical loss increases [8] Figure 3: The proposed cable route [9] B A American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 198 However, opting not to bend the cable, some connectors were put at these turns in order to have a predictable loss from the optic fiber cable, which will be taken into account in the power link budget analysis for the network. These points are marked and labelled A and B in figure 3 below. Point A is about 64km from Mabutsane and point B is 1Km away from Mabutsane. There are two Optical fiber cables that are used to make two distinct Optical systems which shall be subsequently simulated. The first Optical fiber system with the following parameters was chosen. The First Optical fiber cable to be simulated is the single mode optical fiber with the proprietary name; “ëdge 1.25G-SFP-120D”, which is a single mode fiber. It was connected to a system to give the following properties, henceforth known as OF-1 Table 1: Optical Fiber 1 (OF_) Properties Media Type Single mode fiber Min. Receiver Sensitivity (Pr) -32 dB Avg. Transmitting Power 0 dB Source Power (Ps): Min/Max 0/5 dB Max Transmitter distance (L) 120 Km Typical Splice loss (lsp) 0.2 dB Typical connector loss (lc) 0.4 dB Transmitter/Receiver Wavelength 1550 nm Fiber attenuation (αf) 0.2 dB/Km The second Optical fiber cable to be simulated in our system is the single mode optical fiber cable with the proprietary name; “ edge CWDM-1.25G-SFP-150-45”, henceforth referred to as OF_2. It was connected to our system to give the following properties; Table 2: Optical Fiber 2 (OF_2) Properties Media Type Single mode fiber Min. Receiver Sensitivity (Pr) -34 dB Avg. Transmitting Power -2 dB Source Power (Ps): Min/Max -2/7 dB Max Transmitter distance (L) 150 Km Typical Splice loss (lsp) 0.14 dB Typical connector loss (lc) 0.4 dB Transmitter/Receiver Wavelength 1450 nm Fiber attenuation (αf) 0.3 dB/Km Both the cables are spliced at every 10Km. To find the number of splices, the expression below is used - (5) Where L is the total length of fiber and li is the length between splices. Using this expression, the number of splices, n, is found to be 8. The total number of connectors, m becomes 4, i.e one each on the transmitter and American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 199 receiver side of the cable, and one each for the 2 bends. Using the optical fiber power budget in (4), the above values are used to simulate what the value of Transmission Power (Pt) is, as well as establish the System Margin of this system using MATLAB. 3. Results Before simulating for the Mabutsane-Motokwe Optical fiber, the given 80Km Optical fiber cable was simulated first, using the same code. This cable’s parameters, code and results are shown in appendix E.Both the “edge 1.25G-SFP-120D” and the “1.25 G-SFP-150-45” were subsequently simulated. The code and simulated results are shown below. Figure 3: Matlab code used for the simulation American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 200 Figure 4: Results for the simulation of OF_1 & OF_2 The graph shown in Figure 5 was plotted using the above results. Figure 5: The received Power against the Source Power in dB 4. Discussion For OF_1, the total losses amount to 20.64dB, giving a system margin of 11.36dB. The recommended minimum System margin is 10dB. This is a good indicator that the system’s attenuation is not going to be a cause for the disruption in signal transmission for this system. The greater system margin is also ideal as it considers sources of signal losses otherwise not accounted for in the link power budget simulation. These losses are mainly because of a range of external factors, not factored into our “optic loss equation” that must none-the-less be taken into consideration in order to determine the cable construction that will continuously maintain the desired American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 201 characteristics hence, predictable results. The external factors relating to the various environmental conditions can be divided into two categories: i) natural external factors (temperature, wind, water, earthquakes, etc.), which are comprehensively listed in Appendix A; ii) man-made factors (smoke, air pollution, fire, etc.), which are listed in Appendix B. For both categories of factors, the tables show the effects on the optical cables laid in different environments. The cable to be laid down from Mabutsane to Motokwe, however, is going to be for the most part, a buried cable. Both Mabutsane and Motokwe are found in the Kalahari Desert, and like any typical desert, the area is characterized by extremes of temperatures, sporadic rainfall as well as some limited biodiversity [10]. The extremes of temperatures Increase optical loss due to high and low temperature, whilst the little moisture present, typically in the form of salt water may lead to corrosion of the cable amour which may reduce the lifetime of the optical fiber [11]. Possible “biological attacks” from insects, rodents and birds could damage the sheath, further limiting the lifespan of the cable[12]. Any system, therefore, that meets a minimum of the above-mentioned system margin along with the range of its received powers being at least equal to the minimum receiver sensitivity will be considered a viable system The results for OF_1 shown in table 1 show that the received powers range from -20.64dB to -15.64dB, with a system margin of 11.36dB. This is above our system’s minimum receiver sensitivity of -32dB, meaning this system is viable. Table 3: Results for OF_1 Source Power (dB) Received Power (dB) 0 -20.64 1 -19.64 2 -18.64 3 -17.64 4 -16.64 5 -15.64 System Margin (dB) 11.36 The results for OF_2 shown in table 2 show that the received powers range from -28.88dB to -19.88dB, with a system margin of 3.12dB. Now, although all the received values are above our system’s minimum receiver sensitivity of -34dB, the system margin is way below the recommended minimum of 3.12dB. This lack of adequate “margin of error” makes this second system not viable. The Power at the source can always be increased in an attempt to increase the system margin, however increasing the input power will directly increase the overall cost of implementing the system. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 202 Table 4: Results for OF_2 Source Power (dB) Received Power (dB) -2 -28.88 -1 -27.88 0 -26.88 1 -25.88 2 -24.88 3 -23.88 4 -22.88 5 -21.88 6 -20.88 7 -19.88 System Margin (dB) 3.12 5. Conclusions A low budget optical fiber system to be introduced to link Mabutsane and Motokwe with a single mode optical fiber with properties similar to that of OF_1 is a technically feasible project. The costs can further be minimized by transmitting the signal using the minimum input power of 0dB. The transmitter part of this system, which is laser, will be in Mabutsane, whilst the receiver (photodiode) part of the system will be in Motokwe. Both the transmission and receiving wavelength will be at 1550nm, with a maximum data rate of 1.25Gbps. 6. Appendices Appendix A: Showing some of the natural external factors that could affect optical fiber cables. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 203 Figure 6: Showing natural external factors affecting optical fiber cables [11] American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 204 Appendix B: showing the man-made external factors that could affect optical fiber cables Figure 7: Showing the man-made external factors that affect optical fiber cables [11] References [1]. C. DeCusatis, Handbook of Fiber Optic Data Communication, Third. Elsevier Academic Press publications, 2008. [2]. G. P. Agrawal, Fiber-optic communications systems, Third. John Wiley & Sons, Inc, 2002. [3]. Cisco, “Cisco Annual Internet Report (2018–2023),” Cisco Publications. 2020. [4]. F. Mitschke, Fiber Optics. New York: Springer, 2009. [5]. S. Tlhako, “The state and future of Botswana Optic Fibre Networks,” in OPEN DATA OPEN SCIENCE CONFERENCE, 2017. [6]. A. D. Ogbe, “Optimizing the Efficiency of Fiber-Optics Technology in Telecommunications Systems,” in International Conference on Emerging and Sustainable Technologies for Power and ICT in a Developing Society, IEEE NIGERCON Proceedings, 2013. [7]. G. N. Ezeh, “Severity Index Analysis of The Problems of Optical Fiber Communication In Nigeria: A Case Study of South Eastern Nigeria,” J. Nat. Appl. Sci., vol. 4, no. 1, 2013. [8]. O. Strobel, “Microwave & Telecommunication Technology,” in 20th International Crimean Conference, 2010. [9]. Google, “Google Maps directions from Motokwe to Mabutsane.” [Online]. Available: https://www.google.ca/maps/dir/Motokwe/Mabutsane/@-24.2214071,23.1912834,11z/. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 2, pp 195-205 205 [10]. Ministry of Environmental Conservation and Forestry, “National Biodiversity Strategy and Action Plan Myanmar,” p. 121, 2011. [11]. I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n, Optical fibres, cables and systems. 2010. [12]. T. Kaewchalermtong, “Thailand’s experiences on co‐ deployment of fiber‐ optic infrastructure along road and rail networks,” in Workshop on Cross-border co-deployment of fibre optic infrastructure along road and rail networks, 2018.