Open Access is an initiative that aims to make scientific research freely available to all. To date our community has made over 100 million downloads. It’s based on principles of collaboration, unobstructed discovery, and, most importantly, scientific progression. As PhD students, we found it difficult to access the research we needed, so we decided to create a new Open Access publisher that levels the playing field for scientists across the world. How? By making research easy to access, and puts the academic needs of the researchers before the business interests of publishers.
We are a community of more than 103,000 authors and editors from 3,291 institutions spanning 160 countries, including Nobel Prize winners and some of the world’s most-cited researchers. Publishing on IntechOpen allows authors to earn citations and find new collaborators, meaning more people see your work not only from your own field of study, but from other related fields too.
With the advancement in communication systems, there is a need for large bandwidth to send more data at a higher speed. Wavelength division multiplexing (WDM)-ethernet passive optical network (EPON) is important due to its efficiency, higher bandwidth, low-cost passive connection, and reduced complexity of deployment and maintenance of the network. The implementation of radio over fiber in wireless communication achieved a high data rate and high capacity due to the utilization of high-capacity optical fiber and the flexibility of wireless networks. Optical wireless channel (OWC) is the technique in free-space optical communication, which is a high-speed and large-capacity type of communication system. It uses infrared light to convey message from transmitter to receiver. OWC is the solution to the last mile problem, mainly in overpopulated urban areas. This paper demonstrated the integration of OWC and WDM-EPON technology that makes the system more advanced and cost-effective, with high BW and high data rate. The results analysis is based on bit error rate (BER), quality factor (Q Factor), and eye pattern. The system has been analyzed using different power source values, different lengths, and different operating wavelengths. The results for OWC have shown that 2.5 Gbps is better than 5 and 10 Gbps.
*Address all correspondence to: abeha2005@gmail.com
1. Introduction
In a communication system, there are so many ways of communication. Wireless communication demands a high data rate, large bandwidth (BW), low cost, and flexible design due to the gradually increasing number of subscriber. In wireless communication, the information can be transported over a long distance without any need of wire or cable. Subscribers require very high-definition video on demand and internet with high quality and guaranteed data delivery. So new technology is adopted for satisfying these requirements. Optical communications are advanced from lengthy optical fibers to powerful wireless communications. Laser communication is able to transfer information up to several Gbps data rates and covers up to thousands of kilometers [1]. Optical wireless channel (OWC) communication is an ultra-high speed and large capacity communication. It uses free space as a channel and laser light in the IR region as a carrier. The laser light can travel a long distance because it has a very narrow beam width. An additional reason for using OWC is RF wavelength much longer than optical wavelength. Hence, the beam width that can be achieved using lasers is narrower than that of the RF system and it can travel without much loss [2].
The advantages of OWC are that it uses a very small size of antenna at transmitter and receiver sides and it can also minimize the power used for the communication system and offers a high data rate. Most attractive benefit of OWC is its capability to utilize a large amount of unregulated licensed-free bandwidth and solves the problem of the “last mile,” mainly in overpopulated urban areas [1, 2].
In wireless optical communication systems, light is emitted directly from a fiber termination to free space through an optical antenna. The transmitted optical beam is focused, using the receiver optics, directly to fiber and then sent to the fiber for detection at the receiver end. The uses of free-space optical communication systems are that they are capable of replacing wireless over optical links. After announcing passive optical network (PON) in this system, it improves the system-developed network and deals with more advanced features. PON is quite reliable, easy to maintain, easy to install, power efficient, and provides the most cost-effective architecture for the network plant in delivering the radio signal. There are many types of PON technologies. “Among them, Gigabit-PON (GPON) and Ethernet PON (EPON) are the most popular PONs [3].” “EPON has been used in this paper. In this paper, combination of OWC and optical fiber makes the system very useful and attractive for 5G network. The advantages of both techniques combine together and make a new technology that leads the communication [4].”
The recent development of new applications and services, primarily multimedia applications, has driven the need for higher bandwidth and a faster access network. But these cannot be fully realized with the conventional single-channel EPON. In such conditions, the realization of wavelength division multiplexing (WDM)-EPONs is the best solution for the implementation of converged triple-play networks [5].
A novel algorithm of dynamic wavelength priority bandwidth allocation with traffic class hopping for wavelength and bandwidth allocation with QoS support, including both offline and modified online scheduling, is presented in this paper. A two-level WDM-EPON upgrades solution, which implements two main functions: First, efficient capacity scaling with bandwidth sharing, and Second, deterministic QoS provisioning. Recent findings and issues in ROF cellular communication have been discussed and the feature of future ROF technology in cellular communication has been presented [6]. The literature has discussed the advantages and applications of wireless over fiber technology. Wireless over fiber technology has the following advantages compared with electronic signal distribution [7].
Mobile traffic is quickly increasing to access a variety of services. And also their access methods diversify in various types of radio air interfaces, 3.5, 3.9, and 4G, commercial or private wireless local area network (WLAN). This tendency requires more efficient use of radio frequency and the reduction of radio cell size for heterogeneous wireless access. Then the distribution of a vast number of base stations (BSs) and the provision of more efficient and flexible mobile backhaul networks will be required in a wide area [5]. As a broadband and flexible entrance network, over WDM-EPON architecture was proposed. Wireless over fiber and WDM-EPON both have recently attracted much attention for their huge bandwidth and scalability [8, 9].
To analyze the WDM-EPON system, three parameters (Q factor, BER, and eye height) are used. “Q factor is not a dimension quantity that analyzes the quality of the signal. BER is also not a dimension quantity that analyzes the performance of the signal.” BER can be defined as the ratio of the number of bit errors recognized on the receiver side to the original number of bits transmitted on the transmitter side. Depending on the definition of the minimum bit error rate, the ideal case is when the ratio becomes 0 and the worst case is when the ratio becomes 1. The distortion of the signal is realized by the height of the eye. Less distortion has occurred to the signal when the height of the signal is largest (Figures 1 and 2) (Table 1).
Figure 1.
Network set up for WDM-EPON link based on BOF and OWC.
Figure 2.
Simulation design of WDM-EPON with OWC.
Quantity
Parameter
Value
OWC
Length
50 km
PRBS generator
Bit rate
2.5 Gbps
CW laser array
Power
5 dBm
Wavelength
1550, 1549.2, 1548.4, 1547.6, 1546.8, 1546, 1545.2, and 1544.4 nm
An appropriate way to measure the performance of the system is by using an eye diagram, as shown in Figures 3–5. The eye opening clearly indicates that the system performance is good. The Q factor and BER performances of OWC for the different data rates are shown. “The eye diagram output is taken by considering the bit rates of 2.5, 5, and 10 Gbps.” In certain optical systems, the value of Q factor for 2.5 Gbps is higher than 5 and 10 Gbps and the value of BER for 2.5 Gbps is lower than 5 and 10 Gbps in case of OWC. “Because of eye opening of 2.5 Gbps, its performance is better than others.”
Figure 3.
Eye diagram of min BER at 2.5 Gbps, 5 dBm, 50 km, and 1550 nm OWC.
Figure 4.
Eye diagram of min BER at 5 Gbps, 5 dBm, 50 km, and 1550 nm OWC.
Figure 5.
Eye diagram of min BER at 10 Gbps, 5 dBm, 50 km, and 1550 nm OWC.
4.1.1 Data rate of 2.5 Gbps
4.1.2 Data rate of 5 Gbps
4.1.3 Data rate of 10 Gbps
4.2 Q factor
In this section, a comparison is made between three different sets of bit rates, which are 2.5, 5, and 10 Gbps bit rates with the use of power and length. This comparison is made according to the maximum Q factor, in both the downstream and the upstream traffic directions. Power and length are essential components in order to analyze the performance of the optical network regarding channel capacity. The power affects the performance of the system by taking random samples of OLT power. It has been observed that the Q factor begins with 11.02 at 0 dBm. By increasing the power to 20 dBm, we get 131.47. This indicates that the power of fiber increased the Q factor values increased (Figure 6).
Figure 6.
Max Q factor at 50 km, 1550 nm with variable power for OWC.
Q factor variable power range for 2.5, 5, and 10 Gbps bit rates. It has been observed that by increasing OLT power, Q factor increased for all bit rates. The Q factor of 2.5 Gbps is the best compared to 5 and 10 Gbps. Because of this, 2.5 Gbps bit rate has the best performance. Q factor for 2.5, 5, and 10 Gbps bit rates in case of 10–100 km length range. It has been observed that with increasing OWC length, Q factor decreased for all bit rates. We observed from the above table that the Q factor of 2.5 Gbps is the best compared to 5 and 10 Gbps.
Figure 7 shows that 2.5 Gbps bit rate has a good performance than 5 and 10 Gbps bit rates, because 2.5 Gbps bit rate demands less bandwidth than 5 and 10 Gbps bit rates.
Figure 7.
Max Q factor at 5 dBm, 1550 nm with variable length OWC.
4.3 BER
The results for BER of OWC are shown in Figures 8 and 9. In OWC as the OLT power increased, the bit error rate decreased and the length increased, the BER increases. This is because the dispersion increases as the optical fiber length increase. As we seen in the figures, the bit rates increase as the BER increases and the performance of the system decreases.
Figure 8.
BER of OWC at 5 dBm, 1550 nm for varied power values.
Figure 9.
BER of OWC at 5 dBm, 1550 nm for varied length values.
EPONs have developed as the best solution for the last mile problem. EPONs provide high-speed bandwidth, high reliability, maintenance, low-cost, and most importantly an easy spatial upgrade that can meet the continuous internet growth in terms of users and bandwidth demand. The last mile bandwidth problem has been broken. But that does not mean that the challenges of overcoming access constraints have become a thing of the past. The service providers shall be able to cost-effectively meet bandwidth requirements needed today and in the future will be to use fiber, passive plant, and the dedication of a wavelength per customer. WDM-EPON delivers greater distance capabilities, end-to-end transparency, and ease of scalability. A key advantage of WDM-EPON is a totally separate downstream wavelength for each of the subscribers. This separate wavelength provides more bandwidth to each subscriber, better security, and enhanced operational control.
The simulation was performed on Optisystem version 14 software. Good power budget is obtained from minimum BER and maximum Q factor at the output. WDM-EPON is very good choice for 5G wireless internet users due to its very high operating frequency, high data rate, and large bandwidth. From the above analysis, the BER and Q factor depend upon data rate, power OLT, distance of OWC, and operating frequency of ONU’s. The system was analyzed using different power source values, length of fiber, and operating wavelength for both downstream and upstream directions. It has been found that the more effective parameter in the performance was by increasing the power source of OLT in both downstream and upstream scenarios. It has also been found that the OLT power source controls the upstream. In upstream changing length of the fiber and operating wavelength situations, the results of BER and Q factor do not represent the correct behavior. “As the distance between transmitters and receiver and data rate increases, the BER increases and Q factor decreases.” The performance of received signal is very good up to 75 km of OWC length. As the power increases, BER decreases and Q Factor increases.
Dear GOD, thank you, blessed be Lord for evermore Amen and Amen! I would like to give my gratitude to my advisor Dr. Pushparaghavan for his constant support, guidance, and supervision, as well as help to build perfect skills in my scientific thinking to carry out this work. His support and belief in my efforts and to serve as the source of inspiration, encouragement, and professional guidance is also thankfully acknowledged. I would like to thank my host University Woldia University for giving the best chance.
Finally, I am so grateful to my parents and friends. I could not finish this master’s program without their full support.
1.Tiwari P, Jaiswal AK, Agrawal N, Nitin N. Analysis of bidirectional wireless optical integrated with optical fiber. International Journal of Computer Applications. 2015;121(5):7-12
2.Tiwari P, Jaiswal AK, Agrawal N, Nitin N. Performance analysis of a full duplex WDM-EPON based system with fiber to wireless optical network. International Journal of Computer Applications. 2015;121(9):25-29
3.Kramer G, Pesavento G. Ethernet passive optical network (EPON): Building a next generation optical access network. IEEE Communications Magazine. 2002;2002:67-73
4.McGarry P, Reisslein M, Maier M. WDM ethernet passive optical networks. IEEE Communications Magazine. 2006;44(2):15-22
5.Radivojevic MR, Matavulj PS. Highly flexible and efficient model for QoS provisioning in WDM EPON. Journal of Optical Communications and Networking. 2013;5(8):921-931
6.Nawawi NM, Idrus SM, Marwanto A. Investigation of Stimulated Brillouin Scattering for the Generation of Millimeter Waves for Radio over Fiber System. 2008
7.Tashiro T, Hara K, Kani J-I, Yoshimoto N, Iwatsuki K, Miyamoto K, et al. Experimental demonstration of RoF-DAS over WDM-PON with bandpass-sampling and optical TDM techniques. IEICE Electronics Express. 2012;9(3):206-212
8.Wake D, Nkansah A, Gomes NJ, Lethien C, Sion C, Vilcot JP. Optically powered remote units for radio-over-fiber systems. Journal of Lightwave Technology. 2008;26(15):2484-2491
9.Pandey VK. Radio-over-fiber (ROF) in cellular communication. International Journal of Scientific Engineering and Technology. 2013;2(6):462-464
Written By
Abera Haile
Submitted: 01 March 2022Reviewed: 06 April 2022Published: 08 January 2025
Open access peer-reviewed chapter
