fiber to the home (ftth) design and analysis using … to the home (ftth) design and analysis using...

Fiber To The Home (FTTH) Design and Analysis using OCDMA Structure

M.A.Othman, M.M.Ismail, H.A.Sulaiman, M.H,Misran, M.A.M.Said,

Centre for Telecommunication Research and Innovation (CeTRi) Fakulti Kej. Elektronik dan Kej. Komputer

Universiti Teknikal Malaysia Melaka Hang Tuah Jaya, Durian Tunggal 76100, Melaka, Malaysia,

[email protected], [email protected], [email protected], [email protected], [email protected]

Abstract

Since the beginning of the new millennium, dramatic changes in the telecommunication can be seen and have far reaching implications using optical fibers. The Internet is developed rapidly as higher bandwidth can be achieved with optical fibers with unlimited capabilities. As these potential evolve, optical network characteristic change to meet traffic demand. In this paper, a focus should be on the design and analysis of Fiber To The Home (FTTH) based on OCDMA structure. Optical code division multipleaccess (OCDMA) now deserves revisit for a powerful alternative in FTTH. This paper first introduces the basic of optical networks. Then, it roughly explains the type of system available for common optical network. Finally, we will explain and show analysis about OCDMA which is most promising structure to be implementing in FTTH.

Keywords: Optical fibers, Capabilities, FTTH, OCDMA

1. Introduction

Optical network is the method of using fiber optics to connect two or more devices together. Optical networking offers much faster data transfer rates than other convention network out there and can be stretched over an extremely large distances. While optical networks are costly to install, they are reliable and efficient than other mode of connectivity.

Optical technology is a promising candidate in solving the bandwidth limitation in access networks due to its large bandwidth that is at least 10 to 100 times (50tera-bits per second) more than conventional communication over a large area. However, to realize the full potential of optical technology it is necessary to build fully optical networks. The speed at which optical signals may be communicated is far greater than the speed at which data can be processed by electronic circuits. Optical networks now convert from optical to electronic form every time it needs to be routed or switched which bring down its full potential. It seems that there are more to explore of optical components in the electronic networking world.

Currently there is two generation of optical networks. First-generation optical networks simply replaced the copper wires with optical fibers. The second-generation optical networks take account into the differences and recent developments in optical devices and network technologies. [1]

Same as other communication system, optical networks have its own topologies. The four most common topologies used for fiber optic networks are linear bus, ring, star, and mesh configurations. Linear bus configuration for optical networks uses same concept as a non-optical networks that uses a coaxial cable as transmission medium and coupler to split the signal to the users. However, optical fibers need a more complicated coupler that involved active and passive coupler. In ring topology, a single closed path is formed when consecutive nodes connected by point-to-point links that used active device. As for a star architecture, all the nodes are connected to a single point named as the central node or hub. Lastly, the point-to-point links in a mesh network is connected in an arbitrary fashion. This allows significant network configuration that allows flexibility and robustness.[2] Figure 1 shows the basic infrastructure of four typical network topologies.

Fiber To The Home (FTTH) Design and Analysis using OCDMA Structure M.A.Othman, M.M.Ismail, H.A.Sulaiman, M.H,Misran, M.A.M.Said

International Journal of Engineering and Industries(IJEI) Volume3, Number4, December 2012 doi: 10.4156/IJEI.vol3.issue4.5

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Figure 1: Network Topologies

As in the implementation issue, there are two important types of systems that make fiber-to-the

home connections possible. These are active optical networks and optical networks which will explain in detail in the next sections.

2. Type of Optical Network

Generally optical cables only possess one general design, there are few types of system how the optical network works. The most common forms of optical networking are as below:

A. Active Optical Network (AON)

A system that need active configuration of such node in order to achieve the same result is called active optical network [3]. Active optical networks rely on some sort of electrically powered equipment in Optical Distribution Network (ODN) to distribute the signal, such as a switch or router. Normally, optical signals need O-E-O transformation in ODN. Each signal leaving the central office is directed only to the customer for which it is intended. Incoming signals from the customers avoid colliding at the intersection because the powered equipment there provides buffering.

As of 2007, the most common type of active optical networks are called active Ethernet, a type of Ethernet in the first mile (EFM). Active Ethernet uses optical Ethernet switches to distribute the signal, thus incorporating the customers' premises and the central office into one giant switched Ethernet network. Such networks are identical to the Ethernet computer networks used in businesses and academic institutions, except that their purpose is to connect homes and buildings to a central office rather than to connect computers and printers within a campus. Each switching cabinet can handle up to 1,000 customers, although 400-500 is more typical. This neighbourhood equipment performs layer 2/layer 3 switching and routing, offloading full layer 3 routing to the carrier's central office. The IEEE 802.3ah standard enables service providers to deliver up to 100 Mbit/s full-duplex over one single-mode optical fibre to the premises depending on the provider. Speeds of 1Gbit/s are becoming commercially available [4].


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Figure 2: Implementation of Active Optical Network (AON)

B. Passive Optical Network (PON)

PON (Passive Optical Network) is a point-to-multipoint optical network with no active elements in the signal path from source to destination. The only interior elements used in a PON are passive optical components, such as optical fiber, splices, and splitters. A PON employs a passive device (i.e., optical splitter/branching device, etc, that not requiring any power) to split an optical signal signals from multiple fibers into one. PON is capable of delivering triple-play (data, voice, and voice) services at long reach up to 20 km between CO and customer premises. All transmission in PON is performed between an optical line terminal (OLT) and optical network units (ONU). OLT resides at CO; while ONU is located at the end-user location. ONU is located at the end-user location The feature of PON is that ODN is built wholly of optical splitter, which is a kind of passive device and doesn't contain any electronic device or power supply. At present, PON that gradually used for commercial mainly include TDM-PON (including APON, EPON and GPON) and WDM-PON. EPON and GPON are most popular PON. [5]

Figure 3: Implementation of Passive Optical Network (PON)

C. Ethernet-based Passive Optical Network (EPON)

EPON (Ethernet-based Passive Optical Network) is a point to multi-point broadband access network based on the combination of Ethernet and optical fiber technologies. EPON has been considered as one of the most important technologies of broadband access. It carries data traffic in the form of Ethernet frames which is defined in the IEEE 802.3 standard. It uses a standard 8b/10b line coding and operates at standard Ethernet speed. 8b/10b refer to 8 user bits are encoded as 10 line bits. EPON is widely used in the access networks. It will solve the problem of aggravating lag of access network capacity which is coming with the substantial growth of the telecommunications backbone in recent years. What's more, the low-cost Ethernet equipment and low-cost fiber infrastructure make EPON appear to be the best candidate for the next-generation access networks. EPON supports voice, video and data access.[6]


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3. FTTH using OCDMA

FTTH will resolve the last mile bottleneck in between high-capacity metro networks and the customer premises of small-to-medium-sized businesses and residential customers. The cost either to implement or for network maintenance and repair is one of the crucial criteria for the access network. The passive optical network (PON)is one of the promising techniques to enable low-cost optical access. Very recently, another crucial criterion emerges in FTTH, that is, a capability of gigabit-symmetric both for the up and down link. Due to that, ATM PONs, Ethernet PON (EPON), Gigabit Ethernet, GPON (ITU G.984) and even to 10 Gigabit Ethernet PON won’t be able to provide a gigabit uplink.[8]

There are promising multiplexing techniques such as wavelength division multiple access (WDMA) and optical code division multiple access (OCDMA) to enhance the uplink capacity of FTTH. In WDM PON allows for the uplink to occupy a single wavelength. Although a wavelength is uniquely assigned to each channel of the uplink, however, the number of the wavelengths would be not sufficient for WDMA to accommodate even a moderate number of users.

Optical code division multiple access (OCDMA),early proposed in mid '70s, followed by experimental demonstrations in ’80s [9], has long remained outside the mainstream of optical communication R&Ds. OCDMA draws an analogy from the spread-spectrum wireless CDMA. By contrast to the frequency spread/despread, the time and/or optical frequency spread/despread technique is adopted in OCDMA. Having had current mature optical device technology, OCDMA now deserves revisit for a powerful alternative in FTTH systems. Optical code division multiple access (OCDMA) is one promising candidate for a new-generation broadband multiple access technique with some features such as full asynchronous transmission, low latency access, and soft capacity on demand. In particular, enhanced security is a frequently cited benefit of OCDMA techniques.[10]

4. FTTH : OCDMA Analysis Results and Discussions

The simulation has been carried out by using opt system software version 7. The system is represented by three sections: transmitter section, fiber link and receiver section. In the transmitter part, each of optical line terminal (OLT) consist of five components: Pseudo Random Bit Sequence (PRBS) generators, Non-return-to-zero (NRZ) pulse generators, White Light Source, Fiber Bragg Grating and Modulators . The function of pseudo random bit sequence(PRBS) generators is to generates a Pseudo Random Binary Sequence (PRBS) according to different operation modes. The bit sequence is designed to approximate the characteristics of random data. NRZ pulse generator is used to generate NON Return to Zero (NRZ) coded signal. The fiber Bragg grating (FBG) is used as a filter in encoder and decoder. The function of the encoder is to encode the source according to the specific code it uses.

The modulators are Mach-Zehnder modulators, which is an intensity modulator based on an interferometer principle. The signals that coming from the transmitter will be combined by power combiner and drive into a single fiber. The fiber link section includes the fiber cables used for transmission at 1550nmwavelength. In this system, the power splitter are used to representing the branches to the drop part on an optical network unit(ONU). At the receiver part it shows the equipment at the customer premises. The incoming signal is split into two parts, one to the decoder that has an identical filter with the encoder and the other to the decoder that has the complementary filter . Photo detector PIN used to performs conversion from optical to electrical domain. An electrical subtracted is used to subtract the overlapping data from the wanted one. The performance of the system referring to the bit error rate (BER) at BER analyzer.

The simulation is done using OptiSystem 7 to investigate the FTTH with 3 users. An Oscilloscope Visualizer is added after NRZ Pulse Generator to observe the signal generated. The modulated signal is observed using the Optical Time Domain Visualizer and the signal before combined is observed at the Fiber Bragg Grating with Optical Spectrum Analyzer. The


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result is shown as in Figure 5, 6 & 7. All three users are equipped with device with power of -115dBm and wavelength of 1550.5nm.

Figure 4: Project Layout of OSA FTTH

Figure 5: Oscilloscope Visualizer


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Figure 6: Optical Time Domain Visualizer

Figure 7: Optical Spectrum Analyzer


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Figure 8: Eye Diagram of User 1



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Users BER

1 1.07097e-022

2 6.79957e-024

3 1.01435e-016

Later, the system is examined without the Fiber Bragg Grading (FBG). The result is as below:


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Figure 11: Eye Diagram of User 1 (Without FBG)

Figure 12: Eye Diagram of User 2 & 3 (Without FBG)

Users BER 1 0.00896762 2 1 3 1


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Without the BRG, the signal received by User 2 and 3 have a high BER. This show that there is no signal received by user 2 & 3.The length of the fiber is varied to observe the effect of power loss that might cause serious problem to implementation.

Fiber Length

(km) BER

10 1.07097e-022 20 8.73454e-015 30 3.64609e-009 40 1.45063e-005 50 0.00299773

One of the feature of FTTH is when one of the source is disable, the received section with the corresponding side with not receive any signal. When optical source 3 is disables, the result below is shown:

Figure 13: Eye diagram of User 1 (Optical source 3 disable)


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Figure 14: Eye diagram of User 2 (Optical source 3 disable)

Figure 15: Eye diagram of User 3

User BER 1 1.52665e-0182 2.65098e-0233 1


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When optical source 3 is disabled, there is no signal received at User 3. In this simulation, we explain an optical code-division multiple access (OCDMA) structure using three users. The distance range was used is 10 km. This is the typical range of the fiber length in MAN environment. The distance was expected to influence the performance in two means such loss and dispersion. At low transmission rates, when the dispersion was not significant, the loss would be dominant.

In generally, a longer fiber will provide a larger dispersion and attenuation, thus the bit error rate (BER) will increase. For OCDMA system, as a result of the subtraction process, the systems will significantly compensate the dispersion effect. Thus the performances are limited by the fiber losses. The BER increased exponentially with distance. When the signal transmits is too weak and when it was reaches the far end of the system, the data will be difficult to separate from the noise. So this situation will cause the number of errors in the received data bits to increase. So, this problem can be solved by keeping the input power or the transmitter power to a maximum value.

The BER is reduced exponentially when the input power increased. By implemented OCDMA system, the performance can be improved by increasing the input power. A good signal received is when the data that be received was separate from the noise. Number of errors in the received data bits must be to decrease. The BER reduced exponentially when the value of the output power increased. The performance can be improved by increasing the input power, then the output power will increased, and BER value can be reduced. 5. Conclusion

This paper introduced the basic summary of what an optical network is. Optical networks have a big potential in bringing a better quality of communication in telecommunication field. Both types of optical networks have potential in particular condition. Active Optical Network (AON) requires active (electrically powered) devices to operate while Passive Optical Network (PON) requires passive devices (doesn’t require power) to operate. It has been shown that OCDMA is capable of providing a gigabit- or even multi-gigabit-per-second for each user both in the up- and downlinks, and scalable OCDMA over WDMPON could be one of the most promising FTTH network. Using OptiSystem we can explore the performance of different architectures for FTTH networks.

Multi-parameter scanning enables us to study trade-offs with respect to parameters of interest and to choose optimal designs for deployments. It also Enables us to analyze different algorithms for electronic equalization. BER Test Set enables simulation of bits for direct error counting. This paper significantly reduces product development costs and boosts productivity through a comprehensive design environment to help plan, test, and simulate optical links in the transmission layer of modern optical networks. 6. Acknowledgment

Authors would like to thank Universiti Teknikal Malaysia Melaka for supporting this project and also for financing this journal. 7. References [1] Mohammand, I. &Hussein T.M., “The Handbook of Optical Communication Network”, CRC

Pres, 2003. [2] Gerd K., Optical Fiber Communications, Fourth Edition, International Edition, McGraw Hill,

2010. [3] C.P. Larsen, A. Gavler, and K. Wang ; “Comparison of Active and Passive Optical network”,

IEEE journal, 2011 . [4] ITU-T Recommendation G.985, 100 Mbit/s point-to-point Ethernet based optical access system.


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[5] Zhan Mei, Dongsheng Zhao, Jihong Liu, “A Survey of Optical Networks and its Visual Management and Control”, Advanced Computer Control (ICACC), 2011 3rd International Conference, pp. 473-477, 2011.

[6] Ng, B., Ab-Rahman, M.S., Premadi, A., Jumari, K., “Portable Network Monitoring System for Passive Optical Network (PON)”, Computer Technology and Development, 2009. ICCTD ’09.International Conference, p. 176-180, 2009.

[7] M.M.Ismail, M.A.Othman, Z.Zakaria, M.H.Misran, M.A.Meor Said, H.A.Sulaiman, M.N.Shah Zainudin, M. A. Mutalib, “EDFA-WDM Optical Network Design System”, Malaysian Universities Conference On Engineering And Technology 2012 (MUCET2012) , UNIMAP, Malaysia, Accepted July 2012.

[8] M.A. Othman, M.M. Ismail, H.A. Sulaiman, M.H. Misran, M.A. Meor Said, Y.A. Rahim, A.N. Che Pee, M.R. Motsidi, “An Analysis of 10 Gbits/s Optical Transmission System using Fiber Bragg Grating (FBG)”, IOSR Journal of Engineering (IOSRJEN), Accepted July 2012.

[9] P. R. Prucnal, M. A. Santoro, and T. R. Fan, “Spread spectrum fiber-optic local area network using opticalprocessing”, J. Lightwave Technol., Vol.4, no.5,pp.547-554, May, 1986.

[10] M.M.Ismail, M.A.Meor Said, M.A.Othman, M.H.Misran, H.A.Sulaiman, F. A. Azmin, “Buried vs Ridge Optical Waveguide Modeling for Light Trapping into Optical Fiber”, International Journal of Engineering and Innovative Technology (IJEIT), Accepted July 2012.


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