IJRIT International Journal of Research in Information Technology, Volume 2, Issue 1, January 2014, Pg:72-76

International Journal of Research in Information Technology (IJRIT) www.ijrit.com

ISSN 2001-5569

Investigations on Design Issues for Metro Networks Migrating To 10gbps Sanjeev Kumara, Kamaljit Singh Bhatiab, Kulwinder Singhc a,c

Department of Electronics and communication, Bhai Maha Singh College of Engg., Sri Muktsar Sahib, 152026, India b

Department of Electronics Engineering, Sri Guru Granth Sahib World University, Fatehgarh Sahib, India

Abstract In this paper, we will investigate the issues at high data bit rate, particularly 10 Gbps (OC-192) systems in metro area ring networks. At higher bit rates, in addition to loss compensation, we may also need to consider the chromatic dispersion compensation. Different options related to dispersion and initial chirp will also be investigated.

1. Introduction Today's telecommunication networks support an ever-increasing mixture of statistical and deterministic data traffic [1-3]. Current networks rely on time division multiplexing (TDM) hierarchy, originally invented to be the most efficient multiplexing technique possible for 64-kb/s voice, but this architecture is not particularly suited to statistical data traffic. A router or ATM switch can connect into a dense wavelength division multiplexing (DWDM) transport network by mapping packets or cells directly onto a wavelength without the intervening use of a SONET or SDH TDM [4-6]. In effect, a TDM can be replaced with an optical DWDM, which can increase bandwidth utilization, facilitate networking, and reduce cost. DWDM can defer or completely eliminate the need for extra fiber, which is especially significant for providers who have a fiber-exhaustion problem, and it can easily coexist with today's SONET/SDH networks or with older fiber-optic terminals (FOTs) operating on asynchronous protocols. DWDM has already revolutionized the telecommunication industry by providing the infrastructure for long-haul optical networks. As the DWDM revolution moves into the metropolitan interoffice (IOF) and access networks, it will rely on the optical add/drop multiplexer (OADM) as its fundamental network element for metro optical networking. In this paper, we examine the market needs for metro optical networking; introduce the concept, network topology, and architectures for metro optical rings; and describe the key requirements that address the needs of service providers. We also discuss the components of the network and review the general requirements that will enable the next step in the evolution—extending the DWDM ring architecture to business access customers. Metro optical networking represents a unique opportunity for service providers to begin deploying a data-centric highbandwidth services infrastructure. A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities [7]. MANs can also depend on communications channels of moderate-tohigh data rates. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. MANs might also be owned and operated as public utilities. They will often provide means for inter networking of local networks. Our conclusions with the help of Simulative analysis of integrated Sanjeev Kumar, IJRIT

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IJRIT International Journal of Research in Information Technology, Volume 2, Issue 1, January 2014, Pg:72-76

DWDM and MIMO-OFDM system with OADM was done recently for optical-OFDM system and Monitoring and Compensation of Optical Telecommunication Channels [8-15].

2. Results, discussions and conclusions: For this case, the receiver sensitivity is -16 dBm which reduces the allowable loss to Lallowable to 13dB. Assuming a power of 3 dBm per channel, the amount of amplification needed in the ring is Grequired = - (3x13.5-3x3.8-(-16)-3) = 35.9 dB. We can again use the unity gain segment approach for power compensation. By using this approach, migration from 2.5 Gbps to 10 Gbps is easily done in terms of power budgeting since the total loss is not changed, even though the allowable loss is changed. In this case, the received power will be well above the receiver sensitivity. At high bit rates, GVD may become a limiting factor for the transmission distance. When the bit rate increased to 10 Gbps, GVD-limited transmission distance drops to 30 km for externally modulated sources and to 10.5 km for directly modulated sources. Figure 1 shows the eye diagram when the bit rate is 10 Gbps and transmitter power is 3 dBm/channel and directly modulated sources are used. Ever increasing transmitter power does not open the eye. In fact, the shape of the eye shows that pulse direction distortion is related to dispersion. In this example, we have used the unity gain segment approach, which means that loss in each fiber span and node is compensated immediately at the following node. For simplicity, in this paper, we have used the “Directly Modulated Laser Measured” model for directly modulated sources and set the alpha parameter to -5.

Figure 1 Eye diagram of channel 1 at node 4 when the transmitter power is 3 dBm and bit rate is 10 Gbps Therefore, at 10 Gbps bit rate, you have to use dispersion compensation. Total dispersion per 50 km span is around 16x50 = 800 ps / nm. This will require 10.25 km of dispersion compensating fiber (DCF) with D = -80 ps / nm / km for each fiber span. DCF can be used after each span, or total accumulated dispersion can be compensated at a certain point. To preserve the scalability of the network, and keeping in mind the dynamic structure of the metro traffic, it seems to be the best choice to distribute the dispersion compensation to every node. This will also ensure that dispersion experienced by dynamically routed signals will be compensated properly. Figure 2 shows the network layout when unity gain approach and per node dispersion compensation is used. In this paper, we again used directly modulated transmitters as described in previous sections. To find the optimum length for dispersion compensation, we swept the length of the DCFs from 13 km to 18 km. Figure 4 shows the simulation results in terms of Q factor when transmitter power is 3 dBm. As you can see from this figure, maximum Q factor is observed when the length of DCFs is about 18 km. You can also identify from this figure that there is +/2 km of tolerance for each DCF for a minimum Q factor of 6. Figure 5 shows the eye diagram when maximum Q factor is observed.

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IJRIT International Journal of Research in Information Technology, Volume 2, Issue 1, January 2014, Pg:72-76

Figure 2 Ring network layout when unity gain approach and per span dispersion compensation is used

Figure 3 Q factor vs. DCF length when directly modulated transmitter is used To investigate the effect of transmitter type, we have replaced directly modulated sources with externally modulated ones. The results are shown in Figure 5 in terms of Q factor for different DCF lengths. Maximum Q factor is observed when the length of DCF is about 14 km. Compared to the directly modulated transmitter case, this curve is broader and dispersion compensation tolerance is higher; 14 km for this case, which is related to initial chirp on the signal. The influence of the initial chirp on system performance will be investigated in the Negative dispersion fiber for Metro networks.

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Figure 4 Eye diagram at node 4 when per span dispersion compensation is used and DCF length is 16 km In the "lumped" dispersion compensation case, one DCF and an extra amplifier is inserted just before node 2 to compensate the total dispersion. Figure 5 shows Q factor versus DCF length at node 4 when directly modulated laser is used and transmitter power is 3 dBm. As can be seen from this figure, this configuration definitely improves the network performance compared to the uncompensated case, but is worse than the case with distributed compensation. In the case of lumped dispersion compensation, DCF length tolerance is about +/-1.5 where maximum Q factor is observed, DCF is 45 km, and maximum Q factor is about 6.2. Furthermore, this type of dispersion compensation is not suitable for metro networks in which the wavelength routing path cannot be estimated. For example, consider the path recovery schemes in a much more complex network with more than one ring. Depending on the structure of the network, one particular wavelength can follow a path that does not pass over the single dispersion compensation fiber in the network.

Figure 5 Q factor versus DCF length at node 4 when "lumped" dispersion compensation is used

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3. References [1] [2] [3]

G. P. Agrawal, Fiber-Optic Communication Systems, Wiley-Interscience, 1997. R. Ramaswami and K. N. Sivarajan, Optical Networks: A practical Perspective, Morgan Kaufmann, 1998. K. M. Sivalingam and S. Subramaniam, Optical WDM Networks: Principles and Practice, Kluwer Academic Publishers, 2001. [4] Sidney Shiba et. al., “Optical Power Level Management in Metro Networks”, NFOEC’01, 2001. [5] R. Ramaswami and K.N. Sivarajan, Optical Networks: A practical Perspective, Morgan Kaufmann, 1998. [6] Tarek S. El-Bawab et. al., “Design considerations for transmission systems in optical metropolitan networks”, Opt. Fib. Tech. 63, p. 213, 2000. [7] I. Tomkos et. al., Filter concatenation in metropolitan optical networks utilizing directly modulated lasers”, IEEE Photon. Tech. Lett. 13, p. 1023, 2001. [8]. Kamaljit Singh Bhatia, R. S. Kaler, T. S. Kamal and Rajneesh Kale, “Monitoring and Compensation of Optical Telecommunication Channels by using Optical Add Drop Multiplexers for Optical OFDM System” Copyright © 2012 De Grunter. DOI 10.1515/joc-2012-0001 [9]. E K. Singh Bhatia, T.S. Kamal, R.S. Kaler, “Peak-to-average power ratio reduction using coded signal in optical-orthogonal frequency division multiplexing systems” IET Optoelectronic., Elsevier Science. (2012), Vol. 6, Iss. 5, pp. 250–254, doi: 10.1049/iet-opt.2011.0089, Impact Factor-1.201 Available online at www.ieeexplore.ieee.org. [10]. Kamaljit Singh Bhatia, R.S. Kaler, T.S. Kamal, “DESIGN AND SIMULATION OF OPTICAL-OFDM SYSTEMS” Journal of Russian Laser Research, Springer Science+ Business Media (2012), Volume 33, Number 5, pp. 202-208, September, 2012, Impact Factor-0.7, Available online at www.springerlink.com [11]. K.S. Bhatia, T.S. Kamal, R.S. Kaler, “An adaptive compensation scheme-based coded direct detection optical– orthogonal frequency division multiplex (OFDM) system” Computers and Electrical Engineering 38, Elsevier Science(2012) 1573–1578, http://dx.doi.org/10.1016/j.compeleceng.2012.06.007, Impact Factor0.7, Available online at www.sciencedirect.com [12]. Kamaljit Singh Bhatia, R.S. Kaler, T.S. Kamal, Rajneesh Randhawa, “Simulative analysis of integrated DWDM and MIMO-OFDM system with OADM” Optik 124, Elsevier Science (2013) 117– 121, doi:10.1016/j.ijleo.2011.11.081, Impact Factor-0.5,Available online at www.sciencedirect.com [13]. Kamaljit Singh Bhatia, T.S. Kamal, “Modeling and simulative performance analysis of OADM for hybrid multiplexed Optical-OFDM system” In Press Optik,Elsevier Science (2013), http://dx.doi.org/10.1016/j.ijleo.2012.05.036, Impact Factor-0.5,Available online at www.sciencedirect.com [14]. Tarnveer Kaur and Kamaljit Singh Bhatia, “Impact of Initial Laser Phase Values on Soliton Transmission”, J. Opt. Commun.. Volume 0, Issue 0, Pages 1–4, DOI: 10.1515/joc-2013-0044, October 2013 [15]. Tarnveer Kaur and Kamaljit Singh bhatia, “effect of line coding on jitter and initial laser phase on q value in soliton transmission” optik - International Journal for Light and Electron Optics,Volume 125, Issue 2, January 2014, Pages 805–809

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