View of WDM-GPON: A VIABLE ALTERNATIVE FOR NEXT GENERATION FTTX ON THE EVOLUTION OF GPON-BASED FTTX SOLUTIONS

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Research Paper

WDM-GPON: A VIABLE ALTERNATIVE FOR NEXT GENERATION FTTX ON THE EVOLUTION OF GPON-BASED FTTX SOLUTIONS

1Mukesh Gupta

2Anand Swaroop Khare

3Uttam Mishra

1Research Scholar, Department of Electronics & Communication, OIMT Damoh

2Asst. Prof , Department of Electronics & Communication, OIMT Damoh

3Asst. Prof , Department of Electronics & Communication, OIMT Damoh

Abstract— There has been phenomenal growth of information traffic volume because of exponential growth in number of Internet users and continued development of new bandwidth demanding applications. This has motivated the need for implementing high capacity next generation networks. Optical fiber communication has been the key technology for the backbone network infrastructure. For local distribution Gigabit capable Passive Optical Network (GPON) is becoming an attractive alternative for meeting the higher bandwidth demand due its low cost and resource efficiency. Fiber based access networks have shown the capacity to meet the ever increasing demand for the bandwidth.

Passive Optical Networks has emerged as the key technology for the last mile.

Fiber-To-The-x (FTTx) is becoming extremely useful throughout the world. In this paper we review and compare the current GPON-based FTTx solutions, ATM-PON (APON), and Ethernet PON (EPON), and provide a possible evolution scenario to future WDM-GPON/ and present WDM-GPON as a viable solution for next generation FTTx.

Index Terms— Fiber Optics communications, FTTx, GPON, PON, WDM.

I. INTRODUCTION

Recently the optical fiber is becoming the most advanced transmission medium and next generation services can only be supported on fiber. The optical fiber when used as last mile offers many advantages such as higher bandwidth, longer distances between the central office to the end user, the more resistance to electromagnetic interference, increased security, reduced signal degradation etc. In addition, use of PON technology results reducing the initial investment, lower power consumption, less space, fewer points of failure due to the elimination of repeaters and optical amplifiers.

The rapid advancement in broadband applications such as HDTV (high definition

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING Available Online: www.ajeee.co.in Vol.01 , Issue 01, May 2016 , ISSN -2456-1037

To make the aforementioned possible maximum services must be offered economically. To allow faster connections, the optical fiber gets closer and closer to the subscriber. Fiber to the Home FTTH appears the most suitable choice for a long term objective: if the clients are wholly served by optical fibers, it will be easier to increase the bandwidth in the future [1]. FTTH is becoming long term future solution for providing broadband services such as Video on demand, Online Gaming, HD TV and VoIP.

Passive optical network (PON) based FTTH access network is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 32–128 [10]. These networks exploit the low attenuation (0.2–0.6 dB/km) and high bandwidth (>30,000 GHz) of single mode optical fibers to provide many times more bandwidth than currently available with existing broadband technologies.

Several Time Division Multiplexing TDM PON technologies have been standardized for FTTH deployments. The main disadvantage of TDM PON is that it not possible for different operators to physically share the same fiber. A multi-fiber deployment is necessary to physically share the access network [2]. The Wavelength Division Multiplexing (WDM) technology makes it possible to deliver the best solution in which the Dense Wavelength Division Multiplexing (DWDM) can be used for long distance networks and Coarse Wavelength Division Multiplexing (CWDM) for access networks and metropolitan areas as ideal solution on the basis of the tradeoff between the cost of elements and the number of services offered. WDM-GPON provides integrated Data and voice services up to 10 Gbps.

In this paper we focus our discussions on GPON based FTTx solutions. First, in Section II we review two current Time Division Multiplexing (TDM)-based PON solutions, APON and EPON, and summarize their advantages and disadvantages in various aspects. Then in Section III we discuss a possible evolution scenario from APON/EPON to WDM-GPON with issues to be addressed at each step of the scenario.

Section IV concludes this paper.

At the forefront of PON development there have been two separate approaches that appear to compete for next-generation systems: 10 Gbps PON (be it 10G EPON or 10G GPON), and WDM-GPON. Each approach has its own advantages and its own issues, but the progress with both new technologies has accelerated in recent years. In this paper we will focus on WDM-GPON, and examine some of the challenges and new technologies that are making this technology a very viable competitor for next-generation platforms.

2.WDM GPON: RESULTS

In this paper , we will be discussing the results obtained from simulation using

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OptiSystem 11.0. The results which we are going to consider are the eye diagram, the quality factor, the Bit Error Rate (BER) and the decision threshold as a function of the width of the bit. First let’s see results of downstream and then upstream results.

The eye diagram is a useful tool for the qualitative analysis of signal used in digital transmission. It provides at-a-glance evaluation of system performance and can offer insight into the nature of channel imperfections. Careful analysis of this visual display can give the user a first-order approximation of signal-to-noise, clock timing jitter and skew, pulse rise time, and also helps us calculate extinction ratio, Q-factor, and laser chirp. [10]

The vertical axis of eye opening that we see as the height of eye diagram shows the ability to distinguish between a bit “1” or bit “0”. While the horizontal axis of the eye opening shows the time period over the signal that can be sampled without any error. The wide and large of eye opening better for the transmission system performance.

In telecommunication system, the bit error rate (BER) is the percentage of bits that have errors relative to the total number of bits received in the system. For example, a transmission might have a BER of 10-9, meaning that, out of 1,000,000,000 bits transmitted, one bit was in error. The BER is a note of how often data has to be retransmitted because of an error. High BER may indicate that a slower data rate would actually improve overall transmission time for a given amount of transmitted data since the BER might be decreased, lowering the number of packets that had to be present.

The Q-Factor is suitable and acceptable in the performance analysis because it provides a qualitative description of the receiver performance. The Q-Factor is relatively easy and functions of the signal to noise ratio in optical. The Q-Factor is related to the BER with the relationship suggest the higher the value of Q-Factor, the better is BER. The Q-Factor can be expressed in dB or in linear. To expressed the Q-Factor in dB, its use the factor of 20 or (QdB= 20log Q). Must be noted that the Q-factor in linear is unit less.

2.1 Results of Downstream

Figure 2.1 below shows the results obtained from first ONU located at the HOSPITAL Block:

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Figure 2.1 : WDM GPON – HOSPITAL ONU Results

It shows that the eye opening is large and wide. The shape of eye diagram, eye height, value of Max Q Factor, BER and threshold obtained from above graphical results suggest that the design works and is feasible to implement.

Next is the BUSINESS block. It has two ONUs and the signal covers the same path to them since the last fiber has the same dimensions. So the results are identical and are given in Figure 2.2 below:

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Figure 2.2: WDM GPON – BUSINESS ONU Results

It shows that the eye opening is large and wide. The shape of eye diagram, eye height, value of Max Q Factor, BER and threshold obtained from above graphical results suggest that the design works and is feasible to implement. The results and conclusion are same for the other ONU.

Let us now look at the RESIDENTIAL Block which has 20 ONU's. Since display of the results of the 20 ONU's will require a lot of space, we shown only the results of the closest ONU (located at 50 meters from the splitter) and the farthest ONU (situated at 185 meters from the splitter). The results are as shown in the Figure 2.3 and 2.4 on the next page:

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Figure 2.3: WDM GPON – RESIDENTIAL ONU1 Results

Figure 2.4: WDM GPON – RESIDENTIAL ONU2 Results

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The results are almost similar the results of the ONU placed on the shortest fiber are a bit better than the results of the ONU at the end of the longest fiber.

The shape of eye diagram, eye height, value of Max Q Factor, BER and threshold obtained from above graphical results suggest that the design works and is feasible to implement. The results and conclusion are same for the other ONUs. Next block to consider for results is the SCHOOL-MALL Block, which has two ONU’s. The results for the two ONU's are shown in Figure 2.5 and 2.6 on the next page:

As in the earlier case, the only difference between the two signal paths is the last section of optical fiber, which in one case is 100 meters and in the other case, is 250 meters. Therefore, the results are very similar.

Figure 2.5: WDM GPON – SCHOOL-MALL ONU1 Results

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Figure 2.6: WDM GPON – SCHOOL-MALL ONU2 Results

The last block in downstream to be considered is BUILDINGS Block. As we have seen in the case of the business block, in this case also the paths that the signal covers are identical, so both ONU's offer the same results as shown in Figure 2.7 below:

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Figure 2.7: WDM GPON – BUILDINGS ONU Results

2.2 Results of Upstream

For the upstream, the results obtained at the OLT receiver are shown in Figure 2.8 below:

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Figure 2.8: WDM GPON – OLT ONU Results

Putting to gather all above results demonstrate the quality of design in both upstream and downstream and suggest that complete design works and is feasible to implement.

3.CONCLUSION

In this concluding chapter we are presenting on the one hand summary of work carried out in this dissertation, and on the other hand the conclusions based on the simulation results.

It is a fact that Optical Fiber Communication has been the key technology for the backbone network infrastructure due to its capacity and longevity. The detailed description of optical networks is required for proper understanding of FTTx networks and to undertake a particular design of WDM GPON. In this dissertation we have discussed various types of FTTx networks, General architecture of FTTH network, P2P and P2MP configurations, generic operation of PON, various network elements of PON.

For further understanding we have presented the operating principles of PON for both the uplink and downlink. We have then presented the advantages and disadvantages of PON, comparison between PON and active optical networks (AON) thereby concluding that PON design is optimal for exploitation of high bandwidth and lower implementation costs. After selecting PON as the best option, we then go on describing

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various PON technologies and their comparison on advantages and disadvantages, thereby choosing WDM-GPON as the best option due to its high speed, greater reach and support for number of users.

We then move on to discuss the considerations of designing the FTTx network and explaining the services that the different areas of the proposed fictitious environment require. After defining the environment we move on to the network planning. In this section each block of the fictitious environment has been physically described and analysis of the bandwidth requirement to meet the needs of all customers in each area has been carried out.

After describing each block area we have looked into all the network components which are required for the implementation of the network, such as the OLT and the ONU's (which are to be chosen by the operator who will manage the network), cable types to be used as per ITU-T standards, the type of connectors for the proposed network and size and location of optical splitters. We have put forward the arguments in each case why the selection and how many will be needed taking into account the future requirements and redundancy. Once we got the clear picture about the proposed distribution network and all the components needed for its implementation, it was time to select a simulation program that fulfils the design requirements. In this dissertation we have chosen the OptiSystem 11.0 simulation software, as it meets all our requirements.

We have then carried out the final design of the proposed network on the simulation software and conducted the run of the simulation and obtained the results of the simulation. We have presented the snapshots of design simulation and results.

The images have been discussed in detail both for upstream and downstream for the 5 areas of our chosen fictitious environment. At last we have discussed the results obtained for each of the ONU's. For analysis of the quality of the network we have taken into account the eye diagram, the quality factor, the BER and the decision threshold for the minimum BER.

The areas which have been covered by this network are huge hospital, university, business buildings and residential houses, residential buildings and school and Mall area. Flexibility is one of the advantages of the fiber optic design with varied length and bit rate of 2.5 Gbit/s for varied areas that will provide services such as broadband Internet access, teleworking, high definition television (HDTV) and broadcast. The opening and shape of eye diagrams, the quality factor and the bit error rate (BER) show that the performance of the network is within acceptable limits. Hence, the objectives defined for this dissertation has been successfully achieved.

In the worst case of the farthest house in the residential area a BER of about 10^-12 has been achieved. This shows the high reliability that will be achieved in each of

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Recommendation and Future Scope:

It is felt that local access networks based on the PONs will be prominent as this technology is developing very fast and the cost per consumers is very low. As number of HDTV channels, number of internet users, applications requiring high bandwidth are growing at a very fast pace more and more bandwidth capacity systems are required to be developed.

This is motivating fast development of FTTH technologies with Higher and higher speeds based on WDM and WDMA. Although the WDM GPON technology is still in laboratory phase for FTTH, it may be available in the market very soon. Compared to other proven technologies such as DSL, FTTH offers much higher bandwidth.

Although the objectives of this research have been achieved, there are still other research opportunities to be investigated. The introduction of PONs with WDM access is a huge area for research. Networks could have OLTs with dynamic allocation of timeslots and wavelength to the ONUs. This will increase complexities and thereby require newer bandwidth allocation algorithm.

Further study can be done using different simulation tools for the proposed FTTH architectures to estimate the performance for larger systems under different conditions and network parameters.

REFERENCES

[1] M. Chardy et al., “Optimizing splitter and fiber location in multilevel optical FTTH network,”

European Journal of Operational Research: Elsevier B.V, pp. 430-440, May 2012

[2] International Telecommunication Union (2003). Gigabit-capable Passive Optical Networks (GPON):

Physical Media Dependent (PMD) layer specification. ITU-T Recommendation G.984.2.

[3] Sairam, K. V. S. S. S. S. (2007). Optical Communications. Laxmi Publications Chapter1, pp. 1.

[4] Keiser, Gerd (2006). FTTX concepts and applications. John Wiley & Sons, Inc.

[5] White Paper: Broadband Access Technologies

http://www.ftthcouncil.eu/documents/Publications/DandO_White_Paper_2_2013_Final.pdf [6] www.genexis.eu/medialib/323/whitepaper-ftthnetworks.pdf

[7] FTTH Council Europe (2013). FTTH Business Guide.

http://www.ftthcouncil.eu/documents/studies/FTTH_Business_Guide_2013_V.0.pdf [8] Lam, Cedric F (2007). Passive optical networks: principles and practice. Elsevier Inc.

[9] The Product Group LLC. 10G GPON Tutorial.

http://www.fttxtra.com/ftth/10g-gpon-brief-overview/

[10] Sameer Ashfaq Malik (2008). 10G EPON- Unleashing the Bandwidth Potential. ZTE White Papers.

[11] Telecom and networking communications today. OF Cable: Fiber on a rollout.

http://www.communicationstoday.co.in/oct2007/of-cable-fiber-on-a-rollout-3159-154.html [12] http://en.wikipedia.org/wiki/Optical_fiber_connector