Passive Optical Networks (PON)

1032 words (4 pages) Essay in Computer Science

26/07/18 Computer Science Reference this

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With the popularity of broadband services of the terminal users the demands for bandwidth in the access network is rapidly increasing. Rapid increase of global data traffic and massive deployment of new networks are becoming a key environmental, social and economic issue. The access network consumes about 70% of overall network energy. Passive Optical Networks (PON) has been considered to be one of the most promising solutions for access networks due to its immense bandwidth and low cost infrastructure. Wavelength Division Multiplexing Passive Optical Networks (WDM-PON) provides a solution for having longer and larger capacity networks comparing with existing PON systems which can meet the ever increasing bandwidth demand of next generation ac-cess networks. Moreover, the combination of Orthogonal Frequency Division Multi-plexing (OFDM) and WDM-PON technique is a subject of great interest to increase the system capacity and dispersion tolerance. Coherent detection OFDM method has more prominent performance than direct detection method. For the practical implementation of WDM-OFDM-PONs, low-cost Optical Network Units (ONUs) and Optical Line Termi-nals (OLTs) are of most critical importance, in particular, avoiding a wavelength-specific laser source at each ONU. To address this issue, wavelength reuse concepts such as Trav-eling Wave Semiconductor Optical Amplifier, Wideband Traveling wave SOA and Re-flective SOA have been implemented in WDM-OFDM-PON. Among these, RSOA per-forms better than the others. To further reduce the system cost a WDM-OFDM-PON architecture with simplified structure by using Vertical-Cavity Surface-Emitting Laser (VCSEL) as transmitter at OLT and ONU. All these simulations are done using OptiSys-tem 12.0 software.

The combination of an exponential increase in bandwidth-intensive applications and customer base, has resulted in the rapid increase of fiber networks in the access network segment in recent years. In terms of fiber access technology, the point-to-multipoint passive topology in the form of the Passive Optical Network (PON) has been proven to be beneficial to both customers and operators. Due to rapid increase of global data traffic and bandwidth demands, massive deployment of new network, is becoming a key environmental, social and economic issue. To address this issue, great effort has been ex-pended on researching the high-speed, cost-effective, flexible bandwidth allocation and future-proof Next Generation Passive Optical Network (NG-PON) system. Among these techniques, WDM based PON systems have attracted a great deal of research and devel-opment interest, due to their capability of providing cost-effective way for increasing the overall bit rate and transmission reach of networks.

The access network, also known as the first-mile network, connects the service provider Central Offices (COs) to businesses and residential subscribers. An access net-work is a part of a telecommunications network which connects subscribers to their im-mediate service providers. This network is also referred to as the subscriber access net-work, or the local loop. The bandwidth demand in the access network has been increasing rapidly over the past several years. Active Optical Network (AON), the first based access network has been characterized by a single fiber which carries all traffic to a Remote Node (RN) mainly electrically powered switching equipment such as a switch or a router that is placed close to the end users from the central office. In this AON architecture, later the active node is replaced with a passive optical power splitter/combiner leading to the development of Passive Optical Network (PON).

Optical Orthogonal Frequency Division Multiplexing (OFDM) technique has re-cently been a promising technique in access networks due to its high spectral efficiency and robust dispersion tolerance. OFDM, is a form of signal modulation that divides a high data rate modulating stream placing them onto many slowly modulated narrow band close-spaced sub-carriers, and in this way is less sensitive to frequency selective fading. Furthermore, the OFDM is widely considered as one of the strongest candi-date for WDM-based PON system, owing to its unique advantages of superior toler-ance to chromatic dispersion impairments, dynamic provision of multi-granularity band-width allocation both in time and frequency domains. WDM-OFDM-PON, combining the advantages of WDM and OFDM techniques, can provide higher data rate and more flexible bandwidth allocation for end users. Nonetheless, OFDM modulation modules, consisting of high-speed Digital Signal Processing (DSP) chips, Digital-to-Analog Con-verters (DAC), and E/O modulators, are needed for the generation of optical OFDM sig-nals in WDM-OFDM-PON. These components consume much more energy. Moreover, each OFDM modulation module is fixed for one Optical Network Unit (ONU) group in conventional WDM-OFDM-PON, which causes a rough granularity and wastes a large amount of bandwidth resource since the users do not fully utilize the network capacity all the time. Therefore, it is of great significance to design an energy-efficient and cost effective WDM-OFDM-PON system with high data rates compatible with large num-ber of users. This can be accomplished by using wavelength remodulation methods for bandwidth utilization and VCSELs for cost effectiveness.

Objectives of the Project

The main objectives of this project are:

Simulation and performance analysis of Wavelength Division Multiplexing- Or-thogonal Frequency division Multiplexing- Passive Optical Network (WDM-OFDM-PON) systems for different data rates

Simulation and performance analysis of Wavelength Division Multiplexing- Or-thogonal Frequency Division Multiplexing -Passive Optical Network (WDM-OFDM-PON) systems using wavelength reuse by

  • Traveling wave SOA (TWSOA)
  • Wideband TWSOA (WBTSOA)
  • Reflective SOA (RSOA)

Simulation and performance analysis of bidirectional WDM-OFDM-PON with dif-ferent transmission length and users using VCSELs

Report Outline

This report contains six chapters. Chapter 1 gives an introduction about the rel-evance of the project and also convey the main objectives of the project. The second chapter describes about the theories and literature survey of the project. This chapter begins with the basic access networks and describes the various terms relevant to the project. The terms like PON, WDM, OFDM etc are included. Chapter 3 describes the system model for the design. Here explains the basic block diagram representation of the major network technologies used. Chapter 4 explains the simulation procedures, platform used for simulations and details of each section and subsystem in the simulation process. Chapter 5 deals about the results obtained after the simulations and the major inferences got from these results. Sixth chapter concludes the project with findings followed by references section.

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