Introduction to Next-Generation FTTH Passive Optical Networks

Optical fiber access to user, the so-called Fiber-To-The-Home (FTTH), is becoming a mature concept along with a reality in lots of regions of the world, with more than 8 millions homes already connected, in an exponential growth. Because it is widely accepted, FTTH may be the only future-proof technology that’ll be able to support the upcoming interactive multimedia services, and nowadays operators are planning to substitute the existing telephone-line-based systems for example ADSL (Asymmetric Digital Subscriber Line) and POTS (Plain Old Telephone Service), or cable systems such as CATV (Cable Television), per optical fiber. First, point-to-point fiber links; recently, the greater advanced point-to-multipoint Passive Optical Networks (PONs) are now being deployed to implement FTTH – currently in Asia and USA mainly. The first generation PONs including BPON (Broadband PON), GPON (Gigabit PON), and EPON (Ethernet PON), have been recently standardized, offering symmetrical Gbit/s bandwidth typically shared among few tens of users.

Later on, further generations of PONs will be available (in the same manner as we have experienced multiple generations of Digital Subscriber Line, DSL) there will be drivers to deploy a number of them aiming towards higher capacity, less expensive, newer services and Quality of Service (QoS) diversification.

This short article focuses onto discussion from the technical options for next generation PONs (ngPONs) and is aimed at proposing and analyzing new architectures in addition to enabling technologies. True-boardband access (10/100 Mbps) may drive the telecommunications sector again towards relevant positions in terms of social and economic development. If operators can use a gradual upgrade-path for their infrastructure from a basic one that’s probably already deployed for an all-optical network, the development can be effectively done.

The main focus of the report is on very high-density scalable broadband-for-all access networks, for scenarios in which the scalability and the continuous development of the fiber network is a vital requirement for the operator strategic business plan. This may exist in fiber-limited or saturated areas and also where the long-term cost effectiveness drives a green-field deployment. Thus, current approaches like current point-to-point fiber-rich plants or standardized Time Division Multiplexed (TDM) PONs (GPON, EPON) are not extensively dealt in this particular text, which mainly concentrates on longer-term generations of PONs.

Research activities are focusing on possible extensions of current GPON and EPON as these systems are affected bandwidth limitations later on, and they don’t make use of the full optical bandwidth. Our prime initial capital expenditure needed in new FTTH deployments compels network designers and operators to make sure migration paths that guarantee future full usage of infrastructure investments, avoiding bottlenecks at any demand increase. Thus, the major goal would be to reduce the overall access nerwork cost while assuring an amazing symmetrical bandwidth per user, establishing an optical passive transparent infrastructure over a dense extended-range area, capable of supporting unknown future demands. This really is drving the research towards extended, practically-unlimited-bandwidth ngPONs. Time scale for migration of current PON systems towards it can be highly variable, perhaps in a 2-8 years timeframe, although driven by the mentioned unpredictable user demands. An array of operators and system vendors are aiming their R&D interests towards seo considering this.

Wavelength Division Multiplexing (WDM) technology straightforwardly offers a new dimension with this upgrade. The next implementation of ngPONs can be only foreseen if new cost-effective techniques and products are used, such as Fiberstore where you can get the best WDM optical networking solutions. WDM access could be pure-WDM-PON or hybrid TDM/WDM-PON; the second offers a higher-level of granularity and scalability, so it constitutes the main research focus (shown within the figure below). However, there are relevant barriers in the migration towards WDM in FTTH: the increased cost of WDM components in the access field and also the availability of technological solutions to guarantee the robust and unlimited use of the extended PON.


If, using the advanced techniques proposed, operators can realize the chance to highly scale their infrastructure, from a basic one already deployed, the extended development, when it comes to number of serced users, bandwidth and distance, may be effectively prompted. The fundamental scenario from the project is on scalable high-density broadband-for-all access, i.e. environments in which the scalability and the continuous growth of the fiber network are an essential requrement for the operator’s business plan. This may occur in fiber-limited or saturated areas, and also where the long-term cost-effectiveness validates a green-field deployment. Using the extended performances, if PONs can also incorporate resilience and intelligent functionalities of metropolitan networks, it’s possible to envisage an access-metro networks convergence within the long-term, which is becoming a new interesting concept for that integration and simplification of telecommunication networks.

Considering this, the main features that could define a very scalable ngPON may be the following:

  • High splitting ratio (>64)
  • High-speed (>1 Gbps)
  • High bandwidth per user (>100 Mbps)
  • Bidirectional (BIDI) transmission, symmetrical data rate, single fiber access
  • Long reach (>20 km)
  • Passive (no power need)
  • Simple upgradeability
  • Centralized management Dynamic resource allocation
  • Basic protection incorporated

Another indicate address is that some operators curently have a legacy PON problem and just how they will evolve from BPON/GPON/GE-PON to ngPON, when the network is going to be leaning fiber, so that ngPON will need to share fibers with legacy PONs. All those are questions not solved so far. In this case, there will be difficult technical challenges such as wavelength plan discussions. For example, if ngPONs can be deployed on separated fibers to legacy PONs, the style of the ngPONs is probably easier. It is extremely probable that different operators may have different situations.

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