What is PON technology and its generation

What is PON technology and its generation: First we try to know what is PON and why network operator use PON technology?We all know that in fiber optic, the data goes from one place to another in the form of light. Generally, two essential types active optical networks (AON) and passive optical networks (PON) used. In order to achieve the increasing demand for high-bandwidth broadband, network operators invest heavily in their access network.But the question arises, what is the PON network and why its importance?

Passive optical network is nothing alone, it is composite of other network components such as OLT and many others optical network units(ONUs).Understand in simple terms, PON refers to a technique that implements point-to-multi-structure architecture, which means that a single optical fiber serves many endpoints such as customers. PON simply describes the fact that optical transmission has no power requirements or active electronic parts when the signal is going through the network.

PON Technology

What is PON technology and its generation

PON Generations

Network operators are using today Gigabit Passive Optical Network (GPON) technology to extend fiber access to end-user customers. GPON satisfies the bandwidth needs of residential customers for some years to come and is the technology selected by many telecom operators. However, to get the most from their fiber networks, operators are challenged to go beyond the capabilities of GPON and find new ways to monetize and maximize their fiber infrastructure investments in the future.

PON First Generation

The first generation of PON responds to Time Division Multiplexing (TDM) PON architectures. TDM PON has been successfully deployed in a commercial basis by owing the following key enabling technologies:

➥Broadcast PON built with Optical Power Splitters.

➥High-speed burst mode transceivers.

➥Single wavelength for upstream traffic (1310 nm) and downstream traffic (1490 nm).

➥Direct detection (non-coherent).

➥Simple and cost-effective optical sources, especially in the ONT.

Two available standards describe current TDM PON generation
➥Gigabit capable PON (GPON), defined by ITU-T G.984.
➥Gigabit Ethernet PON (GE-PON), defined by IEEE 802.3ah.

PON technology

P2MP Technical tree

Full Service Access Network (FSAN) forum was the first initiative (hold in 1996) to define and share a common optical fiber access technology among vendors and network operators and still is the main meeting point for that purpose. The results of the FSAN activities are submitted to appropriate standard bodies for consideration, usually the International Telecommunication Union (ITU).

The first published standard ITU G.983, appeared in 1999, was a TDM PON described as APON because used ATM for multiplexing. Later on, FSAN designated as BPON an early enhancement which reserved some wavelengths bands for other systems. After BPON, there was a significant interest within the group in moving to higher speeds and also incorporating Ethernet, particularly Gigabit Ethernet. That resulted in GPON ITU G.984 in 2004, with improved performance up to 2.488 Gbps in downstream direction and splitting ratios of 1:64 and 1:128.

Working similar as FSAN, the Ethernet in the First Mile (EFM) group developed a new access network proposing several topologies for transporting Ethernet that were incorporated into a new standard IEEE 802.3ah GE-PON, also in 2004, which included a PON FTTH solution as well as P2P. In the downstream direction, information is broadcast to all end users in timeslots at a line-rate of 1.25 Gbps.

Despite that GPON was published in 2004 and generation of PON equipment is already available in the market, it is still the most deployed technology and seems to do not give way in the market to any of their successors yet. The principal barrier is that GPON is price-competitive and give plenty of bandwidth for today residential requirements.

NEXT GENERATION NG-PON1

Although passive power splitters bring many advantages to construct easily a PON network, the splitter insertion loss is a strong function of the number of supported users per feeder fiber, thereby constraining any possible increase in user count, reach, and/or average user data rate in GPON.

With the interest to overcome that issue, FSAN worked in the definition of the next generation PON, based in 10 Gbps transmission, so-called NG-PON1. With similar concerns, EFM started the definition of the next generation technology to upgrade GE-PON.

The efforts of FSAN and EFM leaded to the approval of two new TDM PON standards in 2009 giving shape to the Next Generation PON:

➥10 Gigabit capable PON (XG-PON1), defined by ITU-T G.987
➥10 Gigabit Ethernet PON (10GE-PON), defined by IEEE 802.3av

XG-PON1 supports an asymmetrical bandwidth capacity of 10 Gbps downstream and 2.5 Gbps upstream. Enhanced security and lower energy consumption were other key features introduced in this specification.

Both XG-PON1 and 10GE-PON allow backward compatibility and co-existence with the previous PON generation, enabling progressive upgrades with minimal operational impact on existing users.

NG-PON2 AND BEYOND

Since 2011 FSAN has been working towards proposing to ITU a new technical solution to be standardized for the future generation of PON systems, referred as NG-PON2. In 2012, based on the current application demands and technological maturity, it was decided that TWDM-PON would be the primary solution for NG-PON2 with an additional choice for P2P links based on WDM. The new standard is being compiled in the recommendation series ITU-T G.989.

TWDM-PON is a step forward in PON technology evolution, based in technologies which have a reliable state of maturity. The standards have been defined to allow GPON, XG-PON and NG-PON2 to coexist on the same fiber by using different wavelengths.

Trends for access PON technology over the next fi years will be towards more symmetrical bandwidth. Multimedia file sharing, peer-to-peer applications and more data-intensive applications used by home-workers will drive subscribers towards upstream bandwidth. Besides these, the main drivers behind the intensive usage of PON technologies will be Business Service, Mobile and Wi-Fi/Small cells backhaul networks that operators need to support beyond the residential services.

Advanced technologies are in review for what is expected to be an upcoming next generation NG-PON3. It may be considered a long-term solution and will likely require a change in components and physical layer technologies compared to today’s PON solutions.

PON technology generation chart

PON Evolution