FTTx Primer

1. Why are we talking about FTTx?

1.1 Fiber Optics, the PC and the Internet

Since the development of fiber optic telecommunications, the personal computer and the internet, telecommunications needs and demands have changed significantly. It is primarily these three technologies that have driven advances in telecommunications services such as VoIP, HDTV and IPTV.

Fiber optic transmission cables in long-haul, metro core and metro access networks have enabled the delivery platform necessary for bandwidth hungry applications. Table 1 shows the bandwidth consumption for typical service applications in today’s households.

Table 1: Application Bandwidth Requirements
Application Bandwidth (Mb/s)

Single
Application

Typical Householda
MPEG-2 MPEG-4
Voice (per channel) 0.064 0.5
Web Browsing 1-2 5
SDTV (MPEG-2) 4-6 10  
SDTV (MPEG-4) 2   5
HDTV (MPEG-2) 20 20  
HDTV (MPEG-4) 10   10
Total   35.5 25.5

 a Includes: 3 phones, 2 PCs, 2 SDTV sets and 1 HDTV set.

1.2 Current Bandwidth Usage

To put our North American bandwidth usage into perspective, it is useful to compare it to usage worldwide. In his book FTTx PON Technology and Testing, Dr. Andre Girard, breaks down global bandwidth usage trends into three geographical categories:

  • European Market – Data. High costs have driven consumers away from access lines and towards cellular phones. Users watch substantially less television than other markets and typically have an internet connection.
  • Asian Market – Voice/Data. Much of this population does not have access to television, however dense populations and multiple-dwelling units (MDUs) have created wide availability of telephone and internet services. Currently China boasts over 100 million internet subscribers.
  • North American Market – Video/Voice/Data. In Canada and the United States, television remains the most widespread and most popular “vehicle of culture”. The colder climate and lower population density have also encouraged the use of the other in-home media. A typical North American home includes 3 or more telephones, 2 or more PCs, 2 standard definition TV’s, and 1 high definition TV.
1.3 Delivery of Service

In order to deliver these services to the household, a service provider requires bandwidth. Bandwidth is both a measure of volume and speed; typically measured in megabits per second (abbreviated Mb/s, Mbps, or Mbit/s) or gigabits per second (abbreviated Gb/s, Gbps, or Gbit/s). In terms of providing this bandwidth, a number of network technologies are available to the service provider (see Table 2). Some of these have been around for a long time and some of them are relatively new.

Table 2: Available Broadband Access Transport Technologies
Transport FTTN - Fiber & Copper FTTH - Fiber
ADSL VDSL PON
 Basic  +  2 2+  Basic  2 BPONa GPONb EPONc
Bandwidth
(Mb/s)
Max Down 3 8 15 20 13 26 52 30 100 622 2488 1000
Up  0.5  1  1  2  Symmetric 155 1244 1000
Shared
(down)
1x16                       ~80
1x32                   ~20 ~80 ~40
Max Reach (km) 3 3 6 1.5 1.5 1 0.3 1 0.3 20 10/20d

a Standard ITU G.983
b Standard ITU G.984
c IEEE 802.3
d With Forward Error Correction (FEC)

1.4 GPON FTTx as the Answer

As you can see, there are many different options, and beyond the data presented in Table 1.2, each has it’s own set of advantages and disadvantages in terms of CAPEX and OPEX. However, from a technical standpoint—and when considering typical consumer demand--we see that only about half of the options provide the necessary downstream bandwidth, and of those only GPON and EPON provide both the required bandwidth and the long reach. It is for these reasons that the majority of service providers in North America, and around the world, have chosen to standardize on GPON FTTx.

2. History of FTTx Development

2.1 FSAN: Full Service Access Network (1995)

In the spring of 1995, major telecommunications providers and system vendors formed the Full Service Access Network (FSAN) working group. The purpose of this group was to develop the body of documentation that would help to define the standards for the new fiber-to-the-home passive optical networks.

Following this, the US federal government, signed the Telecommunications Act of 1996 to “promote and reduce regulation in order to secure lower prices and higher-quality services for American telecommunications consumers and encourage the rapid deployment of new telecommunications technology.”

In 1998 the International Telecommunication Union’s (ITU) telecommunications standardization sector (ITU-T) in turn, created recommendation G.983.1 (APON) based on FSAN’s specification for asynchronous transfer mode (ATM)-based PONs.

2.2 FTTH Council (2001)

In 2001, the Fiber-to-the-Home Council was formed to “educate, promote and accelerate fiber-to-the-home” with primary objectives to “supply a consistent and accurate view of FTTH [and] promote FTTH market development.” This resulted in the Broadband Internet Access Act of 2001 (US Legislature) which provided financial incentives to firms that invested in the development of next-generation broadband equipment.

2.3 ITU-T GPON Standard (2003)

In February of 2003, as part of it’s Triennial Review, the Federal Communications Commission removed the obligation for ILECs to allow CLECs to use their network infrastructures. This provided the all important incentive for service providers to invest in last-mile or local loop fiber infrastructure, without fear of having to share it with competitors—investment in FTTx was set to take off.

2.4 North America’s PON Explosion (2004)

In 2004 Verizon, SBC and Bellsouth kicked off a massive FTTH deployment in the United States, with what became known as the “Super RFP”. Equipment manufactures kicked into high gear, developing technology platforms for FTTx PON while OSP manufacturers began developing cabling, connectors and passive optical components in a race to bring products to market and capture market share.

2.5 FTTx in Canada

FTTx has been slow to develop in Canada. The most obvious reason being our dense population in urban centres coupled with the strong competition between cable-TV and telephone service providers (both with widespread penetration) which means that Canadians have been well served in the broadband services industry and have had less of an appetite for last mile solutions such as FTTx.

However, all this is about to change. As we’ve seen from Table 1.2, even the most robust, copper based broadband access transport technologies cannot support the bandwidth requirements of projected consumer demand. In addition to this, new standards for FTTx PON have “greatly increased the design commonality, capacity, survivability, security and versatility of PONs, opening the opportunity for mass economy of scale and tremendously lower costs that were not conceivable before.”

FTTx PON services can now be offered by many different types of service providers, including:

  • ILECs
  • CLECs
  • RLECs (rural local exchange carriers)
  • utility companies
  • municipalities
  • developers

3. FTTx Technologies

3.1 Copper vs. Fiber Optics

There is little point in doing a systematic comparison of copper vs. fiber. Fiber is clearly the superior transmission medium. Copper technologies continue to exist primarily based on the availability of existing copper plant. The development of singlemode optical fiber, with its nearly unlimited bandwidth has unlocked the possibilities for massive deployment of long-haul and metro point-to-point (P2P) fiber optic networks—resulting in three important changes:

  • Huge capacity increases
  • Substantial cost reductions in equipment, operations and maintenance
  • Significantly improved quality of service (QoS)
3.2 FTTN vs. FTTP

Again, the comparison of a fiber-to-the-node network versus that of a fiber-to-the-premise network, based on technology alone, is trivial, since the network that provides fiber directly to the customer is clearly superior. However, the decision between the two is really a decision between short-term and long-term planning.

As we can see from Table 1.2, many FTTN network configurations can support the bandwidth requirements of today’s typical user. In terms of short-term investment, the FTTN network remains a strong option, because of their lower CAPEX. We have not yet seen a “killer app” that will consume the kinds of bandwidth made available on FTTP networks. However, it is a question of ‘when’ not ‘if’, and in the long-term, when we do see bandwidth demand increase above that of today, FTTP will become the only option.

Additionally, it is also important to note that as research and development continues to heat up, the resulting cost reductions in FTTP and PON technology could easily eclipse the cost advantages of FTTN’s and supplant last mile copper solutions ahead of even the shift in bandwidth demand.

3.3 P2P vs. P2MP

The last major technology advancement in FTTx networking has been the introduction of passive optics which spawned the passive optical network (PON) that has opened the door to point-to-multipoint (P2MP) connections. Any FTTx network connection requires an optical line terminal (OLT) on the CO side of the connection and an optical network terminal/unit (ONT/ONU) on the customer side of the connection. Because OLT’s are expensive and require power to operate, this has been a significant component of the cost per connection. In a P2MP scenario, using PON, a single OLT can be used to connect to multiple (usually 32 or 64) ONTs/ONUs by way of PON splitters in between the CO and the customer. This creates significant cost savings by eliminating (a) a huge amount fiber that would otherwise need to be installed between the CO and the PON splitter, and (b) electronics required to add customers to the network.

Table 3: PON Standards
PON Type APON BPON GPON EPON 10GEPON
Name ATM PON Broadband PON Gigabit PON Ethernet PON 10 Gigabit Ethernet PON
Standard ITU G.983 ITU G.983 ITU G.984 IEEE 802.3ah IEEE 802.3av
Description This was the first passive optical network standard. Based on APON, it adds support for WDM, dynamic and higher upstream bandwidth allocation, and survivabilty.  It also created a standard management interface, called OMCI, between the OLT and ONU/ONT, enabling mixed-vendor networks. An evolution of the BPON standard.  It supports higher rates, enhanced security, and choice of Layer 2 protocol (ATM, GEM, Ethernet). Standard for using Ethernet for packet data.

10GigEPON will likely multi-lamda downstream and continue to use a single lamda with ATDMA for upstream.

It will also be WDM-PON compatible.

Notes Used primarily for business applications. Currently the most widespread network type in use today. In early 2008, Verizon is in the process of installing millions of lines, while British Telecom and AT&T are in advanced trials.   10Gbit/s backwards compatible with with 802.3ah EPON.
References

ADC Telecommunications Inc. The Book on FTTX, From Design to Deployment: A Practical Guide to FTTX Infrastructure. Ed. Steve Grady. Minneapolis, MN: 2005.

Girard, Andre. FTTx PON Technology and Testing. Quebec City: QC: EXFO Electro?Optical Engineering Inc., 2005