GPON or Gigabit PON technology began to be introduced relatively recently. Let's figure out what became the prerequisites for the emergence of GPON technology, what prospects it has, and also compare it with competing technologies - PON and GEPON.
2014 will mark the 45th anniversary of the first computer communication session conducted in the United States at a distance of about 640 km. This event is considered the beginning of the birth of the Internet. True, the ARPANET network, which preceded the World Wide Web, at that time was accessible to a very narrow circle of people and organizations. Connecting to it for lucky “outsiders” who have computers became possible only in 1991. It was only the appearance of the NCSA Mosaic web browser in 1993 that provided the prerequisite for the explosive growth of the global Internet audience. So the history of the “mass Internet” as of 2013 is only 20 years old.
In the first decade of the development of the global network, among the users who paid attention to such an indicator as “communication channel capacity (data transfer rate in bits)” or the associated characteristic “bandwidth”, there were “a few” people familiar with the theoretical foundations of radio engineering . And today everyone is talking about “Internet speeds”. And everyone wants to have “high-speed Internet” at their disposal.
Why high-speed? And where is the limit from which Internet access can be considered “high-speed”?
The mass user associates Internet speed, first of all, with the time intervals for downloading “heavy” video, music and graphic files, the number of which on the Internet is growing exponentially, and they themselves are becoming “larger”. Corporate consumers of online services (and more recently also cloud services) need high speed response to requests in the business management systems they use.
This means that high-speed Internet is an urgent need, and not a whim (both for “users” and for the same with which high-speed Internet begins, today, according to experts, it passes at the level of 10 Mb/s.
"Optics" is replacing "copper"
The Worldwide Computer Network began to develop on the basis of existing telephone lines using xDSL technologies. The most “advanced” version of this “copper” family - ADSL2+ modem technology provides an incoming stream speed of 24 Mb/s (outgoing - 1.2 Mb/s). Currently, it is the undisputed leader in the number of connections in all countries of the world. However, “copper” communication lines, laid decades ago, are becoming obsolete both physically and morally and are gradually being replaced by FTTx optical networks, the use of which makes it possible to increase the speed of information exchange on the Internet by two orders of magnitude. And in the near future - even more.
Over the last five years, the process of replacing copper cable routes with optical ones has been increasing and, according to analysts, in another five years the “optics/copper” ratio in telecommunications will radically change in favor of “optics”.
The FTTx (Fiber to the x) architecture is a section of a fiber optic communication line connected on one side to an OLT (Optical Line Terminal) transceiver station installed at the operator, and on the other - to the subscribers’ transceiver modules - ONT (Optical Network Terminal) or ONU (Optical Network Unit) .
ONT is a personal use terminal (also called an optical modem) installed in an apartment. ONU - designed for installation in the distribution cabinet of an apartment building and has several ports for connecting computers, televisions, telephones located in neighboring apartments.
ONTs and ONUs convert optical signals received from the OLT into electrical signals (sent, for example, to computers, televisions, telephones), and also perform the reverse conversion of electrical signals received from user terminals into optical signals that are sent to the OLT.
If splitters (passive signal splitters coming from the OLT) are introduced into a section of the optical line and ONTs are connected to their outputs, then such a transition from a single-fiber FTTx structure to a tree structure will lead to the formation of a passive optical network - PON (Passive Optical Network).
The work of PON is to organize multiple access through a single optical fiber through time division multiplexing access (TDMA) and frequency division of reception and transmission paths (Wavelength-Division Multiplexing - WDM). WDM multiplexers operating as part of OLT and ONT separate forward (incoming) and reverse (outgoing) signals, broadcast at different wavelengths (forward - 1.49 microns, reverse - 1.31 microns). To these streams can be added a cable television signal transmitted at a wavelength of 1.55 microns.
The first seeds of PON technology appeared about 15 years ago, and since then, the International Telecommunication Union (ITU) has released five standards for data transmission over optical fiber. Active equipment manufactured in accordance with the requirements of these standards provides speeds from 155 Mb/s to 2488 Mb/s. The features of these standards will be discussed below, but for now we emphasize that the advantages common to all types of PON technologies are the ability to easily expand the subscriber base, its maintenance and modernization, as well as low (compared to “copper” technologies) operating costs.
GPON: the driving force behind the standard
The first standard of the PON family - APON (ATM PON) was approved by the Ministry of Energy at the end of 1998, and the following year American and Japanese telecom operators began building passive optical lines. Data transmission according to this standard is carried out on the basis of the ATM protocol, which describes a switching and multiplexing method based on data transmission in the form of fixed-size cells (ATM cells). Data transfer speed – 155 Mb/s.
The introduction of new technologies into APON, in particular, dynamic bandwidth assignment depending on applications, support for SDH, FE, GE, SDI PAL, El, E/FE and telephony protocols, provided additional functionality in the areas of voice broadcasting, various video content and television broadcasting (the first appearance of a third wavelength in PON). This led to the approval of APON’s “daughter” standard – BPON (Broadband PON). At the same time, the data transfer speed increased to 622 Mb/s.
The next “link in the chain” of APON - BPON was the GPON ( Gigabit- capable Passive Optical Network) , the implementation of which ensures the network operates in both symmetric and asymmetric modes. The second mode is most often used, in which the data transfer speed in the forward stream reaches 2.488 Gb/s, and in the reverse stream – 1.244 Gb/s (usually these numbers are rounded and spoken of 2.5 Gb/s and 1.25 Gb/s).
Typically, a home PC is connected to an optical modem (ONT) of a GPON network either via twisted pair cable or wireless connection (Wi-Fi). The ONT also has ports for connecting a TV and VoIP phone.
The basic protocol in GPON technology has become GFP (Generic Framing Protocol), although TDMA, SDH, Ethernet, and ATM recommendations are also used.
In parallel with the improvement of PON technologies in the world, the development of optical Ethernet networks took place and the achievements of this communication “branch” in the field of high-speed data transmission were used in the EPON (Ethernet PON) standard, which was developed based on the MPCP (Multi-Point Control Protocol) protocol, managing multiple nodes. And its improved version - GEPON (Gigabit EPON) in its characteristics and capabilities today is second only to the undisputed leader of PON technologies - GPON.
What “catches your eye” in the above mini-review of technologies used in passive optical networks? – The fact that the differences in their functionality are mainly due to what data transfer protocols form the basis of the standards.
Is it worth switching to Gigabit PO
Let's consider whether it is necessary to switch to updated GPON technologies. Most experts believe that this technology is a truly profitable proposition. High channel power makes it possible to connect more functions and additional options. Everything you use - the global network, television, security alarms - requires a high-speed and secure connection.
GPON and GEPON: simple arithmetic
If numerical indicators (or even descriptions) are known that express any characteristics of the objects that need to be compared, then such a comparison is quite simple to make by placing the corresponding numbers in a row or column. And it will immediately be clear “who is better than whom.” Let's make this comparison between GPON and GEPON.
So, the forward transmission speed of GPON is 2.5 Gb/s, and that of GEPON is 1.25 Gb/s.
The maximum number of subscriber nodes per fiber for GPON is 64, and for GEPON - 16, which leads to a lower cost of port per subscriber in an operator's optical terminal manufactured according to the GPON standard, and significantly lower power consumption by station equipment than when using operator equipment GEPON standard.
Bandwidth utilization using GPON technology is no less than 93%, and using GEPON technology is no more than 60%. This difference is due to the fact that active GPON equipment uses GEM (GTC Encapsulation Method) frame fragmentation technology, which increases the efficiency of bandwidth use. GEPON technology does not have such a tool.
That's all the “simple arithmetic” that explains the popularity of GPON.
How to configure equipment when connected via GPON?
Setting up GPON at Rostelecom is not done by the user; only the ability to set up a wireless network on some terminals is available. There are no administrative rights to access ONT due to the specific operation of the equipment.
Most often, individual services are tied to a specific port on the optical terminal, and it is usually not possible to change this, only in some cases this is done through technical support. What can the user configure?
You can set up a Wi-Fi network, change the network name and password, channel and other parameters.
If you require more flexible configuration, then it is better to connect your router and configure all the necessary parameters. The provider's technical support will appropriately change the operating mode of the ONT so that it acts as a bridge for signal transmission, and the Internet session will be served by the router via a PPPoE connection. In this case, the restrictions imposed on the ONT configuration will not apply in any way.
When connecting additional devices (phones, TV set-top boxes, security alarms), ONT is configured by the provider. To do this, at the time of connection, a call is made to the appropriate technical support department. This is usually done directly by the specialist responsible for connections.
GPON: house wiring cables
The GPON network consists of trunk and distribution lines. The length of GPON backbone routes currently reaches 20 km (in the coming years, the developers of GPON technology promise to increase the maximum length of backbone optical fiber to 60 km). Trunk sections are laid (more about laying fiber optic cable) using traditional methods of aerial or underground laying of optical cables with a protective sheath, which ensures the longevity of the cable line in conditions of high humidity and temperature changes.
For GPON distribution infrastructure, created, for example, within an apartment building, drop and riser cables are used. A feature of “storey” drop cables, intended for branching an optical line from an overhead distribution cable, is the possibility of “flexible” routing with small bending radii provided by their design.
Riser cables used for vertical interfloor wiring contain 6-12 optical fibers, which are easily laid in cassettes, and their welding requires significantly less time than when welding optical fibers of other types of cables.
Self-connection: possible or not
The subscriber will not be able to connect himself. The following reasons are noted:
- The fiber optic cable is laid into the house or apartment by the provider's installers. They will install an outlet from which the terminal will be connected using a patch cord.
- Station OLT terminals work only with a specific list of supported ONT routers. When purchasing independently, there is a high probability that the subscriber will purchase an unsupported device - it will not work on the line.
- Most telecom operators providing access to the Network via fiber optic technology have implemented a system for automatic configuration of subscriber modems - ACS. But if the device is not on the list of supported ones, then it will not be able to be adjusted automatically.
GPON: the speed of evolution is accelerating
The advantages of the GPON standard compared to other types of PON technologies have been undeniable since its approval in 2003. However, by 2010, in Russia there were only 80 thousand broadband users based on GPON, according to J'son & Partners Consulting. The main barrier to greater growth, as is almost always the case with a product entering the market, was the high price of active optical equipment. In the last few years, prices for station transceivers and subscriber optical modems have decreased significantly, due to which by the beginning of 2017 (according to analysts of the same company), the number of Russian GPON users will approach 6 million, that is, it will increase almost 75 times over the next seven years!
This pace of evolution will be determined primarily by the construction of GPON networks, which the largest telecom operators Rostelecom and MGTS began two years ago. The second factor stimulating the spread of GPON is the increased attractiveness of this broadband access technology for subscribers, which is determined by the introduction of additional services and interfaces into GPON expected by users (and promised by developers).
