In terms of penetration into the life of large cities, the Internet is not much inferior to water supply.The FOM data at the beginning of 2015 show that the bar of 80% has been taken in millionaires.That is, all users from high- and low-rise buildings are already, one way or another, connected.Only the private sector remains uncovered, which is also the last point of growth "in breadth".It is not so easy to get this segment through FTTB networks, DSL is hopelessly outdated, Wi-Fi is fast and legal only in glossy prospectuses.But xPON managed to fall in price literally to obscene.I will try to tell about it.Not the first time, but certainly not the last.But before looking at the various uses of xPON, let's note that the sacred question, "EPON or GPON", seems to be a thing of the past.Already now the most popular trio of manufacturers in Russia - BDCOM, Eltex and HUAWEI - has become universal: these vendors are ready to provide devices from both main branches of PON development.Prices differ unprincipledly, opportunities and speeds are also not far from each other.The difference, to put it very briefly, is as follows: you can connect up to 64 subscriber units (ONU) per port for EPON versus 128 per port for GPON.And this difference, it seems, will not last long: chips for EPON have already appeared on the market, allowing you to include up to 128 ONUs per port.At the moment, only Eltex has a complete solution in their TurboGepon, and even then, with differences from the standard, however, it does not make much sense to attribute this feature to real problems.And that's why.The optical budget "for 128" really "passes" only in high-rise buildings.It would seem that GPON with its 128th ONU will be a clear winner there.But there is a nuance (s).The typical level of penetration, in the absence of monopoly and the presence of competition, is usually only 10-15%.Moreover, it is impossible to predict in advance where users will appear.On the other hand, it is impossible to pull in-house wiring personally for each new client; for quality-sensitive welding and installation of PON technology, this is the right path to problems.Therefore, if you do not think about such exotic things as cable TV over fiber, it is very convenient to use "division by 128" even for EPON, that is, take end dividers with a margin to cover half the apartment capacity.For example, on a floor with 8 apartments we put a divider by 4, or we place one divider by 8 through the floor.At the level of the house, the average statistics will still give the result - there will be no more than 25% of actually connected subscribers, of the number of apartments in the house, which gives 64 clients from the PON port.The GPON port in this case will remain only half loaded.Consider also the consumption of traffic by the IPTV service.Almost any operator currently providing IPTV services offers its customers 150-200 channels.The total traffic can reach 600-1000 Mbps.However, despite this, the load on one PON port will be determined only by the number of channels viewed by clients from this port.According to statistics, their number does not exceed 20. The share of HD channels will not exceed half of this number.We will consider the bitrate for HD to be 15 Mbps, the bitrate for SD channels - 5 Mbps.Let's calculate the total consumption: 10*15 + 10*5 =200 Mbps.The final average consumption for one PON port at 100% activity of all clients (taking into account inclusion divided by 64) will be equal to 64 * 4.5 Mbps + 200 Mbps = 488 Mbps.When 128 clients are enabled - 128 * 4.5 Mbps + 200 Mbps = 776 Mbps.This is a single port load in the most optimistic scenario when all clients are connected and active.BDCOM P3310C with two PSUs and four PX-20+ SFP modules will cost ~70,000 rubles.Eltex - LTP-4X with two PSUs and four C + SFP modules, will cost ~ 125,000 rubles,Huawei - MA5608T with AC / DC PSU, 8 GPON ports with eight SFP + C + modules will cost ~ 160,000 rubles.We calculate the cost per client using the formula Skl=(Solt/Qp/N)+Sont, where:Solt is the cost of OLT, Sont is the cost of ONT, Qp is the number of PON ports, N is the number of clients from one PON port.The number of ports for Huawei will be considered equal to 4, to bring it to a single configuration.For clarity, we summarize the results in a table: Comparison indicator BDCOM(64) Eltex(64/128) Huawei(64/128) OLT price, RUB 70000 125000 160000 ONU price, RUB 2046 2533 2150 Price per client, RUB 2319 3021/ 2777 2774/2462The table clearly shows that in terms of price, EPON is more profitable than GPON solutions.Building a network with an eye to the futureComparison indicator BDCOM(64) Eltex(64/128) Huawei(64/128) OLT price, RUB 70000 125000 160000 ONU price, RUB 2046 2533 2150 Price per customer, RUB 2319 3021/2777 2774/2462BDCOM(64) Eltex(64/128) Huawei(64/128) OLT price, RUB 70000 125000 160000 ONU price, RUB 2046 2533 2150 Price per customer, RUB 2319 3021/2777 2774/2462Eltex(64/128) Huawei(64/128) OLT price, RUB 70000 125000 160000 ONU price, RUB 2046 2533 2150 Price per customer, RUB 2319 3021/2777 2774/2462Consider today's participants from this point of view.EPON BDCOM equipment can work with different vendors that support the CTC 2 specification. Those who have already worked with OLT BDCOM know about alternative ONU models that work successfully with OLT.Together with Huawei OLT, ONUs from ZTE, Fiberhome and others are successfully working.At the time of writing, OLT from Eltex did not allow working with third-party ONUs.This may change in the future, but for now it's worth paying attention to.Traffic growth continues every year and the moment when the xPON speed will not be enough is not far off.10G xPON solutions are already available on the market (10G xPON should be understood as XG-PON and 10G-EPON), which allow providing 10G downlink and 2.5G uplink traffic.Since 10G xPON uses other wavelengths for operation, a phased transition of clients from xPON to 10G xPON is possible.Wavelength distributions for different PON generations can be clearly seen in the figure below.To gradually transition clients from xPON to 10G xPON, it is enough to install an additional OLT that supports 10G xPON or an additional board (if you use a chassis, for example, Huawei).Using filters, add the signal from the ports of the new device to the existing xPON network and distribute new ONUs that are being transferred to 10G xPON clients.Unfortunately, the current price of 10G xPON is almost ten times higher than usual, which creates serious barriers to mass adoption.In our opinion, in the next 5 years, it is possible to switch to 10G xPON in the segment of multi-storey buildings.This implies the use of not "pure" 10G xPON, but work in a combined mode.This is due to the fact that 90% of traffic is generated by 10% of clients and it is economically justified to transfer them to the new PON, as well as connections of legal entities.persons.It is also possible to use 10G xPON at the aggregation level.In this case, instead of a conventional ring using STP, a ring is built using two independent cables to obtain a 1+1 (type B) scheme.This method allows for a non-volatile, dual-path connection for each switch.Despite the fact that a massive transition to XG-PON has begun in China (which has been creating a shortage of EML lasers for two years now, which has been felt by everyone who orders CWDM or DWDM modules over 40 km) in Russia, in our opinion, the prospects for using 10G xPON in sectors of low-rise and private houses, in the next 5 years are unlikely.In this segment, the cost of equipment is most important and a multiple price increase is unacceptable.In case of lack of xPON speed, operators will prefer to switch to 32 users per port.TWDM PON technology will help to do this without changing the cable infrastructure.TWDM PON technology allows you to organize several PON channels in one fiber using different wavelengths.Especially for this, the ranges 1270-1280 / 1570-1580 nm, 1535-1540 / 1553-1558 and 1535-1540 / 1570-1580 nm are allocated.Summarizing the above, let's try to figure out how true some of the common statements are: GPON is faster than EPON.Of course, the maximum allowed downstream speed in GPON is higher, however, if you connect 128 clients per beam, then the specific speed for one client will be equal to the EPON option, while the upstream speed will be even less.In addition, above we considered the traffic consumption typical for different types of clients and obtained the required speed, which can be provided by both EPON and GPON.For this reason, we will consider a draw.GPON is more functional than EPON.GPON has more opportunities, but if we discard the TDM transmission, since the propagation of E1 is extremely low.With GPON, by using a detailed setting of speeds and priorities for each GEM port, you can better manage services and traffic for them.However, this significantly complicates the setup and for small operators that do not have a configuration management system integrated with billing, this is more of a minus than a plus.As for the widely used functionality, it is equally presented in both versions.GPON allows you to connect 128 clients per port, which makes it cheaper in the end.In the comparison section "EPON and GPON in rubles", we were able to see that EPON is cheaper than GPON solutions, even if 128 clients are included from one PON port.conclusionsWe compared various aspects of EPON and GPON solutions from both economic and technical points of view.From the information provided, you can conclude which option is closer to you.In our opinion, EPON is more suitable for small and medium-sized operators.Since in cases where it is necessary to provide a level of access in broadband networks, EPON functionality is sufficient, and the price is more attractive.At the same time, the equipment is very easy to set up.For large operators with significant budgets, GPON can be considered.Some increase in price is covered by the ability to make more detailed settings for each service.Moreover, large operators can easily afford full integration from the manufacturer.As a result, the initial configuration of the equipment to the requirements of the operator, as well as a configuration management system integrated into the billing.Such a solution reduces the need to configure the equipment to almost zero.The most important thing was not disclosed - GEPON is easily controlled via the WEB and all settings are simple and intuitive, GPON has only recently received a WEB interface, and some have it, but there are obvious problems with the functionality.At the same time, network management systems should either be integrated with billing or not used at all, because setting through them is sometimes more complicated and less clear than through the OLT WEB interface.