Fibre to the home - GPON vs Active Ethernet

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savag3

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#58040 5-Mar-2010 01:06

What are peoples thoughts regarding GPON vs Active Ethernet for fibre to the home?

GPON uses passive optical splitters to connect up to 32 fibres to a single fibre which is then connected to an OLT in a roadside cabinet which provides the service. This is a shared medium where all 32 customers recieve the same transmission from the OLT and send back their seperate transmissions on effectively the same fibre. It is pretty similar to the way TelstraClear's Cable network operates - just using fibre instead of copper.

Active Ethernet runs as you would expect for an ordinary Ethernet network. Each customer has their own fibre which runs back to a switch in a roadside cabinet. The type of switch used determines the speed of the connection to the customer and the bandwidth of the uplinks of the switch determines whether there is any contention on the network.

Given that the Government has said it will require dark fibre to be provided and my understanding of GPON is that this wouldn't be possible with that kind of architecture due to the passive splitters combining 32 customers into a single unit. This is due to the fact that all customers on the same fibre can only be connected to one OLT. So GPON is probably dead unless someone convinces the Government not to require dark fibre availability.

I also believe that GPON is a poor choice because of its shared nature. The last thing we need is yet another shared bandwidth bottleneck.

My understanding is that GPON is incapable of delivering 1Gbps and would also struggle with even a sustained 100mbps to all 32 users sharing the link to the OLT. This seems a bit silly given the likely lifetime of this installation of many decades.

This pdf has an interesting comparision of the two technologies.

I also wonder what the implications are of the Government requiring an Active Ethernet/dark fibre style of network on Telecom's GPON deployments in those new subdivisions. Would they end up with their network being overbuilt by another provider?

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Uber Geek

#304657 5-Mar-2010 07:26

The Government has moved away from favouring Active Ethernet (herein referred to as P2P) over GPON in the proposals for FTTH. Initially they did favour P2P given its future proofing however feedback from the industry and, I surmise, the cost differential of providing P2P vs GPON has meant that they have relaxed that "requirement" in the Local Fibre Company proposals.

There is plenty of analysis in most major markets that looks at the cost of deployment and the exponential cost of building as you move from urban to suburban and to rural. The Broadband Stakeholders Group in the UK has done some good work on the cost of deployment for both technologies on a household density basis.

Interestingly many FTTH rollouts around the world have tended to favour GPON more and more - almost like a stepping stone in the Fibre to the Exchange moving to FTTC type approach. The next economic step being FTTKerb rather the FTTHome without closing off the avenue of extending from GPON to P2P.

Opinions of other commentators (around the world) is that the absence of demand for more than 50Mpbs (at the moment) suggests P2P is overkill. Not to say it doesnt mean that we may not need the bandwidth in the future but its hard to fund it now. Its hard enough to justify a GPON business case.

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binarybrother

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#304727 5-Mar-2010 12:23

You're always going to have shared backhaul from the cabinet/exchange you connect to back into the transport network. Active Ethernet might give you a 10/100/1000 speed access port but you'll still have the backhaul from the Ethernet switch in the cabinet/exchange back into the transport network.

GPON is probably a much more cost effective option in the NZ environment than P2P Ethernet, unless you happen to live in an apartment building.

raytaylor

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#305209 7-Mar-2010 13:49

I personally would rather not have them use GPON
Active p2p is my prefered choice. This network is going to be aimed at delivering television services as well and once you get 2 hdtv decoders in a household, bandwidth starts getting scarce when the trunk fibre is shared. Remember multicast switches and routers are the key to making a digital tv network over fibre work - or anything that can compete with sky anyway. If you have 10 houses on a gpon fibre trunk, and the technology only allows that to divide equally - that means that the benefits of multicasting stop further up the line. A potential of 20 decoders over those 10 houses would mean that the same channel might be going down that same trunk fibre 2 or 3 times wasting alot of bandwidth.

I would only favour gpon if dark fibre was still avaliable to me - When its avaliable locally I want to connect my home and office by a private fibre network. Will happily pay a nice price for it too.

Gpon might also be workable if they could assign different amounts of spectrum down the fibre to different nodes. Eg. House 1 gets 50% of the light frequencies because they are on a higher plan than the other 5 houses on the trunk fibre so they can share the remainder and get 10% each.

Ray Taylor

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eXDee

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#305244 7-Mar-2010 18:41

I don't know much on the subject - but it sounds like they would go for the cheap option then regret this decision come years down the track? This always seems to happen -_-

Sigh.

cyril7

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#305345 8-Mar-2010 10:21

Not all TV service will consume IP bandwidth, GPON as will all pons can deliver in addition to Ethernet/IP traffic a full 3GHz spectrum of RF to support currently deployed broadcast technologies.

Cyril

savag3

188 posts

Master Geek

#305368 8-Mar-2010 11:17

Having thought a bit more about this I have come to the conclusion that deploying GPON would be a very big mistake. I really hope that the Govt dosen't do this and does in fact insist on dark fibre like they promised they would before the election. I can't really see how GPON is better than simply getting Telecom to install some more roadside cabinets to shorten copper lines and run VDSL2 on that copper which could provide a 50MBit service. Then wait until they can make the business case for a proper Ethernet p2p fibre network acceptable before putting fibre into the ground which could be obsolete in 10-20 years when it should be lasting for 50-100 years if it was done properly.

sbiddle

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#305379 8-Mar-2010 11:44

cyril7: Not all TV service will consume IP bandwidth, GPON as will all pons can deliver in addition to Ethernet/IP traffic a full 3GHz spectrum of RF to support currently deployed broadcast technologies.

Cyril

This is exactly how Verizon deliver their FiOS TV product now across their GPON network.

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raytaylor

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#306128 11-Mar-2010 01:42

sbiddle:
cyril7: Not all TV service will consume IP bandwidth, GPON as will all pons can deliver in addition to Ethernet/IP traffic a full 3GHz spectrum of RF to support currently deployed broadcast technologies.

Cyril

This is exactly how Verizon deliver their FiOS TV product now across their GPON network.

Learn something new every day.

Ray Taylor

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Zeon

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#306774 12-Mar-2010 22:10

Multicasting is good to a degree if the range of channels is limited, for example if the internet provider also provides the tv services. However, the whole point of the internet is to be innovative and with the new fibre rollout, small, specialized channels with low viewerships should be able to start up. Currently, due to the importance of economies of scale in broadcasting etc. you would never see a competitor to Sky.

While GPON maybe cheaper now, bandwidth demand is going to get far greater in the future. The above scenario is just one example. Maybe in 20 years time our entire wall will be a massive screen that we talk to relatives on at 100megapixel. each premise should have its own fibre and switchport even if the cost is a bit higher (15% according to a treasury report).

But knowing how the government approaches infrastructure in New Zealand they won't see it like that....

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webwat

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#307926 16-Mar-2010 18:13

binarybrother: You're always going to have shared backhaul from the cabinet/exchange you connect to back into the transport network. Active Ethernet might give you a 10/100/1000 speed access port but you'll still have the backhaul from the Ethernet switch in the cabinet/exchange back into the transport network.

GPON is probably a much more cost effective option in the NZ environment than P2P Ethernet, unless you happen to live in an apartment building.

By "trunk fibre", I presume you mean backhaul from the nearest node to your place. This would be active fibre, but probably starting at a couple of 1Gbps links for 4 or more GPON lines, so the backhaul always starts with some reasonable contention because each link probably costs over $1000 per month regardless of whether Vector, Telstra or Telecom do the backhaul. Most new GPON nodes support twin 10Gbps uplinks but likely to connect Gbps at first, and that part might have to wait until Vector et al offer 10Gbps routed through their backhaul networks.

Dark fibre all the way from the building to the active node (which could easily be Outside Plant [roadside] or Central Office [exchange/server room]) is called "home run" fibre. Its really useful for commercial districts with a high density of office space, but overkill for home users that are always price sensitve. Lots of home users could already get Active Ethernet if they could afford it, but obviously there is an economy of scale so we all like the affordability that we get with contention. VDSL is limited, high maintenance, and requires way too many active nodes.

GPON gets much more economic in low density areas where just a few strands can be run out to passive nodes miles away that are much cheaper without active powered equipment and aircon etc. So you can have the GPON service in a cabinet within easy reach of the backhaul providers Point of Presence. Roadmap for GPON is to move to 10GEPON but thats distant future and uses the same splitters anyway, so 10GEPON is pointless for large nodes until 40Gbps backhaul becomes more common. Both GPON and 10GEPON have QoS functions built into the protocol, and I dont think you will be using the full 2.5Gbps line capacity until your ISP finds a way to squeeze money out of you for international traffic. The maximum 64 users per GPON link will have to share for now.

Time to find a new industry!

webwat

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#307930 16-Mar-2010 18:21

cyril7: Not all TV service will consume IP bandwidth, GPON as will all pons can deliver in addition to Ethernet/IP traffic a full 3GHz spectrum of RF to support currently deployed broadcast technologies.

Cyril

Not all lof the ONTs support the RF over fibre but I guess Telstra's cable tv users have something like that already. Some ONTs appear to have powerline networking etc (for networked appliances) so it will be interesting to see exactly what features actually get rolled out compared to the world's current fixation with multimedia. Its funny to imagine that a toaster really could become a computurised node on the network! We would have to stop saying that internet isn't simple like a toaster...

Time to find a new industry!

cyril7

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#307946 16-Mar-2010 19:10

The Alcatel ones I have seen that Telecom have been playing with dont have RFoG, but it was an option for the product. Guess it all depends ultimately what marketing strategy they have in mind.

In the states and in particular Version Fios the use of the MoCA and HomePNA interface (local ethernet over RG6 coax) is a natural one as such a large number of houses are wired for cable TV so the cables are already there.

I would not expect MoCA to be so common on ONT's deployed here.

In many part of Europe, cable is also very much the norm, so MoCA seems to be popular there too.

Cyril

FibreFan

18 posts

Geek

#308790 18-Mar-2010 15:17

From what has been said previously - it seems an active MetroEthernet system is definitely the best option for NZ's in regards to future prospects/growth of the country, possibilities of a larger amount of people working from home (far better video conferencing capabilities) which would spin off into possibilites of reduced carbon emissions and reduced traffic around central CBD's around Auckland.
Using GPON would entail another shared network and, as said above, could result in a much larger/complicated broadband bottleneck which would cost a lot more to fix in the future if we don't get it right the first time.
I don't see the point in taking a baby step in the process, i.e. going through with GPON as things are only going to get bigger and harder to break through in the future. Ethernet has shown to provide;
1) high network reliability
2) easy to scale/manage and trouble shoot &
3) although to initially employ would cost more than GPON (15% i think it was), it would be far more cost effective to produce the results now than in x amount of years.

At least if it's done now we can make use of the worlds most up to date technology and be a strong global force on the digital front. I'm all for bringing fibre to the door. Go Vector!!!

#fttd

webwat

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#308912 18-Mar-2010 20:55

No its not. GPON is not shared that much more than Ethernet. the highest contention sharing is probably on the international bandwidth for a few years to come, and perhaps in future there will need to be extra metro backhaul links as data volumes rise. Contention on the GPON links for an average 100Mbps service is worst-case 2.5:1 (thats really good) so no amount of IPTV will cause trouble there. I can see heaps of congestion for backhaul if people start doing huge amounts of national data such as "cloud computing" might demand for things like web applications and online backups.

Introducing excessive active ethernet nodes in the street would not be economic or reliable, defeating the purpose of installing ethernet to the door. and having no advantage. GPON nodes can be designed for household use, such as phone and powerline interfaces in watertight outdoor boxes. You cant expect every household to go out buying IP phones straight away.

Time to find a new industry!

FibreFan

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#309085 19-Mar-2010 12:09

On the contrary I believe installing 'excessive' Ethernet fibre optics now is a highly logical and smart option - look at it from this perspective. Say we choose Fibre to the Cabinet and 5 - 10 years down the road we find ourselves stuck in a rut as the majority of global players got it right the first time by installing fibre to the door (the likes of Korea, Japan, California and parts of Europe - Singapore is also getting a piece of the action) - by that stage our already insufficient infrastructure will be extremely outdated and will require a massive amount of capital to fix the problem which will not be economical.
Fibre to the Cabinet will be bad news for a country like ours who already have a poor transport infrastructure - we have to look for the smart option, i.e. increasing the scope for transporting data and correspondingly decreasing the transportation of people - to do this we require an 'excessive' system now and will be inconceivable without a world-class communications infrastructure.

Just think about the response that Alexander Bell had from bankers and investors when he was seeking finance for wire telephony in the 1880s: "What are you planning to do Mr Bell … wire up every house in the country?"

The future is inevitable and we must be ready to make drastic changes now in order to secure our place as world-class on the global scale - no one can be certain as to how much growth will occur in the next 5-10 years but we can be ready to it on full force!

#fttd

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