tschmidt
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| GPON update
Though I’d post this here rather then in FIOS forum as this is more of a technology discussion. Ran across several interesting FTTP articles in the February issue of Lightwave.
RBOC BPON RFP is proceeding well. Verizon is the most aggressive and plans to start limited deployment of BPON later this year. For those of you tuning in late BPON is the next generation ITU PON standard. The salient points are speed increase from 622/155 Mbps to 2.4/1.2 Gbps and elimination of ATM.
One of the reasons I’ve had mixed response about PON is BPON does not have enough speed to support full-blown deployment of IPTV. BPON is great for high speed Internet and I give Verizon kudos for being aggressive deploying FTTP but it is not fast enough for IPTV. Seemed to me if you are going to make the massive capital investment to replace copper with fiber it ought to be able to support IP HDTV. Assuming a 1:32 split GPON is capable of delivering 75 Mbps 24/7 to each drop. SDTV requires about 3Mbps and HDTV 20 Mbps using MPEG2 compression. GPON is just barely able to support worst-case assumption about Video on Demand. If we assume 1:32 split, 4 different streams per household PON distribution network needs 2.4 Gbps just for TV. HDTV will likely be a long time rolling out and four different demand based HDTV streams per household are probably many years in the future. In the triple play “color” overlay Verizon is using “TV broadcast” channels do not share data path they are delivered independent of data. GPON gives Verizon a lot of maneuvering room to deliver IPTV video on demand before they become constrained by network performance limitations.
The other interesting tidbit from the RFP is interest in doing home distribution over existing TV coax cable Multimedia over Coax Alliance . This is one of the many “no-new wires” initiatives. Since most homes are already wired for TV using existing coax goes a long way to overcome market resistance to broadband. As a purist I cringe at the notion of data over coax - did that 30 years ago. But I have to admit it makes eminent marketing sense.
Buried in a different article is a quote from Mark Wegleitner Verizon CTO. Verizon sees WDM-PON as part of the roadmap. ronpin  and others have pitched WDM-PON in this forum but I really did not realize the implication until I read that article. WDM-PON allows Verizon to used a common outside plant architecture: single fiber 1:32 split, for all services. If requirements begin to outstrip GPON or one assumes 10GPON in a few years Verizon can use multiple “colors” over each fiber. If large customers want to implement their own point-to-point private network Verizon can use colors to deliver virtual dark fiber and on and on. The possibilities are endless. Sorry I was so slow to appreciate the implementation of what you guys were proposing - but once I did it took my breath away.
Twisted pair copper lasted about 100 years – Looks like Verizon is betting on a long useful life for PON.
Lastly anther article that caught my attention was low cost ONT triplexler. BPON requires three colors: one up and one down for data and a third down for TV overlay. Current generation triplexers are discrete modules. The high volumes being driven by FTTP roll out means a more integrated approach is possible using hybrid circuit fabrication techniques. This looks to be able to cut triplexer cost in half from current ~$100 to $50. That is more good news on the FTTP front.
/Tom |
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GhostDoggy
join:2005-05-11
Duluth, GA | BPON? Why would someone start deploying BPON and not just go for GPON? Curious, as always. |
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tschmidt
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| Time to market. GPON gear is not yet been fully certified by the ILECs nor is it volume production. If Verizon had waited for GPON mass deployment would not begin until 2007.
There is always better technology just around the corner. For now BPON is more then adequate to provide a competitive advantage and deliver triple play.
/Tom |
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GhostDoggy
join:2005-05-11
Duluth, GA | reply to tschmidt
That is strange. I wasn't aware that PON systems were LEC-only solutions. I thought they could be used by both cable and telephone operators. |
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tschmidt
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1 edit | said by GhostDoggy :I wasn't aware that PON systems were LEC-only solutions. I thought they could be used by both cable and telephone operators. BPON and GPON are ITU standards; as such they can be used by anyone.
As far as I am aware none of the Cable companies use Passive Optical Network (PON). The Cable industry formed a standards group, Cable Labs, that developed DOCSIS.
BPON/GPON require a dedicated fiber network. Distribution fiber does not carry any other traffic. DOCSIS on the other hand is designed to utilize the 6MHz CATV RF TV channel scheme. Download data is carried by one or my “TV” channels, upload data in band below the lowest TV channel.
/Tom |
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GhostDoggy
join:2005-05-11
Duluth, GA
| reply to tschmidt
Tom, thanks for the enlightenment regarding the different systems being used between the competing technological fields. I wonder if BellSouth is using PON of DOCSIS for its Americast cable television distribution.
For some odd reason I allowed myself into thinking that cable operators has some optical infrastructure in the field, but this would be difficult to send a radio-frequency across. lol |
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sdgthy
| Any modern cable plant is HFC (Hybrid Fiber Coax). There is fiber from the headend to a node in the field, at the node the signal is converted to coax and distributed to customers.
BPON uses virtually the same tech for it's RF overlay. |
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tschmidt
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| reply to GhostDoggy
Everyone uses fiber to some extent.
The Cable Industry distribution plant is Hybrid Fiber Coax. It started out as an all coax network and has evolved so backbone is fiber with coax only being used for short distances. CATV is an channelized RF scheme. When fiber is used the RF stream is converted to optical at the head end, transported over fiber as an analog optical signal then at neighborhood nodes converted back to electrical.
PON networks distribute TV two ways: IPTV and CATV emulation. IPTV deliver multimedia over IP packet network. BPON and GPON emulate current CATV HFC practice as sdgthy posted. A third color is used to carry CATV programming. At the ONT the optical interface is converted to coax and is identical to what a CATV customer sees. The ONT does what the cable node does: convert analog fiber signal to RF.
The only technical difference between current CATV practice and PON TV is the PON TV overlay is unidirectional. Upstream traffic, such as Set-top-box pay per view etc is carried over the IP network. That is why there is a coax to Ethernet adapter brick needed FIOS TV.
If you are interested in reading more of the gory details I've posted more info about Broadband First Mile on my site.
/Tom |
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