Who's Growing a GPON?

Reliable sources say gigabit PON is on the drawing board of at least one major access supplier

June 30, 2003

4 Min Read
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Faster gear for passive optical networking (PON) may be in the works for at least one major respondent to the recently released RBOC "Fiber to the X" RFP (see RBOCs Hungry for Fiber) and A Closer Look at PON Econ).

According to reliable industry sources, who've asked not to be named, Alcatel SA (NYSE: ALA; Paris: CGEP:PA) is at work on gigabit passive optical networking (GPON) technology, a super high-speed network that uses a combination of passive optical components and Sonet framing.

GPON technology would be used to extend cheap fiber links within metro networks (see ILECs' Missing Links ). No one is yet suggesting GPONs for residential fiber.

Specifically, Alcatel is said to be interested in creating a GPON for backhauling traffic to the central office in metro networks -- mainly as a way to address carriers' growing demands to replace old private lines with newer, faster services, such as IP SAN extensions.

Alcatel won't confirm any work on GPON, even though word has it the vendor's touted GPON in analyst forums recently. A spokeswoman says research is always afoot on new technologies, but she insists the direction Alcatel's taking for the foreseeable future is in BPON, or broadband PON.For the uninitiated, here's a thumbnail tutorial in terms:

  • BPON is the same as an APON (ATM PON), with extra overlay capabilities for broadband services like video. APON is the PON transmission technique based on Asynchronous Transfer Mode (ATM) signaling that was developed by a group of carriers as part of the Full Service Access Network (FSAN) in the nineties. BPON is approved as International Telecommunication Union (ITU) spec G.983x. It supports data rates to 622 Mbit/s out to an endpoint (upstream) and back from the customer to the service provider's remote aggregation point (downstream).

  • GPON uses a different, faster approach (up to 2.5 Gbit/s in current products), encapsulating traffic in a version of the Sonet-compatible Generic Framing Protocol (GFP). GPON is on track to becoming the ITU's G.984x. Final pieces are expected to be put in place at meetings in August and October 2003.

  • EPON stands for Ethernet PON, which, as its name indicates, is a technique that uses Ethernet as the main transmission method for the PON. EPON runs at gigabit rates and has its own standarization process underway at the Institute of Electrical and Electronics Engineers Inc. (IEEE).

GPON fans claim its star is rising. Its blazing speed would make it ideal for "triple play" suites of voice, video, and data services from ILECs and other carriers. In contrast, other forms of PON don't have the bandwidth or multiprotocol support to do that. Its use of Sonet framing enables providers to link native TDM and voice connections into the PON without adding Internet Protocol (IP), making it more efficient than EPON.

Of course, for their part, EPON vendors such as Alloptic Inc. have much to say on the relative merits of their approach (see Chip Startups Bank on EPON and Alloptic Delivers FTTP in Wash.), particularly in keeping down the cost of fiber-to-the-home PONs.

So far, the only vendor that's shipped a GPON product is FlexLight Networks, which says its Optimate PON runs at 2.5 Gbit/s downstream and 1.25 Gbit/s upstream (see Giga-PON Ships Quietly). Flexlight hasn't announced any customers, though the box is said to be in trials at France Telecom SA (NYSE: FTE).

Flexlight's CEO, Gary Lee, says he expects competition to emerge fairly soon, mainly because there's so much interest in replacing private lines in metro networks with faster Ethernet services -- such as ones that extend storage area networks (SANs) from site to site via IP. GPON can also start replacing Sonet rings, Lee says."With GPON, you have standardized voice carriage like a Sonet or TDM link, with clocking guaranteed," he says. Carriers can save up to 50 percent on up-front capital costs using GPON links instead of Sonet OC48 (2.5 Gbit/s) rings, Lee claims. And the passive nature of a GPON ensures ongoing operational savings.

That kind of cost model is likely to be music to the ears of fiber-hungry carriers, if it can be proven out. Even EPON proponents, like Alloptic, acknowledge that for businesses where GFP is usually required to handle a variety of data traffic such as Sonet, Frame Relay ATM, voice, and Ethernet, GPON might be the most efficient choice, provided it was running at 2.5 Gbit/s or higher.

But cost is everything in PON, which explains why some vendors haven't run out to add a GPON to their BPONs just yet. A spokesman for Terawave Communications, for instance, says his company will wait till the standard solidifies and component costs are driven down, probably 2004, to release product.

Ditto others. "At the present time the world's largest carriers, represented by the FSAN membership, have chosen to deploy BPON, by and large," writes Jeff Gwynne, senior VP of marketing and business development at Quantum Bridge Communications Inc. If demand goes up and costs drop, that could make the cost of GPON implementation more attractive, he says.

Mary Jander, Senior Editor, Light Reading

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