WDM-PON came under the spotlight last year when three vendors — ADVA Optical Neworking, LG-Nortel, and ZTE — all claimed to have come up with solutions that use more wavelengths to add capacity in the access network (see WDM-PON blurs the boundary between metro and last mile).
For LG-Nortel, the trigger for getting its WDM-PON equipment onto the market was the acquisition of Novera Optics. LG-Nortel had been working on a WDM-PON solution on its own account, but Novera provided the finishing touches in terms of low-cost optics and intellectual property rights to those optics, says Mervyn Kelly, business development director for LG-Nortel.
Kelly describes Novera's box, which is still on sale from LG-Nortel, as a dumb box. The box simply sends and receives 16 wavelengths, using a broadband light source to tune the wavelength of the receivers located at the end-user premises. He says the box is ideal for brownfield deployments, where network owners want to boost the capacity over an existing fibre.
Nortel's own solution, which uses the same low-cost optics, adds service-level intelligence to the equipment to support the sort of features that operators have come to expect from Ethernet, such as link aggregation and Layer 2/3 switching. Each network interface card in the chassis supports up to eight Gigabit Ethernet channels per uplink.
Although the message is starting to get out, WDM-PON is often misunderstood, says Kelly. He outlines a couple of common misconceptions:
Myth 1: WDM-PON is too expensive
When metro equipment specialist ADVA Optical Networking announced its WDM-PON solution, at first LG-Nortel was pleased that another operator was talking about the benefits of the technology, says Kelly. But on closer examination, it turned out that ADVA's solution wasn't really comparable because the WDM wavelengths only reach as far as the street cabinet or local exchange, not right to the end-user.
What's more, ADVA's solution relies on wavelength-specific transmitters, which are widely considered to be too expensive for access deployments. In contrast, LG-Nortel's solution uses colourless, low-cost optics in the customer premises equipment (CPE), Kelly points out.
"Our WDM-PON solution is ready for prime time, traditional WDM in the access network isn't," he claims.
LG-Nortel admits that its Ethernet Access solution is slightly more expensive than GPON/EPON alternatives, but says the business case really does stack up for certain types of deployments.
Kelly highlights the case of UNET, a service provider in the Netherlands, which is building out fibre networks in business parks. "Before speaking to us, UNET had a choice of leasing 32 fibres from KPN, or putting an Ethernet switch in the business park. With Nortel's WDM-PON solution they simply leased a single fibre from KPN, and replace the expensive Ethernet switch with a cheaper WDM mux," he explains.
Myth 2: WDM-PON isn't standardised
Another common misconception about WDM-PON is that it needs to be standardized before it can be useful. "85% of our solution has been standardized for 15 years — because it's based on Ethernet," Kelly claims.
In Kelly's view, the standardization issue is a red herring. Standardization is all about interoperability, and while GPON may be standardized, that doesn't mean that one vendor's kit will talk to another's, because the software interfaces are different. "Verizon famously stood up in a conference and said they had four GPON vendors in the lab and none of them would interoperate," he recalls.
It's just the optics for the CPE that isn't standardized, and that aspect will be addressed through work in the NG-PON2 Group of the Full Service Access Network (FSAN).
In the meantime, LG-Nortel says it is working with CPE vendors to allow them to develop subscriber equipment that will be compatible with WDM-PON optical line terminals. LG-Nortel plans to supply the optics — a Fabry-Perot laser with a bit of tuning circuitry — in a form that CPE vendors can drop straight into their boxes.
Myth 3: Chapter 11 conundrum
Finally, it's worth asking whether LG-Nortel has been impacted by Nortel's Chapter 11 credit protection in the US. The answer is that LG-Nortel is a legally separate entity that is 50% plus one share owned by Nortel and 50% less one share owned by LG. "We are profitable, so it wasn't deemed necessary to put us in Chapter 11", Kelly comments.