Cable Tech

Novera's Got a New PON Spin

As South Korea's DSL mania gives way to fiber, one components startup has a chance to capture 's heart with a new type of passive optical networking (PON).

While EPON and GPON tussle for Asian markets, Novera Optics Inc. is in trials with 50,000 lines of WDM-PON at KT. That's compared with 10,000 lines for KT's EPON trials, says Novera CEO Yoon Kim.

WDM-PON is a means of using Wavelength Division Multiplexing (WDM) to deliver one wavelength to each customer. That's the opposite of a traditional PON layout, where one optical feed is split and shared among 16 or 32 customers. The appeal comes from WDM-PON's point-to-point nature: one connection per subscriber, an appealing level of simplicity for telcos.

It's a new twist for the dynamic amplifier player founded in 1999, raising more than $100 million to chase the once-promising ultra-long-haul market. Several scrapped business plan and nearly $100 million later, Novera might finally have found a market that will stick.

Having raised money at the peak of the bubble, Novera -- originally named Ultraband Fiber Optics -- was pressured by its investors to spend big in 2001 after raising a second round of $83 million, including a $30 million lease line, to supplement an $11 million first round. The company leased 55,000 square feet of high-rent Silicon Valley space and started bulking up to an apex of about 150 employees. (See Ultraband Changes Name and Novera Optics Scores $83 Million .)

"When you raised money, that money was supposed to last one year," says Yoon Kim, Novera's founder and CEO. "That was how they calculated it."

Today, Novera occupies a modest third-story office in downtown Palo Alto, Calif. -- not near the big-name law firms on Page Mill Road, but on California Street, among the boutique restaurants and greasy-spoon student hangouts. Three executives and a handful of part-timers are all you'll find there; the remaining staff of about 30 is in Korea. Some had joined Novera in San Jose, but Kim, formerly a professor in Korea, asked them to return home to contain costs.

Outfits like Bell Labs have tossed around the idea of WDM PONs for years. Novera's breakthrough was to lower the cost, providing WDM-PON without requiring multiple lasers at the central office and a different subscriber-side optical network unit (ONU) for each wavelength. Kim won't discuss details, but the technology involves Novera's wavelength blocking coupled with athermal arrayed waveguides.

KT is using a 16-wavelength implementation of WDM-PON, but Novera officials say they can ship a 32-wavelength implementation, too.

WDM-PON has an interesting implication: Every wavelength can be a completely different service. You could put Gigabit Ethernet on one wavelength and an ATM service on the next one. And if some customers want to upgrade to, say, 10-Gbit/s Ethernet, changes only have to be made at the central office. This means the PON system laid out in the field doesn't have to be upgraded.

"This is a very good way to preserve the outside plant, which is expensive," Kim says.

Kim admits one wavelength per subscriber seems like a lot of bandwidth. But he's confident that demand will catch up to that level, while noting that WDM-PON can be shared by groups of users. A wavelength could be terminated at an apartment building, with the bandwidth split among tenants. Or, a WDM-PON wavelength could become the feeder for some other type of PON.

Even competitors agree WDM-PON is the obvious endgame for PONs, but the technology has always been doomed by price. Novera might have fixed some of that on the optics side, bringing the price per fiber down to "less than a factor of 2" more expensive than that of EPON, Kim says. The price drops more if you consider WDM-PON can put multiple customers on each wavelength.

But there's also the expense of feeding all this point-to-point bandwidth. "At the central office -- say it's 1 Gbit/s to the home -- you now have to put 32 gigabit ports on a switch somewhere," says Lowell Lamb, vice president of marketing for EPON chip vendor Teknovus Inc. "Data flows are idle most of the time. You're going to end up with very lightly loaded gigabit port connections for every customer."

Novera's technology comes at a time when KT is considering fiber-based broadband as a sequel to its massive DSL buildout (see Teknovus Takes In $13M and Chips Draw PON Plans). The carrier gave Novera a trial in 2003, then upped its bet earlier this year to a 50,000-subscriber trial.

EPON and GPON don't yet have to fear WDM-PON, as KT is the only taker so far. Kim has begun scouting for other customers, but he doesn't have any solid prospects yet. Novera's best hope, he figures, is with the countries already embracing PONs (see PON & FTTx Update and Report: PON Gear Takes Off).

There's also the matter of standards. WDM-PON has none. On KT's recommendation, Novera has gotten a spot on the Full Service Access Network (FSAN)'s next-generation access committee, but it's yet to be seen whether the group will embrace WDM-PON.

"They're a favorite son of KT, but there's no standard like there is for EPON or GPON," says Michael Howard, principal analyst with Infonetics Research Inc. "That's a challenge for them, but the KT trial is a great proof point for the technology."

For now, Novera can enjoy a bit of success after a brutal slog through the downturn. Revenues have begun trickling in -- less than $1 million last year and "some millions of dollars" this year, Kim says.

— Craig Matsumoto, Senior Editor, Light Reading

packettitan 12/5/2012 | 3:01:36 PM
re: Novera's Got a New PON Spin Gents,

The www.CernoluX.com leads me to a weird website which is totally irrelevant to optics. Someone can fix that?

Anyone has looked into the DWDM type WDMPON instead of focusing on the CWDM?

I guess BIDI refers to BX xver w/ 1-fiber link.

Pete Baldwin 12/5/2012 | 3:01:39 AM
re: Novera's Got a New PON Spin Sounds a lot like tunable lasers, doesn't it? It's the product everyone would use if the price would just get low enough ...

Anyone out there have any experience researching WDM-PON? I'd be curious how much progress/frustration has gone into the concept.
redface 12/5/2012 | 3:01:37 AM
re: Novera's Got a New PON Spin WDM-PON is a fascinating technology. It does not use any expensive components such as tunable lasers. Instead, it uses simple and inexpensive FP lasers to create all WDM wavelengths. For detailed study, one can check OFC 2005 proceedings - several papers and post-deadline papers were on this subject.

The basic operating principle of WDM-PON is laser injection locking. When an external optical beam of a certain wavelength is injected into a FP semiconductor laser cavity, the FP laser tunes into this wavelength if this wavelength is sufficiently close to the laser native wavelengths and if the external beam is strong enough. And the original multi-wavelength spectrum is replaced by a single wavelength. This phenomenon is called "laser injection locking". The external wavelength is called "locking signal". By modulating the drive current to the FP laser located at the customer site, the laser can transmit communication signal (upstream) at say 100Mb/s.

The locking signal is generated by an AWG. If the FP laser is connected to an output port of a 32 channel AWG demultiplexer and a strong optical beam with a broad wavelength band (say C-band) is connected to the input end of the AWG, the AWG will filter out most wavelengths and allow only one C-band wavelength of the ITU grid to go through on each port, thereby generating the locking signal. So the FP lasers at the customer sites are all the same and it is the AWG that gives them the WDM wavelengths they need. Therefore, you don't need expensive WDM lasers in WDM-PON.

The optical beam emitted from the FP laser (upstream traffic) will go back to the AWG port where the locking signal comes from, and be multiplexed by the AWG. So the same AWG demultiplexer now becomes a multiplexer. At the input end of the AWG demultiplexer, the multiplexed signal travels to the central office along one long fiber where it will be demultiplexed by another AWG and be detected by 32 detectors.

For downstream traffic, the network structure is the same, except that a different wavelength band (say L-band) is used. And due to an interesting coincidence, a C-band AWG demultiplexer is also a good L-band multiplexer and vice versa. So only two AWGs are used for a 32 channel WDM-PON and each AWG serves three functionalities simultaneously, 1) to generate the locking signal for the upstream traffic, 2) to multiplex upstream traffic, 3) to demultiplex downstream traffic. A 32 channel WDM-PON has at the central office one AWG, 32 detectors, 32 FP lasers, 32 fiber wavelength filters serving the BIDI function, one broadband source. At the customer neighborhood, there is an identical set. WDM-PON is a model of efficiency.

This network is capable of providing dedicated and symmetrical transmission bandwidth for each customer. Triple play of phone, Internet and video may be realized using this network.
PONlights 12/5/2012 | 3:01:35 AM
re: Novera's Got a New PON Spin Reading the second comment, my understanding now is that you're more flexible with the bandwidth, meaning you get more bandwidth per user. Could the cost per bit be less with a WDM PON than it is with EPON or GPON?
++++++ 12/5/2012 | 3:01:35 AM
re: Novera's Got a New PON Spin
WDM PON uses....
> one AWG, 32 detectors, 32 FP lasers,
> 32 fiber wavelength filters serving the
> BIDI function, one broadband source.

Too expensive. Compare that to a EPON/GPON, which uses 1 transceiver.

trynbald 12/5/2012 | 3:01:34 AM
re: Novera's Got a New PON Spin Well I believe AWG+allother stuff needed is far too expensive and complex here. Check www.CernoluX.com small Tunable Optical Add Drop Multiplexer. The only product which makes sence for this WDM-application, in my opinion. Granularity starting from ONE..no EXPRESSLOSS...Not at all!

Check it out guys!
redface 12/5/2012 | 3:01:30 AM
re: Novera's Got a New PON Spin PONlights:

I am interested in your comment regarding the cost per bit for WDM-PON vs. EPON. What are the factors that determine the cost per bit?
++++++ 12/5/2012 | 3:01:26 AM
re: Novera's Got a New PON Spin
"Cost per bit" is less important than "cost per subscriber"

rs50terra 12/5/2012 | 2:47:26 AM
re: Novera's Got a New PON Spin Another solution could be to use just a plain vanilla Point-to-point system operating at 1GE.

I compared the two and I fail to see the advantage of the WDM-PON over the P-T-P solution.

Am I missing something?

I would appreciate your point of view.



Each ONT: FP, AWG, high power source
OLT: 32 FP, AWG, high power source, 32 detectors, 32 filters for BIDI (what does BIDI mean?)
fiber depends on the location of the splitter. If the splitter is located in the CO, the same amount of fiber is required as for P-T-P.

OLT: 32 FP, 32 detectors
32 strands of fiber
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