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Optical/IP

Corvis Eliminates EDFAs

Corvis Corp. (Nasdaq: CORV) today announced two new products targeting regional networks and submarine cables (see Corvis Expands Product Portfolio).

The products aim to carry up to 800 Gbit/s per fiber on cables with no intermediate amplifiers for distances of up to 350 kilometers. The CorWave XL supports terrestrial connections and the CorWave XF supports point-to-point and festoon subsea connections. Festoon refers to applications where subsea cables are looped along a coastline, linking multiple landing points.

Corvis says that it will ship these products in the second quarter of this year, and that they mark a real breakthrough. Its press release quotes Andrew McCormick, a senior analyst with Aberdeen Group Inc., saying that Corvis is “first to commercialize Raman amplification.”

It’s “disruptive technology,” according to a quote attributed to David Huber, Corvis’s president and CEO, in the press release. It will enable Corvis to target new markets and new potential customers, it says.

At first glance, all of this may seem a little confusing from two points of view. First, Corvis’s existing products have already been used in trials demonstrating that optical signals can be carried over much longer distances -- up to 4,000 kilometers -- without needing regeneration (see Corvis Drives 4,000 Kilometers...).

Second, established vendors of submarine cable systems say the use of Raman amplification on unrepeatered subsea cables isn’t new. It was first demonstrated six years ago, when STC Submarine Cables -- now part of Alcatel SA (NYSE: ALA; Paris: CGEP:PA) –- showed a system driving 16 channels of 2.5 Gbit/s over a distance of 426km at the European Conference on Optical Communications (ECOC) in 1995. The demo was repeated over a distance of 511km at the Optical Fiber Conference (OFC) in the same year.

Alcatel has now installed a commercial system of this sort in Canada, according to Eric Brandon, manager of Alcatel’s unrepeatered system design team. In lab experiments, Alcatel has already demonstrated a system carrying 32 channels at 40 Gbit/s over 250km and plans to unveil a system carrying one terabit a second over 350km at OFC next month.

Other submarine cable system vendors have also developed Raman amplication products. NEC Corp. (Nasdaq: NIPNY), for instance, says that it can already do 640 Gbit/s over 350km.

However, Corvis’s claims stand up to scrutiny on closer inspection.

Here’s the score. Nowadays, most of the fiber that's installed on long-haul routes incorporates EDFAs (erbium doped fiber amplifiers). The EDFAs are sections of special fiber that are spliced into the normal fiber every 60 to 80 kilometers. The outer cladding of the fiber is pumped with light from a local laser, and this boosts the power of the actual signal passing through the core.

Raman amplification works on a similar principle, but in this case, there’s no need for special fiber.

The distance records of thousands of kilometers that Corvis (and other vendors) have achieved are over fiber fitted with EDFAs. The new products unveiled by Corvis achieve a maximum distance of 350 kilometers without EDFAs. That's the key point.

Likewise, the records claimed by Alcatel for Raman pumping over unrepeatered subsea systems are for fiber that incorporates “at least one EDFA” according to Marc Fullenbaum, an Alcatel product marketing manager. The “unrepeatered” term refers to the absence of electrical regeneration of the signal, not the absence of EDFAs.

The lab experiment that Alcatel will report at next month’s OFC carried 100 channels of 10 Gbit/s over 350 kilometers of fiber incorporating one EDFA. Corvis says that its new products will support 320 channels of 2.5 Gbit/s or 80 channels of 10 Gbit/s over the same distance, with no EDFAs. Right now, this is a claim. It’s yet to be proved in trials.

So, is eliminating a single EDFA such a big deal? It probably is, in that EDFAs involve putting power down the cable to power the lasers that drive them. “It’s not cheap,” admits Fullenbaum. Having lasers at the bottom of the sea also raises questions about reliability.

-- Peter Heywood, international editor, Light Reading http://www.lightreading.com

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Peter Heywood 12/4/2012 | 8:55:59 PM
re: Corvis Eliminates EDFAs Corvis really does have something new here. The other distance achievements have all been over fiber fitted with EDFAs. These products promise to do 350km with no EDFAs.

I've now managed to confirm that this is the case, so I've revised the story pretty extensively.

Peter
CogswellCogs 12/4/2012 | 8:55:59 PM
re: Corvis Eliminates EDFAs This is another point for those of us who perceive an anti-Corvis slant to LR. The standard is becoming "Print negative information as news, discover the facts, and then correct the story".

Is it my imagination or is this happening more often for Corvis than any other company? What about the recent article about the Corvis optical switch regarding port count? Posted, then corrected. I also seem to remember an interview with an anti-Corvis slant a few months back (which provided a corresponding "Quote of the Week") that had to be corrected.

With the increased scrutiny from your reading public, I would hope that you would research THEN report to help allay our perception of bias. Or maybe Huber should just give in and buy an ad.
joeysmith 12/4/2012 | 8:55:57 PM
re: Corvis Eliminates EDFAs # of vc's working 24x7 to build the networks of tomorrow: 97

VC's who allow their portfolio companies to get trashed by Lightspeed-backed LightReading: 17

VC's who owe it to their portfolio companies to challenge this arrangement: 17

Likely shame of a VC who backs Lightreading when you look across at me at the upcoming Robbie Stephens dinner: incalculable

The truth: Priceless

What do people think? Let's oncover the truth!!!

joeysmith 12/4/2012 | 8:55:56 PM
re: Corvis Eliminates EDFAs Hard-working, earnest people whose start-up companies get trashed beause they a) don't buy advertising from LightReading or b) aren't a Lightspeed portfolio company: 2,371

...inclduing Lucent, Ciso and Nortel employees: 507,322

Readers who read LR misrepresentations about their companies and have the guts to rise up, reveal the truth and protect their companies and fellow employees: 3

Companies that subsidize LR's attacks on other companies through advertising dollars: 17

Challenging Steve Saunders and Lightspeed-backed LR in the name of accurate reporting: priceless

The truth will set you free. Can anyone else come forward with the truth please?

Thank you!
photonic314 12/4/2012 | 8:55:56 PM
re: Corvis Eliminates EDFAs Does EDFA mean erbium doped fiber amplifier?

So I am to understand Corvis does not use an amplifier of any kind in the entire distance...in other words they do not amplify the signal at all?

Gee that is magical...how much does this system cost?
joeysmith 12/4/2012 | 8:55:55 PM
re: Corvis Eliminates EDFAs Optical and access companies advertising on LR: 17

# of these companies getting bad press on LR: 1

Probably monthly cost of a banner ad on a website: $35,000

Ethical value of "hush money": $0

The truth: priceless

My partners and I ask all fair-minded people in this inudstry to rise up and uncover the truth. Make yourself and your companies proud! If you sponsor LR, do the right thing!!!

Thank you!
abarbier 12/4/2012 | 8:55:54 PM
re: Corvis Eliminates EDFAs They use a Raman Amplifier (it is based on a
nonlinear effect). The advantage is that it
is less noisy...
Petabit 12/4/2012 | 8:55:49 PM
re: Corvis Eliminates EDFAs This is starting to sound a lot like silkroad (remember them...)

350km at 0.25 dB/km (for real fibre in the ground) is 87.5 dB of loss. Add in some splices and you are talking 90 dB.

You can put up to about 15 dB of Raman amplification into a fibre, before the noise swamps the gain you get. Do that at both ends, and that shaves 30 dB off your loss. So that's 60 dB.

The maximum power that you can launch into fibre from a single channel is about +10 dBm before non-linear effect kill your data. So therefore the power at the receiver is about -50 dBm. Which is about 20 dB lower than any commercial 10 Gbit/s receiver.

And that hasn't included the mux and demux loss.

Before anyone suggests it, you can use the double Stokes shift trick to boost the Raman gain, but there are two reasons not to: you are then way past the point that the optical power will melt the fibre, and two, Lucent have the patents.

So where did I go wrong in the maths?

P.
photonic314 12/4/2012 | 8:55:49 PM
re: Corvis Eliminates EDFAs Mr or MS PETABIT

ALL I CAN SAY IS ---AMEN!

Your math is not wrong!
ownstock 12/4/2012 | 8:55:47 PM
re: Corvis Eliminates EDFAs What is the metric for this new product?
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