x
Optical/IP

Poll Paints Bright Future for CWDM

Coarse wavelength-division multiplexing (CWDM) could eventually overtake DWDM in metro markets, according to a Light Reading Research Poll on the subject staged in October.

A total of 249 people took the poll, and -- surprisingly -- 43 percent of them went so far as to say that CWDM would overtake DWDM in metro markets. Another 35 percent said CWDM would be widely deployed, but not as widely deployed as DWDM.

The full results of the poll can be seen here.

Until recently, CWDM was considered something of a poor cousin to DWDM -- partly because it could pump only up to eight channels down a pair of fibers, and partly because it wouldn't work over distances of more than about 50 kilometers.

Now sentiment appears to have changed, mainly because CWDM promises to help carriers out of a jam by boosting bandwidths in metro networks without busting the bank.

Opinions vary over how much carriers can actually save with the technology. Some CWDM equipment vendors say they can cut costs by a factor of three, while DWDM vendors say savings rarely exceed 20 percent. In the Light Reading poll, 30 percent of respondents thought CWDM could deliver savings of more than 50 percent compared to DWDM. Only 25 percent of respondents thought savings would be 20 percent or less.

Confidence in CWDM as a technology appears to have grown since a 16-channel version was standardized by the International Telecommunication Union, Standardization Sector (ITU-T) last June. In the Light Reading poll, 82 percent of respondents said CWDM was mature enough to be used in metro networks; only 11 percent thought it wasn't.

The other reason for CWDM's increasing popularity is probably the growing availability of low water peak fiber, required for 16-channel systems, and the arrival of innovative CWDM solutions from the likes of Cisco Systems Inc. (Nasdaq: CSCO) and Transmode Systems AB (see Cisco Adds CWDM to Switches and Transmode Makes a Little Go a Long Way).

These and other issues concerning CWDM will be put in the spotlight in a Light Reading Webinar scheduled for next Tuesday, November 19, and hosted by Yours Truly. To get more information and to register for the Webinar, entitled "CWDM: Optical Capacity Without the Cost", please click here.

— Peter Heywood, Founding Editor, Light Reading
www.lightreading.com
<<   <   Page 2 / 4   >   >>
Peter Heywood 12/4/2012 | 9:20:35 PM
re: Poll Paints Bright Future for CWDM One of the audience polls in next Tuesday's webinar asks this very question - ie, if you need to pump 40 Gbit/s down a pair of fibers, which of these options will be most cost effective in 2 years time:

16 channels of 2.5 Gbit/s
4 channels of 10 Gbit/s
1 channel of 40 Gbit/s

dwdm2 12/4/2012 | 9:20:34 PM
re: Poll Paints Bright Future for CWDM Peter wrote: "...1. Right now, most metro WDM systems have got less than 8 channels lit. So CWDM would do the job."

I always thought a direct comparison of CWDM and DWDM is not the most meaningful thing.

Frankly, there are applications where CWDM is appropriate and DWDM is not applicable (yet). These are applications where wider passband is necessary.

On the other hand, where narrow channel spacing and higher channel count are required, CWDM is not what can do the job.

The striking difference, IMHO, is discrete vs. integrated technology; pretty soon most DWDMs are gonna be on a chip. DWDM is also cheaper on per lambda basis.

Now coming back to scalabity issue, CWDM would not be able to keep up the pace, DWDM is essential in metro applications. May be only 8 channel is lit now, but obviously this is only the beginning. Besides, on the ITU grid, CWDM leaves out most of the channels that are absolutely necessary to provide metro access.

Comments?
MrLight 12/4/2012 | 9:20:25 PM
re: Poll Paints Bright Future for CWDM There was a past discussion on this topic under
oct.10.02 "Transmode Makes a Little Go a Long Way " http://www.lightreading.com/do...

I posted http://www.lightreading.com/bo...

There is defintely a place for both CWDM and DWDM.

MrLight :-)


BobbyMax 12/4/2012 | 9:20:22 PM
re: Poll Paints Bright Future for CWDM
First of all CWDM is a technology that can be used by the access, metro ntwork and enterprise networks. The good thing avout CWDM is that the wavelength spacing has been blessed by ITU-T.

For the time being CWDM devices consist of 4, 8 or 16 ports. CWDMs can support speeds upto OC-48. Multiple wavelength services can be transmitted over a single fiber. In case of large networks DWDM can be employed.

The CWDM and DWDMs are interoperable. This fact isused in providing end-to-end network management.CWDM can cover distances upto 5-60 kilometers.

The main reson for deployment of CWDM is cheapest cost of transceivers and almost no cross talk due to high channel separation. For it to be deployed in the carriers network, it has pass Telcordia and Nebs3 compliant.

Peter Heywood 12/4/2012 | 9:20:22 PM
re: Poll Paints Bright Future for CWDM nenene66 said:

"Nortel has been shipping CWDM on its switches for 8 months before Cisco."

My understanding is that Nortel has rather a strange version of CWDM. In essence, it's Nortel's DWDM platform with most of the channels disabled, so that the remaining channels are spaced a long way apart - a bit like a comb with most of the teeth missing. I've yet to confirm this with Nortel.

This isn't as whacky as it first sounds because it makes it dead easy to scale - you just light the intermediate channels and hey presto, CWDM turns into DWDM!

Adva offers a similar platform and points out that if you didn't do this, integrating CWDM and DWDM would likely need back-to-back transponders, which would be expensive.

On the other hand, it's tough to see how this arrangement would reap the cost-cutting benefits of genuine CWDM for low channel counts.

Peter



kokoro 12/4/2012 | 9:20:21 PM
re: Poll Paints Bright Future for CWDM In my view the whole thing can be sharply summarised as follows:

- there are applications in the Metro where CWDM is the very right thing to do, both technically and cost-wise
- most of the applications in the Metro are instead more in favour of a smart DWDM, at least adopting a time perspective. CDWM can be a forced solution for some of today's networks, and you'll repent of it quite quickly.
- as regards the interesting question on 16x2.5G / 4x10G / 40G, I would ask additionally "to do what?". What I mean is that we often concentrate on the bare bandwidth, losing sight of the service we wanna provide and of the network topology and maintenance cost.

My basic question is: are carriers thinking on today's networks or tomorrow's networks when they give, if they do so, their virtual preference to CDWM in a generic Metro environment?

Cheers
gea 12/4/2012 | 9:20:20 PM
re: Poll Paints Bright Future for CWDM "This isn't as whacky as it first sounds because it makes it dead easy to scale - you just light the intermediate channels and hey presto, CWDM turns into DWDM!"

Not exactly...for this to work you can't have the CWDM channels that are in the EDFA gain band (1530 to 1565 or so) be lit with CWDM due to the wavelength stability considerations. CWDM transceivers are uncooled, ad so the central CWDM wavelength can vary by aqbout 10nm in either direction. These would kill the DWDM channels.SO this means you can only populate 5 or maybe 6 CWDM channels (out of the 8-wavelength plan) before you have to upgrade to DWDM. (ALso, you need some extra optical coupling devices to mix the CWDM and DWDM bands.)

As for "back to back transponders", there's no reason the single-wavelegnth ports on transponders can be fit with pluggable optics, so that one of the back-to-back transponders would be eliminated (ie, by using CWDM pluggables on the drop side.)

joestudz 12/4/2012 | 9:20:19 PM
re: Poll Paints Bright Future for CWDM <for 1.25="" 20="" 3="" any="" at="" be="" cheapest="" connections?="" ethernet="" example,="" gb="" gigabit="" if="" in="" is="" lambdas="" might="" of="" options="" poll="" provided="" rather="" s,="" service="" solution="" than="" the="" what="">

Did you mean 20 lambdas at 1.25 Gb/s or 16 lambdas at 1.25 Gb/s?

Believe some people tackled 10 Gb/s by using CWDM (8 lambdas at 1.25 Gb/s each.



</for>
Prizm 12/4/2012 | 9:20:19 PM
re: Poll Paints Bright Future for CWDM kokoro wrote:
"- as regards the interesting question on 16x2.5G / 4x10G / 40G, I would ask additionally "to do what?". What I mean is that we often concentrate on the bare bandwidth, losing sight of the service we wanna provide and of the network topology and maintenance cost."

Great point! For example, what if the service provided is 20 Gigabit Ethernet connections? The cheapest solution might be 20 lambdas at 1.25 Gb/s, rather than any of the 3 options in the poll.
The poll seems to have a SONET slant.

Prizm
RGreg 12/4/2012 | 9:20:18 PM
re: Poll Paints Bright Future for CWDM My understanding is that Nortel has rather a strange version of CWDM. In essence, it's Nortel's DWDM platform with most of the channels disabled, so that the remaining channels are spaced a long way apart - a bit like a comb with most of the teeth missing. I've yet to confirm this with Nortel.
---------

Yes, they definitely do that on their long haul Optera platform. I've seen it installed like that in a couple of carrier hotels.


One other thing... in a previous post you said "We had 221 responses and 75% of them were service providers, and 2/3 of the folk that had deployed WDM had deployed 9 or less channels." How many of those carriers were planning on deploying more of those DWDM channels in the next 12-24 months (I can think of at least on carrier that has told me they would)? I think that would be a corollary predictor to the potential CWDM demand.
<<   <   Page 2 / 4   >   >>
HOME
Sign In
SEARCH
CLOSE
MORE
CLOSE