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DWDM and other Light Spectrum Wavelengths (Nanometer vs Frequency)

kfarrington
Level 3
Level 3

Hi all,

Please may I ask a couple of questions.

1. What is the range of frequencies that DWDM uses. Is there a defined band of the EM spectrum where all laser/light frequencies can operate at?

2. Why do we mesaure all laser and optical light carriers as NM wavelengthsize, ie 850nn, 1310nm etc etc, and why dont we just use the term freqeuncy in Thz? After all, all other ranges within the spectrum use the primary term of frequency and not wavelength size?

Many thx indeed,

Ken

20 Replies 20

Many thx indeed Tom!!

BIG 5 for you. Excellent response!

many thx mate

Ken

viyuan700
Level 5
Level 5

Hi Ken,

1. For DWDM C& L bands are used and they are C 1530-1565nm L from 1565-1625.

U can see this link to see other bands use

http://en.wikipedia.org/wiki/Fiber-optic_communication

We use only these bands for DWDM as in other range we dont have Optical amplifier which are good as those works in C & L bands.

2. I think you use nm for optical wavlenth as they are easier to speak (my opinion if you see at smaller frequency u say 900MHz, 2.4 Ghz, 5Ghz ) but u have seen in your conversion that how complicated number becomes when you have to tell them in THz. In nm it is number which you can communicate easily like 850nm, 1300 nm, 1530nm etc

You conversion formula is right

C(Speed of light)3X10^8= V (frequency in Hertz)* Lambda in m.

So when u convert m into nm you get that 10^17.

In DWDM bands for fast convertion remember if 2 DWDM wavelngths are

0.8nm apart then in frequency they are 100GHz

0.4nm=50GHz

0.8nm=100GHz

1.6nm-200GHz

If you have spoke to anybody speaking about DWDM bands u will hear that wavelngths are 50G apart or 100G apart.

So i think we jsut use where number are easire to use whether it is frquncy or wavelngth.

Hi there, I just posested a reponse about the confusion of ThZ and 100GHz for DWDM. Also, Please look at attachment which I pulled off some DWDMs provider spec sheet?

Many thx to all for the help guys

Ken

Hi Ken, note that the 'code' numbers are vendor specific - different vendors may use different codes. The wavelengths and frequencies for DWDM are defined by the ITU-T in their G.694.1 recommendation.

This does allow even closer spacing (down to 12.5GHz) but commercial DWDM systems are usually 50 or 100GHz.

Richard

jbardgett
Level 1
Level 1

The nm (nanometer) length specification comes from the laser development. Transitions as they are called by folks who founded the laser industry typically refer to the dropping of an electron from one level to another within an atom or molecule in the terms of length. Here is a better explination of the term transition: http://www.rp-photonics.com/laser_transitions.html

Jim ~ optics student at CREOL

Hi Jim,

Many many thanks for that gonna have a good read. Thx for the help.

Kind regards,

Ken

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