I am a newbie to Optical fiber communications and was going through the article on WDM on wikipedia here:
WDM Wikipedia

I also went through the below article on prism diffraction of white light into 7 colors :
Article on dispersion

My question is that in the 2nd article it is mentioned that the white light has been dispersed into:

Violet: 380-450 nm
Blue: 450-495 nm
Green: 495-570 nm
Yellow: 570-590 nm
Orange: 590-620 nm
Red: 620-750 nm

So why can't we use these wavelengths for WDM when it uses the frequencies in the wavelengths of 1310 and 1550? This way we can have a range of 750-380=370nm and if split with 10nm we can have 37 channels rightaway!

Please shed some light on my question considering I am just a newbie.


1 Answer 1


Optical fibers are transparent, but not all transparency is created equal.

Optical fibers are more transparent at 1550 nm and 1310 nm than they are at optical wavelengths. That means that fibers using visible wavelengths could not be as long as fibers that use the IR wavelengths.

Note that "1550 nm" is really a band of wavelengths about 35 nm wide; it's not a single wavelength.


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