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Speed of DWDM Colors

Speed of DWDM Colors

Speed of DWDM Colors

(OP)
I have a question on why that some wavelengths travel faster than other wavelengths when it is traveling down a fiber. I know when I turn up equipment for a fiber transmission system this comes into play that longer wavelengths are slower. I thought all light travels at around 3 E8 m/sec. So what am I forgeting about.
Just curious,

RE: Speed of DWDM Colors

REFRCTIVE INDEX AND WAVELENGTH COME INTO PLAY.
THE LONGER A WAVELENGTH, THE MORE SPACING BETWEEN EACH TRANSMITTED BIT HENCE THE DELAY.

Gregory Jowi
ojgreg@sprint.ca

Humility is a virtue that is often mistaken for weakness.
It takes more strength of character to seek assistance than to bury one's head in the sand.

RE: Speed of DWDM Colors

The speed of light is a constant in vacuum. In materials the speed is a function of index of refraction. v (actual velocity) = c (speed of light in vacuum) / n (index of refraction).
For telecom fiber n is between 1.5 and 1.6. Hence in fiber light only travels at about 2/3 of 8 x 10^8 m/s.
The index of refraction in fiber is function of the wavelength and therefore each wavelength has a different speed. Look for chromatic dispersion to better understand this phenomena.

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