Speed of DWDM Colors

[wpayton]

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,
[sig][/sig]

 

[GregoryJ]

REFRCTIVE INDEX AND WAVELENGTH COME INTO PLAY.
THE LONGER A WAVELENGTH, THE MORE SPACING BETWEEN EACH TRANSMITTED BIT HENCE THE DELAY. [sig]<p>Gregory Jowi<br><a href=mailtojgreg@sprint.ca>ojgreg@sprint.ca</a><br><a href= > </a><br>Humility is a virtue that is often mistaken for weakness.<br>
It takes more strength of character to seek assistance than to bury one's head in the sand.[/sig]

 

[BelAnt]

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.