Does the Sky teach you thing or two on Optical Fiber Design ?

Does the Sky teach you thing or two on Optical Fiber Design ?

The Blue Sky, Why ?

Have you ever looked at the open skies and appreciated the absolute feeling of grandeur that it gives to our eyes ? Most of us would have had this experience at some moment or other in our lives, maybe many of us would not remember that moment while for some it must be a time that they may cherish recollecting even today.

That one common thing that we all would have noticed would be the colour of the sky which in its most probability (other than the early sunrise and the Sunset) would be that Beautiful Blue, but how many of us have ever wondered why is it only Blue and not any other colour ? So the basic need is in questioning ourselves, which we rarely do.

I am not going to be philosophical now on and talk things that are purely technical and therefore will relate to the basic operational guidance that must always be kept in mind when we design Optical Fiber networks. So am I going to make some very startling discovery about the colour of the sky and its relative meaning in Optical design, Maybe Yes. Let's give a try

Einstein once said 'If you can't explain it to a six year old, you don't understand it yourself.' and therefore the objective here would be to make it as simple as possible to understand.

Recall those good old days in the school

Even though the sun’s light may look white/yellow/ Orange  it’s actually made up from all the colours of the rainbow which is the visible light spectrum that's a combination of various colours traveling at different wavelengths. We all at some part of our lives would have seen the colour prism, which is a  3D triangle. When light passes through a prism we see all the colours of the rainbow coming out the other end.

In a similar fashion when sunlight reaches the Earth’s atmosphere it’s scattered by the atmospheric prism consisting of  gas molecules and particles in the air. The sunlight that is scattered more is blue than any other colour because its blue that travels in shorter and smaller waves. It's this very reason why we usually see a blue sky. 

Wavelength Matters

Light energy travels in waves. All colours have different sized waves, red having bigger waves and blue having smaller waves which are termed in technical language as wavelengths. Light travels in straight lines unless something obstructs it, a mirror would reflect it, a prism would bend it and gas molecules would scatter it. So what's there up in the sky are gas molecules that scatter it all across on the viewing window on the Top which is the sky.

So now it's a given that light traveling in shorter wavelengths travels less farther than the light traveling in higher wavelengths and this is what forms the base of why all of 300, 500 & 2000 Ethernet fiber communication channel lengths happen at shorter wavelengths of 850 nm while the 1300/1310 or 1550 nm wavelengths being used for farther distances exceeding 2kms. There are also a number of factors such as optical power, mode, polarization that play a role but it's the wavelength that is one of the most deciding factors.

So whenever you get confused on the length and the wavelength, look no further down as the answer lies at the top in the Sky.