The Rainbow
It was around 6:30 in a summer evening. Rain had been stopped, everything was looking neat and fresh. I just woke up, went to the balcony; what a pleasant weather it was! As I am looking around, a vibrant arc caught my eyes. It was a rainbow spanning from the east horizon to the south-east horizon.
It was a long time since I saw a rainbow and first time when I was seeing it from horizon to horizon (thanks to the balcony). It was really looking like a bow. While I was gazing, many thoughts triggered. Indeed, it was lovely.
I remember when first time I used the prism during a science class in school, it seemed magical how a small glass structure can bring out some deep insights of plain & boring white light. A plain sunlight consists of many colors which we cannot normally see or even think about (at least I was in that category). Later I found that we can see a small rainbow by just spraying water in sunlight (it was interesting).
During my secondary school days, I studied how a rainbow formed. How do water droplets and the sun manifest it? Why do we see a rainbow in the sky? Why are there different colors in it? What do different colors represent? In spite of several rainbows in the sky why do we see just one (sometimes two)? Physics is really beautiful.
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It also reminded me of WDM (Wavelength Division Multiplexing), a multiplexing technique used in optical communication systems. Conceptually this technique is similar to what prism does to sunlight (similar at reception end but opposite at transmission end). Signals with different carrier frequencies (representing different colors) combined, transmitted, received, separated, processed, and delivered. Although frequencies are not limited to just different colors’ frequencies (or wavelengths).
Using different versions of WDM, people have achieved the fastest data transfer rates in the world. For example, Some Japanese engineers have achieved speed of 1.02 pbps (~1000 tbps) for around 50 Kms and 319 tbps for around 3000 Kms. Some European researchers in Sweden achieved speed of around 1.8 pbps (which is almost double than the global internet traffic). These records are being challenged every day to achieve even faster rates. (Photonics is a cool name.)
So, doesn’t a simple experiment like using prism in sunlight symbolize one of the most advanced techniques in communication engineering? Well, this is the rainbow to me.
There were clouds in the sky too which were sometimes distorting the view. Sun was about to set. No Sun, No Rainbow (of course we need water droplets too).
“Somewhere over the rainbow, skies are blue, and the dreams that you dare to dream really do come true.” — E.Y. Harburg
