Why should we turn off mobile phones when we travel in an airplane, Part 1

This video is funny. But some of the challenges from the passengers are quite true.

• "90-Million -dollar aircraft can't ignore the signals from my 40-dollar iPod Shuffle?"
• "Can I hold this plane hostage with my (Nintendo) 3DS?"
• "How come the plane is not interfering with my phone?"
• "Why don't other phones interfere my phone?"
• "I just always leave my phone on and nothing happened?"

I think all the fears of "interferences to navigation" was because of some sound like this one.

WDM, DWDM, and CWDM

Wavelength-division Multiplexing (WDM) is a technology we can put several laser light beams into the same optical fiber. The light beams are identified by their unique physical properties: wavelengths. Because of this, all such technologies are collectively called Wavelength-division Multiplexing.

By TotoBaggins on Wikipedia.