Why the quantum internet should be built in space

[jim bell]

 A "bel",  https://en.wikipedia.org/wiki/Decibel    is a logarithmic measure of relative amplitude, most commonly used when values vary by many factors of 10.  While most people think of it in terms of sound intensity, it is also a description of radio signal strength, antenna gain, and other values.  
a "3 decibel" difference is approximately a factor of 2 in power.   So, if an optical fiber has an optical loss of "0.15 dB/kilometer", that means that 20 kilometers of fiber has about 20 kilometers x 0.15 dB/kilometer = 3 dB loss, or a factor of 2 in power.--Despite the fact that I had absolutely nothing to do with selecting my name, I can manage a minor gloat by saying that I am one of  few people whose name is also the name of an ASCII character:   https://en.wikipedia.org/wiki/ASCII 

(Jim) Bel(l)Tab (Hunter)Del  (Webb, or Shannon)


    On Sunday, January 5, 2020, 02:06:11 PM PST, \0xDynamite <dreamingforward at gmail.com> wrote:  
 
 > But even at about 1550 nanometers, 50 kilometers of fiber has:  50 km x 0.15 dB/km  = 7.5 dB of optical loss

Isn't there a better unit than Bells (dBs) for optics, like
transparency or opacity?  It seems Bells are directly related to air
pressure....

Mark
  
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