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Homework Help: Optical Fibers

  1. May 18, 2007 #1
    Hi guys,

    can anyone help me with this question?-

    An optical fiber has a loss of 0.8dB/km at a wavelength of 1250nm. If 120uW of power is injected into the fibre at the transmitter, how much power would be lost at a distance of 20km down the fibre, also calculate the energy loss over a 24hr period?

  2. jcsd
  3. May 18, 2007 #2

    Doc Al

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    Staff: Mentor

    What's the meaning of 0.8 db? If you're not sure, review here: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/db.html" [Broken]
    Last edited by a moderator: May 2, 2017
  4. May 18, 2007 #3


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    Staff Emeritus
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    Welcome to the forums,

    Have you made any attempt at this question yourself? My first suggestion would be to figure out how dB relates to power...

    Edit: This is getting to be a regular occurrence Doc :redface:
  5. May 19, 2007 #4


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    Doc Al is putting you on the right track. But his dB reference may be confusing to someone just learning about power relationships. Here's another reference to shed more light. You will see some examples relating power.
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