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Optical noise cancellation

Discussion in 'Electronic Design' started by Hüseyin Rahmi Seren, Feb 23, 2007.

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  1. How can optical noise be canceled by dividing two inputs from the same
    light source? Any idea?
  2. Phil Hobbs

    Phil Hobbs Guest

    "Laser noise cancellers"


    Phil Hobbs
    I really did not think that someone was going to write a reply.
  4. Phil Hobbs

    Phil Hobbs Guest

    Most of us try to be helpful round here...provided that the person
    posting looks like he's willing to make some effort, and that it isn't
    an obvious homework problem.

    Besides, laser noise cancellers are a bit of a hobby of mine.


    Phil Hobbs
  5. Hello again,

    Mr Hobbs,

    I built one of your circuits (Fig-3 in the paper "Ultrasensitive laser
    measurements without tears"). In principal it worked. However, I see
    lots of internal oscillations which can be considered as noise. For
    example whenever the signal beam becomes zero an oscillation around
    1.5 MHz appears. Also, there is another oscillation which periodically
    appears and exponentially diminishes. Do you have any suggestions or
    experience about this?
    Thanks very much.
    Best wishes.
  6. Phil Hobbs

    Phil Hobbs Guest

    Just saw this news provider ( is dropping a lot
    of posts.

    Your feedback loop is oscillating. This could be due to inadequate
    bypassing, poor layout, or even hanging a coaxial cable on the output of
    an op amp with no isolation resistor.

    If you can send me an actual schematic, I'll have a look at it, but that
    exact circuit works very well--the New Focus "Nirvana" detector is just
    that circuit in a nice box, for which they'll charge you $1500. (The
    email address above actually works, spam block and all.)


    Phil Hobbs
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