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Optical noise cancellation

  • Thread starter Hüseyin Rahmi Seren
  • Start date
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Hüseyin Rahmi Seren

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

Hüseyin Rahmi Seren said:
I really did not think that someone was going to write a reply.
Thanks.

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.

Cheers,

Phil Hobbs
 
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Hüseyin Rahmi Seren

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.
 
P

Phil Hobbs

Hüseyin Rahmi Seren said:
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.

Just saw this now...my news provider (supernews.com) 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.)

Cheers,

Phil Hobbs
 
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