Re: APC vs. AFC: confused


JoS wrote:
Thank you for your reply.
Another thing I did not define well in this discussion was that we
observe this pattern even when we used 514nm which is well above the
cutoff of 470nm.
ad 1)As a source we use an Argon multi wavelength Laser. The beam is
modified by an AOTF which selects the wanted lambda and turns the
polarization by 90°. We had an old setup where the laser the AOTF and
the coupler were in line. Now we changed to a setup where we employ two
mirrors for the adjustment of the beam. So our source now is this laser
then two mirrors then the AOTF and finally the coupler. So the beam
should be polarized parallel to the breadboard and parallel to the slow
axes. We changed the setup because the old one was not stable. And now
with the new one we do not get much light through the fiber.
ad 2)Besides the lenses in the coupler (focal length: 3.5mm, achromat
lens) there are no lenses in the optical path prior to the coupler.
ad 3) I have not been able to find out the numerical aperture and the
attenuation coefficient of our fiber. It is a polarization maintaining
fiber (PANDA). The length is 3m.
With the old setup we go much higher output powers after the fiber.

regards
reinhard


The other options

it is possible that you are coupling nearly all you light into the
cladding, and that although the cladding modes are rapidly attenuated,
there is still a residual at the output of your relativeyl short fibre.
The pattern would be more speckle like with this theory, whereas I
suspect that a coupling of different polarisation modes would have
reasonabley defined lobes.

Of course as you first pointed out your fibre could be damaged.

To check this I'd strip the system down to the laser and fibre coupling
arrangement, and test with no AOTF or mirrors so that these can all be
eliminated as potential causses of your problem. As you have achieved
resonable coupling before it is good to that stage to determine wher
thisngs could be going wrong, and then add one component at a time.

cheers

David

.

Relevant Pages

  • Re: APC vs. AFC: confused
    ... This is done by passing the fiber between your fingertips which are very sensitive. ... Now we changed to a setup where we employ two ... then two mirrors then the AOTF and finally the coupler. ... it is possible that you are coupling nearly all you light into the ...
    (sci.optics.fiber)
  • Re: Problem with Laser-fiber coupler
    ... Did you match the NA of your PM fiber with the NA of the OZ ... I'm coupling it with the He-Ne laser using a OZ Optics Coupler ... Obviously I suggested to use FC-APC connector, ...
    (sci.optics)
  • Re: Rolling stock connectors and uncouplers.
    ... >> I now have a small number of Bachmann Loco's and am looking for a more ... > There are many, eg the Jackson coupling, which is inconspicuous and can be ... it all depends how unrealistic you are willing to let the coupler be. ... > You want inconspicuousness, reliability, and ease of uncoupling. ...
    (uk.rec.models.rail)
  • Re: APC vs. AFC: confused
    ... According to the data sheet I have this was a special order fiber. ... Now we changed to a setup where we employ two mirrors for the adjustment of the beam. ... So our source now is this laser then two mirrors then the AOTF and finally the coupler. ... You are operating a single mode fibre below its cut off wavelength. ...
    (sci.optics.fiber)
  • Re: APC vs. AFC: confused
    ... After stripping down our system to just the laser and the coupler we were able to get good transmission (at least our fiber is in a good shape). ... When we tried to reproduce the good coupling we achieved without the AOTF we failed. ...
    (sci.optics.fiber)