Just a follow up to the GRIN lens thread.
It seems likely to me that the GRIN technology is a spin off of the
fiber optic industry. Multi mode fiber has the same kind of gradient
index of refraction across it's diameter and the way they get it is by
starting with a 4" to 5" rod with the same proportional properties. The
beginning and end of the original rod are unusable for Fiber production
but would be very temping to an optician. My guess is the the gradient
is not predictable enough for lens use.
In the early days of fiber installations it turns out it wasn't good
enough for the future communication needs either. There are miles of
installed fiber that are starting to cause problems in the local
networks due to just these inconsistencies. When used with more modern
laser transmitters (I believe they have a narrower freqencey output or
something) the glass fiber shows unexpectedly high losses. These older
networks require a Mode Conditioning Patch cord that purposely injects
the laser source off center to avoid the discontinuity in the center of
the fiber.
This is all just supposition and conjecture, but it kind of makes sense
to me. I'm sure there are other views and/or opinions. If so, I'd like
to hear them.
Mike Butler
Dublin, California
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