transmittance @ 1550 nm

Hi - I'm working on a project to measure atmospheric turbulence using
transmissions from a 1550 nm laser and a receiver built around an
off-the-shelf telescope
(like the Meade LX and RCX series). I'm trying to find out, roughly,
what the transmission losses are at this wavelength, and the Meade
technical guys don't seem to answer their telephones.

Does anyone out there have a ball park idea what the losses are for
these telescopes at this
wavelength ?


Thanks
Alan


p.s. I'm trying to build a simpler version of the instrument described
in


http://www.dur.ac.uk/g.d.love/downlo...slodar2005.pdf

In message . com, al
writes
Hi - I'm working on a project to measure atmospheric turbulence using
transmissions from a 1550 nm laser and a receiver built around an
off-the-shelf telescope
(like the Meade LX and RCX series). I'm trying to find out, roughly,
what the transmission losses are at this wavelength, and the Meade
technical guys don't seem to answer their telephones.

Does anyone out there have a ball park idea what the losses are for
these telescopes at this
wavelength ?


Thanks
Alan


p.s. I'm trying to build a simpler version of the instrument described
in


http://www.dur.ac.uk/g.d.love/downlo...slodar2005.pdf


I can't answer your question, but I'm curious about why 1.55um

I use one of these at work to do the same job, it uses two lots of 450
red leds

http://www.scintec.com/Site.1/PDFs/01_LayBLS.pdf

Brian

--
Brian Howie

al wrote:
Hi - I'm working on a project to measure atmospheric turbulence using
transmissions from a 1550 nm laser and a receiver built around an
off-the-shelf telescope
(like the Meade LX and RCX series). I'm trying to find out, roughly,
what the transmission losses are at this wavelength, and the Meade
technical guys don't seem to answer their telephones.

Does anyone out there have a ball park idea what the losses are for
these telescopes at this
wavelength ?


Around 75-80%

Andrea T.

Alan
Most glasses are reasonably transmissive out to about 2um so you shouldn't
be troubled by absorption losses.

However, the performance of Anti Reflection (AR) coating on most telescope
optical surfaces is normally optimised for visible wavelenghts and may
not be well defined for 1.5um so you may want to verify that before going
too much further.

Unfortunately, I can't guess at the performance of any Meade coatings , so
you probably will have to persevere with the phone calls.

HTH

Iain


"al" wrote in message
ups.com...
Hi - I'm working on a project to measure atmospheric turbulence using
transmissions from a 1550 nm laser and a receiver built around an
off-the-shelf telescope
(like the Meade LX and RCX series). I'm trying to find out, roughly,
what the transmission losses are at this wavelength, and the Meade
technical guys don't seem to answer their telephones.

Does anyone out there have a ball park idea what the losses are for
these telescopes at this
wavelength ?


Thanks
Alan


p.s. I'm trying to build a simpler version of the instrument described
in


http://www.dur.ac.uk/g.d.love/downlo...slodar2005.pdf

Hi Brian
I'm interested in 1.55 because it's eye-safe and also because it's
often used in telecommunications.

al

Brian Howie wrote:
In message . com, al
writes
Hi - I'm working on a project to measure atmospheric turbulence using
transmissions from a 1550 nm laser and a receiver built around an
off-the-shelf telescope
(like the Meade LX and RCX series). I'm trying to find out, roughly,
what the transmission losses are at this wavelength, and the Meade
technical guys don't seem to answer their telephones.

Does anyone out there have a ball park idea what the losses are for
these telescopes at this
wavelength ?


Thanks
Alan


p.s. I'm trying to build a simpler version of the instrument described
in


http://www.dur.ac.uk/g.d.love/downlo...slodar2005.pdf


I can't answer your question, but I'm curious about why 1.55um

I use one of these at work to do the same job, it uses two lots of 450
red leds

http://www.scintec.com/Site.1/PDFs/01_LayBLS.pdf

Brian

--
Brian Howie

"al" wrote in message
oups.com...
Hi Brian
I'm interested in 1.55 because it's eye-safe and also because it's
often used in telecommunications.

al

It's often used in the higher-end and long distance telecom equipment
because of optimum Glass Opacity at these wavelengths. Don't count on it
being eye-safe though as most Telecom kit advises (strongly) against looking
into the laser.

Regards


Chris

"al" wrote in message
oups.com...
Hi Brian
I'm interested in 1.55 because it's eye-safe and also because it's
often used in telecommunications.


We sell fibre devices with 1550 um transmitters. They all carry warnings
about possible eye damage. Are you sure that they are safe?

Regards


Donal
--

"Chris Taylor" wrote in message
...

"al" wrote in message
oups.com...
Hi Brian
I'm interested in 1.55 because it's eye-safe and also because it's
often used in telecommunications.

al

It's often used in the higher-end and long distance telecom equipment
because of optimum Glass Opacity at these wavelengths. Don't count on it
being eye-safe though as most Telecom kit advises (strongly) against
looking into the laser.
Dead right.
The 'point' about wavelengths above 1400nm, is that the eye is not
considered to automatically 'focus' these, so the limits rise to those for
'distributed' light, rather than those for 'focussed' light. However the
limits are reduced for all IR radiation, because the 'blink reflex', does
not apply. It is still not inherently 'safe', and this must be considered
in anything using such wavelengths. The short pulse used in Lidar, does
allow quite high instantaneous powers to be used, but great care is still
needed.

Best Wishes