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<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff size=2>Si
rolls of above 900-1000 nm, for 1300-1600 you use GaAs. One way to handle eye
safety is to have</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff size=2>a
negotiation protocol, where the laser runs with fill power, bur very low duty
cycle. Once communication</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff size=2>is
established the duty cycle goes to 100 %. If the link fails, due to the RX not
seeing the TX, the negotiation</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2>protocol is entered, lowering duty cycle below 1%</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff size=2>The
result is that a bird or human getting into the optical path will lower the
energy so the beam will still</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff size=2>be
eyesafe, until both units see each other with proper levels, meaning there is
nothing in the path.</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2>Remember, police laser speed guns with watts of power are considered
eyesafe due to the low duty cycle.</FONT></SPAN></DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=160011111-03032008><FONT face=Arial color=#0000ff
size=2>Gullik</FONT></SPAN></DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Ursprungligt meddelande-----<BR><B>Från:</B>
ronja-bounces+gullik.webjorn=flysta.net@lists.pointless.net
[mailto:ronja-bounces+gullik.webjorn=flysta.net@lists.pointless.net]<B>För
</B>Pramod yaduvanshi<BR><B>Skickat:</B> den 3 mars 2008 02:57<BR><B>Till:</B>
Twibright Ronja<BR><B>Ämne:</B> [Ronja] IR vs Visible<BR><BR></FONT></DIV>
<DIV>In IR Photodiodes will have a better response too!! since Silicon PIN
diodes have higher responsivity at IR frequencies ..am not sure if there are
Lasers and PIN available at a 1300 0r 1500 nm !! If there are then they will
be eye safe and can pump in more power unlike 850nm !! Does any one know of
some cheap Lasers and diodes in this band? 1300/1500nm? </DIV>
<DIV> </DIV>
<DIV>PK Yaduvanshi<BR><BR> </DIV>
<DIV><SPAN class=gmail_quote>On 03/03/2008, <B
class=gmail_sendername>eldis111</B> <<A
href="mailto:eldis111@seznam.cz">eldis111@seznam.cz</A>> wrote:</SPAN>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Is
there reason not-to stay in IR? Only advantage I can think is easier
aiming..<BR>We installed many IR (professional) FSO, it is even faster than
making radio link (at least around 10GHz).<BR>Higher wavelength => better
SNR due to losses in atmosphere and interference from other sources.<BR>But
there might be another reasons.. So, what is your
opinion?<BR><BR>eldis<BR><BR><BR>> Everything is fine... if you stay in
the IR spectrum.<BR>> if someone could find visible light high power
VCSELs, that would be fine...<BR>> Bye,<BR>> Martin<BR>><BR>>
eldis írta:<BR>> > As Gullik says, VCSEL are much better than ordinary
laser,<BR>> > just look at google.<BR>> > To me, it seems that
VCSEL combines good things from laser and led into<BR>> > one
package.<BR>> ><BR>> > eldis<BR>> ><BR>> ><BR>>
><BR>> >> What is crappy about VCSEL?s?<BR>> >><BR>>
>> To me they seem ideal, circular beam, no or very little<BR>>
>> astigmatism, low threshold current, good efficiency,<BR>>
>> fast ( ghz) relatively robust, low cost.<BR>> >><BR>>
>> Why do you not like them?<BR>> >><BR>> >>
Gullik<BR>> >><BR>> >> -----Ursprungligt
meddelande-----<BR>> >> Fran: ronja-bounces+gullik.webjorn=<A
href="mailto:flysta.net@lists.pointless.net">flysta.net@lists.pointless.net</A><BR>>
>> [mailto:<A
href="mailto:ronja-bounces+gullik.webjorn=flysta.net@lists.pointless.net">ronja-bounces+gullik.webjorn=flysta.net@lists.pointless.net</A>]For<BR>>
>> Gyurko Martin<BR>> >> Skickat: den 1 mars 2008
22:58<BR>> >> Till: Twibright Ronja<BR>> >> Amne: [Ronja]
vcsel-s retail<BR>> >><BR>> >><BR>> >>
Hi!<BR>> >><BR>> >> For those who want these crappy
lasers:<BR>> >><BR>> >> <A
href="http://www.roithner-laser.com/VCSELs.htm">http://www.roithner-laser.com/VCSELs.htm</A><BR>>
>><BR>> >> May them work for you.<BR>> >><BR>>
>> Martin<BR>> >><BR>> >><BR>> >><BR>>
><BR>> ><BR>> ><BR>><BR>> --<BR>> Twibright Ronja
mailing list <A
href="http://ronja.twibright.com">http://ronja.twibright.com</A><BR>> <A
href="mailto:Ronja@lists.pointless.net">Ronja@lists.pointless.net</A><BR>>
<A
href="http://pointless.net/mailman/listinfo/ronja">http://pointless.net/mailman/listinfo/ronja</A><BR>><BR>><BR>><BR><BR>--<BR>Twibright
Ronja mailing list <A
href="http://ronja.twibright.com">http://ronja.twibright.com</A><BR><A
href="mailto:Ronja@lists.pointless.net">Ronja@lists.pointless.net</A><BR><A
href="http://pointless.net/mailman/listinfo/ronja">http://pointless.net/mailman/listinfo/ronja</A><BR></BLOCKQUOTE></DIV><BR><BR
clear=all><BR>-- <BR>Tel: +91 9940589851 </BLOCKQUOTE></BODY></HTML>