The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Bret Cannon"
Subject: Re: current source for array of infrared leds
Date: Fri, 6 Dec 2002 12:33:08 -0800
Organization: One World Telecommunications
References: <firstname.lastname@example.org> <4PMG9.email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: Fri, 6 Dec 2002 20:37:07 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
The HITRAN data base is for gas phase spectra, not liquid spectra and so is
probably not very useful for liquid water absorption.
dgm wrote in message
> Tony Williams wrote in message
> > In article ,
> > Winfield Hill wrote:
> > > Tony Williams wrote...
> > > > Wavelength drift can be pure hell if the IR is going
> > > > through water, because water has a series of deep
> > > > (steep-sided) attenuation notches.... smack bang in
> > > > the 850nm to 950nm region. Been there. :-(((((
> > > Tony, kindly point us to some detailed plots, if you can.
> > I last saw the graph in 1982 Win, after weeks of
> > struggling to find out why my water turbidity
> > meter was so unstable. But yes, it was a graph
> > of optical transmission through water, versus
> > frquency, over the range of about 800-1200nm,
> > showing a series of attenuation notches.
> > I have posted something about this before, and
> > Bill Sloman muttered something about the effect
> > being caused by hydroxyl ions (or something).
> > I'll cc this post to Bill to see if he can come
> > up with an authoritive reference.
> An excellent reference source for absorption data is the HITRAN
> database. See
> I have a previous version on CD, but the most recent version is
> available for download, although the PC you use must be properly
> registered with a name server. If any one has problems with this and
> is still interested in the specific data for water then I can e-mail
> it over in a spreadsheet format. The only point of note is that the
> data in the HITRAN database is designed for spectroscopic applications
> and requires a little massaging to get it into any sort of useful
> A quick look at the data shows pretty low absorption from 840-880nm.
> The main peaks appearing from 880-990 and in particular at 900 and
> In general the low absorption windows also correspond to the
> wavelengths used for optical fibre comms. Removing OH impurities was
> one of the key challenges in fabricating low loss fibres. In fact many
> good texts on fibre optics also include some data on OH absorption or
> at least provide a reference.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup