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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
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NNTP-Posting-Date: Fri, 6 Dec 2002 20:37:07 +0000 (UTC)
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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.
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