79afd1b6   
   XPost: sci.optics.fiber   
   From: siegman@stanford.edu   
      
   In article ,   
    Joseph Gwinn  wrote:   
      
   > In article   
   > <3d5756f6-67c6-4144-85da-9b6d71e671b5@q33g2000pra.googlegroups.com>,   
   >  laser  wrote:   
   >   
   > > Does anyone know how to measure the doping profile and refractive   
   > > index profile of optical fiber amplifier?   
   >   
   > Many people know.  It's in all the textbooks, having been worked out between   
   > 1975 and 1985, or so.  Do the research.  Here are some starting points.   
   >   
   > For communications fibers, multimode is ~parabolic, while for single-mode   
   > it's   
   > step index, with perhaps a few stepped rings.   
   >   
   > For carriage of gross amounts of optical power, it's usually a larger   
   > stepped-index fiber than for communications.   
   >   
   > The difference in refractive index between core and cladding is 1% to 2%.   
   >   
   > Joe Gwinn   
      
   I suspect you'll agree, however, that when you look at the actual (i.e.,   
   measured) index profiles of real fibers, they often display horrible   
   looking spikes and irregular small-scale variations about these   
   idealized parabolic or step index profiles -- irregularities that lead,   
   in most cases, to very little or practically no real difference in   
   actual mode propagation.   
      
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