Date: Thu, 27 Apr 2000 16:19:33 -0400
From: Alexander Kojevnikov
To: "kettell@bnl.gov"
Subject: Cleaving or polishing.

I was trying to resolve a question of polishing vs cleaving.

I have made a position scan with a fiber end approximately 1 inch away from PMT window in one direction approximately through a PMT window diameter. I did it two times with one fiber. Once with a 10 meter long, second with 5 meters cut away ( 5 meters left) and fiber end redone from scratch. Other end was fixed from the very beginning.

Each time I did the following:

First scan with cleaved end 3 passes. So each point scanned 3 times with repositioning in between.
Then I polished the end to 3 microns and again did 3 passes.
For 5 meters case I did also 0.3 micron polishing and did the scan again.

Pictures are in 10 m and 5m . I was not trying to do positioning precisely, so the random positioning error should be about 1/8 inch. On plots are mean values and sigmas for 3 measurements for each position point.

From this data I also have estimated the loss of light in fiber itself for our wavelength. I took the mean values summed for 3 central points for 10m and 5m length and got about 7% loss on the 5 meter length. This means about 1,3% per meter. This result is very close to as it should be from the literature.