公开(公告)号：CA2111011A1

公开(公告)日：1994-07-30

申请号：CA2111011

申请日：1993-12-09

Applicant: CORNING INC

Inventor： ALLEGRETTO ALLEN E ,  ATWOOD THOMAS J ,  REDING BRUCE W ,  TRUSTY ROBERT M

IPC: C03C25/42 ,  G01B11/06 ,  G01B11/10 ,  G01M11/00 ,  G01N21/45 ,  G02B6/44 ,  G02B6/16 ,  C03C25/02

Abstract: A method for monitoring the thickness of a hermetic coating on an optical waveguide fiber is provided in which an interference pattern is produced by illuminating the fiber with a laser beam. A spatial frequency spectrum is generated for the interference pattern and a first component of that spectrum, corresponding to the outside diameter of the fiber, is identified. The magnitude of this component is inversely related to the thickness of the coating, i.e., the magnitude decreases as the coating thickness increases, and thus this magnitude can be used to monitor the thickness of the coating during, for example, the coating process. Effects of fluctuations in the power of the laser beam and/or movement of the fiber relative to that beam can be minimized by normalizing the magnitude of the first component by the magnitude of the DC component of the spatial frequency spectrum.