Precision length standard for coherent laser radar

Abstract

This disclosure presents a version of a coherent laser radar system that is immune to environmental effects on Mach-Zehnder-configured interferometers and reference length standards comprising such systems. The present disclosure also describes methods and materials which alleviate interferometer drift due to vapor absorption using a polyimide coated polarization maintaining fiber to reduce the change in the length of a reference arm.

1 . A substantially hydrophobic and substantially non-outgassing coating for optical fibers, whereby the optical fiber maintains substantial dimensional and refractive stability.  
   
   
       2 . The coating of  claim 1  wherein the coating is a polymer.  
   
   
       3 . The coating of  claim 1  wherein the coating is selected from the group consisting of: Ultraviolet Cured Acrylate, Teflon, DuPont Tefzel, Hytrel, and Nylon.  
   
   
       4 . The coating of  claim 1  wherein the coating comprises a metal.  
   
   
       5 . The coating of  claim 2  wherein the polymer is polyimide.  
   
   
       6 . A method of preserving optical path length and polarization maintaining properties of optical fibers comprising coating an optical fiber with a substantially hydrophobic and substantially non-outgassing coating.  
   
   
       7 . The method of  claim 6  wherein the coating is a polymer.  
   
   
       8 . The method of  claim 6  wherein the coating is selected from the group consisting of: Ultraviolet Cured Acrylate, Teflon, DuPont Tefzel, Hytrel, and Nylon.  
   
   
       9 . The method of  claim 6  wherein the coating comprises a metal.  
   
   
       10 . The method of  claim 7  wherein the polymer is polyimide.  
   
   
       11 . In a fiber optic interferometer, the improvement comprising at least one optical fiber coated with a substantially hydrophobic and substantially non-outgassing coating, whereby the optical fiber maintains substantial dimensional and refractive stability.  
   
   
       12 . The improvement of  claim 11  wherein the fiber optic interferometer is a reference standard in a laser distance measuring apparatus.  
   
   
       13 . The coating of  claim 11  wherein the coating is a polymer.  
   
   
       14 . The coating of  claim 11  wherein the coating is selected from the group consisting of: Ultraviolet Cured Acrylate, Teflon, DuPont Tefzel, Hytrel, and Nylon.  
   
   
       15 . The coating of  claim 11  wherein the coating comprises a metal.  
   
   
       16 . The coating of  claim 13  wherein the polymer is polyimide.