Double-clad optical fiber for lasers and amplifiers

Abstract

A double-clad optical fiber includes a core, a multimode inner cladding disposed about the core, and a second cladding layer disposed about the inner cladding. The core includes an active material for absorbing pump radiation received by the inner cladding. The multimode inner cladding includes truncated regions including a first material, where the first material has an index of refraction that is different than the material of the inner cladding that surrounds said truncated regions, for promoting the scattering of pump radiation propagating in the multimode inner cladding for increasing the absorption of the pump radiation by the active material of the core. The truncated regions can include voids that are empty or that comprise a gas. Particles can be distributed in a soot and/or voids formed in the soot, where the soot can be deposited via Outside Vapor Deposition for forming the truncated regions in an optical fiber drawn from a preform.

Having described the invention, what is claimed as new and to be secured by Letters Patent is:  
     
         1 . A method of forming a cladding for being disposed about the core of an optical article, comprising the steps of: 
 providing an elongate glass article;    adhering a layer of soot to the elongate glass article for forming a portion of the cladding so as to be disposed about the core when present;    sintering the layer of soot to form a first sintered layer including voids that are at least one of empty or comprising a gas;    adhering a different layer of soot to the elongate glass article for forming a different portion of the cladding so to be disposed about the core when present;    sintering the different layer of soot to form a different sintered layer substantially free from voids; and    disposing a second cladding about the cladding, the second cladding comprising an index of refraction lower than an index of refraction comprised by the cladding.    
     
     
         2 . The method of  claim 1  including drawing the elongate glass article into a glass fiber.  
     
     
         3 . A method of forming a cladding for being disposed about the core of an optical article, comprising the steps of: 
 providing a hollow elongate glass article;    adhering a layer of soot to a surface of the elongate glass article for forming a portion of the cladding so as to be disposed about the core when present;    sintering the layer of soot to form a sintered layer including voids that are at least one of empty or comprising a gas;    providing a second elongate glass article for providing one of at least a portion of the core and a different portion of the cladding where the different portion is substantially free of voids; and    oversleeving one of the glass articles with the other of the glass articles.    
     
     
         4 . The method of  claim 3  including drawing the oversleeved glass articles into a glass fiber.  
     
     
         5 . A method of forming a cladding for surrounding the core of an optical article, comprising the steps of: 
 providing an elongate glass article;    adhering a layer of soot to the elongate glass article for forming a portion of the cladding so as to be disposed about the core when present;    sintering said layer of soot to form a first sintered layer of the cladding;    adhering a different layer of soot to the elongate glass article for forming a different portion of said cladding so as to be disposed about the core when present;    exposing only the different layer of soot to a selected material in the form of a gas or liquid for absorption by the different layer of soot; and    sintering the different layer of soot to form a second sintered layer of said cladding.    
     
     
         6 . The method of  claim 5  including drawing the elongate optical fiber into a glass fiber.  
     
     
         7 . A method of forming a cladding disposed about the core of an optical article, comprising the steps of: 
 providing an elongate glass article;    adhering a layer of soot to the elongate glass article for forming a portion of the cladding so as to be disposed about the core when present;    distributing particles having an index of refraction different than the index of refraction of the soot with the layer of soot; and    sintering the soot layers.    
     
     
         8 . The method of  claim 7  including drawing the elongate glass article to form a glass fiber.  
     
     
         9 . A method of forming a cladding for being disposed about the core of an optical article, comprising the steps of: 
 providing a hollow elongate glass article;    adhering a layer of soot to the inside of the elongate glass article for forming a portion of the cladding so as to be disposed about the core when present;    exposing the layer of soot to a selected material in one of a gas and liquid form for absorption by the soot;    sintering the soot;    providing a second glass article for providing one of at least a portion of the core and a different portion of the cladding; and    oversleeving one of the glass articles with the other of the glass articles.    
     
     
         10 . The method of  claim 9  including drawing the glass articles into a glass fiber.  
     
     
         11 . A method of forming an elongate optical article having a core and a cladding disposed about the core, the cladding having an index of refraction that is less than the index of refraction of the core, comprising the steps of: 
 providing an elongate glass article;    adding glass to the article for forming a first part of the cladding so as to be disposed about the core when present, the added glass including discrete regions having a different index of refraction than the added glass; and    adding glass without discrete regions to the elongate glass article for forming another part of the same cladding so as to be disposed about the core when present.