Low loss cladded optical fibers from halides and process for making same

The process of fabricating a low loss cladded halide fiber waveguide for transmission of infrared frequencies comprising the steps of:

• forming a first ingot of a first halide compound having a first index of refraction;
• forming a second ingot of a second halide compound having an index of refraction less than the first index of refraction;
• forming a polymer-coated cylindrical billet core from the first ingot, said polymer coating comprising a first polymer film means for segregating said first and second halides during extrusion, said polymer means having a radial thickness so that segregation is achieved without appreciable absorption at infrared frequencies;
• forming a sleeve cladding for the cylindrical billet core from the second ingot;
• inserting the polymer-coated core coaxially in the sleeve cladding to form a composite billet;
• heating the composite billet to a temperature that renders the halide compounds and the polymer film ductile;
• and
• extruding the heated composite billet through a die to form a cladded fiber.

The process of fabricating a low loss clad halide fiber waveguide for transmission of infrared frequencies comprising the steps of:

• forming a first ingot of a first halide compound having a first index of refraction;
• forming a second ingot of a second halide compound having an index of refraction less than the first index of refraction;
• forming a cylindrical billet core from the first ingot;
• forming a sleeve cladding for the cylindrical billet core from the second ingot;
• inserting the core coaxially in the sleeve cladding to form a composite billet;
• inserting the composite billet coaxially in a cylindrical tube of non-hygroscopic polymer film and heat shrinking said tube around the composite billet;
• heating the composite billet to a temperature that renders the halide compounds and the polymer ductile;
• and
• extruding the heated composite billet through a die to form a clad fiber having a protective outer polymer coating.

The process of fabricating a low loss clad halide fiber waveguide for transmission of infrared frequencies comprising the steps of:

• forming a first ingot of a first halide compound selected from the group consisting of DCl, NaCl, NaBr and KBr having a first index of refraction;
• forming a second ingot of a second halide compound selected from the group consisting of KCl, NaCl, NaBr and KBr having a second index of refraction less than the first index of refraction;
• forming a cylindrical billet core from the first ingot;
• forming a sleeve cladding for the cylindrical billet core from the second ingot;
• inserting the core coaxially in the sleeve cladding to form a composite billet;
• coaxially covering the composite billet with a non-hygroscopic polymer film;
• heating the composite billet to a temperature that renders the halide compounds and the polymer ductile;
• and
• extruding the heated composite billet through a die at a temperature of betwen about room temperature and about 350.degree. C. to form a clad fiber having a protective outer polymer coating.

The process of fabricating a low loss clad halide fiber waveguide for transmission of infrared frequencies comprising the steps of:

• forming a first ingot of a first halide compound having a first index of refraction;
• forming a second ingot of a second halide compound having an index of refraction less than the first index of refraction;
• forming a cylindrical billet core from the first ingot;
• forming a sleeve cladding for the cylindrical billet core from the second ingot;
• inserting the core coaxially in the sleeve cladding to form a composite billet;
• coaxially covering the composite billet with a non-hygroscopic polymer film;
• heating the composite billet to a temperature that renders the halide compounds and the polymer ductile;
• extruding the heated composite billet through a die to form a clad fiber having a protective outer polymer coating;
• and
• disposing the fiber coaxially in a strength member by disposing the fiber coaxially in a tube of the strength member with a coaxial space between the fiber and the inner surface of the tubing, filling the space with a liquid epoxy, and curing the epoxy to form a highly viscous semi-solid compound for cushioning and protecting the fiber.

A cladded optical fiber for transmission of electromagnetic energy in the infrared region of the spectrum comprising:

• an extrusion of a cylindrical core of a first halide compound having a first index of refraction;
• a coaxial cladding layer disposed around said core of a second halide compound having a second index of refraction less than the first index of refraction;
• and
• a non-hygroscopic polymer film covering said cladding.

A cable for transmission of electromagnetic energy in the infrared portion of the spectrum comprising:

• an extrusion of a cladded optical fiber having a cylindrical core of a first halide compound having a first index of refraction;
• a coaxial cladding layer disposed around said core of a second halide compound having a second index of refraction less than the first index of refraction;
• a first polymer film coaxially disposed intermediate the cylindrical core and the coaxial cladding layer, said first polymer film having a radial thickness less than the thickness which causes appreciable energy absorption at infrared frequencies;
• and
• a strength member coaxially disposed around said extrusion.