Open Commentary Pathology's New Role: Defining Disease Process and Protective Responses

A singlemode optical fiber 700 having very low loss at 1385 nm, and a practical method for making same are disclosed. A core rod 20 is fabricated using vapor axial deposition to have a deposited cladding/core ratio (D/d) that is less than 7.5. The core rod is dehydrated in a chlorine- or fluorine-containing atmosphere at about 1200 DEG C. to reduce the amount of OH present to less than 0.8 parts per billion by weight, and then consolidated in a helium atmosphere at about 1500 DEG C. to convert the porous soot body into a glass. The consolidated core rod is elongated using an oxygen-hydrogen torch that creates a layer of OH ions on the surface of the rod that are largely removed by plasma etching. Finally, the core rod is installed in a glass tube 40 having a suitably low OH content. Thereafter, the tube is collapsed onto the rod to create a preform 60. Conventional methods are employed for drawing an optical fiber from the preform and applying one or more protective coatings 75, 76. The disclosed method is suitable for commercial production of low-OH fiber. Significantly, the fiber's loss at 1385 nm is reduced to a level that is less than its loss at 1310 nm, thereby rendering the entire wavelength region 1200-1600 nm suitable for optical transmission. In particular, wave-division-multiplex systems are now available to transmit optical signals over distances greater than 10 km in the wavelength region between 1360 nm and 1430 nm.