| 摘要 |
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 fabricate d 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 atmosp here at about 1200.degree.C to reduce the amount of OH present to less than 0.8 part s per billion by weight, and then consolidated in a helium atmosphere at about 1500.degree.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 collapse d 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 les s than its loss at 1310 nm, thereby rendering the entire wavelength region 1200 - 1600 nm su itable for optical transmission. In particular, wave-division-multiplexsystems are nowavailable to transmit optical signals over distances greater than 10 km in the wavelength region between 1360 nm and 1430 nm. |
