Patent ID: 8297080

Claim:
A method for producing a single-mode fiber for submarine cables comprises the steps of: a) washing a preform using a mixed solution comprising nitric acid and hydrofluoric acid with a weight ratio thereof of 1:2-8 and an acid concentration of the mixed solution being 30-80%, and treating the preform using flame polishing to remove 10-100 μm silica from the surface thereof; b) fixing the preform on a fiber drawing furnace comprising a graphite heating element and a stainless steel furnace, an ash content of the graphite heating element being less than or equal to 20 ppm and a surface roughness thereof being less than or equal to 6.3, above the graphite heating element disposed an upper, a middle, and a lower gas inlet pipe, and gas moving therein in the form of laminar flow; drawing the preform at a temperature of 2,000-2,300° C., with a gas flowrate of 10-50 L/min and a speed fluctuation of less than 20 m/min; cooling resultant bare fibers, coating each fiber with a first coating layer and curing therein using an UV-curing device, coating with a second coating layer and curing therein using the UV-curing device, sine twisting the fibers using a sine-twisting wheel, and taking up the fibers using a double take-up system; c) collecting the fibers produced by the middle of the preform and selecting a fiber with a screening strain of 2%; and d) testing the properties of subsections of each fiber using a fiber testing instrument, and calculating averages of the properties of the subsections to represent parameters of the fiber, a zero dispersion wavelength thereof being 1,300-1,324 nm, a zero dispersion slope being less than or equal to 0.092 ps/(nm 2 km), a cable cutoff wavelength being less than or equal to 1,260 nm, a mode field diameter being 9.2±0.4 μm, an attenuation at 1,310 nm being less than or equal to 0.35 dB/km, and an attenuation at 1,550 nm being less than or equal to 0.21 dB/km.