Patent ID: 7155098
Filing Date: 2006-12-26
Classification: C03B,G02B

Abstract:
1. An optical fiber drawn from optical fiber preform manufactured by a method using MCVD (Modified Chemical Vapor Deposition) which forms a clad and a core in a deposition tube by using a flame providing unit reciprocating along an axial direction of the deposition tube, the method repeatedly executing the following process with varying composition of soot generation gas according to a refractive index profile, in which the process comprises the steps of: (a) forming a soot layer having pores on an inner surface of the deposition tube by inducing soot generation reaction at a temperature lower than a soot sintering temperature with putting soot generation gas in a halide group together with oxygen gas in the deposition tube; (b) removing hydroxyl groups existing in the soot layer with keeping the pores by putting dehydration gas into the deposition tube; (c) removing chlorine impurities existing in the soot layer with keeping the pores by putting dechlorination gas into the deposition tube; and (d) sintering the soot layer by heating the deposition tube at a temperature above the soot sintering temperature, wherein a peak of hydroxyl group absorption loss at 1385 nm is less than 0.33 dB/Km, an optical loss at 1310 nm is less than 0.34 dB/Km, an optical loss at 1550 nm is 0.20 dB/Km, and a concentration of hydroxyl group and chlorine impurities is less than 1 ppb.