Study On High Speed Drawing Process And Properties Of Single Mode Optical Fiber Fabricated By PCVD Process

To increase the drawing speed of optical fiber is an important way to increase the productivity and to reduce the cost of optical fiber fabrication.In recent years,the fast development on application of optical network boosts the market requirement on amount of optical fiber,while the severely competition between different optical fiber manufacturers causes the gradual reduction of fiber price.The position results in the increasing of drawing speed by equipment modification and process optimization.At present,the drawing speed of domestic manufacturers has increased from less than 1000m/min to about 1200m/min. But compared with the highest drawing speed in other countries,the distance is still large.The stability of high speed drawing process and properties of optical fiber produced under high drawing speed were investigated in this dissertation.Some factors which play as obstacles on drawing speed increasing of G652D low water-peak single mode optical fiber fabricated by Plasma Chemical Vapour Deposition(PCVD) process were importantly investigated.The content of paper mainly includes two aspects:the design of high speed drawing process and the optimization on properties of optical fiber.Based on theorical analysis,the speed of drawing towers in Yangtze Optical Fiber and Cable Company Ltd. (YOFC) was increased from 1000m/min to 1600m/min.And the optical fibers produced at 1600m/min have high quality.The main content and achievements include:(1) Problems on unstability of the drawing process at high speed were investigated and solved.Some problems that are easily to occur in process of fiber forming,cooling and coating,and also the methods on problems solving were mainly investaged.A new type of die system used in coating process was designed based on theoretical analysis.By modification on equipment and optimization on drawing process,the average deviation of cladding diameter of fiber can be reduced to less than 0.3μm.The average concentricity of buffer and top coating layers were limited to 2μm and 3μm respectively.(2) Problems on quality degradation of fiber produced at high drawing speed were investigated and solved.The effect of drawing speed increasing on attenuation increase, defects formation inside glass and some geometry properties of optical fiber were investaged in detail.By optimization on annealing of glass fiber,concentration of dopants in core and the viscosity match between core and cladding,the attenuation of fiber produced at 1600m/min can be reduced 0.005-0.006dB/km at 1310nm.By re-designation of refractive index profile and viscosity match of core and cladding,the the concentration of NBOHC defects in fiber core caused by thermo-elastic stress at high drawing speed was reduced.The control of fiber cladding circularity and fiber curl at high speed were also discussed in paper.(3) A new high-speed drawing process of drawing fiber at 1600m/min was developed and put into use for large scale production.With new process,more than 50%of productivity of towers was increased and over 10,000,000km G652D optical fibers were produced.Two years time of production proves that the new process has very good stability and fibers produced are of high quality.(4) Drawing fibers with speed higher than 1600m/min was also investigated in experiment.Drawing fiber at 1800m/min has been successfully realized on one drawing tower with continiously production.The maximum drawing speed can reached to 2000m/min.Optical fibers drawing at 2000m/min can be qualified as standard G652D fiber.