YOFC is producing all kinds of fibre preforms with the Plasma Activated Chemical Vapor Deposition （PCVD） process. PCVD has been developed by Philips Optical Fibre to deliver an efficient way of producing optical fibres. PCVD can deposit thousands of fine layers in the core and possesses features like highly accurate refractive index control, high deposition efficiency and excellent process flexibility. Thereby, YOFC fibre products show outstanding performance in some key technical specifications, e.g. MFD, bandwidth, PMD and dispersion control. PCVD not only can produce top-quality multi-mode fibres but also performs outstanding in producing single-mode fibre especially single-mode fibre with complicated refractive index profile,e.g. G.655 fibre. In addition, PCVD shows its unique advantages in producing specialty fibres.
PCVD process: as the substrate tube of PCVD deposition, a clean quartz tube is fixed between the vacuum pump and MFC. The device can control SiCl4, GeCl4, C2F6 and O2 to mix fully and accurately according to the rations set in advance and they are poured into the substrate tube under the given low pressure.
The resonator which moves back and forth encircles the part of the substrate tube, and couples thousands of watts of microwave energy to the vapor mixtures through the waveguide. The microwave can produce plasma of a partial non isotherm and low pressure inside the quartz tube. The vapor inside the plasma reacts with each other and. At this moment, the electron motion of the plasma equates to the high temperature of 60,000 degree centigrade, far higher than the surrounding temperature of the tempering furnace.
SiCl4 and O2 can produce pure SiO2 after they react with each other. GeCl4 and O2 can produce the dopant GeO2 increasing the refractive index after they make similar reactions. Meanwhile, the products react from Freon, the main ingredients of C2F6, reduce the refractive index. Through this way, the optical fibre refractive index can be flexibly changed and deposition can be conducted directly on the transparent tube wall without any dusts coming into being.
When the resonator goes back and forth every time, the mixture proportion of the vapors can be changed to the thousands of deposition layers so that the most accurate perform core layer and refractive index profile curve can be gained. Since any designed refractive index profile can be produced on PCVD deposition lathes, the PCVD deposition lathe can be commonly used and suitable for any types of performs, regardless of single mode or multi mode fibres.
The deposition efficiency of PCVD process is very high and the deposition rate of Freon and SiO2 can reach almost 100%. Therefore, the raw materials can be efficiently used.
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