MCVD工艺关键技术,蒋作文,光纤的四大制造技术,VAD（轴向汽相沉积） OVD （外部汽相沉积） MCVD（改进的化学汽相沉积） PCVD（等离子体化学汽相沉积）,MCVD工艺简介,MCVD工艺步骤1Recipe Development,Main variables for each process steps are following: Gas flows: bubbler carrier gas, O2, He, Cl2, SF6 etc. Preform temperature Carriage speed Sootbox pressure Ramping of relevant parameters,MCVD工艺步骤2Tube preparation,Typical MCVD production tube is constructed from three quartz tubes, which are welded together prior to MCVD process. inlet tube: low quality quartz substrate tube: high quality synthetic silica, forms final preform exhaust tube: low quality quartz sleeving tube: synthetic silica,MCVD工艺步骤3Fire Polishing/Etching,Purpose: To clean tube outer and inner surface to improve preform quality. Temperature: 1850-2200C Reactant flows: O2 + fluorine source for etching,MCVD工艺步骤4Cladding and core deposition,Cladding deposition Purpose: deposition of protection barrier for core. Temperature: 1900-2100oC Typical reactant flows: SiCl4, POCl3, O2, He Core deposition Purpose: deposition of refractive index difference Temperature: 1900-2200oC Typical reactant flows: SiCl4, GeCl4, O2, He,MCVD工艺反应机理,SiCl4+O2=SiO2+2Cl2 GeCl4+O2=GeO2+2Cl2 4POCl3+3O2=2P2O5+6Cl2 4BCl3+3O2=2B2O3+6Cl2,热泳效应,热泳现象是指在温度梯度不为零的气体或悬浮体中，粒子向较冷区域运动的现象。热泳速度正比于温度梯度，而与粒径无关。,MCVD工艺步骤5Collapsing,Purpose: to produce glass rod for jacketing and fiber drawing Typically 2 to 5 forward and 1 backward steps Temperature: 2000-2400oC Chlorine used as a drying agent,MCVD工艺步骤5 Preform analysis,dimensional and optical parameter evaluation. important process and quality control tool,More preform analysis,Preform dimensions Preform, cladding and core diameters from different angles and longitudinal positions Refractive indices Substrate tube, cladding and core from different longitudinal positions Cutoff, MFD, Chromatic dispersion Preform non-circularity (preform, cladding, core) Preform concentricity (preform, cladding, core),MCVD工艺步骤6 Rod in tube sleeving,Purpose: enlarge preform size to improve MCVD productivity Typical final preform size: 40 to 80 mm Temperature: 2000C Vacuum suction between rod and tube to accelerate joining process,Fiber drawing,MCVD设备系统主要组成,1.Lathe 2. Gas Control System 3. PC/PLC Control System 4. Gas & Water Supply 5. Extract Systems.,SGC MCVD,MCVD Lathe,Oxy-hydrogen burner Pyrometer Flame detector,Gas Control and supply System,Silicon Tetrachloride (SiCl4) Supply Germanium Tetrachloride (GeCl4) Supply Phosphoryl Chloride (POCl3) Supply Boron trichloride (BCl3) Supply,Lathe Hydrogen&Oxygen Supply Sulphur Hexafluoride (SF6) Supply Chlorine Supply Oxygen Supply Helium Supply Nitrogen Supply Pneumatics Supply Drybox temperature control,Gas Station,Extract Systems,1. Gas inlet 2. Jet stream column 3. Reduction tank 4. Neutralization tank 5. Absorption column 6. Fresh water feed 7. Chemical feed 8. Waste water discharge 9. Pure gas outlet,Gas scrubberJet stream tank,Over 90% of silica is collected to the 350l jet stream tank. NaOH and Na2S2O3 solutions are automatically added to the tank to keep the pH in the tank between 8 and 8.5 and Redox potential between -50 and +200mV. The washed gas is directed to Neutralization tank through a mist eliminator. Jet stream tank receives continuous 15-40 l/h overflow from Neutralization tank.,Gas scrubber Neutralization tank,The washed gas from stage 1 is directed to the stage 2 through a set of dampers and mist eliminator (chevron type). pH of stage 2 tank is kept between 10 and 11 to ensure efficient neutralization of the HCl gas. HCl + NaOH NaCl + H2O Cl2 + 2NaOH NaCl + NaClO + H2O,谢谢！,