MCVDMCVD工艺制备光纤工艺制备光纤( (制造制造工艺工艺) ) 光纤的四大制造技术光纤的四大制造技术ØVAD（轴向汽相沉积）ØOVD （外部汽相沉积）ØMCVD（改进的化学汽相沉积）ØPCVD（等离子体化学汽相沉积） MCVDMCVD工艺简介工艺简介 MCVDMCVD工艺步骤工艺步骤1——Recipe Development1——Recipe Development Main variables for each process steps are following:ª Gas flows: bubbler carrier gas, O2, He, Cl2, SF6 etc.ª Preform temperatureª Carriage speedª Sootbox pressureª Ramping of relevant parameters MCVDMCVD工艺步骤工艺步骤2——Tube preparation2——Tube preparation Typical MCVD production tube is constructed from three quartz tubes,which are welded together prior to MCVD process.ª inlet tube: low quality quartzª substrate tube: high quality synthetic silica, forms final preformª exhaust tube: low quality quartzª sleeving tube: synthetic silica MCVDMCVD工艺步骤工艺步骤3——Fire Polishing/Etching3——Fire Polishing/Etching Purpose: To clean tube outer and inner surface to improve preform quality.ª Temperature: 1850-2200Cª Reactant flows: O2 + fluorine source for etchingSF6+O2 MCVDMCVDMCVDMCVD工艺步骤工艺步骤工艺步骤工艺步骤4——Cladding and core deposition4——Cladding and core deposition4——Cladding and core deposition4——Cladding and core depositionCladding depositionª Purpose: deposition of protection barrier for core.ª Temperature: 1900-2100oCª Typical reactant flows: SiCl4,ªPOCl3, O2, HeCore depositionª Purpose: deposition of refractiveªindex differenceª Temperature: 1900-2200oCª Typical reactant flows: SiCl4,ªGeCl4, O2, He MCVDMCVD工艺反应机理工艺反应机理SiCl4+O2=SiO2+2Cl2 GeCl4+O2=GeO2+2Cl24POCl3+3O2=2P2O5+6Cl2 4BCl3+3O2=2B2O3+6Cl2 热泳效应热泳效应热泳现象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 MCVDMCVD工艺步骤工艺步骤5——Collapsing5——Collapsingª Purpose: to produce glass rod for jacketing and fiber drawingª Typically 2 to 5 forward and 1 backward stepsª Temperature: 2000-2400oCª Chlorine used as a drying agent MCVDMCVD工艺步骤工艺步骤5——5—— Preform analysisPreform analysisª dimensional and optical parameter evaluation.ª important process and quality control tool More preform analysisMore preform analysisª Preform dimensions Preform, cladding and core diameters from different angles and longitudinal positionsª Refractive indices Substrate tube, cladding and core from different longitudinal positionsª Cutoff, MFD, Chromatic dispersionª Preform non-circularity (preform, cladding, core)ª Preform concentricity (preform, cladding, core) MCVDMCVD工艺步骤工艺步骤6——6—— Rod in tube Rod in tube sleevingsleevingª Purpose: enlarge preform size to improve MCVD productivityª Typical final preform size: 40 to 80 mmª Temperature: >2000Cª Vacuum suction between rod and tube to accelerate joining processFiber Fiber drawingdrawing MCVDMCVD设备系统主要组成设备系统主要组成1.Lathe 2. Gas Control System 3. PC/PLC Control System 4. Gas & Water Supply 5. Extract Systems. SGC MCVD SGC MCVD MCVD LatheMCVD LatheªOxy-hydrogen burnerªPyrometerªFlame detector Gas Control and supply SystemGas Control and supply SystemªSilicon Tetrachloride (SiCl4) SupplyªGermanium Tetrachloride (GeCl4) SupplyªPhosphoryl Chloride (POCl3) SupplyªBoron trichloride (BCl3) SupplyªLathe Hydrogen&Oxygen SupplyªSulphur Hexafluoride (SF6) SupplyªChlorine SupplyªOxygen SupplyªHelium SupplyªNitrogen SupplyªPneumatics SupplyªDrybox temperature control Gas StationGas Station Extract SystemsExtract Systems1. Gas inlet2. Jet stream column3. Reduction tank4. Neutralization tank5. Absorption column6. Fresh water feed7. Chemical feed8. Waste water discharge9. Pure gas outlet Gas scrubber——Jet stream tankGas scrubber——Jet stream tank Over 90% of silica is collected to the350l jet stream tank. NaOH and Na2S2O3 solutions areautomatically added to the tank tokeep the pH in the tank between 8 and8.5 and Redox potential between -50and +200mV. The washed gas is directed to Neutralization tankthrough a mist eliminator. Jet stream tank receives continuous15-40 l/h overflow from Neutralization tank. Gas scrubber——Gas scrubber—— Neutralization tankNeutralization tankªThe washed gas from stage 1 isªdirected to the stage 2 through a setof dampers and mist eliminator(chevron type).ª pH of stage 2 tank is kept between10 and 11 to ensure efficientªneutralization of the HCl gas.ª HCl + NaOH --> NaCl + H2Oª Cl2 + 2NaOH --> NaCl + NaClO + H2O 新型光纤材料与器件团队 NOVEL OPTIC FIBERS AND DEVICES TEAM谢谢！谢谢！谢谢！谢谢！ 结束结束 。