| Fused-taper fiber device is the most typical fiber device and also abasic part of other devices. Fused biconical taper (FBT) is the commonfabrication method of fiber coupler, wavelength division multiplex,optical filter and so on. View from the present research at home andabroad, the optical theory and design have been achieved a greatimprovement. But from the view of manufacturing science, themechanical behavior of rheological manufacturing process is studiedinsufficiently, especially the relationships between rheologicalmanufacturing technological parameters, and between microstructure ofdevice and optical performance. The FBT technology is still at empiricalstage. The performance of fiber device is not ideal, such as low efficiencyand yield rate, and high cost price. At present, our country's fabricationtechnique and fabricatation setup of fused taper fiber device are dependon importing.Fiber coupler is one of the most important devices among fused taperfiber devices. Its usage ranks second among the optical passive devices.It is used for separating or coupling light. At.present, it is fabricated withfused biconical taper technology at large. Its fabrication process is: twoparallel fibers are positioned very close to each other, heated by burningthe combustible gas, drawn at a certain speed by a micro-machine andformed a biconical taper. The fused region will become slim during theheating and drawing processes and become a biconical taper at last. Thetranmitting light signal is coupled and restributed in the fused taperregion. A part of light power is transmitted through "straight arm"; theother part is transmitted through "coupling arm".Taking the fiber coupler as represent, aiming at the performanceproblem of the fiber coupler which is used in the market, such as theoptical performance differences of accepted products, technologicaloptimization and stability reflected by the low rate of finished products,how to reduce excess loss, and so on. From the view of manufacture of rheological formation, the research of experiment and theory has beendeveloped. The effects of rheological technological parameters such asdrawing speed and fused temperature on the optical performance,microstructure and the process of rheological formation have beeninvestigated. It is discovered that the present heating mode of combustinggas can't satisfy with the rheological manufacturing technological needof high performance fiber devices. A new resistance heating system is putforward, designed and manufactured, and a new fused biconical tapermachine is developed.The main innovation researches in the paper are as followed:1. The changing rules between the different technological parameters(such as drawing speed and fused temperature) and the performance offiber coupler optical fiber coupler (such as light power loss and couplingratio) have been studied with the six-axes optical fiber coupler machine.2. The surface topography of fiber coupler fabricated at differenttechnological condition is tested by the scanning electron microscope(SEM). The effect of technological parameters on surface topography isstudied. The essential relationship between surface topography, andperformance of the fiber coupler is demonstrated.3. Based on molecular vibration theory and infrared spectrum theory,the mathematical model on 1100cm-1 wave number of infraredcharacteristic peak and the bonding angle of unit of Si—O—Si offiberglass is set up.4. It is discovered that the essential reason of different opticalperformance such as uneven refractive index distribution and differentcoupling ration is the change of molecular structural in the fabricationprocess with the micro infrared spectroscope.5. Aiming at the theological behavior and the viscoelastic relaxationcharacter of fiberglass in the transition region, a fitting method onrelaxation modulus facing the finite element analysis is put forward. Thetransition of parameters lain in expression of viscoelastic relaxation andfinite element analysis are solved. 6. The numerical analysis model of fiber coupler in the process offused biconical taper (FBT) is constructed successfully. The numericalanalysis of fiber coupler in the process of fused FBT is accomplishedwith finite element software. The effects of technology parameters suchas fused temperature and drawing speed on stress, strain and geometry inthe manufacturing process are acquired.7. It is found that the essential cause to hinder improve theperformance of the light transimit is that the outfield provided with thepresent setup can't satisfy with the exact performances. The uneven stressresults in the distortion ofmicrostructure and loss part of optical power.8. A model of temperature outfield and construction realization witheven temperature and minimize internal stress is built. A novel electrinicresistance heater and temperature controlling system are developed. Thefused temperature is improved from 5～30℃to 1.5℃, whose stability isimproved.9. Based on the novel resistance heater, a new fused biconical tapermachine with high quality is developed. The consistency of performanceis improved exponentially. The consistency of power loss is increased by5 folds. The consistency of coupling ratio is increased by 4 folds. Theconsistency of drawing length is increased by 20 folds.
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