This thesis researches in the structure and fabrication of lensed fibers. To begin with, a novel method for automating fiber endface polishing to form quadrangular-pyramid-shaped fiber endface (QPSFE)-like shape is presented. This system successfully supported automatic polishing with an encouraged fiber tip offset. Such an automatic polishing system can also be applied to any other type of fiber endface. Next, an advanced polishing method to form an elliptical microlens endface from a QPSFE-like shape fiber is proposed. There are many advantages of this approach. First, the process to remove the tip of the fiber can be omitted and be replaced by the proposed process. This would raise the yield of the manufacturing of the lensed fiber and reducing manufacturing time and eliminating the possibility of human error. Second, after the process of the proposed method, an elliptic microlens is formed on the end of fiber and the fusing step can be skipped. In addition, in optical module packaging, laser welding used to attach components is expected to cause relative motion between the pre-aligned components. Such shifts might considerably reduce the efficiency of light coupling. This thesis provides a particular method to measurement the fiber shifts along the three axes quickly and precisely. Furthermore, the efficient coupling of plastic optical fibers (POFs) to the light source has become critical. Two kinds of new schemes of lensed optical fiber for POFs are proposed. The first type of lensed plastic optical fiber (LPOF) scheme is fabricating a convexo-concave-shaped fiber endface (CCSFE) by joining a flat-end POF and a convexo-concave plastic lens (CCPL). The second type of LPOF scheme is fabricating a hyperbola shape LPOF by using electrical force. Both designs of the LPOF all have advantages of easy fabrication and automatic manufacture.

Applying laser near-field wavefront reconstruction, we have discussed the coupling mechanism of the laser and optical lensed fiber. The coupling of the laser and optical lensed fiber is in the near-field range. In order to discuss the coupling mechanism of the laser and optical lensed fiber, we had to measure laser beam in near-field(including intensity and phase).The laser near-field intensity could be measured directly with an objective and a CCD camera. Because the laser spot size was too small, it was difficult to measure the laser near-field phase directly. Therefore, we used the phase retrieval algorithms, intercepting two groups of laser near-field intensity distribution plane to calculate laser near-field phase distribution. Combining laser near-field intensity distribution and phase distribution, we could rebuild laser beam in near-field. Lensed fiber is fabricated by means of grinding and fusing. We measured the coupling efficiency of the lensed fiber and laser diode(the wavelength of laser beam is 980nm), and simulated the surface of the lensed fiber with software. Applying beam propagation method, we could calculate the laser near-field distribution which propagated through lensed fiber, and cooperate the coupling efficiency of the lensed fiber and laser diode to explain the coupling mechanism. In summary, we discovered that the lensed fiber in the course of the coupling mechanism of the laser and optical lensed fiber changed the laser near-field phase from a bending curved surface into a flat curved surface just like the phase of plane wave, and it also improved the coupling efficiency.

The goal of this study is to design a new method which can be used for manufacturing the elliptic lensed fiber. The lensed fiber is obtained by heating the fiber tip in a fusing splicer at present. Before taking the fiber into fusing splicer, there are many procedures have to be checked. Those procedures will take a lot of time and increase the rate of inaccuracy. So, this research proposes a new method to form the elliptic lensed fiber by polishing. In this study, we simply use couple charge device (CCD) to detect the shape of the fiber tip. Than, we use the detected program to get the curvature of fiber tip. The system had been successfully achieved the purpose of curvature-controlled. The research will be the key technique toward the automatic bare fiber polishing system.

A simulation scheme is proposed to analyze the effects of elliptic-conical lensed fiber parameters on the coupling efficiency between a 980nm laser diode and single-mode fiber(SMF). The variation of fiber tip shapes with different melting zone volumes was investigated in this thesis. The heat-transfer finite element model in MARC package is employed to simulate the temperature distribution during the melting process. The free convection is considered in predicting the melting zone. Due to the surface tension, a round tip may be solidificated. In this study an elliptical tip lens is expected to improve the coupling efficiency. The microlens shapes with different radius of curvature is simulated with the software of Surface Evolver. The coupling efficiency of 980nm laser source and different elliptic-conical lensed fiber is calculated by utilizing the ZEMAX optical analysis software. The Taguchi method is employed to evaluate the effect of tip shape parameters on the coupling efficiency. The optimal elliptic-conical lensed fiber parameters has also been proposed. The efficiency loss introduced from the misalignments in laser module packaging has also been discussed in this study.

A simulation algorithm is proposed in this thesis to investigate the effects of lensed fiber parameters on the variation of radius of curvature of the melted lens and the coupling efficiency of butterfly type laser diode transiver module. Two different endface shapes, i.e. the taper and the conical-wedge type lensed fibers, will be studied. The effect of endface shapes, sizes, and the melting zone volume on the coupling efficiency of lensed fibers are simulated and discussed. In the study on the conical type lensed fiber, the MARC¡¦s elastic-plastic-thermal finite element model is employed to simulate the melting and the solidification processes at the fiber tip endface with different conical angles. The temperature dependent material properties are used to calculate the melting zone and the post-melten deformation during the heating process. The Surface Evolver Software has also been employed to simulate the solidified lens shapes. The variation of radius of curvature of the tip lens is analyzed. The ZEMAX optical analysis software is applied to explore the relation between the coupling efficiency and the distribution of the radius of curvature. The variation of laser signal coupling efficiency introduced from different conical lensed fibers is simulated numerically. A good agreement between the published measured data and the simulated results indicate the proposed simulation model is feasible. The effect of endface shape and molten zone size on the conical wedge type lensed fiber has been studied in a similar way. The coherence between the shape of solidified elliptical lens at fiber tip and the coupling efficiency for the 980nm LD will be explored. Different endface shapes will also be investigated by using the simulation model proposed previously. Different aspect ratio of the conical-wedge type tip will be introduced to compensate the elliptical LD ray model and to recover the coupling efficiency loss. The agreement between the results simulated using the proposed model and the measured data is examined. The simulated results indicate that the coupling efficiency of a butterfly type laser diode transever can be improved significantly by controlling the shape of the lens introduced in this type lensed fiber. The optimal grinding parameters and the melting parameters used to fabricate the lensed fibers will also be studied. The effects of the shape parameters, i.e. the conical taper angle, the wedge angle and the size of molten zones on the curvature variation of the lens will also be studied. A better understanding about the design and fabrication of the lensed fiber of a laser diode based transever module is expected from the results presented in this thesis.

This paper proposed a low-cost and high-throughput method to fabricate lensed optical fibers. SU-8 Photoresist is used as the material for fabricating the proposed lens structure and is directly applied on two kinds of optical fiber tip, single mode glass fibers (O.D.=125 £gm) and plastic graded-index plastic fiber (O.D.=500 £gm), utilizing surface tension force to form a hemi-circular shape lens structure. The hemi-circular shape SU-8 lens is then electrostatically pulled to form non-spherical shape in an uniform electric field at a temperature higher than the glass temperature (Tg) of SU-8. Microlens with various radius of curvature can be easily produced by tuning the applied electric fields during the electrostatic pulling process. In addition, this study also measures the UV-Vis-NIR spectrum SU-8 photoresist to confirm the optical property of SU-8. Results indicate the SU-8 has high optical transmittance from the wavelength range of 380-1600 nm. SEM observation also indicates the fabricated SU-8 microlens has excellent surface smoothness which is essential for optical applications. A commercial optical simulation software of ZEMAX® is used to predict the light path of the fabricated lensed fiber. The numerical results show good agreement with the experimental test obtained by projecting laser light into a diluted fluorescence solution. Furthermore, a Fabry-Perot laser chip with the wavelength of 1310 nm is used for light coupling test for the fabricated lensed fibers. Results show the coupling efficiency is up to 78% at working distance of 90 £gm while using the plastic lensed fiber (R =48 £gm), which is around 2 fold higher than that of a flat-end fiber. The coupling efficiency of glass lensed fiber (R =23 £gm) is up to 72% at working distance of 24 £gm, which is around 2.3 fold higher than that of a flat-end fiber. The proposed method is feasible of producing high-quality lensed optical fiber in a high throughput and low-cost way. The method proposed in the current study may give substantial impacts on fabricating lensed fiber in the future.

Optical transceiver module plays an important role in the optical communication system. The packaging quality of the module decides the ability of the communication. Since the light signal is transferred from a laser diode to an optical fiber, the light transfer efficiency between these two components becomes a very important work to be done. The micrometer dimension and the ultra-high performance requirement of these components lead to many problems in module packaging process. Among all the problems, the packaging of the fiber components is the most complicated. In this research, many key technologies are proposed to solve or improve the problems in the packaging of the fiber components. Thus, the performance of the module can be ensured. Two main topics of the fiber component packaging will be introduced here, the fiber-solder-ferrule (FSF) packaging and the machining of the fiber. In the packaging of the FSF, a positioning and a soldering technology are proposed to improve the packaging yield. For the positioning, a novel control strategy is constructed to shorten the positioning time and improve the positioning accuracy. Thus, the position of the fiber can be positioned at the center of the ferrule fast and precisely. The controller successfully completes the positioning command in 0.25sec with 1µm accuracy. And finally, the coupling efficiency can be hold. For the soldering of the FSF, an active soldering mechanism is developed to replace the passive manual operation. The mechanism successfully proofs the stability of the soldering and raises the yield from the 25% to 83%. In machining of the fiber, a fiber end polishing issue and a fiber inspection topic are addressed. For the fiber end polishing, an online force sensing mechanism is implemented. The force sensing mechanism can control the polished fiber tip offset within 1.5µm. So the fiber coupling efficiency can be maintained. A control strategy is designed to solve the polishing problems and reach the polishing requirement. At last, an interference-based fiber inspection method is proposed to find the splicing plane between two spliced fibers. The accuracy of the fiber cleaving in a cascaded fiber fabrication improves from 10µm to 1µm by observing the fiber splicing plane precisely. All the improvements of the above packaging technologies are proposed to raise or keep the performance of the transceiver module. So, the error between theories and experiments can be minimized. Meanwhile, a high stability and repeatability of the packaging can be achieved due to the automation of the positioning, force sensing, and inspection.

A novel lensed plastic optical fiber (LPOF) scheme to achieve the high coupling efficiency with a long working distance between the light source and LPOF is proposed. The advantages of the proposed LPOF are demonstrated by proofs of the experiment. In this study, an aspheric convex-concave plastic lens (CCPLs) is bonded with a flattened end of the plastic fiber by using the laser transmission welding (LTW) to form an aspheric-endface fiber. The working distance between the light source and LPOF can be increased with high coupling efficiency by the design of the CCPLs. According to the proposed design in this study, the working distance and the coupling efficiency can reach to 300£gm and 80%, separately. Furthermore, the analysis shows that the LTW can achieve a high welding strength and a small heat affected zone that meets the commercial utilization. But the LTW technology has some restrictions, the disadvantages of the LTW technology are improved in this study to spread the application of the laser welding.