Focusing condition such as numerical aperture (N.A.) has a great influence on the creation of molten area and the stable welding process in fusion micro-welding of glass. In this study, a picosecond pulsed laser of 1064 nm in wavelength and 12.5 ps in pulse duration was tightly focused inside a borosilicate glass using objective lenses of numerical apertures 0.45, 0.65, and 0.85 with spherical aberration correction. Influence of numerical aperture on molten area formation was experimentally investigated through analysis of focusing situation in glass, and movement of absorption point, and then molten area characteristics were discussed. It is concluded that N.A. of 0.65 with superior focusing characteristics can form a large and continuous molten area without cracks, which enables achievement of stable joining of glass material by picosecond pulsed laser.

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A lightpath design and management tool with parallel processing capabilities and a flexible upgradability, allowing new functions to be added to the system without any system program changes, has been designed and implemented for IP-over-CWDM networks with ROADMs. The tool can process applications composed of some sub applications in parallel in multi machines for high-speed performance. In addition, the tool was designed to have a flexible upgradability, i.e. no changes of the system programs are required when adding the new functions. The system functions are to design lightpaths and wavelengths allocated to ROADMs for the lightpaths required to groom given traffic. The tool also can search possible lightpath routes made by ROADMs with specified switch states, and output the total optical losses of the routes. By the tool implemented in one management and 3 calculation machines for the parallel processing, the total time to obtain the results for a 5-node IP-over-CWDM network was reduced down to 65 % of the total time by the tool with a single machine without parallel processing. The tool enables the network administrators to design and manage the lightpath reconfigurations effectively without errors by avoiding making unlinked lightpaths through routes with higher losses to connect nodes, before the reconfiguration.Index Terms-IP-over-CWDM network, lightpath design, management tool, parallel processing, upgradability I. INTRODUCTIONPTICAL networks are introduced widely to satisfy the increasing traffic demands for the Internet. Optical networks are also expected to provide effective broadband services in optical LAN (Local Area Network) for business use, campus networks, factory networks, and regional networks connecting local governments and research organizations etc., by satisfying different application requirements. The CWDM (Coarse Wavelength-Division Multiplexing) technologies are effective for such applications, because no wavelength stability control is necessary, and therefore the devices are low cost. The communication services are provided by connecting nodes with lightwaves and one optical connection with a wavelength is called a lightpath. Such networks have to be operated and maintained by the network administrators. The important tasks by the administrators are lightpath configurations in the initial network construction and reconfigurations [1, 2] during providing services in the network to avoid traffic congestions, depending on the demand changes. For the reconfiguration purpose, ROADMs [1] (Reconfigurable Optical Add/Drop Multiplexers) were proposed and investigated.We have developed a stackable ROADM (S-ROADM) for IP-over-CWDM networks [3]. The S-ROADM can be constructed by connecting modules with add/drop and passing-through functions for one wavelength, respectively, The modules enable the ROADM to have wavelength transparency flexibly in a stackable way, as described in the next section. The lightpath reconfiguration performance by the S-ROADMs was evaluated experimentally in a bi-direct...