Tae-Goo Choy

Characterization of borophosphosilicate glass soot fabricated by flame hydrolysis deposition for silica-on-silicon device applications

The use of flame hydrolysis deposition (FHD) to fabricate porous silica glass soot in the B2O3-P2O5-SiO2 glass system (BPSG) is described for silica-on-silicon device applications. The deposition conditions with a Si substrate temperature (∼200 °C) and a flame temperature (1300–1500 °C) are appropriate to synthesize the SiO2 and P2O5-SiO2 non-crystalline glass soot. However, further investigations for the B2O3-P2O5-SiO2 glass soot are needed to obtain complete amorphous phases. The densification process of porous silica glass soot in the three systems of SiO2, P2O5-SiO2 and B2O3-P2O5-SiO2 is also described to estimate the onset of sintering temperature. The OH absorption measurements are performed to try to identify incorporation of hydroxyl contaminants in the systems of P2O5-SiO2 and B2O3-P2O5-SiO2.

A simple structure of low-loss large-angle abrupt-bend waveguide

A simple structure of low-loss large-angle abrupt-bend waveguide is proposed. The normalized transmitted powers of the proposed structure are as large as 0.99 and 0.92 for bend angles of 5/spl deg/ and 7/spl deg/, respectively. Experimental results of silica-based planar lightwave circuit-type 5/spl deg/-angled bends agree well with beam propagation method simulations.

Nonparametric estimation of reliability function using the kernel density estimation method

Analysis of data from an accelerated life test employs a model. Such a statistical model for an accelerated life test consists of a life distribution that represents the scatter in product life and a relationship between life and stress. In this study, the Coffin-Manson relationship is used to model fatigue failure of metals subject to thermal cycling. Generally there are two statistical methods for estimating reliability of objects (life distribution). One is a parametric approach and the other is a nonparametric one. The parametric method assumes that the underlying distribution function belongs to a fixed distribution family indexed by a finite number of parameters. The unknown parameters are then estimated from the data. On the other hand, the nonparametric method does not specify a particular family of distributions. The major difficulty of the parametric approach arises at the stage of model specification. Correct specification of the underlying model is crucial for successful application of the parametric approach. Incorrect specification yields severe model bias and this cannot be compensated in any degree by accurate parameter estimation. In this paper, we provide a nonparametric method to estimate the life distribution under normal usage from accelerated life test data.<<ETX>>

A study on insertion-loss improvement for optical connector using the analysis of transmitted optical intensity

In the butt-joint coupling using cylindrical ferrules and sleeve, the insertion loss of the single-mode optical connector depends on the accuracies of components (i.e., sleeve, ferrule, fiber etc.). And it is difficult to achieve both cost reduction and performance improvement simultaneously in optical connectors because higher accuracies give better performance but cause higher cost. For single-mode fiber connection, the dimensional accuracies of currently available ferrules and optical fibers are not sufficiently high to ensure a low insertion loss with reasonable cost. And many efforts have been made to have low insertion loss without any higher order of accuracies of components. In one of the proposed methods the technique of stepwise orientation of ferrule is used to reduce the transverse offset between butt-joint fiber cores by achieving Minimizing Loss Region (MLR). This method requires several stepwise rotations to make the fiber core be within the MLR that was determined by optimal trade-off between insertion loss and working time. In this method the insertion loss depends on the size of the pre-determined MLR. In the report a new assembling method through which a very small MLR can be achieved in a short time is proposed.<<ETX>>

A study on insertion loss improvement for an optical connector using the analysis of transmitted optical intensity

In one of the proposed methods for single-mode fiber connection the technique for stepwise orientation of the ferrule is used to reduce the transverse offset between butt-joint fiber cores by achieving the minimizing loss region (MLR). This method requires several stepwise rotations to make the fiber core within the MLR, which is determined by the optimal tradeoff between insertion loss and working time. In this method the insertion loss severely depends on the size of the predetermined MLR. A new assembly method through which a very small MLR can be achieved in a short time is proposed. With this method, performance can be in proved by minimizing misalignment offset of components without any requirement of strict tolerances. The eccentricity between the cladding and the core, which is classified as an intrinsic misalgnment factor, can be overcome. The rotating ferrule adjustment method, by using an adaptive control algorithm, makes the optimal peak intensity point fall into the very narrow MLR with just one try. Lower coupling loss can be achieved by aligning the peak intensity point in a very narrow region of the sleeve. An automated termination process can be setup, using a computer that performs both the power intensity distribution image process and orientation adjustment. >