The possibility of using SF6 and CF4 as fluorine sources have been studied utilizing the modified chemical vapor deposition (MCVD) method. It has been found that the refractive index change of fluorine doped silica glasses strongly depends on the source materials and the deposition temperature. A maximum refractive index change of 0.05 has been observed using SF6 as the fluorine source. No excess absorption loss resulting from the use of SF6 in the long wavelength region has been observed in single-mode fibers with fluorine and P2O5 doped silica glass cladding.

A new switched-capacitor (SC) pipelined analog-to-digital (A/D) converter is proposed which appears to have some speed, accuracy, and area advantages over earlier schemes. Its analog components consist of only sample-and-hold circuits and comparators. It also has a differential-type configuration and requires only a two-phase clock. An analysis based on a few assumption about characteristics of op-amps shows that the proposed circuit can achieve 13-bit conversion accuracy at a sampling rate of 8.5 Msamples/s. When an 8-bit pipelined A/D converter built with discrete components was operated statically at clock frequency 100 kHz, the maximum total conversion error including a quantizing error was about 0.7 LSB.

New cyclic switched-capacitor (SC) D/A and A/D converters are proposed. In the former, a capacitor-mismatch-compensation technique using additional small capacitors is introduced. With this, a capacitor ratio accuracy as high as twelve bits is possible. And, in the latter, the A/D conversion with ten-bit accuracy is realizable by the simple ratio-independent circuit consuming only a few number of clock cycles for each bit conversion.