Nippon Telegraph and Telephone Corporation

Nippon Telegraph and Telephone Public Corporation

Japan Science and Technology Corporation

Michiya Fujiki

Kazuo Fujiura

Terutoshi Kanamori

Yasutake Ohishi

Shiro Takahashi

Hiroshi Nakashima

Masao Morita

Toshikuni Kaino

Shigeo Nara

Shigeru Oikawa

Julian R Koe

Hiromi Tamoto

Novel polythiophenes which exhibit strong main chain absorption in the ultraviolet to visible region, show optical activity depending on the polymeric chain alone, and comprise as repeating units thiophene rings containing chiral substituent groups, and are represented by the following general formula:(wherein Rand Rare the same or different, each representing a hydrogen atom or an organic group, of which at least one is an enantiopure alkyl group with a branch structure at the &#x3b2;-position, and n represents the number of repeating units selected from 10 to 100,000).

Optically active polythiophenes

A method for preparing a homogenous fluoride glass containing high purity BaF.sub.2 through the CVD process using a gaseous mixture containing a barium .beta.-diketonate complex service as a first starting material and represented by the following general formula (1) of: ##STR1## where (i) R and R' are each --C(CH.sub.3).sub.3 ; or (ii) R is CH.sub.2 CH.sub.2 CH.sub.3 and R' is --C(CH.sub.3).sub.3 ; or (iii) R and R' are each CF.sub.3 ; a gaseous or vaporizable compound of the metallic element constituting said fluoride glass, the gaseous or vaporizable compound serving as a second starting material; and a fluorine-containing gas serving as fluorinating agent. Further provided is a process for preparing a perform for a fluoride optical fiber which is low in transmission loss, by depositing the fluoride glass over the interior wall of a cylindrical tube or the wall of rod-like glass substrate through the CVD process following by collapsing.

Method of making fluoride glass using barium .beta.-diketones

Provided is a process for preparing a homogeneous fluoride glass containing high purity BaF.sub.2 through the CVD process characterized in that the used gaseous mixture comprising: a barium .beta.-diketonate complex serving as a first starting material and represented by the following general formula (1) of: ##STR1## wherein R is an alkyl group having 1 to 7 carbon atoms, R' is a substituted alkyl group having fluorine atoms substituting hydrogen atoms and represented by C.sub.n F.sub.2n+1 where n is an integer of from 1 to 3; a gaseous or vaporizable compound of the metallic element constituting said fluoride glass, the gaseous or vaporizable compound serving as a second starting material; and a fluorine-containing gas serving as fluorinating agent. Further provided is a process for preparing a preform for a fluoride optical fiber which is low in transmission loss, by depositing the fluoride glass over the interior wall of a cylindrical tube or the wall of rod-like glass substrate through the CVD process followed by collapsing.

Process for the preparation of fluoride glass and process for the

In a sealed system, a polymerization initiator and a chain transfer agent are added to a methyl methacrylate monomer distilled under reduced pressure condition via a distillation step of the former both ingredients, the methyl methacrylate monomer is successively polymerized to prepare a core polymer while maintaining the reduced pressure condition, then the resulting core polymer is subjected to melt spinning to form a core fiber while maintaining the sealed system, and a clad of a macromolecular compound having a refractive index lower than that of the aforesaid core fiber is adhered around the periphery thereof, whereby a low-loss plastic optical fiber with excellent optical transmission characteristics having a core-cladding structure is fabricated. Plastic optical fibers so made exhibit light attenuation as low as 60 dB/km or lower.

Fabrication of a low-loss plastic optical fiber

Growing community of inventors

Mito, Japan

Michiya Fujiki