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日立制作所已申请到了制造低损耗光纤技术的专利,专利号为特许1133631。在制造传输损耗低的光纤时,必须防上引起光吸收的重金属离子和氢氧根离子等不纯物混入光纤纤芯部分。其中,尤其要防止不纯物从保护玻璃管扩散到纤芯中去,为此,以往均在保护玻璃管和包层之间设置一层防不纯物扩散的纯SiO_2层,或者在保护玻璃管和纤芯之间设置一厚包层并
Hitachi has applied for the manufacture of low-loss optical fiber technology patents, patent No. 1133631. When manufacturing an optical fiber with a low transmission loss, it is necessary to prevent impurities such as heavy metal ions and hydroxyl ions that cause light absorption from entering the core portion of the optical fiber. Among them, in particular, to prevent the diffusion of impurities from the protective glass tube to the core, to this end, in the past are provided between the protective glass tube and the cladding layer of pure SiO 2 diffusion of impurities to prevent or in the protective glass Set a thick cladding between the tube and the core