Abstract: According to an embodiment, there is provided an optical transmission element comprising: a fiber including a core made of a first glass and a cladding made of a second glass and covering an outer periphery of the core; and a covering layer covering an outer periphery of the cladding and including a plurality of nonionic surfactant molecules wherein each of the nonionic surfactant molecules is hydrogen-bonded to the cladding.

Abstract: An optical transmission element according to an embodiment comprises a fiber and a covering layer. The fiber includes a core made of glass and a cladding made of glass covering an outer periphery of the core. The covering layer covers an outer periphery of the cladding and includes a plurality of alkyl groups which are not fluorine-substituted wherein each of the alkyl groups is bonded to the cladding via a siloxane bond and wherein the alkyl groups are represented by CH3(CH2)n— wherein m is an integer of 7 or more.

Abstract: According to an embodiment, there is provided an optical transmission element comprising: a fiber including a core made of a first glass and a cladding made of a second glass and covering an outer periphery of the core; and a covering layer covering an outer periphery of the cladding and including a plurality of nonionic surfactant molecules wherein each of the nonionic surfactant molecules is hydrogen-bonded to the cladding.

Abstract: An optical transmission element according to an embodiment comprises a fiber and a covering layer. The fiber includes a core made of glass and a cladding made of glass covering an outer periphery of the core. The covering layer covers an outer periphery of the cladding and includes a plurality of alkyl groups which are not fluorine-substituted wherein each of the alkyl groups is bonded to the cladding via a siloxane bond and wherein the alkyl groups are represented by CH3(CH2)n— wherein m is an integer of 7 or more.

Abstract: An endoscope includes an insertion portion including an image pickup section, an illumination section, and a light guide inserted inside the insertion portion, the light guide including a plurality of fibers made of a glass not containing lead, the plurality of fibers guiding illuminating light from a light source apparatus to the illumination section, the light guide having a numerical aperture of 0.46 to 0.90. A core glass of a fiber have a refractive index nd of 1.56 to 1.74, and a composition of (A) 20 to 55 wt % SiO2, (B1) 0 to 4.0 wt % B2O3, (B2) neither P2O5 nor GeO2 contained, (C) 25 to 72 wt % (BaO+SrO+La2O3+Lu2O3+Ta2O5+Gd2O3+WO3), (D) 0 to 30 wt % ZnO, (E) no Al2O3 contained, (F) no ZrO2 contained, (G) neither PbO nor As2O3 contained, (H) 0 to 15 wt % (Na2O+K2O), (I) 0 to 0.050 wt % Sb2O3 and (J) 0.26 to 1.63 wt % (Na2SO4+K2SO4).

Abstract: An endoscope includes an insertion portion including an image pickup section, an illumination section, and a light guide inserted inside the insertion portion, the light guide including a plurality of fibers made of a glass not containing lead, the plurality of fibers guiding illuminating light from a light source apparatus to the illumination section, the light guide having a numerical aperture of 0.46 to 0.90. A core glass of a fiber have a refractive index nd of 1.56 to 1.74, and a composition of (A) 20 to 55 wt % SiO2, (B1) 0 to 4.0 wt % B2O3, (B2) neither P2O5 nor GeO2 contained, (C) 25 to 72 wt % (BaO+SrO+La2O3+Lu2O3+Ta2O5+Gd2O3+WO3), (D) 0 to 30 wt % ZnO, (E) no Al2O3 contained, (F) no ZrO2 contained, (G) neither PbO nor As2O3 contained, (H) 0 to 15 wt % (Na2O+K2O), (I) 0 to 0.050 wt % Sb2O3 and (J) 0.26 to 1.63 wt % (Na2SO4+K2SO4).