Abstract: An optical fiber includes a core (1a) having an oblong rectangular or square cross section and made of quartz, a cladding (2) surrounding the core (1a), having a circular outer cross-sectional shape, having a lower refractive index than the core (1a), and made of resin, and a support layer (3) surrounding the cladding (2) and made of quartz.

Abstract: An optical connector structure (C) includes: an optical fiber (100) having a laser beam entrance end to which a quartz chip (120) is integrally connected; a ferrule (200) into which a portion of the optical fiber (100) including the quartz chip (120) is inserted and which holds the portion of the optical fiber; and a receptacle (21) surrounding the ferrule (200), and including a large-diameter hole (21b) formed toward an opening and a small-diameter hole formed toward a back of the receptacle so as to be connected to the large-diameter hole. A front end portion (210) of the ferrule (200) is inserted into the small-diameter hole (21a) of the receptacle (21), and a back body portion (211) of the ferrule (200) is inserted into the large-diameter hole (21b) of the receptacle (21).

Abstract: An optical fiber includes a core (1a) having an oblong rectangular or square cross section and made of quartz, and a cladding (2) surrounding the core (1a), having a circular outer cross-sectional shape, and made of resin.

Abstract: An optical fiber includes a core (1a) having an oblong rectangular or square cross section and made of quartz, a cladding (2) surrounding the core (1a), having a circular outer cross-sectional shape, having a lower refractive index than the core (1a), and made of resin, and a support layer (3) surrounding the cladding (2) and made of quartz.

Abstract: An optical connector structure (C) includes: an optical fiber (100) having a laser beam entrance end to which a quartz chip (120) is integrally connected; a ferrule (200) into which a portion of the optical fiber (100) including the quartz chip (120) is inserted and which holds the portion of the optical fiber; and a receptacle (21) surrounding the ferrule (200), and including a large-diameter hole (21b) formed toward an opening and a small-diameter hole formed toward a back of the receptacle so as to be connected to the large-diameter hole. A front end portion (210) of the ferrule (200) is inserted into the small-diameter hole (21a) of the receptacle (21), and a back body portion (211) of the ferrule (200) is inserted into the large-diameter hole (21b) of the receptacle (21).

Abstract: An optical fiber includes a core (1a) having an oblong rectangular or square cross section and made of quartz, and a cladding (2) surrounding the core (1a), having a circular outer cross-sectional shape, and made of resin.

Abstract: A core 2 is co-doped with Ge in a general concentration equivalent to that in a core of an optical fiber to be connected as well as Sn and Al in predetermined concentrations. A glass part F including the core and a cladding 3 is coated with a primary coat layer 4 of a UV transmitting resin which transmits UV of 240 nm through 270 nm but cures by absorbing UV of a shorter wavelength band than 240 nm or a longer wavelength band than 270 nm. A grating is written in the core by irradiating the core with UV through the primary coat layer. The primary coat layer is covered with a secondary coat layer 7 of a resin having a negative coefficient of linear expansion so as to cancel and suppress expansion/shrinkage of the glass part in accordance with temperature change derived from the positive coefficient of linear expansion.

Abstract: A long period grating (8) by which an excitation light propagated through the 2nd core (4) of a double-core type optical fiber composed of the 2nd core (4) formed on the outer circumference of the 1st core (2) is guided into the 1st core (2) is formed on the 1st core (2) to improve an excitation efficiency.