Abstract: An optical fiber (10) includes: a core (11); a first cladding (12) surrounding the core (11) and having a lower refractive index than the core (11); and a second cladding (13) surrounding the first cladding (12) and having a lower refractive index than the first cladding (12). The first cladding (12) is doped with light attenuating dopant so that a concentration of the light attenuating dopant in the first cladding (12) increases from an inner surface of the first cladding (12) toward an outer surface of the first cladding (12).

Abstract: A graded index multimode optical fiber (10) includes: a core (11) having an outside diameter of 45-65 ?m; a first cladding (12) surrounding the core (11); a second cladding (13) surrounding the first cladding (12) and made of a material having a lower refractive index than the first cladding (12); and a third cladding (14) surrounding the second cladding (13) and made of a material having a higher refractive index than the second cladding (13). The ratio of the outside diameter of the first cladding (12) to the outside diameter of the core (11) is 1.15-1.25.

Abstract: An optical fiber includes: a core (1) having an outer diameter (D1) of greater than or equal to 8.2 ?m and less than or equal to 10.2 ?m; a first cladding (2) surrounding the core (1) and having an outer diameter (D2) of greater than or equal to 30 ?m and less than or equal to 45 ?m; a second cladding (3) surrounding the first cladding (2) and having a thickness (T) of greater than or equal to 7.4 ?m; and a support layer (4) surrounding the second cladding (3). The relative refractive index difference which is the ratio of the difference between the refractive index of the support layer (4) and that of the second cladding (3) to the refractive index of the support layer (4) is greater than or equal to 0.5%.

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 connection structure which reduces MPI in the use of an optical fiber with a bend resistance improved by forming holes in the fiber, and a single-mode fiber which reduces MPI are provided. A second cladding portion of a second single-mode fiber 20 includes holes 28, and thus, the second single-mode fiber 20 has low bending loss. A portion of the second single-mode fiber 20 connected to a first single-mode fiber 10a is made solid by filling corresponding portions of the holes 28 over the length L0, and light in a mode LP11 is significantly attenuated in this portion, thereby reducing MPI.

Abstract: An optical fiber (10) includes: a core (11); a first cladding (12) surrounding the core (11) and having a lower refractive index than the core (11); and a second cladding (13) surrounding the first cladding (12) and having a lower refractive index than the first cladding (12). The first cladding (12) is doped with light attenuating dopant so that a concentration of the light attenuating dopant in the first cladding (12) increases from an inner surface of the first cladding (12) toward an outer surface of the first cladding (12).

Abstract: An optical fiber connection structure which reduces MPI in the use of an optical fiber with a bend resistance improved by forming holes in the fiber, and a single-mode fiber which reduces MPI are provided. A second cladding portion of a second single-mode fiber 20 includes holes 28, and thus, the second single-mode fiber 20 has low bending loss. A portion of the second single-mode fiber 20 connected to a first single-mode fiber 10a is made solid by filling corresponding portions of the holes 28 over the length L0, and light in a mode LP11 is significantly attenuated in this portion, thereby reducing MPI.

Abstract: An optical fiber connection structure reducing MPI is provided. An intervening optical fiber 30 having a normalized frequency less than 2.405 and a length greater than or equal to 2 mm and less than or equal to 30 mm is interposed between a single-mode fiber 10a and a second single-mode fiber 20, and the second single-mode fiber 20 and the intervening optical fiber 30 are fused together. While transmission light is input through the first single-mode fiber 10a to the second single-mode fiber 20, a higher order mode is not generated in the second single-mode fiber 20.

Abstract: A graded index multimode optical fiber (10) includes: a core (11) having an outside diameter of 45-65 ?m; a first cladding (12) surrounding the core (11); a second cladding (13) surrounding the first cladding (12) and made of a material having a lower refractive index than the first cladding (12); and a third cladding (14) surrounding the second cladding (13) and made of a material having a higher refractive index than the second cladding (13). The ratio of the outside diameter of the first cladding (12) to the outside diameter of the core (11) is 1.15-1.25.

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 (1) having an outer diameter (D1) of greater than or equal to 8.2 ?m and less than or equal to 10.2 ?m; a first cladding (2) surrounding the core (1) and having an outer diameter (D2) of greater than or equal to 30 ?m and less than or equal to 45 ?m; a second cladding (3) surrounding the first cladding (2) and having a thickness (T) of greater than or equal to 7.4 ?m; and a support layer (4) surrounding the second cladding (3). The relative refractive index difference which is the ratio of the difference between the refractive index of the support layer (4) and that of the second cladding (3) to the refractive index of the support layer (4) is greater than or equal to 0.5%.