Multicore fiber for communication

Abstract

A multicore fiber for communication 10 which allows propagation of an optical signal includes: a clad 12 ; a core 11 a which is arranged in a center of the clad 12 ; and seven to ten cores 11 b which are arranged at equal intervals surrounding the core 11 a , and the cladding diameter is 230 μm, distances between centers of the mutually neighboring cores 11 a and 11 b are 30 μm or more, distances between the centers of the cores 11 b and an outer peripheral surface of the clad 12 are 35 μm or more and a mode field diameter of light propagating in the cores 11 a and 11 b is 9 μm to 13 μm.

1 . A multicore fiber for communication comprising:
 a clad;   a core which is arranged in a center of the clad; and   seven to twelve cores which are each arranged at equal distances from the center and at equal intervals surrounding the core,   wherein an cladding diameter is 230 μm or less.   
     
     
         2 . A multicore fiber for communication comprising:
 a clad;   three cores which are each arranged at equal distances from a center of the clad and at equal intervals; and   five to twelve cores which are each arranged at equal distances from the center and at equal intervals surrounding the three cores,   wherein an cladding diameter is 230 μm or less.   
     
     
         3 . A multicore fiber for communication comprising:
 a clad;   a core which is arranged in a center of the clad;   six cores which are each arranged at equal distances from the center and at equal intervals surrounding the core; and   one to six cores which are arranged between a connection line which connects two mutually neighboring cores of the six cores and the core, and on the line which is vertical to the connection line and passes on the core,   wherein an cladding diameter is 230 μm or less.   
     
     
         4 . A multicore fiber for communication comprising:
 a clad;   a core which is arranged in a center of the clad; and   eight cores which surround the core and are arranged at equal intervals to form a square shape as a whole,   wherein an cladding diameter is 230 μm or less.   
     
     
         5 . A multicore fiber for communication comprising:
 a clad;   four cores which are each arranged at equal distances from a center of the clad and at equal intervals; and   eight cores which are arranged on an extended line which connects two mutually neighboring cores of the four cores, and which are arranged such that a distance to a center of a closest core of the four cores is equal to distances between centers of the two mutually neighboring cores of the four cores,   wherein an cladding diameter is 230 μm or less.   
     
     
         6 . The multicore fiber for communication according to  claim 1 , wherein:
 a mode field diameter of light propagating in each of the cores is 9 μm to 13 μm; and   a distance between centers of the cores which are mutually neighboring is 30 μm or more, and a distance between the center of the core and an outer peripheral surface of the clad is 35 μm or more.   
     
     
         7 . The multicore fiber for communication according to  claim 1 , further comprising:
 an inner clad layer which has a lower refractive index than that of the core and which surrounds each core; and   a low refractive index layer which has a lower average refractive index than those of the clad and the inner clad layer and which surrounds each inner clad layer.   
     
     
         8 . The multicore fiber for communication according to  claim 7 , wherein the low refractive index layer is made of a material having a lower refractive index than those of the clad and the inner clad layer. 
     
     
         9 . The multicore fiber for communication according to  claim 7 , wherein, in the low refractive index layer, a plurality of low refractive index portions which has lower refractive indices than those of the clad and the inner clad layer is formed surrounding the inner clad layer. 
     
     
         10 . The for communication multicore fiber for communication according to  claim 9 , wherein the low refractive index portion is a hole. 
     
     
         11 . The multicore fiber for communication according to  claim 2 , wherein:
 a mode field diameter of light propagating in each of the cores is 9 μm to 13 μm; and   a distance between centers of the cores which are mutually neighboring is 30 μm or more, and a distance between the center of the core and an outer peripheral surface of the clad is 35 μm or more.   
     
     
         12 . The multicore fiber for communication according to  claim 3 , wherein:
 a mode field diameter of light propagating in each of the cores is 9 μm to 13 μm; and   a distance between centers of the cores which are mutually neighboring is 30 μm or more, and a distance between the center of the core and an outer peripheral surface of the clad is 35 μm or more.   
     
     
         13 . The multicore fiber for communication according to  claim 4 , wherein:
 a mode field diameter of light propagating in each of the cores is 9 μm to 13 μm; and   a distance between centers of the cores which are mutually neighboring is 30 μm or more, and a distance between the center of the core and an outer peripheral surface of the clad is 35 μm or more.   
     
     
         14 . The multicore fiber for communication according to  claim 5 , wherein:
 a mode field diameter of light propagating in each of the cores is 9 μm to 13 μm; and   a distance between centers of the cores which are mutually neighboring is 30 μm or more, and a distance between the center of the core and an outer peripheral surface of the clad is 35 μm or more.   
     
     
         15 . The multicore fiber for communication according to  claim 2 , further comprising:
 an inner clad layer which has a lower refractive index than that of the core and which surrounds each core; and   a low refractive index layer which has a lower average refractive index than those of the clad and the inner clad layer and which surrounds each inner clad layer.   
     
     
         16 . The multicore fiber for communication according to  claim 3 , further comprising:
 an inner clad layer which has a lower refractive index than that of the core and which surrounds each core; and   a low refractive index layer which has a lower average refractive index than those of the clad and the inner clad layer and which surrounds each inner clad layer.   
     
     
         17 . The multicore fiber for communication according to  claim 4 , further comprising:
 an inner clad layer which has a lower refractive index than that of the core and which surrounds each core; and   a low refractive index layer which has a lower average refractive index than those of the clad and the inner clad layer and which surrounds each inner clad layer.   
     
     
         18 . The multicore fiber for communication according to  claim 5 , further comprising:
 an inner clad layer which has a lower refractive index than that of the core and which surrounds each core; and   a low refractive index layer which has a lower average refractive index than those of the clad and the inner clad layer and which surrounds each inner clad layer.