Patent ID: 6847770

Claim:
A lens function-including optical fiber comprising: at least one information transmission optical fiber; and at least one gradient index optical fiber having an outer diameter equal to that of said information transmission optical fiber and having a length exhibiting a specific lens function, said gradient index optical fiber being jointed or contacted with an end surface of said information transmission optical fiber, and wherein, when a refractive-index distribution of said gradient index optical fiber in a wavelength range used is given by the expression: n ( r ) 2 =n 0 2 ·{1−( g·r ) 2 +h 4 ( g·r ) 4 +h 6 ( g·r ) 6 +h 8 ( g·r ) 8 + . . . }, said gradient index optical fiber satisfies a condition: 0.1≦n 0 ·g·r 0 ≦0.5 in which r is a distance from an optical axis, n(r) is a refractive index in a position at the distance r from the optical axis, n 0 is a refractive index on the optical axis, r 0 is a radius of said gradient index optical fiber, g is a refractive-index distribution coefficient, and h 4 , h 6 , h 8 . . . are high-order refractive-index distribution coefficients respectively.