Patent ID: 6909557

Claim:
An optical coupling system comprising: a first lens having an incident surface disposed in a certain direction and having a positive refractive power, by said first lens, Gaussian beam-like luminous flux incident on said incident surface from a light source being converted into approximately parallel luminous flux; and a second lens having the same refractive power as that of said first lens but having an incident surface and exit surface disposed in a reverse direction, by said second lens, said approximately parallel luminous flux incident on said incident surface of said second lens being converted into converged luminous flux, said converged luminous flux being incident on a light-receiving unit, wherein said light receiving unit is an optical fiber, and; wherein a distance 2L between the two lenses is selected to be in a range given by an expression: 1.8Lmax≦2L≦2Lmax in which 2Lmax is a maximum distance allowing beam waists to be formed at equal distance from the two lenses respectively.