Patent ID: 7044652

Claim:
An optical transmission module comprising: a light emitting element; an optical fiber; a first lens for collimating light from the light emitting element; a second lens for focusing said collimated light to said optical fiber; a package to which the second lens is fixed to maintain airtightness at an inside of the package; and a subassembly on which the light emitting element and the first lens are mounted, the subassembly being disposed in the inside of the package to be fixed to a bottom face of the package; wherein when a focal length of said first lens is designated by a notation f 1 and a focal length of said second lens is designated by a notation f 2 , said first lens and said second lens are arranged such that an optical distance d between a principal plane of a side of said first lens proximate to said second lens and a principal plane of a side of said second lens proximate to said first lens satisfies |d−(f 1 +f 2 )|≦5×f 1 ; and wherein said first lens and said second lens are arranged such that a relationship between said focal length f 1 of said first lens and said focal length f 2 of said second lens becomes f 2 /f 1 ≦5.