Coupling characteristics of lens systems for laser diode modules using single-mode fiber

Abstract

The characteristics of lens systems for coupling InGaAsP laser diodes to single-mode (SM) fibers are studied. Two groups of lens systems are investigated. One group employs a combination of lenses and a SM fiber in a conventional configuration. The other group utilizes a combination of lenses and a virtual fiber, where the virtual fiber is formed by attaching a GRIN rod lens to the input endface of the SM fiber. The maximum coupling efficiency and misalignment tolerances for the optical circuit components in these lens systems are compared from the viewpoint of fabricating laser diode modules. It is confirmed that lens systems using virtual fibers offer better coupling characteristics than does the conventional coupling method.