Patent ID: 8041519

Claim:
A method to produce an optical module able to output an optical signal with preset power for an analog data transmission, said optical module having a package to install a semiconductor chip of a DFB-LD, said method comprising steps of: randomly selecting a plurality of DFB-LD chips from a production unit of said DFB-LD; measuring a linear approximation of a slope efficiency against driving currents for respective DFB-LD chips selected in said selecting step; assembling said DFB-LD within respective housing; measuring an optimum driving current against a CSO characteristic of said DFB-LD assembled with said package, where said optimum driving current minimizes said CSO characteristic; determining a correlation between said linear approximations of said slope efficiency and said optimum driving current; selecting one semiconductor chip of said DFB-LD among semiconductor chips that are unselected in said randomly selecting step, said one semiconductor chip of said DFB-LD having a slope efficiency corresponding to said preset power through said correlation between said optimum driving current and said linear approximation of said slope efficiency; and assembling said one semiconductor chip of said DFB-LD selected in said selecting step in a package, evaluating a correlation between an optimum driving current with respect to a CSO characteristic and a gradient of a linear approximation of a slope efficiency with respect to a driving current for a plurality of DFB-LD chips selected from a production unit; screening a target chip of said DFB-LD included in said production unit but unselected in said evaluating step based on said correlation; and assembling said target chip screened in said screening step within said optical module.