Optical module implementing laser diodes
An optical module that provides a feedthrough to carry an electrical signal output from and/or provided to a semiconductor optical device is disclosed. The feedthrough has a signal pad that carries the electrical signal thereon and at least two ground pads sandwiching the signal pad therebetween. The feedthrough further provides a cavity provided under the signal pad and spaces each between the signal pad and the ground pads.
1. An optical module comprising: a semiconductor optical device that converts signals between an electrical form and an optical form; a housing that encloses the semiconductor optical device; and a feedthrough made of insulating material and attached to the housing, the feedthrough having an interconnection, a signal pad connected with the interconnection, and at least two ground pads sandwiching the signal pad, the electrical signal being carried between the signal pad and the semiconductor optical device through the interconnection, wherein the feedthrough further includes a cavity under the signal pad and spaces between the signal pad and the ground pads, wherein the feedthrough further provides a ground layer provided under the cavity, the cavity exposing the ground layer.
2. The optical module according to claim 1 , wherein the cavity has a height at least half of a distance between the ground layer and the signal pad.
3. The optical module according to claim 1 , wherein the feedthrough further includes walls sandwiching the cavity and under the ground pads, the walls each having a via hole electrically connecting the ground pads with the ground layer.
4. The optical module according to claim 1 ,
further comprising a flexible printed circuit (FPC) board,
wherein the FPC board includes a signal pad and at least two ground pads, the signal pad in the FPC board being fixed to the signal pad in the feedthrough, the ground pads in the FPC board being fixed to the ground pads in the feedthrough.
5. The optical module according to claim 1 ,
wherein the feedthrough has a plurality of ceramic layers.
6. The optical module according to claim 1 ,
wherein the housing has a rectangular plane shape with a longitudinal side and a lateral side, the longitudinal side being determined by a front wall and a rear wall each extending along the lateral side, and
wherein the feedthrough is fixed to the rear wall of the housing and has a width along the lateral side substantially equal to a length along the lateral side of the housing.
7. The optical module according to claim 6 ,
wherein the cavity extends along the longitudinal side of the housing.
8. The optical module according to claim 6 ,
wherein the feedthrough has sides extending along the longitudinal side of the housing and determining the width of the feedthrough, and
wherein the cavity extends form one of the sides to another of the sides of the feedthrough along the lateral side of the housing.