Optical module and flexible printed circuit board

An optical module comprising:

• a package including a substrate that includes a first signal wiring formed on a first wiring layer, and a first ground wiring formed on a second wiring layer located below the first wiring layer;
• and
• a flexible printed circuit board including an upper surface wiring layer, a lower surface wiring layer, and a base layer disposed between the upper surface wiring layer and the lower surface wiring layer, and including a second signal wiring formed on the upper surface wiring layer, and a second ground wiring formed on the lower surface wiring layer,
• wherein the second signal wiring includes a lead portion protruding from the base layer in a first direction,
• the second ground wiring includes a ground terminal located further inside the flexible printed circuit board in the first direction than the lead portion,
• the lead portion is connected to the first signal wiring, and
• the ground terminal is connected to the first ground wiring.