Optical subassembly

1. An optical subassembly, comprising:

an eyelet including a first surface, a second surface arranged on an opposite side from the first surface, and a plurality of through-holes penetrating from the second surface through the first surface;

a plurality of lead terminals, which are to be inserted into the plurality of through-holes, and to at least a part of which differential electrical signals are to be input;

a relay substrate including a lead connection surface extending in a normal direction of the first surface, and a first bonding surface adjacent to the lead connection surface, and having a first conductor pattern and a second conductor pattern formed to extend across the lead connection surface and the first bonding surface, in which the first conductor pattern and the second conductor pattern formed on the lead connection surface are to be connected to at least a part of the plurality of lead terminals with a solder or conductive adhesive, and are configured to receive inputs of the differential electrical signals;

a device mounting unit including a second bonding surface having formed thereon a third conductor pattern and a fourth conductor pattern, to which the differential electrical signals are to be input; and

an optical device, which is to be mounted on the device mounting unit and electrically connected to the third conductor pattern and the fourth conductor pattern, and is configured to convert one of an optical signal and the differential electrical signals into the other,

wherein the first conductor pattern and the second conductor pattern on the first bonding surface are to be connected to the third conductor pattern and the fourth conductor pattern on the second bonding surface with bonding wires, respectively, and

wherein the first bonding surface and the second bonding surface have normal directions in the same direction.

2. The optical subassembly according to claim 1 , further comprising a temperature adjustment device, which is arranged to be in contact with the first surface, and is configured to adjust a temperature of the optical device.

3. The optical subassembly according to claim 2 , further comprising a subcarrier, which is to be mounted on the temperature adjustment device, and on which the device mounting unit is to be mounted.

4. The optical subassembly according to claim 3 , wherein the subcarrier has a center of gravity arranged to be displaced toward the relay substrate with respect to a center of gravity of the eyelet.

5. The optical subassembly according to claim 3 ,

wherein the relay substrate further includes, as a surface adjacent to the first bonding surface, a first ground pattern surface having formed thereon a first ground pattern connected to a ground,

wherein the subcarrier includes, as a surface parallel to the first ground pattern surface, a second ground pattern surface having formed thereon a second ground pattern connected to the ground, and

wherein the first ground pattern is connected to the second ground pattern by bonding wires.

6. The optical subassembly according to claim 5 ,

wherein the first ground pattern is arranged to extend across the first bonding surface, and

wherein the first ground pattern arranged on the first bonding surface is arranged on both sides of the first conductor pattern and the second conductor pattern.

7. The optical subassembly according to claim 5 , wherein the device mounting unit is a metal block.

8. The optical subassembly according to claim 5 , wherein the device mounting unit includes a third ground pattern, which is connected to the ground, and extends across at least two surfaces that are adjacent to each other.

9. The optical subassembly according to claim 1 , wherein the bonding wires comprise three or more pairs of bonding wires.

10. The optical subassembly according to claim 1 ,

wherein the device mounting unit further includes, as a surface adjacent to the second bonding surface, a device mounting surface, on which the optical device is to be mounted, and

wherein the third conductor pattern and the fourth conductor pattern are arranged to extend across the device mounting surface and the second bonding surface.

11. The optical subassembly according to claim 1 ,

wherein the plurality of lead terminals include a pair of lead terminals, to which corresponding signals are to be input, and

wherein the pair of lead terminals are fixed to a single through-hole penetrating through the eyelet with a dielectric material.