Focused Optics boost Energy weapons by increasing their maximum range. This special does not affect minimum range.
Strategy and Setup
Focused Optics are essential for most Energy weapons because they have short range by default and are easily kited by longer-ranged Explosive and Projectile weapons.
Focused Optics cost a lot of mass, making Explosive and Projectile weapons more viable in some situations simply because they weigh less and do not require specials to achieve long range.
They are helpful but unnecessary on cutters which rely on their speed to catch up to enemy ships. This also applies to base attack fleets; after all, modules cannot fly away and will eventually get in range of your ships.