Flexible substrate and optical device

An optical device comprising:

• a flexible substrate comprising:
• an insulating substrate having a first surface and a second surface opposite to the first surface, the insulating substrate including resin;
• a first connection portion configured to be connected with an external conductor and having a first conductor, a first ground pattern, and a second ground pattern on the first surface, the first ground pattern and the second ground pattern being spaced apart from the first conductor and respectively located at either side of the first conductor;
• a conductor pattern formed on the second surface, the conductor pattern being connected to the first conductor through a first via wire which passes through the insulating substrate;
• and
• a third ground pattern formed on the second surface, the third ground pattern being connected to the first ground pattern through a second via wire which passes through the insulating substrate, wherein a distance between the conductor pattern and the third ground pattern is smaller than a distance between the first conductor and the first ground pattern;
• a housing including an optical element;
• a receptacle connected to the housing;
• and
• a lead pin configured to connect the housing and the flexible substrate.