He is strong like a stone.

My specialty is fiber optics.

It's difficult to understand the principles of electrooptics.

He is an expert in fiber optics.

He is immersed in the study of geometrical optics.

Let's solve this problem together.

Cao Wei was one of the Three Kingdoms period in China.

He is working as a military sergeant.

He is working in the navy as a petty officer.

He is affiliated with the military as an airman.