An optical lens includes an aperture, a first lens, a second lens, a third lens, and a fourth lens sequentially in a direction. One of the first lens and the second lens has positive refracting power, and the other has negative refracting power. The third lens has refracting power, and is a lens with a largest diameter in the optical lens. The fourth lens has the refracting power. The four lenses are made of glass. For light having a wavelength of 1315 nm, a transmittance of the optical lens is greater than ninety percent.