Small-form-factor fiber optic interface devices with an internal lens

A receptacle assembly for engaging a first fiber optic interface device having a first planar surface and a first lens, said receptacle assembly comprising:

• a light transmitting body with (i) a front section having a front end with a planar surface;
• (ii) an angled surface;
• and (iii) a curved optical surface situated to direct light to and to receive light from said angled surface, with said angled surface operably arranged between said curved optical surface and said planar front surface of the front section;
• a receptacle end cap disposed over the front section, the receptacle end cap having a body with a front end defined by a solid transparent endwall having a planar front outer surface that defines a second planar surface, and an opposite inner surface, with the inner surface having a receptacle lens that is spaced apart from and that faces the planar surface of the front section;
• and
• wherein the first and second planar surfaces defining a liquid-displacing interface configured to pass a substantially collimated light beam that is substantially the same diameter of the receptacle lens when the receptacle assembly and the first fiber optic interface device are engaged.