In the present paper, the design of the non-imaging totally internally reflecting concentrator family denominated optical antennas (OAs) is discussed, and its use for indoor optical wireless communication systems is explained. The lenses presented here can be designed to provide a prescribed angular response in order to limit the central wavelength shift in thin-film optical filters. They can also be designed for any specific field-of-view (FOV), which allows greater rejection of unwanted background radiation and higher gains. The use of a variety of optical filters to achieve a high signal-to-noise ratio at the receiver is described. Design methods and properties of different Optical Antennas are explained. Comparisons of size and performance of total internal reflection based concentrators with those based on dielectric hemispheres and compound parabolic concentrators (CPCs) are carried out. Finally different experimental results are presented.