Application of optical tapers to receivers in free space/atmospheric optical links

An application of optical tapers to receivers in free-space or atmospheric optical links is discussed. These tapers are proposed for use in a simple optical receiver that has a high tolerance to angular misalignments and supports a high bit rate by using a photodiode with a small active area. The receiver works on the principle that the taper, functioning as a waveguide, increases the effective receiving area of the photodiode and thus increases the field of view of the receiver without raising the diode capacitance. Experimental results show that an optical taper can effectively improve the tolerance of a freespace/atmospheric optical receiver to angular misalignments and that the loss introduced by the taper can be easily reduced to below 1 dB by a properly shaped taper with a magnification factor of about six