New evaluation method to maximize the permissible lateral and angular transmitter misalignments of collimated optical free space links

In this contribution different types of transmitter misalignments are analysed with the ZEMAX and MATLAB software tools (including measurements) to show their influence on free space optical (FSO) links. The paper presents and defines a method to find the permissible lateral and angular transmitter misalignment of a unidirectional FSO link by changing different optical parameters. The analysis leads to an optimization of such link scenarios. The evaluated optical wireless link consists of a lens collimating the beam radiated by an optical source and another lens focusing the beam on a receiver area (detector). The received optical power is simulated in ZEMAX for different lateral and angular transmitter misalignments and additionally for various receiver area shifts out of the focal length of the lens at the detector site. Supplementary measurements are done to estimate the minimum received optical power (ROP) required for such misaligned FSO links under consideration of a given data rate of 10 Gb/s. Using MATLAB the simulated data are compared with the minimum ROP. The misalignment parameter value pair consisting of two entries is calculated, which describes succinctly the permissible lateral and angular transmitter misalignment of an optical wireless system. A configuration of a lens system for the transmitter and receiver of a unidirectional FSO link can be found by generating and comparing these pairs for various lens combinations.