Free Space Optical Non-Orthogonal Multiple Access Experimentation

Free Space Optical (FSO) multi-user communication provides high aggregate bandwidth and link robustness attributable to spatial diversity. The primary challenge for this technology is interference among multiple users at the receiver. A non-orthogonal multiple access (NOMA) technique multiplexes numerous users in the power domain at the same time and frequency resource. Thus, different users simultaneously transmit their signals with various power levels. The receiver then decodes user data individually from the overlapped signal using successive interference cancellation (SIC). This paper reports the use of NOMA in an FSO link with two users and details an investigation of the effects of power allocation and channel estimation on the user's signals demodulation accuracy. Analysis of varying data rate and system capacity gain are explored. Experimental results indicate that accurate channel estimation and optimum power allocation ratio can improve the accuracy of signal reconstruction. Difference in data rate tested proved negligible to signal demodulation quality.