I found these paper interesting for your topic
Design of multi user free space optical communication system for … – I am browsing [Design of multi user free space optical communication system for …]. Have a look at it! https://www.google.co.in/url?q=http://www.ijettjournal.org/2015/volume-24/number-2/IJETT-V24P218.pdf&sa=U&ved=0CA8QFjADahUKEwj-7buq3P3GAhXDUY4KHYH1A40&usg=AFQjCNGs70YQIUZ8S6q8UC7pb0DMpvY09w
http://www.mdpi.com/2304-6732/2/1/139
Let me know if it helps