Hybrid FSO-WDM (Free Space Optics Wave Division Multiplexing) can potentially be used to enhance the capacity of 5G wireless services. WDM-PON is briefly where one single mode fiber (SMF) wire carries multiple data streams to different destinations via different wavelengths of light. Splitters and combiners are used to divide and combine the wavelengths. WDM-PON systems can achieve bandwidth requirements to end users but can suffer performance losses over difficult terrain.
Hybrid FSO-WDM can resolve some of these concerns, with FSO and fiber covering long hauls and 5G New Radio (NR) or the high band sub-terahertz spectrum between 100 and 300 GHz. While its high frequency allows for very high data rates, it also results in limited transmission range due to air loss. FSO/fiber on the other hand is difficult to connect to multiple mobile users. In order to support such a hybrid FSO-WDM scenario FSO can be used bridge the gap over difficult terrain for SMF or ground based fiber, such as hills, buildings or rivers. This is tested in the scenario of a 15km SMF, then 600 m and 15km SMF run, with the 600m FSO run hypothetically serving as a bridge across terrain.
The impact of RB on these FSO bridges and its potential suppression techniques such as advanced modulation and NR-sub-THz channels are evaluated as well.
Lastly the performance techniques of the WDM-FSO link are mathematically and simulationally modeled in the context of 5G systems, in terms of attenuation, received power, impact of weather conditions and modulation formats.