Linear crosstalk analysis of an un-amplified ring PON architecture

Passive optical network (PON) architectures have been proposed as a back haul for wireless networks, where the optical network units (ONUs) can now be interconnected with the antenna base stations. We focus on a ring PON approach with its inherent benefits and use simulation to analyze the effects of linear crosstalk in an un-amplified basic TDM optical ring. Our approach is based on simulation of the entire network using a combination of wavelength-domain and time-domain techniques. Typically PON networks are based on CWDM to maintain the cost of components low and in such case it is logical that any crosstalk will be negligible. However, the subpar performance of such components motivated our study into the crosstalk impact. We show that the tap ratio optimization which increases the number ONUs that can be served in the ring can also exacerbate the effects of linear interchannel crosstalk at the ONU's downstream signal receivers. The interchannel crosstalk originates from the upstream/LAN transmission and is due to non-ideal WDM couplers/splitters and optical switches that are needed for wavelength multiplexing/demultiplexing and protection against node and link failures, respectively.