Digital upstream crosstalk cancellation for future (T)WDM-PON systems

We experimentally demonstrate a multiple-input multiple-output (MIMO) scheme for compensating upstream crosstalk in (T)WDM passive optical network (PON) systems in the electrical domain. The scheme relaxes the optical receiver filter isolation requirements by up to 9 dB, and thus enables narrower channel spacings. We show experimentally that in the case of no or low oversampling of 1 or 2 samples per symbol (Sps), the MIMO scheme can only be applied if all channels are fully symbol aligned, whereas by oversampling at 3 Sps or higher, operation is possible without symbol alignment.