Compatible TDM/WDM PON using a single tunable optical filter for both downstream wavelength selection and upstream wavelength generation

We propose a hybrid time-division multiplexing/wavelength-division multiplexing passive optical network (TDM/WDM-PON) architecture compatible with the traditional TDM-PON configuration using a power splitter in the remote node. A tunable optical filter (TOF) is used to select the downstream wavelength in each optical network unit. Meanwhile, the TOF plays a second role of seeding a reflective semiconductor optical amplifier (RSOA) so as to construct a tunable fiber-ring laser as colorless upstream source. A stable performance is observed for the upstream laser source tuned from 1535 to 1565 nm and with a modulation data rate of 1.25 Gb/s. The upstream wavelength has a ∼ 0.1-nm offset with the central wavelength of the TOF when the RSOA is biased at its saturation region, which mitigates the Rayleigh backscattering and back reflection-induced crosstalk in single-fiber bidirectional PON systems.