In this research, a ring-based wavelength-division-multiplexing passive optical network (WDM-PON) architecture is proposed to support the baseband and free space optical (FSO) communication simultaneously, when the same WDM downstream wavelengths are applied in the optical line termination (OLT). The optical modules of the OLT and remote node (RN) are designed to apply in the ring network architecture for bidirectional data access. Here, all the WDM wavelengths are divided into the downstream and upstream bands to avoid the Rayleigh backscattering (RB) noise through 51 km fiber connection. The 10 Gb/s on-off keying (OOK) bit error rate (BER) performances of downstream and upstream signals are also performed and analyzed. Moreover, all the measured baseband and FSO sensitivities of downstream and upstream signals can achieve enough power budgets to comply with the total insertion loss of proposed PON system under the forward error correction (FEC) target.