Time-domain uplink synchronization method for a spectral efficient OFDMA-based PON

The feasibility of a time-domain technique, proposed for uplink synchronization of the bandwidth scalable orthogonal frequency division multiple access passive optical network (BS-OFDMA PON), is experimentally demonstrated. The results show that a delay variation of less than 50% of the cyclic prefix is tolerable, relaxing the thin time synchronization required in the uplink of the evaluated architecture. Moreover, we enhance the spectral efficiency of the BS-OFDMA PON by reducing the guard band (${B_g}$B
g
) between the optical carrier and the signal bandwidth, as well as by eliminating the frequency gap (${\Delta_{{f_G}}}$Δ
f
G
) between the optical network units. The downlink results demonstrate that ${\Delta_{{f_G}}}$Δ
f
G
can be eliminated with negligible performance penalties, and B
g
can be reduced to almost half the signal bandwidth. Error-free transmissions were achieved after uplink propagation over 45 km of single-mode fibers with received power of ≈−16.8dBm and ${B_g}$B
g
=450MHz, with a signal bandwidth of 1 GHz.