In this paper, we propose the use of multilevel optical transmission over POF, i.e., the use of N-PAM modulation formats rather than OOK (also called 2-PAM) in order to overcome bandwidth limitation. By sending log_2(N) bit per symbol, N-PAM allows to increase the actual bit rate given the same channel bandwidth by a factor equal to log_2(N). For instance, 4-PAM allows doubling the bit rate with respect to standard OOK, while 8-PAM gives a threefold increase. For instance, a channel with 100 MHz bandwidth associated with 8-PAM transmission can easily carry a bit rate in the 300-400Mbit/s range. On the other hand, increasing the number of level N increases the power requirements at the receiver (for instance, 4-PAM pays a 4.7dB power penalty to OOK), and the complexity of TX/RX electronics.