with matched filters are not suitable for Hranilovic’s signaling method. He concluded that transmission is possible with a bandwidth twice the required bandwidth over the corresponding conventional electrical channels. This work was extended to other Nyquist pulses that can introduce a trade-off between bandwidth and average optical power in [@4132995; @bhandari2007squared].

In this paper, we present a new signaling method for bandlimited IM/DD channels, in which the transmitted signal becomes nonnegative by the addition of a constant direct-current (DC) bias. This method provides us with two benefits: (i) We can transmit ISI-free with a bandwidth equal to that of coherent conventional channels, while benefiting from the reduced complexity and cost of IM/DD system. (ii) We can implement the system using either Nyquist pulses with sampling receiver or root-Nyquist pulses with matched filter receiver. By being able to use a larger variety of pulses, the transmitted power can be reduced compared with known methods, which is advantageous in power-sensitive optical interconnects and indoor wireless optical links. We also evaluate the spectral efficiency and optical power efficiency of binary and 4-PAM formats with Nyquist and root-Nyquist pulses for achieving a specific noise-free eye opening or a specific symbol-error-rate (SER).

The remainder of 