devices [@hranilovic2005design; @4132995] and other limitations (e.g., modal dispersion in short-haul optical fiber links [@5223628] and multipath distortion in diffuse indoor wireless optical links[@kahn2002wireless]). Consequently, the coherent modulation formats and pulse shaping methods designed for conventional electrical channels (i.e., with no nonnegativity constraint on the transmitted signal) cannot be directly applied to IM/DD channels.

Pulse shaping for the purpose of reducing intersymbol interference (ISI) in conventional channels has been previously investigated in , [@5055024; @1089824; @beaulieu2002better; @1369626; @chandan05; @192386]. Much research has been conducted on determining upper and lower bounds on the capacity of IM/DD channels considering power and bandwidth limitations [@farid2010capacity; @hranilovic2004capacity; @farid2009capacity; @lapidoth2009capacity; @you2002capacity; @you2002upper]. In [@kahn2002wireless; @16882; @524287; @780164; @490239; @HranilovicLattice; @karout2010power; @FSOIMDD], the performance of various modulation formats in IM/DD channels were studied using rectangular or other time-disjoint (i.e., infinite-bandwidth) pulses. Hranilovic in [@1577875] pioneered in investigating the problem of designing strictly bandlimited pulses for IM/DD channels with nonnegative pulse-amplitude modulation (PAM) schemes. He showed the existence of nonnegative bandlimited Nyquist pulses, which can be used for ISI-free transmission over IM/DD channels, and evaluated the performance of such pulses. He also showed that any nonnegative root-Nyquist pulse must be time limited (i.e., infinite bandwidth). Hence receivers 