Optical frequency combs based on microresonators (microcombs) have been actively researched since the first experimental achievement of soliton mode-locking. Soliton pulses (dissipative Kerr solitons; DKSs) possess high repetition rates ranging from tens to hundreds of GHz. Thanks to this feature, DKSs are expected to benefit a wide range of applications, such as optical communications. In particular, DKSs are highly suitable for wavelength division multiplexing (WDM) transmission, which exploits an individual comb line as an optical carrier, owing to its broad bandwidth and low-noise properties  , . Although coherent transmissions are currently the mainstream of optical communication, transmissions employing the intensity-modulation direct-detection (IM-DD) method remain in use, e.g., in data centers . The advantage of an IM-DD transmission is that it does not require complex digital signal processors, resulting in a low power consumption and a small-signal delay, both of which are key characteristics required in the Beyond-5G technology. The IM-DD method can be used in conjunction with microcombs to achieve high-speed transmission while maintaining these advantages.