Orthogonal chirp-division multiplexing for IM/DD-based short-reach systems.

Orthogonal chirp-division multiplexing (OCDM) has been recently proposed as an attractive modulation technique for realizing high-speed coherent lightwave systems in virtue of its resilience against system impairments. However, the complex-valued OCDM signal is not directly viable for optical intensity modulation and direct detection (IM/DD) systems. In this paper, a double-sideband (DSB)-modulated OCDM scheme is proposed for short-reach, high-speed IM/DD systems. In the proposed scheme, the real-valued OCDM signal is generated by a simple digital up-conversion technique, which converts the complex-baseband signal to a passband to avoid the aliasing for DSB modulation. At the receiver, inverse operations revert the signal back to the baseband for demodulation. Experiments were carried out to validate the feasibility and advantages of the proposed scheme, and OCDM signals with data rates up to 174.5 Gbit/s were successfully demonstrated. The results confirm that the proposed IM/DD-OCDM system is more robust to impairments and thus achieves better performance than a discrete multi-tone system.