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

Area of Science:

• Optical Communications
• Signal Processing
• Photonics

Background:

• Orthogonal chirp-division multiplexing (OCDM) offers resilience against system impairments in high-speed coherent lightwave systems.
• Complex-valued OCDM signals are incompatible with optical intensity modulation and direct detection (IM/DD) systems.

Purpose of the Study:

• To propose a double-sideband (DSB)-modulated OCDM scheme suitable for short-reach, high-speed IM/DD systems.
• To adapt OCDM for IM/DD systems by converting complex-baseband signals to real-valued passband signals.

Main Methods:

• A digital up-conversion technique generates a real-valued OCDM signal from a complex-baseband signal.
• Inverse operations at the receiver demodulate the signal after reverting it to baseband.
• Experimental validation of the proposed IM/DD-OCDM scheme.

Main Results:

• Demonstrated successful transmission of OCDM signals at data rates up to 174.5 Gbit/s.
• The proposed IM/DD-OCDM system exhibited enhanced robustness against system impairments.
• Achieved superior performance compared to discrete multi-tone (DMT) systems in IM/DD configurations.

Conclusions:

• The proposed DSB-modulated IM/DD-OCDM scheme is feasible for high-speed short-reach optical communication systems.
• This technique overcomes the limitations of complex-valued signals in IM/DD systems.
• The IM/DD-OCDM system provides a robust and high-performance alternative to existing modulation techniques.