Orthogonal time-frequency domain multiplexing with multilevel signaling

Area of Science:

• Optical communications
• Signal processing
• Telecommunications engineering

Background:

• Current optical multiplexing techniques face limitations in spectral efficiency and speed.
• Electronic response limitations hinder high-bandwidth optical transmission.

Purpose of the Study:

• To propose and investigate an optical multiplexing technique for ultrafast, high-spectral-efficiency transmission.
• To demonstrate the feasibility of orthogonal time-frequency domain multiplexing (OTFDM) with multilevel signaling.

Main Methods:

• Generation of optical rectangular combs using electro-optic modulators for data modulation and multiplexing.
• Optical domain demultiplexing and coherent demodulation using multi-frequency homodyne mixing.
• Coherent matched detection to down-convert target OTFDM tributary channels to baseband frequencies.

Main Results:

• Analytical and numerical proof of successful OTFDM multiplexing and demultiplexing of multilevel signals (nPSK, nQAM).
• Retention of orthogonality between tributaries during the OTFDM process.
• Achieved spectral efficiency of 1 Baud/Hz per single polarization, reaching the Nyquist limit.

Conclusions:

• OTFDM with multilevel signaling offers a viable solution for ultrafast, high-spectral-efficiency optical transmission.
• The proposed method bypasses the need for fast Fourier transform circuits or optical channel selection filters.
• This technique enables high-bandwidth operation unaffected by electronic limitations in transmitters or receivers.