Optimization of training sequence for DFT-spread DMT signal in optical access network with direct detection utilizing...

Area of Science:

• Optical Communications
• Digital Signal Processing

Background:

• Discrete multi-tone (DMT) modulation is crucial for high-speed optical data transmission.
• Managing signal impairments like Peak-to-Average Power Ratio (PAPR) and narrowband interference is challenging in DMT systems.
• Directly Modulated Lasers (DMLs) are cost-effective light sources for short-reach optical links.

Purpose of the Study:

• To experimentally demonstrate the feasibility of transmitting a high-speed DFT-spread 32 QAM-DMT signal over standard single-mode fiber using a DML.
• To evaluate the effectiveness of DFT-spreading in mitigating signal impairments.
• To identify the optimal training sequence (TS) for robust channel estimation in this system.

Main Methods:

• Transmission of a 79.86-Gb/s DFT-spread 32 QAM-DMT signal over a 20-km standard single-mode fiber (SSMF) link.
• Utilizing a Directly Modulated Laser (DML) as the optical transmitter.
• Comparing various training sequence (TS) symbols for channel estimation, including digital BPSK/QPSK formats.

Main Results:

• Successful experimental demonstration of 79.86-Gb/s signal transmission.
• DFT-spread significantly reduced the PAPR of the DMT signal.
• DFT-spread effectively mitigated narrowband interference and high-frequency power attenuation.
• Digital BPSK/QPSK modulation format TS showed superior performance in channel estimation against optical link noise.

Conclusions:

• DFT-spread 32 QAM-DMT signaling is a viable technique for high-speed optical transmission over SSMF using DMLs.
• DFT-spreading offers significant advantages in PAPR reduction and interference resilience.
• Optimized TS selection, particularly digital BPSK/QPSK, is critical for accurate channel estimation and overall system performance.