Extended reach OFDM-PON using super-Nyquist image induced aliasing

Area of Science:

• Optical Communications
• Signal Processing
• Photonics

Background:

• Passive optical networks (PONs) face dispersion limitations impacting reach and data rates.
• Double sideband (DSB) modulation and directed detection (DD) are common in PON systems.
• Orthogonal frequency division multiplexing (OFDM) is a key modulation technique in modern optical systems.

Purpose of the Study:

• To investigate a novel dispersion compensating technique for DSB-modulated DD-PON systems.
• To utilize super-Nyquist image induced aliasing for enhanced signal processing.
• To improve the performance of OFDM signals in long-haul optical transmissions.

Main Methods:

• Employing super-Nyquist image induced aliasing to introduce diversity in higher frequency components.
• Utilizing fractional sampling and per-subcarrier maximum ratio combining (MRC) to exploit this diversity.
• Evaluating conventional OFDM, discrete Fourier transform spread (DFT-S) OFDM, and code-division multiplexing OFDM (CDM-OFDM) signals.

Main Results:

• The DFT-S OFDM signal demonstrated superior performance due to spectrum spreading and better peak-to-average power ratio (PAPR).
• The proposed scheme extended the reach of a 10-GHz bandwidth QPSK modulated OFDM-PON to approximately 90 km.
• Experimental results showed increased achievable bit rates (10.5% and 5.2%) for DSB modulated OFDM-PONs over 48.3-km and 83.2-km standard single mode fiber (SSMF), respectively.
• A 40-Gb/s OFDM transmission over 83.2-km SSMF was successfully demonstrated.

Conclusions:

• The novel aliasing-based dispersion compensation technique effectively enhances the performance of OFDM-PON systems.
• The method allows for extended transmission distances and increased data rates without transmitter modifications.
• DFT-S OFDM signals are particularly well-suited for this technique, offering significant performance gains.