PMD compensation in fiber-optic communication systems with direct detection using LDPC-coded OFDM.

Area of Science:

• Optical Communications
• Signal Processing
• Coding Theory

Background:

• Polarization-mode dispersion (PMD) degrades signal quality in fiber-optic systems.
• Orthogonal frequency division multiplexing (OFDM) is a robust modulation technique.
• Low-density parity-check (LDPC) codes offer powerful error correction.

Purpose of the Study:

• To demonstrate the feasibility of PMD compensation in direct-detection optical systems.
• To evaluate the effectiveness of LDPC-coded OFDM for PMD mitigation.
• To introduce novel LDPC code designs for PMD compensation.

Main Methods:

• Utilizing a simple channel estimation technique.
• Employing LDPC-coded OFDM in a direct-detection system.
• Designing LDPC codes based on difference systems and product of combinatorial designs.

Main Results:

• Complete compensation of first-order PMD degradation was achieved.
• Effective compensation was demonstrated even for differential group delay (DGD) up to 4/BW.
• Two new classes of LDPC codes suitable for PMD compensation were introduced.

Conclusions:

• LDPC-coded OFDM with direct detection is a viable solution for PMD compensation.
• The proposed channel estimation technique and LDPC codes enhance system performance.
• This approach offers a promising direction for future high-speed optical communication systems.