WDM coherent PDM-QPSK systems with and without inline optical dispersion compensation

Area of Science:

• Optical communication systems
• High-speed data transmission
• Fiber optic networks

Background:

• Wavelength-division multiplexing (WDM) is crucial for high-capacity optical networks.
• Polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) offers advanced modulation for increased data rates.
• Dispersion compensation is essential for maintaining signal integrity over long-haul fiber transmission.

Purpose of the Study:

• To compare the performance of 42.8-Gb/s and 112-Gb/s PDM-QPSK WDM systems.
• To evaluate the impact of inline dispersion compensation fiber (DCF) versus electronic dispersion compensation.
• To analyze the effects of fiber nonlinearities and local oscillator (LO) phase noise to amplitude noise conversion.

Main Methods:

• Numerical simulations of 1000-km standard single-mode fiber (SSM) transmission.
• Comparison of non-return-to-zero (NRZ) and time-interleaved return-to-zero (RZ) PDM-QPSK modulation formats.
• Analysis of nonlinear polarization scattering and LO phase noise-induced penalties.

Main Results:

• NRZ PDM-QPSK systems with DCF show lower tolerance to fiber nonlinearities than electronic compensation due to nonlinear polarization scattering.
• RZ PDM-QPSK significantly suppresses nonlinear polarization scattering, enhancing DCF system performance.
• The 112-Gb/s system with electronic compensation is sensitive to LO phase noise when using distributed feedback lasers.

Conclusions:

• RZ modulation is advantageous for PDM-QPSK WDM systems employing DCF, especially at lower data rates.
• Electronic dispersion compensation offers better nonlinearity tolerance for NRZ PDM-QPSK but is susceptible to LO phase noise penalties.
• System design choices, including modulation format and compensation method, critically impact performance in high-speed WDM transmission.