Raman Amplification Optimization in Short-Reach High Data Rate Coherent Transmission Systems

Area of Science:

• Optical communications
• Fiber optic sensing
• Telecommunications engineering

Background:

• High-speed optical transmission systems are crucial for modern data networks.
• Optimizing optical amplifiers is key to overcoming signal degradation over long distances.
• Different amplification techniques, including Erbium-Doped Fiber Amplifiers (EDFA) and Raman amplifiers, have varying impacts on signal quality.

Purpose of the Study:

• To compare the transmission performance of 600 Gbit/s Polarization-Multiplexed 64-Quadrature Amplitude Modulation (PM-64QAM) Wavelength Division Multiplexing (WDM) signals.
• To evaluate various amplification schemes over 75.6 km of single-mode fiber (SMF).
• To determine the most effective amplification strategy for short-reach, high-capacity optical links.

Main Methods:

• Numerical simulations and experimental validation were employed.
• Transmission performance was assessed using different amplifier types: EDFA, discrete Raman, hybrid Raman/EDFA, and dual-order distributed Raman amplifiers.
• Focus was placed on first-order and second-order distributed Raman amplification with backward pumping.

Main Results:

• The first-order distributed Raman amplifier scheme with backward pumping demonstrated the best transmission performance.
• This scheme outperformed the second-order Raman scheme, which provided a flatter signal power variation.
• The first-order backward Raman pumping scheme achieved an optimal balance between amplified spontaneous emission (ASE) noise and fiber nonlinearity.

Conclusions:

• First-order backward distributed Raman amplification is highly effective for 600 Gbit/s PM-64QAM WDM signals over approximately 75 km of SMF.
• This approach offers a superior trade-off between noise and nonlinearity compared to other tested methods.
• The findings suggest practical implications for designing efficient short-reach optical communication systems.