Nonlinear inverse synthesis technique for optical links with lumped amplification

Area of Science:

• Optical communications
• Digital signal processing

Background:

• Fiber nonlinearity impairments degrade optical signal quality.
• The nonlinear inverse synthesis (NIS) method combats these impairments by encoding information on the nonlinear signal spectrum.
• The original NIS method is limited to ideal optical links with distributed Raman amplification.

Purpose of the Study:

• To propose and assess a modified NIS scheme applicable to standard optical links with lumped amplifiers (e.g., EDFA).
• To adapt the NIS technique for practical optical communication systems by accounting for fiber loss.

Main Methods:

• Developed a modified NIS scheme using a lossless path-averaged model that incorporates average fiber loss.
• Analyzed the error between lossless path-averaged and lossy models concerning transmission distance and input power.
• Numerically demonstrated the scheme's feasibility in burst-mode orthogonal frequency division multiplexing (OFDM) transmission with QPSK, 16QAM, and 64QAM.

Main Results:

• The error between the models increases linearly with transmission distance and input power.
• The proposed NIS scheme achieves performance improvements up to 3.5 dB.
• Results are comparable to multi-step per span digital back-propagation.

Conclusions:

• The modified NIS method effectively addresses fiber nonlinearity in standard optical links with lumped amplifiers.
• This approach offers a viable digital signal processing technique for advanced modulation formats in optical communications.
• The NIS technique shows promise for enhancing the performance of next-generation optical networks.