Laser linewidth tolerance for nonlinear frequency division multiplexing transmission with discrete spectrum...

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Carrier phase estimation (CPE) is crucial for coherent fiber optical transmission.
• Few studies address CPE in nonlinear Fourier transform (NFT) based transmission systems.
• Laser linewidth introduces phase noise, affecting nonlinear spectra and scattering data.

Purpose of the Study:

• To investigate the effectiveness of feed-forward and blind phase search (BPS) CPE schemes in nonlinear frequency division multiplexing (NFDM) transmission.
• To compare the performance of these CPE schemes for various modulation formats.
• To experimentally verify the BPS algorithm in an NFDM system.

Main Methods:

• Utilized feed-forward (M-th power) and blind phase search (BPS) algorithms for CPE.
• Simulated NFDM transmission with discrete spectrum modulation.
• Performed performance comparison across Quadrature Phase Shift Keying (QPSK), 8-Phase Shift Keying (8-PSK), and 16-Amplitude Phase Shift Keying (16-APSK) modulation formats.
• Experimentally verified the BPS algorithm in a back-to-back transmission setup.

Main Results:

• Both feed-forward and BPS CPE methods function well in NFDM transmission.
• Determined laser linewidth tolerances for QPSK (2.3 MHz), 8-PSK (1.05 MHz), and 16-APSK (250 KHz) at a 1-dB OSNR penalty (BER=10^-3).
• Successfully experimentally verified the BPS algorithm using a semiconductor laser with a 100 KHz linewidth.

Conclusions:

• Feed-forward and BPS CPE are viable for NFDM systems with discrete spectrum modulation.
• BPS demonstrates robust performance and is experimentally validated, showing its practical applicability.
• The study quantifies laser linewidth limitations for different modulation formats in NFDM transmission.