Sub-Nyquist field trial using time frequency packed DP-QPSK super-channel within fixed ITU-T grid

Area of Science:

• Optical Communications
• Signal Processing
• Telecommunications Engineering

Background:

• Super-channel technology is crucial for increasing optical network capacity.
• Spectral efficiency remains a key challenge in long-haul transmissions.
• Low-order modulation formats offer OSNR robustness but limited data rates.

Purpose of the Study:

• To demonstrate the Sub-Nyquist time frequency packing technique in a real-world super-channel field trial.
• To evaluate the performance of a 975 Gb/s DP-QPSK super-channel over a 995 km link.
• To assess the spectral efficiency and OSNR performance compared to existing systems.

Main Methods:

• Field trial transmission over a 995 km deployed link between Sydney and Melbourne.
• Utilized Sub-Nyquist time frequency packing with DP-QPSK modulation.
• Employed coherent detection with iterative maximum-a-posteriori (MAP) decoding at the receiver.
• Transmission within a 50 GHz ITU-T grid alongside 40/100 Gb/s channels.

Main Results:

• Successfully transmitted a 975 Gb/s DP-QPSK super-channel over 995 km.
• Achieved a spectral efficiency of 5.58 bit/s/Hz with OSNR comparable to 100 Gb/s channels.
• Demonstrated co-propagation with existing 40/100 Gb/s channels without additional penalty.
• Achieved a potential SE·d product of 9254 bit/s/Hz·km in a loopback configuration.

Conclusions:

• Sub-Nyquist time frequency packing is a viable technique for high-capacity long-haul optical transmissions.
• The demonstrated technique enables efficient spectral usage with robust, lower-complexity modulation formats.
• This advancement has significant implications for future optical network design and capacity upgrades.