Yequn Zhang

1.05Pb/s Transmission with 109b/s/Hz Spectral Efficiency using Hybrid Single- and Few-Mode Cores

We demonstrated 1.05-Pb/s transmission over 3km of multicore fiber with spectral efficiency of 109b/s/Hz, using twelve single-mode cores carrying DP-32QAM-OFDM signals and two few-mode cores carrying DP-QPSK in their LP01 and two LP11 modes.

Terabit/s Nyquist Superchannels in High Capacity Fiber Field Trials Using DP-16QAM and DP-8QAM Modulation Formats

We report the results of two field trials aimed at achieving high fiber capacity over regional and long-haul distances. In the first trial, 41 superchannels with digital Nyquist pulse-shaping were generated and tightly packed to fill up both C-band and L-band. Each subcarrier was modulated with 24.8-Gbaud dual-polarization 16 quadrature amplitude modulation (DP-16QAM) data. The signal carrying net 54.2 Tb/s data was transmitted over 634 km of dispersion uncompensated field-installed standard single mode fiber with the aid of hybrid EDFA and Raman amplification and digital coherent detection. In the second trial for long-haul distances, we extended the transmission distance over 1,822 km. This increase in reach was achieved by reducing the net total capacity to 40.5 Tb/s and modulating the signals with dual-polarization 8 quadrature amplitude modulation (DP-8QAM) Nyquist carrier modulation. A novel rate-adaptive low-density parity-check coding was employed, so that the transmitted channels can exhibit different code rates, adapted by the concatenation of hard-decision and soft-decision forward error correcting codes for enhancing error-correction capability. To the best of our knowledge, we achieved the highest field trial capacity to date at 54.2 Tb/s in regional distances. Furthermore, in long-haul applications, the reported capacity × distance product of 73.79 Pb/s·km is the highest to date.

High capacity field trials of 40.5 Tb/s for LH distance of 1,822 km and 54.2 Tb/s for regional distance of 634 km

40.5 Tb/s over 1,822 km and 54.2 Tb/s over 634 km field SSMF was realized using 41 Nyquist rate DP-8QAM and DP-16QAM superchannels. They are the highest field capacities for long-haul and regional distances achieved so far.

Staircase Rate-Adaptive LDPC-Coded Modulation for High-Speed Intelligent Optical Transmission

We propose staircase rate-adaptive LDPC-coded modulation that is suitable for high-speed intelligent optical transmission. Compared with shortening of LDPC codes, larger coding gain can be obtained and error floor can also be effectively mitigated.

Transoceanic Transmission of 40

We experimentally demonstrated transmitting 40 × 117.6 Gb/s 16 quadrature amplitude modulation with orthogonal frequency division multiplexing modulation over 10 181 km. The following techniques are applied to achieve error-free transmission: 1) hybrid large-core/ultralow-loss fibers were used for improving received optical signal-to-noise ratio while enhancing fiber nonlinearity tolerance; 2) multiband nonlinearity compensation algorithm was performed to further improve nonlinearity tolerance; 3) the forward error correction (FEC) limit of 5.3 dB provided by the concatenation of hard-decision and soft-decision FEC codes ensures to have error-free transmission after turbo equalizer with memory of three symbols, thus attaining a spectral efficiency of 4.7 b/s/Hz.

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Transmission of 117.6Gb/s optical PDM-16QAM OFDM signals over 10,181km is demonstrated at 25-GHz channel spacing with 4.7 b/s/Hz spectral efficiency. All the errors have been corrected by using 25% overhead QC-LDPC after multi-band nonlinearity compensation.

117.6 Gb/s PDM-OFDM-16QAM Over Hybrid Large-Core/Ultralow-Loss Fiber

We demonstrated the first 30Tb/s (350 × 85.74Gb/s) optical transmission over 10,181km using bidirectional C/L-bands, 121.2km hybrid fiber spans, DP-QPSK modulation and EDFAs. Achieved 306Petabit/s•km capacity × distance product is the highest reported to date for WDM transmission.

40×117.6 Gb/s PDM-16QAM OFDM transmission over 10,181 km with soft-decision LDPC coding and nonlinearity compensation

Leveraging the advanced coherent optical communication technologies, this paper explores the feasibility of using four-dimensional (4D) nonbinary LDPC-coded modulation (4D-NB-LDPC-CM) schemes for long-haul transmission in future optical transport networks. In contrast to our previous works on 4D-NB-LDPC-CM which considered amplified spontaneous emission (ASE) noise as the dominant impairment, this paper undertakes transmission in a more realistic optical fiber transmission environment, taking into account impairments due to dispersion effects, nonlinear phase noise, Kerr nonlinearities, and stimulated Raman scattering in addition to ASE noise. We first reveal the advantages of using 4D modulation formats in LDPC-coded modulation instead of conventional two-dimensional (2D) modulation formats used with polarization-division multiplexing (PDM). Then we demonstrate that 4D LDPC-coded modulation schemes with nonbinary LDPC component codes significantly outperform not only their conventional PDM-2D counterparts but also the corresponding 4D bit-interleaved LDPC-coded modulation (4D-BI-LDPC-CM) schemes, which employ binary LDPC codes as component codes. We also show that the transmission reach improvement offered by the 4D-NB-LDPC-CM over 4D-BI-LDPC-CM increases as the underlying constellation size and hence the spectral efficiency of transmission increases. Our results suggest that 4D-NB-LDPC-CM can be an excellent candidate for long-haul transmission in next-generation optical networks.

30Tb/s C- and L-bands bidirectional transmission over 10,181km with 121km span length

Inspired by recent demonstrations of orbital angular momentum-(OAM)-based single-photon communications, we propose two quantum-channel models: (i) the multidimensional quantum-key distribution model and (ii) the quantum teleportation model. Both models employ operator-sum representation for Kraus operators derived from OAM eigenkets transition probabilities. These models are highly important for future development of quantum-error correction schemes to extend the transmission distance and improve date rates of OAM quantum communications. By using these models, we calculate corresponding quantum-channel capacities in the presence of atmospheric turbulence.

Evaluation of four-dimensional nonbinary LDPC-coded modulation for next-generation long-haul optical transport networks

The first experimental demonstration of nonbinary-LDPC-coded optical transmission is presented. Using DQPSK, we can achieve >8dB and ∼10dB net coding gains at the BER of 10⁻⁶ in the absence and presence of I/Q imbalance, respectively.