Ultra Large Effective Area Fiber Research Articles

640-Gbps/Carrier WDM Transmission over 6,400 km Based on PS-16QAM at 106 Gbaud Employing Advanced DSP

We experimentally demonstrated a 5-channel 125-GHz-grid wavelength division multiplexing (WDM) transmission over 6,400-km Raman amplified ultra large effective area fiber (ULAF) with 848-Gbps/carrier line-rate and 640-Gbps/carrier net-bit-rate. Our transmission is based on probabilistically shaped (PS) dual-polarization 16-ary quadrature-amplitude-modulation (16QAM) considering 25%-overhead low-density parity-check threshold of 4.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> bit-error-rate. By utilizing a high-speed digital-analog-converter (DAC) with a 3-dB bandwidth of 35 GHz and innovative pre-equalization based on 4-level pulse-amplitude-modulation (PAM4), 106-Gbaud 16QAM signal is reliably generated and transmitted. Besides, the transmission distance is improved obviously by using ULAF and Raman amplifier. Our results show that the PS-16QAM outperforms the regular-16QAM by around 1.5-dB sensitivity gain and 33% transmission-distance improvement. Furthermore, we have successfully applied Volterra nonlinear equalization (VNLE) to ultra-long-haul coherent optical transmission and proposed a modified offline digital-signal-processing process. By utilizing VNLE, another 15% reach improvement is obtained for PS-16QAM signal. Our work can provide an effective solution for a 600G+ ultra-long-haul transmission. As we know, this is the first time to achieve 640-Gbps/carrier WDM transmission over 6,400 km based on 106-Gbaud PS-16QAM.

High Spectral Efficiency 400 Gb/s Transmission by Different Modulation Formats and Advanced DSP

We experimentally demonstrate probabilistically shaped 64-ary quadrature-amplitude-modulation (64QAM) 50-GHz-grid wavelength-division-multiplexing (WDM) transmission with a bit rate of 400-Gbit/s per channel over 3,600-km Raman-amplified ultra-large effective area fiber (ULAF). Our results show that the probabilistically shaped 64QAM outperforms the hybrid-32/64QAM by 50% reach improvement. Thanks to pre-equalization and look-up-table pre-distortion, a 5.5-dB optical signal-to-noise ratio (OSNR) gain can be obtained. Furthermore, utilizing ULAF with Raman amplifier causes an apparent improvement on the transmission performance compared with using the SSMF with EDFA. We also compare the optical coupler with the wavelength selective switch utilized in the WDM system to explore a suitable way for WDM transmission. Advanced DSP including Butterworth low-pass digital filter is also used at the receiver end.

400 G Transmission of Super-Nyquist-Filtered Signal Based on Single-Carrier 110-GBaud PDM QPSK With 100-GHz Grid

We experimentally demonstrate a coherent transmission system with a high symbol rate using up to 110-GBaud PDM-QPSK signals. Super-Nyquist-filtering technology is used to narrow down the bandwidth of a single channel on a 100-GHz grid. The performance of the high baud rate electronic time division multiplexed-based super-Nyquist-filtered signal is also studied under the aggressive optical filtering elements in multiple reconfigurable optical add-drop multiplexers (ROADMs) nodes during transmission. We successfully transmit 100-GHz-grid, 20 channel single-carrier 440-Gb/s super-Nyquist 9-QAM-like signal over 3600-km ultralarge effective-area fiber (ULAF) at a high net SE of 4 b/s/Hz (after excluding the 7% hard-decision FEC overhead). The highly filtering tolerant performance of the 9-QAM liked super-Nyquist signal is also experimentally demonstrated. Using this scheme, we then successfully transmit ten channel 440-Gb/s signal over 3000-km ULAF and ten cascaded 100-GHz-grid ROADMs based on the 110-GBaud QPSK. Such signal is coherently detected and processed after a real-time oscilloscope at 160-GSa/s sampling rate with 65-GHz bandwidth.

High Symbol Rate Coherent Optical Transmission Systems: 80 and 107 Gbaud

We demonstrate high speed optical transmission systems using digital coherent detection at all-electronically multiplexed symbol rates of 80 and 107 Gbaud. At 107 Gbaud, we demonstrate a single-carrier polarization division multiplexed quadrature phase shift keyed (PDM-QPSK) line rate of 428 Gb/s. At 80 Gbaud, we achieve a single-carrier line rate of 640 Gb/s using PDM 16-ary quadrature amplitude modulation (16-QAM). Using two optical subcarriers, we demonstrate a 1-Tb/s optical interface and conduct long-haul wavelength-division multiplexed (WDM) transmission on a 200-GHz grid over 3200 km of ultra-large effective area fiber.

Nonlinearity Compensation of 224 Gb/s Dual-Polarization 16-QAM Transmission Over 2700 km

Long-haul transmission for distances greater than 2000 km is investigated for a 224 Gb/s dual-polarization 16-ary quadrature-amplitude-modulation signal, using ultralarge effective area fiber with span lengths of 75.5 km and distributed Raman amplification. By using nonlinear compensation (NLC) based on the low-pass filter (LPF) assisted digital back propagation (DBP) algorithm, a transmission distance of 2700 km is demonstrated with moderate complexity (0.25 backpropagation steps/span) and good robustness to deviation of the algorithm parameters from their optimum values. Compared to the standard DBP algorithm, the LPF assisted DBP algorithm can allow a reduction in the number of NLC steps/span, but with an increased computational complexity for each step. The two DBP algorithms are compared in terms of the number of real multiplications per bit, thus allowing the algorithm with lower complexity to be determined for a given level of performance.

Experimental investigation of 84-Gb/s and 112-Gb/s polarization-switched quadrature phase-shift keying signals

We experimentally investigate 28-GBd (84-Gb/s) and 37.3-GBd (112-Gb/s) polarization-switched quadrature phase-shift keying (PS-QPSK) signals. In single-channel transmission experiments over up to 12500 km ultra large effective area fiber, we compare their performance to that of polarization-division multiplexing quadrature phase-shift keying (PDM-QPSK) signals at the same bit rates. The experimental results show that PS-QPSK not only benefits from its better sensitivity but also offers an increased tolerance to intra-channel nonlinearities.

8 $\times$ 448-Gb/s WDM Transmission of 56-GBd PDM 16-QAM OTDM Signals Over 250-km Ultralarge Effective Area Fiber

An 8 × 448-Gb/s polarization-division-multiplexing 16-ary quadrature amplitude modulation wavelength-division multiplexing signal with 4-b/s/Hz spectral efficiency is generated using optical time-division multiplexing and real-time field-programmable gate array-based generation of four-level in-phase and quadrature modulator driving signals. Transmission performance over 250-km ultralarge effective area fiber with erbium-doped fiber amplifier-only amplification is investigated.