Probabilistically shaped PDM 4096-QAM transmission over up to 200 km of fiber using standard intradyne detection.

We demonstrate transmission of a probabilistically shaped polarization-division multiplexed 3-GBd 4096-QAM signal over up to 200 km of backward Raman amplified Corning® Vascade® EX2000 fiber. The 3-GBd signal with a root-raised-cosine roll-off of 0.01 has the potential to generate a spectral efficiency of 19.77 bit/s/Hz over 50 km of fiber.

Ultra-long unrepeatered transmission over 607 km at 100G and 632 km at 10G.

This paper reports record unrepeatered transmission results using forward and backward distributed Raman amplifications, large effective area ultra-low loss fiber and enhanced ROPAs with additional pumping fibers. Coherent 100 Gb/s with PM-QPSK modulation format and OOK 10G transmission are demonstrated over 607 km (97.2 dB) and 632 km (101.0 dB), respectively.

Unrepeatered Nyquist PDM-16QAM transmission over 364 km using Raman amplification and multi-channel digital back-propagation.

Transmission of a net 467-Gb/s PDM-16QAM Nyquist-spaced superchannel is reported with an intra-superchannel net spectral efficiency (SE) of 6.6 (b/s)/Hz, over 364-km SMF-28 ULL ultra-low loss optical fiber, enabled by bi-directional second-order Raman amplification and digital nonlinearity compensation. Multi-channel digital back-propagation (MC-DBP) was applied to compensate for nonlinear interference; an improvement of 2 dB in Q(2) factor was achieved when 70-GHz DBP bandwidth was applied, allowing an increase in span length of 37 km.

Record 500 km unrepeatered 1 Tbit/s (10 x 100 G) transmission over an ultra-low loss fiber.

In this work we experimentally demonstrate 1 Tbit/s (10 x 100 Gbit/s) unrepeatered transmission over 500.5 km using dual polarization quadrature phase shift keyed (DP-QPSK) format and real-time processing. Such ultra-long distance is enabled by the use of high-performance 100G DP-QPSK transponders (the required optical signal-to-noise ratio is 12 dB), ultra-low loss Corning SMF-28 ULL fiber (the average attenuation of the spools used in this experiment <0.160 dB/km), and optimization of remotely-pumped optical amplifiers. To the best of our knowledge this is the longest unrepeatered 100G-based 1 Tb/s WDM transmission distance reported to date.

150 x 120 Gb/s unrepeatered transmission over 409.6 km of large effective area fiber with commercial Raman DWDM system.

15 Tb/s unrepeatered transmission is achieved over 409.6 km (68.2 dB) of large effective area fiber using forward and backward distributed Raman amplification and a remotely-pumped erbium-doped optical amplifier. This result provides a record capacity-reach product of 6.14 Pb/s-km over a single fiber type. We also demonstrate channel growth from 10 to 150 waves within 61 nm amplification bandwidth.

Pulse-shaping versus digital backpropagation in 224Gbit/s PDM-16QAM transmission.

We investigate the transmission performance of 224Gbit/s polarization-division-multiplexed 16-state quadrature amplitude modulation (PDM-16QAM) for systems employing standard single mode fiber (SSMF) and erbium doped fiber amplifiers (EDFAs). We consider the effectiveness of return-to-zero (RZ) data pulses with varying duty cycles and digital backpropagation (DBP) in reducing nonlinear distortion in wavelength-division- multiplexed (WDM) links with 3, 5, 7 and 9 channels. Similar improvement in transmission reach of 18-25% was achieved either by pulse-carving at the transmitter or by DBP, yielding maximum transmission distances of up to 1760km for RZ-pulse-shapes and 1280km for NRZ.

Generation and long-haul transmission of polarization-switched QPSK at 42.9 Gb/s.

We demonstrate, for the first time, the generation and transmission of polarization-switched QPSK (PS-QPSK) signals at 42.9 Gb/s. Long-haul transmission of PS-QPSK is experimentally investigated in a recirculating loop and compared with transmission of dual-polarization QPSK (DP-QPSK) at 42.9 Gb/s per channel. A reduction in the required OSNR of 0.7 dB was found at a BER of 3.8 x 10(-3), resulting in an increase in maximum reach of more than 30% for a WDM system operating on a 50 GHz frequency grid. The maximum reach of 13640 km for WDM PS-QPSK is, to the best of our knowledge, the longest distance reported for 40 Gb/s WDM transmission, over an uncompensated link, with standard fiber and amplification.

Ultra-long-haul transmission of 7×42.9 Gbit/s PS-QPSK and PDM-BPSK.

We investigated ultra-long-haul transmission of polarization-switched QPSK (PS-QPSK) and polarization-division-multiplexed BPSK (PDM-BPSK) at 42.9 Gbit/s experimentally as well as by means of computer simulations. PDM-BPSK allowed transmission distances in excess of 14,040 km to be achieved, compared to 13,640 km for PS-QPSK. However, PS-QPSK offers a significant reduction in receiver complexity due to the lower symbol-rate.

A long-reach ultra-dense 10 Gbit/s WDM-PON using a digital coherent receiver.

We investigate the impact of channel spacing and nonlinear transmission over 120 km of standard single mode fiber for a 10 Gbit/s long-reach wavelength division multiplexed passive optical network (WDM-PON). We employed polarization division multiplexed quadrature phase shift keying (PDM-QPSK), which allowed data transmission at 3.125 GBaud, including a 25% overhead for forward error correction. To receive this spectrally efficient modulation format, a digital coherent receiver was employed, allowing for both frequency selectivity and an increased sensitivity of -45 dBm (25 photons/bit).We investigated a channel spacing as low as 5 GHz, for which the loss budget was 48.6 dB, increasing to 54.0 dB for a 50 GHz grid.

Characterization of long-haul 112Gbit/s PDM-QAM-16 transmission with and without digital nonlinearity compensation.

In this paper long-haul, single channel, polarization multiplexed 16-state quadrature amplitude modulation (PDM-QAM-16) transmission at 112 Gbit/s is investigated. Novel digital signal processing techniques are used to perform carrier phase estimation and symbol estimation, in combination with nonlinear digital backpropagation. The results obtained demonstrate that the use of digital nonlinear backpropagation increases the optimum launch power from -4 dBm to -1 dBm with a consequent increase in maximum reach from 1440 km to 2400 km, which is a record transmission distance for QAM-16 reported to date for an SMF link with EDFAs only. Furthermore, experimental measurements are supported by simulations, based on the link used in the experiment.

Experimental and numerical investigation of bit-wise phase-control OTDM transmission.

The impact of varying the phase relationship between adjacent OTDM channels is investigated in 80 Gbit/s transmission experimentally and numerically. A fiber-based coherent multiplexer is proposed for OTDM experiments - a phase shifter in the multiplexer and an external phase control circuit are used to set and maintain the phase difference. It is demonstrated that the optimum modulation format for maximum transmission distance strongly depends on pulse width, e.g. 120 degrees-RZ provides the best performance for pulse width of 8 ps; however, 90 degrees-RZ is advantageous when pulse width is reduced to 2 ps. Power in 'zero' bit slots and amplitude jitter are calculated to demonstrate that the performance variation is due to intra-channel four-wave mixing (IFWM) and different receiver sensitivity at back-to-back. We also show that phase modulation formats are sensitive to optical filtering.