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.
The potential role of multicore fibers (MCFs) in submarine cable systems is investigated in the context of electrical power and physical fiber count limitations. We compare the maximum cable capacity ...possible for cables using MCFs with 2, 3, and 4 cores to that of cables built with single-core fibers (SCFs). The comparisons are made based on ideal Shannon capacity, constant output power amplifiers, and individual amplification of MCF cores. MCFs have nominally uncoupled cores for which core-to-core crosstalk is a system impairment. We examine the relative cost/bit of systems built with MCFs and SCFs when designed for maximum capacity, and when designed for minimum cost/bit operation. The relative capacity of cables with MCFs depends strongly on the number of fibers able to be physically accommodated and is greatest when the fiber count number is relatively small. We find only small differences in the relative capacities of MCFs with 2-4 cores and that any advantage over SCF systems can be eroded with minimum signal-to-noise ratio (SNR) requirements above the theoretical level near 0 dB maximizing cable capacity. The cost/bit of MCF cable systems is determined to be higher than that of SCF systems when maximum cable capacity is the design goal.
We analyze the potential suitability or strength of arguments for the application of multicore optical fibers in high capacity submarine cable systems via transmission and techno-economic modeling. ...We consider hypothetical multicore fibers (MCFs) with 2-4 weakly coupled cores and compare capacity and cost/bit against conventional single-core fibers (SCFs). The analysis is performed in the context of a trans-Atlantic link length system and we evaluate the relative fiber performance with three different, but related, system design approaches. Two SCF coating diameters are assessed in terms of how this parameter affects the cost/bit through fiber density in submarine cables and resulting cable cost. We find that MCFs may enable higher cable capacity when fiber pair limits are imposed, but likely not at lower cost/bit unless optimistic and best case assumptions are made with respect to MCF relative fiber cost. We also find that reduced diameter SCFs can deliver much of the density and cable cost savings that motivates interest in MCF without the challenges of a new eco-system as required by MCF. However, MCF may enable the design of the largest cable capacities such as 1 Pb/s or more that might not be attainable with SCFs without significant cable changes.
We assess the potential applicability and performance of multicore fibers (MCFs) against conventional single-core fibers (SCFs) in submarine transmission systems. In particular, we assume 4-core MCFs ...with nominally uncoupled cores and separate amplification of each MCF core with conventional erbium doped fiber amplifiers (EDFAs) using fan-in/fan-out (FI/FO) devices in the repeaters. We examine the effects of the number of physical fibers accommodated in the cable design, MCF and FI/FO crosstalk, FI/FO loss, span length, transceiver implementation penalty, and minimum required signal-to-noise ratio (SNR). The relative cable capacities offered by the MCF and SCF systems are evaluated under the different conditions. Then the relative cost/capacity for systems built with the two types of fiber are calculated using a system cost model for two conditions: 1) with maximum cable capacity and 2) for minimum overall cost/capacity. The potential role of multicore fibers (MCFs) in submarine cable systems is investigated in the context of electrical power limitations and physical fiber count limitations. Cable capacities are estimated based on ideal Shannon-limited capacity unless a transceiver implementation penalty, or gap-to-Shannon capacity, is applied. The systems are modeled assuming constant output power amplifiers as are commonly deployed in submarine systems. We find that MCFs offer the greatest cable capacity increase for low fiber count cables, but that the cost/capacity can be significantly higher. When minimization of cost/capacity is the design goal, MCF systems remain higher in this metric than SCF systems, while enabling only a small capacity increase at best.
We model and examine various amplification options for trans-oceanic repeatered submarine systems using multicore fiber (MCF) transmission in the context of relative cable capacity and relative ...system cost/bit. First, we compare the optical performance of various configurations of parallel standard single-core erbium-doped fiber amplifiers (SC-EDFAs) and multicore erbium-doped fiber amplifiers (MC-EDFAs), including both the C/L-bands and core/cladding pump designs. Key amplifier parameters governing expected capacity and cost/bit performance include noise figure, amplifier bandwidth, relative electrical-to-optical conversion efficiency, and relative amplifier cost. We make our best estimates of these parameters through modeling, analysis, and component cost estimates and assess the sensitivity of the results to the nominal values. We find that MC-EDFAs using either core- or cladding-pumping might offer lower cost/bit than parallel SC-EDFAs but cladding-pumping may reduce cable capacities due to the higher noise figure and potentially smaller amplifier bandwidth.
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.
In this article we describe an analytical model for estimating performance degradations caused by non-ideal transponder implementation for coherent modulation formats based on parametric fitting of ...back to back measurements. We discuss in detail several reasons for implementation penalties (IP) such as noise in the transmitter and the receiver, non-ideal filtering, and quantization in the analog-to-digital converter, and how the fitting parameters depend on these penalties. We consider how to combine the IP model and the Gaussian noise (GN) model of nonlinear propagation which includes Amplified Spontaneous Emission (ASE) and Nonlinear Interference (NLI) noise impacts. We modify the Signal to Noise Ratio (SNR) expression of the GN model to include any performance impairments from a non-ideal transponder and additional link components apart from the transponder. In this article we consider transponders based on 16QAM and 2ASK/4PSK-8QAM modulation formats. Then we compare the modeling results obtained with the IP and GN models with experimental data for erbium doped fiber amplifier (EDFA) and Raman-assisted transmission systems. We find that this modeling approach demonstrates good agreement experiment data.
Space Division Multiplexing using multicore optical fibers (MCF) is emerging as a promising technology for achieving capacity in excess of 1 Pb/s for submarine transmission systems. In this paper, we ...discuss the key MCF design considerations that result in transmission performance comparable to a single core fiber in submarine transmission systems. Based on these considerations, uncoupled 2-core multicore fibers having two different core-designs were designed with Effective Area of 112 μm 2 at 1550 nm. These designs were fabricated and record attenuation of 0.1444 dB/km and 0.1449 dB/km are reported for lowest attenuation core for each design, with attenuation of 0.1457 dB/km and 0.1455 dB/km at 1550 nm. This was enabled by using silica-core technology, along with improvements in core-processing and mitigation of attenuation contributors in the fiber manufacturing, including optimization of the draw conditions. Sensitivity of fiber attenuation (including radiation loss to high index coating) and copropagating and counterpropagating crosstalk to inter-core distance is studied and reported. Heterogeneous core MCF designs are evaluated for achieving good crosstalk performance even in cables where the bend radius encountered by the fiber is significantly larger than the bend radius on a shipping spool. Heterogeneous core MCFs where different core radius is used for core identification are also attractive for elimination of marker cores.
This letter demonstrates unrepeatered real-time transmission of 200 Gb/s (5 bit per symbol modulation format, 56.8 GBaud) signal over terrestrial 520 km single-span fiber link. This was achieved ...using ultra low-loss fibers with large effective area, ROPAs with dedicated fibers, and distributed Raman amplifiers with co- and counter-propagating pumps.
Coherent detection with receiver-based DSP has recently enabled the mitigation of fiber nonlinear effects. We investigate the performance benefits available from the backpropagation algorithm for ...polarization division multiplexed quadrature amplitude phase-shift keying (PDM-QPSK) and 16-state quadrature amplitude modulation (PDM-QAM16). The performance of the receiver using a digital backpropagation algorithm with varying nonlinear step size is characterized to determine an upper bound on the suppression of intrachannel nonlinearities in a single-channel system. The results show that for the system under investigation PDM-QPSK and PDM-QAM16 have maximum step sizes for optimal performance of 160 and 80 km, respectively. Whilst the optimal launch power is increased by 2 and 2.5 dB for PDM-QPSK and PDM-QAM16, respectively, the Q-factor is correspondingly increased by 1.6 and 1 dB, highlighting the importance of studying nonlinear compensation for higher level modulation formats.
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