Power control strategies and network performance assessment for C+L+S multiband optical transport

Abstract

Spatial-division multiplexing (SDM) and band-division multiplexing (BDM) have emerged as solutions to expand the capacity of existing C-band wavelength-division multiplexing (WDM) optical systems and to deal with increasing traffic demands. An important difference between these two approaches is that BDM solutions enable data transmission over unused spectral bands of already-deployed optical fibers, whereas SDM solutions require the availability of additional fibers to replicate C-band WDM transmission. On the other hand, to properly design a multiband optical line system (OLS), the following fiber propagation effects have been taken into account in the analysis: (i) stimulated Raman scattering (SRS), which induces considerable power transfer among bands; (ii) frequency dependence of fiber parameters such as attenuation, dispersion, and nonlinear coefficients; and (iii) utilization of optical amplifiers with different doping materials, thus leading to different characteristics, e.g., in terms of noise figures. This work follows a two-step approach: First, we aim at maximizing and flattening the quality of transmission (QoT) when adding L- and -bands to a traditional WDM OLS where only the C-band is deployed. This is achieved by applying a multiband optimized optical power control for BDM upgrades, which consists of setting a pre-tilt and power offset in the line amplifiers, thus achieving a considerable increase in QoT, both in average value and flatness. Second, the SDM approach is used as a benchmark for the BDM approach by assessing network performance on three network topologies with different geographical footprints. We show that, with optical power properly optimized, BDM may enable an increase in network traffic, slightly less than an SDM upgrade but still comparable, without requiring additional fiber cables.

Benefits of counterpropagating Raman amplification for multiband optical networks

“…3. These NFs were obtained through experimental characterization of commercially available Erbium-doped fibre amplifiers (EDFA)s for the C-and L-bands [3] and from a benchtop Thulium-doped fibre amplifier (TDFA) for the S-band [22]. The optical amplifiers fully compensate for the loss of each channel, i.e., the gain ripple of the amplifiers perfectly compensate for the ISRS power transfer.…”

“…Indeed, using the launched power profile calculated by the local-optimization global-optimization (LOGO) strategy, it was shown in [2] that using 48 THz (a 10x factor in bandwidth increase) for data transmission could allow increasing the capacity of point-to-point links by about eight times, thus leading to a spectral efficiency reduction of about 20%. Even though selecting the launch power using the LOGO optimization strategy is not optimal for such wide-band systems [3], this early analysis stresses the importance of accurately estimating the capacity and cost of future MB systems to steer the development of the technology required to enable each transmission band.…”

“…In this case, proper launch power optimization is essential to deliver the highest capacity and fully exploit the benefit of MB transmission. However, the power optimization problem is non-convex in the presence of ISRS [9], and most publications have solved the optimization problem through explicit enumeration [14,15], iterative algorithms [16] or genetic algorithms [3,17].…”

“…For instance, in [10], it is shown that, with proper launch power optimization, the total throughput of a C+L-band system could be increased by 60% when adding the complete S-band. Moreover, the work reported in [3] suggests that the total allocated traffic increases almost 50% for a target blocking probability of 1% when adding only half of the S-band, which corresponds to a much higher average spectral efficiency.…”

Multi-Band Photonic Integrated Wavelength Selective Switch

“…MBT systems are already being deployed as C+L [4], [5], by capitalizing on the re-use of erbium-doped fiber amplifiers (EDFAs) also within the L-band. More recently, S+C+L-band systems started being subject of active research, from numerical studies [3], [6] that showed the potential of these three-band systems to triple the capacity when compared against C-band only, to experimental setups employing power optimization schemes [5], wideband semiconductor optical amplifiers (SOAs) [7], [8] and continuous bandwidth amplification and geometric shaping for record breaking data transmission [9]. As MBT systems gain commercial traction, solutions for, e.g., spectrum management and routing are required.…”