Axel Klekamp

Quantifying spectrum, cost, and energy efficiency in fixed-grid and flex-grid networks [Invited]

Single and multi-carrier networks offering channel rates up to 400 Gb/s are evaluated under realistic reach parameters. It is found that efficient spectrum utilization and fine bit-rate granularity are essential to achieve cost and energy efficiency. Additionally, the break-even cost of flexible orthogonal frequency division multiplexing transponders is examined under different settings. The break-even cost of a flexible transponder corresponds to the cost value for which the total cost of the network is equal to that of the related single-line-rate network. The impact of the traffic load, the additional cost required for flex-grid optical cross connects, the cost of spectrum, as well as the cost of fixed-grid transponders is examined.

WDM transmission at 6-Tbit/s capacity over transatlantic distance, using 42.7-Gb/s differential phase-shift keying without pulse carver

We report the transmission of a record 6 Tbit/s capacity over 6120 km distance, involving channels modulated at 42.7-Gb/s bit-rate with differential phase-shift keying (DPSK). The performance is found similar to DPSK with subsequent pulse carving, namely RZ-DPSK.

Energy and Cost Efficiency of Adaptive and Mixed-Line-Rate IP Over DWDM Networks

Optimization of IP over DWDM networks is studied under constraints of cost (CAPEX) and energy consumption. Realistic IP traffic mapped to the optical DWDM which is expanded by a factor of 33 and 100 for a 10-year projection. General power and cost savings are taken into account for the 2020 scenarios. The DWDM core network (Germany 50) is analyzed for mixed-line-rate and reach/bandwidth adaptive scenarios; the latter is realized by optical orthogonal frequency division multiplexing (O-OFDM). Although the adaptive scenario shows to be more hardware efficient in terms of total number of transponders, the mixed-line-rate approach has slight advantages regarding cost and power. Moreover, a hierarchical network can show benefits in cost and power consumption compared to a network without restrictions in routing at high traffic loads.

Limits of Spectral Efficiency and Transmission Reach of Optical-OFDM Superchannels for Adaptive Networks

Limits of information spectral efficiency and transmission reach are analyzed by an optical orthogonal frequency- division- multiplexing (O-OFDM) dense wavelength- division- multiplexed (DWDM) system with bit rates of 10-600 Gb/s and quadrature phase-shift keying (QPSK) or m -quadrature amplitude modulation ( m-QAM). In addition, using the International Telecommunication Union (ITU) 50-GHz grid transmission of OFDM superchannels is studied.

Efficiency of adaptive and mixed-line-rate IP over DWDM networks regarding CAPEX and power consumption [Invited]

Optimization of IP over dense wavelength division multiplexing (DWDM) networks is studied under the constraints of energy and cost minimization. Realistic IP traffic mapped to the optical DWDM layer together with leased lines form the basic traffic load, which is expanded by factors of 33 and 100 for a 10-year projection. The DWDM core network (USA 66) is analyzed for mixed-line-rate (MLR) and reach/bandwidth-adaptive scenarios; the latter is realized by optical orthogonal frequency division multiplexing. Both scenarios are studied for flat and hierarchical network approaches and for different channel grid configurations. Network optimization due to capital expenditure and power consumption yield no significant differences for the IP layer regarding different scenarios (flat and hierarchical) or network approaches (MLR and adaptive network). In contrast, the wavelength division multiplexing layer shows benefits for the hierarchical network regarding cost and power and for the adaptive approach regarding the total number of transponders and fibers used. We show that elastic and MLR networks can achieve comparable performance levels using a 12.5 GHz grid. This article is a more detailed version of Klekamp et al., OFC, 2012, OTh3B.1, and extends previous studies in a German network [J. Lightwave Technol., vol. 30, p. 215, 2012], now comparing the techniques in a US network under different conditions regarding distances and topology.

Implementation of 64QAM at 42.66 GBaud using 1.5 samples per symbol DAC and demonstration of up to 300 km fiber transmission

We demonstrate 400Gbit/s data generation using 64QAM at 42.66 GBaud with a reduced oversampling ratio of 1.5 Sample/symbol including digital Nyquist filtering and spectral pre-emphasis. Even at 24% FEC overhead a successful transmission over 300 km ULAF has been shown.

Spectrum, cost and energy efficiency in fixed-grid and flex-grid networks

Single and multi-carrier networks offering channel rates up to 400Gb/s are evaluated under realistic reach parameters. It is found that efficient spectrum utilization and fine bit-rate granularity are essential to achieve cost and energy efficiency.

Transmission of 3×253-Gb/s OFDM-superchannels over 764 km field deployed single mode fibers

We demonstrate transmission of 3×253-Gb/s optical OFDM-superchannels in 100-GHz spacing co-propagating with 112-Gb/s NRZ-QPSK DWDM signals over 764 km field deployed fibers and compare system performance with and without inline DCF modules at the repeater amplifiers.

Experimental performance of 4D optimized constellation alternatives for PM-8QAM and PM-16QAM

Sensitivity and reach of soft-decoded PM-8QAM was improved by 1.2-dB and 35%, respectively, by moving to a 64 point 4D constellation and iterative decoding. Replacing PM-16QAM by 256 4D points led to 0.3-dB gain only.

5 × 50 Gb/s WDM transmission of 32 Gbaud DP-3-PSK over 36,000 km fiber with spatially coupled LDPC coding

A novel 3-PSK modulation format with 2 dB SNR gain over BPSK is implemented for ultra long haul transmission. With spatially coupled LDPC coding, 50% reach extension is achieved leading to 36.000 km transmission distance.