Sascha Vorbeck

Evolution of Terrestrial Optical System and Core Network Architecture

Optical systems and technologies have been radically changing the telecommunication networks for past 15 years; today wavelength division multiplexing (WDM) technology, optical amplifiers, and simple optical switching elements like optical add-drop multiplexers (OADMs) are used in the backbone networks of all operators worldwide. Optical systems nowadays provide the basis for cost-effective transmission of large amounts of bandwidth over the Internet, and will enable its future growth and the spreading of new applications and services. This paper summarizes the main trends in optical networking and investigates potential future application areas. Optical system technology has become so pervasive in network design that it needs to be considered in the context of provisioning new applications and services. Therefore, the analysis is not limited to the aspects of physical transmission, but also takes into account recent developments in integrated network design as well as network control and management. The following sections describe the key functionalities of future optical network architectures, and the key findings of the theoretical analysis are supported by the results of a field trial of advanced transmission technology

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.

Terabit transmission of high capacity multiband OFDM superchannels on field deployed single mode fiber

We demonstrate transmission of 5×253-Gb/s optical OFDM-superchannels in 100-GHz spacing over 454 km field deployed fibers, achieving a capacity of 1.16 Tb/s. In addition transmission of 398.5 Gb/s in one OFDM channel over the same distance is reported.

16 x 112 gb/s nrz-dqpsk lab experiments and wdm field trial over ultimate metro distances including high pmd fibers

A 16 × 112 Gb/s field transmission trial was successfully performed over legacy fiber infrastructure of Deutsche Telekom comprising partially high polarization mode dispersion (PMD) values of 8 ps. Using a commercial PMD compensator, transmission over high PMD with negligible penalty was achieved. Enabled by the maturity of 43 Gb/s components, a 112 Gb/s nonreturn to zero (NRZ) differential quadrature phase-shift keying modulation format for dense wavelength division multiplexing transmissions with good system margins of 5 dB over 450 km metro distances (3 dB over 764 km) was demonstrated. By using high baud rate of 56 Gbd, penalty-free transmission is performed when copropagating with either 10.7 Gb/s NRZ or 43 Gb/s phase-shaped binary transmission signal channels.

WDM field trial over 764 km SSMF with 16 × 112 Gb/s NRZ-DQPSK co-propagating with 10.7 Gb/s NRZ

A 16×112Gb/s field trial was performed at the Deutsche Telekom fiber infrastructure with partially high PMD. Using 56Gbaud NRZ-DQPSK, no penalty could be observed when co-propagating with a 10.7Gb/s NRZ. Robust Metro DWDM transmission with attractive carrier-grade margins is demonstrated.

100GEthernet for aggregation and transport networks

Due to the doubling of the internet traffic every twelve month and upgrading existing optical metro-, regio- and long haul transport networks, the migration from existing networks toward high speed optical networks with channel data rates up to 100 Gbit/s/λ is one of the most important questions today and in the near future. Current WDM Systems in photonic networks are commonly operated at linerates of 2.5 and 10 Gbit/s/λ and major carriers already started the deployment of 40 Gbit/s/λ services. Due to the inherent increase of the bandwidth per channel, limitations due to linear and non-linear transmission impairments become stronger resulting in a highly increased complexity of link engineering, potentially increasing the operational expenditures (OPEX). Researchers, system vendors and -operators focus on investigations, targeting the relaxation of constraints for 100 Gbit/s transmission to find the most efficient upgrade strategies. The approaches towards increased robustness against signal distortions are the transmission of the 100 Gbit/s data signals via multiple fibers, wavelength, subcarriers or the introduction of more advanced modulation formats. Different modulation schemes and reduced baud rates show strongly different optical WDM transmission characteristics. The choice of the appropriate format does not only depend on the technical requirements, but also on economical considerations as an increased transmitter- and receiver-complexity will drive the transponder price. This article presents investigations on different approaches for the upgrade of existing metro-/ regio and long haul transport networks. The robustness against the main degrading physical effects and economy of scale are considered for different mitigation strategies.

8×107 Gbit/s serial WDM field trial over 500 km SSMF

8×107Gbit/s DWDM transmission is achieved over a 500km field installed fibre link in the Deutsche Telekom network, indicating high link utilization of 1bit/s/Hz spectral efficiency, needed for Terabit/s network capacity, required in a mid-term timeframe.

Aggregation networks: Cost comparison of WDM ring vs. double star topology

Due to the increasing demand for higher transmission capacity, originated from upcoming Triple-Play services, network operators are forced to increase the transmission capacity in the backbone and aggregation networks and drive down the costs per bit/s. Many concepts have been presented, optimizing backbone network and increasing the network capacity by introducing higher data rates or channel count. In this paper we focus on aggregation network architectures investigating appropriate architectures for the aggregation of broadband services for an incumbent European network operator. These architectures have to be cost effective and ensure high service availability. These requirements can be met by either aggregating via star topology, using several stages of Ethernet aggregation nodes, by a ring topology using cost effective optical add/drop multiplexers (OADM), or furthermore a mixture of star and ring topologies. The right choice depends on the traffic load, the traffic forecast, distribution of the traffic matrix and underlying fiber graph.

Simulation and optimization of 100 Gbit/s single channel modulation formats

The performance of various modulation schemes for 100 Gbit/s single channel serial transmission is investigated by means of numerical simulations. Different ASK and PSK modulation formats are compared in terms of total system reach for a 10-9 BER requirement. RZ-DQPSK format with a 1,920 km reach, without FEC and the support of additional Raman amplification, outperforms all the other schemes including 10×10 Gbit/s NRZ DWDM inverse multiplexing.

Serial 100 Gbit/s PM-RZ-DQPSK transmission in the presence of perturbations from lower data rate neighboring channels

This paper investigates serial 100 Gbit/s PM-RZ-DQPSK transmission in the presence of perturbations from neighboring 10 Gbit/s NRZ, 40 Gbit/s RZ-DPSK, and 40 Gbit/s RZ-DQPSK DWDM channels. It addresses the need to outline upgrade paths of current hybrid DWDM systems equipped with 10 and 40 Gbit/s line cards towards 100 Gbit/s for remaining channels. A numerical simulation approach is used to evaluate the signal quality of the central probe for various DWDM channel constellations and power levels.