Ralph Leppla

Analysis of Crosstalk in Mixed 43 Gb/s RZ-DQPSK and 10.7 Gb/s DWDM Systems at 50 GHz Channel Spacing

In DWDM field experiments over 1047 km of standard fiber and in simulations we analyze the impact of crosstalk on a 43 Gb/s RZ-DQPSK channel both by 10.7 Gb/s OOK and 43 Gb/s RZ-DQPSK neighbors at 50 GHz channel spacing.

Field transmission of 8 /spl times/ 170 gb/s over high-loss SSMF link using third-order distributed Raman amplification

This paper reports on the field transmission of N/spl times/170-Gb/s over high-loss fiber links using third-order distributed Raman amplification (DRA) in a commercially operated network of Deutsche Telekom. It gives an overview of the key technologies applied for the realization of an 8 /spl times/ 170 Gb/s (1.28 Tb/s) dense wavelength division multiplexing (DWDM) system demonstrator and summarizes long-haul transmission experiments with terabit-per-second capacity over European fiber infrastructure. Third-order DRA enabled repeaterless transmission of 1 /spl times/ 170 Gb/s and 8 /spl times/ 170 Gb/s over links of 185- and 140-km field fiber, respectively. Including an additional 25 km of lumped standard single-mode fiber (SSMF) at the end of the span, a total loss of 61 and 44 dB, respectively, was bridged.

Field trials with channel bit rates of 160 Gbit/s

We present two 8/spl times/170 Gbit/s DWDM/OTDM (1.28 Tbit/s) field transmission experiment both over more than 400 km in commercially operated legacy networks of France Telecom (FT) and Deutsche Telekom (DT), respectively. Conventional EDFA based amplification schemes as well as distributed Raman amplified systems are tested. For different levels of polarization mode dispersion due to different quality of the installed fibre infrastructure adaptive PMD compensation and polarization de-multiplexing is tested.

Field transmission of 8/spl times/170 Gbit/s over high loss SSMF link using third order distributed Raman amplification

We report transmission of 1/spl times/170 Gbit/s over 61 dB and 8/spl times/170 Gbit/s over 44 dB attenuating links in the network of a major European network operator. Third order distributed Raman amplification established long span configurations bridging, respectively, 210 km and 165 km repeaterless span.

Modeling the time-variant channel of a PMD-affected WDM transmission system in respect to the temperature activity of dispersion compensating modules

The most common model used for PMD simulations visualizes the fiber as a concatenation of a large number of birefringent elements. This systems DGD has the same Maxwellian PDF for each frequency. By measurement of certain links it is shown that the PDF of the DGD is not equal for all of the frequency bands. This behavior could be traced back to the fact that fiber links consist of a certain number of stable buried sections, with nearly no PMD changes over weeks and months. These sections are connected by sections exposed to strong temperature variations, acting as polarization rotators. This new model of a fiber link is known as the hinge model. To characterize these hinges, the temperature dependent behavior of several DCM and patch cords commonly used in WDM systems have been investigated. Measurements showed that DCM are the most active hinges. They produce approximately a full rotation in Stokes space when heated 1°C. This rotation is both reproducible and reversible. An novel model of the analyzed DCM has been developed in Matlab, which is able to reproduce the described measured behavior in simulations. The frequency dependency of the DGDs PDF leads from overall systems outage probability to frequency selective outage probability. That means instead of having a system outage at a certain outage probability, outage probabilities are connected to a number of outage channels.

PMD tolerance of 8/spl times/170 Gbit/s field transmission experiment over 430 km SSMF with and without PMDC

We report on the impact of PMD in a 8/spl times/170 Gbit/s DWDM transmission experiment over 430 km field installed SSMF with and without PMD compensation. Stable performance is only achieved when using PMDC.

Tolerances and engineering rules for ultrahigh-speed transmission systems

The increasing demand for high capacity optical networks and the decreasing revenues per bit, combined with the given economy of scale for optical networks, forces the network operators to enhance the channel data rates as well as the channel numbers. Higher channel data rates result in a lower footprint, energy consumption and a lower complexity in network management and operation support systems, due to lower channel numbers. The enhancement of channel data rate in principle leads to a system tolerance reduction for chromatic dispersion, PMD and nonlinear effects. Furthermore higher order effects like dispersion slope and higher order polarization mode dispersion have to be taken into account. On the other hand the fast pulse broadening leads to a quasi linear behaviour of the systems, which relaxed some link design rules compared to 40 Gbit/s transmission. The lower tolerances can partially be mitigated by the implementation of more complex amplification schemes and compensators. The complexity of system design, accounting for less tolerances and adaptive compensating modules, is increased. We investigate theoretically and numerically the limiting physical effects and the impact on the signal performance, induced by chromatic dispersion, PMD and nonlinear impairments. We present derived engineering rules for all relevant effects and for various fiber types, based on channel data rates of 160 Gbit/s. These engineering rules enable design engineers to perform a fast system design and system degradation estimation, without time consuming full numerical simulations.

Optical channel model for system outage probability analysis based on PMD measurements of installed WDM links and its components

The opportunity to address special future client interfaces, i.e. IP router interfaces, and to reduce CapEx and OpEx in network domains with highly aggregated traffic are arguments for network operators to insist on the principal option to employ 40G in their backbone network. The fiber infrastructure of most network operators is adequate for a 40G introduction if parameters such as chromatic dispersion, fiber attenuation, nonlinear fiber effects are considered. Already the transition from 2.5Gbit/s to 10Gbit/s per channel the Polarization Modem Dispersion (PMD) for many operators proved to be a limiting factor. The heterogeneous distribution of PMD of cable and fiber segments enabled the operators to install 10 G systems by measuring and selecting the fibers. The migration towards 40G is limited mainly by the PMD of the fiber infrastructure. Again the heterogeneous distribution of PMD values means that only fraction of the possible links are feasible for 40G transmission. To extend the usable part of the infrastructure it is very important to define accurately the PMD limit which is acceptable for 40 G transmission.

Tolerances and engineering rules for performance estimation and system design in 160-Gbit/s transmission systems

Increasing demand for high transmission capacity and the decreasing revenues per bit, combined with the given economy of scale for optical networks, forces the network operators to enhance the channel data rates as well as the channel numbers. Higher channel data rates result in a lower footprint, energy consumption and a lower complexity in network management and operation support systems, due to lower channel numbers. In principle the enhancement of channel data rate leads to a reduction of system tolerance for chromatic dispersion, PMD and nonlinear effects. Furthermore higher order effects like dispersion slope and higher order polarization mode dispersion have to be taken into account. On the other hand the fast pulse broadening leads to a quasi linear behaviour of the systems, which relaxes the impact of fiber nonlinearities compared to 40 Gbit/s transmission. The lower tolerances can partially be mitigated by the implementation of compensators and more complex amplification schemes. Accounting for less tolerances, adaptive compensating modules and higher sophisticated amplification schemes, the complexity of system design is increased. We investigate theoretically and numerically the limiting physical effects and the impact on the signal performance, induced by chromatic dispersion and nonlinear impairments. We present derived engineering rules for all relevant effects and for various fiber types, based on channel data rates of 160 Gbit/s. These engineering rules enable design engineers to perform a fast system design and system degradation estimation, without time consuming full numerical simulations.

OTU3 Transmission with 43-Gbit/s-CS-RZ Signals over Installed G.652 Fiber Infrastructure and Accelerated PMD Outage Evaluation

A joint field trial on 40G transmission was conducted, where Deutsche Telekoms and NTTs R&D groups got involved. 43-Gbit/s/ch CS-RZ signals of the NTT G.709-OTN system were transmitted over selected high-PMD fiber links in DTs actual field environment. The advantage of CS-RZ modulation format was confirmed in comparison with conventional NRZ against all-order (first- and higher-order) PMD. Moreover, we introduced a new scheme for an accelerated determination of outage probability due to PMD that is adapted to practical field conditions in an operated fiber network with buried fibers and in-line operational optical elements.