Routing in optical transport networks: Optimization of the static configuration of optical transport networks

Modern telecommunication networks are structured hierarchically. In the core network, the highest level, many flows from subnetworks are aggregated, resulting in high bandwidth traffic which has to be handled carefully. If optical transmission technology is applied, such networks are called optical transport networks.

Data flows in optical transport networks are transported along so-called lightpaths, ongoing optical connections between pairs of nodes. For their realization, many technical and operational restrictions must be taken into account. Among these, survivability of the connections is of special importance in the core network. Altogether, the planning of appropriate static lightpath configurations states a sophistical task for which we develop mathematical models and solution methods.

Description

In optical telecommunication networks, signals are transmitted as short light pulses on glass fibers which in comparison to electronic systems allow higher bit rates. Moreover, so-called Wavelength Division Multiplexing (WDM) allows to establish several optical channels in parallel with different wavelengths on the same fiber, thus multiplying the available channel number. Until recently, switching in the network nodes was done by converting the optical signal into electronic form and afterwards back to optics. These (first generation) optical networks are therefore also called point-to-point WDM networks. In second generation optical networks, Optical Cross-Connects (OXCs) make it possible to directly switch channels optically. This results in continuous optical connections using one or more fibers which are called lightpaths. They build an virtual layer which is the characteristic property of such (second generation) optical networks.

Project objective

Strategic network planning deals with the design of (optical) transport networks. For this, there is a need to develop mathematical methods to determine lightpath configurations for a given set of static demands such that the dimensioning of the required capacities is cost-efficient. A partial problem typical for optical networks consists of the assignment of wavelengths to the lightpaths in such a way that different lightpaths on the same fiber use different wavelengths. Moreover, the study of different survivability concepts is another important task. The dynamic (lightpath) configuration of optical networks with demands changing over time is studied in a parallel project (see Optimization of optical transport networks with dynamic routing).

Publications

Adrian Zymolka, Arie M. C. A. Koster, Roland Wessäly. Transparent Optical Network Design with Sparse Wavelength Conversion. In: Proc. of Optical Network Design & Modelling (ONDM 2003), pp. 61-80, Budapest, Hungary, 2003.
Arie M. C. A. Koster, Adrian Zymolka, Monika Jäger, Ralf Hülsermann, Christoph Gerlach. Demand-wise Shared Protection for Meshed Optical Networks. In: Proc. of Optical Network Design & Modelling (ONDM 2003), pp. 61-80, Budapest, Hungary, 2003.
Arie M. C. A. Koster, Adrian Zymolka. Minimum Converter Wavelength Assignment in All-Optical Networks. In: Proc. of Optical Network Design & Modelling (ONDM 2004), pp. 517-535, Ghent, Belgium, 2004.
Koster, A. M. C. A., Zymolka, A.. Provably Good Solutions for Wavelength Assignment in Optical Networks. In: Proceedings of ONDM 2005, pp. 335–345, Milan, Italy, 2005.
A. M. C. A. Koster, A. Zymolka, M. Jäger, R. Hülsermann. Demand-wise Shared Protection for Meshed Optical Networks. Journal of Network and Systems Management, 13(1):35–55, 2005.
Koster, A. M. C. A., Zymolka, A.. Linear Programming Lower Bounds for Minimum Converter Wavelength Assignment in Optical Networks. In: Proceedings of INOC 2005, pp. 44–51, Lissabon, Portugal, 2005.
Koster, A. M. C. A.. Wavelength Assignment in Multifiber WDM Networks. In: Proceedings of INOC 2005, pp. 60–66, Lissabon, Portugal, 2005.
Wessäly, R., Orlowski, S., Zymolka, A., Koster, A. M. C. A., Gruber, C.. Demand-wise Shared Protection revisited: A new model for survivable network design. In: Proceedings of INOC 2005, pp. 100–105, Lissabon, Portugal, 2005.
Gruber, C., Koster, A. M. C. A., Orlowski, S., Wessäly. A Computational Study for Demand-wise Shared Protection. In: Proceedings of DRCN 2005, pp. 421–428, Naples, Italy, 2005.