## Invited Session Mon.1.H 3002

#### Monday, 10:30 - 12:00 h, Room: H 3002

**Cluster 23: Telecommunications & networks** [...]

### Optical access networks

**Chair: Andreas Bley**

**Monday, 10:30 - 10:55 h, Room: H 3002, Talk 1**

**Cédric Hervet**

Robust optimization of optical fiber access networks deployments

**Coauthors: Matthieu Chardy, Marie-Christine Costa, Alain Faye, Stanislas Francfort**

**Abstract:**

Due to the recent increase in bandwidth requirements, telecommunication operators have to support it with the deployment of optical fiber networks through Fiber-To-The-Home Gigabit Passive Optical Network technology (FTTH GPON). One great challenge, in a deregulated context, is to design this network while not knowing who and where the future subscribers will be.

We focus on the problem of the robust optical fiber network deployment under demand uncertainty. A two-stage robust optimization model is proposed for this problem, as well as two robust solution methods extending classical results from Ben-Tal et al. and Babonneau et al. in order to be compliant with our uncertainty set.

**Monday, 11:00 - 11:25 h, Room: H 3002, Talk 2**

**Maria João Lopes**

Modelling the minimum cost PON access network design problem

**Coauthors: Amaro de Sousa, Luís Gouveia**

**Abstract:**

A PON is an optical access network connecting a Central Office to a set of terminals using optical splitters, installed on intermediate nodes, and optical fibres connecting all elements. In the network design problem, terminals are clustered in a minimum number of PONs and each PON has a maximum capacity in number of terminals. For each PON, we have to decide where to install splitters and how to connect all elements through optical fibres. In intermediate nodes, optical splitters of different PONs can co-exist.

There are costs associated with intermediate nodes, splitter types and fibre connections. We define the minimum cost design problem in the context of densely populated urban areas, proposing different ILP formulations and valid inequalities.

We address this problem in the general context where the number of splitting stages (and the splitting ratio on each stage) is an outcome of the optimization problem. Therefore, previous works became particular cases of this general network design problem.

We present computational results discussing the trade-off between the linear relaxation bounds and the runtime to achieve integer optimal solutions of the different models.

**Monday, 11:30 - 11:55 h, Room: H 3002, Talk 3**

**Olaf Maurer**

Lagrangian approaches to a two-level FTTX network design problem

**Coauthors: Andreas Bley, Ivana Ljubic**

**Abstract:**

We consider the design of a passive optical telecommunication access network,

where clients have to be connected to an intermediate level of distribution

points (DPs) and further on to some central offices (COs). Each client demands a given number of connections to its CO.

Passive optical splitters installed at the DPs allow several connections to share a single common connection between the DP and the CO. The objective is composed of fixed-charge costs for the use of facilities and hardware and linear costs which depend on the edge utilisation. We present two Lagrangean decomposition approaches that were improved with additional cuts and heuristics. The subproblems are solved using MILP techniques.

We report computational results and compare the efficiency of the Lagrangian approach to the direct approach via an integrated MILP model.