T. Almeida

Analysis of power transfer on multicore fibers with long-period gratings.

The use of long-period gratings (LPGs) to distribute optical power from one core to all the cores in a multicore fiber (MCF) is theoretically analyzed. Simple analytical expressions that describe the mode powers evolution along the LPGs are derived from the coupled mode equations. This study demonstrated the power transfer between cores in a MCF promoted by identical LPGs. Moreover, with this technique, the pump signal can be distributed to all the cores without interfering with the transmission signals.

Admission Control in IP Multicast over Heterogeneous Access Networks

Network operators have been reluctant to deploy IP multicast services mainly due to the lack of native control over multicast groups. This lack of control does not only prevent operators from generating revenue from multicast-based services but also hinders regular network management. In this work we identified the network elements where admission control should be enforced for multicast sessions spawning over heterogeneous access networks. The architecture proposed uses existing AAA functionality to perform user identification and multicast session admission control. This control is made at the network layer with no protocol modifications. Three access networks were considered: xDSL, WiMAX and UMTS.

Strictly Non-Blocking All-Optical-Cross-Connect Demonstrator for WDM Wavelength Path Networks

In this paper, we assess the design and performances of a strictly non-blocking all-optical cross-connect demonstrator node for WDM wavelength path networks. The all-optical cross-connect (AOXC) prototype was experimentally tested in a small 2 x 2 WDM network with a STM-16 bit stream per channel. The single and cascaded performance of the AOXC was also simulated and its results were validated with the experimental ones.

Management of User Generated Multicast Sessions in IMS-Based Networks

Factors such as the growing number of multimedia terminals, the constant increase of bandwidth available per user, and the large number of existing data sharing applications, are compelling users to generate and distribute their own content to restricted groups of other users. In order to support such scenario, we present an IMS-based solution that enables content distribution, in multicast, to groups of users, where the source of the content is also an end-user. The proposed solution allows the source of content to configure the service, indicating a list of authorized receivers and both the transmission date and duration. Moreover, the proposed solution also allows the operator to manage the registered user profiles, to impose access control and to validate the configurations Passed QA by the users.

Tunable transparent and cost effective optical add-drop multiplexer based on fiber Bragg grating for DWDM networks

A wavelength tunable optical add drop multiplexer (OADM), giving access to all the wavelengths of the WDM signals provides more flexibility to satisfy reconfiguration requirements and to enhance network protection. We proposed a tunable OADM based on fiber Bragg gratings (FBG) where the dropped channel is removed by the used of a optical circulator and the added channel is incorporated to the wavelength combo by a passive optical coupler. This OADM is transparent by design and cost effective due to the use of just one optical circulator.

Selective wavelength transparent optical add-drop multiplexer based on fibre Bragg gratings

A configurable optical add-drop multiplexer (OADM) based on fibre Bragg gratings is reported. Dynamical selection of the add-drop or pass-through functionality is realised according to the control of an optical switch. OADM performances measurements in a 70 km, 3/spl times/2.5 Gb/s channel WDM network are reported.

A Fast Method for Launch Parameter Optimization in Long-Haul Dispersion-Managed Optical Links

A new, fast, and simple methodology for optimizing the launch parameters in a long-haul dispersion-managed links is proposed. With this new, simple method, it is possible to quickly predict both the optimum launch power and optimum predispersion compensation values, as opposed to methods based on the numerical integration of the nonlinear Schrodinger equation, which are complex and computationally demanding. This methodology uses the Gaussian noise model for optimal launch power prediction and it is complemented with an ideal predispersion prediction tool based on the analysis of the dispersion map. Realistic scenarios up to 2423.2 km of propagation were simulated and the results were compared with those of a commercial software tool. The results obtained by the simulations, in this paper, show that this methodology accurately predicts the correct launch parameters in few seconds, drastically reducing computational times when compared with conventional methodologies. A maximum mismatch of 0.9 dB in predicted optimal launch power between both methodologies was obtained, as well as very accurate predictions made the newly developed predispersion prediction tool, which calculates a predispersion value that optimizes the Q factor of the validation scenario.

Development of a 10 Gbit/s Optical Soliton Source

In this work we demonstrated the feasibility of a 10 Gbit/s optical soliton source based on direct modulation of a semiconductor laser. We also show that it is possible to reduce substantially the frequency chirp, induced by the direct modulation process, with a narrow optical filter. A peak power greater than 100 mW is achieved with an optical signal-to-noise ratio (OSNR) better than 39 dB. We measured the output timing jitter of the source and we show that its main contribution is due to the laser noise. We successfully test our source in a 45-km 5-channel WDM system. The stability and easy assembly of this type of source make them attractive for upgrading single or multichannel chromatic dispersion limited optical communication systems.