Ana M. Rocha

Detection of Fiber Fuse Effect Using FBG Sensors

In this paper, we propose a new technique to detect the presence of the fiber fuse effect propagation. The implemented technique consists on the utilization of two fiber Bragg gratings (FBGs) as temperature sensors in order to detect the transit of the thermal wave associated with the fuse effect. The developed technique was used to determine the fuse propagation velocity in single mode fibers as function of the injected optical pump power, yielding a direct proportionality constant value of 0.106 ± 0.028 ms-1W-1.

Traveling Solutions of the Fuse Effect in Optical Fibers

In this paper, we reduce a partial differential equation that models the optical fiber fuse to an ordinary differential equation (ODE) using a traveling variable. This similarity reduction neglects the radiation loss term; however, the obtained fuse speeds are in good agreement with the ones obtained with the full propagation equation. The ODE results reveal the dependence of the fuse speed with the thermal parameters of silica and with the optical power density. We have also combined those results with experimental ones in order to adjust fiber absorption parameters.

Evaluation of the fuse effect propagation in networks infrastructures with different types of fibers

The evaluation of the fuse effect propagation in fiber networks is analyzed. We show a relation between the void interval, the power density and the fused effect velocity for different types of optical fibers.

Threshold power of fiber fuse effect for different types of optical fiber

In this work we measured the threshold power level for the fiber fuse effect ignition and propagation for different types of optical fibers. We verified that the threshold power is not proportional to the fiber mode field diameter.

Thermal Effects in Optical Fibres

Optical fibres are essential components in the modern telecommunication scenario. From the first works dealing with the optimization of optical fibres transmission characteristics to accommodate long distance data transmission, realized by Charles Kao (Nobel Prize of Physics in 2009), until the actual optical fibre communication networks, a long way was paved. The developments introduced in the optical communication systems have been focused in 3 main objectives: increase of the propagation distance, increase of the transmission capacity (bitrate) and reduction of the deployment and operation costs. The achievement of these objectives was only possible due to several technological breakthroughs, such as the development of optical amplifiers and the introduction of wavelength multiplexing techniques. However, the consequence of those developments was the increase of the total optical power propagating along the fibres. Moreover, in the last years, the evolution of the optical networks has been toward the objective of deploying the fibre link end directly to the subscribers home (FTTH – fibre to the home). Thus, the conjugation of high power propagation and tight bending, resulting from the actual FTTH infrastructures, is responsible for fibre lifetime reduction, mainly caused by the local increase of the coating temperature. This effect can lead to the rupture of the fibre or to the fibre fuse effect ignition with the consequent destruction of the optical fibre along kilometres. In this work, we analyze the thermal effects occurring in optical fibres, such as the coating heating due to high power propagation in bent fibres and the fibre fuse effect. We describe the actual state of the art of these phenomena and our contribution to the subject, which consists on both experimental and numerical simulation results.

Simulation of fiber fuse effect propagation

In this work, we present the simulation results of the fiber fuse effect propagation, using a one-space-dimensional model. This approach has the advantage of reducing the simulation time. The obtained simulated results are in agreement the experimental ones.

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.

Effect of bending in SMF fibers under high power

In this work we investigate the coating damages in optical fibers under the simultaneous effects of high optical power and tight bending. The power losses and coating heating imposed by the high power propagation have been measured for a SMF fiber. We have implemented a theoretical thermal model for the fiber bend and the minimum safety bend diameter has been established.

Optical fiber bending limits for optical fiber infraestructures

In this work the high power propagation in tight bent fibers was studied. The signal losses and the temperature increase have been experimental measured for single mode optical fibers (SMF) as function of the bending diameter. These results were used to propose an approach to limit the bending diameter, as a function of the injected power, in order to maintain the operational condition bellow the safety limit.

Switching in multicore fibers using flexural acoustic waves.

We propose an in-line wavelength selective core switch for multicore fiber (MCF) transmission systems, based on the acousto-optic effect. A theoretical model addressing the interaction between flexural acoustic waves and the optical signal in MCFs is developed. We show that an optical signal propagating in a particular core can be switched to any other core or distributed over all the cores. By tuning the acoustic wave amplitude, we can adjust the amount of optical power transferred between the cores.