Linearized Semiconductor Optical Amplifiers impairments in dynamic optical networks A. López, J.J. Martínez, M.A. Losada, J. Mateo, I. Garcés Photonic Technologies Group i3A (University of Zaragoza), Walqa Technology Park, Cuarte (Huesca), Spain Abstract: Transmission impairments due to the cross-gain modulation effect in Linearized Semiconductor Optical Amplifiers have been evaluated in a dynamic network environment. Results demonstrate the arising of power penalizations when the amplifier is operated in saturation. Keywords: Dynamic networks, optical amplification, XGM Introduction Amplification is a key issue in next-generation optical networks even when short distances are to be covered. The transfer of routing and switching functionalities to the optical layer in such networks involves an increase of losses that need to be compensated for. Traditionally optical amplification has been performed by Erbium-doped fiber amplifiers (EDFAs). These show good performance in point-to-point links but introduce serious impairments when dealing with dynamic traffic [1]. On the other hand, semiconductor optical amplifiers (SOAs) are good candidates for amplification in cost-sensitive networks, such as those for access or metropolitan areas. The drawback of this kind of amplifiers is their non-linear behaviour which leads to the arising of interchannel crosstalk due to cross-gain modulation (XGM) effects. In the last years a linearized SOA (LOA) intended for amplification in optical networks has been proposed and commercialized [2]. LOAs have been demonstrated to be the ideal candidates for amplification purposes in cost- sensitive dynamic networks [3, 4]. However, degradations related to both add/drop events and amplification of multiple data channels are present. In this work we assess the power penalties associated with the operation of LOAs in WDM dynamic networks with add/drop events of channels, bursts or packets. For this purpose, we have measured the transmission performance at reception in terms of bit error rate (BER). 2. Experimental setup and results The experimental setup shown in Figure 1 emulates the operation of the LOA in a dynamic network environment. Two lasers (A, B) represent the data channels to be amplified. One of them is operated in continuous mode, while the other is operated in burst mode (CW and bursts in the Figure). The relative power between the CW and bursts channels is controlled by variable optical attenuators (VOA), so that the number of channels, bursts or packets added/dropped can be modified. The burst or packet length is set to 5 s and channel burst-mode operation is performed by an optical switch that truly adds or drops the bursts channel to/from the link. At the receiver end the CW channel is monitored and its BER measured. Data from VOA A VOA B laser B VOA Rx PIN det MZM A MZM B 3dB coupler BPF PPG BERT bursts CW 2x2 SW laser A LOA Pw mon Figure 1: Experimental setup for the assessment of LOA impairments in dynamic networks pulse pattern generator (PPG) is PRBS 2 15 -1 at 10 Gb/s and CW and bursts wavelengths are 1556.5 and 1558 nm. Optical powers considered are -7 dBm for CW channel and -7, -1, +5 dBm for bursts channel, associated with scenarios where 1, 4 and 16 bursts are added/dropped. 2.1 XGM by add/drop events Figure 2 shows BER curves for the above-described scenarios when only the XGM effect associated with add/drop events is taken into account (i.e. no data is conveyed by bursts channel, MZM A inactive in Figure 1). Figure 2: BER vs. received optical power as a function of the number of bursts added/dropped As it can be observed from the Figure, the number of channels, bursts or packets simultaneously added/dropped has a direct influence over the transmission performance in the amplified link. Power penalties (at 10 -6 BER) are 0.2 and 1.1 dB for the cases of 4 and 16 bursts add/drop with respect to the scenario with just 1 burst added/dropped. 2.2 XGM by data bit pattern In order to account for the XGM associated to the bit pattern of data conveyed by channels present in the link, 9781-4244-3856-3/09/$25.00 ©2009 IEEE