Data Rewriting After Carrier Erasing by Ultra-Long SOA Napoleão S. Ribeiro 1* , André L. R. Cavalcante 1 , Cristiano M. Gallep 2 and Evandro Conforti 1 1 Department of Microwaves and Optics - FEEC, University of Campinas (UNICAMP), C.P. 6101, 13083-970 Campinas, SP, Brazil; 2 Division of Telecommunication Technology - FT, University of Campinas, 13484-370, Limeira/SP, Brazil * Corresponding author: nribeiro@dmo.fee.unicamp.br Abstract: Optical carrier erasing is demonstrated with evaluation of further remodulation up to 12.5Gbps. Small impairments achieved for all but the 7G-7G and 12.5G-12.5G cases, when spurious-pattern noise force higher penalties (respectively 2.3dB and 0.7dB). OCIS codes: (200.4560) Optical Data Processing; (250.5980) Semiconductor Optical Amplifier; (190.0190) Nonlinear optics. 1. Introduction The wavelength division multiplexing passive optical network (WDM-PON) with centralized light sources (CLS) has been considered an ultimate solution for the fiber-to-the-home (FTTH) structure implementation [1]. Many WDM-PON implementations use two wavelengths: one carrier for the upstream and another for the downstream signal [2]. However, the finite number of available channels may limit the system capacity, making the wavelength reuse approach an attractive candidate to provide power to the upstream channel - downstream carrier erasing and remodulation - with no additional wavelength required. Some techniques were proposed to implement the optical data erasing/rewriting, based on use of two modulators [3], semiconductor optical amplifier (SOA) with feed-forward gain control technique and optical modulator [4], SOA as eraser/modulator [2], reflective SOAs (RSOAs) [5], interferometric filter & RSOAs [6]. However, the erasing capacity presented is not substantial in many cases, even more when considering PRBS, AM signal with input ER greater than 8 dB, and/or when trying high bit rates (above 2.5 Gbps). The use of gain-saturated SOA to erasure optical data was proposed first in [7] and implemented in [5] using cascaded SOAs. The new data rewriter scheme used here was presented previously in ref.[8], were some erasing characterization was presented. The scheme is based on deep gain saturation of an ultra-long SOA (L Z = 8 mm), to erasure the downstream signal, and a local optical modulator, to rewrite data over the now upstream carrier. Here we present the impact of the erased-carrier spurious oscillations over the quality of the upstream signal, with BERT curves for different downstream and upstream bit-rates (up to 12.5Gbps) and varying the modulation extinction ratio (ER in , up to 12.4 dB) for the downstream channel. The rewritten carrier - the upstream - presented small BER penalties, lower than 1 dB when comparing with a clean (CW) original source and when varying the input bit-rates and negligible penalties when varying the ER in . A error-floor appear just for operation using both up- and downstream at 12.5 Gbps, tending to BER = 10 -9 ; even so, the erased/rewritten channel presents equal performance to that of a clean (CW) input up to BER = 10 -7 . 2. Experimental setup and results Fig. 1. Experimental setup - CW tunable laser; Mach-Zehnder amplitude modulator (mod); linear semiconductor optical amplifier (SOA); optical polarization controller (PC); Ultra-Long (UL)SOA; in detail, power spectra and eye-diagrams for the downstream (ex.7Gbps), the erased and the upstream (ex.12.5Gbps) carrier. The experimental setup is shown in Fig.1 – the downstream source formed by signal generator, CW laser and optical amplitude modulator (2 to 12.5 Gbps) operating in non-return to zero (NRZ) PRBS with variable extinction ratio. The chosen carrier wavelength (1565nm) is the optimal in this case, coinciding with the peak of the UL-SOA erased JWA42.pdf OSA/OFC/NFOEC 2011 JWA42.pdf