This work proposes a novel routing algorithm for transparent optical networks, which is based on the Ant Colony Optimization (ACO) meta-heuristics. It takes into consideration the Bit Error Rate (BER) of the connections that is derived from Amplified Spontaneous Emission (ASE) noise accumulated along the lightpath. We implement a Call Admission Control (CAC) to verify if a connection meets the following criteria: it has a BER below the maximum level, which is given by the sensitivity power at each component, and the total aggregate power on every network link is below a threshold, which is necessary to mitigate fiber non-linear effects. 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