We study experimentally inter-channel crosstalk in double-pumped fiber optic parametric amplifiers constructed with conventional dispersion shifted fibers (DSFs) having different lengths (L-A = 13.8, L-B = 6.8, L-C = 4.3, and L-D = 0.8 km). For long fibers (L-A and L-B), eye diagram measurements in a 5-channel (100 GHz spacing) system show that in order to have negligible crosstalk, the output signal power per channel, P-s, should be limited to P-s < 0 dBm. By decreasing the fiber length (to L-C) it is possible to increase the output signal power and/or the number of signals while keeping the crosstalk on negligible levels. This trend was further confirmed by using a very short DSF (L-D = 0.8 km). Finally, we experimentally demonstrate that a general trend in 2P-FOPAs is that spurious FWM increases with the number of signal channels up to a given number of channels when a saturation regime is reached. This saturation of the generation of spurious tones occurs when the bandwidth occupied by the signals exceeds similar to 4-5 nm. (c) 2005 Elsevier B.V. All rights reserved.259194103