EDFA power transients and their effects in high speed optical networks

WDM networks can achieve significant enhancements in efficiency, flexibility and throughput by enabling wavelength-selective add/drop multiplexing (ADM) at user nodes. The wavelength insertion and deletion can be achieved by simply using appropriate wavelength multiplexers and demultiplexers. For achieving optimal performance, the cascaded EDFAs in add/drop networks are typically operated in the gain-saturation regime. Unfortunately, system performance is critically affected by the adding/dropping of WDM channels since all channels present are amplified simultaneously by each amplifier and must share the available saturated gain. Therefore, when channels are added or dropped, there will be a power transient in each of the remaining output channels. In general, system performance may be degraded: (i) by fiber nonlinearity when the channel powers are too high, and (ii) by a small receiver SNR when the channel, powers are too low. These transients occur on the time scale of microseconds to milliseconds, and could momentarily and significantly disrupt the system performance. In the work, an analysis is presented regarding fiber transmission penalties due to nonlinearity and amplified-spontaneous-emission (ASE) noise resulting from channel drop/add EDFA gain transients in a chain of 10-20 EDFAs with as many as 32 WDM channels