T. Jackson, M. Lee, T. Hahn, W. Lin, R.S. Wolff, B. Mumey, and K. Repasky (USA)
Optical amplifiers, EDFAs, optical transients, WDM networks
Many erbium doped fiber amplifier (EDFA) based multi wavelength optical networks employ techniques such as burst-switching or packet switching where the time interval between traffic blocks can be long enough to induce EDFA optical power transients. The optical power transients are created by abrupt changes in the average input power to the EDFAs and can adversely affect the performance of the network. To mitigate the effects of EDFA optical power transients on optical networks, a method based on power shaping where heads and tails are joined to the beginning and end of a traffic block is proposed. A head (tail) gradually increases (decreases) the channel power by employing a pseudo-random bit sequence in which the probability of a “1” (“0”) increases from 0 to 0.5. Theoretical and experimental results both show that EDFA optical power transients can be significantly reduced with adequate shaping periods. For a linear shaping profile, drop transient deviation was reduced by .5dB while add transient deviation was reduced by .71dB. Power shaping is an economical means of suppressing EDFA optical power transients compared to other physical layer approaches that require the addition of specialized components and can be applied to EDFAs as well as other solid-state and Raman optical amplifiers.
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