A gain-flattened two-stage EDFA for WDM optical networks with a fast link control channel

A Singular Perturbation-Like Approach to EDFA Gain Control Based on Observer Techniques

“…The energy level of EDFA is shown in Fig. 1 and the equations for the threelevel process are given as 3 32 3 3 1 ( ) …”

“…Since 3 A is stable for any positive numbers 1 k and 2 , k there exist positive definite symmetric matrices P and Q satisfying the following Lyapunov equation 3 3 .…”

“…It, however, has the drawback that the frequency of channel add/drops should be less than that of the relaxation oscillation frequency of the EDFA, which is several hundred hertz. On the other hand, the gain fluctuation due to channel add / drops can be effectively compensated for by controlling the pump laser output electrically according to the EDFA output signal level [3]. In the previous papers [4][5][6][7], we proposed a novel technique which minimizes the gaintransient time effectively under the assumption that the rate of Erbium ions at level 3 converges relatively fast to the desired equilibrium compared with the one at level 2.…”

A Novel Technique to Minimize Gain-Transient Time of WDM signals in EDFA

“…It seems to be an ideal method since it involves no electrical signal which may degrade the speed of whole system, however, for this method to operate properly, the frequency of channel add/drop should be less than that of relaxation oscillation of EDFA, which leaves not much room for system specifications. The other one controls the pump laser output electrically according to EDFA output signal level [3]. This is a generally accepted method in industry since it is simpler, cheaper and robuster.…”