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

Abstract

━ We propose a new technique to minimize gain-transient time of wavelength-division-multiplexing (WDM) signals in erbium-doped fiber amplifier (EDFA) in channel add/drop networks. We have dramatically reduced the gain-transient time to less than 3μsec by applying, for the first time to our knowledge, a disturbance observer with a proportional/integral/ differential (PID) controller to the control of EDFA gain. The 3μsec gain-transient time is the fastest one ever reported and it is about less than 1.5% of 200μsec gaintransient time of commercially available EDFAs for WDM networks. We have demonstrated the superiority of the new technique by performing the simulation with a numerical modeling software package such as the Optsim TM . Inded Terms ━ Eribium-doped fiber amplifier (EDFA), wavelength-division-multipliexing (WDM), gain-transient time, disturbance observer, proportional/integral/ differential (PID) controller

Theoretical Design and Analysis of EDFA Gain Control System Based on Two-Level EDFA Model

“… is very large compared with 21  , so three-level model can be reduced to the following two-level model equation by singular perturbation method [10].…”

Theoretical Design and Analysis of EDFA Gain Control System Based on Two-Level EDFA Model

“…Generally, 32  is very large compared with 21  , so three-level model can be reduced to the following two-level model equation by singular perturbation method [10]. …”

“…The all-optical scheme has a drawback; the frequency of channel add/drop should be less than that of the relaxation oscillation frequency of EDFA, which is several hundred Hz. On the other hand, the mostly used one is an electrical scheme which controls the pump laser output electrically according to EDFA output signal level [9,10].…”

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

“…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 simplified two-level EDFA model was considered to design a gain controller and a disturbance observer (DOB) technique [8,9,10], and a proportional / integral (PI) controller was applied to the control of the EDFA gain in WDM add/drop networks.…”

“…However, the matching condition is not satisfied by the three-level model, so a new EDFA gain controller design methodology based on the three level model is necessary. In [5], a PID gain control algorithm considering the threelevel EDFA model was applied to a nominal control. Since a channel add / drop compensator was still designed using a DOB based on a simplified two-level model, theoretical analysis of asymptotic stability could not be provided rigorously.…”