Evolution of amplified spontaneous emission and characterization of an optimized two-mode EDFA system obtained from an extended analytical model

Abstract

An optimized two-mode erbium-doped fiber amplifier (2M-EDFA) system is proposed and evaluated in this paper. The Giles model of a single-mode EDFA is extended to multiple modes. Detailed mathematical analysis of the model indicates that a proper combination of an LP01 pump and LP11 pump can equalize the gain of the two modes. The results from mathematical calculations are validated with simulations based on the Runge–Kutta method numerically integrating first-order differential rate equations and propagation equations in the optical domain. Results show that an appropriate LP01 and LP11 pump power combination equalizes the gain of the two signal modes to a high value of 27.256 dB. The evolution of the forward-amplified spontaneous emission (ASE) in the designed 2M-EDFA system is investigated. The ASE ratio between the two modes is observed to remain within a factor of 2. The tolerance of the differential modal gain (DMG) with respect to the intrinsic parameters and external operating conditions for the designed 2M-EDFA system is also investigated. In the range of 1530–1560 nm, a modal gain of about 27 dB and ripple of about 0.21 dB are obtained for both modes. This enables transmission of a total of 60 spatial and spectral channels in this range with appropriate spacing. Finally, the immunity of the 2M-EDFA design to the effects of high concentration are investigated.