Multimode fiber amplifier with tunable modal gain using a reconfigurable multimode pump

Abstract

We propose a method for controlling modal gain in a multimode Erbium-doped fiber amplifier (MM-EDFA) by tuning the mode content of a multimode pump. By adjusting the powers and orientation of input pump modes, modal dependent gain can be tuned over a large dynamic range. Performance impacts due to excitation of undesired pump modes, mode coupling and macro-bending loss within the erbium-doped fiber are also investigated. The MM-EDFA may potentially be a key element for long haul mode-division multiplexed transmission.

Few-mode EDFA Supporting 5 Spatial Modes with Reconfigurable Differential Modal Gain Control

“…It is however well known (and recently demonstrated in Ref [3]) that the HOMs generally experience higher propagation, bending and coupling losses and thus require higher gain for transmission over multiple fiber spans. Mode selective pumping has previously been shown to offer higher gains for the HOMs in a FM-EDFA supporting two mode groups [6], however in this implementation the DMG could not be accurately controlled over the full C-band with a gain flatness of better than 5dB and changes by as much as 2.5dB depending on the pump power and operating wavelength. Here we report a 5M-EDFA providing adjustable DMG obtained by using a mode-selective bi-directional pumping scheme in conjunction with an EDF with a specially tailored Er-doping profile.…”

Modal Gain Control in a Multimode Erbium Doped Fiber Amplifier Incorporating Ring Doping

“…Our FMF amplifier simulator is based on the rate and propagation equations dealing with multitransverse-spatial modes 4,5 . In this model, the following assumptions are made: (1) the EDFA is considered as a two-level system; (2) the erbium-doped fibers (EDFs) are weakly guided and the modes are well approximated by linearly polarized (LP) modes; (3) the fibers are uniform along the longitudinal direction and the mode coupling effects are negligible.…”

Tailored modal gain in a multi-mode erbium-doped fiber amplifier based on engineered ring doping profiles

“…Figure 1(a)] was met with promising early results: 20 dB gain with a differential modal gain (DMG) of less than 3 dB has been demonstrated for the LP 11 and LP 21 mode groups in [14] and for the LP 01 and LP 11 mode groups in [15], while 12.5 dB gain with 1 dB gain excursion between the LP 01 and LP 11 modes was demonstrated in [16]. The same method was recently extended to include a small doped core in the center of a doped ring MM-EDFA in which four signal modes (LP 01 , LP 11 , LP 21 , LP 02 ) were predicted to achieve gains over 20 dB using two pump modes (LP 01 and LP 41 ), although noise and modal coupling were neglected in the analysis [17].…”