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▲ [14p-2D-17] Trench-assisted annulus core EDFA for gain equalization of six mode groups
Keywords:optical fiber
Space Division Multiplexing (SDM) is an emerging technology which could resolve the issue of capacity crunch. In few mode fiber (FMF) scheme, orthogonal modes including degeneracy and polarization of fiber carry information data independently. The few mode erbium doped fiber amplifier (FM-EDFA) is key component for the development of FMF based SDM Optical communication system.
We propose the trench-assisted annulus core EDFA which could provide more than 20 dB gain and less than 0.8 dB DMG for six mode groups. The fiber consists of central core, graded index annulus core sandwiched between two trenches and a cladding. The central core and cladding is made of pure silica. The trenches are made of F-doped silica and the graded-index annulus core is made of Ge-doped silica. The purpose of trenches is to enhance the power confinement of signal mode groups of the EDF in the annulus core, which is doped with Er+3 ions and works as the amplifying core. Mode profiles of fiber and their effective indices have been calculated using the transfer matrix method. The parameters are optimized such that the effective index difference of the adjacent modes is greater than 2.7×10-4 which is sufficient to avoid mode coupling due to micro-bending.
The six mode groups of FM-EDF LP01, LP11, LP21, LP31, LP41 and LP51 with even and odd orientations and two polarizations each, form 22 SDM channels. The input signal power in each orientation and polarization of signal mode groups has been chosen as 30 µW. The gains of FM-EDFA have been calculated using fundamental mode pumping. The trenches help in increasing power confinement in annulus core and hence help in minimizing the DMG.
The proposed trench-assisted annulus core EDFA provides more power confinement in doped region and enables to achieve more than 20 dB amplification of six mode groups with very low DMG using fundamental mode pumping. The proposed FM-EDFA would be useful in SDM optical communication system.
We propose the trench-assisted annulus core EDFA which could provide more than 20 dB gain and less than 0.8 dB DMG for six mode groups. The fiber consists of central core, graded index annulus core sandwiched between two trenches and a cladding. The central core and cladding is made of pure silica. The trenches are made of F-doped silica and the graded-index annulus core is made of Ge-doped silica. The purpose of trenches is to enhance the power confinement of signal mode groups of the EDF in the annulus core, which is doped with Er+3 ions and works as the amplifying core. Mode profiles of fiber and their effective indices have been calculated using the transfer matrix method. The parameters are optimized such that the effective index difference of the adjacent modes is greater than 2.7×10-4 which is sufficient to avoid mode coupling due to micro-bending.
The six mode groups of FM-EDF LP01, LP11, LP21, LP31, LP41 and LP51 with even and odd orientations and two polarizations each, form 22 SDM channels. The input signal power in each orientation and polarization of signal mode groups has been chosen as 30 µW. The gains of FM-EDFA have been calculated using fundamental mode pumping. The trenches help in increasing power confinement in annulus core and hence help in minimizing the DMG.
The proposed trench-assisted annulus core EDFA provides more power confinement in doped region and enables to achieve more than 20 dB amplification of six mode groups with very low DMG using fundamental mode pumping. The proposed FM-EDFA would be useful in SDM optical communication system.