Few-mode Erbium-doped Fiber Amplifier Research Articles

Few-mode erbium-doped fiber amplifier with photonic lantern for pump spatial mode control.

We demonstrate a few-mode erbium-doped fiber amplifier employing a mode-selective photonic lantern for controlling the modal content of the pump light. Amplification of six spatial modes in a 5 m long erbium-doped fiber to ∼6.2 dBm average power is obtained while maintaining high modal fidelity. Through mode-selective forward pumping of the two degenerate LP21 modes operating at 976 nm, differential modal gains of <1 dB between all modes and signal gains of ∼16 dB at 1550 nm are achieved. In addition, low differential modal gain for near-full C-band operation is demonstrated.

Amplification sharing of non-degenerate modes in an elliptical-core few-mode erbium-doped fiber.

We report on the study of a possible first step integration of mode division multiplexed optical component for single-mode fiber networks. State-of-the-art on few-mode erbium-doped fiber amplifiers is used to integrate the amplification function in a single component, which is expected to save energy in comparison to parallelized active components. So as to limit the impact of modal cross-talk, an elliptical-core few-mode erbium-doped fiber has been used to assemble an amplifier sharing setup for different single mode fibers, using non-degenerate modes. With this simple setup, we show the level of performances that can be reached for cross-talk, gain, differential modal gain and losses and discuss the ways to improve them for a possible integration in a real network.

A Five-Mode Erbium-Doped Fiber Amplifier for Mode-Division Multiplexing Transmission

We describe a few-mode erbium-doped fiber amplifier with ring-doped erbium doping profile fiber and optimized optical setup amplifying LP01, LP11, and LP21 modes, simultaneously. Spectral and modal gain distribution is characterized as well as modal crosstalk. We study the gain evolution of every mode in several configurations, changing the input power or the number of injected modes. The gain is above 13 dB for all modes and its differential modal gain is lower than 5.7 dB across the whole C-band with a 3.5-m-long erbium-doped fiber when using a pump at 630 mW. As a proof of concept, we transmit up to five modes carrying each a PDM-QPSK signal at 32 Gbd through this amplifier.

Cladding pumped few-mode EDFA for mode division multiplexed transmission.

We experimentally demonstrate a few-mode erbium doped fiber amplifier (FM-EDFA) supporting 6 spatial modes with a cladding pumped architecture. Average modal gains are measured to be >20dB between 1534nm-1565nm with a differential modal gain of ~3dB among the mode groups and noise figures of 6-7dB. The cladding pumped FM-EDFA offers a cost effective alternative to core-pumped variant as low cost, high power multimode pumps can be used, and offers performance, scalability and simplicity to FM-EDFA design.

Optimization Algorithm Applied to the Design of Few-Mode Erbium Doped Fiber Amplifier for Modal and Spectral Gain Equalization

Gradient descent optimization algorithm is applied to design few-mode Er $^{3+}$ -doped fibers adapted to gain equalization over modes and wavelengths, for mode division multiplexing. Theoretical study is performed for fiber designs supporting six and ten spatial modes at signal wavelength. Flat gain is obtained by optimizing Er $^{3+}$ doping profile of a micro-structured core and modal composition of the pump beam.

Few-mode erbium-doped fiber amplifier design method based on the signal-pump overlap integral

Space-division multiplexing allows an increase of link capacity by using either multicore or single-core few-mode (FM) optical fibers. In the case of FM systems, each mode carries its own data stream and long-haul transmission can be hampered by the use of conventional erbium-doped fiber amplifiers (EDFAs), since because of distinct field profile configurations, each mode experiences a different value of optical gain. The role of the FM-EDFA designer, usually done by solving rate and propagation equations, is to define both the fiber cross-section and the pumping configuration to provide the best possible mode equalization of optical gain and noise figure. An optimization method is proposed here based on the definition of a figure of merit related to the equalization of the pump-mode signal overlap integral, significantly reducing computation time and allowing a multiobjective optimization approach. The results obtained were validated against the solution provided by the full set of rate and propagation equations and we conducted an FM-EDFA optimization case study. Our double-ring Er doping profile design requires a single 180-mW LP11 pump to provide a mean gain of 21.3 dB, within 0.6 dB of equalization for each of the four modes considered.

Reconfigurable Modal Gain Control of a Few-Mode EDFA Supporting Six Spatial Modes

We experimentally demonstrate an inline few-mode erbium doped fiber amplifier supporting six spatial modes with reconfigurable differential gain control and excellent gain flatness obtained through mode-selective bidirectional pumping of a custom fiber with a radially profiled erbium dopant distribution. A signal gain of >20 dB was obtained for all the guided modes with a differential modal gain <;2 dB and good gain flatness across the C-band.

Modeling and characterization of a few-mode EDFA supporting four mode groups for mode division multiplexing

Numerical and experimental study of a Few-Mode (FM) Erbium Doped Fiber Amplifier (EDFA) suitable for mode division multiplexing (MDM) is reported. Based on numerical simulations, a Few-Mode Erbium Doped Fiber (FM-EDF) has been designed to amplify four mode groups and to equally amplify LP11 and LP21 mode groups with gains greater than 20 dB and with a differential modal gain of less than 1 dB. Experimental results confirmed the simulations with a good concordance. This modal gain equalization is obtained by tailoring the erbium spatial distribution in the fiber core with a ring-shaped profile.