Abstract
Lots of research efforts have been devoted to increase the transmission capacity in optical communications using orbital angular momentum (OAM) multiplexing. To enable long-haul OAM mode transmission, an in-line OAM fiber amplifier is desired. A ring-core fiber (RCF) is considered to be a preferable design for stable OAM mode propagation in the fiber. Here, we demonstrate an OAM fiber amplifier based on a fabricated ring-core erbium-doped fiber (RC-EDF). We characterize the performance of the RC-EDF-assisted OAM fiber amplifier and demonstrate its use in OAM multiplexing communications with OAM modes carrying quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM) signals. The amplification of two OAM modes over four wavelengths is demonstrated in a data-carrying OAM-division multiplexing and wavelength-division multiplexing system. The obtained results show favorable performance of the RC-EDF-assisted OAM fiber amplifier. These demonstrations may open up new perspectives for long-haul transmission in capacity scaling fiber-optic communications employing OAM modes.
Highlights
Light beams carrying orbital angular momentum (OAM) are characterized by a helical phase front of exp ðilθÞ [1], where l is the topological charge and θ is related to the azimuthal angle
The overall bit-error rate (BER) performance is dependent on the input signal power fed into the ring-core erbium-doped fiber (RC-erbium-doped fiber (EDF))-assisted OAM fiber amplifier which affects the output optical signalto-noise ratio (OSNR)
We have proposed and demonstrated an RCEDF-assisted OAM fiber amplifier, and its performance has been evaluated in a data-carrying OAM-division multiplexing (OAM-DM) and wavelength-division multiplexing (WDM) system
Summary
Light beams carrying orbital angular momentum (OAM) are characterized by a helical phase front of exp ðilθÞ [1], where l is the topological charge and θ is related to the azimuthal angle. Due to the helical phase structure, an OAM beam usually has a doughnut intensity profile with a phase singularity at the beam center. In the past few decades, optical communications employing OAM beams have attracted increasing attention from researchers [15,16,17,18,19,20,21]. The index profile of RCF is compatible with the donut-shaped OAM fields which is beneficial to suppress the unwanted radially higher-order modes. This simplifies the multiplexing and demultiplexing of the OAM modes and prevents crossing between effective indices of modes belonging to different families, allowing good mode separation. In the last decade, optimized design of RCFs has led to a significant increase in the number of Research
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