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Recently, space-division multiplexing (SDM) techniques using multi-core fiber (MCF) and few-mode fiber (FMF) have been introduced into optical fiber communication to increase transmission capacity. Two main types of optical fiber amplifiers based on the Erbiumdoped fiber (EDF) and the Raman effect have been developed to amplify signals in the MCF a...
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... of the ways to control MDG is to tailor the mode content of the pump as shown in Ref. [20]. The schematic and experimental setup of FM-EDFA is shown in Fig. 1. To generate the desired pump intensity profile, the pump source is split into N paths. Mode converters are used to transform the spatial mode of the pump source into the N spatial modes of the MMF. As shown in Fig. 1, free-space optics can be used for mode conversion method and phase plates are employed to convert modes between the ...
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... MDG is to tailor the mode content of the pump as shown in Ref. [20]. The schematic and experimental setup of FM-EDFA is shown in Fig. 1. To generate the desired pump intensity profile, the pump source is split into N paths. Mode converters are used to transform the spatial mode of the pump source into the N spatial modes of the MMF. As shown in Fig. 1, free-space optics can be used for mode conversion method and phase plates are employed to convert modes between the pump and ...
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... profile with a maximum gain variation of 3 dB across the full C-band was also obtained through optimizing active fiber refractive index profile [18]. Yung et al. later extended their work to demonstrate simultaneously amplification of about 20 dB for different spatial- polarization modes (LP x 11,a and LP y 11,b ) [19]. The FM- EDFA, as shown in Fig. 1 (b), was employed in a WDM mode-division multiplexed (MDM) transmission over 50 km of FMF ...
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Citations
... The vortex beam is a new type of beam with helical phase wavefront, and OAM modes with different topological charges are orthogonal in space, which can be used as independent channels. So the vortex beam can realize the multi-channel transmission of the information, which fundamentally improves the communication capacity of the free-space optical communication system [2] [3]. Therefore, the generation of high-quality vortex beams is a key issue in the research of orbital angular momentum (OAM) multiplexed communication system. ...
... Few mode fiber (FMF) transmission is currently subject to intense research of future mode division multiplexing (MDM) communication system to increase the transmission capacity and avoid the foreseen "capacity crunch" [1][2][3] . One such MDM method, orbital angular moment (OAM) multiplexing has seen its potential use in optical communications to enhance the transmission capacity and spectral efficiency in FMF transmission. ...
We experimentally demonstrate a chip to few mode fiber (FMF) transmission link with on-off-keying (OOK) signal. The device emits TM 01 and TE 01 vortex modes which propagate through a 1.1 km FMF with measured OSNR penalties less than 2 dB at a BER of 2e-3.
One of the most promising solutions to overcome the capacity limit of current optical fiber links is space-division multiplexing, which allows the transmission on various cores of multi-core fibers or modes of few-mode fibers. In order to realize such systems, suitable optical fiber amplifiers must be designed. In single mode fibers, Raman amplification has shown significant advantages over doped fiber amplifiers due to its low-noise and spectral flexibility. For these reasons, its use in next-generation space-division multiplexing transmission systems is being studied extensively. In this work, we propose a deep learning method that uses automatic differentiation to embed a complete few-mode Raman amplification model in the training process of a neural network to identify the optimal pump wavelengths and power allocation scheme to design both flat and tilted gain profiles. Compared to other machine learning methods, the proposed technique allows to train the neural network on ideal gain profiles, removing the need to compute a dataset that accurately covers the space of Raman gains we are interested in. The ability to directly target a selected region of the space of possible gains allows the method to be easily generalized to any type of Raman gain profiles, while also being more robust when increasing the number of pumps, modes, and the amplification bandwidth. This approach is tested on a 70 km long 4-mode fiber transmitting over the C+L band with various numbers of Raman pumps in the counter-propagating scheme, targeting gain profiles with an average gain in the interval from 5 dB to 15 dB and total tilt in the interval from —1.425 dB to 1.425 dB. We achieve wavelength- and mode-dependent gain fluctuations lower than 0.04 dB and 0.02 dB per dB of gain, respectively.
The chapter provides a discussion of optical fiber amplifiers and through three sections provides a detailed treatment of three types of optical fiber amplifiers, erbium doped fiber amplifiers (EDFA), Raman amplifiers, and parametric amplifiers. Each section comprises the fundamentals including the basic physics and relevant in-depth theoretical modeling, amplifiers characteristics and performance data as a function of specific operation parameters. Typical applications in fiber optic communication systems and the improvement achievable through the use of fiber amplifiers are illustrated.
A higher order Raman amplifier model that take random mode coupling into account is presented. Mode dependent gain and signal power fluctuations at the output of the higher order mode Raman amplifier are discussed.
We demonstrate the differences in the excited state transmission (EST) for different modes in 8 μm core diameter, Er³⁺- doped silica fiber. The S² (Spatially and Spectrally resolved) imaging method was used to determine the modal composition of the transmitted beam and to analyze the group delays of the higher order modes. We register the up-converted emission under two beam excitation (980 nm + 850 nm or 790 nm) and propose the numerical model for the anti-Stokes emission analysis. Taking additionally into account the interference of the beating fiber modes, one can expect the inhomogeneous spatial distribution of the excited ions. This was predicted by numerical calculations. The obtained results have been confirmed by taking photo of the up-converted emission as seen from the side of the fiber.
