Multimode Fiber Transmission Systems Research Articles

Neural Network Based Perturbation-Location Fiber Specklegram Sensing System Towards Applications With Limited Number of Training Samples

Deep learning methods such as convolutional neural networks (CNN) have been shown to be highly effective in complex nonlinear modeling or classification in multimode fiber transmission systems with intensity-only detection. However, such powers are often realized along with time-consuming training processes requiring large number of data samples, which may not be achievable in some practical implementations where only limited numbers of samples are available. In this paper, aiming at high-accuracy perturbation location in a multimode fiber specklegram sensing (FSS) system with small size training data set, we compare and analyze the performance of the CNN based FSS system using fibers under different conditions of mode coupling. We demonstrate that, by utilizing a ring core fiber (RCF) supporting a few weakly-coupled mode groups(MGs), high accuracy of around 100% in the classification of perturbation locations can be more easily achieved with faster convergence speed and fewer training samples, compared with FSS systems using conventional OM3 multimode fibers (MMFs) with hundreds of modes. Furthermore, owing to similar low-level characteristics extracted from the speckle-pattern images, the CNN exhibits good performance of transfer learning in a more practical RCF based FSS system with foot-stepping perturbations, confirming their good potential of extension into practical systems.

Hybrid WDM and Optical-CDMA over Multi-Mode Fiber Transmission System based on Optical Vortex

The optical vortex has recently attracted scholars to implement it in optical tweezers, microscopy, optical communications, quantum information processing, optical trapping, and laser machining. Optical vortex beam applied classically that can be transferred to the transverse amplitude of a heralded single-photon, and optical vortex possesses a helical wavefront and carries orbital angular momentum. In this study, Optical vortex is applied in optical-CDMA (optical code-division multiple-access) in conjunction with WDM (wavelength division multiplexing). This mechanism aims to increase the capacity and security in optical communication significantly. The implementation of Laguerre-Gaussian (LG) modes with optical vortex based on one dimension zero cross-correlation (ZCC) code shows that mode coupling reduces effectively. Consequently, a positive increase in channel performance and response. Accordingly, the LG modes based on the 1D-ZCC code are investigated and propagated over multi-mode fiber (MMF) based on an optical vortex, which also substantially reduces channel effects. Consequently, all these attributes combined will result in a hybrid WDM-Optical-CDMA with an optical vortex system over MMF.

基于光子灯笼的正交频分/模分复用IM-DD多模光纤传输系统

基于光子灯笼的正交频分/模分复用IM-DD多模光纤传输系统

Mode-dependent loss and gain: statistics and effect on mode-division multiplexing

In multimode fiber transmission systems, mode-dependent loss and gain (collectively referred to as MDL) pose fundamental performance limitations. In the regime of strong mode coupling, the statistics of MDL (expressed in decibels or log power gain units) can be described by the eigenvalue distribution of zero-trace Gaussian unitary ensemble in the small-MDL region that is expected to be of interest for practical long-haul transmission. Information-theoretic channel capacities of mode-division-multiplexed systems in the presence of MDL are studied, including average and outage capacities, with and without channel state information.

A Low Bending Loss Multimode Fiber Transmission System

This paper presents a high bend tolerant multimode optical fiber transmission system that is compatible with standard 50 microm graded index multimode fiber, in terms of achievable bandwidth and interconnectivity losses. When the 10 loops of the proposed bend resistive multimode fiber were wrapped around a cylinder of 1.5 mm radius, bend losses below -0.2 dB were achieved in case of experimentally produced fiber. Furthermore, when the section of the proposed bend resistive fiber was inserted between two sections of a standard 50 microm graded index multimode fiber, the total experimental measured loss proved to be below -0.15 dB.

Performance of High-Bitrate Multiple-Output Links Over Multimode Fiber With Intermodal Dispersion

We investigate novel transmission schemes over multimode fiber with multiple output detectors, providing more efficient utilization of the available spatial-temporal degrees of freedom of the system by combining coherent phase shift keying transmission with direct detection. We evaluate the statistics of the electrical charge generated by each detector, and its dependence on factors such as detector type, dimension and offset position. In the frequency-selective case, we reveal that temporal degrees of freedom resulting from nonoverlapping time pulses modify the decision variable statistics. We apply the ensuing model to propose a novel phase-modulated single input multiple output (SIMO) multimode fiber transmission system employing multiple detectors and multiple input multiple output (MIMO) space-time postdetection signal processing in order to mitigate the ISI stemming from intermodal dispersion.

Optical multiplexer for multimode fiber transmission systems

We have constructed and tested an optical multiplexer for use with multimode optical fibers. The device utilized a blazed plane reflection grating with a single GRIN‐rod lens, and was made from commercially available components. The wavelength spacing of the two channels was 27 nm, the insertion losses were ⩽2.4 dB, and the crosstalk was <−30 dB. Optimized versions of the device should be capable of providing at least four channels, with still lower insertion losses, in a rugged stable package 1–2 cm long by 2–4 mm in diameter.

Wavelength multiplexing in multimode optical fibers

The capacity of optical fiber transmission systems could be increased by multiplexing several signals at different wavelengths on each fiber. This paper considers various multiplex system designs that might be used with multimode fiber transmission systems. In each case, the required multiplexer size and material properties are calculated as functions of the basic parameters of the fiber system. For fiber systems of the type currently being tested, a compact (~2 mm in diameter x 1 cm long), rugged, three-channel multiplexer could be constructed using a blazed plane reflection grating and graded-refractive-index (GRIN) optics; and it appears that such devices could be produced using available materials and technology. Multiplexers using thick gratings or multilayer dielectric filters are larger, more complicated, and require materials at the very edge of available technology. Multiplexers using a multiple thick grating or hologram could be even smaller than the blazed-grating devices, but materials having the quired characteristics have not been demonstrated.

Optical multiplexer for multimode fiber transmission systems

We have constructed and tested an optical multiplexer for use with multimode optical fibers. The device utilized a blazed plane reflection grating with a single GRIN-rod lens, and was made from commercially available components. The wavelength spacing of the two channels was 27 nm, the insertion losses were ⩽2.4 dB, and the crosstalk was &amp;lt;−30 dB. Optimized versions of the device should be capable of providing at least four channels, with still lower insertion losses, in a rugged stable package 1–2 cm long by 2–4 mm in diameter.