A method is proposed for predicting the evolution of the power distribution along graded-index plastic optical fibers. This method is verified against our recently reported measurements. The strong influence of mode coupling on the power distribution is demonstrated on a specific graded-index plastic fiber to illustrate the influence of mode coupling in applications, such as data transmission, power delivery, and sensing systems.

We present 10-Gb/s transmission with a directly modulated laser (DML) avoiding inline dispersion compensating by electronic precompensation. To apply this technique of electronic dispersion precompensation to DMLs, a new approach based on artificial neural networks will be introduced. We realized a transmission of 190-km standard single-mode fiber in a laboratory experiment. Simulations show that compensation of up to 350 km can be achieved.

This paper reviews the application of the Volterra series expansion to fiber-optic communication systems and performance evaluation of dispersion maps. It is shown that under certain conditions periodically dispersion-managed multispan systems can be approximated by simple single-span systems with dispersion precompensation. This single-span approximation can help us to identify equivalent system configurations and estimate optimum system parameters. To set an example, the single-span model is employed to analyze transmission systems based on the return-to-zero on-off-keying modulation format and direct detection.

The structural properties of novel melt-spun polymer optical fibers (POFs) are investigated by small-angle X-ray scattering. The amorphous PMMA POFs were subjected to a rapid cooling in a water quench right after extrusion in order to obtain a radial refractive index profile. Four fiber samples were investigated with small-angle X-ray scattering (SAXS). The resulting distance-distribution functions obtained from the respective equatorial and meridional SAXS data exhibit a real-space correlation peak indicative of periodic cross-sectional and axial variations in the scattering density contrast. Simple model calculations demonstrate how the structural information contained particularly in the equatorial distance distribution function can be interpreted. The respective results are qualitatively verified for one of the fiber samples by comparison of the model curve with the measured SAXS data. Eventually, the study confirms that the cross-sectional variation of the (scattering-) density is the main reason for the formation of radial refractive-index profiles in the POFs.

A 3×3 textile integrated force-sensor array is presented that is based on the cross coupling of optical fibers and provides multi-touch capability. The force sensing relies on cross coupling between two fibers that are aligned orthogonally to each other. The actual coupling is improved by an increased contact area and higher scattering at the fiber crossing. A systematic analysis of different parameters is done for the driving and the sensing fiber, which involves materials, size, fabrication parameters as well as the cross-section shape. The results reveal that the combination of a rather stiff driving fiber and a flexible sensing fiber from elastomer (TPU) lead to the highest sensitivities in the range of 45.5 pW/N. The application of non-circular cross sections can improve the coupling efficiency by directing the sideemitted light better towards the sensing fiber. A trilobal-shaped driving fiber lead to an increase of 5 dBs, whereas the shaping of the sensing fiber improved the efficiency by another 7.5 dB.

Laboratory experiments on optical short range transmission with light-emiting diodes (LEDs), different lengths of step-index polymer optical fiber (SI-POF), and p-i-n-diode-based reception are performed. We compare multilevel pulse amplitude modulation with different spectral efficiencies with a particular focus on the impact of LED-based nonlinear signal impairments. A resonant cavity LED is used which emits a fiber-coupled power of −0.8 dBm at 650 nm. The impact of LED nonlinearities on the system power budget is evaluated, showing that compensation of these nonlinear signal distortions may noticeably increase the system power budget, even for 4-PAM. Applying a reduced-length Volterra-series-based post equalization, we report successful transmission of 5 Gb/s over 20 m of SI-POF, 2.25 Gb/s over 50 m, 1.1 Gb/s over 80 m, and 620 Mb/s over 100 m. To the best of our knowledge, the data rates obtained here set new record values using such an LED and SI-POFs, and we further show that gigabit per second transmission is also possible beyond 50m of SI-POF. Moreover, it generally demonstrates that competitive data rates using LEDs and p-i-n diode reception are possible with a well-adapted digital signal processing scheme. The results obtained here may also serve as a valuable information on how to maximize the bitrate of LED-based visible light communication (VLC) systems.