Christian-Alexander Bunge

Reach-dependent capacity in optical networks enabled by OFDM

In todays optical networks, the channel capacity is designed for the systems maximum reach. By using OFDM, reach dependent capacity can be realized which improves the network performance substantially.

Cost Comparison of Networks Using Traditional 10 and 40 Gb/s Transponders Versus OFDM Transponders

OFDM allows flexible adjustment of transmission data rate according to channel properties. We propose to use OFDM transponders and calculate the cost at which OFDM networks result in lower CAPEX compared to traditional networks.

Geometric Optics Analysis of Multi-Step Index Optical Fibers

The double aim of the present article is to give a brief description of our research groups main results achieved in recent years and to provide a comprehensive analysis of light propagation properties in multi-step index (MSI) fibers based on the geometric optics method. Therefore, in the initial part we present our research team and its main lines of research on plastic optical fibers (POF). Afterward, the discussion focuses on a new theory we have developed for the propagation in MSI fibers. First of all, we derive the ray invariants ˜β and ˜l, which allow us to instantly determine the direction of the ray at any position along its trajectory, and we discuss the characteristics of the ray path, setting the classification of rays into bound, refracting and tunneling categories. Then, we calculate the ray-path parameters, namely the path length Lp, the ray half period zp and the ray transit time t. Furthermore, we analyze the ray temporal dispersion. Specifically, we take a practical case in which the width of each layer is maintained constant, allowing, in contrast, for the respective refractive indices to take any value, and we derive closed expressions for the ray dispersion. Finally, we investigate the light power acceptance properties of an MSI fiber, calculating the effectiveness of both diffuse and collimated light sources in launching bound rays and the coupling losses with lateral and longitudinal misalignments.

Precoding Based Peak-to-Average Power Ratio Reduction for Optical OFDM demonstrated on Compatible Single-Sideband Modulation with Direct Detection

Clipping-aided precoding is suggested for effective PAPR reduction to improve performance of OFDM. Up to 3.7 dB PAPR reduction is shown. Performance improvements in required OSNR and dispersion tolerance are demonstrated on compatible SSB.

Noise suppression properties of an interferometer-based regenerator for differential phase-shift keying data

We studied the amplitude and phase noise suppression properties of an all-optical regenerator for differential phase-shift keying data. A detailed analytical investigation is performed and compared with numerical simulations for different working points. The results show that both amplitude and phase can be regenerated. However, simultaneous amplitude and phase noise suppression is possible only if the phase degradation is stronger than the amplitude degradation, for instance, due to nonlinear phase noise.

Analysis of a plastic optical fiber-based displacement sensor

An easy-to-manufacture setup for a displacement sensor based on plastic optical fiber (POF) is analyzed, showing computational and experimental results. If the displacement is the consequence of force or pressure applied to the device, this can be used as a force or pressure transducer. Its principle of operation consists of bending a POF section around a flexible cylinder and measuring light attenuation when the whole set is subjected to side pressure. Attenuations are obtained computationally as a function of side deformation for different design parameters. Experimental results with an actually built prototype are also provided.

Equivalent dispersion maps in fibre-optic communication systems

We show that under certain conditions it is possible to define an equivalent single-span system for an arbitrary dispersion-managed multi-span system. This can facilitate the optimization of dispersion maps.

Electronic Precompensation of Intra-Channel Nonlinearities at 40 Gbit/s

Electronic precompensation of intra-channel nonlinearities is theoretically studied in a transmission system consisting of 100% dispersion compensated spans. Different Mach-Zehnder transmitter structures are compared. Using a triple Mach-Zehnder modulator achieves effective compensation at 40 Gbit/s.

Tolerant launching scheme for short-reach multimode fibre connections with non-ideal offset connectors

In short-reach connections, large-diameter multimode fibres allow for robust and easy connections. Unfortunately, their propagation properties depend on the excitation conditions. We propose a launching technique using a fibre stub that can tolerate fabrication tolerances in terms of tilts and off-sets to a large extent. A study of the influence of displaced connectors along the transmission link shows that the power distributions approach a steady-state power distribution very similar to the initial distribution established by the proposed launching scheme.

Fibre-Independent Optimum Dispersion Mapping for SPM and XPM Suppression in 10 Gbit/s WDM NRZ Optical Transmission Systems

We show that XPM can be reduced by an appropriate residual dispersion per span, which only depends on walk-off conditions between adjacent wavelength channels independent of fibre types. Suitable pre-compensation will also suppress SPM effects.