Cp Christos Tsekrekos

Design Considerations for a Transparent Mode Group Diversity Multiplexing Link

Mode group diversity multiplexing (MGDM) is an optical multiple-input-multiple-output technique that aims at creating independent communication channels over a multimode fiber, using subsets of propagating modes. This letter deals with the analysis of an MGDM point-to-point link, transparent to the transmission format. The geometry of a mode-group selective multi/demultiplexer is optimized in order to minimize the crosstalk among the channels. The power penalty is calculated when a zero-forcing algorithm is used to mitigate the crosstalk

Mode-selective spatial filtering for increased robustness in a mode group diversity multiplexing link

We propose a very simple optical method to reduce the cross talk among the channels of a mode group diversity multiplexing (MGDM) link. MGDM is an intensity modulation, direct detection, multiple-input, multiple-output technique that creates independent communication channels over a multimode fiber (MMF). The cross talk among the channels is mitigated electronically. However, by properly employing a lens between the output of a graded-index MMF and the detectors, we achieve mode-selective spatial filtering (MSSF) and optically reduce the cross talk. The robustness of the link is then increased when compared with an implementation without MSSF. This allows for a larger number of channels.

Temporal Stability of a Transparent Mode Group Diversity Multiplexing Link

The temporal behavior of a mode group diversity multiplexing (MGDM) link is examined. MGDM has been proposed as a way of creating parallel, independent communication channels over multimode fiber (MMF) links using different groups of modes. When the effect of dispersion can be neglected, the output electrical signals of an MGDM link are related to the input ones via a real-valued transmission matrix. The transmission matrix is vulnerable to changes in the modal spectrum of the propagating mode groups as well as to the coupling of light at the input and output of the MMF. Measurements of the transmission matrix of a two-input two-output system over 12.7 h show that an MGDM link can be very stable

Demonstration of a Transparent 2-Input 2-Output Mode Group Diversity Multiplexing Link

This paper reports the first demonstration of a transparent 2-input 2-output mode group diversity multiplexing link. A zero-forcing algorithm, implemented in an analogue circuit, is used to reduce the interference between the two channels.

Symmetric Few-Mode Fiber Couplers as the Key Component for Broadband Mode Multiplexing

All-fiber broadband mode multiplexers (MMUXs) for mode and wavelength division multiplexing transmission systems are designed and analyzed. The MMUXs are based on cascaded 2-D or 3-D symmetric few-mode fiber (FMF) couplers. The MMUXs are optimized for operation over the C band and multiplex modes LP01, LP11a, LP11b, LP21a, LP21b, and LP02 with a nearly flat response and an average insertion loss around 1.6 dB, depending on the design approach. The operation of the FMF couplers and the MMUXs is analyzed numerically by means of a full-vectorial beam propagation method. If the two polarization states of each LP mode are further considered, such all-fiber MMUXs can be used to combine 12 spatial channels, supporting an order of magnitude capacity increase-compared to a single spatial channel system-in optical fiber transmission systems through space (mode and polarization) division multiplexing.

Mitigation of Impairments in MGDM Transmission With Mode-Selective Spatial Filtering

A model for a mode group diversity multiplexing (MGDM) transmission system is derived. The factors that may limit MGDM transmission are identified. An optical method to reduce the spatial overlap among the fields of the detected mode groups could mitigate impairments that may occur in MGDM transmission. Mode-selective spatial filtering (MSSF) is such an optical method. Experimental results support that a robust five-channel MGDM system could be realized with MSSF, as long as modal noise is limited. MSSF facilitates the combination of MGDM with wavelength-division multiplexing.

Distribution of Millimeter-Wave and Baseband Services Over an Integrated Reconfigurable Access Network Platform

An experimental investigation is presented that demonstrates how optical tunable filtering and polarization demultiplexing can be used to realize reconfigurable remote access nodes (RAN) in the context of future access networks that integrate diverge services. In particular, transmission of 60-GHz radio-over-fiber and baseband signals is successfully shown considering two reconfigurable RAN architectures. One based on optical tunable filtering and polarization demultiplexing and another one based only on optical tunable filtering. The perceived network architecture is that of multilevel ring/bus configuration and a two-RAN experiment shows the robustness of polarization multiplexing/demultiplexing in such a reconfigurable access network solution. The assets of physical-layer reconfigurability are discussed.

Experimental study of the temporal behaviour of a mode group diversity multiplexing link

This paper reports an experimental investigation on the temporal variations of the transmission matrix of a 2-input 2-output mode group diversity multiplexing MMF link; such a link is shown to be very stable.

Performance evaluation and improvement methods for low-driving voltage transmitters in long reach PONs

The performance of two common low-driving voltage (low-ER) sources is experimentally evaluated for long reach PON applications, considering also partial optical dispersion compensation and electronic equalization methods for performance improvement.

Optical-Wireless Network with Multi-Layer Reconfigurability

Current telecom access architectures do not support broadband networking in a converged way on fixed/mobile networks. Here, a highly-configurable optical-wireless network is presented capable of handling dynamics inferred by user mobility and varying service demands.