Ranks of binary relations

This paper clarifies the notion of rank of a binary relation. Indeed several definitions cohabit in the literature and two of them have never been distinguished. The main results concern the comparison of these two notions. We show that the two definitions are really different, even under strong restrictive conditions about the algebraic structure of the semigroup.     

FTTx automated test solution: Requirements and experimental implementation

The requirements for preventive maintenance of point-to-multipoint passive optical networks is investigated. The method developed, based on the use of an OTDR, of reference variable reflectors and of a proprietary signal-analysis software is described. Faults in the network are identified, quantified and localised, making the preventive maintenance possible.     

Physical layer characterization of hybrid fibre coax (HFC) networks

This paper reviews the future prospects of cable television networks through their evolution towards HFC topology. This upgrade will allow cable operators to provide full broadband bi-directional communications (image, data and voice) and generate new revenues from their existing network. This article focuses on: what is an HFC topology, what are the relevant parameters to characterize its physical layer, what are the technological key issues and future trends?     

Chromatic dispersion modeling of single-mode optical fibers: adetailed analysis

We present here an efficient method for single-mode fiber modeling. This paper deals mainly with chromatic dispersion computation but the analysis can be extended to other single-mode characteristics. This synthesis shows that key-parameters have to be correctly chosen in order to insure an accurate modeling of chromatic dispersion. Finally, the results we obtained with this method are presented. The agreement between theoretical calculations and measurements is also explained     

Theoretical and experimental study of second-order distortions inCATV DFB laser diodes

Calculation of linearity performances of a given DFB laser is a well-known problem when working with CATV AM-VSB optical links. In this paper, a nonlinear model of the DFB laser is presented. The bias and frequency dependence of second order intermodulation distortion is analyzed by combining Volterra models of the laser leakage current and rate equations. The prediction of the model is then compared to distortion measurements with a maximum discrepancy of around 1.5 dB     

Experimental and Theoretical Evaluation of Distortion Effects on SCM Optical Transmissions Due to the Joint Action of Static Chirping,Dynamic Chirping and Dispersive Channel

In optical CATV systems based on subcarrier-multiplexing technique, the joint action of semiconductor laser chirp and fiber chromatic dispersion gives rise to intermodulation distortion phenomena affecting the transmission performance. This problem has been explained analytically, leading to a model valid for every kind of modulating signal and explored in the case of a Gaussian process. In this paper, the model is developed for the important specific case of an analogue SCM modulating signal. The results are assessed experimentally.