Massimo Calzavara

Instabilities in a semiconductor laser with delayed optoelectronic feedback

Abstract A single mode CW semiconductor laser with an optoelectronic feedback gives a modulated output, with a sharp frequency peak depending on the feedback delay. A theoretical model, with few parameters assigned from the experiment, yields quantitative agreement with observations.

A new procedure for analysis of single-mode-fiber far-field data

Abstract A new procedure for analysis of far-field data on single-mode fibers is proposed; it allows one to obtain mode field diameters with reproducibility of ±0.05 μm or better and to reconstruct reliably and unambiguously the refractive-index profile even for dispersion-modified fibers with moderate requirements on dynamic range of the measurements.

A new approach to investigating mode coupling phenomena in graded-index optical fibres

To study mode coupling in optical fibres a new technique is developed, based on mode selective excitation and output near-field analysis. Experimental results support decoupling of the problem into two phenomena which are effective on different scales of propagation length: azimuthal and longitudinal mode mixing. A statistical model providing a simulation of the experimental near-field patterns is developed. Comparison with measurements shows that azimuthal mixing is complete before 1 km propagation, while effects of uncomplete axial coupling are accounted for. This approach also suggests a method for measuring the steady-state distribution length, with useful system implications.

Steady-state and dynamic characteristics of bistable DFB amplifiers for all optical switching

The steady-state and dynamic properties of a DFB amplifier have been analyzed from theoretical and experimental viewpoints. The linewidth enhancement factor has been estimated from the experimental hysteresis cycle using an inversion technique of the device transmissivity. The dynamic behavior of the DFB has been tested at 622 Mbit/s and the experimental results are supported by numerical simulations based on an assessed model.