Fabrizio Chiarello

Polarization Attraction in Counterpropagating Fiber Raman Amplifiers

Polarization attraction in counterpropagating, randomly birefringent, fiber Raman amplifiers is numerically investigated, including the effects of nonlinear polarization rotation, pump depletion and orthogonal Raman gain. The analysis determines the limitations of the pulling efficiency, and shows that the maximum achievable mean degree of polarization is a function of the mean gain.

Experimental characterization of the counter-propagating Raman polarization attraction.

Recently, fiber Raman amplifiers have proven to be effective in the all-optical control of the state of polarization of signals in single-mode telecommunications optical fibers. Previous works predicted the existence of a quantitative relationship between the achieved degree of polarization and the mean Raman gain. Here, we experimentally validate such a relationship in the case of counter-propagating Raman-based polarization attractors for different pump and signal powers and for different fiber link lengths.

Experimental analysis of degenerate vector phase-sensitive amplification

We comprehensively investigate a degenerate vector phase-sensitive amplifier (PSA). We determine the gain dependence on the relative phase and polarization angle between the pumps and the degenerate signal wave. The vector PSA is experimentally shown to be sensitive to the pump states of polarization (SOP) due to polarization mode dispersion in the fiber. However, the scheme performance agrees well with theory under specific pump SOPs and we achieve an on-off gain over 10 dB with a small deviation from the theoretically expected results. In comparison to the scalar scheme, the proposed vector scheme has larger tolerance for pump depletion due to four-wave mixing between pumps and generation of higher-order idlers.

Phase-Sensitive Amplification and Regeneration of Dual-Polarization BPSK without Polarization Diversity

We analyze the performance of a degenerate vector PSA-based receiver and compare to an EDFA-based receiver, achieving an about 1 dB sensitivity improvement. We also assess the phase regeneration provided by the vector PSA when the signal phase is degraded.

Distributed characterization of localized and stationary dynamic Brillouin gratings in polarization maintaining optical fibers

We experimentally generate localized and stationary dynamic Brillouin gratings in a 5 m long polarization maintaining fiber by phase-modulation of the pumps with a pseudo-random bit sequence. The dynamic Brillouin gratings are characterized in terms of length, bandwidth, group delay and group delay ripple, optical signal-to-noise ratio and peak to sidelobe ratio by measuring the distribution of the complex reflected signal along the fiber through swept-wavelength interferometry. By numerical processing, the performance of an optimal modulation format enabling null off-peak reflections are estimated and compared to the pseudo-random bit sequence case.

Securing Wireless Infrared Communications Through Optical Chaos

A wireless infrared optical chaotic communication system, for the secure transmission of a digital message at hundreds of megabits per second is presented. A numerical investigation of the system is performed for various configurations, to evaluate the synchronization error and the Q-factor with respect to the impairments due to the indoor infrared channel.

Generation of dynamic Brillouin grating in polarization maintaining fiber

We report an experimental demonstration and characterization of dynamic Brillouin gratings (DBGs) in a 5m long polarization-maintaining fiber (PMF) using heterodyne detection. The dependence of DBG reflectivity on the Brillouin gain and on the pumps and the probe powers is studied and reported.

Characterization of reconfigurable ultra-narrowband optical filters realized by localized dynamic Brillouin gratings

We experimentally demonstrate reconfigurable ultra-narrowband optical filters realized by localized dynamic Brillouin gratings in a polarization maintaining fiber. The filters are characterized in terms of bandwidth, optical signal-to-noise ratio and peak to sidelobe ratio.

Widely time-dispersion-tuned fiber optical oscillator and frequency comb based on multiple nonlinear processes

An all-fiber optical oscillator based on three nonlinear processes, namely stimulated Raman scattering and broad-band and narrow-band optical parametric amplification, is presented and experimentally characterized. The wavelength tuning is achieved by means of the time-dispersion technique and spans over 160 nm. Through the same technique a fast tunable optical frequency comb has been realized exploiting cascaded four-wave mixing.