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We present a novel all-fiber optical tweezer (OT) for biological applications. The tweezer is based on a new approach relying on total internal reflection in an annular core fiber or into a fiber bundle. The proposed device, whose trapping efficacy has been recently demonstrated experimentally, is extremely promising, also because optical manipulation and analysis functions can be easily added to the tweezer basic structure, leading to the realization of a powerful biotool. In this paper, a detailed numerical analysis of the structure properties and of its efficiency is carried out in the Mie regime. Moreover, by defining a new parameter to evaluate the trapping efficiency, we perform a comparison between the proposed tweezer structure and a standard OT based on a strongly focused Gaussian beam. [ABSTRACT FROM PUBLISHER]

Several Bragg-grating (BG) filters employing an asymmetrical and multilobe apodization curve, obtained by inverse-problem solving techniques, have been described in literature. To our knowledge, the roles played by the asymmetry of the apodization function and by each apodization lobe have never been determined. In this paper, the role of the lobes and asymmetry is mathematically analyzed, and the validity of the given description is numerically demonstrated. The physical insight gained allows to optimize the filters obtained as solution of the inverse problem. [ABSTRACT FROM PUBLISHER]

One of the main causes of signal degradation in high-bit-rate transmission systems is the interplay between fiber nonlinear effects and dispersion. Different techniques to compensate nonlinear effects in transmission systems, by using an optical phase conjugator, have been proposed in the literature. In this paper, two different innovative setups allowing nonlinearity cancellation in an embedded link are disclosed. The proposed schemes are simpler than those previously described and strongly improve systems performances. The physical mechanism allowing nonlinearity compensation is depicted, and the effectiveness of the proposed solutions is numerically demonstrated. Moreover a new practical method, useful for performance optimization of systems including a phase conjugator, is presented. Results apply to any bit-rate and modulation format. [ABSTRACT FROM PUBLISHER]

The development of wavelength-division multiplexing (WDM) all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this paper, an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5×100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization-independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counterpropagation of TE and TM signal components along the same guide and results extremely compact. In this paper it is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks. [ABSTRACT FROM PUBLISHER]

Wavelength conversion in the transmission of a message masked by optical chaos is experimentally demonstrated. In our setup, chaos is generated by a distributed-feedback laser subject to delayed optical feedback, and hides a message by additive chaos masking. The optical wavelength is converted, along the transmission line, by four-wave mixing in a semiconductor optical amplifier. At the receiver, the message is extracted by master-slave synchronization. Our experiments demonstrate that secure communications based on chaos are compatible with channel switching as required in reconfigurable optical networks. [ABSTRACT FROM PUBLISHER]

The authors carry out a numerical and experimental comparison between three different techniques for chromatic dispersion compensation on a terrestrial 40-Gb/s system. They are: periodic dispersion compensation at the amplifier places; the same but with initial prechirp; and dispersion compensation all at the end of the system by means of highly dispersed pulses. Numerical results are consistent with experimental ones and suggest the most convenient compensation technique with respect to fiber type (G.652 or G.655) and pulsewidth (3-10 ps). [ABSTRACT FROM PUBLISHER]

Optical phase-modulated systems are promising candidates for the development of ultrahigh-bit-rate transmission links, thanks to their high spectral efficiency and increased tolerance to fiber-optic nonlinearities. However, their implementation was considerably slowed down by theoretical studies, suggesting that the transmission performance can be severely hindered by nonlinear phase noise (the so-called Gordon-Mollenauer effect). The simulations presented here show that, in realistic systems (including nonlinearity, dispersion, and attenuation), Gordon-Mollenauer noise does not represent the main source of signal distortions. We demonstrate that all nonlinear impairments can be efficiently compensated by optical phase conjugation, independent of system characteristics. The combination of optical-phase-conjugation with phase-modulation formats could enable ultrahigh-transmission-capacity and easy embedded-link upgrading.