Pirelli Cavi E Sistemi S.p.a.

Pirelli Cavi S.p.a.

Avanex Corporation

Giuseppe Ravasio

Claudio Zammarchi

Massimo Notargiacomo

Franco Mussino

Flavio Fontana

Guido Oliveti

Federico Franzoso

Gianluca Gobetti

Paolo Brambilla

A network for distributing signals to a plurality of user apparatuses having a distribution unit with a plurality of ports, and a plurality of optical-fiber cables connected to the ports and suitable to make the plurality of ports of the distribution unit communicate with the plurality of user apparatuses. At least one of the plurality of optical-fiber cables is an electrically terminated optical cable having an optical cable with a single-mode optical fiber and an opto-electronic end portion mechanically and permanently connected to an end of the optical cable, and the opto-electronic end portion has an opto-electronic conversion device having an optic port optically aligned with and mechanically connected to, an end of the single-mode optical fiber.

Network for distributing signals to a plurality of users

Electro-optical modulator (), comprising at least one electrical port () and an input circuit () for the application of a modulating electrical signal to the said at least one electrical port. The said modulator also comprises a linear processing circuit () capable of generating a compensation signal. This linear processing circuit comprises a first terminal connected to the input circuit for taking a fraction of the said modulating electrical signal, at least one filtering element () for eliminating predetermined spectral components from the said fraction of the modulating electrical signal, and at least one phase-shifting element () for inverting the phase of the said fraction of the modulating electrical signal. The said linear processing circuit also comprises a second terminal capable of being connected to the said at least one electrical port for applying the compensation signal to the said electro-optical modulator.

Method of analog modulation and optical emitter using this method

The present invention relates to a method and to a signal predistorter circuit for eliminiating the nonlinearities in the input/output characteristics of nonlinear stages, in particular for eliminating the third-order nonlinearities. More particularly, it relates to a method and to a predistorter circuit for external optical modulators of television signals. The method for predistortion of a signal of variable amplitude comprises the phases of: delivering the said signal to at least one first distorter circuit; biasing the said at least one first distorter circuit; distorting the said signal in the said at least one first distorter circuit; characterized in that the said phase of biasing the said at least one first distorter circuit comprises the phase of maintaining a substantially constant preset voltage value on varying the amplitude of the said signal at the said at least one first distorter circuit.

External optical modulation system comprising a predistorter

An optical communication system is described which includes an optical source; an optical modulator, receiving a transmission signal having frequencies included within a signal band and adapted to emit a modulated optical signal of a predetermined optical bandwidth; an optical transmission line comprising an optical fiber portion; and an optical receiver adapted to receive the optical signal in the presence of a predetermined SNR in the signal band, measured in a 5 MHz band. The telecommunication system further comprises, optically connected between the optical modulator and the optical transmission line, a depolarizer comprising two polarization-maintaining optical fiber portions, optically connected with each other in such a manner that the respective polarization axes form an angle of 45.degree., in which the optical bandwidth, lengths and birefringence of the polarization-maintaining optical fibers are operatively selected so that the SNR at the receiver in the signal band does not differ more than 1 dB from the SNR at the receiver measured in a band of 5 MHz by substituting the optical fiber portion of the transmission line with a passive attenuator of same attenuation.

Modulated and depolarized optical signal transmission system

An analog-external-modulation optical, emitter is described which comprises an electro-optical modulator and a piloting circuit. The piloting circuit comprises a pilot-tone-generating circuit; an electric control signal generated by the optical signal coming out of the modulator and a predetermined bias voltage are fed to the input of a differential amplifier the output of which is added to the pilot tone to feed an electric input of the electro-optical modulator. The RF input of the analog electric signal is connected to a linearizer circuit to which the pilot-tone-generating circuit is also connected. The output of the linearizer circuit is sent to an electric input of the electro-optical modulator through a band-stop filter adapted to eliminate the pilot tone downstream of the linearizer circuit.

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Capriate San Gervasio, Italy

Giuseppe Ravasio