Abstract: Methods and apparatus for supporting a plurality of modulation formats using a single transmitter are disclosed. According to one aspect of the present invention, a transmitter arrangement that provides a signal to a modulator that creates an optical data stream from the signal includes an encoder and a switching/filtering arrangement. The encoder has a state that is varied between first and second encoder states. If the state is the first encoder state, the encoder encodes the signal in a format associated with an optical duobinary (ODB) modulation format. Otherwise, the encoder does not encode the signal in the format associated with the ODB modulation format. The switching/filtering arrangement receives the signal from the encoder, and provides the signal to the modulator. If the variable state of the encoder is the first encoder state, the switching/filtering arrangement has a low bandpass configuration. Otherwise, the switching/filtering arrangement has a high bandpass configuration.

Abstract: A transponder unit which relays signals between a plurality of channels of an optical transport network and a plurality of clients. The interconnections within the transponder unit are reconfigurable for selective connections. A connection between a first client and a first network channel and a connection between a second client and a second network channel is independent of each other and may be selected so that the second client is connected to the first network channel and the first client is connected to the second network channel. Other selected connections are also possible.

Abstract: A transponder unit which relays signals between a plurality of channels of an optical transport network and a plurality of clients. The interconnections within the transponder unit are reconfigurable for selective connections. A connection between a first client and a first network channel and a connection between a second client and a second network channel is independent of each other and may be selected so that the second client is connected to the first network channel and the first client is connected to the second network channel. Other selected connections are also possible.

Abstract: 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.

Abstract: Electro-optical modulator (100), comprising at least one electrical port (918, 919) and an input circuit (915, 916, 917) 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 (250) 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 (2, 3) for eliminating predetermined spectral components from the said fraction of the modulating electrical signal, and at least one phase-shifting element (4, 6) 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.

Abstract: A network (100) for distributing signals to a plurality of user apparel comprising: a distribution unit (40) having a plurality of ports, and a plurality of optical-fibre cables (9) connected to said ports and suitable to make said plurality of ports of said distribution unit (40) communicate with said plurality of user apparatuses, wherein at least one of said plurality of optical-fibre cables (9) is an electrically terminated optical cable (1) comprising an optical cable (9) with a single-mode optical fibre and an opto-electronic end portion (10) mechanically and permanently connected to an end of said optical cable, and said opto-electronic end portion (10) comprises an opto-electronic conversion device,(12; 13) having an optic port optically aligned with and mechanically connected to, an end of said single-mode optical fibre.

Abstract: Electro-optical modulator (100), comprising at least one electrical port (918, 919) and an input circuit (915, 916, 917) 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 (250) 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 (2, 3) for eliminating predetermined spectral components from the said fraction of the modulating electrical signal, and at least one phase-shifting element (4, 6) 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.