Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.

Abstract: An optical transmitter for a WDM (Wavelength Division Multiplexing) passive optical network (PON) and a WDM PON comprising such an optical transmitter are disclosed. An optical transmitter comprises first mirror and second mirrors at first end and second ends of a cavity; an optical amplifier positioned within the cavity upstream from the first mirror and for amplifying light polarized in a first polarization plane; an optical waveguide for transmitting light from the optical amplifier to the second mirror and vice versa; a first non-reciprocal polarization rotator upstream of the optical amplifier and downstream of the optical waveguide; and a second non-reciprocal polarization rotator upstream of the optical waveguide and downstream of the first mirror; wherein the first and second non-reciprocal polarization rotators rotate the polarization of the light such that light which re-enters the optical amplifier after having been reflected by the second mirror is polarized in the first polarization plane.

Abstract: An optical communication system (100; 2300) comprises at least a transmitter (110) apt to emit a differential phase shift keying (DPSK) optical signal having a bit-rate equal to R, at least a receiving system (1200) for receiving the differential phase shift keying optical signal; and an optical link (130) optically connecting the transmitter and the receiving system for transmitting the DPSK optical signal from the transmitter to the receiving system, wherein the receiving system comprises a coherent optical receiving device (1205) apt to coherently receive the propagated DPSK optical signal and to emit at least one electrical signal (I) related to the received DPSK optical signal, and wherein the receiving system further comprises at least one electrical filter (270) for filtering the at least one electrical signal and having ?3 dB double-side bandwidth greater than or equal to 0.44 R and lower than or equal to 0.68 R, and at least one squarer (280) for squaring the at least one filtered electrical signal.

Abstract: An optical transmission system having an optical source, an optical dispersion compensation filter optically connected to the optical source, and a control system. The optical source generates a modulated optical signal having an optical spectrum and a value of dispersion robustness. The optical dispersion compensation filter has at least two cascaded optical resonators and a periodic transfer function rigidly translatable in the frequency spectrum to obtain translation in frequency of the transfer function without a substantial change in shape, and characterized by a free spectral range. The control system acts on the optical dispersion compensation filter in order to rigidly translate the transfer function along the frequency spectrum in first and second positions in the frequency spectrum. The translation of the transfer function between the first and the second positions is smaller than the free spectral range.

Abstract: A device and method for stabilizing the state of polarization of polarization multiplexed optical radiation including an identified channel is disclosed.

Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.

Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.

Abstract: A device and method for stabilizing the state of polarization of polarization multiplexed optical radiation including an identified channel is disclosed.

Abstract: A device and method for stabilizing the polarization of polarization multiplexed optical radiation includes an identified channel which is provided with a pilot signal.

Abstract: An optical communication system (100; 2300) comprises at least a transmitter (110) apt to emit a differential phase shift keying (DPSK) optical signal having a bit-rate equal to R, at least a receiving system (1200) for receiving the differential phase shift keying optical signal; and an optical link (130) optically connecting the transmitter and the receiving system for transmitting the DPSK optical signal from the transmitter to the receiving system, wherein the receiving system comprises a coherent optical receiving device (1205) apt to coherently receive the propagated DPSK optical signal and to emit at least one electrical signal (I) related to the received DPSK optical signal, and wherein the receiving system further comprises at least one electrical filter (270) for filtering the at least one electrical signal and having ?3 dB double-side bandwidth greater than or equal to 0.44 R and lower than or equal to 0.68 R, and at least one squarer (280) for squaring the at least one filtered electrical signal.

Abstract: Optical transmission system (200) comprising: an optical source (210) adapted to generate a modulated optical signal having an optical spectrum and a dispersion robustness; an optical dispersion compensation filter (250) optically connected to the optical source, comprising at least two cascaded optical resonators and having a periodic transfer function that is rigidly translatable in the frequency spectrum and characterized by a free spectral range (FSR); a control system (270; 280; 260) adapted to act on the optical compensation filter in order rigidly to translate said transfer function along the frequency spectrum in a first and in a second position in such a way that: in a first position in the frequency spectrum of said transfer function, the mean chromatic dispersion weighted over said optical spectrum of the modulated signal is greater, in absolute value, than the value of dispersion robustness; in a second position in the frequency spectrum of said transfer function, the mean chromatic dispersion wei

Abstract: A device and method for stabilizing the polarization of polarization multiplexed optical radiation includes an identified channel which is provided with a pilot signal.

Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.

Abstract: An optical communication system has a transmitter generating a phase-modulated optical signal (Sa, Sb, . . . , Sk); a receiver for receiving the phase-modulated optical signal; an optical communication link between the transmitter section and the receiver section. The optical communication link is a dispersion-managed optical communication link having dispersion-compensating elements propagating the phase-modulated optical signal at substantially constant optical power. The receiver has a dispersive element having a prescribed dispersion, the dispersive element receiving and converting the phase-modulated optical signal into a corresponding intensity-modulated optical signal, and an optical intensity detector fed with the intensity-modulated optical signal.

Abstract: A wavelength converter or demultiplexer device comprising first and second stages (30, 40). For wavelength converter action, the first stage impresses an intensity modulation (IM) and phase modulation (PM) on a CW input signal (?1) carried by an input DATA signal (?2) using cross phase modulation in a non-linear optical element (46). The first stage in an embodiment is a semiconductor laser amplifier loop optical mirror (SLALOM) which has a semiconductor optical amplifier (SOA) as the non-linear optical element. The second stage has a non-linear transfer function and impresses a further IM on the optical signal responsive to the PM impressed in the first stage. In an embodiment, the second stage is a polarization maintaining fiber (PMF) optical loop. The transfer function of the overall device is thus improved by making it steeper and more time confined.

Abstract: A wavelength converter or demultiplexer device comprising first and second stages (30, 40). For wavelength converter action, the first stage impresses an intensity modulation (IM) and phase modulation (PM) on a CW input signal (?1) carried by an input DATA signal (?2) using cross phase modulation in a non-linear optical element (46). The first stage in an embodiment is a semiconductor laser amplifier loop optical mirror (SLALOM) which has a semiconductor optical amplifier (SOA) as the non-linear optical element. The second stage has a non-linear transfer function and impresses a further IM on the optical signal responsive to the PM impressed in the first stage. In an embodiment, the second stage is a polarization maintaining fiber (PMF) optical loop. The transfer function of the overall device is thus improved by making it steeper and more time confined.

Abstract: An optical device for providing threshold and comparison functions. The device comprises first and second SOA's having respective first and second propagation paths along which the first and second optical signals, input as signals Pin1(&lgr;1) and Pin2(&lgr;2) travel in first and second forward directions. A feedback path is provided using couplers to interconnect the outputs of the SOA's. As a result, a portion of the optical signals output from each SOA is supplied backwards into the output of the other SOA as feedback optical control signals Pfeedback1(&lgr;1) and Pfeedback2(&lgr;2). The feedback optical control signals modulate the gain of the forwards travelling optical signals by cross gain modulation (XGM). In contrast to prior art devices, the optical control signal is supplied backwards into the SOA's in a counter-propagating configuration. This allows much shorter feedback path lengths to be achieved in comparison to what is possible with prior art co-propagating configurations.

Abstract: A wavelength converter or demultiplexer device comprising first and second stages (30, 40). For wavelength converter action, the first stage impresses an intensity modulation (IM) and phase modulation (PM) on a CW input signal (&lgr;1) carried by an input DATA signal (&lgr;2) using cross phase modulation in a non-linear optical element (46). The first stage in an embodiment is a semiconductor laser amplifier loop optical mirror (SLALOM) which has a semiconductor optical amplifier (SOA) as the non-linear optical element. The second stage has a non-linear transfer function and impresses a further IM on the optical signal responsive to the PM impressed in the first stage. In an embodiment, the second stage is a polarization maintaining fiber (PMF) optical loop. The transfer function of the overall device is thus improved by making it steeper and more time confined.

Abstract: An optical window signal generator which begins generation of an optical output signal in response to an optical activation pulse, and terminates generation of the optical output signal in response to an optical deactivation pulse. The rise time of the optical output signal is equal to the rise time of the optical activation pulse, and its fall time is equal to the rise time of the optical deactivation pulse.

Abstract: An optical device for providing threshold and comparison functions. The device comprises first and second SOA's having respective first and second propagation paths along which the first and second optical signals, input as signals Pin1(&lgr;1) and Pin2(&lgr;2) travel in first and second forward directions. A feedback path is provided using couplers to interconnect the outputs of the SOA's. As a result, a portion of the optical signals output from each SOA is supplied backwards into the output of the other SOA as feedback optical control signals Pfeedback1(&lgr;1) and Pfeedback2(&lgr;2). The feedback optical control signals modulate the gain of the forwards travelling optical signals by cross gain modulation (XGM). In contrast to prior art devices, the optical control signal is supplied backwards into the SOA's in a counter-propagating configuration. This allows much shorter feedback path lengths to be achieved in comparison to what is possible with prior art co-propagating configurations.