Abstract: A polarization stabilizing device and method based on controlling the phase retardations of a pair of variable rotators with an optically interposed quarter-wave plate, with a controller such that the first of the variable rotators has its phase retardation switched between first and second values whenever the phase retardation of the second of the variable rotators reaches an upper or a lower limit. The upper and lower limits of the second rotator and the first and second values of the first rotator are chosen so that discontinuities in the power of the output optical radiation are avoided when the first variable rotator is switched, thereby providing endless polarization stabilization using rotators that themselves may have limited retardation ranges.

Abstract: An optical switching system includes a two-dimensional arrangement of a plurality of switching elements. Each switching element includes an optical guiding structure which includes two pairs of waveguides; a driving arrangement for individually moving the switching elements between at least a first and a second position; and a first and a second input and a second output. When a generic switching element is moved in the first position, the first pair of waveguides connects a first input with a first output, and a second input with a second output; when a generic switching element is moved in the second position, the second pair of waveguides connects the first input with the second output, and the second input with the first output. In a first embodiment, the waveguides are provided on a disc shaped carrier and lie in the same plane, which disc is rotated. In a second embodiment, the two pairs of waveguides lie in different planes and the waveguide carrier plate is moved up and down for switching.

Abstract: A wavelength converter device is provided for generating a converted radiation at frequency ?g through interaction between at least one signal radiation at frequency ?s and at least one pump radiation at frequency ?p, including an input for the at least one signal radiation at frequency ?s, a pump light source for generating the at least one pump radiation at frequency ?p, an output for taking out the converted radiation at frequency ?g, a structure for transmitting the signal radiation, including two optical resonators having a non-linear material, having an optical length of at least 40*?/2, ? being the wavelength of the pump radiation, and resonating at the pump, signal and converted frequencies ?p, ?s and ?g, wherein by propagating through the structure, the pump and signal radiation generate the converted radiation by non-linear interaction within the optical resonators.

Abstract: A polarization stabilizing device and method based on controlling the phase retardation of a pair of variable phase retarders with a controller such that the first of the variable retarders has its phase retardation switched between first and second values whenever the phase retardation of the second of the variable retarders reaches an upper or a lower limit. The upper and lower limits of the second retarder and the first and second values of the first retarder are chosen so that discontinuities in the power of the output optical signal are avoided when the first variable retarder is switched, thereby providing endless polarization stabilization using phase retarders that themselves have only limited retardation ranges.

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: Optical switch matrix having at least an input matrix port defining at least a row of the matrix, a plurality of output matrix ports defining columns of the matrix, a plurality of switching elements, each one being disposed at the intersection of at least one row and one of the columns. Each switch element in a predetermined position of the matrix, in an activated condition, connects an input matrix port to an output matrix port, the ports being correspondents respectively to the predetermined position of the matrix.

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: Wavelength converter device for generating a converted radiation at frequency ?g through interaction between at least one signal radiation at frequency ?g and at least one pump radiation at frequency ?g, with an input for the at least one signal radiation at frequency ?g; a pump light source for generating the at least one pump radiation at frequency ?g, an output for taking out the converted radiation at frequency ?g, a structure for transmitting the signal radiation, the structure including one optical resonator having a non-linear material, having an optical length of at least 40*?/2, wavelength ? being the wavelength of the pump radiation, and resonating at the pump, signal and converted frequencies ?p, ?s, and ?g.

Abstract: In an interferometer configuration, a retarder in the form of a half-wave plate (125) and a phase shifter in the form of a glass plate (120) are arranged in one arm (114). The phase shifter provides an optical path difference between the interferometer arms which needs to be greater than the coherence length of the input light to be polarization stabilized. A polarizer in the form of a linear polarizer (118) aligned at 45° to the half-wave plate is arranged across both interferometer arms (114 & 116). Polarization stabilization action is achieved by the retarder in combination with the polarizer. More specifically, for at least one input polarization state, the polarization states in the two interferometer arms are rendered orthogonal by the retarder, the polarizer being aligned to allow only one of the two orthogonal states to be transmitted, the other being absorbed. The device is expected to find application for WDM networks based on broadband sources, such as superluminescent diodes.

Abstract: The invention relates to new polymers useful in non linear optical (NLO) applications, particularly as optical waveguide materials.

Abstract: Optical switch matrix having at least an input matrix port defining at least a row of the matrix, a plurality of output matrix ports defining columns of the matrix, a plurality of switching elements, each one being disposed at the intersection of at least one row and one of the columns. Each switch element in a predetermined position of the matrix, in an activated condition, connects an input matrix port to an output matrix port, the ports being correspondents respectively to the predetermined position of the matrix.

Abstract: A polarization stabilizing device and method based on controlling the phase retardation of a pair of variable phase retarders with a controller such that the first of the variable retarders has its phase retardation switched between first and second values whenever the phase retardation of the second of the variable retarders reaches an upper or a lower limit. The upper and lower limits of the second retarder and the first and second values of the first retarder are chosen so that discontinuities in the power of the output optical signal are avoided when the first variable retarder is switched, thereby providing endless polarization stabilization using phase retarders that themselves have only limited retardation ranges.

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 crystal made of CdxZn1−xTe provides an electro-optical switch that performs consistently at high and low switching frequencies for signals of the 1000-1650 nm wavelength window. Preferably, a crystal of Cd0.9Zn0.1Te is driven with an electrical voltage to cause polarization rotation and switching action for a passing optical signal. Despite having a higher light absorption coefficient than CdTe:In, Cd0.9Zn0.1Te surprisingly exhibits a weak auto-inhibition effect, giving it better electro-optic performance when used in conjunction with optical wavelengths and optical powers characteristic of optical communication systems. Optical switch matrices and optical cross-connect switches in optical communication systems may effectively use Cd0.9Zn0.1Te crystals.

Abstract: An optical intensity modulator for high-speed RZ and NRZ data modulation based on a balanced three-arm Mach-Zehnder interferometer. The three arms are joined at the input and output sides of the device by three-way couplers. The input coupler is structured to couple approximately equal powers into the first and third arms and no more than 50% power into the second arm. In the straight sections of the arms, there is arranged an AC electrode structure for applying an RF modulation signal and a DC electrode structure for biasing the device at a working point. The AC electrode structure is arranged so that an applied modulation signal induces a negative phase shift (−&Dgr;&phgr;) in the first arm in relation to the second arm and a positive phase shift (+&Dgr;&phgr;) in the third arm in relation to the second arm.

Abstract: An apparatus for gating an optical signal comprising: an input stage arranged to receive and combine first and second optical control signals (ON, OFF) of first and second wavelengths, and an optical signal (SIGNAL IN) to be gated of a third wavelength. A gain medium is arranged to receive the signals SIGNAL IN, ON and OFF from the input stage. The gain medium (e.g. YAG) comprises a transition metal dopant (e.g. Cr4+) that has an excited state populatable by the first control signal and depopulatable by the second control signal to allow selective amplification of the optical signal to be gated by stimulated emission from the excited state responsive to the control signals. The amplification process has a very fast switch-on time that is several orders of magnitude faster than in prior art devices based on the rare earth dopant Er3+.

Abstract: An optical selector for an asynchronous transfer mode (ATM) optical network, the said selector being capable of selecting ATM cells of bits having a frequency of arrival f less than or equal to a predetermined frequency (PCR), the said optical selector comprising: an input having a first device capable of blocking the entry of bits; an output having a second device capable of permitting the outflow of bits; an ATM cell recognition unit constructed in such a way that it recognizes the headers of ATM cells and connected to the said input and to the said output for the transit of bits from the said input to the said output; and an optical decision unit connected operationally to the said first device, to the said second device and the said ATM cell recognition unit.

Abstract: The invention relates to new polymers useful in non linear optical (NLO) applications, particularly as optical waveguide materials.

Abstract: An optical device comprises an input for an input optical impulse and an optical beam splitting element for supplying, from the input optical impulse, a first pair and a second pair of optical impulses. Also included is a first optical delay element to delay, by a predetermined time, at least one of the first pair of optical impulses and a second optical delay element to delay, by a predetermined time, at least one of the second pair of optical impulses. A first optical processing element supplies a first output optical signal to a first output when commanded by the first pair of optical impulses and a second optical processing element supplies a second output optical signal to a second output when commanded by the second pair of optical impulses.