Abstract: A switching power supply that can operate in critical conduction mode as self-oscillating power supply (SOP) during moderate load, and in discontinuous conduction mode (DCM) under the control of a pulse-width modulated signal under small load, whereby the power consumption of the supply is decreases continuously as the load is decreased. A frequency modulated self-oscillating switching power supply (FMSOP) having a power switch, the switch being held OFF, after a zero-current detector detects that an output current falls to zero, until allowed to turn ON after a pulse having a load-modulated width that corresponds to the load. The FMSOP operates with a switch controller that may include a flip-flop to latch the detector's signal, a load-modulated pulse generator, and a combinatorial logic gate to combine the pulse and the latched signal.

Abstract: A laser transmitter bias circuit for a laser diode transmitter, for use in a optical transmission system, e.g. in commercial CATV systems. The laser transmitter bias circuit reduces power consumption and heat dissipation by eliminating the conventional need for a distinct constant DC current supply for biasing the laser diode. Radio frequency (RF) circuitry, e.g., a radio frequency amplifier (e.g., a Hybrid Amplifier), connected in series to the laser diode supplies both a DC bias-current (IB) and an RF drive-current (IP) through the laser diode. The DC bias current through the laser diode in turn powers (and/or biases) the radio frequency amplifier and, optionally, other radio frequency circuitry. An optional diode-bypass current (IBP) path may be connected in parallel with the laser diode, and in series with the radio frequency amplifier to control bias current.

Abstract: A method and structure for generation of signal distortion. In a first embodiment, a first signal distortion generator (SDG) receives a pair of balanced input currents +X and −X, each having a same angular frequency &ohgr;. The first SDG generates a pair of output currents +X+&Dgr;X1 and −X+&Dgr;X2, wherein &Dgr;X1−&Dgr;X2=G2X2+G3X3. G2 and G3 are each independent of X, and at least one of G2 and G3 is nonzero. In a second embodiment, a second SDG receives an unbalanced input current P having an angular frequency &ohgr;. The second SDG generates an output current UOUT of a form P+(&agr;P+&bgr;P2+&ggr;P3)/2. &agr;, &bgr;, and &ggr; are each nonzero and each independent of P. The second SDG includes a distortion generating circuit path that has an input impedance ratio of at least 5 and an output impedance ratio of at least 5.

Abstract: A transmission lone filter having low reflectivity and Gaussian characteristics includes at least one inductive element aligned along the transmission line and at least one shunt configuration branching off the transmission line including a capacitive element and a resistive element. The transmission line filter is embodied in complete and incomplete Gaussian filters, and in both lumped element and distributed-element configurations. A method of designing a transmission line filter having low reflectivity and Gaussian characteristics is provided in which values for desired filter parameters are ascertained, formulas for the values of the inductive, capacitive and resistive elements are derived in terms of the desired filter parameters and the number of half-cells, a number of half-cells for the filter required to achieve the desired filter parameters is selected, and lumped element values for the inductive, capacitive, and resistive elements are estimated using the selected number of half-cells.

Abstract: The present invention relates generally to an amplifier such as that with the radio frequency (RF) spectrum having a nonlinear feedback loop to cancel out distortions in the input signal, and method therefor.

Abstract: A switching power supply that can operate in critical conduction mode as self-oscillating power supply (SOP) during moderate load, and in discontinuous conduction mode (DCM) under the control of a pulse-width modulated signal under small load, whereby the power consumption of the supply is decreases continuously as the load is decreased. A frequency modulated self-oscillating switching power supply (FMSOP) having a power switch, the switch being held OFF, after a zero-current detector detects that an output current falls to zero, until allowed to turn ON after a pulse having a load-modulated width that corresponds to the load. The FMSOP operates with a switch controller that may include a flip-flop to latch the detector's signal, a load-modulated pulse generator, and a combinatorial logic gate to combine the pulse and the latched signal.

Abstract: An optical signal is transmitted and received from an optical wave guide, the optical signal including an in-phase (I) component, a quadrature (Q) component and a carrier signal, and converted to an electrical signal. The electrical signal is phase-filtered to compensate for dispersion and phase locked.

Abstract: A radio frequency stabilization system (e.g., for use with a laser transmitter) in an optical communication system is provided. The present invention relates to maintaining a stable RF level in an optical link despite temperature fluctuations, including a transmitter section, a receiver section, a plurality of feedback loops connected to each of the transmitter section and the receiver section. The present invention further discloses a method of stabilizing an RF level in an optical link which method include providing an optical signal transmitter, an optical signal receiver, and a plurality of feedback loops to the optical transmitter section and the optical receiver section.

Abstract: A method and apparatus for enhancing the effective dynamic range of an RF-to-optical-to-RF link. The transmission through an optical link of RF digital signals having magnitudes outside of the dynamic range of the link is performed by changing the amplitude of (e.g., attenuating) such signals prior to transmission, and restoring such signals to their original amplitude after transmission. Signal-to-Noise Ratio (e.g., Noise Power Ratio (NPR)) of such digital signals is thereby maintained above a predetermined minimum level. The method and apparatus have advantageous applications in bi-directional commercial CATV systems.

Abstract: A method and structure for generation of signal distortion. In a first embodiment, a first signal distortion generator (SDG) receives a pair of balanced input currents +X and −X, each having a same angular frequency &ohgr;. The first SDG generates a pair of output currents +X+&Dgr;X1 and −X+&Dgr;X2, wherein &Dgr;X1−&Dgr;X2=G2X2+G3X3. G2 and G3 are each independent of X, and at least one of G2 and G3 is nonzero. In a second embodiment, a second SDG receives an unbalanced input current P having an angular frequency &ohgr;. The second SDG generates an output current UOUT of a form P+(&agr;P+&bgr;P2+&ggr;P3)/2. &agr;, &bgr;, and &ggr; are each nonzero and each independent of P. The second SDG includes a distortion generating circuit path that has an input impedance ratio of at least 5 and an output impedance ratio of at least 5.

Abstract: A laser transmitter bias circuit for a laser diode transmitter, for use in a optical transmission system, e.g. in commercial CATV systems. The laser transmitter bias circuit reduces power consumption and heat dissipation by eliminating the conventional need for a distinct constant DC current supply for biasing the laser diode. Radio frequency (RF) circuitry, e.g., a radio frequency amplifier (e.g., a Hybrid Amplifier), connected in series to the laser diode supplies both a DC bias-current (IB) and an RF drive-current (IP) through the laser diode. The DC bias current through the laser diode in turn powers (and/or biases) the radio frequency amplifier and, optionally, other radio frequency circuitry. An optional diode-bypass current (IBP) path may be connected in parallel with the laser diode, and in series with the radio frequency amplifier to control bias current.

Abstract: A cable television (CATV) distribution system, and a method of forming and using the CATV distribution system. In a first embodiment, a narrowcast optical signal is generated by an uncooled laser and converted by a receiver into a narrowcast electrical signal. In a second embodiment, a narrowcast optical signal generated by an uncooled laser is combined with a broadcast optical signal by an optical coupler at a hub of the CATV distribution system to generate a composite optical signal, which at a CATV node is: split into the broadcast and narrowcast optical components, respectively converted into broadcast and narrowcast electrical components, and combined into a composite electrical signal. In a third embodiment, a narrowcast optical signal is generated by an uncooled laser and then combined with the broadcast optical signal by a single receiver.

Abstract: Optical transmitter/receivers for use in a DWDM systems are provided. Transmission of data signals in a quadrature-return-to-zero (QRZ) format achieves a data transmission rate equal to eight times a base data rate, i.e., 80 Gbps over a 100 GHz channel if the base data rate is 10 Gbps, with high non-linear performance by setting the polarization state of the data bands such that non-linear effects induced by PMD are reduced. Additionally, a transmitter achieves a transmission data rate equal to 16 times the base data rate by sharpening the QRZ pulses and interleaving pulse-sharpened QRZ data signals in the time domain, further doubling the data rate. Using counterpropagation in the transmitter, carrier signals and data signals traverse the same length of fiber, reducing fringing effects in the transmitter. Related techniques enhance reception and detection of data at high data rates. A local pulse-sharpened carrier is mixed with a QRZ data signal at a detector reducing amplification noise by a factor of two.

Abstract: An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.

Abstract: A system and method for enhancing data capacity in optical data communication are described. First data is modulated onto a first optical carrier to occupy a data frequency range. The first optical carrier includes a first side frequency separated from the frequency range of the data band. A first modulated carrier having a first polarization state is output. Second data is modulated onto a second optical carrier signal occupying the same data frequency range. The second optical carrier includes a second side frequency separated from the data frequency range of the data band in a direction opposite from the first side frequency. A second modulated carrier having a first polarization state is output. The polarization state of the second modulated carrier is changed to a second polarization state orthogonal to the first polarization state and the first modulated carrier is combined with the second modulated carrier into a combined carrier.

Abstract: Information is optically transferred by generating an optical carrier signal having a first polarization state, generating an optical data signal separate from the optical carrier signal and having a second polarization state, matching the first polarization state and the second polarization state, combining the optical carrier signal with the optical data signal to create a combined optical signal, transferring the combined optical signal over an optical wave guide, and receiving the combined optical signal from the optical wave guide.

Abstract: A method and apparatus for controlling and stabilizing laser wavelengths in a dense wavelength division multiplexer (DWDM) transmission system. The lasers in the transmission system are each modulated in a known manner by a data signal. In addition, the lasers are each modulated by a plurality of test signals each having a predetermined frequency. At the optical receiver, a frequency analyzer examiners the frequency test signals for distortions and/or changes in amplitude. Any distortions and/or changes in amplitude of the frequency test signals indicate a change in the wavelength of a corresponding laser. A control signal may be returned to the laser controller of each laser to regulate the laser wavelength. A fault signal may be generated indicating that the wavelength of a laser has changed, drifted, etc., more an acceptable amount.

Abstract: A radiation-emitting semiconductor diode, especially a laser having a first and a second cladding layer, an active layer and a mesa which comprises at least the second cladding layer and which lies recessed in a third cladding layer. The second cladding layer comprises a first sub-layer which adjoins the active layer and is comparatively thin, and a second sub-layer which adjoins the first sub-layer and is comparatively thick, while the refractive index of the first sub-layer is lower than that of the second sub-layer. Confinement in the thickness direction of charge carriers and radiation is good in such a diode, while the third cladding layer has a relatively high refractive index (giving a relatively low bandgap). Thus, the third cladding layer has a relatively low aluminium content, while providing good lateral confinement.

Abstract: Semiconductor diode lasers are used inter alia in optical disc systems, laser printers, bar code readers, and glass fibre communication systems. Lasers having a so-called (weakly) index-guided structure are very suitable for many applications inter alia because they can be manufactured comparatively simply and reliably. A disadvantage of the known (weakly) index-guided laser is that the so-called P-I (=optical power-current) characteristic thereof exhibits a kink. Such a kink limits the use of the laser to a relatively low optical power. According to the invention, such a (weakly) index-guided laser has a resonance cavity with a length for which the optical power at which a kink occurs in the P-I characteristic is a maximum. It was a surprise to find that the occurrence of a kink in the P-I curve of such a (weakly) index-guided laser depends on the length of the resonance cavity. Very surprising is the appearance of a maximum value in this kink power as a function of the length of the resonance cavity.