Abstract: It is disclosed an optical coherent receiver for an optical communication network. The optical coherent receiver is configured to receive a modulated optical signal and to process it for generating an in-phase component and a quadrature component. The optical coherent receiver comprises a power adjuster in turn comprising a multiplying unit and a retroactively connected digital circuit. The multiplying unit is configured to multiply the in-phase and quadrature components by in-phase and quadrature gains, respectively, thereby providing power-adjusted in-phase and quadrature components. The digital circuit is configured to compute: a common gain indicative of a sum of the powers of the power-adjusted in-phase and quadrature components; a differential gain indicative of a difference between the powers of the power-adjusted in-phase and quadrature components; and the in-phase and quadrature gains as a product and a ratio, respectively, between the common gain and the differential gain.

Abstract: A method and apparatus for correcting of phase errors in a coherent optical receiver are disclosed. Embodiments include a method for calculating a phase error between in-phase and quadrature-phase component signals, multiplying the phase error by one of the component signals and subtracting the result from the other component signal to output a corrected signal.

Abstract: An electrical device that comprises a tunable cavity filter that includes a container and a post. The container encloses a cavity therein, wherein interior surfaces of the container are covered with a metal layer. The post is configured be movable through an opening in the container such that at least a portion of the post is locatable inside of the cavity.

Abstract: One aspect provides an optical communication system. The system includes an optical-to-digital converter, a frequency estimator and a symbol synchronizer. The optical-to-digital converter is configured to receive an optical OFDM bit stream including an OFDM symbol bearing payload data and a symbol header preceding the OFDM payload data. The frequency estimator is configured to determine a carrier frequency offset of the payload data from the symbol header. The symbol synchronizer is configured to determine a starting location of the payload data within the bit stream by cross-correlating a synchronization pattern within the symbol header with a model synchronization pattern stored by the symbol synchronizer.

Abstract: An approach is provided that uses diversity to compensate fading of free-space optical (FSO) signals propagating through an environment characterized by atmospheric scintillation. One embodiment involves collecting at least one FSO beam, demultiplexing the beam by wavelength into at least two sub-beams, detecting each sub-beam to produce an electrical output therefrom, and recovering a signal using complementary information from at least two of the electrical outputs. Another embodiment involves collecting the FSO beam onto an array of spatially separated sub-apertures, detecting the light entering each sub-aperture to produce an electrical output therefrom, and recovering a signal using complementary information from at least two of the electrical outputs. This second embodiment enables both electronic adaptive processing to coherently integrate across the sub-apertures and in the case of multiple transmit apertures a free space optical Multiple Input Multiple Output (MIMO) system.

Abstract: A method and apparatus providing clock and data recovery within an optical receiver using three CMA FIR filters with different group delays where filter coefficients are adapted to provide for a filter exhibiting a group delay of one sample period from which symbols for further processing are provided.

Abstract: An electronic device includes a first strip conductor formed from a first metal level over a substrate. A second strip conductor formed from a second metal level is located between the first strip conductor and the substrate. At least one of the first and the second strip conductors includes a stripline portion and a microstrip line portion.

Abstract: A method for determining symbols PSK modulated on an optical carrier includes interfering a first polarization component of the modulated optical carrier and a reference optical carrier in a first optical mixer and interfering the first polarization component of the modulated optical carrier and the reference with a different relative phase in a second optical mixer. The method also includes sampling the interfered carriers from the first optical mixer to produce first digital sampled values and sampling the interfered carriers from the second optical mixer to produce second digital sampled values. The first and second digital sampled values of a sampling period form a first complex sampling value thereof. The method also includes offsetting a phase of a complex signal value corresponding to each first complex sampling value to correct for a phase error caused by a frequency offset between the modulated and reference optical carriers.

Abstract: A method and apparatus providing a tunable channelized patch antenna by selectively adjoining one or more radiating element extensions successively to a radiating element of the patch antenna, and adjusting fringe capacitance at active outer edges of the patch antenna.

Abstract: A method, apparatus and system for providing clock and data recovery in a receiver for receiving a high speed coherent polarization division multiplexed optical signal using a digital signal processing block including a spectral domain spatial combiner are provided.

Abstract: An apparatus, a polarization diversity receiver and a method of receiving a received optical signal. In one embodiment, the apparatus includes: (1) an optical device configured to separate in-phase and quadrature components of a received optical signal, to transmit the in-phase components to a first optical output thereof and to transmit the quadrature components to a second optical output thereof, (2) a first polarization splitter coupled to receive light at the first optical output and (3) a second polarization splitter coupled to receive light at the second optical output.

Abstract: A method and apparatus for correcting of phase errors in a coherent optical receiver are disclosed. Embodiments include a method for calculating a phase error between in-phase and quadrature-phase component signals, multiplying the phase error by one of the component signals and subtracting the result from the other component signal to output a corrected signal.

Abstract: An electronic device includes a first strip conductor formed from a first metal level over a substrate. A second strip conductor formed from a second metal level is located between the first strip conductor and the substrate. At least one of the first and the second strip conductors includes a stripline portion and a microstrip line portion.

Abstract: An automatic threshold voltage adjustment circuit, a method of automatically adjusting threshold voltage and an optical receiver for an optical communication system. In one embodiment, the circuit includes: (1) an amplitude detector configured to detect an amplitude of a received optical signal, (2) a variable resistor coupled to the amplitude detector and including a field-effect transistor configured to operate in a triad mode to provide a resistance that varies substantially linearly based on the amplitude and (3) an operational amplifier coupled to the variable resistor and configured to apply a variable gain based on the resistance to an input threshold voltage to yield an adapted threshold voltage.

Abstract: Tunable microstrip devices formed by capacitively coupled conductive strips are disclosed. Device parameters can be tuned by adjusting corresponding lengths of a resonator and a coupling section of the device by connecting one or more auxiliary segments to the conductive strips.

Abstract: A method and apparatus providing a tunable channelized patch antenna by selectively adjoining one or more radiating element extensions successively to a radiating element of the patch antenna, and adjusting fringe capacitance at active outer edges of the patch antenna.

Abstract: A method and apparatus providing clock and data recovery within an optical receiver using three CMA FIR filters with different group delays where filter coefficients are adapted to provide for a filter exhibiting a group delay of one sample period from which symbols for further processing are provided.

Abstract: Tunable microstrip devices formed by capacitively coupled conductive strips are disclosed. Device parameters can be tuned by adjusting corresponding lengths of a resonator and a coupling section of the device by connecting one or more auxiliary segments to the conductive strips.

Abstract: An automatic threshold voltage adjustment circuit, a method of automatically adjusting threshold voltage and an optical receiver for an optical communication system. In one embodiment, the circuit includes: (1) an amplitude detector configured to detect an amplitude of a received optical signal, (2) a variable resistor coupled to the amplitude detector and including a field-effect transistor configured to operate in a triad mode to provide a resistance that varies substantially linearly based on the amplitude and (3) an operational amplifier coupled to the variable resistor and configured to apply a variable gain based on the resistance to an input threshold voltage to yield an adapted threshold voltage.

Abstract: A method and apparatus are provided for performing electronic equalization in optical communication systems. Coefficient values in equalizers, such as feed forward equalizers or decision feedback equalizers, are updated using higher-order algorithms in the Least-Mean-2Nth-Order family. An optical receiver includes a photo-detector for converting a received optical signal to an electrical signal; and an equalizer for removing intersymbol interference from the electrical signal, wherein coefficients of the equalizer are updated based upon a least-mean 2Nth-order (LMN) algorithm (N is greater than one). Feed forward equalizer and decision feedback equalizer implementations are disclosed. The non-symmetric nature of optical noise is addressed by varying A slicer threshold based on an incoming signal distribution to reduce bit errors.