Abstract: An apparatus to measure optical characteristics of an optical medium may include an optical source to generate an optical square wave for transmission into the optical medium and an optical receiver to receive a reflected optical waveform from the optical medium caused by a portion of the optical square wave being reflected by any anomaly in the optical medium. The optical receiver may convert the reflected optical waveform to a reflected electrical waveform. The apparatus may also include a module to combine the reflected electrical waveform with a reference waveform to form a resulting waveform. The reference waveform may correspond substantially to the optical square wave and may be delayed a predetermined time duration. A controller may be included to process the resulting waveform to detect any anomaly and a location of the anomaly in the optical medium based on an amplitude of the resulting waveform at a sample delay position in the resulting waveform.

Abstract: A power diagnostic system and method for detecting faults is provided. The system includes a processor coupled to a plurality of sampling blocks; wherein the plurality of sampling blocks simultaneously perform current measurements and voltage measurements at a plurality of loads, based on a reference signal generated by a clock generator; wherein the sampling blocks measurements are sent to the processor via power cables that are also used to supply power to the plurality of loads. The method includes sampling currents and voltages at a power supply and at a plurality of loads; wherein the sampling is synchronized to a reference signal; transmitting sampled currents and voltages to a processor; comparing sampled currents and voltages with threshold values; and identifying faults if the sampled currents and voltages vary from the threshold values.

Abstract: A fiber optic communication system is provided that includes a light source adapted to emit a system optical signal and an electrical signal source adapted to provide a data input electrical signal. Additionally, the fiber optic communication system includes a feed forward photonic modulation circuit adapted to receive the data input electrical signal and the system optical signal and output a final modulated optical signal substantially free from residual error.

Abstract: Apparatus and methods for capacitively coupled device input/output are disclosed. In one embodiment, a connector module includes a first member having at least one first conductive lead disposed therein. A dielectric portion is coupled to an end portion of the at least one first conductive lead. A second member has at least one second conductive lead disposed therein. The first and second members are coupled such that respective end portions of the first and second conductive leads are operatively positioned and spaced apart by the dielectric portion. The dielectric portion is adapted to capacitively couple the respective end portions of the first and second conductive leads and to allow signals to be transmitted therethrough.

Abstract: A digital communications system includes a transmitter and a receiver. The transmitter is capable of quadrature amplitude modulation (QAM) encoding each bit of at least one n-bit digital signal into at least one QAM signal and thereafter transmitting the QAM signals. And the receiver is capable of receiving the QAM signals and thereafter integrating the QAM signals. The receiver includes at least one tapped-delay line filter, which can then receive the integrated QAM signals and thereafter output a representation of each bit of the at least one n-bit digital signal.

Abstract: An inexpensive optical time domain reflectometer is disclosed that comprises a variable delay device and that is capable of identifying the location of a damage portion of a fiber optic cable with great accuracy and minimal power consumption. A method of providing a vehicle with an on-board optical time domain reflectometer is also disclosed.

Abstract: Bi-directional optical signal transmission apparatus and methods are disclosed. In one embodiment, an optical detector is configured to receive an optical signal from an end of an optical fiber. An optical element is located at the detector surface and is configured to receive and direct a laser beam. A laser beam is directed by the optical element through the end into the optical fiber substantially parallel with the principal axis.

Abstract: Apparatus and methods for improved fiber optic signal transmission systems are disclosed. In one embodiment, a reflectometer includes an optical source to emit optical energy into a the fiber optic line and to generate time-delayed signals from the repetitive pulses, an optical receiver to detect reflected energy from the fiber optic line and generate reflected signals from the reflected energy, a mixer that receives the reflected signals and receives the time delayed signals to generate a product waveform from the reflected signals and the time-delayed signals, and a processor that receives the product waveform to process the waveform to generate a value based on the sampled characteristic.

Abstract: Apparatus and methods for fiber optic links having a built-in test are disclosed. In one embodiment, an optical component includes a signal source, and a controller operatively coupled to the signal source. The signal source is adapted to output a first combined optical signal having a first optical signal portion of a first frequency and a second optical signal portion of a second frequency. The first frequency is substantially greater than the second frequency. The controller is adapted to induce the signal source to output the first and second optical signal portions, the first optical signal portion being associated with a main communication function and the second optical signal portion being associated with a monitoring function.

Abstract: Methods and apparatus for detecting degradation of a fiber optic connector. In a preferred embodiment, the method includes transmitting a optical pulse in a first direction along the fiber optic cable such that a first portion of the optical pulse is either absorbed or reflected by the degradation. The method also includes determining the degradation's location within at most two connectors of the cable based on the first portion of the optical pulse. If the at most two connectors is two connectors then the method includes transmitting a second optical pulse in a second direction along the cable so that a portion of the second optical pulse is either absorbed or reflected by the degradation. A determination is made of the location of the degradation within one of the two connectors based on the first portion and the second portion of the optical pulses.

Abstract: A network system includes a network having a network bus, such as unshielded differential twisted-pair wires, electrically connected to a plurality of remote devices, and a network controller for digitally directing transmissions with the remote devices via the network bus. The network system also includes a plurality of network device interface elements adapted to interconnect the network controller with respective remote devices via the network bus. Each network device interface element includes a local oscillator, and is capable of transmitting and receiving messages via the network bus. To at least partially limit electromagnetic emissions from the local oscillator, each network device interface element further includes a spread-spectrum clock. And to further aid in limiting electromagnetic emissions, each network device interface element can further include a suppression assembly.

Abstract: A test signal attenuation circuit is built into a signal transmitter for modifying the energy content of the transmitter output signal. The built-in test signal attenuation circuit includes circuits for generating an attenuated, degraded, chopped signal. The built-in test signal attenuation circuit may be used for purposes of testing the performance of a link under degraded conditions.

Abstract: A method for introducing errors into a digital fiber optic communication link so that small analog changes in optical transmission efficiency can be determined by changes in the audible error rate. The method comprises providing a transmitter with a test channel that provides a pseudorandom encoded optical transmission through coupled fiber optic cables. The signal is sent through the cables and received by a receiver which introduces and measures errors. The received signal is split and processed by a clock recovery circuit and a lowpass filter. The clock recovery circuit obtains the optimal sampling point. The lowpass filter filters the data and provides a timing adjustment relative to the recovered clock signal. The clock retimes the filtered data with a sampling comparator. The variable timing introduces errors allowing optical transmission efficiency measurements. A bit error rate tester produces audible sounds whose frequency content is related to the bit error rate.

Abstract: Apparatus and methods for noise-feedback controlled optical systems are disclosed. In one aspect, an apparatus includes a receiver adapted to receive an optical signal and to convert the optical signal to a corresponding electrical signal, and a control circuit coupled to the receiver. The control circuit includes a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust a gain of the receiver based on the noise level. In an alternate aspect, an optical system includes a transmitter, a receiver, and a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust at least one of an amplification of the transmitter and a gain of the receiver based on the noise level.

Abstract: A matched-filter receiver includes a detector that generates a current signal based on light input thereto. An integrating circuit has an input that is connected to the detector. The integrating circuit integrates the current signal and outputs an integrated signal. A delay circuit is connected to an output of the integrating circuit. The delay circuit delays the integrated signal for a first duration. A comparator circuit includes an inverting input that is connected to the output of the integrating circuit and to an output of the delay circuit. The integrating circuit includes a resistor having a parasitic capacitance. The integrating circuit includes an amplifier circuit that amplifies the integrated signal. The duration that the delay circuit delays the integrated signal can be set to a plurality of duration values. The comparator provides an output signal having one of a first state and a second state. A decision circuit that is connected to the comparator provides a binary decision signal.

Abstract: A method for introducing errors into a digital fiber optic communication link so that small analog changes in optical transmission efficiency can be determined by changes in the audible error rate. The method comprises providing a transmitter with a test channel that provides a pseudorandom encoded optical transmission through coupled fiber optic cables. The signal is sent through the cables and received by a receiver which introduces and measures errors. The received signal is split and processed by a clock recovery circuit and a lowpass filter. The clock recovery circuit obtains the optimal sampling point. The lowpass filter filters the data and provides a timing adjustment relative to the recovered clock signal. The clock retimes the filtered data with a sampling comparator. The variable timing introduces errors allowing optical transmission efficiency measurements. A bit error rate tester produces audible sounds whose frequency content is related to the bit error rate.

Abstract: A bidirectional optical link for communication between a first data unit and a second data unit using a single optical source. In a broad aspect it includes a modulator/optical receiver system that includes a splitter element; a receiver element and a return modulator. The splitter element receives an incoming modulated optical signal from an optical source associated with a first data unit. It splits the incoming optical signal into a received optical portion and an outgoing optical portion. The receiver element detects the received optical portion and converts the received optical portion to an electrical signal to be communicated to a second data unit. The return modulator element modulates the outgoing optical portion and transmits the modulated outgoing optical portion to the first data unit. The modulation of the outgoing optical portion allows the use of a single, shared optical source.

Abstract: A network system includes a network having a network bus, such as unshielded differential twisted-pair wires, electrically connected to a plurality of remote devices, and a network controller for digitally directing transmissions with the remote devices via the network bus. The network system also includes a plurality of network device interface elements adapted to interconnect the network controller with respective remote devices via the network bus. Each network device interface element includes a local oscillator, and is capable of transmitting and receiving messages via the network bus. To at least partially limit electromagnetic emissions from the local oscillator, each network device interface element further includes a spread-spectrum clock. And to further aid in limiting electromagnetic emissions, each network device interface element can further include a suppression assembly.

Abstract: A test signal attenuation circuit built into a signal transmitter for modifying the energy content of the transmitter output signal includes means for generating an attenuated, degraded, chopped signal for purposes of testing the performance of a link under degraded conditions.

Abstract: A digital communications system includes a transmitter and a receiver. The transmitter is capable of quadrature amplitude modulation (QAM) encoding each bit of at least one n-bit digital signal into at least one QAM signal and thereafter transmitting the QAM signals. And the receiver is capable of receiving the QAM signals and thereafter integrating the QAM signals. The receiver includes at least one tapped-delay line filter, which can then receive the integrated QAM signals and thereafter output a representation of each bit of the at least one n-bit digital signal.