Abstract: Systems and methods in accordance with embodiments of the invention transmit and detect electromagnetic signals using an offset IQ modulation technique. Offset IQ modulation systems use a digital to analog converter to generate a transmitted waveform that is frequency offset from direct current by an amount equal or larger than half the signal bandwidth, so that the level of any local oscillator leakage present within the frequency band containing the transmitted signal is insignificant. When the transmitted signal is received, an IQ mixer is also used to down convert the received signal. In many embodiments, the down converted signal is over sampled and provided to a digital signal processing system to perform linear filtering to remove intermodulation and/or crossmodulation components that can be introduced by nonlinearities in components such as (but not limited to) Power Amplifiers, Low Noise Amplifiers and/or the IQ mixer used during the down conversion.

Abstract: A GPON module comprises a housing and a circuit board disposed in the housing. The circuit board further includes ground lines that substantially isolate regions of the circuit board, an electro-optical interface for converting an inbound optical signal to an electrical signal and processing circuitry that is arranged to provide an electrical RF signal to an RF interface. The RF interface comprises a three-pin RF connector exposed from the housing, wherein the RF connector is coupled directly to the circuit board, and two of the three pins are coupled to ground.

Abstract: An optical communication system for generating and transmitting a modulated optical signal in which light emitted by a light source is modulated by an optical modulator in accordance with an input electrical signal. A bias signal generator applies a bias electrical signal to bias the optical modulator at a bias angle away from quadrature. The bias signal generator monitors the input electrical signal and adjusts the applied bias electrical signal in dependence on the input electrical signal. The system further includes a receiver which may include an equalizer coupled to the photodetector of the receiver.

Abstract: An optical communication system for generating and transmitting a modulated optical signal in which light emitted by a light source is modulated by an optical modulator in accordance with an input electrical signal. A bias signal generator applies a bias electrical signal to bias the optical modulator at a bias angle away from quadrature. The bias signal generator monitors the input electrical signal and adjusts the applied bias electrical signal in dependence on the input electrical signal. The system further includes a receiver which may include an equalizer coupled to the photodetector of the receiver.

Abstract: A GPON module comprises a housing and a circuit board disposed in the housing. The circuit board further includes ground lines that substantially isolate regions of the circuit board, an electro-optical interface for converting an inbound optical signal to an electrical signal and processing circuitry that is arranged to provide an electrical RF signal to an RF interface. The RF interface comprises a three-pin RF connector exposed from the housing, wherein the RF connector is coupled directly to the circuit board, and two of the three pins are coupled to ground.

Abstract: A passive optical network transceiver includes an avalanche photodiode, a bias voltage generator for supplying a bias voltage to the avalanche photodiode, a temperature detector for measuring the operating temperature of the avalanche photodiode, a memory for storing one reference bias voltage and a processing circuitry to process the value of the measured operating temperature and the reference bias voltage to generate a control signal for controlling the bias voltage generator to adjust the bias voltage supplied by the said bias voltage generator.

Abstract: A distortion circuit is provided for correcting the distortion from a nonlinear circuit element by generating a frequency dependent signal having a sign opposite to the distortion signal produced by the nonlinear circuit and substantially the same magnitude. The distortion circuit includes an input signal and a first nonlinear device coupled to the input signal for generating a first signal and where the first nonlinear device has a first bias level. Also included is a second nonlinear device different from same first nonlinear device and coupled to the first nonlinear device for modifying the first signal to produce an output second signal, the second nonlinear device having a second bias level. A bias control means is provided for adjusting the first and said second bias levels so that the magnitude, phase and frequency of the output second signal can be adjusted.

Abstract: A passive optical network transceiver includes an avalanche photodiode, a bias voltage generator for supplying a bias voltage to the avalanche photodiode, a temperature detector for measuring the operating temperature of the avalanche photodiode, a memory for storing one reference bias voltage and a processing circuitry to process the value of the measured operating temperature and the reference bias voltage to generate a control signal for controlling the bias voltage generator to adjust the bias voltage supplied by the said bias voltage generator.

Abstract: An optical receiver having a photodetector coupled to an external optical fiber for receiving an optical communications signal and converting it into an electrical signal; an RF amplifier coupled to the electrical output of the photodetector and generating an output signal with distortion; and a post-distortion circuit connected to the output of the RF amplifier for canceling the distortion in the output signal produced by the RF amplifier.

Abstract: A distortion circuit is provided for correcting the distortion from a nonlinear circuit element by generating a frequency dependent signal having a sign opposite to the distortion signal produced by the nonlinear circuit and substantially the same magnitude. The distortion circuit includes an input signal and a first nonlinear device coupled to the input signal for generating a first signal and where the first nonlinear device has a first bias level. Also included is a second nonlinear device different from same first nonlinear device and coupled to the first nonlinear device for modifying the first signal to produce an output second signal, the second nonlinear device having a second bias level. A bias control means is provided for adjusting the first and said second bias levels so that the magnitude, phase and frequency of the output second signal can be adjusted.

Abstract: An optical receiver having a photodetector coupled to an external optical fiber for receiving an optical communications signal and converting it into an electrical signal; an RF amplifier coupled to the electrical output of the photodetector and generating an output signal with distortion; and a post-distortion circuit connected to the output of the RF amplifier for canceling the distortion in the output signal produced by the RF amplifier.

Abstract: An optical receiver for use in an optical communications system in which an analog signal is transmitted over an optical fiber including a housing with a photodetector coupled to the external optical fiber for receiving an optical communications signal; and a transimpedance amplifier coupled to the electrical output of the photodetector and having a bias current in a second stage set to a predetermined value that minimizes the distortion in the output signal created in a first amplification stage by a cancellation effect.

Abstract: An optical interface between an optical fiber and a laser is provided. The optical fiber has a core and an end. The optical interface includes a mirror that is capable of receiving an optical output of the laser and of reflecting the optical output to the end of the optical fiber such that a chief ray of the optical output is incident on the core of the optical fiber. The optical interface also includes a lens located such that the chief ray of the optical output traverses a center of the lens. Such optical interface may be used in a transmitter optical subassembly (TOSA) having a vertical TO package for un-cooled lasers.

Abstract: An optical transmitter includes a laser driver capable of receiving data and applying the data to drive a laser diode over a transmission line having first and second ends. The first end of the transmission line is coupled to an output of the laser driver. A first terminal of an amplifier is coupled to the second end of the transmission line. A second terminal of the amplifier is coupled to the laser diode. The signal amplitude applied at the first terminal controls optical output amplitude of the laser diode.

Abstract: A high performance transmission optical subassembly is disclosed. The transmission optical subassembly includes a laser diode transmitting an optical transmission beam from a first facet of the laser diode. A reflective mirror reflects a first portion of the optical transmission beam to an end face of an optical fiber and an edge illumination monitor photodetector, having a light receiving facet that receives a second portion of the optical transmission beam, produces a laser diode control signal as a function of the received second portion of the optical transmission beam.

Abstract: An optical interface between an optical fiber and a laser is provided. The optical fiber has a core and an end. The optical interface includes a mirror that is capable of receiving an optical output of the laser and of reflecting the optical output to the end of the optical fiber such that a chief ray of the optical output is incident on the core of the optical fiber. The optical interface also includes a lens located such that the chief ray of the optical output traverses a center of the lens. Such optical interface may be used in a transmitter optical subassembly (TOSA) having a vertical TO package for un-cooled lasers.

Abstract: An optical transmitter includes a laser driver capable of receiving data and applying the data to drive a laser diode over a transmission line having first and second ends. The first end of the transmission line is coupled to an output of the laser driver. A first terminal of an amplifier is coupled to the second end of the transmission line. A second terminal of the amplifier is coupled to the laser diode. The signal amplitude applied at the first terminal controls optical output amplitude of the laser diode.

Abstract: A circuit for, and method of, measuring an extinction ratio of a laser diode and a laser diode transmitter incorporating the circuit or the method. In one embodiment, the circuit includes: (1) an RF power detector, optically couplable to an output of the laser diode, for producing a varying voltage that is a function of an AC portion of modulated power generated by the laser diode and (2) an error signal generator, coupled to the power detector, for integrating the varying voltage over time to yield an integrated DC voltage that is a function of the extinction ratio.

Abstract: Optical waveguide devices based on optical coupling of different modes by using a mediating mode. Such waveguide devices generally have at least two coupling regions. The first coupling region couples an output mode and the mediating mode, and the second one couples the mediating mode and an input mode that copropagates with the output mode. Under proper conditions, the energy in the input mode can be completely transferred to the output mode, without energy loss to the mediating mode.