Described herein is an electronic device, including a pixel and a turn-off circuit. The pixel includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage node and an anode selectively coupled to ground through an enable circuit, and a clamp diode having an anode coupled to the anode of the SPAD and a cathode coupled to a turn-off voltage node. The turn-off circuit includes a sense circuit coupled between the turn-off voltage node and ground and configured to generate a feedback voltage, and a regulation circuit configured to sink current from the turn-off voltage node to ground based upon the feedback voltage such that a voltage at the turn-off voltage node maintains generally constant.

Provided are an apparatus and method of generating a terahertz (THz) signal using a directly-modulated laser. An apparatus of generating a THz signal includes a first directly-modulated laser configured to output a local oscillator (LO) signal, a second directly-modulated laser configured to receive a baseband signal used as data and optically modulate the baseband signal, a band-pass filter configured to filter a spectral component of the baseband signal optically modulated and outputted through the second directly-modulated laser by using a specific frequency bandwidth, a coupler configured to couple the baseband signal filtered through the band-pass filter and the LO signal to each other, and a uni-travelling-carrier photodiode (UTC-PD) configured to generate a THz signal by beating the baseband signal and the LO signal coupled to each other.

Systems and methods are described for transmitting information optically. For instance, a system may include an optical source configured to generate a beam of light. The system may include at least one modulator configured to encode data on the beam of light to produce an encoded beam of light/encoded plurality of pulses. The system may include a spectrally-equalizing amplifier configured to receive the encoded beam of light/encoded plurality of pulses from the at least one modulator and both amplify and filter the encoded beam of light/encoded plurality of pulses to produce a filtered beam of light/filtered plurality of pulses, thereby spectrally equalizing a gain applied to the encoded beam of light. In some cases, the system may slice the beam of slight, to ensure a detector has impulsive detection. In some cases, the system may include a temperature controller to shift a distribution curve of wavelengths of the optical source.

An optical receiver capable of substantially measuring the phase and amplitude of a received intensity- or amplitude-modulated optical signal by performing digital-signal processing. In an example embodiment, a DSP of the receiver operates to reduce the detrimental effects of relative phase noise between the optical reference oscillator and optical carrier based on an optical pilot present in the received optical signal. The DSP may employ a sequence of digital filters configured to select a signal component that represents a non-vestigial modulation sideband and then perform signal equalization thereon. The signal equalization may include but is not limited to dispersion compensation. In some embodiments, the optical receiver can be a direct-detection optical receiver. In an example embodiment, the optical reference oscillator and optical carrier are generated using two respective independently running lasers that may or may not be co-located.

The present invention provides an optical transmitter including a semiconductor laser and a control method thereof for preventing crosstalk between channels in an NG-PON2 with a 100 GHz channel spacing by reducing a wavelength drift of the semiconductor laser. The wavelength drift occurs between a few nanoseconds and a few hundreds of nanoseconds from the beginning of a burst when the semiconductor laser is operated in a burst-mode.

An optical receiver includes a photodiode, a transimpedance amplifier (TIA), a slope detection circuit, and a logic circuit. The TIA includes an output stage and a feedback amplifier and is coupled to the photodiode. The slope detection circuit is coupled to the feedback amplifier and configured to monitor a feedback signal from the feedback amplifier. The slope detection circuit is configured to provide, in response to a slope in the feedback signal being detected, a first slope-status signal indicating the slope is detected. The logic circuit is coupled to the slope detection circuit and is coupled to the output stage of the TIA. The logic circuit is configured to squelch the output stage of the TIA in response to the first slope-status signal.

System and methods implemented in a coherent receiver having a pair of Avalanche Photodiodes (APD) include adjusting one or more of a reverse bias voltage (VAPD) on a P-path (VAPD.sub.P) and on an N-path (VAPD.sub.N) responsive to an output (P.sub.IN,CM) that indicates electrical power of an AC common-mode input signal; adjusting a Transimpedance Amplifier (TIA) common-mode AC response, Adj.sub.CM_AC_Response, responsive to an output (P.sub.OUT,CM) that indicates electrical power of an AC common-mode output signal; and/or adjusting one or more of VAPD.sub.P and VAPD.sub.N responsive to received signal Signal-to-Noise Ratio (SNR).

An apparatus embodiment includes a remote control interface unit configured to accept an appliance control code carried in a radio frequency signal transmitted from a smart phone, extract the appliance control code from the radio frequency signal, send the extracted appliance control code to an optical frequency interface, and initiate transmission of an optical frequency signal including the appliance control code to an appliance configured to receive signals from an optical remote control.

Provided are an apparatus and method of generating a terahertz (THz) signal using a directly-modulated laser. An apparatus of generating a THz signal includes a first directly-modulated laser configured to output a local oscillator (LO) signal, a second directly-modulated laser configured to receive a baseband signal used as data and optically modulate the baseband signal, a band-pass filter configured to filter a spectral component of the baseband signal optically modulated and outputted through the second directly-modulated laser by using a specific frequency bandwidth, a coupler configured to couple the baseband signal filtered through the band-pass filter and the LO signal to each other, and a uni-travelling-carrier photodiode (UTC-PD) configured to generate a THz signal by beating the baseband signal and the LO signal coupled to each other.

An optical transmitter includes an optical modulator, a tunable optical filter, a temperature sensor, and a processor. The tunable optical filter is provided on an output side of the optical modulator and transmits light of a frequency corresponding to a control voltage. The temperature sensor detects a temperature around the tunable optical filter. The processor detects an optical loss occurring in the tunable optical filter, calculates a width of a range of the control voltage in which the detected optical loss is smaller than a specified threshold, adjusts the control voltage based on the temperature detected by the temperature sensor, and shifts the control voltage by a specified amount that is larger than zero and smaller than or equal to a half of the calculated width of the range when the optical loss is larger than or equal to the threshold.