In high data rate receivers, comprising a photodetector (PD) and a transimpedance amplifier (TIA), a transmitted optical signal typically has poor extinction ratio, which translates into a small modulated current with a large DC current at the output of the PD. The large DC current saturates the TIA, which significantly degrades the gain and bandwidth performance. Accordingly, cancelling photo diode DC current in high data rate receivers is important for proper receiver operation. A DC current cancellation loop, comprising a low pass filter section and a trans-conductance cell (GM) are connected to the input of the TIA. PD DC current I.sub.DC is drawn from the input node of the TIA in the GM cell, such that the cancellation loop maintains the DC voltage value of the TIA input node to be the same as a reference voltage (V.sub.REF).

A receiver circuit includes: a constant current circuit to generate second paired current signals according to first paired current signals; a current splitter circuit to output third differential signals having amplitudes smaller than the second paired current signals, from a first and second output nodes; first and second load resistor elements connected between a DC voltage node and the first and second output nodes, respectively; a differential transimpedance amplifier circuit to output paired voltage signals according to the third paired current signals, from first and second output terminals; and a voltage regulator circuit to adjust a gate voltage of an FET connected between a power supply wire and the DC voltage node, so as to reduce at least a difference in respective average potentials of the first and second output nodes and the first and second output terminals.

Embodiments herein relate to an optical system coupled with or including a control logic. The control logic may be configured to identify, based on feedback provided by a photodiode (PD) of an optical receiver, that an amplitude of an optical marker signal output by an interferometer of the optical receiver is above a threshold value. The control logic may further be configured to adjust, based on the identification, a thermo-optic phase tuner of the interferometer, wherein adjustment of the thermo-optic phase tuner results in a change to the amplitude of the optical marker signal. Other embodiments may be described and/or claimed.

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 or optoelectronic receiver, an optoelectronic transceiver including the same, and a method and system for protecting a photodetector in the same are disclosed. The method of protecting a photodetector generally includes providing a control voltage to the photodetector so that a current flows through the photodetector, and determining that a transient event has occurred or a transient state exists in the receiver. During the transient event or transient state, the method maintains the control voltage at a normal operating voltage when the current through the photodetector is at or below a predetermined threshold current, and switches the control voltage to a safe mode voltage when the current through the photodetector is above the predetermined threshold current.

An optical communication apparatus according to an embodiment of the present invention includes: a light emitting element; a transmission driver that drives the light emitting element; a light receiving element capable of changing a multiplication factor by a bias voltage; a temperature sensor; a computing unit that calculates a drive rate of the transmission driver; and an adjusting unit that adjusts the bias voltage applied to the light receiving element. The adjusting unit adjusts the bias voltage by linear computation using a plurality of target values of the bias voltage for combinations of a plurality of temperatures and a plurality of drive rates, based on a temperature detected by the temperature sensor and a result of calculation of the drive rate.

High-performance ultra-wideband Phased Array Sensors (PAS) are disclosed, which have unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for a Receive PAS are provided by wafer scale photonic integration including heterogeneous integration of III-V materials and ultra-low-loss silicon nitride waveguides, combining key component technologies into complex PIC devices. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors providing the capability to combine many RF photonic signals with very low loss. The architecture also includes optical down-conversion, as well as digital signal processing to improve the linearity of the system. Simultaneous multi-channel beamforming is achieved through optical power splitting of optical signals to create multiple exact replicas of the signals that are then processed independently.

A circuit may include amplifier circuitry configured to receive a current signal at an amplifier input node, convert the current signal to a voltage signal, and output the voltage signal at an amplifier output node. The circuit may also include overload circuitry configured to receive a replica DC input voltage and a replica DC output voltage. The overload circuitry may be further configured to detect that the current signal exceeds a threshold level based on the replica DC input voltage and the replica DC output voltage. In addition, the overload circuitry may be configured to, in response to and based on detecting that the current signal exceeds the threshold level, direct DC current of the current signal through a DC shunt path and direct AC current of the current signal through an AC shunt path. The AC shunt path may be different from the DC shunt path.

A transimpedance amplifier connectable to a light receiving element includes a bias terminal for suppling bias potential to the light receiving element, an input terminal to receive a signal from the light receiving element and a ground terminal. The bias terminal, the input terminal and the ground terminal are arranged on at one side of the transimpedance amplifier facing the light receiving element.

The present disclosure provides an optical module comprising: a photoelectric conversion unit, a first demodulation circuit, and a second demodulation circuit; the first demodulation circuit and the second demodulation circuit are respectively connected to the photoelectric conversion unit; the photoelectric conversion unit is configured to convert the received optical signal into an electrical signal; the first demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a high-frequency electrical signal; the second demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a low-frequency electrical signal.