An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

In conventional optical receivers the dynamic range is obtained by using variable gain amplifiers (VGA) with a fixed trans-impedance amplifier (TIA) gain. To overcome the SNR problems inherent in conventional receivers an improved optical receiver comprises an automatic gain control loop for generating at least one gain control signal for controlling gain of both the VGA and the TIA. Ideally, both the resistance and the gain of the TIA are controlled by a gain control signal.

A method, an image sensor, and an image processing device for crosstalk noise reduction are proposed. The method is applicable to an image sensor having a sensing array of image sensing elements and PD sensing elements and includes the following steps. A raw image generated by the sensing array is obtained. Whether to compensate image data of a current image pixel among image pixels corresponding to the image sensing elements is determined based on a first condition associated with at least one of an exposure and a system gain of the image sensor, a second condition associated with pixel coordinates of PD pixels corresponding to the PD sensing elements, and a third condition associated with sharpness information of the raw image. The image data of the current image pixel is compensated in response to the three conditions being satisfied. A processed raw image including the compensated image data is generated.

An example optical receiver may have an optical receiver front-end, four slicers, and a logic block. The optical receiver front-end may include a transimpedance amplifier to convert a photodiode output signal to a voltage signal. Three of the slicers may be data slicers, and one of the slicers may be an edge slicer. The slicers may each: shift the voltage signal based on an offset voltage set for the respective slicer, determine whether the shifted voltage signal is greater than a threshold value and generate a number of comparison signals based on the determining, and generate multiple digital signals by demuxing the comparison signals. The logic block may perform PAM-4 to binary decoding based on the data signals output by the data slicers and clock-and-data-recovery based on the digital signals output by the edge slicer.

Methods and systems for waveguide delay based equalization summing at single-ended to differential converters in optical communication are disclosed and may include: in an photonic circuit including a directional coupler, photodetectors, and a gain stage, receiving an input optical signal; splitting the input optical signal into first and second optical signals using the directional coupler; generating a first current from the first optical signal using a first photodetector; communicating the first voltage to a first input of the gain stage; generating a second current from the second optical signal using a second photodetector; communicating the second voltage to a second input of the gain stage; and generating a differential output voltage based on the first and second currents using the gain stage.

An optical receiver circuit includes an input terminal receiving current signal from photodetector; a trans-impedance amplifier converting the current signal into voltage signal; an inductor having one end connected to the input terminal and another end connected to the input of the trans-impedance amplifier; a first variable resistor having a first end connected to the other end of the inducer a second end receiving bias voltage, and a third end receiving a control signal, where the first variable resistor varies a resistance between the first end nut the second end in accordance with the control signal; and a second variable resistor having a first end connected to the one end of the inductor, a second end receiving bias voltage, and a third end receiving a control signal, where the second variable resistor varies a resistance between the first end and the second end in accordance with Me control signal.

In optical receivers, cancelling the DC component of the incoming current is a key to increasing the receiver's effectiveness, and therefore increase the channel capacity. Ideally, the receiver includes a DC cancellation circuit for removing the DC component; however, in differential receivers an offset may be created between the output voltage components caused by the various amplifiers. Accordingly, an offset cancellation circuit is required to determine the offset and to modify the DC cancellation circuit accordingly.

In optical receivers, extending the transimpedance amplifier's (TIA) dynamic range is a key to increasing the receiver's dynamic range, and therefore increase the channel capacity. Ideally, the TIA requires controllable gain, whereby the receiver can modify the characteristics of the TIA and/or the VGA to process high power incoming signals with a defined maximum distortion, and low power incoming signals with a defined maximum noise. A solution to the problem is to provide TIA's with reconfigurable feedback resistors, which are adjustable based on the level of power, e.g. current, generated by the photodetector, and variable load resistors, which are adjustable based on the change in impedance caused by the change in the feedback resistor.

An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

In conventional optical receivers the dynamic range is obtained by using variable gain amplifiers (VGA) with a fixed trans-impedance amplifier (TIA) gain. To overcome the SNR problems inherent in conventional receivers an improved optical receiver comprises an automatic gain control loop for generating at least one gain control signal for controlling gain of both the VGA and the TIA. Ideally, both the resistance and the gain of the TIA are controlled by a gain control signal.