Per-port performance optimization may be provided. First, performance data may be received corresponding to each of a plurality of ports. Then it may be determined that performance of at least one of the plurality of ports can be improved based on the received performance data corresponding to the least one of the plurality of ports. Next, in response to determining that the performance of the at least one of the plurality of ports can be improved, at least one of a plurality of components may be adjusted corresponding to the at least one of the plurality of ports to improve performance of the least one of the plurality of ports.

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.

An amplifier typically exemplified by a TIA is realized that provides an optimal band characteristic, that reduces the possibility of the oscillation, and that achieves a reduced dispersion of the band characteristics. An amplifier for amplifying an electric signal, comprising: a first buffer for amplifying the electric signal; a filter that is connected to an output of the first buffer and that includes a parallel circuit consisting of an inductor and a first capacity; and a second buffer connected to an output of the filter.

An optical receiver includes a transimpedance amplifier that converts a current signal corresponding to an optical signal into a voltage signal. The transimpedance amplifier includes an input terminal receiving the current signal, an output terminal outputting the voltage signal, an inverting circuit including a pull-up device that pull-up drives the voltage signal of the output terminal according to the current signal, and a pull-down device that pull-down drives the voltage signal of the output terminal according to the current signal, a feedback resistor electrically connected between the input and output terminals, a first resistor electrically connected between the input terminal and the pull-up device, and a second resistor electrically connected between the input terminal and the pull-down device.

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.

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.

An optical receiver (1) comprises a differential TIA (4) linked with a photodiode (2, 3) providing a current sense signal (I.sub.sig_tia). The receiver is configured to provide to the TIA a sense signal as a sense TIA input (I.sub.sig_tia) and a second input (I.sub.dark_tia) which is a proportion of the maximum sense signal. The proportion input is half of said maximum sense signal. The inputs to the TIA are via cascode circuits (5, 6), thereby providing the advantages of a low input impedance for large area photodiodes at the TIA input, while creating a fully differential signal at the output, and the reduction of TIA bandwidth in burst mode applications, which filters out high frequency noise.

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.

Per-port performance optimization may be provided. First, performance data may be received corresponding to each of a plurality of ports. Then it may be determined that performance of at least one of the plurality of ports can be improved based on the received performance data corresponding to the least one of the plurality of ports. Next, in response to determining that the performance of the at least one of the plurality of ports can be improved, at least one of a plurality of components may be adjusted corresponding to the at least one of the plurality of ports to improve performance of the least one of the plurality of ports.