An optical power and gain detection apparatus including multiple optical power detection circuits, an FPGA device, and a temperature detection circuit. Various optical power detection circuits include a respective independent photoelectric converter, a trans-impedance amplifier, an analog signal conditioning circuit, a filter and an analog-digital conversion chip. By improving an analog circuit, digital detection and control in an optical amplifier, the property of the FPGA device may be used to realize the detection of optical signal and gain in a burst mode, avoid increasing complicated analogue circuits, and avoid the influence caused by element inconsistency in an analogue control solution. Whether the optical signal is in a stable mode or in a burst mode, the algorithm can detect the optical power accurately and stably, with a wide application range. By strictly controlling the synchronism of ADC sampling and the delay of calculation, the amplifier gain may be calculated more accurately.

An IC for power conversion includes bias circuitry that generates one or more bias voltages. An adaptive biasing circuit adaptively shifts an input signal having a negative value to a positive value. An operational transconductance amplifier (OTA) receives a supply bias current and the first and second bias voltages. The OTA has first and second input terminals coupled to the input signal and ground, respectively. The OTA has first and second transistors coupled to the first and second input terminals through first and second resistors at first and second internal nodes, respectively. Additional circuitry of the OTA is coupled to the second internal node. The additional circuitry insures that the voltage at the second internal node follows the voltage at the first internal node. The OTA generates an output current signal responsive to a differential input voltage applied across the first and second input terminals.

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.

A system for controlling convergence of gain to a target value for a variable gain amplifier comprising a detector module configured to determine a magnitude value of a variable gain amplifier output. Also, part of this embodiment is a comparator module configured to compare the magnitude value to a target value and responsive to the comparison, generate an up_dn signal. A digital control module is configured to receive the up_dn signal and processes the up_dn signal to generate a control vector. One or more digital to analog converters are configured to convert the control vector to an analog control signal such that the analog control signal controls the gain of the variable gain amplifier. Various methods of operation exist for this hardware configured to improve convergence time to a target gain value while controlling the rate of change of the gain.

Described herein are systems and methods that manage polarization in coherent optical receivers by using analog signal processing that eliminates the need for ultra-fast, power-hungry ADCs and DSPs and that would require digitization of the full-bandwidth signal path and result in bulky and expensive circuit designs. Various embodiments of the invention provide polarization correction by using an analog polarization correction circuit that implements the equivalent of two matrix operations. This is accomplished by using analog electronics that comprises a combination of variable and unity gain amplifiers to align polarizations of input signals to generate a polarization-corrected output signal that is further aligned with the polarization frame of reference of the receiver.

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.

The present disclosure provides for process and temperature compensation in a transimpedance amplifier (TIA) using a dual replica via monitoring an output of a first TIA (transimpedance amplifier) and a second TIA; configuring a first gain level of the first TIA based on a feedback resistance and a reference current applied at an input to the first TIA; configuring a second gain level of the second TIA and a third TIA based on a control voltage; and amplifying a received electrical current to generate an output voltage using the third TIA according to the second gain level. In some embodiments, one or both of the second TIA and the third TIA include a configurable feedback impedance used in compensating for changes in the second gain level due to a temperature of the respective second or third TIA via the configurable feedback impedance of the respective second or third TIA.

The present disclosure provides a trans-impedance amplifier, comprising: an inverting amplifier circuit, having an input end and an output end. The input end is coupled to an optical diode and is used for accessing an input voltage signal, and the output end is used for outputting an amplified voltage signal. The inverting amplifier circuit comprises at least three sequentially-connected amplifier units. Each of the amplifier units comprises two mutually-coupled N-type transistors, wherein one N-type transistor is used for receiving an input voltage, and the other N-type transistor is used for receiving a DC voltage signal. A common connection end of the two N-type transistors is used for outputting an amplified voltage signal, and the N-type transistor used for receiving the DC voltage signal adopts a native NFET. The trans-impedance amplifier further comprises a feedback resistor coupled to the input end and the output end of the inverting amplifier circuit.

An automatic gain control (AGC) transimpedance amplifier (TIA) uses a differential structure with feedback PIN diodes to adjust the loop gain of the amplifier automatically to maintain stability over a wide dynamic range when converting optical power using a photodiode to an electrical signal. A stable DC current derived from the photodiode current sets the voltage gain of the amplifier. The use of ultra-linear long carrier lifetime PIN diodes assures the transimpedance feedback resistance is linear. The AGC function adjusts the gain of the TIA to provide a linear stable differential transresistance controlled by the photodiode current; a linear stable AGC function using current supplied by the photodiode; an improvement of about 10 db of the transresistance dynamic range; and reduces the need for internal and external circuitry needed to provide the same function. The TIA is applicable to CATV optical systems which have very strict linearity requirements.

This invention relates to a optical receiver circuit (200) comprising: at least one photo detector (207) configured to convert a received light signal to an input current signal, a transimpedance amplifier circuit (201) with an input to receive the input current signal from the at least one photo detector (207) and being configured to convert the received input current signal to an output voltage signal to generate an output signal of the transimpedance amplifier circuit (201), wherein the transimpedance amplifier circuit comprises a plurality of gain amplifier stages (209, 210, 211), a DC restoration component (205), wherein the DC restoration component (205) is configured to receive the output voltage signal of the transimpedance amplifier circuit (201) for restoring the DC component of the received current signal and configured for outputting a corresponding current signal, and an automatic gain control component (204) configured for controlling via at least one programmable feedback resistor (226, 227) the equivalent transimpedance of the transimpedance amplifier circuit based on the signal output by the DC restoration component (205) to provide a constant output voltage amplitude for different current ranges of the input current signal.