Abstract: An automatic gain control system for a receiver, including: an automatic gain control loop (40) adapted to be coupled to both a first transimpedance amplifier (12) coupled to a first analog-to-digital converter (14) forming a first tributary and a second transimpedance amplifier (12) coupled to a second analog-to-digital converter (14) forming a second tributary; and an offset gain control voltage to gain balance a transimpedance amplifier gain of the first tributary and a transimpedance amplifier gain of the second tributary. The automatic gain control loop can be analog. Also, the automatic gain control loop can be implemented in hardware or firmware.

Abstract: An optical link optimization includes receiving detected power outputs from one or more receivers in an optical network, wherein the detected power outputs include both a broad bandwidth power component and a low bandwidth power component; analyzing the detected power outputs to one or more of (1) balance power of a channel of interest for the one or more receivers and associated adjacent channels to a given channel of interest and (2) adjust filtering of the channel of interest for the one or more receivers and the associated adjacent channels to the given channel of interest; and configuring one or more components of the optical network to provide the one or more of (1) balance power and (2) adjust filtering.

Abstract: A coherent receiver includes a receive signal path including i) an input configured to connect a receive signal, ii) one or more signal paths connected to the input and to one or more optical hybrids, and iii) a variable optical attenuator (VOA) in each of the one or more signal paths; and a local oscillator (LO) signal path including i) an input configured to connect to an LO and the one or more optical hybrids, and ii) one or more complementary VOAs located between the input and the one or more optical hybrids, wherein the one or more complementary VOAs are configured to cancel any phase changes from the VOA in each of the one or more signal paths. The VOA in each of the one or more signal paths and the one or more complementary VOAs can be p-i-n junctions.

Abstract: Optical network devices, optical receivers, Automatic Gain Control (AGC) circuits, and power detection systems are provided for detecting power of optical signals within an optical communication system. An optical network device, according to one implementation, includes a receiver configured to receive an optical signal. The optical network device also includes a low bandwidth path configured to detect a low-band power component of the optical signal within a channel of interest and a broad bandwidth path arranged in parallel with the low bandwidth path. The broad bandwidth path is configured to detect a broad-band power component of the optical signal within broad-band channels including at least the channel of interest. A power detection output is derived from the low-band power component and the broad-band power component.

Abstract: An automatic gain control system for a receiver, including: an automatic gain control loop (40) adapted to be coupled to both a first transimpedance amplifier (12) coupled to a first analog-to-digital converter (14) forming a first tributary and a second transimpedance amplifier (12) coupled to a second analog-to-digital converter (14) forming a second tributary; and an offset gain control voltage to gain balance a transimpedance amplifier gain of the first tributary and a transimpedance amplifier gain of the second tributary. The automatic gain control loop can be analog. Also, the automatic gain control loop can be implemented in hardware or firmware.

Abstract: 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 (VAPDP) and on an N-path (VAPDN) responsive to an output (PIN,CM) that indicates electrical power of an AC common-mode input signal; adjusting a Transimpedance Amplifier (TIA) common-mode AC response, AdjCM_AC_Response, responsive to an output (POUT,CM) that indicates electrical power of an AC common-mode output signal; and/or adjusting one or more of VAPDP and VAPDN responsive to received signal Signal-to-Noise Ratio (SNR).

Abstract: Optical network devices, optical receivers, Automatic Gain Control (AGC) circuits, and power detection systems are provided for detecting power of optical signals within an optical communication system. An optical network device, according to one implementation, includes a receiver configured to receive an optical signal. The optical network device also includes a low bandwidth path configured to detect a low-band power component of the optical signal within a channel of interest and a broad bandwidth path arranged in parallel with the low bandwidth path. The broad bandwidth path is configured to detect a broad-band power component of the optical signal within broad-band channels including at least the channel of interest. A power detection output is derived from the low-band power component and the broad-band power component.

Abstract: A method and system, in an optical receiver, includes receiving a first photocurrent from a first photodetector and a second photocurrent from a second photodetector; amplifying the first photocurrent with a first amplifier to provide a first output signal and the second photocurrent with a second amplifier to provide a second output signal; adjusting a frequency response of a first path the first photocurrent and a second path of the second photocurrent; and determining a difference between the adjusted first photocurrent and the adjusted second photocurrent.

Abstract: A coherent optical modem includes one or more inputs; one or more amplifier circuits, each coupled to a respective input of the one or more inputs; and one or more receiver circuits each including an analog-to-digital converter, each coupled to a respective amplifier circuit of the one or more amplifier circuits; wherein the one or more amplifier circuits are configured to implement an automatic gain control loop to provide a constant signal amplitude at an input of the analog-to-digital converter of a respective receiver circuit.

Abstract: A coherent optical modem includes one or more inputs; one or more amplifier circuits, each coupled to a respective input of the one or more inputs; and one or more receiver circuits each including an analog-to-digital converter, each coupled to a respective amplifier circuit of the one or more amplifier circuits; wherein the one or more amplifier circuits are configured to implement an automatic gain control loop to provide a constant signal amplitude at an input of the analog-to-digital converter of a respective receiver circuit.

Abstract: A receiver gain tracking loop utilizing two Digital-to-Analog Converters (DACs) and methods for operating the gain tracking loop are provided. The gain tracking circuit includes a signal detector for detecting at least one signal and outputting a detected signal; a digital integrator connected in series to the signal detector for integrating the detected signal in the digital domain; two DACs connected in parallel to the digital integrator; and an analog summing element for summing the first digital output and the second digital output of the DACs producing a combined output.

Abstract: An amplifier circuit includes: an amplifier configured to receive at least one input signal and generate an output voltage in response to the at least one input signal and a gain control voltage; a voltage detector configured to generate a detector voltage based on the output voltage; a gain control summation circuit configured to generate an error signal by subtracting the detector voltage from a reference voltage; a loop filter configured to generate the gain control voltage based on the error signal and adjust the loop bandwidth in response to a loop filter adjust signal; and an analog automatic gain control bandwidth controller configured to monitor the detector voltage and the gain control voltage, to provide the reference voltage and the loop filter adjust signal, and to control a loop bandwidth of the output signal.

Abstract: An automatic gain control system for a receiver for an asymmetrical and/or unbalanced constellation, the system including: an automatic gain control loop adapted to be coupled to both a first transimpedance amplifier coupled to a first analog-to-digital converter forming a first tributary and a second transimpedance amplifier coupled to a second analog-to-digital converter forming a second tributary; wherein the automatic gain control loop is operable for providing an offset gain control voltage to gain balance a transimpedance amplifier voltage and a power associated with the first tributary and a transimpedance amplifier voltage and a power associated with the second tributary. The automatic gain control loop includes an analog automatic gain control loop. The automatic gain control loop is implemented in hardware or firmware.

Abstract: An amplifier circuit includes: an amplifier configured to receive at least one input signal and generate an output voltage in response to the at least one input signal and a gain control voltage; a voltage detector configured to generate a detector voltage based on the output voltage; a gain control summation circuit configured to generate an error signal by subtracting the detector voltage from a reference voltage; a loop filter configured to generate the gain control voltage based on the error signal and adjust the loop bandwidth in response to a loop filter adjust signal; and an analog automatic gain control bandwidth controller configured to monitor the detector voltage and the gain control voltage, to provide the reference voltage and the loop filter adjust signal, and to control a loop bandwidth of the output signal.

Abstract: A method and system, in an optical receiver, includes receiving a first photocurrent from a first photodetector and a second photocurrent from a second photodetector; amplifying the first photocurrent with a first amplifier to provide a first output signal and the second photocurrent with a second amplifier to provide a second output signal; adjusting a frequency response of a first path the first photocurrent and a second path of the second photocurrent; and determining a difference between the adjusted first photocurrent and the adjusted second photocurrent.

Abstract: A method. The method may include transmitting an optical noise signal to a first photodetector and a second photodetector within an optical receiver circuit that includes a transimpedance amplifier circuit. The method may further include measuring, in response to transmitting the optical noise signal, a power output from the optical receiver circuit. The method may further include determining, using the power output, a difference in photodetector responsivity between the first photodetector and the second photodetector. The method may further include adjusting, using a transimpedance gain controller, an amplifier gain within the optical receiver circuit to decrease a difference in photodetector responsivity between the first photodetector and the second photodetector.

Abstract: A method. The method may include transmitting an optical noise signal to a first photodetector and a second photodetector within an optical receiver circuit that includes a transimpedance amplifier circuit. The method may further include measuring, in response to transmitting the optical noise signal, a power output from the optical receiver circuit. The method may further include determining, using the power output, a difference in photodetector responsivity between the first photodetector and the second photodetector. The method may further include adjusting, using a transimpedance gain controller, an amplifier gain within the optical receiver circuit to decrease a difference in photodetector responsivity between the first photodetector and the second photodetector.

Abstract: A method for monitoring a circuit. The method may include obtaining, using a total current monitoring device, a measurement of a current transmitted through a cathode in a photodetector circuit. The current may include a first photocurrent for a first photodetector and a second photocurrent for a second photodetector. The method may include obtaining, using a differential current monitoring device in a transimpedance amplifier circuit, a differential voltage proportional to a current difference between the first photocurrent and the second photocurrent. The transimpedance amplifier circuit may generate, using the first photocurrent and the second photocurrent, a first output signal and a second output signal. The method may include determining, using the differential voltage and the measurement of the current transmitted through the cathode, an amount of the first photocurrent and an amount of the second photocurrent.

Abstract: A method for monitoring a circuit. The method may include obtaining, using a total current monitoring device, a measurement of a current transmitted through a cathode in a photodetector circuit. The current may include a first photocurrent for a first photodetector and a second photocurrent for a second photodetector. The method may include obtaining, using a differential current monitoring device in a transimpedance amplifier circuit, a differential voltage proportional to a current difference between the first photocurrent and the second photocurrent. The transimpedance amplifier circuit may generate, using the first photocurrent and the second photocurrent, a first output signal and a second output signal. The method may include determining, using the differential voltage and the measurement of the current transmitted through the cathode, an amount of the first photocurrent and an amount of the second photocurrent.

Abstract: Techniques for controlling a light source in a wavelength division multiplexed passive optical network (WDM-PON) are disclosed. In one particular exemplary embodiment, the techniques may be realized as an apparatus for controlling a light source in a wavelength division multiplexed passive optical network (WDM-PON). The apparatus may include a digital signal processing device configured to output a pilot tone signal. The apparatus may also include an amplifier configured to modulate a modulation current and the pilot tone signal, and output an amplitude modulated signal. The apparatus may further include a capacitor configured to AC couple the amplitude modulated signal to a bias current applied to a light source; and a monitoring photodiode configured to detect an output optical signal of the light source and transmit the detected output optical signal to the digital signal processing device to control the output optical signal of the light source.