Optical receiver signal strength indicator (RSSI) circuit having a variable supply voltage filter impedance

An optical receiver signal strength indicator (RSSI) circuit for use in an optical receiver or transceiver module, the RSSI circuit comprising:

• a supply voltage filter circuit electrically coupled to a supply voltage of the RSSI circuit and to an input terminal of the RSSI circuit, the supply voltage filter circuit comprising a first variable impedance device;
• a second variable impedance device that is a scaled replica of the first variable impedance device, the second variable impedance device being electrically coupled to the supply voltage;
• an operational amplifier (op-amp) having a non-inverting terminal, an inverting terminal, and an output terminal, the non-inverting terminal being electrically coupled to the input terminal of the RSSI circuit, the inverting terminal of the op-amp being electrically coupled to the second variable impedance device;
• and
• control circuitry electrically coupled to the first and second variable impedance devices, the control circuitry being configured to selectively vary an impedance value of at least the first variable impedance device based on a strength or weakness of an input current signal to the RSSI circuit, the input current signal being produced by an optical detector that is electrically coupled to the input terminal of the RSSI circuit.