Patent ID: 6930300

Claim:
An apparatus for monitoring a photo-detector in an optical receiver, the apparatus comprising: a sense transistor of a bipolar type and a mirror transistor of a bipolar type connected in a mirror configuration, the sense transistor sensing a photo-detector current and the mirror transistor mirroring the photo-detector current with a mirror current; a first non-linear isolation element with a first terminal and a second terminal, the first terminal coupled to a collector of the mirror transistor and the second terminal connected to a monitor node, the first non-linear isolation element exhibiting a non-linear voltage drop between the first terminal and the second terminal in response to varying levels of the mirror current to improve compliance between the mirror current and the detector current; an operational amplifier connected with the monitor node that generates a monitor voltage in response to the mirror current, the operational amplifier receiving the monitor voltage to generate an amplified output proportional to the mirror current that is converted to a digital signal output by an analog to digital converter; and a microcontroller that uses the digital signal output to perform diagnostics for an optical receiver.