A photodiode array includes a plurality of monitoring photodiodes capable operating in a voltage mode configuration each able to provide a voltage indicating an intensity of an incident light. Integrated with the monitoring photodiodes is a reference diode configured to produce reference voltages in response to reference currents supplied to that diode. The monitoring photodiodes and the reference diode may be integrated and have the same current-voltage characteristics and the same temperature, for example by fabricating them on the same substrate. The reference diode is supplied with the reference currents in dark manner, meaning without incident light impinging on the reference diode. The resulting reference voltages, the reference source currents, and the measured photo-voltage from the monitoring photodiodes are than used to determine an optical power value at any temperature within the operation temperature range.