Dual-amplifier circuit for optical signals

A method for providing a dual-path amplification of an optical input signal for optical measurements, the method comprising:

• receiving, from a photodiode, the optical input signal at an input of a first amplification path, wherein the first amplification path comprises only a first logarithmic amplifier;
• receiving, from the photodiode, the optical input signal at an input of a second amplification path, wherein the second amplification path comprises a linear amplifier circuit coupled in series with a second logarithmic amplifier circuit;
• selecting, using a selection circuit,
• an output of the second amplification path while the optical input signal is increasing and below a first power threshold, wherein the first power threshold is selected based on a beginning of a saturation level of the linear amplifier circuit,
• an output of the first amplification path while the optical input signal is increasing above the first power threshold to reach a peak and is decreasing after the peak and above a second power threshold, wherein the second power threshold is selected based on an ending of the saturation level of the linear amplifier circuit, and wherein the first power threshold is different from the second power threshold, and
• the output of the second amplification path again while the optical input signal is decreasing and below the second power threshold;
• and
• providing, by the selection circuit, the selected outputs to a measurement device.

An optical measurement system, comprising:

• a photodiode to detect an optical signal and, responsive to the detected optical signal, provide a photocurrent signal;
• an amplification block to amplify the photocurrent signal, the amplification block comprising:
• a first amplification path comprising only a first logarithmic amplifier circuit to receive the photocurrent signal;
• and
• a second amplification path comprising a linear amplifier circuit and a second logarithmic amplifier circuit coupled in series with the linear amplifier circuit, wherein the linear amplifier circuit is to receive the photocurrent signal;
• a sampling circuit to:
• receive an output of the first amplification path and an output of the second amplification path;
• and
• sample the output of the first amplification path and the output of the second amplification path;
• and
• a selection circuit to:
• select the sampled output of the second amplification path while the photocurrent signal is increasing and below a first power threshold, wherein the first power threshold is selected based on a beginning of a saturation level of the linear amplifier circuit;
• select the sampled output of the first amplification path while the photocurrent signal is increasing above the first power threshold to reach a peak and is decreasing after the peak and above a second power threshold, wherein the second power threshold is selected based on an ending of the saturation level of the linear amplifier circuit;
• select the sampled output of the second amplification path again while the photocurrent signal is decreasing and below the second power threshold;
• and
• provide the selected sampled outputs to a measurement device of the optical measurement system.