Method and system for estimating distance between a fiber end and a target

At least one non-transitory computer-readable medium comprising a set of instructions that, in response to being executed by a processor circuit, cause the processor circuit to:

• determine a first intensity value based on first reflected laser light corresponding to laser light of a first wavelength, wherein the laser light of the first wavelength exits a distal end of an optical fiber and the first reflected laser light is reflected by a target and enters the distal end of the optical fiber;
• determine a second intensity value based on second reflected laser light corresponding to laser light of a second wavelength different from the first wavelength, wherein the laser light of the second wavelength exits the distal end of the optical fiber and the second reflected laser light is reflected by the target and enters the distal end of the optical fiber;
• derive an adjusted first intensity value based on subtracting a first internal reflection values from the first intensity value,
• derive an adjusted second intensity value based on subtracting a second internal reflection values from the second intensity value, and
• compute a ratio of the adjusted first intensity value and the adjusted second intensity value;
• and
• estimate a distance between the distal end of the optical fiber and the target based on the ratio of the adjusted first intensity value and the adjusted second intensity value,
• wherein the first wavelength has a first water absorption coefficient higher than a second water absorption coefficient of the second wavelength.

A method, comprising:

• illuminating a target with laser light of a plurality of different wavelengths;
• receiving reflected light beams from the target via an optical fiber;
• measuring intensity of the reflected light beams with one or more light detectors, comprising at least:
• measuring a first intensity value of the reflected light beams corresponding to laser light of a first wavelength, and
• measuring a second intensity value of the reflected light beams corresponding to laser light of a second wavelength different from the first wavelength;
• deriving an adjusted first intensity value based on subtracting a first internal reflection values from the first intensity value;
• deriving an adjusted second intensity value based on subtracting a second internal reflection values from the second intensity value;
• computing a ratio of the adjusted first intensity value and the adjusted second intensity value;
• and
• estimating a distance between a distal end of the optical fiber and the target based on the ratio,
• wherein the first wavelength has a first water absorption coefficient higher than a second water absorption coefficient of the second wavelength.