Noninvasive blood glucose monitoring in the 2.0-2.5 μm wavelength range

In the 1.5-1.8 μm range the glucose absorption signature is weak and not distinct. Tunable laser sources or arrays of laser diodes can eliminate the low signal limitation, even with modest powers narrow linewidths are not important, but wavelength stability (for lasers in an array) or wavelength reproducibility (for a tunable system) is critical. Successful noninvasive measurements will likely require very large signal-to-noise-ratios, so wavelength deviations must be very small