We aimed to measure signal precision, repeatability, and stability of the sensor. Here precision is defined as the variation of signal in comparison to the mean of a series of repeat measurements. Repeatability is defined as the measurements made on the same object after setting up a sensing system, performing measurements, disassembling the setup, reassembling the system, and again performing measurements. Stability is defined as long-term (greater than 20 min) sensing with the same sensor of a fixed object. To do this, we performed experiments using both a solid, silicon tissue-simulating phantom [Fig. 2(a)] as well as mice. The phantom mimics tissue light scattering without absorption or autofluorescence in the NIR range, whereas the mouse exhibits light scattering with a small amount of autofluorescence. We designated the same two sensors to be used for all experiments as “S1” or “S2,” each containing two detectors referred to “D1” and “D2.” We placed the sensor into direct contact with the phantom or mouse to characterize noise due to back-scattered excitation light [Fig. 2(b)]. Precision ranged from 0.291% to 0.941% for S1 and S2 sensors for open (no phantom), phantom, and live mouse conditions (Table 1, coefficient of variation, CV%, measurements), and similar results were obtained in several experiments. Repeatability ranged from 9.7% to 23.87% for the phantom condition, and 7.28% to 14.07% for the live mouse case for both sensors [Fig. 2(c) and 2(d), Table 2, (open and phantom), mice, CV%,). For signal stability, we measured the signal for 20 min, and in some cases we performed sensing for as long as 60 min [Fig. 2(e), ]. We calculated CV% as a measure of variation with time. For the open (no phantom) condition, the CV% was for S1D1, and for S1D2. For the phantom condition, the CV% was for S1D1 and for S1D2. For the live mouse condition, the CV% was for S1D1 and for S1D2 (Table 3, ). To illustrate differences in signal between individual mice, we plotted data from both detectors in each sensor in two mice [Fig. 2(f)]. Each detector value changes when comparing the first mouse to the second mouse. We compared the mean values for all mice by plotting the for both the S1 sensor and the S2 sensor for each mouse [Figs. 2(g) and 2(h), ]. The mean values for the S1 sensor were (D1) and (D2), and the values were significantly different (). The mean values for the S2 sensor were (D1) and (D2), and these values were significantly different (). Thus the S1 sensor the signal from D1 was always higher than at D2, whereas for the S2 sensor, the signal at D2 was always higher than D1. Thus we report a precise, stable, and repeatable signal, along with a statistically significant difference between the detectors in each sensor for live mouse sensing.