JOIN: Optimized Light Source Activation for Deep Tissue Optical Sensing

In wearable optical sensing systems, non-idealities present during measurement affect the quality of acquired signals of interest. The issue is of particular significance in deep tissue sensing applications in which the signal of interest is faint relative to typical noise sources that contaminate the measured data. To mitigate the problem, we investigate the role of optimizing the light source activation pulse, specifically its toggling rate and duty cycle. We identify the potential for the optical source activation signal to mitigate the problem and characterize its design space. Subsequently, we present JOIN, an algorithm that yields the parameters of an optimized activation signal for a given profile of contextual noise profile. Through this algorithm, we strike a balance between avoiding noisy spectral regions associated with environmental disturbances and fitting a judiciously-selected number of signal harmonics into the measurement bandwidth, thereby enhancing the signal-to-noise ratio (SNR) of the acquired data from deep tissue by as much as $6dB$ . The proposed method is validated through analytical derivations, as well as test bench and in-vivo measurements on human subjects.