Embodiments of the invention are directed to a photoplethysmogram (PPG) structure that includes a wearable component and a network of PPG sensors physically coupled to the wearable component. Each PPG sensor of the network includes a housing, a first light source and a light detector. The first light source is positioned in or on the housing such that, when the housing is positioned on a surface, the housing positions an illuminating surface of the first light source at a predetermined first-light-source angle with respect to the surface.
