A flexible sensor pad includes a cavity to hold a sensor unit with an attached cable. According to one aspect of the present invention, a light-shielding layer is coupled to a bottom surface of the sensor pad, surrounds the sensor unit, and extends past two sides of the sensor pad. A transparent adhesive layer is coupled to the light-shielding layer and extends past two sides of the light-shielding layer. Another light shielding layer is coupled to a top surface of the sensor pad and covers the sensor unit. The cable divides the sensor pad into a first side and a second side which are mirror images of each other.
