Systems and methods for measuring a physiological parameter of tissue in a patient are provided herein. In a first example, tissue interface pad for applying optical signals to tissue of a patient is provided. The tissue interface pad includes a first surface configured to interface with the tissue of the patient and further includes a first guide channel disposed generally parallel to a second guide channel. The first guide channel is configured to route an input optical fiber to a first location and optically couple an end of the input optical fiber to the tissue at the first location. The second guide channel is configured to route an output optical fiber to a second location and optically couple an end of the output optical fiber to the tissue at the second location.
