Systems and methods are provided for monitoring the physiological state of a subject. One or more physiological parameters of a subject may be determined from a photoplethysmograph (PPG) signal or signals obtained using at least one PPG sensor. In some embodiments, an electrical physiological signal (EPS) sensor may be located in or near a PPG sensor. A sensor configuration including both PPG sensors and EPS sensors may be advantageously used to detect a PPG signal or signals in combination with one or more EPS signal or signals. To reduce potential interference between an EPS sensor and a PPG sensor, fiber-optic input and output lines may be used to transmit optical signals from light generating circuitry and light detecting circuitry. In some embodiments, the generating and detecting circuitry may be located remotely from one another and may further be located remotely from the EPS sensor, PPG sensor, or both.
