Abstract: An efficient, effective, MRI compatible small bore MRI noninvasive photoplethysmographic sensor for animals such as small rodents, namely rats and mice. The photoplethysmographic sensor for animals comprising: a non-magnetic sensor coupling attachable to an animal; fiber optic cable coupled to the sensor coupling and configured to deliver a signal to and receive a signal from the animal tissue adjacent the sensor coupling; an opto-electical converter coupled to the fiber optic cable, the converter including a receiver coupled the fiber optic cable portion configured to receive a signal from the animal tissue and including an emitter coupled to the fiber optic portion configured to deliver a signal to the animal tissue; an electronic coupling extending from the opto-electric converter and configured to be coupled to the emitter and the receiver, wherein the electronic coupling is configured to extend outside of the MRI chamber; and a processor coupled to the electronic coupling.