A photoplethysmograph is a device used to optically obtain a volumetric measurement of an organ. The trace generated by the device is called photoplethysmogram.
The most established use of photoplethysmography can be found in pulse oximeters.
Further use of photoplethysmographic measurements for cardiovasculary monitoring, respiration detection and pulse wave analysis has been studied.
See also 
- Reisner, A.; Shaltis, P. A.; McCombie, D.; Asada, H. H. (May 2008). "Utility of the Photoplethysmogram in Circulatory Monitoring". Anesthesiology 108 (5): 950–958. doi:10.1097/ALN.0b013e31816c89e1. PMID 18431132.
- Kyriacou, P. A. (January 2006). "Pulse oximetry in the oesophagus". Physiological Measurement 27 (1): R1–35. doi:10.1088/0967-3334/27/1/R01. PMID 16365505.
- Asada, H. H.; Shaltis, P.; Reisner, A.; Rhee, S.; Hutchinson, R. C. (May-June 2003). "Mobile monitoring with wearable photoplethysmographic biosensors". IEEE engineering in medicine and biology magazine : the quarterly magazine of the Engineering in Medicine & Biology Society 22 (3): 28–40. PMID 12845817.