Pertaining to any device that functions as an electrical-to-optical or optical-to-electrical transducer, or an instrument that uses such a device in its operation. Note 1: Photodiodes, LEDs, injection laser diodes, and integrated optical circuit (IOC) elements are examples of opto-electronic devices commonly used in optical fiber communications. Note 2: "Electro-optical" is often erroneously used as a synonym.