Name the device used to convert electrical signals into optical signals.

The device that is used to convert electrical signals into optical signals is an optical transmitter. This device plays a fundamental role in communication systems where data needs to be transmitted over distances in the form of light. An optical transmitter typically takes an electrical input, which could represent data in various forms, such as video, audio, or digital signals, and converts that input into an optical output, usually in the form of modulated light.

Optical transmitters commonly use components like laser diodes or light-emitting diodes (LEDs) to generate the light signal. The process involves modulating the light in accordance with the electrical input, allowing for the transmission of information through optical fibers or free space.

While a laser diode can be a component within an optical transmitter, it does not function independently as a complete signal conversion device. Similarly, an optical receiver is designed to perform the opposite function, converting light signals back into electrical signals. A photoresistor is a light-sensitive resistor used in various applications but does not convert electrical signals to optical signals. Understanding the role of each device helps clarify why the optical transmitter is the correct answer.