Measurements on optoelectronic emission components

Semiconductor light-emitting components are the backbone of a growing number of optoelectronic edifices. They are found in fiber-optic telecommunication systems, optical sensors, optical disk reading systems, certain terminals and measurement equipment (printers, alarms, distance meters, etc.).

These are the components that have changed our daily lives the most in recent decades, and there's more to come, as futuristic ideas emerge in lighting, for example. High-power light-emitting diodes could replace the lamps we use today. They offer a number of advantages: high energy efficiency, long life (10 years), robustness and the ability to broadcast information in a way that is not perceptible to the eye. This last property opens the way to numerous innovations.

The performance of these optoelectronic systems is closely linked to that of the transmitting components. Their evaluation, improvement and proper use depend on precise measurement of the fundamental parameters involved in each application.

Let's take the example of a fiber optic link, where the information is carried simply by the intensity of the light: we need to be able to measure the optimum modulation speed of the emitted light and the lack of linearity introduced by the conversion of electric current into light. In more sophisticated systems, such as coherent transmission systems, where phase, or frequency, is the information carrier, knowledge of frequency, or phase, noise is of vital importance.

After a brief reminder of how solid-state transmitters work, we'll describe the methods used to measure the main parameters. Purely electrical measurements will be described first, followed by purely optical measurements. Then we'll move on to measurements involving the conversion of electrons into photons.