How is an electrical signal converted into an optical signal capable of carrying information?

3 days ago

2 min read

When we talk about computing, we tend to think of processors, transistors, and electrical signals. But there’s another way to move and process information: using light.

That’s one of the fundamental principles of integrated photonics.

The idea may seem complex, but the starting point is simple: data is still generated as digital information, represented by bits. What changes is the way that information travels and is manipulated within the system.

Instead of relying solely on electric currents, we can convert that data into an optical signal and then work with the properties of light.

From an electrical signal to an optical signal

Schematic showing the conversion of electrical signals into optical signals using a laser and Mach-Zehnder modulators, with two data inputs that are subsequently processed by photonic logic gates such as AND, OR, XOR, and half-adder.

The data begins as electrical signals. At the same time, a laser generates the light we will use to carry that information.

The light splits into different paths, and each branch passes through a Mach-Zehnder Modulator (MZM). This component allows the electrical signal to control the light and modify it to represent the input information.

In other words: the information remains the same, but the medium we use to carry it changes.

Once the data has been converted to the optical domain, the signals can be routed to different parts of the circuit.

And this is where it gets interesting.

The optical signals can interfere, combine, and be processed to implement different logical functions, such as those shown in the diagram: AND, OR, XOR, or Half Adder.

Integrated photonics thus enables the design of circuits in which light not only carries information but also participates in its processing.

What if we use more than one wavelength?

A wavelength-division multiplexing scheme in which multiple optical signals are modulated using an MZM and combined in multiplexers to feed the inputs of photonic logic gates such as AND, OR, XOR, and half-adder.

Instead of working solely with a single optical signal, we can use different wavelengths to carry different information channels within the same system.

Each wavelength can carry its own information, and subsequently, several of these signals can be combined using a multiplexer.

A simple way to visualize this is to imagine multiple channels traveling through the same infrastructure, but each using a different wavelength.

Thus, instead of relying solely on separate physical paths, light itself offers us another way to organize information.

This ability to work with different wavelengths is one of the most interesting features of integrated photonics.

Another Way of Thinking About Information Processing

In electronics, we’re used to thinking about cables, currents, and electrical signals.

In photonics, other concepts come into play: light, optical paths, interference, and wavelengths. And that’s precisely where the shift in perspective lies.

It’s not simply a matter of replacing electricity with light, but of harnessing the properties of light to explore new ways of transmitting and processing information.

The two images illustrate this evolution in a simple way: first, how an electrical signal can be converted into an optical signal; then, how that same principle can be extended by using different wavelengths within the same architecture.

This is one of the fields we explore at Tarranix as part of our work in photonic computing.