In 2020, NASA's first-ever integrated-photonics modem will be tested aboard the International Space Station. Mike Krainak leads the development of the modem, which integrates optics-based functions such as lasers, switches, and wires onto a microchip. The technology will improve the way NASA sends and receives data during space missions.

NASA Tech Briefs: What are the advantages of using light in communications?

Mike Krainak: Light has made it possible to have this incredible bandwidth. You can have a phenomenal amount of data that you transmit over these now very-low-cost transmission media: glass fibers. That has led to the terrestrial revolution in communication. You can transmit this light from here to California, or from here to Europe, or all the way across China.

NTB: What are the advantages of using light in space communications specifically?

Krainak: In space communications, the size of the transmission antenna, or telescope, [is reduced]. Early satellite TVs are a great example. Your neighbor, because of the wavelength being used, had a satellite dish that took up his whole yard, and it was a big eyesore. Once you make the wavelength shorter, moving up to the Ka-band or the 30-GHz band, the wavelength becomes a fraction of a meter. The optical antenna, or telescope, can then be a fraction of a meter. Both the transmit antennas and the receive antennas can now have very, very small diameters.

NTB: How does the modem support NASA's Laser Communications Relay Demonstration?

Krainak: With our first geosynchronous Laser Communications Relay Demonstration, we are transferring data from one place to the other. For the astronauts, we’re relaying the information from the space station or from the orbiting capsule. We’re relaying the data from them, through a geosynchronous satellite, and then down to Earth. We’re going to demonstrate the relay between ground stations. That’s just a stepping stone; hopefully, over time, you would have a community of users in lower-Earth orbit that would use the geosynchronous relay to get information.

NTB: How are integrated photonics circuits being used to support new sensors?

Krainak: The blood oximeter was invented in the 1940s, but it couldn’t be fully realized until it could be made in compact forms in the 1980s. Once you have an integrated form that’s very small, you can clip a little red LED on your finger to look at your blood oxygen. So why stop at oxygen? You can have a blood oximeter that runs over to your smart watch. But instead of just measuring your blood oxygen, it can measure all of the 200 constituents in your blood. As [the oximeter emits] more laser wavelengths, you can do more refined spectroscopy, along with electronics signal processing. You can conceivably analyze the constituents in your blood without taking blood.

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