We present an implementation overview and demonstrated error-free coded performance over the 400,000-km link between an Earth-based laser communication terminal and the LADEE satellite orbiting the moon at 9.72-Mbps and 19.44-Mbps uplink rates.

The space terminal modem for the Lunar Laser Communications Demonstration (LLCD) provides duplex lasercom capabilities between the Earth and a satellite in lunar orbit with a 0.5-W optical transmitter delivering downlink data rates of 39-620 Mbps and an optically-preamplified direct detection receiver supporting uplink data rates of 10-19 Mbps. The modem consists of four subsystem modules: digital electronics, analog electronics, power conditioning, and electro-optics. This modular approach permits subsystems to be built and tested in parallel and provides design flexibility to address evolving requirements. Other important design considerations for the modem include the utilization of commercial-off-the-shelf (COTS) components to reduce delivery time, cost, minimization of size, weight, and power, and the ability to survive launch conditions and operate over a broad temperature range in lunar orbit.

We implemented a photon-counting optical receiver using a periodically-poled lithium niobate waveguide and an emulated array of silicon Geiger-mode avalanche photodiodes. We achieved a sensitivity of < 0.5 detected photons/bit at 187.5 Mb/s.

We implemented a photon-counting optical receiver at 1550 nm with periodically-poled lithium niobate and a silicon Geiger-mode avalanche photodiode. We measured a sensitivity of 1.9 incident photons/bit at 18.8 Mb/s for a single detector.

Monolithically integrated widely-tunable wavelength converters are a family of photonic integrated circuits whose function is essential for wavelength division multiplexing (WDM) systems, particularly in functions like optical switching, wavelength routing and add/drop multiplexing. Wavelength conversion in WDM optical networks can potentially allow for much greater network flexibility and improved performance. Tunable all-optical wavelength converters allow data to be transferred from an input wavelength to a tunable output wavelength without passing the signal through electronics. To be practical, the wavelength converters need to be capable of stable operation, have a small footprint, operate with low power consumption and have a low cost. Monolithically integrating wavelength converters with tunable lasers has the potential to meet all of these requirements. These requirements fit naturally with the demands of current and future avionic networks and systems for low weight, footprint and low power consumption robust components. This paper gives an overview of the state-of-the-art in the field of integrated tunable wavelength converters, in particular focusing on the results related to the monolithic integrated wavelength converter research conducted at the University of California in Santa Barbara, as part of DARPA Microsystems Technology Office's Chip-Scale WDM (CS-WDM) program. The objective of the CS-WDM program was to develop and demonstrate novel chip-scale WDM component level technologies for use in networks on-board current and future military platforms, and to develop and evaluate innovative concepts in network design. These new WDM components and network concepts were intended to deliver significant improvements that are of particular benefit to military weapons systems, relative to conventional WDM methods.

Silicon Geiger-mode avalanche photodiodes (Si GM-APDs) have desirable properties for an optical photon-counting receiver, including high single-photon detection efficiency, low reset time, and low timing jitter; however, they do not detect near-IR photons. In this work, we demonstrated a sensitive photon-counting receiver in the near-IR by combining a wavelength converter consisting of a periodically-poled lithium niobate (PPLN) waveguide and a commercial Si GM-APD detector. We measured a receiver sensitivity from 1.4 to 3.5 incident photons/bit from 5.5 Mb/s to 22 Mb/s for a single detector, and achieved a sensitivity of 4 photons/bit at 78 Mb/s using an emulated array of 25 detectors.

In this paper, we demonstrate a 1550-nm photon-counting optical communications channel using pulse-position modulation and an optical receiver utilizing a periodically-poled lithium niobate wavelength converter and a silicon Geiger-mode avalanche photodiode.