Testbed for Modulating Retroreflectors Enabled Passive Optical Communications

A “laserless” optical communication transceiver (also known as a “modulating retroreflector”) uses a wide-angle retroreflector and surface-normal electro-absorptive quantum-well modulators to efficiently encode information onto the optical beam, which is reflected along the same path of incidence. This is particularly attractive to planetary mission concepts using a highly asymmetric resource-allocated architecture and examples include surface missions to the Moon, Mars, and other planetary destinations. A key challenge is the wide temperature range that the transceiver needs to operate without high-power active temperature control. This is particularly challenging for ground prototyping work when the temperature is as low as 100K (lunar night) in the ambient laboratory environment. We designed and constructed a laboratory testbed that can simulate the required operating temperature range for the passive optical communication transceiver including the optics, quantum-well modulator, and necessary electronics. The testbed also includes a design that can work with both continuous-wave lasers and optical frequency combs (pulsed lasers) as the interrogating light sources.