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Signals in the dark

A difficult problem in oceanography is sending and receiving information and commands underwater. Generally, scientists send information to and from underwater instruments as signals through cables, or as sound that travels through the water. WHOI engineers and scientists have developed an innovative underwater optical modem that can send large amounts of data up to 100 meters using light. Here the modem, mounted on the new Hybrid Remotely Operated Vehicle Nereus, and another instrument successfully “talk” to each other with blue and green lights. As engineer Norm Farr put it, “The predatory blue light, seen here stalking the peaceful green light from below, under cover of darkness.” (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)