Free-space optical communication transfers information using light traveling through an open path rather than inside optical fiber. A laser can carry data by changing properties of its light. This is distinct from radio communication and, for a receiver on an above-water snorkel tip, distinct from trying to transmit the beam through seawater.
One Laser Source, Two-Way Communication
A modulating retroreflector (MRR) is a promising line of research. The remote device reflects an incoming beam toward its source while electronically altering the returned light to encode data. The source terminal detects that modulation. Thus the remote terminal need not produce its own laser beam, although it still requires optical components and electronics.
NASA described full-duplex digital communication on a single laser beam in a 2006 technical report and has studied modulated retroreflectors for spacecraft-to-surface links. These are demonstrations or proposals of the relevant principles, not evidence that the full snorkeling concept is an existing product.
Questions to Investigate
- Which modulation schemes enable both directions of data on one optical carrier?
- What proportion of emitted and returned light can a compact receiver capture?
- How do sunlight, ocean spray, haze, reflections, and obstructions affect performance?
- Can the required laser arrangement be made eye-safe for swimmers and nearby people?
Selected Sources
- NASA — Full-Duplex Digital Communication on a Single Laser Beam (2006).
- NASA — Free Space Optical Link Utilizing a Modulated Retro-Reflector (2020).