Abstract
Tethered deep-sea robots and instrument platforms, such as Remotely Operated Vehicles (ROVs) and vertical-profiling or towed instrument arrays, commonly rely on fiber optics for real-time data transmission. Fiber optic tethers used for these applications are either heavily reinforced load-bearing cables used to support lifting and pulling, or bare optical fibers used in non-load bearing applications. Load-bearing tethers directly scale operations for deep-sea robots as the cable diameter, mass, and length typically require heavy winches and large surface support vessels to operate, and also guide the design of the deep-sea robot itself. In an effort to dramatically reduce the physical scale and operational overhead of tethered live-telemetry deep-sea robots and sensors, we have developed the Fiber Optic Reel System (FOReelS). FOReelS utilizes a customized electric fishing reel outfitted with a proprietary hollow-core braided fiber optic fishing line and mechanical termination assembly (FOFL), which offers an extremely small diameter (750 μm) load-bearing (90 lb/400 N breaking strength) tether to support live high-bandwidth data transmission as well as fiber optic sensing applications. The system incorporates a novel epoxy potted data payload system (DPS) that includes high-definition video, integrated lighting, rechargeable battery power, and gigabit ethernet fiber optic telemetry. In this paper we present the complete FOReelS design and field demonstrations to depths exceeding 780 m using small coastal support vessels of opportunity. FOReelS is likely the smallest form factor live-telemetry deep-sea exploration tool currently in existence, with a broad range of future applications envisioned for oceanographic sensing and communication.
Highlights
Human access to the deep-sea is facilitated through a spectrum of platforms such as untethered human-occupied vehicles (HOVs), unmanned underwater vehicles (UUVs) and a wide variety of cabled/tethered systems such as Remotely Operated Vehicles (ROVs) [1]
An early prototype version of fiber optic fishing line (FOFL) based on TufLine XP (250 lb test) was produced by Mustad’s subsidiary company Western Filament, Inc.; in parallel, custom designs were pursued by Nautilus Defense LLC
The FOFL’s braided sheath (750 μm outer diameter) has a minimum inner diameter when under tension that is greater than the outer diameter of the incorporated fiber optic core
Summary
Human access to the deep-sea is facilitated through a spectrum of platforms such as untethered human-occupied vehicles (HOVs), unmanned underwater vehicles (UUVs) and a wide variety of cabled/tethered systems such as ROVs [1]. Modern deep-rated ROVs, towsleds, and sonar systems (>1000 m cable length) almost exclusively employ fiber optics for data transmission, typically via steel-armored cables that include power transmission over copper conductors. The size of these cable spools often dwarf the subsea vehicles themselves and require large oceanographic-class winches installed on appropriately sized support vessels for operation. ‘Hybrid’ ROVs, which can operate as both tethered ROVs and untethered UUVs, have demonstrated their efficacy at the deepest depths of the ocean [8,9] In these systems a major length of the tether is bare optical fiber that is extremely fragile, non-load bearing, and cannot be reused for multiple deployments; the robot is retrieved at the surface as a free-swimming untethered autonomous system
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