I’ve been following the great tetherless BlueROV2 builds here (Droplet and others) and noticed that the data link is usually the hard part, acoustic is too slow for video, and going fully tetherless means losing your real-time camera feed.
I’m working on a low-cost underwater optical (blue-light, ~450 nm) wireless modem aimed at exactly this gap: real-time video (~1 Mbps) over short range (a few meters to tens of meters in clear-ish water), using simple OOK modulation on an FPGA. The goal is an affordable module that small ROVs like the BlueROV2 could integrate, not a $20k+ commercial unit.
Before I go too far down the engineering path, I’d love to hear from this community:
1. For those building tetherless / reduced-tether ROVs, how are you handling the video link today? What hurts the most?
2. Would a short-range optical video link actually be useful for your use case, or is range (clarity/turbidity) a dealbreaker?
3. What would “good enough” look like for you; resolution, latency, range, price?
I’m genuinely trying to learn whether this solves a real problem before building more. Honest “this wouldn’t work for me because…” answers are just as valuable as enthusiasm. Thanks!
This is a really interesting idea, and it sounds like a fun build. Though, I think you’re wise to start with “Will this solve a problem for someone”. I’d imagen if the water is clear enough for this too work, then you might not need the ROV in the first place. I’d maybe start by talking to a bunch of Blue ROV users, and without asking them, see if they mention any problems or complaints that a wireless video feed could fix.
Yes, you’re right. My goal was to get users’ feedback anyway. If it’s not actually going to be put to use, it won’t be more than a hobby project. In my forum searches, I’ve seen people complaining about this in the past.
Maybe you could reach out to those accounts and ask if this could help them. You’d be able to find out if they were just complaining about a minor problem, or jumping to buy a solution.
There is a book called “the mom test” that explains this process of customer discovery really well.
A tether, be it copper or fiber-optic, has bandwidth and more importantly, physical limits. The drag a tether induces can be the biggest restriction an ROV faces - if the current to overcome is uniform from the surface to the target depth, the ROVs ability to overcome it at the surface does not guarantee it will do so as depth increases and tether drag with it.
Therefore, if your optical modem connection gave sufficient bandwidth for video and control, at ranges from 100-300m in clear water (at least the kind I encounter in Hawaii), it could indeed be quite useful. Especially if feedback of the connection quality was given, so exceeding the range could be avoided?
Without a tether, the overall risk to the vehicle does however greatly increase… even though the BlueROV2 is typically battery powered, the tether can serve as a recovery method if the power becomes especially depleted, avoiding permanent damage to the battery.
The most common application I’m aware of for optical and acoustic modems is in telemetry and control of AUVs, and data transfer from bottom-located asset to auv or surface unit. This is lower data rate than HD video, with more focus on range vs. speed.
What kind of range and bandwidth are you targeting?
Targeting 1 Mbps at 50-100m in clear water for the MVP. Adaptive rate down to ~10 kbps at longer range. One of the MVP goals is 480p 30fps video with compression (H.264) — which should fit within 1 Mbps comfortably. ROV tether replacement is a stretch goal; primary focus is AUV dock data-offload at short range where turbidity isn’t an issue.
Curious: what would be the minimum acceptable video quality for your use case underwater? Is 480p 30fps enough to identify what you need to see, or would you need higher resolution?