Helllo,
The Blue Robotics site said that the Tether has a maximum distance of 300m for a good signal to handle video and cmd send to the ROV and a depth rated of 950m.
I see some people trying the depth but there is no information on the cable.
If I only want to take pictures with a 100 to 200Kbit rate one way, will the cable support that distance? In fact will it goes to 950m?
Thank you,
Pierre
Hi @Pierre021 -
Welcome to the forums!
The BROV2 can only be configured for a maximum depth rating of 300m. However, many of our enclosures and penetrators are rated to 950m! The limiting factor for the BlueROV2 is the dome, currently.
The 900m depth ROV was a resident, cabled system, not deployed from the surface! It was connected at the seafloor to a system that provided it with power over tether and a network connection all the way to shore - likely using fiber optics!
The Fathom-X tether interface will not work beyond 200-300m, depending on the twisted pair used. Newer versions may manage farther, but generally to reach that distance fiber-optics are required - at least as far as I know! For only 100-200kbit, it may be possible to use other protocols to cover the distance, like RS485. It’s equally about the type of communications, as well as the conductors used!
Yes, I am using RS485. I used 300m of CAT6, not in water, this is working fine of course. I am not using with a ROV, just the enclosure, sensors, camera for pictures.
Now I want to test more distance but doubling it with CAT6 which is 24AWG will not make much sense for the goal just above 1000psi. I will be surprised that these cables take that pressure and I am not sure about the connection even if HDpt is selling 5000psi marine epoxy.
The CAT6 I am using is 24AWG and the tether, more like CAT5, is 26AWG and I wonder how will this handle the distance.
The real question then is can I send data to a distance of 750m using BlueRobotics tether but not your interface?
I started as well to look at fiber optics, most quickly available are 50m in length. Longer than that and it is the magic expre$$ion of “request for quote”… Then I have to link all of them and maybe splice some.
For the dome, yes, 3" is rated 750m and the 2" will go the length of the depth rated cable 950m. I choose the 3" since this is what the depth I have available and I can reach it without using a Falkor (too).
Now of course there is another way to reach that depth. I was thinking about this waiting for input to my question. I can use 3 enclosures, sitting near the fiber optics, which will be the solution of last resort. This solution allows me to de-risk the spending on the cable and based on a maximum of 300m, between enclosures, a guaranty of getting data.
This was the first choice: If the 750m length cable cable can pass data than I only have to use wetlink cable splice kit. Can 750m tether pass data?
Thank you for helping to think harder and get a solution.
Pierre
I use optical fibre in my equipment. It has a diameter of about 3mm, buoyancy almost neutral. I use sections of 400m, 500m, 1000m and 1500m. No problem with control and operation of 5 HD cameras.Equipment tested to 150bar depth (1500m)
Wow nice to have all this equipment!
Will it be possible to know which manufacturer or reseller you use and the price by meter? Ethernet Kevlar from Blue 
is at U$6.5/m and I cannot find the price of fibre unless it is only 50m. I am guessing that you are not sending 1500m of fibre with 5 cameras by hand?
My goal is 750m-800m, half your depth, from a sea kayak, 60kg of cable and I am sure that the weight is not the issue. The issue is the management of the cable in and out.
Have fun.
My company, Gralmarine, has been manufacturing lighting, underwater communication and video equipment for divers for over 20 years. In addition, we build our own ROVs. We have some achievements to our credit. In 2016, our ROV discovered the deepest flooded cave in the world. National Geographic wrote about it. But let’s get to the point. We use SM fibre optic cable, single fibre, tactical type. It has a strength of about 80 kg. 1000 m of this fibre optic cable weighs 8 kg and is almost neutral in water. It is reinforced with Kevlar. On the surface (land) side, it is terminated with an ST or SC connector, which we then connect to a fibre optic/Ethernet converter. There is also a slip ring along the way. Underwater, a Subconn plug, 8-pin (transmission up to 100 MB), or 10-pin (1 GB) is connected to one camera when connecting up to 5 cameras or to an ROV led out of a hermetic converter. We have a pressure chamber for testing up to 2000 m.
Last week, I sent a drum with 1000m of fibre optic cable to a ship sailing to Spitsbergen. It has converters, a drive, i.e. electric winding/unwinding (powered, for example, by a car battery). The whole thing (without the battery) weighs about 20kg.
The fibre optic cable can be between 1 m and 3,000 m long. The cost depends on whether it is just the fibre optic cable or whether it includes connectors, converters and slip rings.