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Run BlueROV over Fiber Optic Tether?


#1

What is the possibilities to run the BlueROV over a fiber optic cable? If I install Gigabit Ethernet to Fiber optic converters in each end and plug the Fathom-X boards into the Ethernet. Will that work?

Any comments or advise is much appreciated :slight_smile:


Fiber Optic Tether
(Kevin) #2

We don’t know of anyone who has tried a fiber connection, but you are certainly welcome to experiment around with the BlueROV2. You will need to substitute our Fathom-X board for a Fiber to Ethernet converter that will fit in the remaining space inside the BlueROV2. The Raspberry Pi would connect to the converter and would need to be powered from the main power terminal blocks.

The tether would need to enter the vehicle, be potted in either a penetrator or a waterproof connector, and then installed into the fiber converter. A similar converter will need to be used topside. The bulkhead penetration with fiber is probably the riskiest part and you’ll need to understand cutting and crimping fiber connections.

On a technical level, there is no reason why fiber won’t work, the BlueROV2 is all Ethernet based, you’re just changing the tether communications bridge medium. You may have some issues doing the penetrations and finding a converter to fit inside the 4" tube.


(Doug) #3

Would the video lag be reduced if run on fiber?


(Matt) #4

I have a BlueROV running on fibre optics.
Just as Kevin described above. I use a Lancer Penetrator on the 4" enclosure. If you remove the Fathom X and replace with ethernet to fibre converter you can place a small switch right above it in the 4" enclosure.

No additional comms lag at all on the video plus the reconnect time if you drop comms is much faster without the Fathom X board, with a fibre converter its almost an instant connection. I have a 600m tether which allows me to run the BlueROV Pi system at full ~80Mbps bandwidth as well as running sonar, x2 HD IP cameras and 4K IP camera video all on the same network at that length with no lag with the comms. Video lag is still the same due to processing. Using a small switch in the enclosure allows for a lot of expansion on the network.
Using a BiDi SMP Module in the Fibre converter allows dual frequency operation (one for transmit and one for recieve) on a single fibre line, No need for two.

its important that you understand how to terminate a fibre connection and you have the correct terminating equipment and testing gear. Its not a cheap option but it can be done at lower than normal costs if you shop around.


(achat) #5

Hi Matt,
Are you videos good?
Could you tell what are the HD ip cameras you’re using? and which 4K Ip camera?


(Jan Robert Fiksdal) #6

Hi Matt,
We would like to try something similar. Do you have links or partnumbers for the different items?
Regards from Norway


(Matt) #7

Hi Guys

I would rather not put specs on the forum here but if your serious about doing this PM me and I can lead you in the right direction.
In my opinion the only reason to go fibre is to have Gig Ethernet ability at long tether lengths. Its a fair bit of money and effort and not worth it if your only going for 100m.

I got my fibre converters through FS.com, they were really good with excellent customer service. I had a ruggedised tether made for me in the US but i can help you get the right tether off a manufacturer in China for much much cheaper if you dont need it to be heavy duty.

PM me with your email address if your interested.


(Doug) #8

Wondering what it takes to run Blue ROV2 over fiber instead of twisted pair of copper wires. What components would be required top and bottome side? Would you still use Fathom boards or be able to plug direct into Pi Computer?

Would running over fiber would the video latency of approximately 200 msecs be reduced?


(Jacob) #9

Would running over fiber would the video latency of approximately 200 msecs be reduced?

No, there is 100-200ms latency even with the camera plugged into the same computer running QGC. A significant fraction of this is probably built into the camera hardware. The network latency is usually less than 10ms latency, even with a copper tether.


(Etienne Demers) #10

Hi Doug,

I already got this done.

PM me if you are interested.

You basically put my module in place of the Fathom board.

This is my fiber optic module installed on my network upgrade:

You can alternatively just install it in where the Fathom-X board is located.

Cheers,
E.


(Etienne Demers) #11

Hi Doug,

the IP camera needs time to capture the video and “transform it” to a H.264 video stream. This is where the 200ms comes from. I am sure technology will catch up eventually but at present this is what we have to work with.

Any particular reason why this is bothering you. It is hardly noticeable when flying…

What the Fiber Optic mod does is give you as much bandwidth as the ROV possibly can, as if it was connected directly to the ROV regardless of how far it is.

This might sound like it is of no importance but it is actually one of the most important thing if you want to maintain performances with tether length.

This is the bench test I just did with my fiber mod over 300m tether to show you this:

Note the Upload and Download speed.

If I plug a 1 meter fiber lead I get the same results… If I plug an ethernet cable from my computer directly to the Raspberry Pie I get the same results.

Now try this with a Fathom-X. The longer the cable, the less bandwidth you will get.

This not only considerably limits the number of camera / sensors you can use but can also affect the performance of a basic BR2.

In fact, the last system I sold with the latest Bluerobotics mods had very poor performance over 300m tether with Fathom-X.

I had around 12 MPS upload and even less download. Although I did not have the unit long enough to see how I could improve this, it proves the Fiber upgrade to be most valuable in a commercial application.

Brand new ROV and the video had a tendency to lag a lot more than 200ms…

Cheers,
E.