Fibre optic tether

[kenl]

Hi Rovdude,

I don't think I can answer your question for you, I had a quick search on that site but it didn't seem to turn up any transceivers that would convert video to optic and the back again, in addition I would need data, at least in one direction (too the rov).

But I think you are looking at a different control system ? Over a ethernet connection? Am I right? That may well be the answer to it all..... Let us know how it works out for you, if you go that way... Please

Ken

[rossrov]

Hi Guys.

Rovdude, the Digikey parts are either TX or RX (transmitters or receivers) not both combined in the one fibre, so you would need 2 fibres. Still, with a bit of research, a hobbyist could build some sort of converter from the parts. The ROV control and return data (compass, depth...) pretty easy but the video would have to be or be converted to serial data in a format that, in your case, could be decoded by the PC. USB comes to mind but I think the time delay in a long fibre (or copper cable) would upset things and not work. I've never done anything with USB so maybe check that out for yourself.
I get a feeling that there may be some confusion regarding "cat5". Basically Cat5 is just a physical specification for a type of twisted pair cable. It's common use is for Ethernet, but is also commercially used for lower speed data such as RS485 etc, also analog audio such as telephone, and of course analog security system video as used in many ROVs here. So the cable type will not come into the equation when looking at fibre stuff. The type of data into and out of the converter is what to look for in the specs.

I revisited the two links I posted earlier. The first one I managed to find a price on the "topside" component, which was listed by a distributor as $950 - no way. Irrelevant now what the ROV end costs. The second one, I had a look at the data sheet http://www.avexcctv.com/previews/downlo ... r_1101.pdf , this looks to me exactly what we want. If nothing else the data sheet makes sense.

Ross

[rovdude]

Here specifically is where i think the transceivers are that do both TX and RX.

Ross: Thanks for pointing out the fact about cat5 being only a connector. I am new to all of this. When I refer to cat5 i actually mean any type of serial, the speed/architecture I will use will be determined when I figure out this fiber optic thing

Ken: I intend to have an IP camera which uses a serial connection via cat5, and convert that to fiber as the tether, and reconvert it back to serial up top. Does this still require the video to optic conversion you refer to even though it is serial?

[rossrov]

Cool - thanks for link - have not checked these out in detail but I think there is a much easier way of doing it. If you can implement display of IP camera in your own PC software, you can plug a topside Ethernet to fibre converter into the Ethernet port of your PC. The IP camera of course plugs into an ethernet to fibre converter in the ROV. At least that's what I'm planning on

Something like this http://www.itsdirect.com.au/com_product ... 0nkBlWSzjE

Have not tried or even purchased a pair yet, but do have an Ethernet switch to go into the ROV - one port for the camera, the other for Ethernet equipped Arduino. If that works over cat5 Ethernet cable, then I'll consider buying the converters. Higher priorities have been keeping me from submersible stuff of late, but trying to make some progress on my SONAR project today. The ROV itself has kind of taken a back seat...

[rovdude]

Aren't those converters doing the same thing as the transceivers? Or am I just outright confused

[rossrov]

Again, I haven't checked these out in detail, BUT, just looking at one of the datasheets on the link page I'm wondering that maybe it could just be as simple as finding a mating connector and soldering it onto the end of the Ethernet cable and adding a power supply, with no interfacing or control needed? There are inverted TX and RX as well as non-inverted, and impedance of 100 ohms is stated in there somewhere. Would be more compact than the stand-alone converters I linked to last post. Maybe see if you can find a pair that use just one fibre for TX and RX together ? - the sheet I chose pseudo-randomly near the top was a $50 unit for two fibres.

[kenl]

Hi Rovdude,

I thought you were on the IP camera route, I am trying to avoid taking a computer out when I go ROVing, no reason really just the way I decided to go. But pending your findings I may change that .

As for what to buy and will it do what you want it to do, the company you have posted links from appears to be USA based, as do you.... Why don't you just call them, tell them what you're doing and what you want from them. I am more than sure if you get through to a technician they will be very happy to help you.

As I understand it IP cameras are normally connected through the ethernet port on the computer, so I doubt very much you would need a video converter, as the work has already been done by converting it to the ethernet protocol, whatever that is

Ken

[rovdude]

While I do want to call Digi Key, my ROV project is going to have to take a break for the next few weeks Digi Key is a legit website, with very good (and a huge array of) products based in the US and they know what they are talking about. However if anyone wants quicker feedback they do have an online tech service where technicians will talk to you that I have used before that is pretty good. If not, I will definitely get to it and will post my findings!

[rovdude]

Okay so here's what I have found so far:

Transceiver - for TTL communication between Arduino boards (I still need to find one for ethernet communication too, but didn't want the online tech, or my head, exploding). This specific one uses a duplex LC connector, and I assume single mode fiber (definitely need to check that), obviously need two per communication line

1000 ft of fiber - Singlemode, really cheap. I don't remember if this link was already posted on the forum or if I found it in my searches. Need two per set of transceivers

Terminating Connections - Duplex LC

Now what I really need to figure out is how to find a cheap termination kit. I found a lot that are like $700 and up, which is way more than all the other fiber optic stuff here listed together. I also found individual tools, which I think if I buy just the bare essentials for termination I can keep it down to $100-120. Thoughts? Anyone have experience with this?

All these are preliminary finds. I am probably going to call a few companies (actual fiber companies, not the distributors) and make sure this will work, and I still have to pour over the spec sheets yet

[kenl]

Hi Rovdude , I went through much of the process you are now, but never really finished by getting the desired hardware. At some stage I will return to that path though I think.

I seem to remember that I only needed 1 strand of fiber as communication can flow in both directions, also there are much better connectors from a water proofing point of view, I think the ones I was looking at were ST connectors. Field connectors were more expensive but didn't need the full tool kit to apply, there are a few good youtubes that show various ones.