general info on fiber optics

whats up everybody, i need a little bit of help finding any kind of reading or tutorials on how to work with fiber optic systems like on mercedes and other expensive cars. i cant seem to find anything helpful on the net so im turning to you guys. mainly i need to know how to test and possibly interface with fiber optics. what to do, what not to do, stuff like that. im starting to see these kind of systems more and more these days and im just trying to stay ahead of the curve so any help at all would be nice.

Unfortunately with OF (or FO if you prefer), you can't just tap-in or remote-sense as with electrical conductors. (Although theoretically there is a zero-power virtual wave outside the fiber around bends. But until the quantum gurus figure out that you can observe something without effecting it, they won't be able to measure a zero-power object - virtual or not.) That means either you tap in to existing joints with an optical splitter or a repeater (with electrical tap), or you splice in your own. Splicing requires specialised equipment that ensures identical clean & matching cuts, proper alignment & resealing - though these days such kits can be cheap. (I think have seen some for ~$25, but they are often $100s or more.) And the there is a signal loss associated with each splice (it used to be 3dB) & at least 3dB for a passive splitter. The upshot is that you are probably at the mercy of whatever is provided my the manufacturer though they no doubt have some interface for fault finding. Maybe even a few for continuity checks, though that is probably pointless as any break or failure means the entire OF circuit or loop is replaced. (My system was an OF loop so it tolerated one break, though risky sections had taps for jumpers.) And unless there is some lovely standard that all conform to, there is a selection of single or multi-mode OF, the thicknesses & wavelengths, armour-plated etc, not to mention the protocols used - probably IP (Internet Protocol) if certain telcos were to be imitated. I may be stating the obvious above. And that it is difficult staying ahead of the "automotive" curve when that industry lags others so far (like 20 years??). You will merely be able to follow what they provide. The only leading you can do is provide the standard that they will all follow - that's as easy as worldwide OBD-III. Yet again be aware of my generalisation. Someone with actual experience may provide specific help and answers. Good luck!

thanks for the information. even though most of it was stuff i already kind of knew about. you guys just basically confirmed that there is really nothing i can do other than get a tester. it still would be nice if anyone had any kind of technical reading material or links. oldspark you are right about one thing that the auto industry is usually way behind the curve and sadly the installer industry is even farther behind. nobody makes any kind of interfaces that i can find for OF vehicles. i guess because they think that the average tech wouldn't be able to understand whats going on or maybe due to the fact that a car isn't exactly the best environment to be running fiber optics, its just not practical

It really isnt practical. The biggest plus side of fiber is the length it can go without repeating the signal depending on splices and other losses of course. And the pure bandwidth it can carry over that distance. Its a car, how far and how high bandwidth does it need to be?

sinistar wrote: It really isnt practical. The biggest plus side of fiber is the length it can go without repeating the signal depending on splices and other losses of course. And the pure bandwidth it can carry over that distance. Its a car, how far and how high bandwidth does it need to be?

its not necessarily the bandwidth that is important in a car its the fact that fiber optics doesn't pick up any electrical interference aka silence. pure signal. i would love to run it through my truck but cant find an amp that accepts a straight optical input even though there are a few (1 or 2) head units that offer an optical output but they will only work with a certain signal processor and amp, far from universal. the only other option is to use a car PC with a sound card that has an optical output but the fact that it still would need to be converted to rca's to be used on an amp completely defeats the purpose.

Your are not only Sounding off, but Securely so - at least IMO. The reason OF in vehicles was touted decades ago was lightness. Long ago I figured the simplest & lightest vehicle wiring was a power loop with taps - ie, heavy gauge copper (or Al if secure) around the car with junctions at each load - RH stop, RH tail, RH reverse etc. But then came the control loop - obviously not parallel etc, but serial. Maybe coax ethernet - the newest super high speed that would solve bandwidth problems forever (LOL!) - namely 1Mbit/s? Nah, I preferred OF. Else plain 2-wire comms. Or using the power loop itself (but I preferred OOB - especially in that environment). Now I'm sure the Military got into OF vehicles once they figured out why that Russian MIG had miniature valves (re defection to Japan; 1967? - Who had the last laugh there LOL!). Not only interference proof, but EMP proof and minimised the conductive antennas. Let's see - that's 1970s.... I think OF began around then. (As I recall, Australia's "Telecom" bought 90% of the world's output of OF - which was then only produced in Germany.) 30 years later and we have some kind of copper OBD system? Oh well, at least it isn't wireless (thank the spirits!). And who know, soon it may become a standard open interface. WOW! FYI - I kept getting into trouble for all the "unroadworthy" and illegal things I did - like having motorcycle running lights (dim non-flashing indicator lamps); indicators in front of car door/wing mirrors; rear-window mimic stop lamps; flashing stop lamps (flashed when first applied; proportional flash & brake rates); four headlights with dedicated outer low-beam; blah-di-blah.... At least they couldn't touch my wing mounted CONVEX mounted mirrors as they were standard equipment. External convex mirrors were dangerous back then - unlike like today.... LOL! Mind you, I still get into trouble, and that's from peers! I too have been chastised for pointing out the fallacy of aftermarket EFIs with multiple maps or of oil-pressure controlled fuel pumps (and their DANGER!). Even recently where I merely repeat industry wisdom about NOT paralleling batteries. I suppose in 20 years those things will be as stupid as the banning of laminated windscreens and air-bags. Ah yes, I find lagging ignorance to be bliss!

The Light Brigade is a good source to stay updated. Boy, before FO was familiar to most.... on the job we would always make a big deal out of its installation... People literally flew half way across the US to watch us terminate it. I'm talkin a 300ft', single mode, 12 strand tie from the MDF to the IDF. Big Deal! Probably not a bad idea to keep tabs on FO these days. Check this out though: It is believed by some that the benefits of its use in audio has not been recognized yet, so to speak. They are arguing that the transition between light sourcing and the typical electrical transfer is having negative repercussions on the clarity of the signal. This comes mainly from the Home Audio enthusiasts I know who for some time have had the ability to patch components with it, but are not eager to do so.This is what I do for FUN!

ianarian wrote: They are arguing that the transition between light sourcing and the typical electrical transfer is having negative repercussions on the clarity of the signal...

That sounds like a bit of crap to me... It's like the old "CD balancers" that used to be sold to minimise the wow & flutter - can you still buy them? (They were like rubber bands that fitted around the rim of the CD). As if you couldn't have 10% or 100% wow & flutter - it still wouldn't effect the sound output (in CD/DVD most systems; with qualifications). If they are talking fibre-optics as an analog transmission medium, then it's as valid as any other medium. But as a digital signal path? I'd like to know more. Then again the usual criticism with digital is that it is TOO clear - because it does not have the harmonics introduced by analog recording and reproduction, it lacks the richness.... But the statement is ambiguous, so I remain open.... (But I'll bet....) PS - I remember when telecoms competition started over here. The newstarter did not need that over-engineered OF-laying vehicle of the former monopoly. They laid their own stretch of 70km of OF between 2 exchanges - and had ~7kms left over (it was 70k of fiber for a 70k distance). They re-ordered and had the cable relaid - using the monopoly as subcontractor. Like so many things, the newbs just don't understand..... Nor do many inquire.