Fiber optic rear lamp monitor

[Guido]

Can the fiber optic be repaired.

[79 Eldorado]

Richard,
You should tell us what's wrong with it and as well what year/model you have.

The systems are typically a boot on the end of a fiber optic cable. The boot goes over an area integrated in the rear light housing. I would first check to see if everything is connected.

Scott

[Big Fins]

I think he means if it can be spliced. Once severed, the optic continuity is forever broken. Replacement is about the only option.

[Guido]

Thanks for the response. I have a 1976 Eldorado Convertible. One fiber optic cable has been cut and one side works. I have no experience with fiber optics. I was hoping it could be fixed but if not any ideas about replacing. 

[The Tassie Devil(le)]

What I am doing at the moment is exactly the same thing.

But, as I haven't completed it as I am in the middle of fitting the back seat, I can only offer an insight into what I am proposing.

Using a piece of scrap nylon stock, I bored holes the same diameter as the Optical Cable, and then trimmed it down for lightness.   Using this piece as a simple joiner, I can insert each end of the cable that has been squarely cut with a VERY sharp blade, and as can be seen in the last picture, the inside of the cable has more than one optical fibre.

Then once one end is almost  halfway in, the other end can be inserted, and when not quite touching, rotate one cable to try and obtain the most number of Optics to be opposite each other.   This must be done whilst applying a light source to one end, and looking at the opposite end to gain the optimum light transference.

By not pushing the ends tightly together, there is going to be every chance for the light from one optic to possibly transfer to parts of the adjacent optic, as when comparing two cables, the optics are not exactly equally arranged within the insulation.

This Nylon block seems to be the best method I have found thus far.

Bruce.

[79 Eldorado]

Bruce,
Isn't the end at the light source simply cut and it picks-up enough light to transmit. I was wondering is adhesive shrink tube would work (maybe with a piece of tape at the splice to keep the adhesive from getting into the splice). How difficult was it to cut clean? Is is just that at the source the light is bright and abundant but at a splice the same situation doesn't exist? I'm almost certain that I've also seen fiber optic cable sold in coils. I thought about buying a coil and making my own ends. I don't think there's anything special to the ends other than joining with the feature at the light (looks like a tight fitting rubber boot) and on the monitor. Am I getting that part wrong; is their more to the end than I suspect?

I once came across a 1979 E-Body in the local junkyard which was as fully optioned as I've ever seen for a 1979-85 E-Body. I noticed that someone had cut most of the fiber optic cables around the dash area. I immediately though someone was likely looking for a ground and couldn't tell the difference between fiber optic cable and ground wires. What a disaster.

Scott

[The Tassie Devil(le)]

G'day Scott,

I have tried to source a replacement cable that I could simply replace the whole piece, but there was nothing in what I was after that looked anything like what I could use.   Either too stiff, too large in diameter, and too large overall to even look like getting into where it had to feed.   The smallest coil I could buy was 3 feet in diameter, meaning that it was going to be impossible to fit the ends up in the rear seat mount.   Which have to be bent at a tight 90 Degrees, as in my case, I was using a Coupe Mount.   The Convertible Mount has to be even tighter.

Looking at the cut pieces in the vice, the individual fibres are not exactly aligned so a simple cut and splice is nothing like as used in the modern day of splicing Optics as used in the Telecom industries.

Yes, the ends are simply cut and squeezed into a brass ferrule that is pointed towards the filaments of the globe, but modern day Fibre Optics are so small that they are not for what we are using ours for.

I tried using pieces of Heat Shrink to hold the joins together, but, once the joint was made, if the alignment was out by a smidgeon, it couldn't be rotated to get a better alignment.   I have that method currently in my Eldorado, but the light transfer is not good enough for daytime use.   At night, one has to be really looking at the monitor to be aware that it is working.

I have found that when people pull stuff from cars in Wrecking Yards, unless they know what is there, they only want to get the part that they are after, and just hack away.

Initially I adapted a Coupe one as I didn't have a Convertible one, and made a bracket that I could be able to slip it up and out of the way when I was fitting the Hard Boot, then place it back in, after the fitting.

This method worked well, as I had to do emergency repairs to the seat upholstery when I got the car, so it didn't look pretty, but it worked.   Now I have rebuilt the framework, and fitted the new upholstery, it will sit higher, but I now have to decide which one I will use.   The proper Convertible one, and risk it breaking, or finish my new one, using the tapered mount, with the Coupe Guts.

Bruce.

[J. Gomez]

Bruce,

I'm not sure if you or someone else has ever tinkered with some of the telecommunications data fiber optic cables? The one in question is the one used with LEDs devices called MM (multi-mode) these are cheaper and have larger diameter fiber (OM1 type) which are designed for LED light versus the SM (single mode) that are used for lasers and have very small diameter fiber and are more $$.

The MM fiber cables comes in several lengths traditional these have the "orange or light blue/teal" coating and have the LC square type connectors which can be removed leaving the fiber core and the cladding around the core expose. There are also splicing LC connectors to connect two cables if needed.

I'm not sure if the fiber cable use on the Cadillac has a single or multiple cores for the transmission of the light, in your pictures yours shows multiple strands of fibers so again not sure if these have different light sources on them.

Again since these are just a to transmit the light across the two end there is no need for much accuracy on the type of fiber used for this application.

Just an option.   

[The Tassie Devil(le)]

G'day Jose,

The picture with the two cables in the vice, that is the one illuminated, using a light source, and the other not, show what the internals of the one that GM used.

This is one I have online, but the length is too short for the rears.
https://www.mannys.com.au/hosa-opt110-fiber-optic-cable-10-ft?msclkid=e3cb000d757d1ece5a4f619ca26b938c&utm_source=bing&utm_medium=cpc&utm_campaign=DC.ORetailSmartShopping01_All%20First%20Categories_AUD&utm_term=4583382956669639&utm_content=Ad%20Group

Bruce.

[J. Gomez]

Bruce,

Yes, the optical cables used for audio are limited on length due to the low light output.

The one I was referring as MM are the one below, these can be found with several lengths this one is a 5m (meter). Unfortunately the one issue with these is the cable is not cover with a hard armored plastic like the one you show on the link.

https://www.amazon.com/5m-Fiber-Optic-Cable-Multimode/dp/B0009M2FIE

The biggest draw back with fiber optic cables is you need to avoid sharp turns to avoid attenuation of the light source at the end, and the second one is splicing them.   

Since you are a tinkered something to try in your spare time in your next 25 hours day or around February 30th.   

[The Tassie Devil(le)]

Looks like I had better get my finger out and complete my joining, and report back.

Bruce.

[The Tassie Devil(le)]

well, finger pulled, and it looks like the black nylon piece is the way to go, BUT, one has to turn one of the ends around to gain the optimum light transference before pushing the joint closer together.

One thing I have found is that in some cases, Cadillac placed a coloured cap at the tail light end, and then used a clear terminal at the other.   And Vice Versa, when a clear end was used, a Red terminal was used.

The first pictures are the parts that I took out of a Coupe, and these Optics don't have to bend at all whereas the Convertible one has to turn a tight 90 Degrees to enter the fitting.

As I don't have a clear end in my Tail Lights, I will have to either go with the clear Convertible piece, and repair the broken mount, or stay with my metal mount that was made for the Coupe mount.

If one looks at their upper fitting, and the lens is Red, then there will be clear caps in the Bumper Bar.

Bruce.

[79 Eldorado]

I don't have photos but I've had some parts in hand in the past from 1979 (E-Body) and 1983 B-Body and the colored lens was always at the end which the driver can view from the car (above the rear window and on the front fenders). The end of the cable inside the car, above the rear window, has a small metal ferrule which looks like a split top-hat. The cable goes through the top-hat and then inserts into the trim piece with the colored lenses.

In the rear, at the pick-up or sensing end (end at the light source), there is a flexible boot over the cable end. The boot slips over a plastic molded area in the taillight backing. The cables I've seen are always multi-strand and the covering is black in color. I would say around 2.5 to 3mm OD cable with probably 8 to 10 fine strands of fiber optic inside. I never looked closely at the end at the light source but I thought the cable was simply cut and the plastic molded feature in the tail-lamp simply placed the cable end in a good position to monitor the light.

Scott