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optical over distance
#202584 03/30/08 05:02 PM
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I would like to connect the digital output from the TV to my receiver. However, the TV only has an optical output for the digital signal. I need about an 8 ft cable from the TV to a wall jack, about 15 ft of in wall cable, and maybe 3 ft cable from the back of the entertainment center to the receiver.

This is way too far for the cheap plastic optical fiber (POF) to carry a signal with 3 cables. I have got it to work with two 4ft cables and a single wall plate. But even a 9ft and 4ft with a wall plate looses too much strength to use.

Would better cables (quarts or glass) work or will I need to use an optical to coax converter and run coax all the way? Or is there a booster that will increase the signal strength to make it usable?

Re: optical over distance
OhioKyle #202587 03/30/08 05:40 PM
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Have you checked out monoprice.com? They may have something for you. If no, I have seen repeaters but I would try a longer cable first.


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Re: optical over distance
Hansang #202588 03/30/08 06:11 PM
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This is just a guess, but I think glass would probably work much better. My only experience with optical fibre is gigabit ethernet over fibre, which is a bit of a different animal. I believe we have about 5-7 splices in our line.


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Re: optical over distance
Ken.C #202628 03/31/08 01:16 AM
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Try bluejeans. Since they test all the Mitsubishi Eska POF cables they make prior to shipping I'm sure they know just how long a cable will work.

A splice on network fiber is welded somehow is it not? I remember my brother did some fiber install a while back and I remember him talking about a superwammodyne fiber joining tool.


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Re: optical over distance
prototype3a #202642 03/31/08 03:51 AM
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Not my fiber... It may well be joined like that under the street.


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Re: optical over distance
Ken.C #202653 03/31/08 12:17 PM
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Telco grade fiber can be spliced a couple of different ways. The permanent method is indeed a form of weld. I'm not totally familiar with how it works but it can produce results so close to 100% that it is usually a non issue (when done properly). The challenge is lining up the fiber EXACTLY. As you can imagine, if the two pieces are not lined up properly, it will diminish the signal strength or alter it until it is unusable.

There are pieces of electronic gear that can do this automatically and do a very good job of lining up and splicing the fiber. These pieces of gear are expensive but tend to do a good job. I'm not familiar with their innards to explain how they work exactly, although I have seen them in action.

There are also manual devices that can assist the tech to line up the fibers prior to being spliced. They are not as good as the automated electronic versions but do a good job in the hands of an experinced technition.

The quick and dirty method is to use little plastic clips that attempt to line up the fiber and squeeze it together. They look like small plastic tubes about the size of a larger car fuse. They open on each side of the cylinder and the idea is that you put the end pieces of the fiber in each end and then close it and tighten a squeezing, locking mechanism. This locking mechanism squeezes the fiber into the dead center automatically and can often get you back in service.

These manual splicing clips do not normally give you 100% signal perfection, although the laws of chance sometimes makes it happen. However, they can get you back in service in a hurry until the van or trailer with the fancy splicing machine can get there. to do the permanent solution. The bonus is that anyone with 30 minutes of training can put these things on in a few minutes.

The real challenge is that in telco fiber, you are not talking about just one glass core. The cable is filled with 20, 50, 100, or possibly hundreds of smaller, individual fibers. In a large fiber cut, these all have to be sorted out so that you connect each side back together with it's proper match.

I wouldn't be to concerned if you heard about 'properly' spliced fiber in your telco plant. This is normal. A really good scope can spot a well done splice in a line. However, if it's done well enough, you might be very challenged to see it on a scope. Of course, a poorly done splice will be much more obvious to find.


As for fiber for home electronics, I know little about them but some reading tells me that older, poor quality cables with plastic cores can present issues over longer distances and sharper bends. A cable with a newer glass core is preferable.

If either are working in good conditions, both will be 100% effective and certainly won't sound different than the other as they are just passing ones and zeros. However, the plastic or otherwise inferior one is more likely to have stress related issues from distance or bending much quicker than the glass.

As stated. I'm not all that familiar with fiber interconnects for the home but going by the logic of the Telco manual splicing devices, I would have to say that there is an obvious logic that one long, well made fiber will be superior to two or more smaller fibers connected together.

I think that the common distance limitation for the TOSLink standard for optical home electronic connections is 5 meters. Since this distance in itself is not very far, adding any sort of interconnect between two TOSLink cables, you risk reducing this length or even making them unusable.


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Re: optical over distance
Murph #202658 03/31/08 12:46 PM
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Who needs wikipedia when you've got the Axiom forum? \:\)

Re: optical over distance
pmbuko #202659 03/31/08 12:52 PM
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Ya, sorry about that. I need to learn to post links instead of babbling on myself.

I just figure you guys have provided me with soooo much useful information that I feel like I should contribute when I actually know a little about something.

Last edited by Murph; 03/31/08 12:53 PM.

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Re: optical over distance
Murph #202661 03/31/08 01:32 PM
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Thanks Murph. I just looked on bluejeans again and noticed this.

"In our own usage, we've tested these cables at lengths up to 50 feet and found them to perform perfectly even at those extended distances."

I thought their site said something like that but I was missing it somehow before. I have one of their optical cables and while only 7 feet long I can tell it's a high quality part like all their other cables. I will say that I am rather disappointed they used purple stress reliefs on my white subwoofer coax cable.


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Re: optical over distance
prototype3a #202667 03/31/08 01:51 PM
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Purple stress reliefs will optimize all your Prince songs!


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Re: optical over distance
Murph #202686 03/31/08 06:10 PM
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I've got that same sub cable with the ugly purple bands. Totally agreed!


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Re: optical over distance
Murph #202688 03/31/08 06:46 PM
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 Quote:
Purple stress reliefs will optimize all your Prince songs!

Somewhere at an Imax workstation, two ears perked up.....

Re: optical over distance
Murph #202690 03/31/08 06:48 PM
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Oh, do not apologize. That was meant as a compliment. \:\)

Re: optical over distance
MarkSJohnson #202691 03/31/08 06:49 PM
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You sure it was ears?

Re: optical over distance
OhioKyle #202759 04/01/08 02:54 AM
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Kyle, it doesn't seem very useful to rely on arbitrary length limits for Toslink connections, since three factors are involved: the strength of the LED output in the sending unit, the attenuation of the light in the cable, and the sensitivity of the LED conversion process in the receiving unit. So, the same cable can have different results depending on the associated equipment. You might note that users reported success with the 35' MonoPrice cable . Yes, another option is to use the optical to coax converter that MonoPrice and others offer.


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Re: optical over distance
JohnK #202760 04/01/08 03:23 AM
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I've got a 30 foot optical cable from monoprice going from my PC to my receiver and it sounds fine, never had issues


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Re: optical over distance
blackstar79 #202787 04/01/08 02:35 PM
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Gotta be the splices.


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Re: optical over distance
Ken.C #202804 04/01/08 05:14 PM
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My optical cables are from Blue Jeans Cable, as are most of my others. The reason I am using multiple cables is I have a built in cabinet for the entertainment center. I am running everything from the back of the center, through a wall to a four gang wall plate with keystone jacks to plug the TV, speakers, etc. into. I like the clean installed look.

I was surprised that two 4ft cables with a jack worked but a 9ft and a 4ft with a jack would not. It is starting to look like I might have to run a single cable through a modified keystone cover to get this to work. It won't look as nice but it should work.

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