Minimum Bending Radius for Optical Audio Cable - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 11 Old 01-16-2012, 06:08 PM - Thread Starter
Member
 
RamKat's Avatar
 
Join Date: Aug 2007
Location: Ottawa, Ontario
Posts: 91
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi, I would like to route a 25' monoprice 8mm toslink audio cable through some walls in my basement. The ends of the cable will be terminated inside keystone toslink couplers that will be mounted in two wall plates. My question is, will the 4 inches behind the wallplate be enough to accommodate the required 90 degrees bend and the coupler/connector without attenuating the signal below the required levels. The routing in the wall will also require a couple of 90 degree bends. (the assumption is that there will be some signal loss in any 90 degrees bend) Is there some spec available that I could refer to (I could not find anything on the monoprice site)

Epson 8500UB (R); Elite Electric100 16:9; Yamaha RX-V671; Polk Monitor 60 x 2, Polk CS2, Polk Monitor 30 x 4
RamKat is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 01-16-2012, 06:11 PM
Member
 
jparr's Avatar
 
Join Date: Jan 2006
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by RamKat View Post

Hi, I would like to route a 25' monoprice 8mm toslink audio cable through some walls wall in my basement. The ends of the cable will be terminated inside keystone toslink couplers that will be mounted in two wall plates. My question is, will the 4 inches behind the wall be enough to accommodate the required 90 degrees bends and the coupler/connector without attenuating the signal below the required levels. (the assumption is that there will be some signal loss in any 90 degrees bend) Is there some spec available that I could refer to (I could not find anything on the monoprice site)

That should be fine. Fiber handles a lot more abose than people think. You can test it by placing a strong flashlight up against one end and looking for light at the other.
jparr is offline  
post #3 of 11 Old 01-16-2012, 06:11 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
90 degree bends for fiber is bad. Even with regular copper wire, 90 degree bends is bad. Fiber needs a long sweeping turn, not sharp. Even with copper, it should be a sweeping turn, so that the wires do not break inside the jacket.
gregzoll is offline  
post #4 of 11 Old 01-16-2012, 06:32 PM
Member
 
jparr's Avatar
 
Join Date: Jan 2006
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by gregzoll View Post

90 degree bends for fiber is bad. Even with regular copper wire, 90 degree bends is bad. Fiber needs a long sweeping turn, not sharp. Even with copper, it should be a sweeping turn, so that the wires do not break inside the jacket.

Idealy a sweeping bend is best, but certainly not required. In fact, when testing fiber the light meters require the fiber test lead to be wrapped around a drum slightly smaller than a wine cork. That is a bend radius of only a few mm.

http://www.aflglobal.com/Products/Te...-Test-Kit.aspx
jparr is offline  
post #5 of 11 Old 01-16-2012, 06:33 PM - Thread Starter
Member
 
RamKat's Avatar
 
Join Date: Aug 2007
Location: Ottawa, Ontario
Posts: 91
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by gregzoll View Post

90 degree bends for fiber is bad. Even with regular copper wire, 90 degree bends is bad. Fiber needs a long sweeping turn, not sharp. Even with copper, it should be a sweeping turn, so that the wires do not break inside the jacket.

Yes, the idea is to have a sweeping bend, not a sharp corner, however the direction of the cable has to turn by 90 degrees and I am looking for the minimum radius of this sweeping bend. The problem is that the 4 inch wall does not allow too much of a sweep when feeding into the toslink adapter. As an analogy. There is a similar issue when hooking RG-6 coax to a wall plate where a rule of thumb is to keep the bending radius above 6 times the cable diameter.

Epson 8500UB (R); Elite Electric100 16:9; Yamaha RX-V671; Polk Monitor 60 x 2, Polk CS2, Polk Monitor 30 x 4
RamKat is offline  
post #6 of 11 Old 01-16-2012, 06:33 PM - Thread Starter
Member
 
RamKat's Avatar
 
Join Date: Aug 2007
Location: Ottawa, Ontario
Posts: 91
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by jparr View Post

That should be fine. Fiber handles a lot more abose than people think. You can test it by placing a strong flashlight up against one end and looking for light at the other.

Thanks, that is a good idea.

Epson 8500UB (R); Elite Electric100 16:9; Yamaha RX-V671; Polk Monitor 60 x 2, Polk CS2, Polk Monitor 30 x 4
RamKat is offline  
post #7 of 11 Old 01-16-2012, 08:45 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 89
The issue with bend radius for fiber is not when damage will occur. It is when internal reflections will cause a significant drop in signal. I have seen TOSLink cables with a specified minimum bend radius of 1" with less that .5dB loss. You are probably good to go, but you will have to check with the manufacturer of your cable to be sure.
Colm is offline  
post #8 of 11 Old 01-17-2012, 05:34 AM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
Quote:
Originally Posted by RamKat View Post

Yes, the idea is to have a sweeping bend, not a sharp corner, however the direction of the cable has to turn by 90 degrees and I am looking for the minimum radius of this sweeping bend. The problem is that the 4 inch wall does not allow too much of a sweep when feeding into the toslink adapter. As an analogy. There is a similar issue when hooking RG-6 coax to a wall plate where a rule of thumb is to keep the bending radius above 6 times the cable diameter.

You should still be able to get a sweeping turn going up into the wall, from where it enters, or use a wall plate, with a right angle 90 attached on the back. http://search.yahoo.com/search;_ylt=...r=toslink%2090
gregzoll is offline  
post #9 of 11 Old 01-17-2012, 03:38 PM - Thread Starter
Member
 
RamKat's Avatar
 
Join Date: Aug 2007
Location: Ottawa, Ontario
Posts: 91
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by gregzoll View Post

You should still be able to get a sweeping turn going up into the wall, from where it enters, or use a wall plate, with a right angle 90 attached on the back. http://search.yahoo.com/search;_ylt=...r=toslink%2090

Thanks gregzoll - this is just what I have been looking for!

Epson 8500UB (R); Elite Electric100 16:9; Yamaha RX-V671; Polk Monitor 60 x 2, Polk CS2, Polk Monitor 30 x 4
RamKat is offline  
post #10 of 11 Old 01-17-2012, 04:19 PM
Member
 
jparr's Avatar
 
Join Date: Jan 2006
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by RamKat View Post

Thanks gregzoll - this is just what I have been looking for!

The extra connector losses will be higher than any loss from the bend. Either should be fine though.
jparr is offline  
post #11 of 11 Old 01-26-2012, 05:40 PM - Thread Starter
Member
 
RamKat's Avatar
 
Join Date: Aug 2007
Location: Ottawa, Ontario
Posts: 91
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by jparr View Post

The extra connector losses will be higher than any loss from the bend.

Yup, I have proven that. Received the cable earlier tonight and did some tests outside the wall with my current TV/ AV receiver setup. Bending the cable (on both ends) to allow it to fit inside a 4 inch wall results in a working setup, adding the 90 degrees couplers with straight cables does not work (even though I can see the red light at the other end)

Epson 8500UB (R); Elite Electric100 16:9; Yamaha RX-V671; Polk Monitor 60 x 2, Polk CS2, Polk Monitor 30 x 4
RamKat is offline  
Reply Dedicated Theater Design & Construction

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off