How do I draw fiber-optic lines in a schematic?

[Eeyore]

It has to be different, it's not a trace. Understanding a large
complicated signal maze is tough if you can't instantly see what's an
electrical path and what is fiber-optic.

I just re-thought it and considered that word 'optical' alongside the 'wire'
would serve its purpose well.

Graham

 

[qrk]

Since it's functionally a connection I see no special need to make it any
different to a wire (or bus come to that).

Graham

In a schematic, the fibre optic line needs to be a drawing entity, not
a wire. Don't want the FO line to be included in a netlist.

 

[Joerg]

In a schematic, the fibre optic line needs to be a drawing entity, not
a wire. Don't want the FO line to be included in a netlist.

That's a gray area. Sure, until some major technical breakthrough
happens we won't see embedded FO in any kind of board material. But
often one wants to provide a silk screen track so the production guys
have an easier time lining stuff up and making sure it runs through the
intended tie-downs.

 

[Joerg]

Just use a schematic symbol linked to a footprint with zero copper pads? At
least in the tools I use, zero pads/pins is perfectly legal for any footprint,
schematic symbol, etc.

AFAIK my CAD does allow that. However, then I'd have to define straight
parts and bends and stack them along piece by piece, just like laying
roof tile (got a back pain last time I did that ...).

 

[Archimedes' Lever]

In a schematic, the fibre optic line needs to be a drawing entity, not
a wire. Don't want the FO line to be included in a netlist.

Yes, or it messes up circuit layout software. However, would it be too
much to ask the PCB software industry to make proviso for removing a
"node" from a netlist during certain checks.

In other words, the capture and layout software needs to be better
integrated such that the elements drawn in one can be counted as what
they are, when the other is being run.

That way, non-conducting "circuit elements" can be included in a
schematic, and the layout app doesn't have a shit fit.

I am sure these tools are already in place, and that users are simply
not designating certain circuit elements properly to keep them off the
netlists used for layout.

 

[Archimedes' Lever]

That's a gray area. Sure, until some major technical breakthrough
happens we won't see embedded FO in any kind of board material. But
often one wants to provide a silk screen track so the production guys
have an easier time lining stuff up and making sure it runs through the
intended tie-downs.

Grooves and slots ARE allowed in PCBs, and a slot can be on a per layer
basis, so yes, one can make a proviso for a dedicated channel to lay an
optical link into.

We had HV PCBs that had perpendicular slots in the top layer under the
HV caps, so that the cap could be fully encapsulated in potting media.

So they went pad, slot, pad, and the slots were wider than the part by
about 30% (15% on each side).

Our HV failures were reduced, and the PCB house said it did not affect
board costs as those operations are a normal part of PCB manufacture.

We could cut slots as narrow as 35 mils. according to our PCB house.

 

[JosephKK]

Hello Folks,

Got a design coming up where there will be lots of fiber-optic parts
within the electronics. Has to be that way because it's fast stuff and
the only way for others to understand is if I draw the FO lines and the
respective parts into the schematic. No problem to generate nice models
for the parts but:

What is the standard or custom for FO lines from one part to another?
Use fat rounded bus lines? Some kind of "hollow" traces?

Personally, i just use normal lines interrupted with circles with
double arrows inside.

 

[Archimedes' Lever]

Personally, i just use normal lines interrupted with circles with
double arrows inside.

How are "waveguide" links in microwave transmitters drawn
schematically, yet not included on layout netlists?

 

[Rich Grise]

It has to be different, it's not a trace. Understanding a large
complicated signal maze is tough if you can't instantly see what's an
electrical path and what is fiber-optic.

http://mysite.verizon.net/richgrise/images/Fiber.bmp

Cheers!
Rich

 

[JosephKK]

Thanks, Mark! I guess that settles it then. Gotta make a double-arrow
symbol now but with Cadsoft Eagle graphics stuff is fairly easy. One
just has to plug the ears when the ERC horn blares (it doesn't like
lines going through parts). Or I'll try a bitmap import.

Most of the implementations that i have seen "interrupt" the line for
the circle. Better CAD systems can incorporate the circle as part of
a line pattern.