| Title: | FDDI - The Next Generation |
| Moderator: | NETCAD::STEFANI |
| Created: | Thu Apr 27 1989 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2259 |
| Total number of notes: | 8590 |
Hi, I have been asked if our single mode options (specifically in the concentrator) "automatically shut off transmit power/light when they detect light lost on the receive port". This customer is a PTT and many of their current laser boxes do this, which makes them "safe" to work on when there is a cable fault (their definition of safe). I believe this can't happen as the concentrator will be trying to establish the link all the time, but need confirmation please. As an alternative, if (through elms/elm) the port is "disabled" then am I correct in believing that there is NO light transmitted at all. Thanks, Steve
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 335.1 | KONING::KONING | Eesti vabaks! | Wed Aug 28 1991 11:27 | 16 | |
All FDDI nodes will continue to send a signal (i.e., have light on) even
though light is off on their input -- so long as the port is enabled.
This is unavoidable for two reasons:
1. The FDDI standard requires it
2. The protocol is symmetrical, so it is impossible to wait for light before
sending light, because then both sides would wait forever.
("after you".... "no, after you...")
On the other hand, disabling the port unconditionally shuts off its light.
You might also remind the customer of the fact that our single mode products
are in one of the lower categories as far as lasers go. I don't remember
the specifics, but I know we did something special to help in that area.
paul
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| 335.3 | Thanks | COMICS::WOODWARD | Smile! | Wed Aug 28 1991 11:38 | 0 |
| 335.4 | DEC FDDI Single Mode Fiber is safe... | SAAR::B_GOODWIN | Time is an illusion... | Wed Aug 28 1991 13:16 | 8 |
Note .2 was deleted because of some concern as to the correctness of
the reply and the saftey issues involved.
After doing more research it was found that the laser used in our (DEC)
Single Mode FDDI products is 100% safe and cannot cause any kind of eye
damage short of poking yourself in the eye with the fiber when you look
into it. But a good rule of thumb it "Never look down fiber, you might be
mistaken on what is launched into it!"
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