Do I ground and if so, how?

[wxstevens]

After pulling several runs of SM fiber optic, I began terminating today. I began stripping the outer sheath and it has a metal protective cover similar to metal flex. Should this metal be grounded and if so, how would you go about it?

 

[MisterCMK]

Usually the splice/termination enclosure has a lug or clamp to bond the metal sheath.

 

[don_resqcapt19]

As to the question, "should I ground it?", the answer is yes.

770.101 Grounding.
Non–current-carrying conductive members of optical fiber cables shall be grounded according to the grounding methods specified by 770.100.

 

[mcclary's electrical]

I'm not sure what this is going on,,,but I've been behind several Fios guys that grounded the fibre, but never brought a ground wire to the FIOS box. Customer gets humming in phone

 

[dbuckley]

I would suggest that grounding a fibre sheath at all is a questionably bad idea, and grounding it at both ends is a terrible idea.

The OP states he's using single mode fibre, which typically goes long distances (up to 20KM), which in electrical terms could mean between services, and thus you are placing a path between different ground points. Given that the foil sheath is conductive, but quite weedy, the current flow could cause heating or even failure of said sheath. If the PoCo MGN is shoddy, or the distance is long, then you could have a lot of volts between the two ground points and have that reflected across the fibre. That of course then creates a hazard for the installer.

Additionally, we IT folk assume that fibre is true isolation, and we dont want a lightning strike from building A being propogated into building B along the fibre.

 

[mcclary's electrical]

I would suggest that grounding a fibre sheath at all is a questionably bad idea, and grounding it at both ends is a terrible idea.

The OP states he's using single mode fibre, which typically goes long distances (up to 20KM), which in electrical terms could mean between services, and thus you are placing a path between different ground points. Given that the foil sheath is conductive, but quite weedy, the current flow could cause heating or even failure of said sheath. If the PoCo MGN is shoddy, or the distance is long, then you could have a lot of volts between the two ground points and have that reflected across the fibre. That of course then creates a hazard for the installer.

Additionally, we IT folk assume that fibre is true isolation, and we dont want a lightning strike from building A being propogated into building B along the fibre.

Then how do you comply with 770. 100?

 

[dbuckley]

Then how do you comply with 770. 100?

Thats a very good question.

The only reasonable answers I can think of are:

* get 770.100 repealed because its wrong (and preferably before someone gets electrocuted)
* use fibre without metallic sheathing
* contract data installers who know nothing of the NEC ('cos it doesn't apply to computer signal wiring, right???) to do the terminations.

 

[K8MHZ]

Thats a very good question.

The only reasonable answers I can think of are:

* get 770.100 repealed because its wrong (and preferably before someone gets electrocuted)
* use fibre without metallic sheathing
* contract data installers who know nothing of the NEC ('cos it doesn't apply to computer signal wiring, right???) to do the terminations.

This may interest you:

However, with respect to the inside configurations, Mr. McCoy believes?and
Verizon concurs?that the intent of the NEC was not to require bonding to a power
company ground (or to one of the alternative grounding sources mentioned in Staff?s
letter). Rather, Mr. McCoy informed the company that where the ONT is not connected
to any conductors exposed to the environment outside the customer?s building (and thus
where there is no risk of a lightning strike or power-line contact), NEC Article 770 and
Chapter 8 do not apply.

http://docs.google.com/viewer?a=v&q...OrIaOk&sig=AHIEtbS0GUn7jvVs-d8La-OKGu48dc5oXQ

 

[dutchparson]

After pulling several runs of SM fiber optic, I began terminating today. I began stripping the outer sheath and it has a metal protective cover similar to metal flex. Should this metal be grounded and if so, how would you go about it?

I don't think it's a good idea

 

[zbang]

That doc is also available at http://www.dps.state.ny.us/08v0835_Letter_to_Staff_Re_Grounding_and_Bonding.pdf (a friend mentioned it to me.)

Customer gets humming in phone

Unlikely that it's due to the fiber sheath grounding. More likely there's an unintentional ground on the inside wiring of the phone line.

 

[mcclary's electrical]

That doc is also available at http://www.dps.state.ny.us/08v0835_Letter_to_Staff_Re_Grounding_and_Bonding.pdf (a friend mentioned it to me.)



Unlikely that it's due to the fiber sheath grounding. More likely there's an unintentional ground on the inside wiring of the phone line.

All interior wiring was checked and it was fine. The noise was definately a 60 cyle hum being induced on the incoming fiber. It was exceptionally strong when the house was isolated

 

[Smart $]

Then how do you comply with 770. 100?

Thats a very good question.

The only reasonable answers I can think of are:

* get 770.100 repealed because its wrong (and preferably before someone gets electrocuted)
* use fibre without metallic sheathing
* contract data installers who know nothing of the NEC ('cos it doesn't apply to computer signal wiring, right???) to do the terminations.

Back up a step or two

III. Protection
770.93 Grounding or Interruption of Non–Current-
Carrying Metallic Members of Optical Fiber Cables..
Optical fiber cables entering the building or terminating on
the outside of the building shall comply with 770.93(A) or
(B).
(A) Entering Buildings. In installations where an optical
fiber cable is exposed to contact with electric light or power
conductors and the cable enters the building, the non–
current-carrying metallic members shall be either grounded
as specified in 770.100, or interrupted by an insulating joint
or equivalent device. The grounding or interruption shall be
as close as practicable to the point of entrance.
(B) Terminating On the Outside of Buildings. In installations
where an optical fiber cable is exposed to contact
with electric light or power conductors and the cable is
terminated on the outside of the building, the non–currentcarrying
metallic members shall be either grounded as
specified in 770.100, or interrupted by an insulating joint or
equivalent device. The grounding or interruption shall be as
close as practicable to the point of termination of the cable.

It doesn't say where the exposing to electric light and power conductors must occur, does it?... and it doesn't specify any particular conductor(s), does it?. The grounding conductor(s) is connected to the electric light and power system, isn't it?

 

[don_resqcapt19]

All interior wiring was checked and it was fine. The noise was definately a 60 cyle hum being induced on the incoming fiber. It was exceptionally strong when the house was isolated

I don't think that is possible. Current or voltage does not have any effect on the signal transmitted in the glass fiber. The noise or hum can only be induced at or after the point where the light signal is changed to an electronic signal.

 

[mcclary's electrical]

I don't think that is possible. Current or voltage does not have any effect on the signal transmitted in the glass fiber. The noise or hum can only be induced at or after the point where the light signal is changed to an electronic signal.

Again, with the house TOTALLY isolated, and a test set direct wired into the fios box, the hum was there, completely isolated from the house. It HAD to have been being induced on the metal shielding from being too close to the laterals. The hum was not coming from the house

 

[hurk27]

Again, with the house TOTALLY isolated, and a test set direct wired into the fios box, the hum was there, completely isolated from the house. It HAD to have been being induced on the metal shielding from being too close to the laterals. The hum was not coming from the house

To relate what Don is trying to say is fiber does not have any electrical properties, so there is no way a 60hz hum can be induced into the fiber itself, now if the test equipment and or phones has some connection to this metal outer covering, it may be possible they are amplifying it in some way, but I really don't believe it references this shield in any way, my bet is it is being injected in at the A/D converters before it hits the fiber, 60hz, is an audio frequency digital would ignore it, and any amplification will allow a very small level get into the signal pathway very easy at the head end.

 

[hurk27]

I don't think that is possible. Current or voltage does not have any effect on the signal transmitted in the glass fiber. The noise or hum can only be induced at or after the point where the light signal is changed to an electronic signal.

Or "at or before where the electronic signal is changed to a light signal"?

 

[Volta]

As to the question, "should I ground it?", the answer is yes.

Then how do you comply with 770. 100?

As Smart$ pointed out, 770.100 doesn't require us to ground all FO sheaths, but show how to "Where" it is grounded.

 

[zbang]

Again, with the house TOTALLY isolated, and a test set direct wired into the fios box, the hum was there, completely isolated from the house. It HAD to have been being induced on the metal shielding from being too close to the laterals.

Sounds like the ONT might be bad. Has it been swapped?

 

[mrcanby]

After pulling several runs of SM fiber optic, I began terminating today. I began stripping the outer sheath and it has a metal protective cover similar to metal flex. Should this metal be grounded and if so, how would you go about it?

bonding bushing

 

[mcclary's electrical]

bonding bushing

got a link?