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Telco line question

  • Thread starter Paul Hovnanian P.E.
  • Start date
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Paul Hovnanian P.E.

Jan 1, 1970
0
If anyone is familiar with telco construction practices, maybe they can
answer this one.

The local telco was installing a brand new overhead line from the
central office near me a few months ago. I stopped by and asked one of
the linemen what kind of cable they were stringing and he told me it was
thousand pair, 26 gauge (why they are still using such old technology is
a topic for another post). Later, I noticed that every few blocks, where
they had to tie into an underground lateral, they would route the cable
down a pole, into a splice cabinet and then back up the pole to continue
on. When transitioning from the overhead line to the riser on the pole,
they installed a splice box on the overhead line and then run a separate
section of cable down the riser, through some conduit and into the
cabinet. The downstream circuit goes back up the pole and into another
overhead splice. As far as I can tell, all of the pairs are spliced and
routed through the underground section. There are only two cables in and
out of the overhead splices, so I assume that they aren't splitting a
subset of the cable pairs out and running it to the cabinet.

My question is: Why can't the overhead cable be routed through the short
sections of conduit and into the splice cabinet? It appears that the
labor to make up each overhead splice is about a week for one person,
which is not cheap. Its probably more expensive to make the overhead
splices (working up a pole) than it is to work in a ground level cabinet
(not a vault, just a pedestal style cabinet).
 
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Paul Hovnanian P.E.

Jan 1, 1970
0
Floyd L. Davidson said:
You probably *should* make another post. What is it about 26
gauge copper cable that you think inappropriate today?

Good question. I'm not familiar with the state of the art, but some
other companies are going 100% fiber for new installations to within a
few thousand feet of their customers. This is a 5 mile circuit from the
CO.
That is unlikely, though with a 1000 pair cable it might be.
Probably some suitable subset of the total actually break out at
the junction box, even if they all do go down the pole. It is
also likely that the cabinet at the bottom of the pole contains
a variety of equipment, in addition to a junction box. There
could be loading coils, T1 repeaters, cable carrier, or even an
entire remote switching unit.

Actually, I got a peek inside one. No such equipment, Just terminal
blocks.
But even if there is no cable between two overhead splice boxes
(in which case clearly all pairs do go to the cabinet below)
that would not necessarily mean that all pairs are broken out
and made available in side the cabinet.

True. But they did terminate everything running into the splice box from
the overhead cable. They may have run a smaller group down the pole into
the cabinet and left some pairs unused, but eventually they will have to
make up some more splices overhead or the cable's capacity can't be
used.
The overhead cable and the cable going down the pole are of
different physical construction. I doubt the overhead cable can
be bent into a tight enough curve to bring it down the pole.

They can turn some pretty tight corners with the overhead cable. In fact
the underground cable looks like it doesn't bend as well.

I used to work for a local power company and some of the stuff we pulled
through vaults and up risers didn't bend very well. You just use larger
radius conduit.

Also, the economics of installing utilities is such that labor is most
of the cost, not the materials. I'd think one would spend more on the
equipment if one can save a few thousand splices.
 
T

TimPerry

Jan 1, 1970
0
Paul Hovnanian P.E. said:
Good question. I'm not familiar with the state of the art, but some
other companies are going 100% fiber for new installations to within a
few thousand feet of their customers. This is a 5 mile circuit from the
CO.


Actually, I got a peek inside one. No such equipment, Just terminal
blocks.

they could be getting ready to roll out DSL. this requires a DSLAM every
15,000 ft (to subscriber)
 
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Paul Hovnanian P.E.

Jan 1, 1970
0
Floyd L. Davidson said:
Fiber is fine between telco facilities, but is not viable for
customer loops. Or, it is not viable without also having some
form of copper along with it, to supply emergency power. As a
result you'll see a great deal of long haul fiber, but most
local outside plant is still going to be copper for quite some
time into the future for residential areas, and much so even
for local distribution in business areas.

I don't think we'll be seeing fiber subscriber loops for quite some
time. But I'd expect a more rapid migration to digital (either copper or
fiber) feeders up to some local cabinets where the conversion is done.

The local cable TV company is pretty sucessful at maintaining their CATV
and digital telephone services with pole mounted battery packs every few
thousand feet.
We might note too that the state of the art with 26 gauge cable
is vastly different than it was say 3 decades ago. Both the
cable itself (which once used paper insulation and now uses
plastics) and the equipment directly connected to it are modern
technology.

Its possible that the telco wants to stick with copper and go with some
sort of high bandwidth over copper technology. In the future, that is.
Was that after the project was completed? If so, that explains even
more about why it is copper. This must be a feeder line, from which
a number of other cables cross connect to route to individual drop
locations??? Hence, with a 1000 pair cable there might be something
like 10 of these junction boxes, each with perhaps 200 pairs (some of
which show up at other junction boxes too). (Given your later comment
about "underground cable", this probably feeds a network of buried cables
that go down individual streets to homes?

Yes. Every few blocks, this feeder dips underground to a splice cabinet
and then goes back overhead again. All of the neighborhoods have
underground wiring. When I peeked into an open cabinet one day, there
appeared to be 4 or 5 cables entering it. Other then the two risers,
these go into the local neighborhoods.
I'm not getting a clear enough picture yet of what you are
seeing to be sure what it is. If there are one or two splice
boxes on the pole, and there is a cable between them,

No. That's the point. There is no cable between the OH boxes. They
appear to transition the overhead cable into an underground drop into a
splice cabinet.
then you
can be fairly certain that not all of the pairs appear at the
junction box in the cabinet at the bottom of the pole. That's
pretty much standard procedure.

Then, I'd expect to see a single OH splice box and a single riser from
the pad mounted cabinet. That would still save them one set of overhead
splices compared to what they have now.
But even if they ran the whole
1000 pairs down the pole and back up, I doubt they would want to
put 1000 terminals in at each pole rather than just splice 8 or
9 hundred of them. Usually the splicing would be done on the
pole, not in the cabinet though.


Underground cable? I'm confused about what is there. Aerial
cable and underground cable are indeed going to be different
things, as is the cable coming down the side of the pole to the
cabinet.

This is how it is set up (view with fixed font):

oh splice oh splice
from CO +---+ +---+ to next riser
-------- oh cable -----+ +-+ +-+ +----- oh cable ------>
+---+ | | +---+
| |
| |
| | +---------+
cable risers in conduit(2) ->| | | | padmound cabinet
| | | |
| | ++---+---++
| | | | |
| +------+ | |
+--------------+ V
ug laterals


The major question I have is why they can't eliminate the two OH splice
boxes and just run the overhead cable down through the conduit runs into
the cabinet. Then, make up whatever splices in there just once.
I was assuming that whatever comes down the pole necessarily has
some tight bends in it.

No tighter than a bend in the overhead line turning a corner in mid
span.
 
A

Anthony

Jan 1, 1970
0
The method our teleco has been using for the last several years, is fiber
to the neighborhood. They set up a medium sized (appears to usually be
either a single or double 4') padmount box near the neighborhood, and run
fiber to it from the main switch building. From there throughout some set
radial distance, it is copper wire.
All runs between main switch buildings are ug fiber, and have been for many
years. They are actively replacing long copper runs with the fiber/box set
up all over the area. This teleco does offer DSL, and this seems to play
into the design of the system.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email
 
J

John Gilmer

Jan 1, 1970
0
We might note too that the state of the art with 26 gauge cable
is vastly different than it was say 3 decades ago.

I went on a tour of NJ Bell a little over 30 years ago. This was a week
long effort to let us know what the "real world" was like.

Anyway, the technology was fairly mature by then. The "new" cables had
plastic insulation rather than paper and the various "splice" gadgets were
in common use. Bell Labs had computer programs to simulate these wires so
that the operation of special circuits could be predicted. While I'm sure
there was some room for progress I doubt that someone who went to sleep 30
years ago would be very surprised by the copper wire part of the "outside
plant" today.

The Bell System liked to have as much of the equipment safely in climate
controlled buildings rather than in boxes on the ground or on poles or in
the customers' buildings. It's just easier to maintain (and power) stuff
in the central office than out in the middle of nowhere.

Back then, the cost of your basic POTS wire was on the order of
$50/pair/mile. (That's everything: cable, splices, poles, whatever.) Even
in you factor in inflation, that's low enough to want to keep the fancy
stuff in the CO as much as possible.

Beyond some point, of course, they have to install equipment outside of a CO
(or "wire center"). But copper wire is plenty good for most customers.


Both the
cable itself (which once used paper insulation and now uses
plastics) and the equipment directly connected to it are modern
technology.

"Modern," as in less than 40 years old, maybe.

"Modern," as in less than 5 years old, I don't think so.
 
T

Tom Lager

Jan 1, 1970
0
[email protected] (John Gilmer) wrote in
I went on a tour of NJ Bell a little over 30 years ago. This was a week
long effort to let us know what the "real world" was like.

Anyway, the technology was fairly mature by then. The "new" cables had
plastic insulation rather than paper and the various "splice" gadgets
were in common use. Bell Labs had computer programs to simulate these
wires so that the operation of special circuits could be predicted.
While I'm sure there was some room for progress I doubt that someone who
went to sleep 30 years ago would be very surprised by the copper wire
part of the "outside plant" today.

The Bell System liked to have as much of the equipment safely in climate
controlled buildings rather than in boxes on the ground or on poles or
in the customers' buildings. It's just easier to maintain (and power)
stuff in the central office than out in the middle of nowhere.

Back then, the cost of your basic POTS wire was on the order of
$50/pair/mile. (That's everything: cable, splices, poles, whatever.)
Even in you factor in inflation, that's low enough to want to keep the
fancy stuff in the CO as much as possible.

Beyond some point, of course, they have to install equipment outside of
a CO (or "wire center"). But copper wire is plenty good for most
customers.




"Modern," as in less than 40 years old, maybe.

"Modern," as in less than 5 years old, I don't think so.
It is possible that the system spec's, or whatever VZ is using today in
place of the old BSPs, say that for underground applications jelly filled
cable must be used, thus the necessity of a splice at each riser.
As to 26 Ga copper being "old", it depends on the application. In short
distance, urban applications, it is probably as viable both technically and
economically as fiber.
Fiber to the premise, using passive optical networks, is beginning to be
deployed in the local loop more and more. Subscriber interfaces with
battery backup are approaching the reliability of wireless, but have a long
way to go before matching copper. That being said, there are continuing
breakthroughs both in batterey technology and circuit design that will
extend the battery life and eventually approach copper reliability. I
don't think it's going to be long before customers and regulators begin to
accept a trade-off of bandwidth for emergency availability.
 
J

John Gilmer

Jan 1, 1970
0
It is possible that the system spec's, or whatever VZ is using today in
place of the old BSPs, say that for underground applications jelly filled
cable must be used,

One of the interesting things I leaned on my tour 30 years ago was that the
"jelly" stuff was introduced because when the plastic insulation got wet the
water would travel up and down the cable and "find" every pin hole in your
1000 pair (or whatever) cable until the next splice. The old paper
insulation would swell and confine the damage to a short section. With
"luck" and some dry nitrogen the cable might be kept in service. The
original jelly was some stuff that resisted most normal solvents so it was a
messy PITA to splice. That definitely would be an area where one would
home some improvements have been made.

thus the necessity of a splice at each riser.
As to 26 Ga copper being "old", it depends on the application. In short
distance, urban applications, it is probably as viable both technically and
economically as fiber.
Fiber to the premise, using passive optical networks, is beginning to be
deployed in the local loop more and more. Subscriber interfaces with
battery backup are approaching the reliability of wireless, but have a long
way to go before matching copper. That being said, there are continuing
breakthroughs both in batterey technology and circuit design that will
extend the battery life and eventually approach copper reliability. I
don't think it's going to be long before customers and regulators begin to
accept a trade-off of bandwidth for emergency availability.

Maybe. But I always keep one "low tech" telephone about just in case the
power fails.

There's a guy who works for the telephone company in one of the churches we
go to. Next time I see him I will try to pump him for information. He
may just know enough to do his job and nothing else, however.
 
J

John Gilmer

Jan 1, 1970
0
I was at Bell Labs in 1949. We sent base-band video, (B&W), over 26 GA
copper all over Manhattan. It did require a bit of "equalization".

Later, at Holmdel, I worked on "guided wave" technology. The idea was
to use a TE01 waveguide to achieve large bandwidths. The "optical
waveguide" has proved much more practical.

My, my!

I spent the winter of 1973/74 at Holmdel.

That was around the time it finally sunk in that AT&T had wasted HUNDREDS
(in 1960s $dollars) of $millions lars trying to make "PicturePhone" work on
your POTS wires.

Without fiber to the premise, a lot more can be done with copper. A
simple example with large economic pay-back, is to replace manual
electrical, water, and gas meter reading with data sent back on the
existing premise wiring. This requires no technological break-through,
but does involve mundane things like company structure and unions
objection.

Well, there are two generations of technology beyond that.

First generation required the meter reader to "wave a wand or point a LED
gadget toward the meter. The second generation just requires the meter
reader to just drive about the neighborhood. In the case of the water
meter, I think it requires that the batteries be replaced every few years.
I suppose that the next "breakthrough" would have the batteries be charged
by the water flow.
Moving away from base-band signaling has probably saved more POTS
bandwith than anything else, independant of the transmission medium.

One thing seems to be certain: The use of bandwidth will rise to meet
its availability, even though we may not now even know its uses!
AT&T thought they could sell "picturephones" using the new bandwidth.

As mentioned, "Picturephone was one of the two or three BIG mistakes taken
by AT&T management.

(In case you wonder, the 2nd was the decision to get out of "military work"
a few years before RR was elected.)

The 3rd was the decision to overspend on fiber and cell phones and other
"broad band" nonsense. AT&T had a REVERSE SPLIT to keep its stock listed
on the Big Board.
 

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