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Q: Power over telephony wiring ( Answered 5 out of 5 stars,   1 Comment )
Subject: Power over telephony wiring
Category: Science > Technology
Asked by: marquis2-ga
List Price: $100.00
Posted: 08 Sep 2005 16:23 PDT
Expires: 08 Oct 2005 16:23 PDT
Question ID: 565860
In North America, during the mid-1990s, several telecom companies
(e.g. Bell Canada) installed netwoks that were powered remotely using
phone lines.  I'd like to find dated resources that show and explain 
how remote power was done at that time. (Not how it's being done
recently, say 2002-present.)

The topic above is the main question. Any insights into what prevented
this technology from being more widely adopted at that time, would
also be welcome.

Request for Question Clarification by pafalafa-ga on 08 Sep 2005 16:43 PDT

Can you explain a bit more about your understanding of this technology?

What sort of network are you talking about?  What is it that is being
powered by the telephone lines?  What more can you tell us about the
Bell Canada experience?  Or, for that matter, any more recent examples
of this technology?

I just want to make sure we get started on the right track.  Any
additional information would be helpful.



Clarification of Question by marquis2-ga on 08 Sep 2005 18:29 PDT
Can you explain a bit more about your understanding of this technology?
It is used with fibre communications networks.  The fibre works quite
well to transmit information, but can't transmit power.  One solution
is to transmit power over the phone lines.

What sort of network are you talking about?  
Communications networks.

What is it that is being powered by the telephone lines?  
Typically, the communications equipment which receives the fiber and
converts the high-bandwidth information into a larger number of
non-fiber lines.

What more can you tell us about the Bell Canada experience?  Or, for
that matter, any more recent examples of this technology?
Here's a link to an article on a recent product:

Communications networks.

Request for Question Clarification by pafalafa-ga on 08 Sep 2005 19:13 PDT
Thanks.  I suspected that's what you were talking about, but it helps to be sure.

My question now is:  what can I do for you???

There are a few articles that address this topic head-on, but so far,
most of the ones I'm finding are in commercial databases, and not
online in a directly-linkable way.

I cannot post these articles, since they are copyrighted, but I can
certainly cite them and provide some excerpts.

For instance, here's one that looks interesting:


Power Technologies:  Putting power into the field 

19 April 1993
Electronic Engineering Times 

With the growing use of remote network electronics, telephone
companies must decide how to provide power in the field. In the past,
telephone companies powered all the equipment connected into the
network from a central office, equipment hut or vault through the
twisted pair used to make the connection. More recently, an increasing
portion of the network is being converted from copper to optical
fiber...At the far end of the optical fiber, an optical network unit
(ONU) is required to convert the optical signals to electrical signals
and vice versa. The problem is that the optical fiber electrically
insulates the ONU from central office power.

...Even in copper-based installations, the need to increase the number
of subscriber lines being supported often results in the use of
multiplexers or pair-gain amplifiers. Since they are connected to the
network through copper wire, such units can be operated on a telephone
company's own dc supply. However, in some installations, the nearest
source of telco power is so far away that the voltage drop through the
twisted pair becomes significant, which complicates the design of
remote electronics.

...Low loop voltage can also affect customer-premises equipment.
Because the telephone electrical system is current based, the actual
voltage present across the terminals of a subscriber's telephones is
not important. What is important is that the voltage is sufficient to
drive at least 20 mA through the equivalent parallel resistance of
five telephones. Thus, voltages as low as 8.6 V are adequate to power
a telephone.

...some customer-premises equipment is voltage sensitive. Many
answering machines, for example, determine whether or not the
telephone has been answered by monitoring the voltage across the line.
If the telephone loop voltage is too low-typically under 25 V-the
answering machine may believe the telephone has been answered even
though it has not.

...Whether it is an optical network unit (ONU) insulated from the
copper network by optical fiber or an electronic unit that cannot be
powered from the network, a remote source of power must be provided.

...The issues surrounding power for remote ONUs, multiplexers and
pair-gain amplifiers are still unfolding. While Bellcore specifies
power dissipation per subscriber line, it does not specify how the
remote equipment is configured or how it is to be powered. There is
also a general lack of consensus among equipment manufacturers about
how best to implement the powering of remote systems.


The other articles I've seen thus far aren't quite as on-target as
this one seems to be.  Still, there's some useful information out

Would identification of a handful of such articles -- along with
relevant excertps -- meet your needs?

Or is there something more you're looking for?

Let me know.


Clarification of Question by marquis2-ga on 09 Sep 2005 07:00 PDT
The cited article is a step in the right direction because it is dated
and public  (Copyrighted, yes, but it's in the public domain.) 
However, it's more about explaining why remote power is needed.

My interest is in how remote power was done at that time.  I'd like
technical detail - diagrams, schematics, etc. to show and explain what
was being done.  I expect the best results to be dated a several years
after the 1993 article.

If we locate the right article in a commercial database, I can work
directly with the copyright holder to purchase it.  Another avenue
might be the US patent database or BellCore standards database, if
certain documents are directly related to the question.  Even non-US
patents could be helpful in understanding what was being done in this

Thanks for your efforts.

Request for Question Clarification by pafalafa-ga on 09 Sep 2005 07:51 PDT
OK.  I'm starting to zero-in on what you want.  We may still need
another round or two of clarifications, so thanks for hanging in with
the process.

Have a look at this one from 1997, and let me know how close (or not) it comes:
Power for the last fiber mile - extended fiber optical


Clarification of Question by marquis2-ga on 09 Sep 2005 10:36 PDT
This is similar to the first article in that it's more about
explaining why one wants this power. (Heat control & Saving Space and
Money) Not about how.

It helps some in that it cites a relevant Bellcore document and gives
another name for this architecture "Network Power".

Keep digging, please.

Request for Question Clarification by pafalafa-ga on 09 Sep 2005 11:10 PDT
I can see you're looking for highly technical specs, so I'll concentrate on these.

In the mean time, please have a look at one more link:

Near the top of this page, click on the "Expand All" button to see all
the paper titles.

There are quite a number of papers from the mid-1990's on your topic,
but unfortunately, not all of them are accessible at this site.  As
these are relatively brief "white papers", I don't expect that they
would have the level of detail you're seeking.  Still, if there is a
title or two of particular interest, let me know.

It may be a day or two before I have further feedback on this, so stay tuned....


Clarification of Question by marquis2-ga on 09 Sep 2005 15:38 PDT

This site is quite nice.  One of the papers here, from 1998, provides
a partial answer to my question.

Request for Question Clarification by pafalafa-ga on 09 Sep 2005 20:14 PDT
I'm quite glad to hear that.

However, it would help to know which paper best meets your needs.

And even more to the point, what other sorts of references you need to
make for a complete answer to your question.

Let me know how I can best assist you at this point.


Clarification of Question by marquis2-ga on 09 Sep 2005 22:26 PDT
This one:

"Powering Fiber in the Local Loop: FTTC and FITL Power Architectures 
Published by NFOEC Conference 1998, 9/1998
This paper maps several alternative powering strategies with two
leading classes of emerging access technology, xDSL and FTTC, for the
purpose of providing a starting point for planning successful and cost
effective power solutions."

In particular, Figures 7 & 8, and the text explaining them, provide
diagrams of two power wiring alternatives including converters,
limiters, power ratings for both supply and 'ONU' - this is helpful in
answering my question about how remote power could have been done at
that time.

What's missing?  This is one power supplier making a pitch to their
customers.  Now I know what a supplier thought, but what did the
telecom companies think?  Better, what did they actually do?

I'd like to find a couple more documents with similar detail on this
narrow topic.
Thanks for your help.

Request for Question Clarification by pafalafa-ga on 10 Sep 2005 04:46 PDT
Almost all the searching I've done thus far leads me back to the Alpha
Technologies site -- they've clearly had a lot to say on this topic,
and are recognized as leaders on the issue (at least in terms of their
presence at conferences, etc).

Take a look at this one brief mention in this Telcordia (the successor
to Bellcore) document:

The relevant mention is on page 45:

Issue A, March 1998

This document describes the
Environmental and Installation
Requirements, as well as the Powering and
Grounding options for U S WEST
Communications Telecommunications
Equipment to be placed on the Customers'
Premises.  services that require the placement of
U S WEST digital multiplexing and/or
switching equipment. The space may be
wholly owned by the customer, leased by
U S WEST, or owned by the building owner
or another tenant. In other words this document
covers all Customer Premises applications.

It looks to be a company-specific powering specification for equipment
which includes power to fiber networks.  It's a bit hard to be sure.

There are tidbits throughout the entire document here, on ONUs, FITL
systems, and so on...worth a scan.

Stay tuned...


Request for Question Clarification by pafalafa-ga on 10 Sep 2005 10:42 PDT
Here's another from 1998 that looks to me to be on the money (though I
admit...I'm still a bit hazy on some of the technical details here):

Implementation Strategies for Advanced Access Networks
Deliverable 13: FTTH Architectures, Services and Technical Issues

This has a more European focus, but seems to provide a level of
specifics that may be useful.

And yet another that has not date, but judging from the url, it looks
to be a 1997 document:
Local Powering Solutions for Fiber To The Home (FTTH) Technology

Let me know your thoughts at this point, in terms of what we have thus
far, and what more you'd like to have.


Request for Question Clarification by pafalafa-ga on 10 Sep 2005 15:57 PDT
Hey!  Here's a pretty comprehensive overview from 1998 -- bit more
focused then the last one posted -- though it's not specific to a
given company or technology:
Implementation Strategies for Advanced Access Networks
FTTH Architectures, Services and Technical Issues:
Definition of the Suitable Powering Issues

Do you think you have enough at this point, or is there more that you need.

Looking forward to hearing back from you.


Clarification of Question by marquis2-ga on 10 Sep 2005 18:26 PDT

I'm sorry, I meant to respond earlier but I've been busy with the
papers and links that you've found.  (Don't know if you noticed, but
some of it is rather dry reading.)

Anyway, I finding what I needed in your answers, so yes, I think we have enough.  

Thanks for your help.
Subject: Re: Power over telephony wiring
Answered By: pafalafa-ga on 10 Sep 2005 18:48 PDT
Rated:5 out of 5 stars

I tried quite a number of different searches as I learned more and
more about what you were looking for.  The search that turned out to
be most fruitful was this Google search:

[ "network power" OR powering onu OR onus 1993..1999 ]

You might want to look over the search results, which are here:


if you find you'd like to explore additional documents.  

I'd also recommend a visit to this site:

as it has a lot of 'historical' information on this particular
technology, even if it's a tough site to navigate and actually open up
the documents of interest.

This has been an interesting challenge...thanks for posting your
question at Google Answers.

You are welcome to rate or comment on the answer you've received.  But
before you do so, please let me know if there's anything else you
need.  Just post a Request for Clarification, and I'm at your service.

All the best,

marquis2-ga rated this answer:5 out of 5 stars and gave an additional tip of: $10.00
My question was more technical than I thought, which required several
In the end, I got the answer I needed.

Subject: Re: Power over telephony wiring
From: pafalafa-ga on 11 Sep 2005 07:40 PDT
Thanks a lot.

Hope we'll see you back here one day soon.


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