U.S. patent application number 12/315348 was filed with the patent office on 2009-03-26 for ground control unit for cable locating.
Invention is credited to John K. Boland, Hossein Eslambolchi, John Huffman, Claywell D. Turley.
Application Number | 20090079433 12/315348 |
Document ID | / |
Family ID | 38178765 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090079433 |
Kind Code |
A1 |
Eslambolchi; Hossein ; et
al. |
March 26, 2009 |
Ground control unit for cable locating
Abstract
A system and method for selectively grounding each of a
plurality of short-haul buried utility conveyances coupled to a
common long-haul buried utility conveyance to enable a conveyance
locating signal transmitted through the long-haul conveyance to
travel from the long-haul utility conveyance to a selected
short-haul utility conveyance. The system includes a first optical
switch for selecting each of the plurality of short-haul utility
conveyances to be grounded, where the first optical switch is
adapted to receive an optical signal and selectively output the
optical signal on one of a plurality of optical fibers; and a
second optical switch coupled to each of the plurality of optical
fibers for grounding each short-haul utility conveyance in response
to the optical signal on a corresponding optical fiber.
Inventors: |
Eslambolchi; Hossein; (Los
Altos Hills, CA) ; Huffman; John; (Conyers, GA)
; Boland; John K.; (Dover, DE) ; Turley; Claywell
D.; (Covington, GA) |
Correspondence
Address: |
AT&T CORP.
ROOM 2A207, ONE AT&T WAY
BEDMINSTER
NJ
07921
US
|
Family ID: |
38178765 |
Appl. No.: |
12/315348 |
Filed: |
December 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10748882 |
Dec 30, 2003 |
7467227 |
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12315348 |
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11804256 |
May 17, 2007 |
7463034 |
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10748882 |
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11289996 |
Nov 30, 2005 |
7235960 |
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11804256 |
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Current U.S.
Class: |
324/326 |
Current CPC
Class: |
G01R 29/085
20130101 |
Class at
Publication: |
324/326 |
International
Class: |
G01V 3/11 20060101
G01V003/11 |
Claims
1. A method for selectively grounding each of a plurality of buried
short-haul utility conveyances coupled to a common buried long-haul
utility conveyance to enable a conveyance locating signal
transmitted through the buried long-haul conveyance to travel from
the buried long-haul utility conveyance to a selected buried
short-haul utility conveyance, comprising: selecting a buried
short-haul utility conveyance to be grounded among the plurality of
buried short-haul utility conveyances by outputting an optical
control signal; selectively grounding each buried short-haul
utility conveyance in response to the optical control signal.
2. The method recited in claim 1, wherein the optical control
signal is output from an optical switch coupled to an optical
transmitter.
3. The method recited in claim 1, wherein the optical control
signal is output from an optical switch coupled to a cable locate
tone transmitter.
4. The method recited in claim 1, wherein the optical control
signal is output from an optical switch remotely operated by DTMF
control.
5. The method recited in claim 1, wherein the optical control
signal is output from an optical switch remotely operated by
cellular control.
6. The method recited in claim 1, wherein the optical control
signal is output from an optical switch remotely operated over a
network.
7. The method recited in claim 1, wherein the optical control
signal is output from an optical switch coupled to a cable locate
transmitter, and is remotely operated over a network.
8. The method recited in claim 1, wherein the optical control
signal is output from a first optical switch coupled to an optical
transmitter and a cable locate tone transmitter.
9. A method for selectively grounding each of a plurality of buried
short-haul utility conveyances coupled to a common buried long-haul
utility conveyance to enable a conveyance locating signal
transmitted through the buried long-haul conveyance to travel from
the buried long-haul utility conveyance to a selected buried
short-haul utility conveyance, comprising: selecting a buried
short-haul utility conveyance to be grounded among the plurality of
buried short-haul utility conveyances by outputting a control
signal on one of a plurality of fibers; and grounding each buried
short-haul utility conveyance upon receipt of the control signal on
a corresponding fiber.
10. The method recited in claim 9, wherein the control signal is
output by a switch remotely operated by DTMF control.
11. The method recited in claim 9, wherein the control signal is
output by a switch remotely operated by cellular control.
12. The method recited in claim 9, wherein the control signal is
output by a switch remotely operated over a network.
13. The method recited in claim 9, wherein the control signal is
output by a switch coupled to a cable locate transmitter, and is
remotely operated over a network.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional application is a continuation and
claims the benefit of U.S. application Ser. No. 11/804,256, filed
May 17, 2007, which is a continuation of U.S. application Ser. No.
11/289,996, filed Nov. 30, 2005, now U.S. Pat. No. 7,235,960.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to locating an
underground utility conveyance, and more particularly, to a method
and apparatus for selectively locating a short-haul cable or pipe
that is coupled to a long-haul (backbone) cable.
[0003] Many utilities, such as AT&T Corp., bury their pipes and
cables ("utility conveyances") underground both for reasons of
safety and esthetics. Underground burial often provides protection
to such utility conveyances against weather and other sources of
potential damage. Utilities that undertake burial of their
conveyances usually make extensive efforts to plot the location of
each buried conveyance on a map to facilitate its location in case
of repair or replacement. While a map will indicate the general
location of a buried conveyance, more precise location information
often becomes necessary, particularly in urban environments. For
that reason, most utilities that bury their conveyances underground
typically rely on electromagnetic signaling techniques to precisely
locate such conveyances.
[0004] U.S. Pat. No. 5,644,237 to Eslambolchi et al. (incorporated
by reference herein) and assigned to the assignee of the present
invention, discloses an electromagnetic signaling technique for
locating a buried utility conveyance. A signal generator applies a
locating signal and a confirmation signal to a metallic part of the
conveyance. In the case of an optical fiber cable, the metallic
part comprises either a metallic sheath or a copper trace wire
within the cable. Using a signal detector, a technician detects
both the locating signal and the confirmation signal radiated above
ground to precisely locate the buried conveyance.
[0005] Conveyance location via electromagnetic signaling works well
for long haul conveyances. However, some conveyance routes, and in
particular, certain fiber cable routes in urban areas, include one
or more short haul cables ("side-leg") cables that run between a
long-haul (backbone) cable and a telecommunications facility. Each
side leg cable connects the metallic sheath of the backbone cable
to ground, thus allowing the locating signal on the backbone cable
to pass into the side-leg cable. All other considerations being
equal, a side-leg cable having a smaller impedance (i.e., a shorter
signal path to the cable locating signal generator) will radiate a
higher strength locating signal. Conversely, the side leg cable
having a larger impedance (i.e., a longer signal path to the cable
locating signal generator) will radiate a lower strength locating
signal, making locating of such a side-leg cable more difficult. In
the past, overcoming the problem of a low-strength locating signal
on a side-leg cable required the addition of a separate locating
signal generator for that side-leg. Such locating signal generators
are expensive, and adding a separate locating signal generator for
each side-leg will greatly increase costs.
[0006] U.S. Pat. No. 6,700,380 to Eslambolchi et al. (incorporated
by reference herein) and assigned to the assignee of the present
invention, discloses a method for selectively applying a
conveyance-locating signal to each of a plurality of short haul
(side leg) underground utility conveyances, each coupled to a
backbone conveyance. In this expedient, a conveyance-locating
signal generator applies a plurality of different frequency
conveyance-locating signals to the backbone conveyance. A notch
filter, comprising a part of a filter arrestor assembly, connects
each short-haul conveyance to ground to selectively pass a
particular frequency locating signal. In this manner, each
short-haul conveyance carries a locating signal of a particular
frequency having a strength that remains unaffected by locating
signals on the other short-haul conveyances.
[0007] In view of the foregoing, there exists a need for a cable
locating system and method that enables selective grounding of the
short-haul conveyances to facilitate cable locating procedures
without the need for a technician to physically travel to multiple
locations to apply and remove the ground.
SUMMARY OF INVENTION
[0008] In accordance with an aspect of the present invention, a
system is provided for selectively grounding each of a plurality of
short-haul buried utility conveyances coupled to a common long-haul
buried utility conveyance to enable a conveyance locating signal
transmitted through the long-haul conveyance to travel from the
long-haul utility conveyance to a selected short-haul utility
conveyance. The system comprises a first optical switch for
selecting each of the plurality of short-haul utility conveyances
to be grounded, where the first optical switch is adapted to
receive an optical signal and selectively output the optical signal
on one of a plurality of optical fibers; and a second optical
switch coupled to each of the plurality of optical fibers for
grounding each short-haul utility conveyance. The second optical
switch is responsive to the optical signal on a corresponding
optical fiber.
[0009] The inventive system provides the ability to remotely
control all lateral ground points thereby eliminating the need for
a technician to travel to each customer location and manually apply
or remove the ground. This methodology reduces plant protection
time and increases the efficiency of maintenance personnel at a dig
location.
[0010] These and other advantages of the invention will be apparent
to those of ordinary skill in the art by reference to the following
detailed description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram of a grounding system in
accordance with an aspect of the invention for selectively applying
a locating tone to an isolated side-leg of a cable route.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] FIG. 1 depicts a schematic diagram of an exemplary
telecommunications system 100 that includes a long-haul (backbone)
outside the plant (OSP) fiber optic cable 102 coupled to a
plurality of short-haul side-leg cables 104.sub.1, 104.sub.2,
104.sub.3, and 104.sub.4 (collectively "side-legs 104"). The
side-legs 104 each serve a respective customer location 1-4. The
backbone cable 102 typically comprises a buried fiber optic cable
that includes one or more individual optical fibers and a metallic
sheath (not shown). The side-leg cables 104 each run from the
backbone cable 102 to a separate telecommunications facility at the
customer locations (not shown). The long-haul and short-haul cables
are also referred to as utility conveyances as will be appreciated
by those skilled in the art. Although four side-leg cables 104 are
depicted in the illustrative drawing, the cable route could include
a larger or smaller number of side-leg cables and corresponding
customer locations.
[0013] To enable the location of each cable to be detected by an
above-the-ground detector, a cable locate tone transmitter 106
generates and applies a cable locating tone to the sheath
associated with backbone cable 102. This cable locating tone
travels via relays 108 to each of the side-leg cables 104 via a
bond between the sheath associated with backbone cable 102 and
side-leg cables 104. The cable locate transmitter 106 may be, as in
the exemplary embodiment, a LMS3 transmitter available from
Telonix. The LMS3 transmitter generates a plurality of selectable
low frequency tones that may be selected through a DTMF telephone
interface, such as from POTS line 110 or from a cellular telephone
or other interface (not shown). The locate tones may be remotely
selected by frequency and the signal level can be adjusted as
desired.
[0014] The cable tone transmitter 106 is also operably coupled to
an optical switch 112 and an optical transmitter 114 for
transmitting a source of light through an optical fiber 116 to the
optical switch 112. These elements are also adapted for remote
control via the DTMF, cellular or other interface. Optical switch
112 is connected to a fiber distribution panel 118 via a plurality
of fiber jumpers 120.sub.1, 120.sub.2, 120.sub.3 and 120.sub.4. The
fiber distribution panel 118 is coupled to backbone 102 via a
splice enclosure 122 and ground closure 124. Each customer location
has a fiber distribution panel (e.g., 126 associated with the first
customer location) that receives a respective light signal (i.e.,
from fiber jumper 120.sub.1). Fiber distribution panel 126 is
connected via a fiber jumper 128 to an optical switch 130 which is
operable to open or close a ground connection 132 via ground wire
134. Side-leg 104.sub.1 is connected to ground wire 134 via ground
enclosure 136. Fiber distribution panel 126 receives the control
signal from fiber distribution panel 118 via a feeder fiber 138
through splice enclosure 140 as shown. When the multi-position
optical switch 112 is selected to the first position at pole 142,
the optical control signal from source 114 is carried via the
feeder fiber in the backbone 102 to the side-leg 104.sub.1 and
ultimately to fiber distribution panel 126. This control signal
closes optical switch 130 to enable the ground connection 132 at
side-leg 104.sub.1. Switch 130 remains closed until the light
source is removed (by changing the position of switch 112). In this
manner, side-leg 104.sub.1 is selectively grounded as shown and
described in the foregoing, and consequently the entire cable
locating tone current flows through side-leg 104.sub.1 only.
[0015] The other side-legs 104.sub.2, 104.sub.3 and 104.sub.4 may
be similarly grounded by moving optical switch 112 to close
contacts 142.sub.2, 142.sub.3, and 142.sub.4, which will operate to
close a switch coupled to a fiber distribution panel (similar to
panel 126 but not shown) associated with each side-leg 104.sub.2,
104.sub.3 and 104.sub.4. Accordingly, each of side-legs 104.sub.2,
104.sub.3 and 104.sub.4 may be individually grounded to enable the
entire cable locating tone current to flow through a selected
side-leg.
[0016] The ability to remotely control all lateral ground points
eliminates the need for a technician to travel to each customer
location and manually apply or remove the ground. This methodology
therefore reduces plant protection time and increases the
efficiency of maintenance personnel at a dig location.
[0017] The present invention has been shown and described in what
are considered to be the most practical and preferred embodiments.
It is anticipated, however, that departures may be made therefrom
and that obvious modifications will be implemented by those skilled
in the art. It will be appreciated that those skilled in the art
will be able to devise numerous arrangements and variations which,
although not explicitly shown or described herein, embody the
principles of the invention and are within their spirit and
scope.
* * * * *