Concentrated dynamic test path rooting

Details Concentrated dynamic test path rooting Concentrated dynamic test path rooting

1997-12-24

2001-08-28

Nguyen, Duc (Department: 2643)

Telephonic communications

Diagnostic testing, malfunction indication, or electrical...

Testing of subscriber loop or terminal

C379S016000, C379S017000, C379S029010

Reexamination Certificate

active

06282266

ABSTRACT:

FIELD OF THE INVENTION
The invention generally relates to telecommunication service and specifically, the invention relates to testing, performed at a central office, of “drops” at a remote terminal for individual subscriber service.
BACKGROUND
Years ago, telecommunications companies provided service to their subscribers strictly by copper wire. Within the recent decades, however, telecommunications companies have been gradually replacing much of the copper wire with optical fiber. Optical fiber permits a greater capacity of signals to travel further with considerably less degradation than when using copper wires.
The block diagram of
FIG. 1
shows generally a communication system that does not include fiber. A central office (CO)
110
provides, through local digital switch (LDS)
112
, subscriber service on communication path
114
to a remote terminal (RT)
118
. A number N of RTs
118
n
(n=1 . . . N) can be coupled to the switch
112
via a respective communication path
114
n
. Each communication path
114
n
includes T
1
lines, i.e., lines capable of carrying signals according to the DS1 signaling standard for transmission at 1.544 Mbps. A T
1
facility can support 24 simultaneous DS0 channels, where DS0 is a standard for transmission (64 Kbps) for PCM digitized voice channels and is well known in the art.
The RTs each respectively contain a number of different cards including “plain old telephone service” (“POTS”) cards
122
, which are each in turn coupled to a respective subscriber's home or office to provide telephone or other communication service. The connection
124
between a respective POTS card
122
and the subscribers location is often referred to herein as a “drop.” Each drop is composed of a “tip” line and “ring” line. POTS cards can often support more than one drop.
Often, the telecommunication service provider (e.g., a telephone company) will need to test an individual “drop” from the RT
118
n
to the individual subscriber's location. Rather than having to go to each subscriber's location, equipment is provided at the CO to enable remote testing of drops, including a “mechanized loop test” (MLT) unit
130
. The MLT
130
has a number of DC test pairs
132
, formed of copper, coupled between the MLT
130
and switch
112
. While two test pairs
132
are shown in
FIG. 1
, one or more test pairs are often provided. In addition, dedicated test lines, referred to herein as “bypass pairs” and also formed of copper, are coupled between the CO
110
and the RTs such that each RT
118
n
receives its own respective bypass pair
134
n
. The switch
112
switches to couple a DC test pair to a bypass pair such that only a single RT unit is coupled to the respective DC test pair at a given time.
Tests are performed under control of the MLT
130
. Generally, to initiate a test, first switch
112
directs that 130 volts be placed on the tip line of the individual drop to be tested via its respective POTS card. This 130 volts informs the selected POTS card in the RT that its drop is about to be tested. The POTS card then redirects its connection from the communication path
114
n
to the bypass pair coupled to the RT. Then the MLT
130
, having been electrically coupled to the drop to be tested via the appropriate bypass pair
134
n
and switch
112
, takes appropriate electrical measurements over the drop under test (e.g., by placing a voltage or current on the bypass pair
134
n
).
The telecommunications industry has gradually been replacing many of their copper wire connections with optical fiber, and particularly those connections between the CO and the RTs. Referring to the block diagram of
FIG. 2
, central office
210
is coupled to each of N RT units
218
n
, n=1 . . . N, via a communication path
216
n
formed of optical fiber. (In one implementation currently provided by DSC Communications Corporation, N≦5). The communication path
216
n
carries signals according to the SONET standard of optical network transmission as is known in the art. In the CO
210
, a local digital switch
212
and MLT
230
are still present and coupled to one another, the MLT
230
providing DC test pairs
232
to the LDS
212
. However, rather than being directly connected to each RT via copper lines, the switch
212
is coupled with copper T
1
lines
214
, that are capable of carrying signals in accordance with DS1 or DS0, to a central office terminal (COT)
240
. The COT is then coupled to each RT via fiber communication paths
216
n.
The COT
240
also receives one or more bypass pairs
234
, formed of copper wire, from LDS
212
.
Despite the use of fiber paths
216
n
, MLT
230
as used by most telecommunication service providers is the same MLT used when a copper wire connection was formed between the central office and each RT unit. Since the MLT
230
cannot take measurements over fiber (it can only take electrical measurements), testing the individual drops becomes difficult when fiber is installed. Thus, equipment has been developed to mimic copper signals over the fiber path, enabling switch
212
to essentially “perceive” a copper bypass pair from the central office to each RT and to allow the POTS cards at each RT to essentially “perceive” the switch
212
as if coupled with copper wire. This equipment includes COT
240
, mentioned above.
The COT
240
includes a common control unit
242
as well as one or more card banks
244
m
, m =1 . . . M. In one implementation currently provided by DSC Communications Corporation, M≦9. Common control unit
242
provides hardware, firmware, and/or software needed to interface the copper lines
214
and bypass pairs
234
from the LDS
212
to optical fiber paths
216
n
. Each card bank within the COT
240
can also be one of a variety of types, e.g., a channel bank, a fiber bank, or the like. In
FIG. 2
, each of the card banks
244
m
in the COT is shown as a channel bank. Card banks
244
m
, each include slots for housing various line cards. In one implementation, each channel bank includes
56
line card slots. In the case of a channel bank, e.g.,
244
M
, line cards may include POTS cards
246
coupled to a drop
248
.
Each RT unit
218
n
also includes a common control unit
260
, which is similar in many respects to common control unit
242
in COT
240
. Each RT
218
n
also includes a plurality of card banks
262
1k
,
262
Np
(k=1 . . . K, p=1 . . . P), where the subscript for each card bank
262
identifies first the RT number and then the bank number (
262
(RT#)(bank#)
). The number (K, P) of card banks
262
1k
,
262
Np
in each RT
218
n
can vary, although in one implementation, K, P≦9. Each card bank within each RT can also be one of a variety of types: the card banks can be either channel banks, fiber banks, or the like. For example, in
FIG. 2
, RT-
1
218
1
is shown to contain one card bank
262
11
, which is a channel bank. Channel bank
262
11
includes a number of line cards, including POTS cards
247
which are each coupled to a drop
224
. RT-N
218
N
, however, includes P card banks
262
Np
, where at least one of the banks
262
Np
is a channel bank, housing POTS cards
247
, and at least one of the banks is a fiber bank
262
N1
.
A fiber bank, e.g.,
262
N1
, includes a number of fiber cards (not shown), which convert electrical signals to optical signals and vice versa. Each card in the fiber bank
262
N1
is coupled to an optical network unit (ONU)
270
q
, q=1. Q, via a fiber connection. As they receive optical signals, ONUs
270
q
are generally used to provide telecommunication services to subscribers that are located too far away from the RT to receive reliable service over copper lines. Each ONU
270
q
includes a fiber card (for converting optical signals into electrical signals and vice versa, not shown) and a number of POTS cards
247
each coupled to a respective drop
224
. Each fiber bank, e.g.,
262
N1
can have a plurality of ONUs coupled to it, and in one implementation
16
ONUs can be coupled to a fiber bank su

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