U.S. patent application number 14/641715 was filed with the patent office on 2015-06-25 for optical line terminal arrangement, apparatus and methods.
The applicant listed for this patent is Coriant Operations, Inc.. Invention is credited to Ornan A. Gerstel, Rajiv Ramaswami.
Application Number | 20150180606 14/641715 |
Document ID | / |
Family ID | 32044847 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150180606 |
Kind Code |
A1 |
Gerstel; Ornan A. ; et
al. |
June 25, 2015 |
OPTICAL LINE TERMINAL ARRANGEMENT, APPARATUS AND METHODS
Abstract
A wavelength division multiplexed optical communication system
includes a plurality of optical line terminals which may be part of
separate in service networks, each having a line interface and an
all-optical pass-through interface including a plurality of
pass-through optical ports, and each also including a plurality of
local optical ports which are connectable to client equipment and
an optical multiplexer/demultiplexer for
multiplexing/demultiplexing optical wavelengths. The optical
multiplexer/demultiplexer may include one or more stages for
inputting/outputting individual wavelengths or bands of a
predetermined number of wavelengths, or a combination of bands and
individual wavelengths. At least one of the pass-through optical
ports of an optical line terminal of one network may be connected
to at least one of the pass-through optical ports of an optical
line terminal of another network to form an optical path from the
line interface of the optical line terminal of the one network to
the line interface of the optical line terminal of the another
network to form a merged network. The use of such optical line
terminals allows the upgrading and merging of the separate networks
while in service.
Inventors: |
Gerstel; Ornan A.; (Los
Altos, CA) ; Ramaswami; Rajiv; (Sunnyvale,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Coriant Operations, Inc. |
Naperville |
IL |
US |
|
|
Family ID: |
32044847 |
Appl. No.: |
14/641715 |
Filed: |
March 9, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12042793 |
Mar 5, 2008 |
9014562 |
|
|
14641715 |
|
|
|
|
10737765 |
Dec 18, 2003 |
7369772 |
|
|
12042793 |
|
|
|
|
09293775 |
Apr 19, 1999 |
6721508 |
|
|
10737765 |
|
|
|
|
60112510 |
Dec 14, 1998 |
|
|
|
Current U.S.
Class: |
398/79 |
Current CPC
Class: |
H04J 14/0216 20130101;
H04J 14/0212 20130101; H04J 14/0206 20130101; H04J 14/0282
20130101; H04J 14/022 20130101; H04J 14/0201 20130101; H04J 14/0286
20130101; H04J 14/0278 20130101 |
International
Class: |
H04J 14/02 20060101
H04J014/02 |
Claims
1. A wavelength division multiplexed optical communication system
comprising: a first optical line terminal having a line interface
and an all-optical pass-through interface; a second optical line
terminal having a line interface and an all-optical pass-through
interface; and connection means for connecting the all-optical
pass-through interface of said first optical line terminal to the
all-optical pass-through interface of said second optical line
terminal to form an optical connection from the line side interface
of said first optical line terminal to the line side interface of
said second optical line terminal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
12/042,793, filed Mar. 5, 2008, which is a continuation of
application Ser. No. 10/737,765, filed Dec. 18, 2003, now U.S. Pat.
No. 7,369,772, issued May 6, 2008, which is a division of
application Ser. No. 09/293,775, filed Apr. 19, 1999, now U.S. Pat.
No. 6,721,508, issued Apr. 13, 2004, which claims the benefit of
U.S. Provisional Application No. 60/112,510, filed Dec. 14, 1998.
Each of those applications is hereby incorporated by reference in
their entireties, as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The invention is in the field of optical telecommunications,
and more particularly, pertains to upgrading an in-service
wavelength division multiplexed (WDM) optical communication system
including a pair of optical line terminals (OLTs) that reside in
the same office and are part of separate WDM networks to form an
all optical pass-through from the line side of one OLT of the pair
to the line side of the other OLT of the pair.
BACKGROUND OF THE INVENTION
[0003] Wavelength division multiplexing (WDM) is an approach for
increasing the capacity of existing fiber optic networks. A WDM
system employs plural optical signal channels, each channel being
assigned a particular channel wavelength. In a WDM system optical
signal channels are generated, multiplexed to form an optical
signal comprised of the individual optical signal channels,
transmitted over a single waveguide, and demultiplexed such that
each channel wavelength is individually routed to a designated
receiver.
SUMMARY OF THE INVENTION
[0004] In typical wavelength division multiplexing systems all
wavelengths are constrained to pass through from a source optical
node to a predetermined sink optical node.
[0005] In view of the above it is an aspect of the invention to
selectively pass-through, add or drop individual wavelengths at
selected optical nodes.
[0006] It is another aspect of the invention to utilize optical
line terminals having all-optical pass-through interfaces that
provide for continued transmission of optical signals without any
intervening electro-optical conversion, and to connect two optical
line terminals back-to-back at their respective pass-through
interfaces to provide an optical path from the line side interface
of the first optical line terminal to the line side interface of
the second optical line terminal.
[0007] It is yet another aspect of the invention to utilize optical
line terminals having a multiplexer/demultiplexer including one or
more stages for inputting/outputting individual wavelengths or
bands of a predetermined number of wavelengths, or a combination of
bands and individual wavelengths.
[0008] It is a further aspect of the invention to utilize the
optical line terminals to support complex mesh network structures
while permitting growth of an in-service network without disrupting
network service.
[0009] It is yet a further aspect of the invention to provide a
wavelength division multiplexed optical communication system
including a plurality of optical line terminals, each having a line
interface and an all-optical pass-through interface including a
plurality of pass-through optical ports and each also including a
plurality of local optical ports and an optical
multiplexer/demultiplexer for multiplexing/demultiplexing
transmitted/received wavelengths. The optical
multiplexer/demultiplexer may include one or more stages for
inputting/outputting individual wavelengths or bands of a
predetermined number of wavelengths, or a combination of bands and
individual wavelengths, with at least one of the pass-through
optical ports of one of the optical line terminals being connected
to at least one of the pass-through optical ports of another
optical line terminal to form an optical path from the line side
interface of the one of the optical line terminals to the line side
interface of the another optical line terminal.
[0010] These and other aspects and advantages of the invention will
be apparent to those of skill in the art from the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a block diagram of an optical line terminal;
[0012] FIG. 2 is a flow chart of the control steps executed by the
controller 10 of FIG. 1;
[0013] FIG. 3 is a block diagram of an optical line terminal having
a two-stage multiplexer/demultiplexer;
[0014] FIG. 4 is a schematic diagram representative of the optical
line terminal of FIG. 1 or FIG. 3;
[0015] FIG. 5 is a schematic diagram of two optical line terminals
such as in FIG. 4 being connected back-to-back;
[0016] FIG. 6 is a diagram illustrating how at least two separate
point-to-point WDM systems can be upgraded while in-service to form
a merged point-to-point WDM system;
[0017] FIG. 7 is a diagram illustrating how at least two separate
network WDM systems can be upgraded while in-service to form a
merged network WDM system; and
[0018] FIG. 8 illustrates a mesh connection between a plurality of
optical line terminals.
DETAILED DESCRIPTION
[0019] FIG. 1 is a block diagram of an optical line terminal (OLT)
2 which is the basic element of the present embodiment. The OLT 2
has an input/output line interface 4 which is connected to an
external fiber facility and transmits/receives an optical signal
having N optical wavelengths, for example 32 wavelengths, on a
single optical fiber which is multiplexed/demultiplexed by a
multiplexer/demultiplexer 6, which outputs demultiplexed
wavelengths .lamda.1-.lamda.N on individual optical fibers. The
respective wavelengths .lamda.1-.lamda.N are sent either to a peer
OLT via a pass-through port or to client equipment via a
transponder and a local port. The client equipment includes SONET
equipment, add/drop multiplexers, cross-connect switches, internet
protocol (IP) routers, asynchronous transfer mode switches (ATM)
and the like.
[0020] As employed herein an optical signal is generally intended
to encompass wavelengths in the range of approximately 300
nanometers to approximately 2000 nanometers (UV to far IR). This
range of wavelengths can be accommodated by the preferred type of
optical conductor (a fiber optic), which typically operates in the
range of approximately 800 nanometers to approximately 1600
nanometers.
[0021] Consider .lamda.1 which is provided to a 1.times.2 switch 8
which is controlled by a control signal, having at least N states,
from a controller 10. The controller 10 responds to a command, from
a management system (not shown), at a terminal 12 to provide the
control signal at a terminal 14 and then to control terminal 16 of
switch 8 to position the switch 8 in a first or second position.
When in the first position, .lamda.1 is provided to a transponder
18 which transmits .lamda.1 to a client apparatus 20 via a local
port 19. When in the second position .lamda.1 is provided to a
pass-through port 22 to a corresponding pass-through port in a peer
OLT 24. The control signal is also provided to output terminal 15,
and then to control terminal 16 of a corresponding switch 8 in peer
OLT 24 to route .lamda.1 to the corresponding
multiplexer/demultiplexer 6. If it is desired to send .lamda.1 to
both client apparatus 20 and peer OLT 24, an optical splitter can
be used in place of the switch 8.
[0022] Switch 26 selects .lamda.1 coming from the opposite
direction in response to a control signal at terminal 28 from
controller 10 to position switch 26 in a first or second position.
When in the first position, 21 is received from client 20 via local
port 19 and transponder 18, and when in the second position 21 is
received from peer OLT 24 via pass-through port 22, and then is
provided to multiplexer/demultiplex 6 to be multiplexed with the
other received wavelengths .lamda.2-.lamda.N.
[0023] A wavelength can be directly passed-through to a peer OLT
rather than being sent to a client apparatus. For example, .lamda.2
is directly sent to, and received from, peer OLT 30 via
pass-through port 32.
[0024] A 1.times.N switch can be used to send/receive a wavelength
to/from one of N-1 peer OLTs or a client apparatus. For example,
1.times.N switch 34 under control of a control signal, having at
least N states, provided to terminal 36 from controller 10 sends
.lamda.3 to either peer OLT 38 via pass-through port 40, or peer
OLT 42 via pass-through port 44, or peer OLT 46 via pass-through
port 48 or client apparatus 50 via transponder 52 and local port
53. Reception of .lamda.3 in the opposite direction is controlled
by N.times.1 switch 54 under control of a control signal provided
to terminal 56 from controller 10, and than is provided to
multiplexer/demultiplexer 6 to be multiplexed with the other
received wavelengths.
[0025] As discussed above, a wavelength can be passed-through to a
peer OLT via a pass-through port or can be optically switched to a
client apparatus via a local port. .lamda.N is shown as being
directly passed through to, or received from, peer OLT 60 via
pass-through port 62.
[0026] FIG. 2 is a flow chart of the steps performed by the
controller 10 of FIG. 1 to control the 1.times.2 switches 8 and 26,
and the 1.times.N switches 34 and 54 to route the respective
wavelengths .lamda.1-.lamda.N.
[0027] In step S101 the controller 10 waits for a command from a
management system such as a computer (not shown). At step S102 a
determination is made as to whether or not the command is a switch
control signal to either pass-through the wavelength via a
pass-through port to a peer OLT or drop/add the wavelength locally
at/from a client apparatus via a transponder and a local port. If
the answer is no, the command is handled by another interface (not
shown) at step S103. If the answer is yes, a signal is sent to
switch A (for example switch 8 or 34) to move switch A to transmit
position X (the selected position) at step S104, and at S105 a
signal is sent to switch B (for example switch 26 or 54) to move
switch B to receive position X (the selected position). At step 106
the control signal at terminal 15 of controller 10 is sent to the
peer OLT to set its switches A and B in a corresponding manner. A
loop-back is then made to step S101 to wait for the next
command.
[0028] In the multiplexer/demultiplexer 6 of FIG. 1, 32 wavelengths
on a single optical fiber received at line interface 4 are
demultiplexed into 32 individual wavelengths .lamda.1-.lamda.32.
However, according to another aspect of the invention the 32
wavelengths can be demultiplexed into bands, for example four bands
of 8 wavelengths each, by a first multiplexer, and the resultant
four bands can be processed by the OLT. According to another aspect
of the invention at least one of the four bands of wavelengths can
be demultiplexed by a second multiplexer/demultiplexer into its
individual wave lengths such that the OLT can process the
individual wavelengths of the at least one band and the remaining
ones of the four bands.
[0029] FIG. 3 is a block diagram illustrating a modular OLT 200
having two stages of multiplexing/demultiplexing. The operation of
the OLT 200 is described with respect to the demultiplexing
operation; however, it is to be understood that the multiplexing is
merely the reverse operation. It is to be noted that the 1.times.2
switches and 1.times.N switches shown in FIG. 1 are not included in
FIG. 3 in order to simplify the drawing. However, it is to be
understood that in practice such switches may be utilized in the
practice of the invention. The OLT terminal 200 has an input/output
line interface 202 which is connected to an external fiber facility
and receives on a single optical fiber N, for example 32,
wavelengths which are demultiplexed by a multiplexer/demultiplexer
204, which is situated on a first modular card, into M, for example
4, bands of 8 wavelengths each. The first band 206
(.lamda.1-.lamda.8) is demultiplexed into its 8 individual
wavelengths by a multiplexer/demultiplexer 208, which is situated
on a second modular card, with each such wavelength being provided
to a pass-through port (P) or a local port (L) via transponder (T).
Each of the pass-through ports (P) is situated on a different
modular card, and each of the transponder (T) and its associated
local port (P) are situated together on yet another modular card.
Although direct connections are shown, as discussed above the
respective wavelengths may be selectively switched to either of a
local port (L) via transponder (T), or a pass-through port (P) as
described with respect to FIG. 1.
[0030] The second band 210 (.lamda.9-.lamda.16) is provided
directly to a pass-through port (P), and the third band 212
(.lamda.17-.lamda.24) is provided directly to a pass-through port
(P).
[0031] The fourth band 214 (.lamda.25-.lamda.32) is demultiplexed
into its 8 individual wavelengths by a multiplexer/demultiplexer
216, which is situated on a modular card 217, with each such
wavelength being provided to a pass-through port (P) or a local
port (L) via a transponder (T). Again, switching may be used to
select a connection to either P or T.
[0032] FIG. 4 is a simplified schematic diagram representative of
the OLT 2 shown in FIG. 1 or the OLT 200 of FIG. 3. However, it is
to be noted that for simplicity only 16 wavelengths are utilized.
The OLT 300 interfaces and operates in a bidirectional manner as
discussed in detail with respect to FIGS. 1 and 3. The line
interface 302 is adapted for wavelength division multiplexed (WDM)
optical communication signals of the highest relative order, in
this example 16 wavelengths .lamda.1-.lamda.16, corresponding to
the N optical wavelengths on a single optical fiber which are
applied to input/output line interfaces 4 and 202 of OLT 2 (FIG. 1)
and OLT 200 (FIG. 3), respectively. The pass-through interface
connected to the lines WL 1-4, WL 5-8, WL 9-12 and WL 13-16
corresponds to the respective pass-through ports, and the
local-interface connected to the lines labeled 16 local ports
correspond to the local ports connected to the respective
transponders, where wavelengths from or to client equipment are
added or dropped.
[0033] FIG. 5 illustrates two OLTs 300A and 300B as shown in FIG. 4
connected in a back-to-back relationship by way of their respective
all-optical pass-through interfaces. Thus, it is seen that the
connection results in an optical add/drop multiplexer (OADM)
functionality without requiring intermediate electro-optical
conversion (OEO) of the communicated optical signals. As discussed
above, the add/drop feature is achieved at the 16 local ports of
each OLT, where channels (wavelengths) can be added or dropped by a
manual configuration, or via add/drop switching, as controlled by
switches 8 and 26 of FIG. 1, to achieve a switchable add/drop
multiplexer.
[0034] The pass-through may be accomplished using single conductors
and/or ribbon connectors that pass multiple individual channels
(wavelengths) in one cable. The pass-through connections between
OLTS 300A and 300B is preferably made using ribbon
connectors/cables.
[0035] FIG. 6 illustrates three separate in-service WDM
point-to-point optical communication systems A, B and C which are
not initially interconnected. WDM system A includes optical nodes
400 and 402 which are optically connected via their respective line
interfaces, with at least optical node 402 being an OLT. WDM system
B includes optical nodes 404 and 406 which are optically connected
via their respective line interfaces, with at least optical node
404 being an OLT. WDM system C includes optical nodes 408 and 410
which are optically connected via their respective line interfaces,
with at least optical node 408 being an OLT.
[0036] As discussed above, the three separate WDM systems are not
initially interconnected. However, any two of the three WDM
systems, or all three of the WDM systems, may be interconnected by
connecting respective OLTs of the separate WDM system back-to-back
at respective pass-through ports as shown in FIG. 5, without
disrupting service. For example, WDM system A may be connected to
WDM system B by directly optically connecting pass-through ports of
the OLT of node 402 to pass-through ports of the OLT of node 404
via optical fibers 416 and 418. WDM system A may also be connected
to WDM system C by directly optically connecting pass-through
optical ports of the OLT of node 402 to pass-through ports of the
OLT of node 408 via optical fibers 420 and 422. Thus, an all
optical path is provided from optical node 400 of WDM system A to
optical node 406 of WDM system B, and likewise an all optical path
is provided from optical node 400 of WDM system A to optical node
410 of WDM system C, resulting in a merger of WDM systems A, B and
C without disrupting service. At the back-side of the respective
optical nodes, lines with a box are indicative of local ports (L)
to which client equipment is normally connected.
[0037] FIG. 7 illustrates three separate in-service WDM network
optical communication systems D, E and F which are not initially
interconnected. WDM system D includes optical nodes 500 and 502
which are optically connected via their respective line interfaces
through an optical network 503, with at least optical node 502
being an OLT. WDM system E includes optical nodes 504 and 506 which
are optically connected via their respective line interfaces
through an optical network 507, with at least optical node 504
being an OLT. WDM system F includes optical nodes 508 and 510 which
are optically connected via their respective line interfaces
through an optical network 511, with at least optical node 508
being an OLT.
[0038] As discussed above, the three separate WDM optical networks
are not initially interconnected. However, any two of the three WDM
optical networks, or all three of the WDM optical networks may be
interconnected by connecting respective OLTs of the separate WDM
optical networks back-to-back at respective pass-through ports as
shown in FIG. 5, without disrupting service. For example, WDM
optical network D may be connected to WDM optical network E by
directly optically connecting pass-through ports of the OLT of node
502 to pass-through ports of the OLT of node 504 via optical fibers
516 and 518. WDM system D may also be connected to WDM optical
network F by directly optically connecting pass-through optical
ports of the OLT of node 502 to pass-through ports of the OLT of
node 508 via optical fibers 520 and 522. Thus, an all optical path
is provided from optical node 500 of WDM optical network D to
optical node 506 of WDM optical network E, and likewise an all
optical path is provided from optical node 500 of WDM optical
network D to optical node 510 of WDM optical network F, resulting
in a merger of WDM network optical communication systems D, E and F
without disrupting service. At the back-side of the respective
optical nodes, lines with a box are indicative of local ports (L)
to which client equipment is normally connected.
[0039] FIG. 8 illustrates how OLTs can be connected in more complex
ways to achieve greater functionality, such as, for example,
limited cross-connection capabilities. Specifically, OLT 600 and
OLT 602 are connected back-to-back to form a first OADM, OLT 604
and OLT 606 are connected back-to-back to form a second OADM, OLT
600 and OLT 606 are connected back-to-back to form a third OADM and
OLT 602 and OLT 604 are connected back-to-back to form a fourth
OADM. OLT 600, OLT 602 and OLT 604 each have add/drop switching
capability, whereas OLT 606 has no switching capability.
[0040] The arrangement shown in FIG. 8 illustrates how a group of
OLTs in an office, which may be part of separate WDM networks, can
be coupled to form different OADMs on an individual channel or per
band basis. Wavelengths 1, 2, 3 and 4 (channels 1, 2, 3 and 4) are
connected between pass-through optical ports of OLT 600 and OLT 602
via optical fiber 603 and are also connected between pass-through
optical ports of OLT 604 and OLT 606 via optical fiber 607.
Wavelengths 5, 6, 7 and 8 (channels 5, 6, 7 and 8) are connected
between pass-through optical ports of OLT 600 and OLT 606 via
optical fiber 608 and are also connected between pass-through
optical ports of OLT 602 and OLT 604 via optical fiber 609.
Wavelengths 9, 10, 11 and 12 (channels 9, 10, 11 and 12) can be
separated into individual channels that are connected between local
ports of the respective OLTs. For example, channel 9 is directly
connected between a local port of OLT 600 and a local port of OLT
602 via optical fiber 610, and channel 10 is directly connected
between a local port of OLT 600 and a local port of OLT 606 via
optical fiber 612. To simplify the drawing, no connections are
shown for wavelengths 11 and 12; however, they may be connected in
a like manner. The local ports may also be connected to client
equipment as discussed above. It is to be noted that the connection
configuration of FIG. 8 does not constitute a plain patch-panel
form of connectivity, insofar as it allows for switching of
channels without manual reconfigurations.
[0041] In summary, the methods and apparatus of the present
invention allow upgrading of a wavelength division multiplexed
optical communication system including a pair of OLTs that reside
in the same office or facility and are part of separate WDM
networks (whether point-to-point links or more advanced networks)
to form an OADM. Such upgrade is accomplished without service
disruption to the network by appropriate connection of the OLTs
through the pass-through interfaces.
[0042] Although certain embodiments of the invention have been
described and illustrated herein, it will be readily apparent to
those of ordinary skill in the art that a number of modifications
and substitutions can be made to the preferred example methods and
apparatus disclosed and described herein without departing from the
true spirit and scope of the invention.
* * * * *