U.S. patent application number 11/211699 was filed with the patent office on 2005-12-22 for fiber optic synchronous digital hierarchy telecommunication network provided with a protection system shared on the network.
This patent application is currently assigned to ALCATEL. Invention is credited to Coltro, Claudio.
Application Number | 20050281250 11/211699 |
Document ID | / |
Family ID | 11377147 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050281250 |
Kind Code |
A1 |
Coltro, Claudio |
December 22, 2005 |
Fiber optic synchronous digital hierarchy telecommunication network
provided with a protection system shared on the network
Abstract
A fiber optic synchronous digital hierarchy telecommunication
network provided with a protection system shared on the network is
described, which comprises spans of pairs of optical fibers
(N.times.2F) having network elements (N.times.2F-SDHNE) interposed
therebetween, wherein the spares of pairs of optical fibers have a
variable number N (N=1, 2, 3, . . . ) of pairs, and the network
elements (N.times.2F-SDHNE) feature variable interconnection
capability between said spans, so that several spans having number
N of pairs of optical fiber even different can be connected to at
least some of said network elements.
Inventors: |
Coltro, Claudio; (Milano,
IT) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
ALCATEL
|
Family ID: |
11377147 |
Appl. No.: |
11/211699 |
Filed: |
August 26, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11211699 |
Aug 26, 2005 |
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10180344 |
Jun 27, 2002 |
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6950392 |
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10180344 |
Jun 27, 2002 |
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09074812 |
May 8, 1998 |
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6421318 |
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Current U.S.
Class: |
370/351 |
Current CPC
Class: |
H04J 14/0291 20130101;
H04J 3/085 20130101; H04J 2203/0042 20130101; H04J 2203/006
20130101; H04Q 11/0478 20130101; H04J 14/0283 20130101 |
Class at
Publication: |
370/351 |
International
Class: |
H04L 012/28 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 1997 |
IT |
MI97A 001144 |
Claims
What is claimed is:
1. A fiber optic network, including network elements comprising
optical interfaces for receiving optical fibers, and fiber optic
spans interposed between the network elements to form a ring, each
network element being connected to adjacent network elements
through said fiber optic spans allowing communication therebetween;
wherein said fiber optic spans comprise: at least two spans having
a first number of fibers; and at least one span having a second
number of fibers, the second number being different from the first
number; further wherein said network elements comprise: at least
one network element interposed between spans having said first
number of fibers; and at least one network element connected to a
span having said second number of fibers.
2. A network according to claim 1, wherein every network element
realizes the following types of non-blocking connections:
cross-connection between fibers of the same span; cross-connection
between fibers of different spans, from any span towards any other
span; connections between said fibers and local ports for local
data flows at a bit rate lower than the bit rate between the
network elements.
3. An optical ring network, comprising: a plurality of network
elements; and plural fiber optic spans interposed between the
network elements to form said ring, each network element being
connected to adjacent network elements through said fiber optic
spans allowing communication therebetween, wherein a non-blocking
cross-connection is realized between fibers of a same span.
4. An optical ring network, comprising: a plurality of network
elements; and plural fiber optic spans interposed between the
network elements to form said ring, each network element being
connected to adjacent network elements through said fiber optic
spans allowing communication therebetween, wherein a non-blocking
cross-connection is realized between fibers of different spans from
any span towards any other span.
5. An optical ring network, comprising: a plurality of network
elements; and plural fiber optic spans, each of a plurality of
fibers, interposed between the network elements to form said ring,
each network element being connected to adjacent network elements
through said fiber optic spans allowing communication at a same bit
rate therebetween, wherein non-blocking connections are makeable
between said fibers and local ports for local data flows at a bit
rate lower than said same bit rate between said network
elements.
6. A network according to claim 1, wherein said fiber optic spans
further comprise at least one span having a third number of fibers,
the third number being higher than the second number.
7. A network according to claim 1, further wherein said at least
one network element that is connected to a span having said second
number of fibers is also connected to at least one span having said
first number of fibers.
8. A network according to claim 1, further wherein said at least
one network element that is connected to a span having said second
number of fibers is also connected to a further span having said
second number of fibers.
9. A network according to claim 6, further wherein said network
elements comprise at least one network element connected to a span
having said third number of fibers and to at least one span having
said first number of fibers.
10. A network according to claim 6, further wherein said network
elements comprise at least one network element connected to a span
having said third number of fibers and to at least one span having
said second number of fibers.
11. A network according to claim 6, further wherein said network
elements comprise at least one network element connected to a span
having said third number of fibers and to a span having said third
number of fibers.
12. A network according to claim 1, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a cross-connection capability between
fibers of the same span.
13. A network according to claim 1, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a cross-connection capability between
fibers of different spans.
14. A network according to claim 3, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a connection capability between said
fibers and local ports for local data flows at a bit rate lower
than the bit rate between the network elements.
15. A network element for use in a fiber optic network including
network elements and fiber optic spans interconnecting the network
elements to form a ring, said fiber optic spans including at least
two spans having a first number of fibers; and at least one span
having a second number of fibers, with the second number being
higher than the first number; said network element realizing the
following types of non-blocking connections: cross-connection
between fibers of the same span; cross-connection between fibers of
different spans, from any span towards any other span; connections
between said fibers and local ports for local data flows at a bit
rate lower than the bit rate between the network elements.
16. A method for making a fiber optic network, the method
comprising the step of interposing fiber optic spans between
network elements to form a ring, wherein said network elements
comprise optical interfaces for receiving optical fibers and
wherein each network element is connected to adjacent network
elements through said fiber optic spans allowing communication
therebetween, wherein: at least two of said spans have a first
number of fibers, and at least one of said spans has a second
number of fibers, the second number being different from the first
number; and said step of providing network elements comprises
providing at least one network element interposed between spans
having said first number of fibers, and providing at least one
network element connected to a span having said second number of
fibers.
17. A method according to claim 16, wherein the step of providing
network elements comprises providing network elements realizing the
following types of non-blocking connections: cross-connection
between fibers of the same span; cross-connection between fibers of
different spans, from any span towards any other span; and
connections between said fibers and local ports for local data
flows at a bit rate lower than the bit rate between the network
elements.
18. A method according to claim 16, wherein said fiber optic spans
further comprise at least one span having a third number of fibers,
the third number being higher than the second number.
19. A method according to claim 16, further comprising connecting
said at least one network element that is connected to a span
having said second number of fibers also to at least one span
having said first number of fibers.
20. A method according to claim 16, further comprising connecting
said at least one network element that is connected to a span
having said second number of fibers also to a further span having
said second number of fibers.
21. A method according to claim 18, wherein said interposing step
further comprises connecting at least one network element connected
to a span having said third number of fibers also to at least one
span having said first number of fibers.
22. A method according to claim 18, wherein said interposing step
further comprises connecting at least one network element connected
to a span having said third number of fibers also to at least one
span having said second number of fibers.
23. A method according to claim 18, wherein said interposing step
further comprises connecting at least one network element connected
to a span having said third number of fibers also to a span having
said third number of fibers.
24. A method according to claim 16, wherein said first number of
fibers is two and said second number of fibers is four.
25. A method according to claim 16, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a cross-connection capability between
fibers of the same span.
26. A method according to claim 16, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a cross-connection capability between
fibers of different spans.
27. A method according to claim 1, wherein said at least one
network element that is connected to a span having said second
number of fibers provides for a connection capability between said
fibers and local ports for local data flows at a bit rate lower
than the bit rate between the network elements.
28. A method according to claim 16, wherein said second number is
higher than said first number.
Description
[0001] This is a continuation of Application Ser. No. 10/180,344,
filed Jun. 27, 2002, which is a continuation of application Ser.
No. 09/074,812, filed May 8, 1998, now U.S. Pat. No. 6,421,318, the
disclosures of which are incorporated herein by reference.
BACKGROUND OF INVENTION
[0002] The present invention relates to the field of the
synchronous hierarchy telecommunication network and more precisely
to improvements in a fiber optic SDH telecommunication network
provided with a protection system shared on the network, comprising
fiber optic spans with network elements interposed therebetween in
which every network element is connected to an adjacent elements
through said fiber spans allowing a bidirectional communication
between the elements.
[0003] The structure of the fiber optic SDH (Synchronous Digital
Hierarchy) telecommunication networks, as well as the transmission
protocols, are substantially known and subjected to international
standardization activity.
[0004] The International Telecommunication Union (ITU-T) issued a
set of Recommendations (series G.7nn and G.8nn, in particular
G.707, G.782, G.783, G.803, G.841) relative to said SDH network
structure giving a full description thereof, to such a level that a
person skilled in the art is able to get all information required
for the implementation thereof, as a not limiting example, the
ITU-T Recommendation G.707 entitled "General Aspects of Digital
Transmission Systems-Network node Interface for the Synchronous
Digital Hierarchy (SDH)", November 1995.
[0005] In the field of fiber optic SDH transmission networks,
systems for protecting from line interruptions of the type shared
on the network itself are generally known with the acronym
MS-SPRING (Multiplex Section-Shared Protected RING), described e.g.
in the ITU-T Recommendation G.841 entitled: "General Aspects of
Digital Transmission Systems-Types and characteristics of SDH
Network Protection Architectures", April 1995. In said
Recommendation G.841 there are described the MS-SPRING networks
having two-fiber spans (2F-MS-SPRING) or four-fiber ones
(4F-MS-SPRING).
[0006] As evidenced in FIGS. 1.1 and 1.2, the known two- and
four-fiber architectures are composed of two-fiber (2F) spans or
four-fiber (4F) spans respectively, having nodal points, 2F-SDHNE
or 4F-SDHNE respectively, interposed therebetween and formed
essentially of known multiplexing/switching matrices, as described
in Recommendation G.841.
[0007] Due to the type of traffic in said transmission network that
is generally hubbed or dual hubbed with a small component of
uniform traffic, fixed ring structures like 2F-MS-SPRING and
4F-MS-SPRING are not flexible enough to adapt the traffic
requirements in the network.
[0008] From the traffic distribution analysis in the metropolitan
regional and national network, it has been observed that said
networks are mainly made of few nodes with high traffic
capabilities (for large capital cities or large suburbs and
business centers) and, on the other hand, a majority of nodes with
small traffic access capabilities, located in the city or small
suburbs.
[0009] It has been observed that traffic models in real networks
require a multiplicity of nodes with limited traffic access
capabilities and, on the contrary, a very small number of nodes
require very high traffic access capabilities; this amounts to
saying that the mean flows of traffic go from small nodes to large
nodes.
[0010] If one wishes to realize such networks by using the known
structures 2F-MS-SPRINGs or 4F-MS-SPRINGs, it is seen that, apart
from the traffic access in each of the nodes, the amount of high
speed interconnecting ports required to interconnect the nodes is
the same and it is too high. This results in large expenditures in
installation and equipment costs.
[0011] Moreover, in the case of multiple interruptions in the fiber
optic spans or optical interfaces, the known network structures do
not provide enough protection level, since they do not assure a
suitable reset capability.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the present invention to
overcome all the aforesaid drawbacks and to indicate a new topology
of fiber optic SDH telecommunication networks provided with a
protection system shared on the network, in which nodes with very
high traffic access capabilities and nodes with smaller traffic
access capabilities coexist.
[0013] Large nodes will require a higher number of optical ports
and interconnection fibers, whilst smaller nodes will require a
smaller amount of optical ports and fiber interconnections.
[0014] Hence, network elements and nodes with capability
N.times.2FMS SPRINGs will coexist in the same network, N being
variable. Typically N will be 1 or 2 but greater values may exist
as well. Therefore, in the same network, network elements with
2-fiber connections for small nodes, network elements with
2.times.2-fiber connections for medium sized nodes and network
elements with N.times.2-fiber connections for larger nodes, will
coexist.
[0015] N.times.2F nodes (N=>2) will be required to support a
full cross-connection of traffic between high-speed optical ports
and between high-speed ports and low-speed ports.
[0016] In order to achieve these objectives, the present invention
has for its subject matter improvements in a fiber-optic SDH
telecommunication network provided with a protection system shared
on the network, comprising fiber optic spans with network elements
interposed therebetween, in which every network element is
connected with adjacent elements through said fiber spans allowing
a bidirectional communication between the elements, characterized
in that said fiber optic spans are spans of pairs of fibers having
a variable number N (N=1, 2, 3, . . . ) of pairs, wherein each pair
is independent from the others, and in that said network elements
are network elements with variable interconnection capability
between said spans of pairs of fibers so that connectable to at
least some of said elements are several spans having even different
numbers N of pairs of optical fibers.
[0017] Further embodiments of the present invention are set fourth
in the dependent claims.
[0018] The network of the invention has the basic advantage of a
remarkable cost reduction as compared with the known solutions type
4F-MS-SPRING. This is due to substantial reduction in high-speed
SDH optical interfaces required for interconnecting the nodes. This
results in significant saving in installation, equipment and spare
parts expenditures.
[0019] Another important advantage of the network subject matter of
the present invention is the provision of protection in the case of
multiple interruptions occuring in different spans of the network,
since the N.times.2F nodes act as N independent protection systems,
capable of assuring protection against N simultaneous
interruptions, which are handled independently, thus assuring
higher traffic capabilities in case of failure.
[0020] Another advantage is an increase in the network flexibility
in function of envisaged variations of the traffic demand, since
the grow steps of the N.times.2F-MS-SPRING network are in terms of
two-fiber sub-networks and not of four-fiber sub-networks as in the
known 4F-MS-SPRING networks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Further objects and advantages of the present invention will
result better from the following detailed description of an
embodiment thereof and from the drawings attached merely by way of
a not limiting example, in which:
[0022] FIGS. 1.1 and 1.2 show known two- and four-fiber network
structures respectively;
[0023] FIGS. 2.1 and 2.2 show block diagrams of the 2F-SDHNE and
4F-SDHNE network elements of FIGS. 1.1 and 1.2 respectively;
[0024] FIG. 3 shows the new network structure according to the
invention;
[0025] FIG. 4 shows a first embodiment of the N.times.2F-SDHNE
network element of FIG. 3; and
[0026] FIG. 5 shows a second embodiment of the N.times.2F-SDHNE
network element of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0027] FIGS. 1.1 and 1.2 illustrate conventional two- and
four-fiber network structures respectively. They comprise two-fiber
optic spans 2F (FIG. 1.1) and four-fiber optic spans 4F (FIG. 1.2)
with nodal points interposed therebetween, in the following termed
as 2F-SDHNE and 4F-SDHNE network elements respectively, whose
structure is standardized and described for instance in the ITU-T
Recommendations G.707 and G.841.
[0028] Said network structures form closed rings in which every
network element is connected to two adjacent elements through fiber
optic spans allowing a bidirectional communication (duplex) between
the elements. The ring provides such a redundancy level, both in
bandwidth and in forming parts, that it can be re-configured, in
case of failure, in such a way as to support anyway a certain
traffic level also in a degraded configuration.
[0029] FIGS. 2.1 and 2.2 illustrate block diagrams of the network
elements 2F-SDHNE and 4F-SDHNE of FIGS. 1.1 and 1.2 respectively.
They are formed essentially of known multiplexing/switching
matrices realizing full cross-connection capabilities between the
various input/output ports of the SDH network element, not shown in
the figures. The bidirectional arrows inside the network elements
indicate the types of cross-connection thus realized: connection
between high speed ports for data flows belonging to the same 2F or
4F fiber span, and connections between said high speed ports and
local ports TRIB1 and TRIB2 for data traffic at lower bitrate.
[0030] Data flows can transit through the 2F, 4F fiber optic spans
at high bit rate, e.g. 2.5 Gbit/s or even 10 Gbit/s, and over the
local ports TRIB1 and TRIB2 local flows can transit at variable bit
rate, e.g. from 2 Mbit/s up to 2.5 Gbit/s. The data flow structure
is known and defined in the various ITU-T Recommendations.
[0031] The MS-SPRING network structure, both in the 2F and 4F
cases, sees every span as unitary and carries both working channels
that must be protected, and protection channels of the working
traffic. The protection channels are mainly used for replacing the
working channels in case of failure in the network, otherwise they
are used also for transporting working traffic as extra-capability
under normal condition. The extra-capability is nullified in case
of failure that requires the use of protection channels for
replacing the working channels.
[0032] Following the minimum distance paths between two terminal
points, in the 2F case, one fiber of the span carries working
channels and protection channels in one direction, the other fiber
in the opposite direction, whilst in the 4F case, two fibers in a
span carry working channels one in one direction, the other in the
opposite direction, and the other two carry protection channels,
one in one direction and the other in the opposite direction.
[0033] In both 2F and 4F configurations in case of failure leading
to the break of a fiber in a span, the working traffic of even only
one of the two directions can be routed again over the protection
channel of the other fiber in the opposite direction of the same
span following the longest path on the remainder of the ring, but
avoiding the loss of connection. In the case of break of all fibers
in the span, the working traffic is routed again over the
protection channels of the adjacent span in the opposite
direction.
[0034] It is not deemed necessary to provide further description of
said structures, as well as of signals transiting therein, since
they are known to those skilled in the art.
[0035] In accordance with the present invention, the structures of
FIGS. 1.1 and 1.2 are modified as evidenced by FIG. 3, where the
network structure allows the coexistence of network elements and
nodes with capability of N.times.2F MS-SPRINGs, N being
variable.
[0036] In FIG. 3, 2F indicates spans of pairs of fibers as those
shown in FIG. 1.1 and 2F-SDHNE indicates network elements of the
type shown in FIG. 1.1.
[0037] N.times.2F-SDHNE indicates network elements modified in
accordance with the present invention, to allow said coexistence.
N.times.2F indicates a span with N pairs of fibers, where N=2, 3, .
. . .
[0038] In the general case, every span is then considered as
comprising N independent pairs of fibers, and therefore it is seen
as N different spans contrasting with the known structures.
[0039] As a particular case, for N=1 we obtain the known 2F
case.
[0040] FIG. 4 shows a first not limiting example of how the
structures of FIGS. 2.1 and 2.2 can be modified in accordance with
the present invention to obtain N.times.2F-SDHNE network elements,
i.e. 2.times.2F-SDHNE when N=2.
[0041] A 2.times.2F-SDHNE network element is formed essentially of
a known multiplexing/switching matrix type ADM (Add-Drop Multiplex)
which realizes a non-blocking cross-connect capability between the
various access ports of the network element, not shown in the
figure for simplicity, as they are also known.
[0042] The bidirectional arrows inside 2.times.2F-SDHNE indicate
the following types of non-blocking cross-connections thus
realized:
[0043] cross-connection between ports for high bit rate data flows
belonging to fiber of the same pair (2F11 . . . 2F22) or different
pairs of the same span (2F11 with 2F21, 2F12 with 2F22);
[0044] cross-connection between ports for high bit rate data flows
belonging to pairs of different fiber of different spans: 2F11 with
2F12 or with 2F22; 2F22 with 2F11 or with 2F21, and so on;
[0045] connections between said high speed ports 2Fnn with local
ports TRIB3 for lower bit rate data traffic.
[0046] From the above functional description a person skilled in
the art is able to realize the network element, also taking into
account what described with reference to the above known
structures. The dimensioning of the network element depends upon
the size of the flows to be routed, in accordance with information
frame structures defined e.g. in the ITU-T Recommendation
G.707.
[0047] The cross-connect functionality thus realized is, therefore,
such as to connect in a bidirectional non-blocking way the ports of
2F line spans with the local flow ports TRIB3, and the ports of the
line spans to each other according to all the possible
combinations.
[0048] In case of failure in the span, for instance 2F11, the
network element is able to switch the data flows on span 2F21 or
2F22, this realizing a sort of re-routing of flows from different
spans which was not possible to realize with the known systems
described above.
[0049] Therefore, it is possible to configure a four-fiber high
speed span preferably as composed of two known independent spans of
pairs of fibers 2F, thanks to the new configuration according to
the invention which allows a cross-connection between ports for
high bit-rate data flows belonging to different fiber spans. This
was not possible in the known systems. But it is always possible to
configure the span as a known 4F span.
[0050] FIG. 5 shows a second not limiting example of how the
structures of FIGS. 2.1 and 2.2 can be modified in accordance with
the present invention to obtain N.times.2F-SDHNE network elements,
when N>2. More specifically, the not limiting case N=4 is
contemplated here.
[0051] An N.times.2F-SDHNE network element is formed essentially of
a system called Digital Cross Connect (DXC) known per se, which
realizes a non-blocking cross-connection capability among the
various access ports of the network element itself, not illustrated
in the figure, as they are also known.
[0052] The bidirectional arrows inside N.times.2F-SDHNE indicate
the following types of non blocking cross-connection thus
realized:
[0053] cross-connection between ports for high bit rate data flows
belonging to fibers of the same pair (2F31, 2F32, . . . 2F61, 2F62)
or different pairs of the same span (e.g. 2F31 with 2F41 of span
TR1, or 2F52 with 2F62 of span TR2);
[0054] cross-connection between ports of high bit rate data flows
belonging to different pairs of fibers of different spans, from
anyone towards another one of these (e.g. 2F61 with 2F41, or 2F52
with 2F31);
[0055] connections between said high speed ports 2F31, . . . 2Fnn
with local ports TRIB4 for local data flows at lower bit rate.
[0056] From the above functional description, a person skilled in
the art is able to realize the Digital Cross Connect (DXC) system,
taking also into account what has been described in connection with
the above known structures. The dimensioning of the network element
depends on the dimension of the flows to be routed, in accordance
with the structures of the information frames defined e.g. in the
ITU-T Recommendation G.707.
[0057] The cross-connection functionality thus realized, therefore,
is such as to connect in a non-blocking bidirectional way the port
of high speed line spans 2Fnn with the local flow ports TRIB4, and
the line span ports to each other according to all the possible
combinations.
[0058] In case of failure in a span, e.g. pair 2F51, the
N.times.2F-SDHNE network element is able to switch the given flows
on another span, e.g. pair 2F32, thus realizing a sort of
re-routing of flows from different spans which was not possible to
realize with the known system, even complex, described above.
[0059] Therefore, also in this case it is possible to configure a
high speed span provided with a number N of pairs of fibers
preferably composed of N independent connectional spans of pairs of
fiber 2F, thanks to the new configuration according to the
invention, which allows a cross-connection between ports for high
bit rate data flows belonging to different fiber spans.
[0060] This was not possible in conventional systems.
* * * * *