U.S. patent application number 16/398863 was filed with the patent office on 2019-08-22 for optical networking with support for unidirectional optical links.
The applicant listed for this patent is Neptune Subsea IP Limited. Invention is credited to Herve A. Fevrier.
Application Number | 20190260473 16/398863 |
Document ID | / |
Family ID | 56069160 |
Filed Date | 2019-08-22 |
![](/patent/app/20190260473/US20190260473A1-20190822-D00000.png)
![](/patent/app/20190260473/US20190260473A1-20190822-D00001.png)
![](/patent/app/20190260473/US20190260473A1-20190822-D00002.png)
![](/patent/app/20190260473/US20190260473A1-20190822-D00003.png)
![](/patent/app/20190260473/US20190260473A1-20190822-D00004.png)
United States Patent
Application |
20190260473 |
Kind Code |
A1 |
Fevrier; Herve A. |
August 22, 2019 |
OPTICAL NETWORKING WITH SUPPORT FOR UNIDIRECTIONAL OPTICAL
LINKS
Abstract
An apparatus includes first bidirectional communications
equipment having a transmitter and a receiver. The first
bidirectional communications equipment is configured to operate in
at least a first configuration and a second configuration. In the
first configuration, the first bidirectional communications
equipment is configured to provide a bidirectional communication
link with a transmitter and a receiver of second bidirectional
communications equipment. In the second configuration, the first
bidirectional communications equipment is configured to provide (i)
a first unidirectional communication link between the transmitter
of the first bidirectional communications equipment and the
receiver of the second bidirectional communications equipment and
(ii) a second unidirectional communication link between the
receiver of the first bidirectional communications equipment and a
transmitter of third bidirectional communications equipment.
Inventors: |
Fevrier; Herve A.; (Miami,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Neptune Subsea IP Limited |
London |
|
GB |
|
|
Family ID: |
56069160 |
Appl. No.: |
16/398863 |
Filed: |
April 30, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15152358 |
May 11, 2016 |
10320484 |
|
|
16398863 |
|
|
|
|
PCT/GB2016/051320 |
May 9, 2016 |
|
|
|
15152358 |
|
|
|
|
62159694 |
May 11, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 10/2581 20130101;
H04B 10/40 20130101; H04J 14/021 20130101; H04B 10/275
20130101 |
International
Class: |
H04B 10/2581 20060101
H04B010/2581; H04B 10/275 20060101 H04B010/275; H04B 10/40 20060101
H04B010/40; H04J 14/02 20060101 H04J014/02 |
Claims
1. An apparatus comprising: first bidirectional communications
equipment comprising a transmitter and a receiver, wherein the
first bidirectional communications equipment is configured to
operate in at least a first configuration and a second
configuration; wherein, in the first configuration, the first
bidirectional communications equipment is configured to provide a
bidirectional communication link with a transmitter and a receiver
of second bidirectional communications equipment; and wherein, in
the second configuration, the first bidirectional communications
equipment is configured to provide (i) a first unidirectional
communication link between the transmitter of the first
bidirectional communications equipment and the receiver of the
second bidirectional communications equipment and (ii) a second
unidirectional communication link between the receiver of the first
bidirectional communications equipment and a transmitter of third
bidirectional communications equipment.
2. The apparatus of claim 1, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
provide the first unidirectional communication link with a
different capacity or bandwidth than the second unidirectional
communication link.
3. The apparatus of claim 1, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different frequencies or wavelengths for the first and second
unidirectional communication links.
4. The apparatus of claim 1, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different forward error correction (FEC) codes for the first
and second unidirectional communication links.
5. The apparatus of claim 1, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different modulation formats for the first and second
unidirectional communication links.
6. The apparatus of claim 1, wherein the first bidirectional
communications equipment further comprises additional bidirectional
interfaces configured to provide additional bidirectional or
unidirectional communication channels.
7. The apparatus of claim 1, wherein the first bidirectional
communications equipment comprises an optical interface card, the
optical interface card comprising the transmitter and the receiver
of the first bidirectional communications equipment.
8. The apparatus of claim 1, wherein the first and second
unidirectional communication links provision a bidirectional link
between a first location at which the first bidirectional
communications equipment is located and a second location, the
first unidirectional communication link having a different optical
path than the second unidirectional communication link.
9. A method comprising: configuring first bidirectional
communications equipment to operate in one of a first configuration
of the first bidirectional communications equipment or a second
configuration of the first bidirectional communications equipment;
wherein the first bidirectional communications equipment comprises
a transmitter and a receiver; wherein, in the first configuration,
the first bidirectional communications equipment is configured to
provide a bidirectional communication link with a transmitter and a
receiver of second bidirectional communications equipment; and
wherein, in the second configuration, the first bidirectional
communications equipment is configured to provide (i) a first
unidirectional communication link between the transmitter of the
first bidirectional communications equipment and the receiver of
the second bidirectional communications equipment and (ii) a second
unidirectional communication link between the receiver of the first
bidirectional communications equipment and a transmitter of third
bidirectional communications equipment.
10. The method of claim 9, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
provide the first unidirectional communication link with a
different capacity or bandwidth than the second unidirectional
communication link.
11. The method of claim 9, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different frequencies or wavelengths for the first and second
unidirectional communication links.
12. The method of claim 9, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different forward error correction (FEC) codes for the first
and second unidirectional communication links.
13. The method of claim 9, wherein, in the second configuration,
the first bidirectional communications equipment is configured to
use different modulation formats for the first and second
unidirectional communication links.
14. The method of claim 9, wherein the first and second
unidirectional communication links provision a bidirectional link
between a first location at which the first bidirectional
communications equipment is located and a second location, the
first unidirectional communication link having a different optical
path than the second unidirectional communication link.
15. A non-transient computer readable medium comprising
instructions that, when executed, are configured to: configure
first bidirectional communications equipment to operate in one of a
first configuration of the first bidirectional communications
equipment or a second configuration of the first bidirectional
communications equipment; wherein the first bidirectional
communications equipment comprises a transmitter and a receiver;
wherein, in the first configuration, the first bidirectional
communications equipment is configured to provide a bidirectional
communication link with a transmitter and a receiver of second
bidirectional communications equipment; and wherein, in the second
configuration, the first bidirectional communications equipment is
configured to provide (i) a first unidirectional communication link
between the transmitter of the first bidirectional communications
equipment and the receiver of the second bidirectional
communications equipment and (ii) a second unidirectional
communication link between the receiver of the first bidirectional
communications equipment and a transmitter of third bidirectional
communications equipment.
16. The non-transient computer readable medium of claim 15,
wherein, in the second configuration, the first bidirectional
communications equipment is configured to provide the first
unidirectional communication link with a different capacity or
bandwidth than the second unidirectional communication link.
17. The non-transient computer readable medium of claim 15,
wherein, in the second configuration, the first bidirectional
communications equipment is configured to use different frequencies
or wavelengths for the first and second unidirectional
communication links.
18. The non-transient computer readable medium of claim 15,
wherein, in the second configuration, the first bidirectional
communications equipment is configured to use different forward
error correction (FEC) codes for the first and second
unidirectional communication links.
19. The non-transient computer readable medium of claim 15,
wherein, in the second configuration, the first bidirectional
communications equipment is configured to use different modulation
formats for the first and second unidirectional communication
links.
20. The non-transient computer readable medium of claim 15, wherein
the instructions are executed by a network management system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIM
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/152,358 filed on May 11, 2016, which claims
priority under 35 U.S.C. .sctn. 119(e) to U.S. Provisional Patent
Application No. 62/159,694 filed on May 11, 2015 and which claims
priority as a continuation of PCT Patent Application No.
PCT/GB2016/051320 filed on May 9, 2016. All of these patent
applications are hereby incorporated by reference in their
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to an optical network,
optical networking equipment, and a method of provisioning an
optical network.
BACKGROUND
[0003] Telecommunication networks are networks that allow
communication of information over a distance, and often a great
distance, via the use of electromagnetic signals. Telecommunication
networks based on propagation of electronic signals through
electrical conductors have been available since the time of the
telegraph. Telecommunication networks based on propagation of
optical signals have been a more recent development. Regardless,
the invention and improvement in the ability of human beings to
communicate over distances, often great distances, have presented a
paradigm shift in human interaction, greatly benefiting human
civilization.
[0004] Conventional telecommunications technology represents the
culmination of decades, and in some cases, centuries of human
thought and collaboration. At present, sophisticated optical
communication networks are capable of transmitting tens of
trillions of bits of information per second over a single optical
fiber spanning from a few kilometres to a few thousands of
kilometres. Optical networks generally exceed the bandwidth
capabilities of wired copper networks. Accordingly, optical
networks often provide optical backbones at the core of the
telecommunication networks.
[0005] Typically, these core optical networks use Dense Wavelength
Division Multiplexed (DWDM) optical systems in which optical
channels (referred to as "DWDM channels") are allocated by
frequency range. These optical systems employ equipment in
different sites of the network, each site composed of network
elements that constitute the physical layer of the network.
Conventional optical networks are often mesh networks with
protection and restoration capabilities, and in which there are
Reconfigurable Optical Add/Drop Multiplexers (ROADMs) at the nodes
of the mesh network.
[0006] Optical networks are often configured and provisioned
through a "network management system", which allows one or more
people in a network operations center to change the configuration
of the network, to monitor the activity and performance of the
network, and so forth.
[0007] The ROADMs are typically multi-degree ROADMs, which means
that there are different possible paths starting and ending from
each multi-degree ROADM node. The number of degrees is the number
of paths.
[0008] A second type of node is in-line amplifiers (ILA). These
in-line amplification nodes may use Erbium-doped fiber amplifiers
(EDFAs) and can also use Raman amplification (alone or in
combination with EDFAs).
[0009] Raman amplification can be used to extend the optical reach
(by improving the Optical Signal to Noise Ratio--OSNR) and/or
expanding the optical bandwidth of the DWDM optical systems and
therefore the capacity.
[0010] A third type of node is emerging today and is named optical
transport network (OTN) switches. OTN switching are nodes with
optoelectronic conversion. These are not all-optical nodes like ILA
and ROADM nodes.
[0011] Telecommunication networks started because of voice traffic
needs. They started based on the provisioning of circuits in order
to put in communications two sites, A and B. The circuit was
bidirectional, which means A talks to B and B talks to A. The
capacity in each direction is the same.
[0012] This has been true from the 64 kbit/s circuit up to the
high-speed/high-capacity channels in the different hierarchies of
optical networks: Sonet/SDH, OTN, etc.
[0013] It is known that now data traffic has overpassed voice
traffic in terms of volume. Data traffic is often based on networks
using Internet Protocol (IP).
[0014] Data traffic is sometimes bidirectional but can also be
unidirectional. Bidirectional means that the same capacity is
required in both directions between the two sites of
communications. Unidirectional means traffic is going only in one
direction (or essentially in one direction, as there is the
possibility of the need for a small capacity in the other direction
in order to acknowledge to the emitting site that the flow of
communications is going well).
[0015] An example of the need for unidirectional traffic is the
copy of a database from one site to another site. Bidirectional and
unidirectional traffic types are two extremes, and intermediate
cases are also possible. Therefore, one could characterize traffic
by its asymmetry.
[0016] Despite the emergence of asymmetric traffic, optical
networks conventionally have optical circuits provisioned in a
bidirectional fashion. This is in adherence to ITU-T standards (see
website itu.org). One fundamental object in optical networks
provisioned in accordance with these standards continues to be the
OCh element (Optical Channel). This OCh element continues to be the
basic element in the OTH (Optical Transport Hierarchy). The OCh
element is a bidirectional circuit (by definition in the
standards).
SUMMARY
[0017] According to a first aspect, there is provided an apparatus
comprising bidirectional communications equipment for communicating
information along optical fibers, wherein the bidirectional
communications equipment is configured to provide a first
unidirectional communication link from the equipment to a first
location, and a second unidirectional communication link to the
equipment from a different second location.
[0018] The bidirectional communications equipment (which can be a
DWDM communication equipment incorporating
multiplexers/demultiplexers, wavelength selective switches, optical
amplifiers, etc.) may comprise a transmitter and receiver, the
transmitter and receiver operable to:
[0019] i) provide a bidirectional communication link over an
optical fiber pair with a transmitter and receiver of a second
bidirectional communications equipment; and
[0020] ii) alternatively provide a first unidirectional
communication link between the transmitter of the first
bidirectional communications equipment and the receiver of the
second bidirectional communications equipment, and a second
unidirectional communication link between the receiver of the first
bidirectional communications equipment and a transmitter of a third
bidirectional communications equipment.
[0021] The bidirectional communications equipment may be operable
to provide the first unidirectional communication link with a
different capacity than the second unidirectional communication
link.
[0022] The first bidirectional communications equipment may be
operable to use a different wavelength for the first and second
unidirectional communication links.
[0023] Each bidirectional communications equipment may comprise (or
consist exclusively of) a transmitter and receiver pair of a
bidirectional interface card.
[0024] According to a second aspect, there is provided an optical
network comprising first, second and third bidirectional
communications equipment according to the first aspect, a first
optical fiber link connecting a transmitter of the first
bidirectional communications equipment and a receiver of the second
bidirectional communications equipment, and a second optical fiber
link connecting a receiver of the first bidirectional
communications equipment and a transmitter of the third
bidirectional communications equipment, wherein the optical network
is configured with a first unidirectional communications link along
the first optical fiber link and a second unidirectional
communications link along the second optical fiber link.
[0025] The optical network may further comprise a third optical
fiber connecting a transmitter of the second bidirectional
communications equipment with a receiver of the third bidirectional
communications equipment, the optical network configured with a
third unidirectional communications link along the third optical
fiber.
[0026] The second unidirectional communications link may differ
from the first unidirectional communications link and/or the third
unidirectional communications link in at least one of: wavelength,
bandwidth, modulation scheme, forward error correction, and
distance.
[0027] According to a third aspect, there is provided a method of
configuring an optical network, the optical network comprising
bidirectional communications equipment for providing a
bidirectional communication link over an optical fiber pair, the
method comprising provisioning unidirectional communication links
using the bidirectional communications equipment.
[0028] The method may comprise increasing a capacity of an existing
optical network by re-configuring the bidirectional communications
equipment.
[0029] Re-configuring the bidirectional communications equipment
may comprise changing software that controls provisioning of
communication links to and from the bidirectional communications
equipment to enable unidirectional links to be provisioned.
[0030] The method may comprise configuring optical fiber
connections between the bidirectional communications equipment to
establish unidirectional communications links between the
bidirectional communications equipment.
[0031] Configuring the optical fiber connections may comprise:
[0032] providing a first optical fiber connecting a transmitter of
a first selected bidirectional communications equipment and a
receiver of a second selected bidirectional communications
equipment, a second optical fiber connecting a receiver of the
first selected bidirectional communications equipment and a
transmitter of the third selected bidirectional communications
equipment, and
[0033] provisioning a first unidirectional communications link
along the first optical fiber, and a second unidirectional
communications link along the second optical fiber.
[0034] The first unidirectional communications link may have a
different bandwidth than the second unidirectional communications
link.
[0035] A first and second unidirectional communications link may be
used to provision a bidirectional communications link between a
first location and a second location, with the first unidirectional
link having a different optical path than the second unidirectional
communications link.
[0036] According to a fourth aspect, there is provided a
non-transient computer readable medium comprising instructions
that, when run on bidirectional communications equipment, causes
the bidirectional communications equipment to be operable to
provision unidirectional communication links.
[0037] According to a fifth aspect, there is provided a network,
comprising: a plurality of bidirectional communications equipment,
a network management server, and a data communications network
connecting the network management server with the bidirectional
communications equipment, wherein the server is configured to
provision bidirectional communications links using the
bidirectional communications equipment.
[0038] The features of any aspect may be combined with those of any
other aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] For a more complete understanding of this disclosure,
reference is made to the following description, taken in
conjunction with the accompanying drawings, in which:
[0040] FIG. 1 illustrates an example network apparatus comprising
DWDM equipment at the boundary of the optical network where the
interface cards are located;
[0041] FIG. 2 illustrates an example network management
environment;
[0042] FIG. 3 illustrates an example optical network in which
bidirectional connections are used to provide all the optical
communications links;
[0043] FIG. 4 shows an example of an optical network according to
an embodiment of this disclosure; and
[0044] FIGS. 5 through 8 illustrate example simulation results
associated with an optical network according to an embodiment of
this disclosure.
DETAILED DESCRIPTION
[0045] FIGS. 1 through 8, discussed below, and the various
embodiments used to describe the principles of the present
invention in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
invention. Those skilled in the art will understand that the
principles of the invention may be implemented in any type of
suitably arranged device or system.
[0046] One aspect of this disclosure relates to the possibility to
provision unidirectional circuits as the basic "circuit object" in
an optical network, where the equipment is kept "bidirectional".
The "bidirectional equipment" means, for example, that traffic
interface cards are kept, as before, as transmit/receive interface
cards. A difference from a hardware perspective may be in the
optical cables on the client side or line side of the traffic
interface cards of the optical network.
[0047] FIG. 1 illustrates an example network apparatus 100,
comprising DWDM equipment 120 at the boundary of the optical
network showing the client side 121 and the line side 122 of an
optical interface card 123. The DWDM equipment 120 comprises
bidirectional communications equipment, in the form of a
bidirectional optical interface card 123. The client side 121 of
the interface card 123 comprises a receiver 101 and a transmitter
102. The line side of the interface card 122 also comprises a
receiver 112 and a transmitter 111. The DWDM equipment may further
comprise other equipment (not represented in FIG. 1) such as
optical amplifiers, multiplexers, demultiplexers, etc. . . .
[0048] The DWDM equipment also comprises a processing device 160.
The processing device 160 may control the configuration of the
equipment 120, for instance provisioning communication links via
the optical interface card 123. The processing device 160 executes
instructions that may be loaded into a memory 161. The processing
device 160 may include any suitable number(s) and type(s) of
processors or other devices in any suitable arrangement. Example
types of processing devices 160 include microprocessors,
microcontrollers, digital signal processors, field programmable
gate arrays, application specific integrated circuits, and discrete
circuitry.
[0049] The memory 161 represents any structure(s) capable of
storing and facilitating retrieval of information (such as data,
program code, and/or other suitable information on a temporary or
permanent basis). The memory 161 may represent a random access
memory, read only memory, hard drive, Flash memory, optical disc,
or any other suitable volatile or non-volatile storage
device(s).
[0050] The processing device 160 may be connected to a data
communications network (not shown in FIG. 1, but shown in more
detail in FIG. 2), and may be instructed how to configure the
equipment 120 via the data communications network.
[0051] A first cable 103 connects equipment 105A to the receiver
101 of the client side 121 of the interface card 123. A second
cable 104 (e.g. an optical cable) connects equipment 105B to the
transmitter 102 of the client side of the interface card 121.
Equipment 105A can transmit network traffic (e.g. data) through the
first cable 103 and the client side 121 of the interface card 123
into the line side 122 of the interface card 123 and into the
optical network (via the line side 122 of the interface card 123).
Equipment 105B can similarly receive network traffic from the line
side 121 of the interface card 123 via the second cable 104 (e.g.
an optical cable).
[0052] The line-side 121 of the bidirectional optical interface
card 123 may be configured to provide a bidirectional optical
communication link via first and second fibers 113, 114 of a fiber
pair, receptively connected to the transmitter 111 and receiver
112. Alternatively, unidirectional communications links may be
established over each of the first and second fibers 113, 114.
[0053] Optics is essentially unidirectional. This means that
existing network elements such as in-line amplifiers (ILA), optical
transport network (OTN) switches or reconfigurable optical add-drop
multiplexers (ROADMs) have bidirectional architectures to support
the provisioning of bidirectional circuits, but the optical
functions/the optical modules operate on light which is propagating
in one single direction. It is conventional to establish
bidirectional circuits using fiber pairs in existing optical
networks.
[0054] In each fiber of such a fiber pair, light propagates in one
direction. Conventional optical amplifiers are unidirectional in
nature. Even if it is possible to create "bidirectional" optical
amplifiers, Erbium-doped fiber amplifiers (EDFAs) and Raman
amplifiers have, thus far, been essentially deployed in optical
networks in such a way that light propagates inside these
amplifiers in one direction. Existing ROADM nodes have
architectures that work in conjunction with fiber pairs, switching
connections between fiber pairs.
[0055] Traffic interface cards have a transmit side and a receive
side, since optical amplifiers and switching modules (e.g.
wavelength selective switching (WSS) modules) are essentially
unidirectional in nature. Today, the transmit side may be tunable,
which means that it is possible to provision the card in order to
tune the laser of the transmit side to emit on the desired optical
frequency. Regarding the receive side, in the case of direct
detection, the receive side is broadband, which means that it does
not need to be tuned to be able to receive a particular incoming
wavelength of the incoming optical channel. Instead, the receiver
may be able to receive with a good performance any wavelength in
the spectrum of transmission. In the case of coherent detection,
there is a local oscillator/laser, which can be tunable and can be
tuned to the incoming wavelength.
[0056] FIG. 2 illustrates a network management environment 200,
which includes various network elements. The network elements may
comprise communications equipment (such as bidirectional interface
cards, ROADMS, ILAs, OTAs etc) which may be configured as racks of
electronics/optoelectronics. The different sites that include one
or more of such network elements are labelled 201(2) through
201(N), where "N" is an integer representing the number of sites.
Although each network site 201 may contain multiple network
elements, for simplicity, only two network elements A and B are
illustrated.
[0057] The network elements of the various network element sites
201 connect to a server 202 over a data communications network
(DCN) 205. The server 202 runs thereon software which may be
referred to as a network management system 203. More generally, a
network management system 203 may be implemented on any suitable
processor, as firmware, software, or hardware, provided it is
capable of controlling the configuration of network elements to
provision optical communications links.
[0058] The network elements within the various network element
sites 201 are configured to provide a telecommunications network
206 in accordance with instructions received from the network
management system 203. For example, ROADMs at various sites may be
configured to establish unidirectional optical paths between
specific ports of bidirectional interface cards in different
network sites. The interface cards may be instructed to provision
unidirectional or bidirectional communications links over the
established optical paths, in order to satisfy a demand for
communications capacity between those two sites. Bidirectional
interface cards may receive commands specifying a modulation scheme
or forward error correction scheme for each unidirectional (or
bidirectional) communications link.
[0059] This data communications network 205 may be a private
telecommunications network so as to prevent intrusion and possible
disruptions to service in the telecommunication system served by
the network elements of the network element sites 201.
[0060] The data communications network 205 may be an Internet
Protocol (IP) based network, where each network element (and the
server that runs the network management system 202) has a different
IP address. The network management system 203 may have access to
storage 204 of a large storage capacity, which is used to store
large volumes of data (perhaps in a database) corresponding to the
optical network. For instance, the network management system might
cause performance monitoring data to be stored within the storage
204.
[0061] The design of network elements A and B may be such that it
is possible to monitor quality of the transmission and to monitor a
whole set of parameter settings of the hardware modules. These
measurements may be stored in the storage 204 (which again could be
organized in a database).
[0062] FIG. 3 illustrates a network that is provisioned using
bidirectional channels, using bidirectional communications
equipment, in order to satisfy a demand for communications capacity
from A to B (100 G), from C to A (200 G) and from B to C (100 G). A
number of bidirectional communication links may already link these
locations, and the demand for additional capacity may arise from a
recognition that traffic is asymmetric. According to existing
optical communications standards, it is necessary to establish a
bidirectional communications path between A and B, between B and C
and between C and A, as shown in FIG. 3.
[0063] Bidirectional communications equipment A, B and C are
respectively located in three separate locations (e.g. cities A, B
and C). Each bidirectional equipment A, B, and C respectively
comprises two bidirectional interface cards A1, A2; B1, B2; and C1,
C2 (and may include other bidirectional interface cards (not
shown).
[0064] In order to establish communications capacity between A and
B using a conventional bidirectional communications link, a
bidirectional optical path consisting of paired optical paths AB
and BA connects bidirectional interface A1 with bidirectional
interface B1. Similarly a bidirectional optical path consisting of
paired optical paths AC and CA connects bidirectional interface A2
with bidirectional interface C1. A bidirectional optical path
consisting of paired optical paths CB and BC connects bidirectional
interface C2 with bidirectional interface B2. The optical paths of
each pair follow the same path (e.g. provided by a fiber pair), and
are connected pairwise at each ROADM, as mentioned above.
[0065] The optical fiber connections between A, B and C are routed
via ROADMs 131-134. According to conventional optical
communications standards, ROADMs 131-134 are operable to allow
fiber-pair connections to be re-routed, to connect different
bidirectional interfaces together.
[0066] The optical paths and bidirectional communications links in
FIG. 3 may be established in response to instructions provided to
the various network elements (A1, A2, B1, B2, C1, C2, 131, 132,
133, 134) from a network management system, as described with
reference to FIG. 2 (but not shown in FIG. 3).
[0067] Using bidirectional communications equipment to provision
the capacities requires the use of a total of 6 bidirectional
interface cards (A1-C2), with 6 optical paths (AB-CA) between
them.
[0068] FIG. 4 shows an example of an optical network 150 according
to an embodiment of this disclosure, that is provisioned to satisfy
the same capacity demand as the example of FIG. 3. The network 150
comprises bidirectional communications equipment at three different
locations. The bidirectional communications equipment at each
location respectively comprises a first, second and third
bidirectional interface A, B and C. Each interface A, B, C
respectively has a transmitter 102A, 102B, 102C and a receiver
101A, 101B, 101C. Each interface A, B, C may be, in hardware terms,
a conventional bidirectional interface, such as is already widely
installed in optical communications networks to provide
bidirectional communications over fiber pairs. However, in contrast
to the arrangement of FIG. 3, in the embodiment of FIG. 4 the
bidirectional interfaces A, B, C are used to provision
unidirectional communication links.
[0069] A first unidirectional communications link is provided from
the transmitter 102A of the first interface A to the receiver 101B
of the second interface B, via optical fiber link AB. A second
unidirectional communications link is provided from the transmitter
102C of the third interface C to the receiver 101A of the first
interface A, via optical fiber link CA. A third unidirectional
communications link is provided from the transmitter 102B of the
second interface B to the receiver 101C of the third interface C,
via optical fiber link BC.
[0070] The optical links AB, CA, BC may comprise optical fiber
spans that are interconnected by ROADMs 131-134, or other optical
components (e.g. repeaters, etc.). In the present embodiment, the
optical fiber link AB comprises a first fiber span connecting
transmitter 102A to ROADM 131, a second fiber span connecting ROADM
131 with ROADM 132, and a third fiber span connecting ROADM 132
with receiver 101B. Optical fiber link CA comprises a fourth fiber
span connecting transmitter 102C to ROADM 133, a fifth fiber span
connecting ROADM 133 to ROADM 134, a sixth fiber span connecting
ROADM 134 to ROADM 131, and a seventh fiber span connecting ROADM
131 to receiver 101A. Optical fiber link BC comprises an eighth
fiber span connecting transmitter 102B to ROADM 132, a ninth fiber
span connecting ROADM 132 to ROADM 133, and a tenth fiber span
connecting ROADM 133 to receiver 101C.
[0071] The bidirectional communications equipment at each location
may be provided with further bidirectional interfaces, which may be
configured to provide bidirectional communication channels, or
further unidirectional communication channels, depending on the
needs of the network.
[0072] The optical carriers in the unidirectional communication
links provided by a single bidirectional communications interface
(A, B or C) may have different optical frequencies or wavelengths,
and they may also carry different capacities/bandwidths, have
different modulation formats, and/or different forward error
correction (FEC) codes.
[0073] In the example of FIG. 4, there may be a relatively short
distance from B to C, enabling a modulation scheme with increased
bandwidth (e.g. 200 G, i.e. 200 gigabits per second) to be used for
the third unidirectional communications link. The distance from A
to B may preclude a 200 G link, so the first unidirectional
communications link may be configured as a 100 G link. In the
example, the first and third communications links are also
configured with different wavelengths .lamda..sub.1 and
.lamda..sub.3, respectively. The bidirectional interface B
therefore provides unidirectional communications links with
different bandwidths and wavelengths. The second unidirectional
communications link uses a wavelength .lamda..sub.2 that is
different to .lamda..sub.1 and .lamda..sub.3.
[0074] The optical paths and bidirectional communications links in
FIG. 4 may be established in response to instructions provided to
the various network elements (A B, C, 131, 132, 133, 134) from a
network management system, as described with reference to FIG. 2
(but not shown in FIG. 4).
[0075] In FIG. 4, using the principles disclosed herein, only three
bidirectional interfaces and only three optical paths are necessary
to provide the required capacity, which is in contrast to FIG. 3,
which requires six bidirectional interfaces and six optical paths.
The cost of establishing enhanced capacity according to embodiments
is therefore substantially decreased.
[0076] It can be understood from comparing FIG. 4 with FIG. 3 that
the a network similar to that of FIG. 2 can be re-configured
according to an embodiment with little or no hardware
modifications, provided that the management software of the various
elements of the network (e.g. interfaces, ROADMs, etc.) is capable
of provisioning unidirectional optical channels. If the ROADMs are
configured to switch single fibers, rather than fiber pairs, then
unidirectional fiber links can be established arbitrarily by the
ROADMs between transmitters and receivers of different
bidirectional interfaces. Where the bidirectional communications
equipment comprises a plurality of bidirectional interfaces, some
can be configured to provide conventional bidirectional
communications links and others to provide unidirectional
communications links, potentially leaving a "spare" unidirectional
communications port (from which a communications link can be
established) that can be provisioned for a different route.
[0077] Embodiments of the disclosure therefore enable an optical
network in which existing bidirectional equipment is able to
provision unidirectional circuits. Embodiments may reside in a
significant modification of the objects manipulated by the
management software that controls provisioning of optical
communication links (or channels) and also of software that
controls the operation of the network elements themselves (such as
ROADMs and interface cards).
[0078] A network or apparatus configured in accordance with an
embodiment does not follow existing ITU-T standards, because the
concept of Optical Channel (OCh), which is the fundamental element
of optical communications networks according to existing standards,
needs to be drastically changed. Optical network standards are
found on the ITU-T website. Relevant documents include the G
Recommendations: G.692, G.709 and G.853.1.
[0079] In contrast with conventional systems, one fundamental
element for network provisioning and management in embodiments of
this disclosure is a unidirectional oriented optical channel, which
may be denoted UOCh. UOCh(A,B) designates a unidirectional oriented
channel from A to B. This may be the fundamental unit which is to
be provisioned in accordance with embodiments of this
disclosure.
[0080] A bidirectional optical channel may also be able to be
provisioned: BOCh(A,B). Such a bidirectional channel may not be
only the sum of two unidirectional optical channels traveling in
opposite directions along the same path. In embodiments, a
bidirectional channel may be established or provisioned using
different optical paths (i.e. with a different topology, traversing
different nodes of the network). The ability to use different
optical paths for each direction in a bidirectional optical path
provides for a wider range of possibilities for establishing
optical restoration or optical protection (because of the far
greater permutations of optical paths that may be available). This
is in contrast to existing bidirectional communications channels
OCh in which protection paths in both directions stay together.
[0081] Moreover, in the hierarchy of the organization of the
objects managed at the network management level (similar to the
optical transport hierarchy), one can also consider "groups" of
unidirectional (UOCh) or bidirectional (BOCh) optical channels.
These groups of optical channels may also be treated the same way
with respect to optical protection and restoration.
[0082] Embodiments of this disclosure are able, by an appropriate
network management architecture and set of objects manipulated, to
create an optical network using bidirectional equipment to create
the network elements in which it is possible to provision circuits
that are either unidirectional (UOCh) or bidirectional (BOCh).
[0083] According to an embodiment of this disclosure, it is
possible to combine easily in the same network asymmetric
circuits/optical channels and symmetric circuits/optical channels.
This provides economic benefits (e.g. network cost) that are even
greater than those achievable with conventional approaches.
[0084] In order to maximise these benefits, network planning can be
adapted to the approach of unidirectional circuits. This will
provide benefits by reducing congestion and making better use of
network resources. Embodiments may also provide benefits in terms
of protection and restoration at the network level. According to
embodiments of this disclosure, asymmetric traffic may be
provisioned with a maximum granularity. For example: one can
provide different bandwidths for each of the two traffic directions
. . . 100 G/200 G, 100 G/300 G, 100 G/400 G, 100 G/500 G, 200 G/300
G, 300 G/400 G, etc. (here it is assumed the granularity for
optical channels is 100 G).
[0085] In order to more clearly demonstrate the advantages
associated with embodiments of this disclosure, the concepts
disclosed herein were applied to a simulated US-wide optical
network.
[0086] The network simulations were done using a modified version
of the open source tool Net2Plan (developed at Universidad
Politecnica de Cartagena, Spain) as a framework. For this study,
the continental US reference network CORONET was used. A full mesh
set of bidirectional IP traffic demands were generated between
eleven areas of data centers. The traffic weighting and locations
of these data centers were allocated between the following 11
cities: NYC (241 data centers), Washington D.C. (196), San
Francisco (178), Los Angeles (153), Dallas (150), Chicago (141),
Atlanta (84), Seattle (72), Miami (67), Phoenix (62), and Houston
(60).
[0087] Three optical line system configurations were simulated to
show benefits of reach and spectral bandwidth: a 90-channel
EDFA-only configuration with 2000 km reach, a 90-channel hybrid
EDFA/Raman configuration with 4500 km reach, and a 150-channel
all-Raman configuration with 3800 km reach. The reachability
figures for the three line systems are based upon the current
generation coherent 100 G DP-QPSK (dual polarisation quadrature
phase shift keyed) modulation format at 50 GHz channel-spacing with
an average of 92 km spans between in-line amplification sites. The
reachability distances were determined by OSNR benefits of the
hybrid EDFA/Raman system: approximately 2.5 times the reachability
at short wavelength compared to the EDFA-only solution. For the
all-Raman system, additional penalties for L-band are considered
which reduces the reachability to 3800 km.
[0088] For each of the three optical line system configurations,
two simulation sets were done for accommodating the generated
IP-traffic demands (each set including simulations of EDFA only,
all Raman, and hybrid optical line system configuration). The first
simulation set was done with the typical bidirectional optical
channel circuit configurations that are currently deployed in DWDM
long-haul optical networks. The second simulation set employed a
network configured in accordance with an embodiment, allowing for
provisioning of unidirectional optical channels using bidirectional
network elements. Both simulations used the same set of transponder
equipment, with the only difference being how the software
configures the provisioning and management of optical
channels/communication links.
[0089] FIG. 5 shows a graph illustrating the average carried
traffic in the busiest 10% of links in the network. A moderate
traffic growth was assumed, matching the top 10% of the busiest
routes in the simulated network with the traffic growth expected in
Metro Network Traffic Growth: An Architecture Impact Study,
Alcatel-Lucent Bell Labs White Paper, December 2013. This study
uses an 18.8% percent IP-traffic growth year-over-year throughout
the network over a twenty-year period.
[0090] Within the simulation, a full-mesh of IP-traffic demands are
generated between data centres, with an average asymmetry ratio of
0.5. An asymmetry ratio of 0.5 indicates that there is twice as
much IP-traffic flowing in one direction compared to the opposite
direction of the demand. In the simulations, this asymmetry ratio
is uniformly distributed between 0.25 and 0.75 and the direction of
asymmetry is randomized. The traffic demands are routed with
Dijkstra's shortest-path algorithm.
[0091] A variety of network design metrics are the output from
these simulations including total IP-traffic, total optical channel
traffic, total number of transponders, spectrum utilization,
bottleneck link utilization, transponder port utilization, route
quality, and yearly and cumulative summaries of total network cost.
Total costs of the network are composed of fiber leasing costs,
operations and maintenance costs, space and power costs, in-line
amplification equipment costs, ROADM site costs, and transponder
costs.
[0092] The capacity on the top 10% of the busiest routes in the
simulated network exceeds the capacity offered by EDFA-only or
hybrid EDFA/Raman configurations in 2024 (assuming 100 G channels).
At this point in time, the total spectrum usage across the whole
network (and not only for the busiest routes) is about 53% for
EDFA-only or hybrid EDFA/Raman configurations and 31% for all-Raman
equipment. All-Raman amplification provides high bandwidth by
offering more room for optical channels, thus delaying the need to
equip new fiber pairs (which leads to the need to deploy and
operate additional common equipment) to meet capacity demands on
the busiest routes.
[0093] In addition, the long reach capability enabled by Raman
amplification reduces the number of regeneration sites required
over long optical data paths, leading to a reduction of about 20%
in the number of transponder cards throughout the network. The
difference in the number of transponder cards between hybrid
EDFA/Raman (4500 km reach) and all-Raman (3800 km reach)
amplification schemes is only about 3%.
[0094] FIG. 6 includes a graph 501 illustrating the reduction in
100 G network transponders for the second set of simulations (cf
the first set) for configurations with: EDFA only 502, all Raman
amplification 503 and hybrid amplification 504. Savings of 15-25%
in network transponders can be made according to some embodiments.
The capability to provision unidirectional optical communication
links makes more efficient use of network hardware, including fiber
links between locations which may be very expensive to
establish.
[0095] FIG. 6 also includes a graph 511, illustrating the number of
unused ports in transponders in the second set of simulations for
configurations with: EDFA only 512, all Raman amplification 513,
and hybrid amplification 514. The interface cards of the DWDM
platform according to some embodiments are equipped with both
transmit and receive ports, and when these are provisioned
unidirectionally, it may happen that one of the ports is not used.
Between approximately 4 and 6% of ports are unused in the simulated
network configurations of the second set, indicating that ports are
available to provide bandwidth on demand, for example to respond to
an increased demand for communication.
[0096] In DWDM equipment according to an embodiment of this
disclosure, unidirectional optical circuits can be provisioned
using customary bidirectional interface cards: an interface card in
node A can transmit an optical wavelength to node B while the
transmit port of the interface card in node B can transmit an
optical wavelength to another node different from A. Such a DWDM
configuration may not require any new hardware development or
evolution but may require a software architecture enabling
provision of OCh in different ways (unidirectional or bidirectional
depending on the traffic needs). The proposed IP-optimized DWDM
platform therefore does not induce significant extra hardware costs
that might be incurred using conventional approaches.
[0097] FIGS. 7 and 8 illustrate the simulated cost savings in
accordance with an embodiment of this disclosure. FIG. 7
illustrates network cost projections for a conventional EDFA-only
network in which the fundamental channel OCh is bidirectional. FIG.
7 illustrates network cost projections for a network according to
an embodiment of this disclosure, using all-Raman amplification, in
which bidirectional communication equipment can be configured to
provide unidirectional communication links, as appropriate. In both
cases it is assumed that the operators own the fiber infrastructure
in a CORONET-like network.
[0098] The costs are driven by the equipment capital expenses (for
ILAs 601; ROADMs 602; and transponders TXP 603) and operational
expenses (space and power 604; operation and maintenance 605). The
extra cost required in the first year for longer reach and higher
bandwidth that is enabled by all-Raman amplification is partly
compensated by the lower number of transponders in the
unidirectional all-Raman network approach; this extra cost is
quickly recouped after two years of operation with yearly savings
ranging from $2M to $29M, the highest savings being observed in the
years (e.g. 2025, 2029, 2031, 2034) when new fiber pairs need to be
lit in the bidirectional EDFA-only network to respond to the
traffic growth.
[0099] Cost figures for the DWDM equipment are based on Ovum data
showing average selling prices in industry for the equipment as
well as a yearly reduction based on forecasts. Operation,
maintenance, space, power, and fiber leasing expenses are based on
network data such as a monthly lease within a 20-year IRU
(indefeasible right of use). Different cases have been studied,
including operators leasing the fiber infrastructure or operators
who own the fiber infrastructure. Pan-European networks have been
studied as well.
[0100] Unidirectional provisioning using bidirectional equipment
can reduce the number of transponders across a network, reduce the
number of fibers required, and lead to a lower network cost for
operators owning or leasing the fiber infrastructure.
[0101] In some embodiments, various functions described in this
patent document are implemented or supported by a computer program
that is formed from computer readable program code and that is
embodied in a computer readable medium. The phrase "computer
readable program code" includes any type of computer code,
including source code, object code, and executable code. The phrase
"computer readable medium" includes any type of medium capable of
being accessed by a computer, such as read only memory (ROM),
random access memory (RAM), a hard disk drive, a compact disc (CD),
a digital video disc (DVD), or any other type of memory. A
"non-transitory" computer readable medium excludes wired, wireless,
optical, or other communication links that transport transitory
electrical or other signals. A non-transitory computer readable
medium includes media where data can be permanently stored and
media where data can be stored and later overwritten, such as a
rewritable optical disc or an erasable memory device.
[0102] It may be advantageous to set forth definitions of certain
words and phrases used throughout this patent document. The terms
"application" and "program" refer to one or more computer programs,
software components, sets of instructions, procedures, functions,
objects, classes, instances, related data, or a portion thereof
adapted for implementation in a suitable computer code (including
source code, object code, or executable code). The terms
"transmit," "receive," and "communicate," as well as derivatives
thereof, encompasses both direct and indirect communication. The
terms "include" and "comprise," as well as derivatives thereof,
mean inclusion without limitation. The term "or" is inclusive,
meaning and/or. The phrase "associated with," as well as
derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or
with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, have a relationship to or with, or the like.
The phrase "at least one of," when used with a list of items, means
that different combinations of one or more of the listed items may
be used, and only one item in the list may be needed. For example,
"at least one of: A, B, and C" includes any of the following
combinations: A, B, C, A and B, A and C, B and C, and A and B and
C.
[0103] The description in the present application should not be
read as implying that any particular element, step, or function is
an essential or critical element that must be included in the claim
scope. The scope of patented subject matter is defined only by the
allowed claims. Moreover, none of the claims invokes 35 U.S.C.
.sctn. 112(f) with respect to any of the appended claims or claim
elements unless the exact words "means for" or "step for" are
explicitly used in the particular claim, followed by a participle
phrase identifying a function. Use of terms such as (but not
limited to) "mechanism," "module," "device," "unit," "component,"
"element," "member," "apparatus," "machine," "system," "processor,"
or "controller" within a claim is understood and intended to refer
to structures known to those skilled in the relevant art, as
further modified or enhanced by the features of the claims
themselves, and is not intended to invoke 35 U.S.C. .sctn.
112(f).
[0104] While this disclosure has described certain embodiments and
generally associated methods, alterations and permutations of these
embodiments and methods will be apparent to those skilled in the
art. Accordingly, the above description of example embodiments does
not define or constrain this disclosure. Other changes,
substitutions, and alterations are also possible without departing
from the scope of the invention as defined by the following
claims.
* * * * *