U.S. patent application number 17/125766 was filed with the patent office on 2022-04-28 for fast system optimization (fso) with optimally placed recovery tones.
The applicant listed for this patent is Infinera Corp.. Invention is credited to Steven William Beacall, Sumudu Geethika Edirisinghe, Pierre Mertz.
Application Number | 20220131605 17/125766 |
Document ID | / |
Family ID | 1000005401301 |
Filed Date | 2022-04-28 |
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United States Patent
Application |
20220131605 |
Kind Code |
A1 |
Edirisinghe; Sumudu Geethika ;
et al. |
April 28, 2022 |
FAST SYSTEM OPTIMIZATION (FSO) WITH OPTIMALLY PLACED RECOVERY
TONES
Abstract
Described herein is an apparatus including a continuous wave
idler and an optical coupler that provide an optical signal having
a power greater than optical channels carrying data, and positioned
at a cross-over point between two spectral bands, with each band
encompassing multiple optical channels.
Inventors: |
Edirisinghe; Sumudu Geethika;
(Newmarket, GB) ; Mertz; Pierre; (Baltimore,
MD) ; Beacall; Steven William; (Bridgwater,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infinera Corp. |
Annapolis Junction |
MD |
US |
|
|
Family ID: |
1000005401301 |
Appl. No.: |
17/125766 |
Filed: |
December 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63106420 |
Oct 28, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04J 14/0213 20130101;
H04B 10/50 20130101; H04Q 2011/0016 20130101; H04J 14/02 20130101;
H04B 10/032 20130101; H04J 14/0212 20130101; H04J 14/0221 20130101;
H04B 10/296 20130101 |
International
Class: |
H04B 10/032 20060101
H04B010/032; H04J 14/02 20060101 H04J014/02; H04B 10/50 20060101
H04B010/50 |
Claims
1. An apparatus, comprising: an optical transmitter operable to
supply a plurality of first optical signals, each of the plurality
of first optical signals being spaced apart from one another
spectrally, each of the plurality of first optical signals having a
corresponding one of a plurality of first wavelengths; a second
optical transmitter configured to supply a plurality of second
optical signals, each of the plurality of second optical signals
being spaced apart from one another spectrally, each of the
plurality of second optical signals having a corresponding one of a
plurality of second wavelengths wherein a maximum one of the
plurality of first wavelengths and a minimum one of the plurality
of second wavelengths are spaced apart spectrally from one another
encompassing a sub-band of spectrum encompassing a third
wavelength; an ASE idler operable to supply a third optical signal,
the third optical signal having a first power and corresponding to
a plurality of fourth wavelengths; a wavelength selective switch
having a first input port receiving the plurality of first optical
signals, a second input port receiving the plurality of second
optical signals, a third input port receiving the third optical
signal, a first reconfigurable filter associated with the first
input port and operable to pass the first optical signals and block
other optical signals, a second reconfigurable filter associated
with the second input port and operable to pass the second optical
signals and block other optical signals, a third reconfigurable
filter associated with the third input port and operable to pass
selected wavelengths of the third optical signals and block
unselected wavelengths of the third optical signals, and an output
port, the wavelength selective switch operable to combine the
plurality of first optical signals, the plurality of second optical
signals, and the selected wavelengths of the third optical signals
into a fourth optical signal, and wherein the first reconfigurable
filter, the second reconfigurable filter, and the third
reconfigurable filter are operable to block the sub-band of the
spectrum encompassing the third wavelength, a CW idler operable to
supply a fifth optical signal, the fifth optical signal having a
second power greater than the first power and a wavelength
corresponding to the third wavelength, and a power coupler having a
first input port operable to receive the fifth optical signal, a
second input port operable to receive the fourth optical signal,
the power coupler operable to couple the fifth optical signal with
the fourth optical signal.
2. The apparatus of claim 1, wherein the first optical signals are
spaced apart spectrally by a first spacing, and the sub-band of the
spectrum encompassing the third wavelength is spaced apart
spectrally by a second spacing, and wherein the second spacing is
greater than the first spacing.
3. The apparatus of claim 1, wherein the sub-band of the spectrum
encompassing the third wavelength is devoid of the selected
wavelengths of the third optical signal.
4. The apparatus of claim 3, wherein the sub-band of the spectrum
encompassing the third wavelength is devoid of the first optical
signals and the second optical signals.
5. The apparatus of claim 1, wherein the first optical signals have
a third power and the second optical signals have a fourth power,
and wherein the second power of the fifth optical signal is greater
than the third power and the fourth power.
6-10. (canceled)
Description
INCORPORATION BY REFERENCE
[0001] The present patent application claims priority to the
provisional patent application identified by U.S. Ser. No.
63/106,420, filed on Oct. 28, 2020, the entire content of which is
hereby incorporated by reference.
BACKGROUND
[0002] Optical networking is a communication means that utilizes
signals encoded in light to transmit information in various types
of telecommunications networks. Optical networking may be used in
relatively short-range networking applications such as in a local
area network (LAN) or in long-range networking applications
spanning countries, continents, and oceans. Generally, optical
networks utilize optical amplifiers, a light source such as lasers
or LEDs, and wave division multiplexing to enable high-bandwidth,
transcontinental communication.
[0003] Wavelength division multiplexed (WDM) optical communication
systems (referred to as "WDM systems") are systems in which
multiple optical signals, each having a different wavelength, are
combined onto a single optical fiber using an optical multiplexer
circuit (referred to as a "multiplexer"). Such systems may include
a transmitter circuit, such as a transmitter (Tx) photonic
integrated circuit (PIC) having a transmitter component to provide
a laser associated with each wavelength, a modulator configured to
modulate the output of the laser, and a multiplexer to combine each
of the modulated outputs (e.g., to form a combined output or WDM
signal), which may be collectively integrated onto a common
semiconductor substrate.
[0004] A WDM system may also include a receiver circuit, such as a
receiver (Rx) PIC, having a photodiode, and an optical
demultiplexer circuit (referred to as a "demultiplexer") configured
to receive the combined output and demultiplex the combined output
into individual optical signals.
[0005] A WDM system may also include a set of nodes (e.g., devices
of the WDM system that may be utilized to route the multiple
optical signals, add another optical signal to the multiple optical
signals, drop an optical signal from the multiple optical signals,
or the like). During transmission of an optical signal in a WDM
system, a set of intermediate nodes, such as a set of
reconfigurable add-drop multiplexers (ROADMs), may be utilized to
route and/or amplify the optical signal.
[0006] ROADMs are characterized by the number of fiber optic cables
that the ROADMs can be connected to. Each fiber optic cable that a
particular ROADM can be connected to is referred to in the art as a
"degree". Thus, if a particular ROADM is configured to be connected
to four fiber optical cables, then such ROADM is referred to in the
art as having four degrees. For each degree, the ROADM has an
optical device known as a wavelength selective switch connected to
the fiber optic cable. The wavelength selective switch has a
plurality of input ports, and functions to combine and shape the
spectrum of light received at the input ports into a single
combined signal that is passed onto the fiber optic cable. Shaping
the light received at the plurality of input ports includes
blocking optical signals having undesired wavelengths of light
received at the input ports so that the single combined signal does
not include the blocked optical signals. To block the undesired
optical signals, each of the input ports of the wavelength
selective switch includes a separate reconfigurable filter.
[0007] ROADMs may also be provided with a splitter which splits
light and directs the light to ports of the wavelength selective
switches. In colorless, directionless and contentionless networks,
the splitter broadcasts each wavelength of light to all of the N
degrees of the node and the wavelength selective switches select,
for each degree, which wavelengths are blocked and which
wavelengths are let through.
[0008] In fiber optic communications, "perturbation" is a deviation
in the optical signal from its normal course caused by an outside
influence. Nonlinearity is a particular type of perturbation in
which the behavior of the optical signal transmitted from a
transmitter to a receiver deviates from its normal course and does
not vary in direct proportion to the optical signal transmitted at
the transmitter. Examples of nonlinearities include intra-channel
nonlinearities, stimulated Brillouin scattering (SBS), stimulated
Raman scattering (SRS), four wave mixing (FWM), self-phase
modulation (SPM), cross-phase modulation (XPM), and
intermodulation.
[0009] Generally, subsea optical communication systems communicate
over long distances by operating at constant optical power. The
designed power of a data channel in the subsea optical
communication system is the total constant power (in dBm or
milliwatts) divided by the number of data channels that can fit
within the repeater bandwidth of the subsea communication line.
When the subsea optical communication system is not fully populated
with data channels, such as during early installations or during
upgrades where fewer higher capacity channels can replace many
legacy channels, the power per channel of those fewer channels will
be higher than the designed optimal power. In contrast, terrestrial
communication lines generally use constant gain amps, that is, as
channels are added power is added such that the power is the same
for each channel.
[0010] Modern optical communication systems are designed with
spectral windows close to 5 THz (from about 191 THz to about 196
THz) due to the advancement of optical fiber and optical amplifier
technology. This has led to the development and deployment of
optical add drop multiplexing branching unit (OADM-BU) based subsea
cables servicing multiple countries with a single fiber pair. Since
the spectrum is split and shared along branches between different
cable landing stations, in the event of a single or multiple cable
cuts of a branch, the remaining un-cut branches will experience a
drop in performance due to nonlinear penalties induced by the
increased channel power.
[0011] When submarine optical communication systems are
commissioned, they are often equipped with a fraction of the
designed capacity. Submarine repeaters operate at the maximum
designed output power and work on constant output power mode.
Loading channels are used to fill used spectrum and ensure
data-carrying channels operate with optimum power levels.
Channelized amplified spontaneous emission (ASE) noise, or multiple
ASE idler channels, are often used as loading channels. When new
data carrying channels are added these ASE loading channels are
gradually removed.
[0012] Existing solutions for recovering channel performance in the
event of a cable cut in an optical network using an OADM-BU uses
ASE idler channels to adjust and recover remaining channels.
However, this has several limitations, such as requiring all
digital line segments use the same modulation format causing some
digital line segments to operate with excess margins, thereby
decreasing spectral efficiency. Additionally, as ASE idler channels
are replaced with data-carrying channels, adjustment of the
remaining ASE idler channels will not be adequate to equalize power
across multiple channels, or the band.
[0013] Thus, there is a need to reduce nonlinear penalties due to a
failed branch in the remaining channels. It is to such a system and
method that the present disclosure is directed.
SUMMARY OF THE DISCLOSURE
[0014] The problem of reducing nonlinear penalties due to the
failed branch in the remaining channels is addressed by an
apparatus or method including a continuous wave idler and an
optical coupler that provide an optical signal having a power
greater than optical channels carrying data, and positioned at a
cross-over point between two spectral bands, with each band
encompassing multiple optical channels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate one or more
implementations described herein and, together with the
description, explain these implementations. The drawings are not
intended to be drawn to scale, and certain features and certain
views of the figures may be shown exaggerated, to scale or in
schematic in the interest of clarity and conciseness. Not every
component may be labeled in every drawing. Like reference numerals
in the figures may represent and refer to the same or similar
element or function. In the drawings:
[0016] FIG. 1 illustrates an optical communication system
consistent with aspects of the present disclosure.
[0017] FIG. 2 illustrates an optical link consistent with aspects
of the present disclosure.
[0018] FIG. 3 illustrates a wavelength plan for two superchannels
separated by a guard-band and transmitted in an optical
communication system consistent with aspects of the present
disclosure.
[0019] FIG. 3A Illustrates a block diagram of a cable landing
station constructed in accordance with the present disclosure.
[0020] FIG. 4 illustrates a block diagram of a transmitter module
constructed in accordance with the present disclosure consistent
with aspects of the present disclosure.
[0021] FIG. 4A is a block diagram of a coherent transmitter
constructed in accordance with the present disclosure.
[0022] FIG. 4B is a block diagram of a coherent receiver
constructed in accordance with the present disclosure.
[0023] FIG. 5 illustrates a block diagram of an exemplary branching
unit within the optical link of FIG. 2.
[0024] FIG. 6 is a block diagram of a computer system constructed
in accordance with the present disclosure.
[0025] FIG. 7 is a flow chart of fast system optimization process
performed by a processor in accordance with the present
disclosure.
[0026] FIG. 8 is a block diagram of an exemplary embodiment of the
subsea communication system of FIG. 2 having a plurality of band
pass profiles illustrated for various locations within the subsea
communication system.
DETAILED DESCRIPTION
[0027] The following detailed description refers to the
accompanying drawings. The same reference numbers in different
drawings may identify the same or similar elements.
[0028] The problems of nonlinear penalties discussed above are
solved by an apparatus including a continuous wave idler and an
optical coupler that provide an optical signal having a power
greater than optical channels carrying data, and positioned at a
cross-over point between two spectral bands, with each band
encompassing multiple optical channels.
[0029] If used throughout the description and the drawings, the
following terms have the following meanings unless otherwise
stated:
[0030] Band: The complete optical spectrum carried on the optical
fiber. Depending on the fiber used and the supported spectrum which
can be carried over long distances with the current technology,
relevant examples of the same are: C-Band/L-Band/Extended-C-Band.
As used herein, the C-Band is a band of light having a wavelength
between about 1528.6 nm and about 1566.9 nm. The L-Band is a band
of light having a wavelength between about 1569.2 nm and about
1609.6 nm. Because the wavelength of the C-Band is smaller than the
wavelength of the L-Band, the wavelength of the C-Band may be
described as a short, or a shorter, wavelength relative to the
L-Band. Similarly, because the wavelength of the L-Band is larger
than the wavelength of the C-Band, the wavelength of the L-Band may
be described as a long, or a longer, wavelength relative to the
C-Band.
[0031] LS (Light source): A card where the digital transport client
is modulate/de-modulated to/from an optical channel. This is the
place where the optical channel originates/terminates.
[0032] OA (Optical Amplifier) stands for a band control gain
element generally EDFA or RAMAN based.
[0033] PD (Photo-Diode) stands for a device which can measure the
power levels in the complete band.
[0034] SCH (Super Channel/Optical Channel) stands for a group of
wavelengths sufficiently spaced so as not to cause any interference
among the group of wavelengths. The group of wavelengths may be
sourced from a single light source and managed as a single grouped
entity for routing and signaling in an optical network. Each
optical channel included in a super-channel may be associated with
a particular optical wavelength (or set of optical wavelengths).
The multiple optical channels may be combined to create a
super-channel using wavelength division multiplexing and then
routed together through the optical network. For example, the
multiple optical channels may be combined using dense wavelength
division multiplexing, in which channel-to-channel spacing may be
less than one nanometer. In some implementations, each optical
channel may be modulated to carry an optical signal.
[0035] WSS (Wavelength Selective Switch) is a component used in
optical communications networks to route (switch) optical signals
between optical fibers on a per-slice basis. Generally power level
controls can also be done by the WSS by specifying an attenuation
level on a reconfigurable pass-band filter. A wavelength Selective
Switch is a programmable device having source and destination fiber
ports where the source and destination fiber ports and associated
attenuation can be specified for a pass-band.
[0036] Slice stands for an N GHz (N=12.5, 6.25, 3.125) spaced
frequency band of the whole of the optical spectrum each such
constituent band is called a slice. A slice is the spectral
resolution at which the wavelength selective switch operates to
build the filter response. A channel (or super-channel) pass-band
is composed of a set of contiguous slices.
[0037] Before explaining at least one embodiment of the disclosure
in detail, it is to be understood that the disclosure is not
limited in its application to the details of construction,
experiments, exemplary data, and/or the arrangement of the
components set forth in the following description or illustrated in
the drawings unless otherwise noted.
[0038] The disclosure is capable of other embodiments or of being
practiced or carried out in various ways. Also, it is to be
understood that the phraseology and terminology employed herein is
for purposes of description and should not be regarded as
limiting.
[0039] As used in the description herein, the terms "comprises,"
"comprising," "includes," "including," "has," "having," or any
other variations thereof, are intended to cover a non-exclusive
inclusion. For example, unless otherwise noted, a process, method,
article, or apparatus that comprises a list of elements is not
necessarily limited to only those elements but may also include
other elements not expressly listed or inherent to such process,
method, article, or apparatus.
[0040] Further, unless expressly stated to the contrary, "or"
refers to an inclusive and not to an exclusive "or". For example, a
condition A or B is satisfied by one of the following: A is true
(or present) and B is false (or not present), A is false (or not
present) and B is true (or present), and both A and B are true (or
present).
[0041] In addition, use of the "a" or "an" are employed to describe
elements and components of the embodiments herein. This is done
merely for convenience and to give a general sense of the inventive
concept. This description should be read to include one or more,
and the singular also includes the plural unless it is obvious that
it is meant otherwise. Further, use of the term "plurality" is
meant to convey "more than one" unless expressly stated to the
contrary.
[0042] As used herein, qualifiers like "substantially," "about,"
"approximately," and combinations and variations thereof, are
intended to include not only the exact amount or value that they
qualify, but also some slight deviations therefrom, which may be
due to computing tolerances, computing error, manufacturing
tolerances, measurement error, wear and tear, stresses exerted on
various parts, and combinations thereof, for example.
[0043] As used herein, any reference to "one embodiment," "an
embodiment," "some embodiments," "one example," "for example," or
"an example" means that a particular element, feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment and may be used in conjunction
with other embodiments. The appearance of the phrase "in some
embodiments" or "one example" in various places in the
specification is not necessarily all referring to the same
embodiment, for example.
[0044] The use of ordinal number terminology (i.e., "first",
"second", "third", "fourth", etc.) is solely for the purpose of
differentiating between two or more items and, unless explicitly
stated otherwise, is not meant to imply any sequence or order of
importance to one item over another.
[0045] The use of the term "at least one" or "one or more" will be
understood to include one as well as any quantity more than one. In
addition, the use of the phrase "at least one of X, Y, and Z" will
be understood to include X alone, Y alone, and Z alone, as well as
any combination of X, Y, and Z.
[0046] Circuitry, as used herein, may be analog and/or digital
components, or one or more suitably programmed processors (e.g.,
microprocessors) and associated hardware and software, or hardwired
logic. Also, "components" may perform one or more functions. The
term "component," may include hardware, such as a processor (e.g.,
microprocessor), an application specific integrated circuit (ASIC),
a field programmable gate array (FPGA), a combination of hardware
and software, and/or the like. The term "processor" as used herein
means a single processor or multiple processors working
independently or together to collectively perform a task.
[0047] Software may include one or more computer readable
instructions that when executed by one or more components cause the
component to perform a specified function. It should be understood
that the algorithms described herein may be stored on one or more
non-transitory computer readable medium. Exemplary non-transitory
computer readable mediums may include random access memory, read
only memory, flash memory, and/or the like. Such non-transitory
computer readable mediums may be electrically based, optically
based, magnetically based, and/or the like. Further, the messages
described herein may be generated by the components and result in
various physical transformations.
[0048] The generation of laser beams for use as optical data
carrier signals is explained, for example, in U.S. Pat. No.
8,155,531, entitled "Tunable Photonic Integrated Circuits", issued
Apr. 10, 2012, and U.S. Pat. No. 8,639,118, entitled "Wavelength
division multiplexed optical communication system having variable
channel spacings and different modulation formats," issued Jan. 28,
2014, which are hereby fully incorporated in their entirety herein
by reference.
[0049] An Optical Cross-Connect is a device for switching at least
a portion of a spectrum of light in an optical signal received on
an input optical port to any (one or more) output optical port. An
optical cross-connect can be configured on ROADM network elements,
with a built-in wavelength selective switch (WSS) component that is
used to route an optical signal in any of the fiber degree or
direction. For example, an exemplary optical cross connect can be
formed within a wavelength selective switch by opening a specified
channel, or specific spectrum of light on an input port of the
wavelength selective switch. Configuring or pre-configuring an
optical cross-connect may be accomplished by providing instructions
to a device to cause the device to switch at least a portion of a
spectrum of light in an optical signal received on an input port to
any (one or more) output optical port.
[0050] A digital line segment (DLS) is a possible communication
link between any two nodes in the optical network. For example, in
an optical network with Node A, Node B, and Node C interconnected
to each other, three DLS are formed: a first DLS between Node A and
Node B, a second DLS between Node A and Node C, and a third DLS
between Node B and Node C.
[0051] Amplified spontaneous emission (ASE) is light produced by
spontaneous emission that has been optically amplified by the
process of stimulated emission in a gain medium. ASE is an
incoherent effect of pumping a laser gain medium to produce a
transmission signal. If an amplified spontaneous emission power
level is too high relative to the transmission signal power level,
the transmission signal in the fiber optic cable will be unreadable
due to the low signal to noise ratio.
[0052] Spectral loading, or channel loading, is the addition of one
or more channel to a specific spectrum of light described by the
light's wavelength in an optical signal. When all channels within a
specific spectrum are being utilized, the specific spectrum is
described as fully loaded. A grouping of one or more channel may be
called a media channel. Spectral loading may also be described as
the addition of one or more media channel to a specific spectrum of
light described by the light's wavelength to be supplied onto the
optical fiber as the optical signal.
[0053] Line amplifier dynamics (i.e., EDFA, Raman) and interactions
in optical fiber (Signal-Signal Raman gain, etc.) are likely to
change based on spectral loading changes (such as number of optical
channels in the fiber optic cable and/or the wavelength of the
present optical channels, etc.) In other words, amplifier and
optical fiber dynamics differ when the wavelength of the optical
signals, or optical carriers, for existing optical channels change
and this causes changes in the tilt.
[0054] Tilt, also called linear power tilt, is the linear change in
power with wavelength over the signal spectrum. Due to Raman gain,
short wavelength signals provide Raman gain for longer wavelengths.
SRS Tilt strength, that is the difference in gain between the
longest wavelength and the shortest wavelength of the signals,
depends on the transmission signal power, spectral loading, fiber
type, and fiber length.
[0055] Referring now to the drawings, and in particular to FIG. 1,
an exemplary embodiment of subsea communication system 10
constructed in accordance with the present disclosure is
illustrated therein. Subsea communication system 10 typically
includes at least two cable landing stations 14a, 14b on land 18
and at least one optical fiber pair 22 extending underwater, such
as on the ocean floor 26, between the two cable landing stations
14a, 14b. The subsea communication system 10 may also include one
or more in-line node 30 between the cable landing stations 14a,
14b, which may, in part, boost signals in the optical fiber pair
22.
[0056] Optical signals are preferably grouped according to a
plurality of superchannels SC1, SC2, for example, as described with
respect to FIG. 3 below. Each cable landing station 14a-n
preferably uses the exemplary systems and methods discussed below
to transmit and receive carriers, such as superchannels, SC1, SC2,
in the subsea communication system 10.
[0057] In one embodiment, the cable landing stations 14a, 14b also
provide transmission between the optical fiber pair 22 and at least
one terrestrial system 34.
[0058] In one embodiment, the optical fiber pair 22 is one or more
slope-matched cable, however, in another embodiment, the optical
fiber pair 22 is a dispersion compensated fiber having a
zero-dispersion window. The optical fiber pair 22 may include a
first fiber optic cable operable to carry a first optical signal in
a first direction and a second fiber optic cable operable to carry
a second optical signal in a second direction. In one embodiment,
the optical fiber pair 22 is an optical fiber submarine cable
pair.
[0059] In one embodiment, the in-line node 30 may be a repeater or
an in-line amplifier. In one embodiment, the in-line node 30 is a
"repeater" that receives, amplifies, and transmits the optical
signals, thereby increasing a transmission range of the optical
signals. The in-line node 30 as a repeater may operate at a maximum
output power. Output power may be set such that, when the optical
signal is fully loaded, the optical signal is operating at optimum
power. Not all subsea communication systems 10 utilize in-line
node(s) 30 and the present disclosure may apply to both repeater
and repeaterless systems. In one embodiment, if the optical signal
is not fully loaded, the remaining channels in the optical signal
will operate with a higher power.
[0060] Subsea communication system 10 typically utilizes Wavelength
Division Multiplexing (WDM) such as Dense Wavelength Division
Multiplexing (DWDM). Dense Wavelength Division Multiplexing
multiplexes multiple optical signals, such as Optical Channel
signals or Super-Channel signals, onto a single optical fiber by
using different laser light wavelengths.
[0061] In subsea communication system 10, one or more data channel
may be transmitted using the optical signal 38 through the optical
fiber pair 22. As previously described, the subsea communication
system 10 is in constant power in order to transmit for long
distances with low noise. To be able to operate through the subsea
communication system 10 at a lower power than the constant power,
one or more idler signal 42 in one or more idler channel may also
be transmitted. The idler channel(s) are transmitted at different
frequencies than the one or more data channel. The idler channel
"soaks up" the unwanted power not used by the one or more data
channel so that each data channel may operate at the correct
power.
[0062] Referring now to FIG. 2, shown therein is a function diagram
of an exemplary embodiment of the subsea communication system 10
shown in FIG. 1 and constructed in accordance with the present
disclosure. The subsea communication system 10 generally comprises
the first cable landing station 14a and the second cable landing
station 14b optically coupled by optical trunk 50 formed of the
optical fiber pair 22. Intermediate the first cable landing station
14 and the second cable landing station 14b on the optical trunk 50
is one or more branching unit 54, illustrated as first branching
unit 54a and second branching unit 54b, shown in FIG. 5 and
described in more detail below. The first branching unit 54a
receives optical signals from the optical trunk 50, filters out a
first branching optical signal from the optical signals, and
directs the first branching optical signal along a first optical
branch 58a. The first branching unit 54a also receives optical
signals from the first optical branch 58a, and supplies the optical
signals onto the optical trunk 50. The second branching unit 54b
receives optical signals from the optical trunk 50, filters out a
second branching optical signal from the optical signals, and
directs the second branching optical signal along a second optical
branch 58b. The second branching unit 54a also receives optical
signals from the second optical branch 58b and supplies the optical
signals onto the optical trunk 50. In one embodiment, each of the
optical trunk 50, the first optical branch 58a, and the second
optical branch 58b is an optical fiber pair 22 operable to carry an
optical signal. In one embodiment, the optical trunk 50 is fully
loaded, that is, the optical trunk 50 is loaded with the full
spectrum, while each optical branch 58 is loaded with the spectral
components, such as channels or superchannels, added and dropped
towards a particular cable terminal station 14c or 14d connected to
the optical trunk 50 by the optical branch 58a or 58b.
[0063] In one embodiment, each branching unit 54 of the subsea
communication system 10 is either a fixed optical add/drop
multiplexer (FOADM) or a reconfigurable optical add drop
multiplexer (ROADM). Each branching unit 54 can add/drop one or
more channel or superchannel onto or from an optical branch 58a-n
for communication with a cable landing station 14n not directly
connected to the optical trunk 50. Each branching unit 54 may be
arranged such that every cable landing station 14 is connected via
a digital line segment (DLS) to another cable landing station 14 by
partitioning the spectrum of the optical fiber pair 22 into one or
more superchannel. For example, as shown in FIG. 2, a plurality of
DLS-n may be formed such that DLS-1 is a digital line segment
between the first cable landing station 14a and the second cable
landing station 14b, DLS-2 is a digital line segment between the
first cable landing station 14a and the third cable landing station
14c, DLS-3 is a digital line segment between the first cable
landing station 14a and the fourth cable landing station 14d, DLS-4
is a digital line segment between the second cable landing station
14b and the third cable landing station 14c, DLS-5 is a digital
line segment between the second cable landing station 14b and the
fourth cable landing station 14d, and DLS-6 is a digital line
segment between the third cable landing station 14c and the fourth
cable landing station 14d. Each DLS-n may be considered a
bi-directional, logical path through the subsea communication
system 10 between two specific cable landing stations 14.
[0064] In one embodiment, the subsea communication system 10
employs modulation formats such as BPSK, QPSK, 8-QAM, and 16-QAM,
which are highly susceptible to nonlinear distortions when channel
power levels increase. In the event of a cable failure, such as a
cut cable or a cable fault, part of the optical power in the
spectrum will be lost, raising the power of the remaining parts of
the spectrum. The increase in power could potentially cause some or
all of the remaining channels to operate in degraded conditions.
While the modulation formats described include BPSK, QPSK, 8-QAM,
and 16-QAM, the subsea communication system 10 is not limited to
these modulation formats. For example, the subsea communication
system 10 may use 32-QAM, 64-QAM or a higher-level quadrature
amplitude modulation format, or a different modulation format
entirely. The systems and methods of the present disclosure are not
dependent on the modulation format used.
[0065] Referring now to FIG. 3, shown therein is a diagram of an
exemplary embodiment of a wavelength channel plan 100 with the
presence of a guard-band 104. The optical signals or carriers,
e.g., one or more data channel, included in each group or band are
centered around a wavelength or frequency specified by the
International Telecommunications Union (ITU) standard wavelength or
frequency grid. Alternatively, each of the optical carriers is
provided according to a unique nonstandard grid that is optimized
for a specific embodiment. For example, as shown in FIG. 3, a
plurality of optical signals or carriers .lamda.1,1 to .lamda.1,10
are grouped or banded together to form a superchannel SC1, and a
plurality of optical signals or carriers .lamda.2,1 to .lamda.2,10
are grouped or banded together to form a superchannel SC2. As
shown, the plurality of optical (sub-wavelength) channels
.lamda.1,1 to .lamda.1,10 and .lamda.2,1 to .lamda.2,10 are closely
spaced so as to optimize the occupied bandwidth BW1 and BW2 of the
superchannels SC1 and SC2, respectively. Each optical channel
.lamda.1,1 to .lamda.1,10 and .lamda.2,1 to .lamda.2,10 of SC1 and
SC2, respectively, may be considered a sub-wavelength channel
banded around a center wavelength .lamda.1 and .lamda.2 identifying
the superchannels SC1 and SC2, respectively. As described above,
each of the superchannels SC1 and SC2 may be multiplexed or
independently routed through the subsea communication system 10
shown in FIG. 1 or FIG. 2. In one embodiment, the guard-band 104 is
between about 100 GHz-200 GHz wide. In another embodiment, the
guard-band 104 is approximately the same width of each of the one
or more channels in the superchannel SC1 and/or SC2. In one
embodiment, each of superchannel SC1 and SC2 is associated with one
DLS-n. Each superchannel SC1 and SC2 may be described in relation
to each other, such that the superchannel SC2 may be described as
the next superchannel in the spectrum in relation to the
superchannel SC1 and the superchannel SC1 may be described as the
previous superchannel in the spectrum in relation to the
superchannel SC2.
[0066] In an exemplary embodiment, the plurality of channels
.lamda.1,1 to .lamda.1,10 and .lamda.2,1 to .lamda.2,10 are
periodically spaced from each other by a fixed frequency spacing
according to a specific unique frequency grid. In other words, as
shown in FIG. 3, a corresponding frequency spacing between the
center wavelengths .lamda.1,6 and .lamda.1,7, shown as .DELTA.f, is
the same for each of the other carriers within a particular
superchannel SC1, SC2. Thus, each of the carriers are said to be
periodically spaced from each other by .DELTA.f. Because a transmit
node, such as the cable landing station 14a, can produce a
plurality of superchannels .lamda.1 to .lamda.n, in order to
utilize common optical components for each superchannel, the
channels for each superchannel utilize the same fixed frequency
spacing .DELTA.f as shown in FIG. 3. In one embodiment, where each
of the channels within a particular superchannel do not utilize the
same modulation format, the frequency spacing .DELTA.f between one
or more channel may be different.
[0067] Also shown in FIG. 3 is a CW channel 108, and an ASE channel
112, discussed in more detail below. In one embodiment, the CW
channel 108 has a CW power that is greater than the power of any of
the optical signals or carriers forming the superchannel SC1 or the
superchannel SC2 and has a bandwidth that is less than the
bandwidth of each of the one or more data channel. In one
embodiment, the bandwidth of the CW channel 108 is between about 10
Mhz and about 25 GHz. In one embodiment, the CW channel 108 is
within the guard-band 104, and spaced spectrally from an adjacent
carrier within a range of 50-100 GHz. In one embodiment, the ASE
channel 112 has an ASE power that is lesser than the power of any
of the optical signals or carriers forming the superchannel of
which it is a member, such as the superchannel SC1 in FIG. 3. The
ASE channel 112 further has a bandwidth approximately equal to the
bandwidth of the one or more channel forming the superchannel SC1.
In one embodiment, the ASE channel 112 may be considered a
sub-wavelength channel banded around a center wavelength .lamda.1
and .lamda.2 identifying the superchannels SC1 and SC2,
respectively, and is periodically spaced from the plurality of
optical signals or carriers carrying data by a fixed frequency
spacing according to the specific unique frequency grid, that is,
the ASE channel 112 may utilize the same fixed frequency spacing
.DELTA.f. In one embodiment, more than one CW channel 108 may be
included in the spectrum.
[0068] It is understood that the characteristics of optical
components can vary with respect to temperature and other
environmental conditions. Thus, throughout the disclosure where a
"fixed" frequency or wavelength spacing is described, such fixed
spacing is a theoretical or ideal fixed spacing that is desired,
but may not be achieved exactly due to environmental conditions.
Thus, any substantially similar spacing, frequency or wavelength
within expected optical component variations may correspond to the
ideal fixed spacing described.
[0069] Because of the non-ideal response of optical components,
such as a reconfigurable filter of a wavelength selective switch,
for example, filtered channels shows a roll-off effect that needs
to be accounted for in a wavelength channel plan. The common way to
deal with this non-ideal filtering effect is by allocating enough
spectrum in between channels (or superchannels) so that the
roll-off can be accommodated for. In one embodiment, the guard-band
104 is generally un-occupied spectral spacing between
superchannels. Conventionally, a wavelength selective switch will
pass the guard-band 104 in an open state.
[0070] Referring now to FIG. 3A, shown therein is a block diagram
of an exemplary embodiment of a cable landing station 14
constructed in accordance with the present disclosure. The cable
landing station 14 generally includes a plurality of submarine line
terminating equipment modules 80a-n (SLTE module 80a-n) Each SLTE
module 80a-n includes at least a transmitter module 84, shown in
FIG. 4 and described in more detail below, and a receiver module
88. As shown in FIG. 3A, an SLTE module 80a includes a transmitter
module 84a and a receiver module 88a. Each SLTE module 80a-n may be
in communication with a processor 92, which is in communication
with a memory 96. The memory 96 is a non-transitory computer
readable medium operable to store computer readable instructions
that when executed by the processor 92 causes the processor to
execute one or more operation. In one embodiment, the processor 92
may further be coupled to a communication link 98.
[0071] Referring now to FIG. 4, shown therein is a block diagram of
an exemplary embodiment of the transmitter module 84a of the SLTE
module 80 of FIG. 3A, constructed in accordance with the present
disclosure. In one embodiment, the transmitter module 84 generally
includes a submarine line terminating equipment component 120, a
transponder 124, an ASE idler 128, a wavelength selective switch
(WSS) 132, a CW idler 136, a first coupler 140, a second coupler
144, and an amplifier 148. In one embodiment, the SLTE module 80
does not include the existing component 120.
[0072] In one embodiment, the submarine line terminating equipment
component 120 includes transmission equipment, which may supply one
or more channel. The submarine line terminating equipment component
120 further supplies one or more ASE idler channel.
[0073] In one embodiment, the transponder 124 is operable to
receive one or more data or information stream, and, in response to
a respective one of these data streams, may output one or more
optical data channel, or a superchannel, to the WSS 132.
[0074] In one embodiment, the ASE idler 128 generates a broadband
ASE signal having an ASE power. The ASE power may be similar to or
lower than a power of the plurality of channels. The ASE signal is
optically connected to the WSS 132. The WSS 132 multiplexes a
plurality of channels and superchannels together. In order to keep
the plurality of channels and superchannels at an optimum
operational power, an ASE channel, such as the ASE channel 112
shown in FIG. 3, is shaped by the WSS 132 from the ASE signal such
that the ASE channel is located at one or more optical channel
.lamda.1,1 to .lamda.1,10 and .lamda.2,1 to .lamda.2,10 different
from any of the one or more data carrying optical channel, or a
superchannel, output by the transponder 124. In one embodiment, the
WSS 132 is a multiplexer/demultiplexer that is capable of adding or
dropping and adjusting one or more channel, including both data
channels and ASE channels, remotely. The WSS 132 may be in
communication with the processor 92 and operable to add/drop or
adjust the one or more channel based on an instruction from the
processor 92.
[0075] In one embodiment, the transmitter module 84 includes the CW
idler 136. The CW idler 136 may be a depolarized continuous wave
idler to provide a CW channel, such as the CW channel 108 shown in
FIG. 3, to inject optical power into the guard-band 80 of the
spectrum to replace power lost due to one or more lost data
carrying channel, or one or more ASE channel. The CW idler 136 is
optically coupled to supply the CW channel to the first coupler
140. In one embodiment, the CW idler 136 is an un-modulated or low
modulated laser used to soak optical power but does not carry data
traffic. In one embodiment, the CW idler 136 is an orthogonally
polarized continuous wave laser that generates a discrete CW
channel having a wavelength spectrum sized and configured to be
placed at an edge of a bandwidth adjacent to a failed superchannel.
In one embodiment, the CW channel 108 may be entirely within at
least one of the guard-band(s) 80. For example, referring to FIG.
3, if a cable failure causes loss of the superchannel SC1, the CW
idler 136 may generate the CW channel 108 at a lower-frequency end
of the bandwidth Bw2 adjacent failed superchannel SC1. In one
embodiment, more than one CW channel 108 may be generated and
inserted into the spectrum. In one embodiment, one or more CW
channel 108 may be generated by a different CW idler 136.
[0076] In one embodiment, each CW channel can compensate for power
lost due to a loss of multiple channels, such as up to 16 channels.
In one embodiment, the transmitter module 84 includes more than one
CW idler 136 where each CW idler 136 is optically coupled to the
first coupler 140. In one embodiment, the transmitter module 84
includes up to four (4) CW idlers 136 optically coupled to the
first coupler 140 for each optical fiber pair 22. In one
embodiment, the CW idler 136 is activated, e.g., in response to a
communication from the processor 92, in the event of a cable cut to
supply optical power into the spectrum to protect the affected
section of the optical fiber pair 22 and the rest of the spectrum.
Each CW idler 136 may supply optical power into the spectrum at a
different frequency and with a different bandwidth. In one
embodiment, the first coupler 140 couples the one or more channel
or superchannels from the WSS 132 with the CW channel into the
spectrum. In other words, the first coupler 140 combines the one or
more channel or superchannel with the one or more CW channel.
[0077] In one embodiment, the second coupler 144 combines the one
or more channel from the submarine line terminating equipment
component 120 with the spectrum having the one or more channel or
superchannel from the WSS 132 and the CW channel.
[0078] In one embodiment, the transmitter module 84 further
includes the amplifier 148 amplifying the combined one or more
channel or superchannel from the submarine line terminating
equipment component 120, the one or more channel or superchannel
from the transponder 124, and the CW channel. In one embodiment,
the amplifier 148 is an erbium doped fiber amplifier with a
configurable fixed output power.
[0079] In one embodiment, the first coupler 140 and the second
coupler 144 are the same coupler such that the submarine line
terminating equipment component 120 is coupled with the one or more
channel or superchannel from the WSS 132 and the CW channel at the
first coupler 140. In another embodiment, the second coupler 144 is
a 2.times.2 coupler, that is, the second coupler 144 combines
sub-optical channels from two separate inputs into two separate
aggregate outputs. The second coupler 144 may also be a 50/50
coupler or a 3 dB coupler.
[0080] It will be understood that the transponder 124 may be
implemented in a variety of ways. For example, shown in FIG. 4A is
a block diagram of an exemplary implementation of the transponder
124. The transponder 124 may comprise one or more transmitter
processor circuit 164, one or more laser 165, one or more modulator
166, one or more semiconductor optical amplifier 167, and/or other
components (not shown).
[0081] The transmitter processor circuit 164 may have one or more
transmitter digital signal processor (DSP) 168, Transmitter Forward
Error Correction (FEC) circuitry 169, Symbol Map circuitry 170,
transmitter perturbative pre-compensation circuitry 171, and
digital-to-analogue converters (DAC) 172. The transmitter processor
circuit 164 may be located in any one or more components of the
transponder 124, or separate from the components, and/or in any
location(s) among the components. The transmitter processor circuit
164 may be in the form of one or more Application Specific
Integrated Circuit (ASIC), which may contain one or more module
and/or custom module.
[0082] Processed electrical outputs from the transmitter processor
circuit 164 may be supplied to the modulator 166 for encoding data
into optical signals generated and supplied to the modulator 166
from the laser 165. The semiconductor optical amplifier 167
receives, amplifies and transmits the optical signal including
encoded data in the spectrum. Processed electrical outputs from the
transmitter processor circuit 164 may be supplied to other
circuitry in the transmitter processor circuit 164, for example,
clock and data modification circuitry. The laser 165, modulator
166, and/or semiconductor optical amplifier 167 may be coupled with
a tuning element (e.g., a heater) (not shown) that can be used to
tune the wavelength of an optical signal channel output by the
laser 165, modulator 166, or semiconductor optical amplifier 167.
In some implementations, a single laser 165 may be shared by
multiple transponder 124.
[0083] Other possible components in the transponder 124 may include
filters, circuit blocks, memory, such as non-transitory memory
storing processor executable instructions, additional modulators,
splitters, couplers, multiplexers, etc., as is well known in the
art. The components may be combined, used, or not used, in multiple
combinations or orders. Optical transmitters are further described
in U.S. Patent Publication No. 2012/0082453, the content of which
is hereby incorporated by reference in its entirety herein.
[0084] Referring now to FIG. 4B, shown therein is a block diagram
of an exemplary embodiment of the receiver module 88 consistent
with the present disclosure. Receiver module 88 may comprise one or
more local oscillator 174, a polarization and phase diversity
hybrid circuit 175 receiving the one or more channel on the
spectrum and the input from the local oscillator 174, one or more
balanced photodiode 176 that produces electrical signals
representative of the one or more channel on the spectrum, and one
or more receiver processor circuit 177. Other possible components
in the receiver module 88 may include filters, circuit blocks,
memory, such as non-transitory memory storing processor executable
instructions, additional modulators, splitters, couplers,
multiplexers, etc., as is well known in the art. The components may
be combined, used, or not used, in multiple combinations or orders.
The receiver module 88 may be implemented in other ways, as is well
known in the art. Exemplary receiver module 88 are further
described in U.S. patent application Ser. No. 12/052,541, titled
"Coherent Optical Receiver".
[0085] The one or more receiver processor circuit 177, may comprise
one or more analog-to-digital converter (ADC) 178 receiving the
electrical signals from the balanced photodiodes 176, one or more
receiver digital signal processor (DSP) 179, receiver perturbative
post-compensation circuitry 180, and receiver forward error
correction (FEC) circuitry 181. The receiver FEC circuitry 181 may
apply corrections to the data, as is well known in the art. The one
or more receiver processor circuit 177 and/or the one or more
receiver DSP 179 may be located on one or more component of the
receiver module 88 or separately from the components, and/or in any
location(s) among the components. The receiver processor circuit
177 may be in the form of an Application Specific Integrated
Circuit (ASIC), which may contain one or more module and/or custom
module. In one embodiment, the receiver DSP 179 may include, or be
in communication with, one or more processor 182 and one or more
memory 183 storing processor readable instructions, such as
software, or may be in communication with the processor 92 and the
memory 96.
[0086] The one or more receiver DSP 179 receives and processes the
electrical signals with multi-input-multiple-output (MIMO)
circuitry, as described, for example, in U.S. Pat. No. 8,014,686,
titled "Polarization demultiplexing optical receiver using
polarization oversampling and electronic polarization tracking".
Processed electrical outputs from receiver DSP 179 may be supplied
to other circuitry in the receiver processor circuit 177, such as
the receiver perturbative post-compensation circuitry 180 and the
receiver FEC circuitry 181.
[0087] Various components of the receiver module 88 may be provided
or integrated, in one example, on a common substrate. Further
integration is achieved by incorporating various optical
demultiplexer designs that are relatively compact and conserve
space on the surface of the substrate.
[0088] In use, the one or more channel of the spectrum may be
subjected to optical non-linear effects between the transponder 124
and the receiver module 88 such that the spectrum received does not
accurately convey carried data in the form that the spectrum was
transmitted. The impact of optical nonlinear effects can be
partially mitigated by applying perturbative distortion algorithms
using one or more of the transmitter perturbative pre-compensation
circuitry 171 and the receiver perturbative post-compensation
circuitry 180. The amount of perturbation may be calculated using
coefficients in algorithms and known or recovered transmitted data.
The coefficients may be calculated, in accordance with U.S. Pat.
No. 9,154,258 entitled "Subsea Optical Communication System Dual
Polarization Idler" herein incorporated by reference in its
entirety, by use of analysis of one or more incoming channel at the
receiver module 88.
[0089] Referring now to FIG. 5, shown therein is a block diagram of
an exemplary embodiment of the branching unit 54. The branching
unit 54 generally includes at least two power splitters 150,
illustrated as power splitter 150a and power splitter 150b, at
least two branching couplers 154, illustrated as branching coupler
154a and branching coupler 154b, at least two ASE filters 158,
illustrated as ASE filter 158a and ASE filter 158b, and at least
two notch filters 162, illustrated as notch filter 162a and notch
filter 162b. For simplicity, the branching unit 54 will be
described in relation to the first direction. In one embodiment,
the branching unit 54 filters one or more particular channel from
the spectrum on the optical trunk 50 and directs the one or more
particular channel to a cable landing station 14 on a particular
optical branch 58. The notch filters 162 are operable to filter one
or more channel from the spectrum into one or more drop data
channel, which is filtered out of the spectrum, and one or more
express data channel, that continues through the notch filter 162.
A cross-over point 370 (see FIG. 8) may be used to describe a
frequency, or range of frequencies, between the one or more drop
data channel and the one or more express data channel. In one
embodiment, the notch filters 162 and the ASE filters 158 are
configurable to filter out each permutation of digital line segment
that can pass through the branching unit 72. In one embodiment, one
or more notch filter 162 and/or one or more ASE filter 158 is a
WSS. In one embodiment, each filter 158, 162 includes a small
guard-band, rendering a redundant region between filters where one
or more channel and ASE channel cannot be placed without being
filtered out. In one embodiment, each filter 158,162 is either a
fixed or reconfigurable filter. By generating and inserting one or
more CW channel 108 into the guard-band adjacent a failed
superchannel, each CW channel may naturally decay in the subsea
communication system 10 having one or more optical branch 58. In
one embodiment, the CW channel will only decay if it is placed in a
guard-band adjacent to the failed superchannel.
[0090] Generally, in operation, the power splitter 150a receives
the spectrum, having one or more channel, traveling in the first
direction along the optical trunk 50 and splits the spectrum into
two components, both of which include all channels on the spectrum.
The first component is optically coupled to the first optical
branch 58a such that the first component is carried to the cable
landing station 14c and the second component continues to the notch
filter 162a. The cable landing station 14c receives the first
component and sends one or more data-channel and, in some
instances, one or more ASE channel, in a second spectrum, via the
optical branch 58a, to the ASE filter 158a. The ASE filter 158a
filters out the one or more ASE channel in the second spectrum such
that the one or more data-channel is transmitted to the branching
coupler 154a and the notch filter 162a operates to filter "drop"
channels from the spectrum, that is, the notch filter 162a filters
one or more channel from the spectrum that is intended for the
cable landing station 14c, and transmits the remaining spectrum to
the branching coupler 154a. The branching coupler 154a couples the
remaining spectrum and the second spectrum such that the spectrum
continues along the optical trunk 50.
[0091] In one embodiment, the full spectrum of the first component
is dropped at the cable landing station 14c such that the cable
landing station 14c just adds one or more data-channel originating
at the cable landing station 14c along with one or more ASE channel
as filler to ensure the spectrum is at an operable optical power.
In other words, in one embodiment, if DLS-1 describes data-traffic
from the cable landing station 14a to the cable landing station
14b, DLS-2 describes data-traffic from the cable landing station
14a to the cable landing station 14c, and DLS-3 describes
data-traffic from the cable landing station 14c to the cable
landing station 14b, then the branching unit 72 filters out DLS-2
data-traffic, adds DLS-3 data-traffic, and passes along DLS-1
data-traffic.
[0092] Referring now to FIG. 6, shown therein is a diagram of an
exemplary embodiment of one or more computer system 200. In one
embodiment, as shown in FIG. 6, a system optimization process 300,
shown below and in FIG. 7, is carried out on one or more computer
system 200. The computer system 200 may comprise one or more
computer processor 204, and one or more non-transitory memory 208.
In one embodiment, one or more initial values database 212 and one
or more baseline spectral database 216 are stored in the memory
208. As shown in FIG. 6, the computer processor 204 may include (or
be communicatively coupled with) one or more communication
component 220. The computer system 200 may include a network 224
enabling bidirectional communication between the computer processor
204 and the non-transitory memory 208 with a plurality of user
devices 228. The user devices 228 may communicate via the network
224 and/or may display information on a display 232. The computer
processor 204 or multiple computer processors 204 may or may not
necessarily be located in a single physical location. The user
devices 228 may enable one or more user to access to the fast
system optimization process 300.
[0093] In one embodiment, the network 224 is the Internet and the
user devices 228 interface with the computer processor 204 via the
communication component 220 using a series of web pages. It should
be noted, however, that the network 224 may be almost any type of
network and may be implemented as the World Wide Web (or Internet),
a local area network (LAN), a wide area network (WAN), a
metropolitan network, a wireless network, a cellular network, a
Global System for Mobile Communications (GSM) network, a code
division multiple access (CDMA) network, a 3G network, a 4G
network, a 5G network, a satellite network, a radio network, an
optical network, a cable network, a public switched telephone
network, an Ethernet network, combinations thereof, and/or the
like. It is conceivable that in the near future, embodiments of the
present disclosure may use more advanced networking topologies.
[0094] In one embodiment, the computer processor 204 and the
non-transitory memory 208 may be implemented with a server system
236 having multiple servers in a configuration suitable to provide
a commercial computer-based business system such as a commercial
web-site and/or data center. Additionally, it is understood that
the fast system optimization process 300 may be implemented on the
same or on a different server system 236.
[0095] Referring now to FIG. 7, shown therein is a process flow
diagram of an exemplary embodiment of the fast system optimization
process 300 generally comprising the steps of: detecting a cable
failure (step 304); setting one or more CW channel (step 308);
initialize spectral equalization (step 312); and tune one or more
CW channel power and wavelength (step 316).
[0096] In one embodiment, detecting a cable failure (step 304)
includes detecting a cut in a fiber optic cable or detecting a
cable fault. Detecting a cut in a fiber optic cable may be
performed by the processor 92 or 204 monitoring error signals, such
as an optical loss of signal, or a loss of frame. In the event of a
cable failure, the processor 204 may launch an Intelligent Power
Management Software. The Intelligent Power Management Software may
be accessed by a user via the user device 228, discussed in more
detail above. The Intelligent Power Management Software may display
one or more chart of a receive spectrum and Q for every cable
landing station 14 in a chosen direction, such as the first
direction or the second direction. The Intelligent Power Management
Software may also load a baseline measurement for the receive
spectrum. In one embodiment, the Intelligent Power Management
Software is executing on the computer system 200 and causes the
processor 204 to communicate with the processor 92 of each cable
landing station 14 such that the processor 204 can gather CLS
status information from each cable landing station 14. The CLS
status information may include an optical power across the spectrum
at the cable landing station 14 with a granularity of about 6.25
GHz. In other embodiments, the granularity may be more than or less
than 6.25 GHz. The processor 204, in communication with the
processor 92, can also control, monitor, and adjust the cable
landing station 14 and the components of the cable landing station
14, such as the WSS 132, the ASE idler 128, and the CW idler 136,
for example. In one embodiment, detecting a cable failure (step
304) includes identifying one or more failed superchannel.
[0097] In one embodiment, setting one or more CW channel (step 308)
includes the processor 204 causing the processor 92 to set one or
more CW channel to an initial wavelength and power for each
location on each optical fiber pair 22. One or more CW channel is
placed at an edge of a particular superchannel pass-band adjacent
to an affected one or more superchannel with a combined CW power
approximately equivalent to lost spectral power due to the loss of
one or more channel within the spectrum due to the cable failure.
In one embodiment, setting one or more CW channel (step 308) can be
initialized by the user via the user device 228 whereas in another
embodiment, setting one or more CW channel (step 308) is performed
by the processor 204 without any manual assistance by the user, as
described in more detail above. In one embodiment, the initial
wavelength and initial power for each location on each optical
fiber pair 22 is stored in an initial values database 212, which
may be stored in the memory 208. In one embodiment, the user is one
or more staff of a network operating center.
[0098] In one embodiment, setting one or more CW channel (step 308)
includes the processor 204 causing the processor 92 to set a CW
channel to an initial wavelength within a cross over point 370 (see
FIG. 8) adjacent to a failed superchannel. In one embodiment,
setting one or more CW channel (step 308) includes the processor
204 causing the processor 92 to set a first CW channel to an
initial wavelength approximately 50-100 GHz greater than the failed
superchannel's highest frequency and a second CW channel to an
initial wavelength approximately 50-100 GHz lesser than the failed
superchannel lowest frequency. In one embodiment, setting one or
more CW channel (step 308) includes the processor 204 causing the
processor 92 to set a first CW channel to an initial wavelength at
a lower-end of the bandwidth of a next non-failed superchannel in
the spectrum and set a second CW channel to an initial wavelength
at a higher-end of the bandwidth of a previous non-failed
superchannel in the spectrum.
[0099] In one embodiment, initializing spectral equalization (step
312) includes initializing spectral equalization at a downstream
node of the optical trunk 50, e.g., the cable landing station 14b.
During normal operations, the processor 204 may receive from the
processor 92 and may record one or more receive spectrum status at
each site on every optical fiber pair 22 and store the plurality of
receive spectrum statuses as a baseline spectrum status in a
baseline spectral database 216. In one embodiment, initializing
spectral equalization (step 312) includes comparing, by the
processor, the receive spectrum status with the baseline spectrum
status in the baseline spectral database. In one embodiment,
initializing spectral equalization (step 312) is initialized by the
user and executed by the processor, whereas in another embodiment,
initializing spectral equalization (step 312) is initialized by and
executed by the processor.
[0100] In one embodiment, initializing spectral equalization (step
312) further includes displaying the receive spectrum for every
cable landing station 14 of a selected direction. Displaying the
receive spectrum may include displaying, by a processor, the
receive spectrum for every cable landing station 14 of a selected
direction, on the display 232 of the one or more user device 228.
In one embodiment, displaying the receive spectrum is triggered by
a request from the user via the user device 228.
[0101] In one embodiment, initializing spectral equalization (step
312) further includes adjusting, by the user or the processor 204,
the power of the one or more CW channel and adjusting, by the user
or the processor 204, the wavelength of the one or more CW channel
to equalize the spectrum. In one embodiment, the user or processor
204 may further adjust, increase, decrease, or otherwise modify one
or more ASE channel supplied to the spectrum. In one embodiment,
adjusting, by the user or the processor 204, the power of the one
or more CW channel and adjusting, by the user or the processor 204,
the wavelength of the one or more CW channel to equalize the
spectrum, may be performed first for the longest DLS, that is, the
DLS corresponding the cable landing station 14 in either direction
of the optical trunk 50, i.e., in subsea communication system 10,
the DLS corresponding to the optical trunk 50 between the cable
landing station 14a and the cable landing station 14b. In order to
adjust, increase, decrease, or otherwise modify the one or more ASE
channel, the user, through interaction with the user device 228,
causes the processor 204 to issue one or more command to the
processor 92 of each cable landing station 14 which, in turn,
issues one or more command to the ASE idler 128.
[0102] In one embodiment, initializing spectral equalization (step
312) further includes adjusting, by the user or the processor 204,
the power of the one or more data channel within the spectrum.
[0103] In one embodiment, tuning the one or more CW channel power
and wavelength (step 316) includes adjusting, by the processor 204,
the power and the wavelength of the one or more CW channel
beginning with the DLS having the lowest Q margin, where the Q
margin is the difference between a baseline transmission quality,
in dB, and a current transmission quality, in dB, based on the
receive spectrum status. In one embodiment, the lowest Q margin is
determined by determining a Q margin for each of the one or more
channel by calculating a Q performance less an FEC limit based on a
modulation format of a particular channel, and selecting the
particular channel having the lowest Q margin. In one embodiment,
the lowest Q margin is about 0.5 dB. In one embodiment, tuning the
one or more CW channel power and wavelength (step 316) further
includes adjusting one or more ASE power by sending a command, by
the processor 204, to the processor 92, which in turn sends a
command to the WSS 132, or to the ASE idler 128, to cause the ASE
idler 128 to increase the ASE power.
[0104] Referring now to FIG. 8, shown therein is a block diagram of
an exemplary embodiment of the subsea communication system 10 of
FIG. 2 and a plurality of band pass profiles 350 at various
locations 352 within the subsea communication system 10 when a
cable failure has occurred in the optical branch 58a. When
describing the band pass profiles 350 of the subsea communication
system 10, for simplicity, only one direction is described from
cable landing station 14a to cable landing station 14b, however,
the subsea communication system 10 is a bidirectional optical
network. Additionally, it should be understood that a more complex
subsea communication system 10 having additional band pass profiles
350, additional cable landing stations 14, and additional branching
units 54 than described below may also be constructed in accordance
with the present disclosure. Shown in FIG. 8 is a first set of band
pass profiles 350a indicative of the spectrum on the optical trunk
50 between the cable landing station 14a and the branching unit 54a
shown at location 352a, a second set of band pass profiles 350b
indicative of the spectrum on the optical trunk 50 between the
branching unit 54a and the branching unit 54b shown at location
352b, and a third set of band pass profiles 350c indicative of the
spectrum on the optical trunk 50 between the branching unit 54b and
the cable landing station 14b shown at location 352c. Each set of
band pass profiles 350a-c depicts a first band 354 being routed to
the cable landing station 14b, a second band 358 being routed to
the cable landing station 14d, a third band 362 routed to the cable
landing station 14c, and a CW channel 366. Also shown in FIG. 8 are
cross over points 370a and 370b. The cross over point 370a is an
intersection of an edge of the first band 354 and an edge of the
second band 358a or 358b. The cross over point 370b is an
intersection of the second band 358a or 358b and the third band
362a or 362b. In some embodiments, the set of band pass profiles
350a, 350b, and 350c sets the filter shapes required to either
block or allow particular slices of wavelengths within the bands
354, 358a, 362a, 358a and 362b. Because reconfigurable band pass
filters, such as the notch filter 162a, cannot transition ideally
from a response of 0 dB attenuation for example to entire
attenuation, the edges of the bands 354, 358a, 362a, 358b, and 362b
taper towards entire attenuation. This taper may be referred to in
the art as "roll-off". And, the intersection between the edges of
two adjacent bands, such as the bands 354 and 358a is referred to
as a cross-over point.
[0105] For example, in one embodiment, the subsea communication
system 10, implementing the fast system optimization process 300,
may first detect, at the cable landing station 14a, a cable failure
of the optical branch 58a. In response to detecting the cable
failure, the cable landing station 14a may insert a CW channel,
i.e., the CW channel 366, adjacent to any band of the spectrum
intended to travel along the optical branch 58a, i.e., the third
band 362 being routed to the cable landing station 14c, as
indicated in the first band pass profile 350a of the spectrum.
Thus, the first band pass profile 350a at the location 352a has a
first band 354, a second band 358a, a third band 362a, and a CW
channel 366a, wherein each of the first band 354, the second band
358a, and the third band 362a have a substantially similar band
gain and the CW channel 366a has a first CW gain greater than each
band gain. The second band pass profile 350b at location 352b
depicts the first band 354, the second band 358a, and a CW channel
366b having a second CW gain, however, there is no third band 362
present in the second band pass profile 350b of the spectrum as the
third band 362, intended for the cable landing station 14c, is
dropped at the branching unit 54a by the notch filter 162a and, as
the optical branch 58a has failed, no third band 362 is received by
the branching coupler 154a in the branching unit 54a. By inserting
the CW channel 366 at the cable landing station 14a, power is
balanced across the spectrum and noise is reduced as shown by the
second band pass profile 350b. As the spectrum passes through the
branching unit 54a, the notch filter 162a attenuates the CW channel
366a, such that a portion of the CW channel 366a present at the
location 352b (shown as CW channel 366b) is lesser than the CW
channel 366a. At the location 352c, the third band pass profile
350c depicts the first band 354 still having a band gain similar to
the first band 354 at the second location 352b and at the first
location 352a, however, the third band pass profile 350c further
includes a second band 358b and a third band 362b that has been
restored, such as from the cable landing station 14d.
[0106] Specifically, the branching unit 54b routes the second band
358a to the cable landing station 14d, and receives a second band
358b from the cable landing station 14d. Further, the notch filter
162a of the branching unit 54b passes only the first band 354 and a
portion of the CW channel 366b to the location 352c. The portion of
the CW channel 366b at the location 352c is denoted with the
reference numeral 366c. The CW Channel 366c has less power than the
CW channel 366b. The cable landing station 14d transmits the
restored third band 362b and the second band 358b to the branching
unit 54b via the optical branch 58b where the restored third band
362b, the second band 358b, and the first band 354 are combined by
the branching coupler 154a of the branching unit 54b. In one
embodiment, the third CW gain of the CW channel 366c at location
352c has decayed, or otherwise been reduced, once the third band
362 has been restored as the third band 362b, such that the CW gain
is substantially similar to the band gain for each of the first
gain 354, the second gain 358b, and/or the third gain 362b. In
other embodiments, the subsea communication system 10 includes more
than two branching units 54, more than four cable landing stations
14, and/or more than three bands 354, 358, 362 within the spectrum,
however, the aforementioned example is equally applicable to such
subsea communication systems 10.
[0107] The foregoing description provides illustration and
description, but is not intended to be exhaustive or to limit the
inventive concepts to the precise form disclosed. Modifications and
variations are possible in light of the above teachings or may be
acquired from practice of the methodologies set forth in the
present disclosure.
[0108] Even though particular combinations of features are recited
in the claims and/or disclosed in the specification, these
combinations are not intended to limit the disclosure. In fact,
many of these features may be combined in ways not specifically
recited in the claims and/or disclosed in the specification.
Although each dependent claim listed below may directly depend on
only one other claim, the disclosure includes each dependent claim
in combination with every other claim in the claim set.
[0109] No element, act, or instruction used in the present
application should be construed as critical or essential to the
invention unless explicitly described as such outside of the
preferred embodiment. Further, the phrase "based on" is intended to
mean "based, at least in part, on" unless explicitly stated
otherwise.
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