Note: Descriptions are shown in the official language in which they were submitted.
CA 02568209 2011-02-24
-1-
OPTICAL PACKET ROUTER USING MULTIPLE WAVELENGTH LABELS,
AND OPTICAL PACKET NETWORK THAT USES MULTIPLE
WAVELENGTH LABELS
This application is a division of Canadian Patent Application Serial No.
2,342,556, filed on March 30, 2001.
In view of division enforced by the Canadian Intellectual Property Office the
claims of this application are directed to an optical packet router using
multiple
wavelength labels, and an optical packet network that uses multiple packet
labels.
Accordingly, in view of enforced division required by the Examiner in the
prosecution of the aforesaid parent application, object clauses and features
have been
retained for the purposes of facilitating and understanding of the overall
development.
However, the retention of any clauses or features which may be more
particularly
related to the parent application or a separate divisional thereof should not
be
regarded as rendering the teachings and claiming ambiguous or inconsistent
with the
subject matter defined in the claims of the divisional application presented
herein when
seeking to interpret the scope thereof and the basis in this disclosure for
the claims
recited herein.
FIELD OF THE INVENTION
The present invention relates to optical communication by routing optical
packets using multiple wavelength labels. More particularly, the present
invention
relates to a method for routing optical packets using multiple wavelength
labels that
is based on wavelength division multiplexing (WDM), to an optical packet
router using
multiple wavelength labels, and to an optical packet network that uses
multiple
wavelength labels.
BACKGROUND OF THE INVENTION
In the area of optical packet communications using optical fibers, photonic
networks have been proposed in which not only trunk line links, but even
switching
functions in network nodes connecting a plurality of trunk lines, are
implemented in the
optical domain. In such a network, when each of the optical packets passes
through
CA 02568209 2011-02-24
-2-
a network node, it can autonomously switch to a predetermined route based on
address information carried by the packet. In this respect, there is a need
for an optical
packet routing system that optically labels each packet with the respective
address,
checks and identifies the labels in the optical domain and, based on the
identification
result, switches the output route of the packet.
In prior art photonic networks based on the WDM technology, many
configurations and methods have been proposed in which the routing labels are
comprised as single wavelength optical signals. To identify the packet labels,
this
technology uses simple wavelength identification devices such as arrayed
waveguide
gratings (AWG), which are limited with respect to the number of labels that
can be
identified. Specifically, when single wavelength labels are used, with the
existing level
of technology, most networks can only handle around 100 to 200 labels, and the
upper
limit for any network is around 1000.
For the processing involved, there has been proposed a label switching router
employing a phase code processor that uses an optical code division
multiplexing
(OCDM) system (K. Kitayama and N. Wada, "Photonic IP Routing," IEEE Photon.
Technol. Lett., vol. 11, no. 12, pp. 1689-1691, December 1999). In that
system, the
labels used are phase labels having a pattern comprised of a light phase, such
as 0,îr,
for example, so that the labels are, for example, "000Tr", "00-rr-rr",
"OrrOrr," and so forth,
which are processed by a phase code processor. An input signal constituting a
phase
label is split into a plurality of signals, each of which falls incident on an
independent
optical correlation processor. Each of these optical correlation processors is
configured
to match, i.e. identify, a corresponding independent phase label. This differs
from the
present invention in terms of label configuration method and label processor.
With respect to optical encoding using time spreading/wavelength hopping
codes, Japanese Patent No. 3038378 discloses a method in which streams of
optical
pulses having different wavelengths on a bit-by-bit basis are used for
encoding by
setting different codes within a code sequence specified for each channel,
with
decoding of received signals being effected by matched filtering in the time
domain.
This disclosure differs from the present invention in that the disclosure does
not
pertain to routing.
CA 02568209 2011-02-24
-3-
As described above, with respect to prior art optical packet routing methods
and
apparatuses, and optical packet network configurations, with current
technology, when
single wavelength labels are used, most networks can only handle around 100 to
200
labels, and the upper limit for any network is around 1000 labels.
SUMMARY OF THE INVENTION
The present invention describes a method for routing optical packets using
multiple wavelength labels, an optical packet router using multiple wavelength
labels
and an optical packet network that uses multiple wavelength labels, that
enable
wavelength resources to be effectively utilized by using wavelength division
multiplexing to route optical packets with multiple wavelength labels, thereby
greatly
increasing the number of routing labels that can be used in a network compared
to the
number of routing labels that can be used in a prior art photonic network.
The invention provides a method for routing optical packets using multiple
wavelength labels, the method comprising converting optical packet address
signals
to a plurality of optical pulses having different time-deviated wavelengths by
executing
a first operation to impart a wavelength dependent delay time with respect to
a plurality
of optical pulses having different wavelengths at a same time axis position
and, when
the optical pulses are transmitted along a predetermined optical path having
dispersion, compensating for the dispersion by executing a second operation on
the
optical pulses corresponding to a reverse process of the operation to impart a
wavelength dependent delay time, the second operation resulting in generation
of a
plurality of optical pulses having different wavelengths at a same time axis
position,
and using signals of the pulses thus generated to determine a transmission
route.
The invention also describes a method for routing optical packets using
multiple
wavelength labels, in which a predetermined waveband used for one-bit address
signals and a one-bit data signal waveband have identical bandwidths.
Additionally the invention describes a method in which the bandwidth allocated
to data signals included in optical packets is wider than the bandwidth
allocated to
address signals.
CA 02568209 2011-02-24
-4-
Furthermore, the invention describes a method in which address signals and
data signals are transmitted with a predetermined time differential.
Optical packet address signals may also include address information in which
optical packet address signals include address information that is identified
by
wavelength information delimited by a predetermined waveband width and
predetermined time differential information.
Optical packet address signals may further include first address information
in
which optical packet address signals include first address information that is
identified
by wavelength information delimited by a first waveband width, and second
address
information that is identified by wavelength information delimited by a second
waveband width and predetermined time differential information.
The invention describes a method in which, based on first address information,
routing is performed by a first router that can switch optical paths according
to
wavelength differences and, based on second address information, routing is
performed by a second router that can switch optical paths according to time
differences.
In a first aspect, the invention provides an optical packet router using
multiple
wavelength labels, comprising means for separating data signals and address
signals,
in which means the address signals are identified by wavelength information
delimited
by a predetermined waveband width and predetermined time differential
information
included in optical packets; means for demodulating address information
delimited by
the wavelength information from the address signals to obtain demodulated
address
information; means for switching an optical switch in accordance with the
demodulated
address information; and selection means that uses the optical switch to
select an
optical path for the data signals.
In another aspect, the invention provides a router as described in which the
demodulation means uses a multi-section fiber Bragg grating.
The invention also provides an optical packet router using multiple wavelength
labels comprising a pulse light source that includes multi-wavelength laser
light; means
for dividing pulse signals from the pulse light source into a plurality of
light paths; a
means for obtaining a first pulse signal using a means that interacts with a
multi-
CA 02568209 2011-02-24
-5-
section fiber Bragg grating following modulation of one divided pulse signal;
a means
for obtaining a second pulse signal comprising means for narrowing waveband
width
of other divided pulse signals and means for modulating the reduced-bandwidth
pulse
signals; means for adjusting a time differential between the first pulse
signal and the
second pulse signal; and means for guiding the first and second pulse signals
thus
adjusted to a same light path.
In a second aspect, the invention provides an optical packet communication
network that uses multiple wavelength labels, the network including a
plurality of
routers that can switch optical paths in accordance with differences in
combinations
of multiple optical pulse wavelengths and time differentials included in
address signals,
with at least two of the routers being connected together.
In another aspect, the invention provides an optical packet communication
network that uses multiple wavelength labels, the network including a first
router that
can switch optical paths in accordance with differences in wavelengths of
multiple
optical pulses included in address signals, and a second router that can
switch optical
paths in accordance with differences in combinations of multiple optical pulse
wavelengths and time differentials included in address signals, with the
second router
being connected to the first router.
In a further aspect, there is provided an optical packet router using multiple
wavelength labels used for routing of optical packets which carries data
signals and
address signals that include the optical signals in bands other than the
wavelength
bands of the data signals, comprising means for separating the data signals
from the
address signals, in which means said address signals are identified by
wavelength
information delimited by a predetermined waveband width and predetermined time
differential information included in the optical packets; means for
demodulating
address information from the address signals delimited by the wavelength
information
to obtain demodulated address information; means for switching an optical
switch in
accordance with the demodulated address information; and selection means that
uses
the optical switch to select an optical path for the data signals.
CA 02568209 2011-02-24
-6-
BRIEF DESCRIPTION OF THE INVENTION
Further features of the invention, its nature and various advantages will be
more
apparent from the accompanying drawings and following detailed description of
the
invention, in which:
Figure 1 is a drawing showing the configuration of a multiple wavelength label
switching router system.
Figure 2 shows an example of a first configuration of an optical packet having
a multiple wavelength label.
Figure 3 shows an example of a second configuration of an optical packet
having a multiple wavelength label.
Figure 4 shows an example of a third configuration of an optical packet having
a multiple wavelength label.
Figure 5 shows an example of the configuration of a network that uses multiple
wavelength switching routers and wavelength routers.
Figure 6 illustrates a method of generating multiple wavelength labels using a
multi-section fiber Bragg grating.
Figure 7 illustrates a method of matching multiple wavelength labels using a
multi-section fiber Bragg grating.
Figure 8 is a block diagram of a multiple wavelength packet transmitter that
transmits optical packet signals having multiple wavelength labels.
Figure 9 is a block diagram of part of a multiple wavelength label switching
router that uses an array of multi-section fiber Bragg gratings to process the
multiple
wavelength labels.
Figure 10 shows signal waveforms of each part of a multiple wavelength label
switching router, in which Figure 10(a) shows the detected signal waveform of
a
multiple wavelength label generated by means of a multi-section fiber Bragg
grating;
Figure 10(b) shows the detected signal waveform of the packet consisting of a
header
having a multiple wavelength label and a payload data; Figure 10(c) shows the
detected waveform of a signal signifying a label match output by a multiple
wavelength
label matching unit comprised of a multi-section fiber Bragg grating; Figure
10(d)
shows the detected waveform of a signal signifying a label non-match output by
a
CA 02568209 2011-02-24
-7-
multiple wavelength label matching unit comprised of a multi-section fiber
Bragg
grating; Figure 10(e) shows the detected waveform of a signal output by a
three-port
switch signifying a port #1 multiple wavelength label; and Figure 10(f) shows
the
detected waveform of a signal output by a three-port switch signing a port #3
multiple
wavelength label.
Figure 11 shows an example of a multiple wavelength label switching router
network.
DETAILED DESCRIPTION OF THE INVENTION
In the prior art packet communications, a packet signifies the temporal
propagation of signal system sets. However, in the case of the present
invention, a
packet signifies the wavelength propagation, or both wavelength and temporal
propagation, of signal system sets. The present invention relates to the
handling of
codes having structural elements in the form of a plurality of points in two-
dimensional
space that are propagated in terms of wavelength and temporal direction. In
particular,
the invention uses as optical labels optical signal system data that are
propagated in
terms of both wavelength and time-based direction. Using these optical labels
as
identifiers in optical domain packet switching makes it possible to
effectively utilize
wavelength resources by greatly increasing the number of labels that can be
used
within a single network. Details are explained in the following embodiments.
Figure 1 shows the configuration of a multiple wavelength label switching
router
system. The router comprises a label/data separator 1, a multiple wavelength
label
processor 2, a label converter 3, an optical switch 4, an optical delay unit 5
and optical
couplers 15. Transmitted optical packets, each carrying multiple wavelength
labels
affixed to data as header information, are input to the router. These packets
are
separated into two by the label/data separator 1 and the respective parts sent
to the
label processor 2 and optical delay unit 5. In the label processor 2, the
labels are not
converted to electrical signals, but are read in their native optical signal
form, resulting
in the output of a switch control signal. The control signal is sent to the
optical switch
4, where an optical wave detector converts it to a high-frequency signal that
is applied
to the optical switch 4. The optical delay unit 5 applies a time delay to data
going to the
CA 02568209 2011-02-24
-8-
optical switch 4, the time delay corresponding to the difference between that
optical
path and the optical path to the label processor 2. Following this, the
optical switch 4
outputs a signal based on a control signal from the label processor 2. The
optical
coupler 15 combines this output with a new label output from the label
converter 3,
and outputs the result as an optical packet.
Figure 2 shows an example of a first configuration of an optical packet with a
multiple wavelength label. These optical packets are divided into wavebands
A1, A2,
. . . An. In the following, this is referred to as a large-band configuration.
Each of the
wavebands in this large-band configuration is further subdivided into what is
referred
to as small-band configurations. These small-band configurations are assumed
to
have bands A, B, C, D, E, for example. Address information in small bands is
mapped
into a multiple wavelength pulse train to effect optical labelization. Of the
small bands
A, B, C, D, E, bands A to D are used for multiple wavelength labels and the
remaining
small band E is allocated for the transmission data signals, to thereby
produce the
optical packets. If a large-band label uses 8 waves, this label generation
method
makes it possible to ensure over 10000 labels.
Figure 3 shows an example of a second configuration of an optical packet with
a multiple wavelength label. As in the first example, these optical packets
are divided
into large bands A1, A2, . . . An. To form optical packets, in a small-band
configuration
a small band is allocated to each of the optical pulses used for each optical
label that
has a different center wavelength from the data signals, and all of the
remaining bands
within a large-band member is allocated for the data signal.
Figure 4 shows an example of a third configuration of an optical packet having
a multiple wavelength label. Here, the fill bandwidth of each of the bands A1,
A2,. . .
An is used for address information for the label. Also, data signals are
generated using
the full bandwidth of a large-band member. In this case, the label and data
portions
can be readily separated using a time gate or the like. An advantage of this
configuration is that it makes it possible to easily increase the ratio of
data signal to
address signal.
Figure 5 shows the arrangement of a network using the above multiple
wavelength label switching routers. The network of Figure 5 is configured with
multiple
CA 02568209 2011-02-24
-9-
wavelength label optical packet sender-receivers 7 connected to multiple
wavelength
label switching routers 8 that are linked by commercially available wavelength
routers
9. A single- wavelength-packet sender-receiver 22 can also be connected to the
wavelength router 9. Also, as shown in Figure 11, a network can be formed of
multiple
wavelength label switching routers 8 connected together. In the packet routing
method
of this invention, the wavelength router 9 routes packets on a large-band
configuration
member basis, with the small bands within each large-band configuration member
being regarded as having the same wavelength. However, the multiple wavelength
label switching router 8 identifies down to the small-band configuration level
in
performing routing based on the multiple wavelength label processor 2 and
optical
switch shown in Figure 1. This configuration can be readily merged with a
photonic
network that uses conventional single-wavelength routing.
In the configurations described with reference to Figures 2, 3 and 4, when
large-
band members are divided into small-band members, the small-band members each
have a different center wavelength. Figure 6 shows an example of generation of
multiple wavelength labels in the form of a string of optical pulses arrayed
along the
time axes thereof. As shown in Figure 6, labels can be generated with a time
differential by projecting multiple wavelength pulses onto a multi-section
fiber Bragg
grating and applying to the reflected pulse signals a time delay that differs
in
accordance with the wavelength.
Figure 7 shows a multiple wavelength label discriminator based on a multi-
section fiber Bragg grating. The multi-section fiber Bragg grating shown in
Figure 6 has
a configuration that is inverted with respect to the direction of light
incidence. When
specified multiple wavelength labels fall incident on this label
discriminator, the
reflected signals are adjusted to compensate for the time delay received by
each pulse
during label generation, to thereby reproduce the original multiple wavelength
pulses.
When the label discriminator finds that the combined characteristic
(wavelength and
time-position) of a reflected band does not match that of an incident label,
no
compensation is effected for the time delay received at the time the label was
generated, so the original pulses are not reproduced. Thus, it becomes
possible to
distinguish between matching and non-matching labels by subjecting the output
of the
CA 02568209 2011-02-24
-10-
label discriminator to threshold processing. The multiple wavelength label
processor
shown in Figure 1 can be configured with an array of multi-section fiber Bragg
grating
based label discriminators. Optical packets that simultaneously fall incident
on the
array can then be simultaneously processed using a routing table and packet
labels
to assign predetermined routes and labels.
Figure 8 is a block diagram of a multiple wavelength packet transmitter that
transmits optical packet signals having multiple wavelength labels. In Figure
8, a
supercontinuum light source 10 denotes a multiple wavelength light source with
a
center wavelength of 1.56pm. This light source produces light pulses with a
broad
wavelength distribution. The light pulses emitted by the light source 10 pass
through
an optical coupler 17a and a bandpass filter 16 with a 5-nm bandpass
characteristic.
Light pulses transmitted by the bandpass filter 16 form a small-band member
constituting a data signal, and light pulses that are not transmitted by the
bandpass
filter 16 form a group of small-band members constituting a multiple
wavelength label.
By means of an intensity modulator 12b, the optical signals passed by the
filter 16 are
intensity-modulated by a 10-Gbps electrical signal generated by a pattern
generator
11b and time-adjusted by the optical delay unit 5 to form burst data. Light
that does
not go to the filter 16 is intensity-modulated by an intensity modulator 12a,
using a 10-
Gbps electrical signal generated by a pattern generator 11a, and is input to a
multi-
section fiber Bragg grating 13 connected to the light path by a circulator 14,
to thereby
form a multiple wavelength label. The burst data and multiple wavelength label
are
combined by an optical coupler 17b and output as an optical packet.
Figure 9 is a block diagram of a part 21 of a multiple wavelength label
switching
router that uses an array of three multi-section fiber Bragg gratings 13, each
having
a different characteristic, to process the multiple wavelength labels. Optical
packets
having multiple wavelength labels that are input to the router are divided by
an optical
coupler 17a1 into a label portion that does not pass through the bandpass
filter 16,
and a data portion that does go to the bandpass filter 16. The light is
divided into a
plurality of beams by the optical coupler 17a2, with each beam going via a
circulator
14 to fall incident on a multi-section fiber Bragg grating 13. Label matching
is
performed using the multi-section fiber Bragg grating system shown in Figure
7. When
CA 02568209 2011-02-24
-11-
there is a label match, the label discriminator outputs a switch operation
control signal
that opens a specific gate switch, allowing the emission of data-section
signals from
a selected port.
Figure 10 shows the waveforms of signals from the multiple wavelength packet
transmitter of Figure 8 that are input to the router shown in Figure 9. Figure
10(a)
shows the signal waveform of a multiple wavelength label generated by means of
a
multi-section fiber Bragg grating; Figure 10(b) shows the signal waveform of
the packet
consisting of a header having a multiple wavelength label and a payload data;
Figure
10(c) shows the waveform of a signal signifying a label match output by a
multiple
wavelength label matching unit comprised of a multi-section fiber Bragg
grating; Figure
10(d) shows the waveform of a signal signifying a label non-match output by a
multiple
wavelength label matching unit comprised of a multi-section fiber Bragg
grating; Figure
10(e) shows the waveform of a signal output by a three-port switch signifying
a port #1
multiple wavelength label; and Figure 10(f) shows the waveform of a signal
output by
a three-port switch signifying a port #3 multiple wavelength label. This
method of the
present invention for routing optical packets using multiple wavelength
labels, enables
problem-free routing of optical signals.
The invention having the configurations described in the foregoing
embodiments and aspects provides the following effects. It readily enables
routing to
be carried out in an optical packet communication system, using labels
comprised of
multiple wavelength optical pulses. The fact that optical pulses in a two-
dimensional
space defined by wavelength and time axes are used as the basic address
signals
greatly increases the number of labels that can be used for routing purposes.
Moreover, these address signals can be readily generated by means of a simple
configuration that uses multi-section fiber Bragg gratings, facilitating the
generation of
packet routing labels and the routing itself. The optical packet router of the
invention
can also be used in conjunction with a conventional packet routing system that
switches paths based on wavelength differences. Networks can also be
configured
with optical packet routers of the invention connected together.
