U.S. patent application number 09/799070 was filed with the patent office on 2002-02-21 for optical power managed network node for processing dense wavelength division multiplexed optical signals.
Invention is credited to Emkey, William L., Turner, Ian, Wade, Robert K..
Application Number | 20020021463 09/799070 |
Document ID | / |
Family ID | 26882712 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020021463 |
Kind Code |
A1 |
Turner, Ian ; et
al. |
February 21, 2002 |
Optical power managed network node for processing dense wavelength
division multiplexed optical signals
Abstract
A technique for processing dense wavelength division multiplexed
optical signals in a network node is disclosed. In one embodiment,
the technique is realized as an optical power managed network node
comprising a dense wavelength division multiplexing device for
combining a plurality of narrowband optical signals into a
multiplexed polychromatic optical signal. The optical power managed
network node also comprises a wavelength-selective optical power
detector for detecting the power of each of the plurality of
narrowband optical signals combined into the multiplexed
polychromatic optical signal. The optical power managed network
node further comprises a plurality of attenuators for attenuating
the power of at least one of the plurality of narrowband optical
signals based upon the detected power of each of the plurality of
narrowband optical signals.
Inventors: |
Turner, Ian; (Stratham,
NH) ; Emkey, William L.; (Windham, NH) ; Wade,
Robert K.; (Boca Raton, FL) |
Correspondence
Address: |
Thomas E. Anderson
Hunton & Williams
1900 K Street, N.W.
Washington
DC
20006-1109
US
|
Family ID: |
26882712 |
Appl. No.: |
09/799070 |
Filed: |
March 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60187101 |
Mar 6, 2000 |
|
|
|
Current U.S.
Class: |
398/79 ; 398/34;
398/38; 398/9 |
Current CPC
Class: |
H04J 14/0221 20130101;
H04B 10/07955 20130101; H04Q 2011/005 20130101; H04Q 11/0005
20130101; H04B 10/077 20130101; H04Q 2011/0058 20130101 |
Class at
Publication: |
359/124 ;
359/110 |
International
Class: |
H04B 010/08; H04J
014/02; H04B 010/00 |
Claims
What is claimed is:
1. An optical power managed network node for processing dense
wavelength division multiplexed signals comprising: a dense
wavelength division multiplexing device for combining a plurality
of narrowband optical signals into a multiplexed polychromatic
optical signal; a wavelength-selective optical power detector for
detecting the power of each of the plurality of narrowband optical
signals combined into the multiplexed polychromatic optical signal;
and a plurality of attenuators for attenuating the power of at
least one of the plurality of narrowband optical signals based upon
the detected power of each of the plurality of narrowband optical
signals.
2. The optical power managed network node as defined in claim 1,
further comprising: an adjustable power amplifier for adjustably
amplifying the power of the multiplexed polychromatic optical
signal based upon the detected power of each of the plurality of
narrowband optical signals.
3. The optical power managed network node as defined in claim 1,
wherein the at least one of the plurality of narrowband optical
signals is attenuated so as to equalize the power in each of the
plurality of narrowband optical signals.
4. The optical power managed network node as defined in claim 1,
wherein the at least one of the plurality of narrowband optical
signals is attenuated prior to being combined into the multiplexed
polychromatic optical signal.
5. The optical power managed network node as defined in claim 1,
wherein the plurality of narrowband optical signals is a first
plurality of narrowband optical signals, further comprising: a
switching device for switching a second plurality of narrowband
optical signals according to a predetermined signal routing scheme,
wherein the second plurality of narrowband optical signals
constitutes at least a portion of the first plurality of narrowband
optical signals.
6. The optical power managed network node as defined in claim 5,
wherein at least one of the second plurality of narrowband optical
signals is switched such that the at least one switched narrowband
optical signal is routed to a local sub-node.
7. The optical power managed network node as defined in claim 5,
wherein at least one of the second plurality of narrowband optical
signals is switched such that the at least one switched narrowband
optical signal is routed through the optical power managed network
node.
8. The optical power managed network node as defined in claim 7,
wherein the switching device receives at least one of a third
plurality of narrowband optical signals for routing through the
optical power managed network node.
9. The optical power managed network node as defined in claim 8,
wherein the first plurality of narrowband optical signals comprises
those of the second plurality of narrowband optical signals and the
third plurality of narrowband optical signals that are routed
through the optical power managed network node.
10. The optical power managed network node as defined in claim 8,
further comprising: a controller for controlling the power of the
at least one of the third plurality of narrowband optical signals
based upon the detected power of each of the plurality of
narrowband optical signals.
11. The optical power managed network node as defined in claim 5,
wherein the multiplexed polychromatic optical signal is a first
multiplexed polychromatic optical signal, further comprising: a
demultiplexing device for separating a second multiplexed
polychromatic optical signal into the second plurality of
narrowband optical signals.
12. The optical power managed network node as defined in claim 11,
wherein the wavelength-selective optical power detector also
detects the power of each of the second plurality of narrowband
optical signals contained within the second multiplexed
polychromatic optical signal.
13. The optical power managed network node as defined in claim 11,
wherein the wavelength-selective optical power detector is a first
wavelength-selective optical power detector, further comprising: a
second wavelength-selective optical power detector for detecting
the power of each of the second plurality of narrowband optical
signals contained within the second multiplexed polychromatic
optical signal.
14. A method for processing dense wavelength division multiplexed
signals in an optical power managed network node, the method
comprising the steps of: combining a plurality of narrowband
optical signals into a multiplexed polychromatic optical signal;
detecting the power of each of the plurality of narrowband optical
signals combined into the multiplexed polychromatic optical signal;
and attenuating the power of at least one of the plurality of
narrowband optical signals based upon the detected power of each of
the plurality of narrowband optical signals.
15. The method as defined in claim 14, further comprising the step
of: adjustably amplifying the power of the multiplexed
polychromatic optical signal based upon the detected power of each
of the plurality of narrowband optical signals.
16. The method as defined in claim 14, wherein the at least one of
the plurality of narrowband optical signals is attenuated so as to
equalize the power in each of the plurality of narrowband optical
signals.
17. The method as defined in claim 14, wherein the at least one of
the plurality of narrowband optical signals is attenuated prior to
being combined into the multiplexed polychromatic optical
signal.
18. The method as defined in claim 14, wherein the plurality of
narrowband optical signals is a first plurality of narrowband
optical signals, further comprising the step of: switching a second
plurality of narrowband optical signals according to a
predetermined signal routing scheme, wherein the second plurality
of narrowband optical signals constitutes at least a portion of the
first plurality of narrowband optical signals.
19. The method as defined in claim 18, wherein at least one of the
second plurality of narrowband optical signals is switched such
that the at least one switched narrowband optical signal is routed
to a local sub-node.
20. The method as defined in claim 18, wherein at least one of the
second plurality of narrowband optical signals is switched such
that the at least one switched narrowband optical signal is routed
through the optical power managed network node.
21. The method as defined in claim 20, further comprising the step
of: receiving at least one of a third plurality of narrowband
optical signals for routing through the optical power managed
network node.
22. The method as defined in claim 21, wherein the first plurality
of narrowband optical signals comprises those of the second
plurality of narrowband optical signals and the third plurality of
narrowband optical signals that are routed through the optical
power managed network node.
23. The method as defined in claim 21, further comprising the step
of: controlling the power of the at least one of the third
plurality of narrowband optical signals based upon the detected
power of each of the plurality of narrowband optical signals.
24. The method as defined in claim 18, wherein the multiplexed
polychromatic optical signal is a first multiplexed polychromatic
optical signal, further comprising the step of: separating a second
multiplexed polychromatic optical signal into the second plurality
of narrowband optical signals.
25. The method as defined in claim 24, wherein the step of
detecting includes detecting the power of each of the second
plurality of narrowband optical signals contained within the second
multiplexed polychromatic optical signal.
26. The method as defined in claim 24, further comprising the step
of: detecting the power of each of the second plurality of
narrowband optical signals contained within the second multiplexed
polychromatic optical signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. Provisional
Patent Application No. 60/187,101, filed Mar. 6, 2000, which is
hereby incorporated by reference herein in its entirety.
[0002] This patent application is related to U.S. patent
application Ser. No. 09/578,721, filed May 26, 2000, which is
hereby incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0003] The present invention relates generally to dense wavelength
division multiplexing networks and, more particularly, to an
optical power managed network node for processing dense wavelength
division multiplexed optical signals.
BACKGROUND OF THE INVENTION
[0004] Dense wavelength division multiplexing (DWDM) networks
typically comprise a plurality of network nodes for receiving and
transmitting dense wavelength division multiplexed optical signals.
Each of the plurality of network nodes typically allows an
individual optical signal that is contained in a received dense
wavelength division multiplexed optical signal to either simply
pass through the network node and then be transmitted further along
the network from the network node, or be "dropped" at the network
node for use by one or more sub-nodes connected to the network
node. Each of the plurality of network nodes also typically allows
one or more individual optical signals to be "added" to the network
at the network node. These "added" optical signals are typically
transmitted further along the network from the network node along
with other optical signals that are received at the network node,
but are not "dropped" at the network node. The above-described
network node is generally referred to as an optical add/drop
network node due to the "adding" and "dropping" functions performed
by the network node.
[0005] The "adding" and "dropping" functions performed by most
existing optical add/drop network nodes typically result in a
difference between the power of a dense wavelength division
multiplexed optical signal that is received at the optical add/drop
network node and the power of a dense wavelength division
multiplexed optical signal that is transmitted from the optical
add/drop network node. For example, if more optical signals are
"dropped" at the optical add/drop network node than are "added" at
the optical add/drop network node, then the power of the dense
wavelength division multiplexed optical signal that is received at
the optical add/drop network node will typically be more than the
power of the dense wavelength division multiplexed optical signal
that is transmitted from the optical add/drop network node.
[0006] Also, most existing optical add/drop network nodes typically
inflict some degree of loss upon the power of the optical signals
that are received at each network node. That is, an optical
add/drop network node typically receives a dense wavelength
division multiplexed optical signal in multiplexed form, and then
demultiplexes the received dense wavelength division multiplexed
optical signal in order for the individual optical signals that are
contained within the received dense wavelength division multiplexed
optical signal to be processed by the optical add/drop network
node. Also, the processing of the individual optical signals at an
optical add/drop network node typically comprises switching the
individual optical signals such that the individual optical signals
are either passed through the optical add/drop network node or
"dropped" at the optical add/drop network node. Further, the
individual optical signals that are passed through the optical
add/drop network node are recombined (i.e., multiplexed) prior to
being transmitted further along the network from the optical
add/drop network node. All of the above-described demultiplexing,
switching, and multiplexing functions typically inflict some degree
of loss upon the power of the optical signals that are received at
the optical add/drop network node.
[0007] The above-described multiplexing function losses that are
inflicted upon the power of the optical signals that are received
at the optical add/drop network node are also typically inflicted
upon the power of any optical signals that are "added" to the
network at the optical add/drop network node. That is, optical
signals that are "added" to the network at the optical add/drop
network node are combined (i.e., multiplexed) with optical signals
that are otherwise received at the optical add/drop network node,
and a resulting dense wavelength division multiplexed optical
signal is transmitted further along the network from the optical
add/drop network node. Thus, optical signals that are "added" to
the network at the optical add/drop network node are also typically
subject to multiplexing function losses.
[0008] Furthermore, optical signals that are "added" to a network
at most existing optical add/drop network nodes typically have a
power level that is different from the optical signals that are
otherwise received at the optical add/drop network node. This
difference in power between "added" optical signals and optical
signals that are otherwise received at the optical add/drop network
node typically effects the power of the resulting dense wavelength
division multiplexed optical signal that is transmitted further
along the network from the optical add/drop network node. For
example, if the power of "added" optical signals is greater than
the power of optical signals that are otherwise received at the
optical add/drop network node, then the power of the resulting
dense wavelength division multiplexed optical signal that is
transmitted further along the network from the optical add/drop
network node is typically greater than the power of the dense
wavelength division multiplexed optical signal that is initially
received at the optical add/drop network node.
[0009] Additionally, differences in power between "added" optical
signals and optical signals that are otherwise received at most
existing optical add/drop network nodes can cause problems such as,
for example, channel crosstalk, in the resulting dense wavelength
division multiplexed optical signal that is transmitted further
along the network from the optical add/drop network node. That is,
when "added" optical signals are combined (i.e., multiplexed) with
optical signals that are otherwise received at the optical add/drop
network node, the higher power optical signals often interfere with
the lower power optical signals.
[0010] All of the above-described power related problems associated
with existing optical add/drop network nodes require an operator of
a network to continually perform some type of manual network
initialization procedure whenever additional optical signals are
added to the network, existing optical signals are dropped from the
network, or the network is otherwise reconfigured in some manner
(e.g., an additional optical add/drop network node is added to the
network, an existing optical add/drop network node is removed from
the network, etc.). That is, a network operator typically has to
perform such a manual network initialization procedure whenever a
change occurs in the network such that there is a corresponding
change in the power of a dense wavelength division multiplexed
optical signal that is transmitted from an optical add/drop network
node. Such a change in the power of a dense wavelength division
multiplexed optical signal that is transmitted from an optical
add/drop network node is seen at every subsequent optical add/drop
network node that receives this same dense wavelength division
multiplexed optical signal either directly or after all or a
portion of this same dense wavelength division multiplexed optical
signal propagates through one or more subsequent optical add/drop
network nodes. Thus, a network operator typically has to perform a
manual network initialization procedure on most, if not all,
optical add/drop network nodes in the network so that these optical
add/drop network nodes can accommodate the change in the power of
every received dense wavelength division multiplexed optical
signal.
[0011] Obviously, the above-described manual network initialization
procedure can be costly in terms of both time spent by a network
operator and the cost of optical power measurement and adjustment
equipment. Thus, it would be desirable to provide a technique for
overcoming the above-described inadequacies and shortcomings of
existing optical add/drop network nodes. More particularly, it
would be desirable to provide an optical power managed network node
for processing dense wavelength division multiplexed optical
signals in an efficient and cost effective manner.
OBJECTS OF THE INVENTION
[0012] The primary object of the present invention is to provide an
optical power managed network node for processing dense wavelength
division multiplexed optical signals in an efficient and cost
effective manner.
[0013] The above-stated primary object, as well as other objects,
features, and advantages, of the present invention will become
readily apparent to those of ordinary skill in the art from the
following summary and detailed descriptions, as well as the
appended drawings. While the present invention is described below
with reference to preferred embodiment(s), it should be understood
that the present invention is not limited thereto. Those of
ordinary skill in the art having access to the teachings herein
will recognize additional implementations, modifications, and
embodiments, as well as other fields of use, which are within the
scope of the present invention as disclosed and claimed herein, and
with respect to which the present invention could be of significant
utility.
SUMMARY OF THE INVENTION
[0014] According to the present invention, a technique for
processing dense wavelength division multiplexed optical signals in
a network node is provided. In a first embodiment, the technique is
realized as an optical power managed network node comprising a
dense wavelength division multiplexing device for combining a
plurality of narrowband optical signals into a multiplexed
polychromatic optical signal. The optical power managed network
node also comprises a wavelength-selective optical power detector
for detecting the power of each of the plurality of narrowband
optical signals combined into the multiplexed polychromatic optical
signal. The optical power managed network node further comprises a
plurality of attenuators for attenuating the power of at least one
of the plurality of narrowband optical signals based upon the
detected power of each of the plurality of narrowband optical
signals. The plurality of narrowband optical signals are
beneficially attenuated, prior to being combined into the
multiplexed polychromatic optical signal, so as to equalize the
power in each of the plurality of narrowband optical signals.
[0015] In accordance with other aspects of the present invention,
the optical power managed network node further beneficially
comprises an adjustable optical power amplifier for adjustably
amplifying the power of the multiplexed polychromatic optical
signal based upon the detected power of each of the plurality of
narrowband optical signals.
[0016] In accordance with further aspects of the present invention,
the plurality of narrowband optical signals is preferably a first
plurality of narrowband optical signals, and the optical power
managed network node further beneficially comprises a switching
device for switching a second plurality of narrowband optical
signals according to a predetermined signal routing scheme, wherein
the second plurality of narrowband optical signals constitutes at
least a portion of the first plurality of narrowband optical
signals. The second plurality of narrowband optical signals are
beneficially switched such that the second plurality of narrowband
optical signals are routed to either a local sub-node or through
the optical power managed network node.
[0017] In accordance with still further aspects of the present
invention, the switching device beneficially receives at least one
of a third plurality of narrowband optical signals for routing
through the optical power managed network node. The first plurality
of narrowband optical signals beneficially comprises those of the
second plurality of narrowband optical signals and the third
plurality of narrowband optical signals that are routed through the
optical power managed network node.
[0018] In accordance with still further aspects of the present
invention, the optical power managed network node further
beneficially comprises a controller for controlling the power of at
least one of the third plurality of narrowband optical signals
based upon the detected power of each of the plurality of
narrowband optical signals.
[0019] In accordance with still further aspects of the present
invention, the multiplexed polychromatic optical signal is
preferably a first multiplexed polychromatic optical signal, and
the optical power managed network node further beneficially
comprises a demultiplexing device for separating a second
multiplexed polychromatic optical signal into the second plurality
of narrowband optical signals. The wavelength-selective optical
power detector may beneficially detect the power of each of the
second plurality of narrowband optical signals contained within the
second multiplexed polychromatic optical signal. Alternatively, the
optical power managed network node may further beneficially
comprise a second wavelength-selective optical power detector for
detecting the power of each of the second plurality of narrowband
optical signals contained within the second multiplexed
polychromatic optical signal.
[0020] In an alternative embodiment, the technique is realized as a
method for processing dense wavelength division multiplexed signals
in an optical power managed network node. The method comprises
combining a plurality of narrowband optical signals into a
multiplexed polychromatic optical signal, and then detecting the
power of each of the plurality of narrowband optical signals
combined into the multiplexed polychromatic optical signal. The
method also comprises attenuating the power of at least one of the
plurality of narrowband optical signals based upon the detected
power of each of the plurality of narrowband optical signals. As in
the first embodiment of the optical power managed network node
described above, the plurality of narrowband optical signals are
beneficially attenuated, prior to being combined into the
multiplexed polychromatic optical signal, so as to equalize the
power in each of the plurality of narrowband optical signals.
[0021] In accordance with other aspects of the present invention,
the power of the multiplexed polychromatic optical signal is
beneficially adjustably amplified based upon the detected power of
each of the plurality of narrowband optical signals.
[0022] In accordance with further aspects of the present invention,
the plurality of narrowband optical signals is preferably a first
plurality of narrowband optical signals, and a second plurality of
narrowband optical signals is beneficially switched according to a
predetermined signal routing scheme, wherein the second plurality
of narrowband optical signals constitutes at least a portion of the
first plurality of narrowband optical signals. Again, the second
plurality of narrowband optical signals are beneficially switched
such that the second plurality of narrowband optical signals are
routed to either a local sub-node or through the optical power
managed network node.
[0023] In accordance with still further aspects of the present
invention, at least one of a third plurality of narrowband optical
signals is beneficially received for routing through the optical
power managed network node. Again, the first plurality of
narrowband optical signals beneficially comprises those of the
second plurality of narrowband optical signals and the third
plurality of narrowband optical signals that are routed through the
optical power managed network node.
[0024] In accordance with still further aspects of the present
invention, the power of at least one of the third plurality of
narrowband optical signals is beneficially controlled based upon
the detected power of each of the plurality of narrowband optical
signals.
[0025] In accordance with still further aspects of the present
invention, the multiplexed polychromatic optical signal is
preferably a first multiplexed polychromatic optical signal, and a
second multiplexed polychromatic optical signal is beneficially
separated into the second plurality of narrowband optical signals.
The power of each of the second plurality of narrowband optical
signals contained within the second multiplexed polychromatic
optical signal can be beneficially detected either separately or
along with the power of each of the first plurality of narrowband
optical signals.
[0026] The present invention will now be described in more detail
with reference to exemplary embodiments thereof as shown in the
appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to facilitate a fuller understanding of the present
invention, reference is now made to the appended drawings. These
drawings should not be construed as limiting the present invention,
but are intended to be exemplary only.
[0028] FIG. 1 is a schematic diagram of a preferred embodiment of
an optical power managed network node for processing dense
wavelength division multiplexed optical signals in accordance with
the present invention.
[0029] FIG. 2 is a schematic diagram of a preferred embodiment of
an optical wavelength control technique in accordance with the
present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)
[0030] Referring to FIG. 1, there is shown a schematic diagram of a
preferred embodiment of an optical power managed network node for
processing dense wavelength division multiplexed optical signals in
accordance with the present invention. The optical power managed
network node 10 comprises a demultiplexing device 12, a switching
device 14, a plurality of variable optical attenuators 16, a
multiplexing device 18, a variable optical amplifier or gain
element 20, a wavelength-selective optical power
detector/controller 22, a first plurality of optical
receivers/transmitters 24, and a second plurality of optical
transmitters/receivers 26. The optical power managed network node
10 operates, through its aforementioned constituent parts, as
follows.
[0031] The demultiplexing device 12 receives a first dense
wavelength division multiplexed (DWDM) polychromatic optical signal
on an optical input fiber 28. The first DWDM polychromatic optical
signal contains a first plurality of narrowband optical signals,
each carrying a unique channel of transmitted data. The
demultiplexing device 12 separates the first DWDM polychromatic
optical signal into the first plurality of narrowband optical
signals contained therein and forwards each of the first plurality
of narrowband optical signals to the switching device 14 along a
corresponding plurality of optical fibers 30.
[0032] The switching device 14 switches the first plurality of
narrowband optical signals according to some signal routing scheme.
That is, each of the first plurality of narrowband optical signals
either pass through the switching device 14 so as to be output from
the switching device 14 on one of a plurality of optical fibers 32,
or are "dropped" by the optical power managed network node 10, and
hence from the network to which the optical power managed network
node 10 is connected. Those narrowband optical signals that are
"dropped" by the optical power managed network node 10 are output
from the switching device 14 on optical fibers 34, which are
connected to the first plurality of optical receivers/transmitters
24. The first plurality of optical receivers/transmitters 24
transmit the narrowband optical signals received on optical fibers
34 to one or more sub-nodes (not shown) via output optical fibers
36. Of course, the optical fibers 34 that carry the narrowband
optical signals from the optical power managed network node 10
could extend all the way to the one or more sub-nodes (not shown),
thereby alleviating the need for the first plurality of optical
receivers/transmitters 24.
[0033] The second plurality of optical receivers/transmitters 26
may or may not be connected to the same sub-nodes as the first
plurality of optical receivers/transmitters 24. In any event, the
second plurality of optical receivers/transmitters 26 receive
narrowband optical signals from one or more sub-nodes (not shown)
on input optical fibers 38. The second plurality of optical
receivers/transmitters 26 transmit the narrowband optical signals
received on input optical fibers 38 to the switching device 14 via
optical fibers 40. Of course, as with the optical fibers 34 that
carry the narrowband optical signals from the optical power managed
network node 10, the optical fibers 40 that carry the narrowband
optical signals to the optical power managed network node 10 could
extend all the way from the one or more sub-nodes (not shown),
thereby alleviating the need for the second plurality of optical
receivers/transmitters 26.
[0034] The switching device 14 "adds" the narrowband optical
signals received on optical fibers 40 to the network to which the
optical power managed network node 10 is connected. That is, the
switching device 14 includes the narrowband optical signals
received on optical fibers 40 with those narrowband optical signals
from the first plurality of narrowband optical signals that pass
through the switching device 14 and are output from the switching
device 14 on one of the plurality of optical fibers 32. Thus, the
plurality of optical fibers 32 carry a second plurality of
narrowband optical signals comprised of the narrowband optical
signals from the first plurality of narrowband optical signals that
pass through the switching device 14 (i.e., those of the first
plurality of narrowband optical signals that are not "dropped" by
the optical power managed network node 10), as well as the "added"
narrowband optical signals received at the switching device 14 on
optical fibers 40.
[0035] At this point it should be noted that the switching device
14 can be, for example, a switch matrix or some other type of fixed
or dynamic optical signal switching element.
[0036] The plurality of optical fibers 32 carry the second
plurality of narrowband optical signals to the plurality of
variable optical attenuators 16. As described in more detail below,
the plurality of variable optical attenuators 16 act to equalize
the power level of each of the second plurality of narrowband
optical signals based upon the detected power level of each of the
second plurality of narrowband optical signals after they have been
multiplexed by the multiplexing device 18 and amplified by the
variable optical amplifier or gain element 20. Thus, at this point,
suffice it to say that the plurality of variable optical
attenuators 16 act to equalize the power level of each of the
second plurality of narrowband optical signals prior to being
multiplexed by the multiplexing device 18. The plurality of
variable optical attenuators 16 thus provide an attenuated version
of the second plurality of narrowband optical signals to the
multiplexing device 18 via a plurality of optical fibers 42.
[0037] As mentioned above, the multiplexing device 18 combines the
attenuated version of the second plurality of narrowband optical
signals into a second dense wavelength division multiplexed (DWDM)
polychromatic optical signal and forwards this second DWDM
polychromatic optical signal to the variable optical amplifier or
gain element 20 on an optical output fiber 44. As described in more
detail below, the variable optical amplifier or gain element
amplifies this second DWDM polychromatic optical signal based upon
the detected power level of each of the second plurality of
narrowband optical signals contained in the second DWDM
polychromatic optical signal (i.e., after attenuation by the
plurality of variable optical attenuators 16 and multiplexing by
the multiplexing device 18). The variable optical amplifier or gain
element 20 thus provides an amplified version of the second DWDM
polychromatic optical signal on output optical fiber 46. At this
point it should be noted that the variable optical amplifier or
gain element 20 could be, for example, an erbium doped fiber
amplifier (EDFA), an erbium doped waveguide amplifier (EDWA), a
Raman amplifier, or some other type of variable optical amplifier
or gain element.
[0038] The wavelength-selective optical power detector/controller
22 taps a portion of the amplified version of the second DWDM
polychromatic optical signal being carried on output optical fiber
46 via an optical tap fiber 48 so as to detect the power level of
each of the second plurality of narrowband optical signals
contained in the second DWDM polychromatic optical signal (i.e.,
after attenuation by the plurality of variable optical attenuators
16 and multiplexing by the multiplexing device 18). One technique
for accomplishing this power detection function is described in
related U.S. patent application Ser. No. 09/578,721, filed May 26,
2000, which has previously been incorporated by reference herein in
its entirety.
[0039] After determining the power level of each of the second
plurality of narrowband optical signals contained in the second
DWDM polychromatic optical signal (i.e., after attenuation by the
plurality of variable optical attenuators 16 and multiplexing by
the multiplexing device 18), the wavelength-selective optical power
detector/controller 22 provides one or more first power control
signals to the plurality of variable optical attenuators 16 on a
first power control signal line/bus 50, and provides a second power
control signal to the variable optical amplifier or gain element 20
on a second power control signal line/bus 52. These first and
second power control signals allow the power level of the amplified
version of the second DWDM polychromatic optical signal on output
optical fiber 46 to be controlled such that the amplified version
of the second DWDM polychromatic optical signal on output optical
fiber 46 is always at a constant power level. Thus, the optical
power managed network node 10 always provides a constant power
level DWDM polychromatic optical output signal. This constant power
level DWDM polychromatic optical output signal provided by the
optical power managed network node 10 is probably most beneficial
when it matches the power level of the first DWDM polychromatic
optical signal on the optical input fiber 28, thereby resulting in
the optical power managed network node 10 having a zero decibel
(dB) level loss. Thus, the present invention optical power managed
network node 10 alleviates the need for manual network
initialization procedures whenever additional optical signals are
added to a network, existing optical signals are dropped from a
network, or a network is otherwise reconfigured in some manner
(e.g., an additional optical add/drop network node is added to a
network, an existing optical add/drop network node is removed from
a network, etc.).
[0040] At this point it should be noted that the
wavelength-selective optical power detector/controller 22 may also
provide a third power control signal to the second plurality of
optical receivers/transmitters 26 on a third power control signal
line/bus 54 so as to control the power level of the second
plurality of optical receivers/transmitters 26 which transmit the
narrowband optical signals received on input optical fibers 38 to
the switching device 14 via optical fibers 40. This additional
aspect of power level control in accordance with the present
invention may be beneficial in that the second plurality of optical
receivers/transmitters 26 may be of a lower power variety, thereby
requiring less cost.
[0041] At this point it should be noted that the
wavelength-selective optical power detector/controller 22 may also
tap a portion of the first DWDM polychromatic optical signal being
carried on optical input fiber 28 via an optical tap fiber 56 so as
to detect the power level of each of the first plurality of
narrowband optical signals contained in the first DWDM
polychromatic optical signal. This additional aspect of power level
control in accordance with the present invention may be beneficial
in that the power level of each of the first plurality of
narrowband optical signals contained in the first DWDM
polychromatic optical signal may be detected so as to determine id
if any failures have occurred in the network.
[0042] Referring to FIG. 2, there is shown a schematic diagram of a
preferred embodiment of an optical wavelength control system 60 in
accordance with the present invention. The optical wavelength
control system 60 comprises a central office 62, an optical
cross-connect 64, an optical wavelength monitor 66, and a laser
locking device 68. The optical wavelength control system 60
operates, through its aforementioned constituent parts, as
follows.
[0043] The central office 62 receives and transmits a plurality of
narrowband optical signals from and to the optical cross-connect
via a plurality of optical fibers 76. The plurality of optical
fibers 76 connect to a plurality of multiplexing/demultiplexing
devices within the optical cross-connect 64. That is, the optical
cross-connect 64 includes a first multiplexing/demultiplexing
device 70, a second multiplexing/demultiplexing device 72, and a
third multiplexing/demultiplexing device 74, each for receiving and
transmitting the plurality of narrowband optical signals from and
to the central office 62 via the plurality of optical fibers 76.
The plurality of multiplexing/demultiplexing devices 70, 72, 74
within the optical cross-connect 64 perform multiplexing functions
on the plurality of narrowband optical signals received from the
central office 62 so as to generate dense wavelength division
multiplexed (DWDM) polychromatic optical signals transmitted on
optical fibers 78, 80, 82, respectively. The plurality of
multiplexing/demultiplexing devices 70, 72, 74 within the optical
cross-connect 64 also perform demultiplexing functions on DWDM
polychromatic optical signals received on optical fibers 78, 80,
82, respectively, so as to generate the plurality of narrowband
optical signals transmitted to the central office 62.
[0044] Similar to the wavelength-selective optical power
detector/controller 22 of FIG. 1, the optical wavelength monitor 66
of FIG. 2 taps a portion of the DWDM polychromatic optical signals
being carried on each of the optical fibers 78, 80, 82 via optical
tap fibers 84, 86, 88, respectively, so as to detect the wavelength
of each of the plurality of narrowband optical signals contained in
all of the DWDM polychromatic optical signals. One technique for
accomplishing this wavelength monitoring function is described in
related U.S. patent application Ser. No. 09/578,721, filed May 26,
2000, which has previously been incorporated by reference herein in
its entirety.
[0045] The optical wavelength monitor 66 provides an indication of
the wavelength of each of the plurality of narrowband optical
signals contained in all of the DWDM polychromatic optical signals
to the laser locking device 68 via one or more wavelength indicator
lines 90. The laser locking device 68 in turn provides one or more
laser control signals to the central office 62 via laser control
lines 92. These laser control signals provide a mechanism for
controlling the accuracy of the wavelengths of each of the
plurality of narrowband optical signals transmitted from the
central office 62. Thus, the optical wavelength control system 60
insures that wavelength accuracy is maintained within the
system.
[0046] The present invention is not to be limited in scope by the
specific embodiments described herein. Indeed, various
modifications of the present invention, in addition to those
described herein, will be apparent to those of ordinary skill in
the art from the foregoing description and accompanying drawings.
Thus, such modifications are intended to fall within the scope of
the following appended claims. Further, although the present
invention has been described herein in the context of a particular
implementation in a particular environment for a particular
purpose, those of ordinary skill in the art will recognize that its
usefulness is not limited thereto and that the present invention
can be beneficially implemented in any number of environments for
any number of purposes. Accordingly, the claims set forth below
should be construed in view of the full breath and spirit of the
present invention as disclosed herein.
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