Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2001-03-06
2002-09-10
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06449068
ABSTRACT:
FIELD OF THE INVENTION
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
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.
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.
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.
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.
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.
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.
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.
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 fo
Emkey William L.
Turner Ian
Wade Robert K.
Hunton & Williams
LightChip, Inc.
Pascal Leslie
Phan Hanh
LandOfFree
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