# US 8,542,999 B2 · Minimizing bandwidth narrowing penalties in a wavelength selective switch optical network

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- Number: US 8,542,999 B2
- Document ID: US8542999B2
- Status: Granted
- Kind: B2
- Application number: 13/019,255
- Filed: 2011-02-01
- Published: 2012-08-02
- Granted: 2013-09-24
- Earliest claimed: 2011-02-01
- Assignees: Vello Systems, Inc.
- Applicants: Chris Wilhelm Barnard; Piotr Myslinski
- Inventors: Chris Wilhelm Barnard; Piotr Myslinski
- Web page: https://patentgrep.com/patent/US8542999B2

## CPC

- H04J 14/0212: {using optical switches or wavelength selective switches [WSS]}
- H04J 14/0204: {Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping}
- H04J 14/0205: {Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping}
- H04J 14/0206: {Express channels arrangements}
- H04J 14/0209: {Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers}
- H04J 14/02122: {Colourless, directionless or contentionless [CDC] arrangements}
- H04J 14/0256: {at the optical channel layer}
- H04Q 11/0005: {Switch and router aspects}
- H04Q 11/0062: {Network aspects}
- H04Q 2011/0009: {using wavelength filters}
- H04Q 2011/0016: {using wavelength multiplexing or demultiplexing}
- H04Q 2011/0086: {Network resource allocation, dimensioning or optimisation}
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W)

## Abstract

This invention relates to provisioning wavelength-selective switches and reconfigurable optical add-drop multiplexers to minimize the bandwidth narrowing effect from the optical filters. Novel architectures and methods are disclosed that can significantly reduce bandwidth-narrowing on channels in a reconfigurable WDM network where a large number of optical filter elements are cascaded. Instead of blocking unused channels as in the prior art, unused channels are selectively provisioned depending on the state of their adjacent channels. Unused adjacent channels of an active channel are provisioned to follow the same path as the active channels. As each channels is deployed, the channel frequency is selected so as to minimize bandwidth narrowing.

## Claims

### Claim 1

A system that provisions a channel on which a client signal will be transmitted along a path from a source node through at least one intermediate node before reaching a destination node of a WDM optical network, the system comprising:
(a) a signal channel transmitter that transmits a client signal among a plurality of nodes of the network on a signal channel having a predetermined frequency;
(b) an optical filter at each node along the path that is configured to reflect the state of the signal channel at that node; and
(c) a state table indicating, with respect to each node along the path, whether each of two channels adjacent to the signal channel is unused,
(d) wherein the optical filter at each node along the path is configured by setting the state of each unused adjacent channel to the same physical state as that of the signal channel, thereby effectively increasing the spectral passband of the client signal.

### Claim 2 (depends on 1)

The system of claim 1, wherein the physical state of the signal channel at the source node of the path is an “add” state, the physical state of the signal channel at each intermediate node of the path is a “pass through” state and the physical state of the signal channel at the destination node is a “blocking” state.

### Claim 3 (depends on 2)

The system of claim 2, wherein every channel is initially set to a default “blocking” state.

### Claim 4 (depends on 1)

The system of claim 1, wherein the state of each unused adjacent channel is set to a different logical state than that of the signal channel.

### Claim 5 (depends on 1)

The system of claim 1, wherein the level of attenuation of each unused adjacent channel is set to the same level of attenuation as that of the signal channel.

### Claim 6 (depends on 1)

The system of claim 1, wherein the optical filter at each node along the path is a wavelength selective switch.