US 6,188,816 B1 · Filter topologies for optical add-drop multiplexers

Abstract

A filter topography is possible that can reduce the overall cost of a single Optical Add-Drop Multiplexer (OADM) or a series of OADMs that are within a network. The key is to have one of the wavelengths of a WDM signal being input to a filtering apparatus empty. The filtering apparatus can then with a reduced cost filter the received WDM signal such that a channel at a wavelength adjacent to the empty wavelength is removed and a channel is inserted at the previously empty wavelength. In one implementation of this topology within an OADM, a single filter can be used to perform both filtering operations due to the empty wavelength ensuring no corruption of the removed channel at the adjacent wavelength. In another implementation, the filtering operations are performed by two separate filters that each have asymmetrically reduced tolerances. In either case in which there is a reduced number of filters or reduced tolerances for those filters, a reduction in cost will be found.

Claims28

Dependent claims

A method of adding a first channel to and subtracting a second channel from a first Wavelength Division Multiplexed (WDM) signal which comprises a plurality of channels defined by a sequential set of wavelengths except for a first wavelength of the set which has been omitted, the method comprising:

receiving the first WDM signal that has no channel at the first wavelength;
filtering the first WDM signal such that a channel at a second wavelength adjacent to the first wavelength is subtracted from the first WDM signal and a channel is added at the first wavelength;
and
outputting a second WDM signal that has no channel at the second wavelength after the filtering of the first WDM signal.

1 more element

An Optical Add-Drop Multiplexer (OADM) arranged to receive a first Wavelength Division Multiplexed (WDM) signal which comprises a plurality of channels defined by a sequential set of wavelengths, the OADM comprising:

an initial filter that generates one of a plurality of intermediate WDM signals by filtering the first WDM signal such that a channel at a first wavelength is removed from the first WDM signal, leaving the first wavelength within the intermediate WDM signal empty;
N−1 intermediate filters that each generate one of the intermediate WDM signals by filtering the previously generated intermediate WDM signal such that a channel at a wavelength adjacent to a previously emptied wavelength is removed from the previously generated intermediate WDM signal and left empty while a channel is inserted at the previously emptied wavelength;
and
a final filter that generates a second WDM signal by filtering the previously generated intermediate WDM signal such that a channel is inserted at a wavelength that the previous additional filter had emptied;
wherein N is equal to the number of wavelengths within the sequential set of wavelengths that have channels removed and other channels inserted in order to generate the second WDM signal, N being greater than one.

2 more elements

Dependencies are inferred from the claim text.

Filter topologies for optical add-drop multiplexers

Life of this patent

Filter topologies for optical add-drop multiplexers

Life of this patent

Abstract

Claims28