Optical filtering by using an add-drop node

• US 20040234194A1
• Filed: 06/24/2004
• Published: 11/25/2004
• Est. Priority Date: 07/16/2001
• Status: Active Grant

• Current Assignee: Lumentis AB (Infinera Corp.)
• Original Assignee: Lumentis AB (Infinera Corp.)
• Inventors: Persson, Ulf
• Granted Patent: US 7,113,662 B2
• Time in Patent Office: Days
• US Class Current: 385/24
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0283 WDM ring architectures

Abstract

The present invention relates to a method using a node, a system comprising a node and a node for filtering signals in a wavelength division multiplexing (WDM) optical communications system, especially for re-configurably adding and dropping signals to and from an optical fibre path. The node comprising a drop filter, an add filter, a signal channel receiver, and a signal channel transmitter each being connected to a switch for signal channel relaying between said network, and signal channel dropping and adding from and to said network. The node provides low loss for relayed signals by allowing the drop filter to have a low crosstalk isolation, and provides high crosstalk isolation for dropped signal channels by connecting said receiver to the switch through an additional filter with high filtering characteristics for at least one predetermined signal.

Claims

1. An add-drop node for wavelength division multiplexing optical signal transmission on an optical fiber network between multiple add-drop nodes, said node comprising a drop filter (78, 84, 85, 88), an add filter (65, 84, 86, 89), a signal channel receiver (72, 93), and a signal channel transmitter (71, 92) each being connected to a switch (68) for signal channel relaying between said network, and signal channel dropping and adding from and to said network, characterized in providing low loss for relayed signals by allowing said drop filter having a low crosstalk isolation, and providing high crosstalk isolation for dropped signal channels by connecting said receiver to the switch through an additional filter (79, 90) with high filtering characteristics for at least one predetermined signal channel of said signal.

2. An add-drop node according to claim 1, characterized in that the drop filter is a channel drop filter for dropping signals on a single channel.

3. An add-drop node according to claim 1, characterized in that the drop filter is a band drop filter for dropping signals on two or more channels and the additional filter form a part of a demultiplexer.

4. A system comprising at least one add-drop node for wavelength division multiplexing optical signal transmission on an optical fiber network between other add-drop nodes, said at least one node comprising a drop filter (78, 84, 85, 88), an add filter (65, 84, 86, 89), a signal channel receiver (72, 93), and a signal channel transmitter (71, 92) each being connected to a switch (68) for signal channel relaying between said network, and signal channel dropping and adding from and to said network, characterized in providing low loss for relayed signals by allowing said drop filter having a low crosstalk isolation, and providing high crosstalk isolation for dropped signal by connecting said receiver to the switch through an additional filter (79, 90) with high filtering characteristics for at least one predetermined signal channel of said signal.

5. A system according to claim 4 characterised in that the drop filter is a channel drop filter for dropping signals on a single channel.

6. A system according to claim 4 characterised in that the drop filter is a band drop filter for dropping signals on two or more channels and the additional filter form a part of a demultiplexer.

7. A method using an add-drop node for wavelength division multiplexing optical signal transmission on an optical fiber network between multiple add-drop nodes, said node comprising a low loss drop filter (78, 84, 85, 88), an add filter (65, 84, 86, 89), a signal channel receiver (72, 93), and a signal channel transmitter (71, 92) each being connected to a switch (68) for signal channel relaying between said network, and signal channel dropping and adding from and to said network, characterized in that it comprises the steps of:

providing low loss for relayed signals by allowing said drop filter having a low crosstalk isolation; and

providing high crosstalk isolation for dropped signal by connecting said receiver to the switch through an additional filter (79, 90) with high filtering characteristics for at least one predetermined signal channel of said signal.

8. A method according to claim 7 characterised in that the drop filter is a channel drop filter for dropping signals on a single channel.

9. A method according to claim 7 characterised in that the drop filter is a band drop filter for dropping signals on two or more channels and the additional filter form a part of a demultiplexer.