WDM multiplexer

• US 6,256,431 B1
• Filed: 02/11/1999
• Issued: 07/03/2001
• Est. Priority Date: 02/11/1999
• Status: Expired due to Term

• Current Assignee: ECI Telecom Limited (Shaul Shani)
• Original Assignee: ECI Telecom Limited (Shaul Shani)
• Inventors: Mesh, Michael
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Nguyen, Tu T.
• Application Number:
  US09/248,919
• Time in Patent Office: 873 Days
• Field of Search: 385/24, 385/15, 385/27, 385/28, 385/39, 385/42, 385/37, 385/17, 385/18, 359/127, 359/130, 359/122, 359/123, 359/156, 359/192
• US Class Current: 385/24
• CPC Class Codes: G02B 6/12019 characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes coupling integrated waveguide to fibre G02B6/30, to optoelectronic element G02B6/42; monolithic integration of integrated waveguides with other optical elements G02B6/12004
• CPC Class Codes: G02B 6/12021 Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
• CPC Class Codes: G02B 6/29353 with a wavelength selective element in at least one light guide interferometer arm, e.g. grating, interference filter, resonator
• CPC Class Codes: G02B 6/29355 Cascade arrangement of interferometers
• CPC Class Codes: G02B 6/29383 Adding and dropping
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems

Abstract

An expandable multiplexer and method for adding additional channels per fiber in an optical communication system, the multiplexer including a wavelength multiplexer including at least two multiplexer input ports for combining a plurality of input wavelengths onto at least one multiplexer output port, and at least one wavelength filter including at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to one of the multiplexer input ports.

Claims

1. An expandable multiplexer for adding additional channels per fiber in an optical communication system, the multiplexer comprising:

a wavelength multiplexer comprising an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range and including at least two multiplexer input ports for combining a plurality of input wavelengths onto at least one multiplexer output port; and

at least one wavelength filter including at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to one of said multiplexer input ports.

2. The expandable multiplexer of claim 1, wherein:

said wavelength multiplexer includes an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range; and

said at least one wavelength filter includes a narrow band wavelength division multiplexer (WDM) filter located at a first input port of said AWG multiplexer for coupling wavelengths separated by said free space range entering said AWG multiplexer.

3. The expandable multiplexer of claim 2, wherein said wavelength multiplexer is a four channel multiplexer, and further including between one and three additional narrow band wavelength division multiplexer filters, each coupled to a different multiplexer input port of said AWG multiplexer, each for coupling two wavelengths separated by said free space range entering said port.

14. A method of expanding an optical communication system, the method comprising the steps of:

optically coupling a first and second expandable multiplexer, each according to claim 1, for optical communication over a plurality of wavelengths across at least one fiber; and

adding at least one wavelength filter for combining at least one additional wavelength onto an input port of said first expandable multiplexer and at least one wavelength filter for splitting said at least one additional wavelength from an output port of said second expandable multiplexer, wherein said expandable multiplexer includes an add and drop multiplexer, and the wavelength filter includes a pair of identical Bragg gratings resonant at a unique identical wavelength, associated with the add and drop multiplexer, wherein the step of adding includes;

connecting to said first add and drop multiplexer another add and drop multiplexer and associated pair of identical Bragg gratings resonant at a different identical wavelength.

15. The method of claim 14, wherein said step of adding includes adding at least one wavelength to said expandable multiplexer without disturbing any existing wavelength.

16. The method of claim 14, wherein said step of adding includes adding another add and drop multiplexer coupled to said add and drop multiplexer.

4. An expandable multiplexer for adding additional channels per fiber in an optical communication system, the multiplexer comprising:

a wavelength multiplexer including at least two multiplexer input ports for combining a plurality of input wavelengths onto at least one multiplexer output port; and

at least one wavelength filter including at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to one of said multiplexer input ports, wherein;

said wavelength multiplexer includes at least one add and drop multiplexer including two fibers coupled at two points; and

said first wavelength filter includes a pair of identical Bragg gratings resonant at a unique identical wavelength, each said Bragg grating disposed in one fiber of said add and drop multiplexer between said two points for adding and dropping said unique wavelength.

5. A communications system comprising:

a first expandable multiplexer including;

a first wavelength multiplexer comprising an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range and including at least two multiplexer input ports for combining a plurality of input wavelengths onto at least one multiplexer output port; and

at least one wavelength filter including at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to one of said multiplexer input ports; and

a second expandable multiplexer coupled for fiberoptic communication to said first expandable multiplexer including;

a second wavelength multiplexer comprising an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer and including at least one multiplexer input port for splitting a plurality of output wavelengths onto at least two multiplexer output ports; and

at least one wavelength filter including a filter input port for splitting at least two selected wavelengths from one of said multiplexer output ports onto at least two filter output ports.

6. The communications system of claim 5, wherein:

said first wavelength multiplexer includes an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range;

said at least one wavelength filter in said first expandable multiplexer includes a narrow band wavelength division multiplexer (WDM) filter, located at a first input port of said first AWG multiplexer for coupling wavelengths separated by said free space range entering said first AWG multiplexer;

said second wavelength multiplexer includes an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having said predefined free space range; and

said at least one wavelength filter in said second expandable multiplexer includes a narrow band wavelength division multiplexer (WDM) filter, located at a first output port of said second AWG multiplexer for splitting the wavelengths leaving said second AWG multiplexer.

7. The communications system of claim 6, further including:

up to three wavelength filters coupled to different input ports of said first AWG multiplexer, each for combining two wavelengths separated by said free space range onto said different input port of said first AWG multiplexer; and

up to three wavelength filters located at different output ports of said second AWG multiplexer, each for splitting two wavelengths leaving said different output port of second AWG multiplexer corresponding to said combined wavelengths.

8. A communications system comprising:

a first expandable multiplexer including;

a first wavelength multiplexer including at least two multiplexer input ports for combining a plurality of input wavelengths onto at least one multiplexer output port; and

at least one wavelength filter including at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to one of said multiplexer input ports; and

a second expandable multiplexer coupled for fiberoptic communication to said first expandable multiplexer including;

a second wavelength multiplexer including at least one multiplexer input port for splitting a plurality of output wavelengths onto at least two multiplexer output ports; and

at least one wavelength filter including a filter input port for splitting at least two selected wavelengths from one of said multiplexer output ports onto at least two filter output ports, wherein;

said first wavelength multiplexer includes a first add and drop multiplexer including two fibers coupled at two points, and said first wavelength filter includes a pair of identical Bragg gratings resonant at a first unique identical wavelength, each said Bragg grating disposed in one fiber of said add and drop multiplexer between said two points for adding and dropping said first unique wavelength; and

said second wavelength multiplexer includes a second add and drop multiplexer including two fibers coupled at two points, and said second wavelength filter includes a pair of identical Bragg gratings resonant at a second unique identical wavelength, each said Bragg grating disposed in one fiber of said add and drop multiplexer between said two points for adding and dropping said second unique wavelength;

said first wavelength multiplexer being coupled to said second wavelength multiplexer.

9. The communications system of claim 8, wherein said expandable multiplexer includes a plurality of add and drop multiplexers coupled to one another, each said add and drop multiplexer including two fibers coupled at two points, and an associated wavelength filter including a pair of identical Bragg gratings resonant at a unique identical wavelength, for adding and dropping said unique wavelength, each said Bragg grating disposed in one fiber of said add and drop multiplexer between said two points.

10. The communications system of claim 9, further comprising a fiberoptic circulator coupling said multiplexer input and said multiplexer output in a loop.

11. A method of expanding an optical communication system, the method comprising the steps of:

optically coupling a first and second expandable multiplexer, each including a wavelength multiplexer comprising an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range and having at least two input ports for combining a plurality of input wavelengths onto at least one multiplexer output port, and a wavelength filter having at least two filter input ports for combining at least two selected wavelengths onto at least one filter output port coupled to at least one of said multiplexer input ports, for optical communication over a plurality of wavelengths across at least one fiber; and

adding at least one wavelength filter for combining at least one additional wavelength onto an input port of said first expandable multiplexer and at least one wavelength filter for splitting said at least one additional wavelength from an output port of said second expandable multiplexer.

12. The method of claim 11, wherein said first and second expandable multiplexers each includes an Arrayed Waveguide Grating (AWG) multiplexer/demultiplexer having a predefined free space range, and wherein said step of adding includes:

inserting two corresponding narrow band wavelength division multiplexer (WDM) filters, one located at a first input port of said first AWG multiplexer for combining wavelengths separated by said free space range entering said first AWG multiplexer, and one located at a first output port of said second AWG multiplexer for splitting said combined wavelengths leaving said second AWG multiplexer.

13. The method of claim 12, further corrprising the step of inserting a third narrow band wavelength division multiplexer (WDM) filter at a second input port of said first AWG multiplexer for coupling two different wavelengths separated by said free space range entering said first AWG multiplexer onto a single signal;

and inserting a fourth narrow band wavelength division multiplexer filter at a second output port of the second AWG multiplexer for splitting said combined different wavelengths leaving said second AWG multiplexer.