OPTICAL WAVELENGTH DEMULTIPLEXER HAVING OPTICAL INTERFERENCE FILTERS CONNECTED IN CASCADE

• US 20150295672A1
• Filed: 01/27/2015
• Published: 10/15/2015
• Est. Priority Date: 04/11/2014
• Status: Active Grant

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: OKAYAMA, Hideaki
• Granted Patent: US 9,780,903 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/29344 operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI
• CPC Class Codes: G02B 6/29355 Cascade arrangement of interferometers
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29397 Polarisation insensitivity
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems

Abstract

An optical wavelength demultiplexer includes a wavelength demultiplexing device, a first wavelength filter and a first- and second-stage wavelength sub-filters. The wavelength demultiplexing device demultiplexes an input light into a first wavelength band including wavelengths λ₁ and λ₂ in the vicinity of 1310 nm and a second wavelength band including a wavelength λ₃ of 1490 nm and a wavelength λ₄ of 1550 nm to output. The first-stage wavelength sub-filter removes the wavelength λ₂ longer than 1310 nm from the second wavelength band and transmits the wavelength λ₃ of 1490 nm. The second-stage wavelength sub-filter removes the wavelength λ₄ of 1550 nm and outputs the wavelength λ₃ of 1490 nm, which is the remainder of the selected lights, with a sufficient wavelength spectral purity.

Claims

1. An optical wavelength demultiplexer comprising:

a wavelength demultiplexing device having a first and a second output port for demultiplexing an input light received on an input port into a first wavelength band and a second wavelength band, different from the first wavelength band, to output wavelength components of the first wavelength band on the first output port and the second wavelength band from the second output port;

a first wavelength filter connected to the first output port for selecting a first predetermined wavelength component and removing a component other than the selected first wavelength component from the first wavelength band; and

a second wavelength filter connected to the second output port for selecting a second predetermined wavelength component and removing a component other than the selected second wavelength component from the second wavelength band,

each of said first wavelength filter and said second wavelength filter comprising at least one wavelength sub-filter connected in cascade of stages required in number for obtaining an output light which is to be selected with a sufficient wavelength spectrum purity from corresponding one of the first wavelength band and the second wavelength band.

2. The optical wavelength demultiplexer in accordance with claim 1, wherein said at least one wavelength sub-filter is provided in plural, said plural wavelength sub-filters being connected in cascade of a corresponding plurality of stages.

3. The optical wavelength demultiplexer in accordance with claim 1, wherein

said first wavelength filter has said at least one wavelength sub-filter provided in plural, said plural wavelength sub-filters being connected in cascade of a corresponding plurality of stages required in number for obtaining the output light from the first wavelength band,

said second wavelength filter having said at least one wavelength sub-filter provided in plural, said plural wavelength sub-filters being connected in cascade of a corresponding plurality of stages required in number for obtaining the output light from the second wavelength band.

4. The optical wavelength demultiplexer in accordance with claim 3, wherein

the first wavelength band is in a vicinity of a wavelength of 1310 nm, and includes wavelength λ

₁ on a shorter wavelength side and wavelength λ

₂ on a longer wavelength side than the wavelength of 1310 nm, which falls between the wavelength λ

₁ and the wavelength λ

₂,

the second wavelength band including a wavelength λ

₃ of 1490 nm and a wavelength λ

₄ of 1550 nm,

said first wavelength filter removing the wavelength λ

₄ of 1550 nm from the wavelength component of the first wavelength band and transmitting light of the wavelength of 1310 nm,

said plural wavelength sub-filters in said second wavelength filter comprising a first wavelength sub-filter for removing the wavelength λ

₂ on the longer wavelength side from the wavelength component of the second wavelength band and transmitting the wavelength λ

₃ of 1490 nm, and a second wavelength sub-filter connected to said first wavelength sub-filter in cascade for removing the wavelength λ

₄ of 1550 nm and transmitting the wavelength λ

₃ of 1490 nm.

5. The optical wavelength demultiplexer in accordance with claim 1, wherein said wavelength demultiplexing device and said first and second wavelength filters are of a Mach-Zehnder interferometer comprising a directional optical coupler.

6. The optical wavelength demultiplexer in accordance with claim 1, wherein said wavelength demultiplexing device and said first and second wavelength filters are of a multimode interferometer (MMI).

7. The optical wavelength demultiplexer in accordance with claim 5, wherein said Mach-Zehnder interferometer comprises two optical paths causing an interference phenomenon of light, the two optical paths including interference waveguides whose waveguide widths are different from each other,

each of the interference waveguides and a waveguide constituting the directional optical coupler having a waveguide width set such as to attain a wave-guiding characteristic of polarization independency.

8. The optical wavelength demultiplexer in accordance with claim 6, wherein said multimode interferometer comprises a main MMI waveguide, and a tapering waveguide provided in a preceding stage of the main MMI waveguide to form the input port, as well as a tapering waveguide for adjusting a waveguide width, a waveguide for connection, and a tapering waveguide forming the output port, which are provided in a subsequent stage of the main MMI waveguide,

the main MMI waveguide having a waveguide width set so as to attain a wave-guiding characteristic of polarization independency.