Optical wavelength demultiplexer having optical interference filters connected in cascade

• US 9,780,903 B2
• Filed: 01/27/2015
• Issued: 10/03/2017
• 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
• Primary Examiner(s): VANDERPUYE, KENNETH N
• Assistant Examiner(s): Alagheband, Abbas H
• Application Number:
  US14/606,676
• Publication Number:
  US 20150295672A1
• Time in Patent Office: 980 Days
• Field of Search: 398 65, 398 91, 398 45, 398215, 398183, 385 12, 385 14- 15, 385 22, 385 37, 385 42, 385 39
• 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 transmitting a first predetermined wavelength component and removing a component other than the transmitted first wavelength component from the first wavelength band; and

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

wherein each of said wavelength demultiplexing device and said first and second wavelength filters is a multimode interferometer (MMI),

each of said first wavelength filter and said second wavelength filter comprises a single wavelength sub-filter or two or more wavelength sub-filters connected in a cascade of a predetermined number of stages to output an output light having a corresponding one of the first wavelength component and the second wavelength component,

said first wavelength filter includes said wavelength sub-filters in plural, said plural wavelength sub-filters being connected in a cascade of a first predetermined number of stages to output the output light having the first wavelength component,

said second wavelength filter includes said wavelength sub-filters in plural, said plural wavelength sub-filters being connected in a cascade of a second predetermined number of stages to output the output light having the second wavelength component,

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

₃ of 1490 nm and a wavelength λ

₄ of 1550 nm,

said first wavelength filter removes 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, and

said plural wavelength sub-filters in said second wavelength filter comprise 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.

2. The optical wavelength demultiplexer in accordance with claim 1, 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.