WO2008127067A1 - Waveguide type optical splitter having the asymmetrical mach zhender structure of multimode type - Google Patents

Waveguide type optical splitter having the asymmetrical mach zhender structure of multimode type Download PDF

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Publication number
WO2008127067A1
WO2008127067A1 PCT/KR2008/002134 KR2008002134W WO2008127067A1 WO 2008127067 A1 WO2008127067 A1 WO 2008127067A1 KR 2008002134 W KR2008002134 W KR 2008002134W WO 2008127067 A1 WO2008127067 A1 WO 2008127067A1
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WO
WIPO (PCT)
Prior art keywords
optical splitter
input
waveguide type
coupler
type optical
Prior art date
Application number
PCT/KR2008/002134
Other languages
French (fr)
Inventor
Seung-Chan Kwak
Hyung-Myung Moon
Jin-Bong Kim
Original Assignee
Ppi Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ppi Co., Ltd. filed Critical Ppi Co., Ltd.
Priority to CN2008800123019A priority Critical patent/CN101657746B/en
Publication of WO2008127067A1 publication Critical patent/WO2008127067A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/2935—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
    • G02B6/0288—Multimode fibre, e.g. graded index core for compensating modal dispersion
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12133—Functions
    • G02B2006/12154—Power divider

Definitions

  • the FTTH technology relates to facilities including a transmitting apparatus and a transmitting medium to connect networks into users.
  • High speed access and transport are typically referred to as a technique for providing a utilization band of a few Mb/s to users.
  • a passive optical network (PON) method used to establish the FTTH, is applied to a network for connecting a center office as a service provider to subscribers as customers using only passive optical devices within the FTTH.
  • PON passive optical network
  • data signals including multiplexed voice, data, or video service are simultaneously transmitted. It is a waveguide type optical splitter of the PON system, which effectively split optical power.
  • optical splitters also referred to as optical couplers, may be classified into a bulk type, a fiber type, and a waveguide type optical splitters.
  • the bulk type optical splitter including combinations of a microlens, a prism, and an interference film filter, can provide a device with less wavelength dependence, but assembly adjustment takes time, or a problem relating to reliability, costs, or the size of a device arises.
  • the fiber type optical splitter formed of optical fibers through grinding, welding, and extension processes, can provide a device with less wavelength dependence, but high technology is required and productivity is low. Thus, the fiber type optical splitter is not suitable for mass production.
  • the waveguide type optical splitter can be formed on a planar substrate in a batch type through a photolithography process with a designed mask having a shape of the optical splitter, to achieve mass production.
  • the waveguide type optical splitter has been noted as a promising technology in productivity and high-density.
  • the waveguide type optical splitter has limitations with great polarization loss and great wavelength dependence according to process variables.
  • the waveguide type optical splitter applied to a PON network should be formed to minimize optical power loss and polarization loss depending on the number of split waveguides and have uniform power values within wavelength regions used in optical communications.
  • An object of the present invention is to provide a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes, which is designed to bring asymmetric Mach-Zehnder couplers in contact with each other and compensate for great wavelength dependence and polarization loss.
  • evanescent wave coupling occurs between native modes of a plurality of optical couplers to cause optical output coupling, by bring arrangement of the optical couplers matching with characteristics near an optical wavelength unit.
  • a portion of input power of the coupler can be delivered into another coupler.
  • a distribution-coupling guide type optical modulator can be realized by making the efficiency of the optical coupler modulatable.
  • a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes, the optical splitter including two couplers and two connection waveguides between two input ends and two output ends, wherein the couplers include an input coupler and an output coupler, and each of the couplers has an integrally attached side.
  • the couplers may include a coupler width extension portion G between the input ends and the output ends to extend a width connected to the input ends and the output ends.
  • the coupler width extension portion G may have a width ranging from 0.5 ⁇ m to 1.5 ⁇ m.
  • a length of the input coupler and a length of the output coupler may be respectively in a range from 180 ⁇ m to 220 ⁇ m and a range from 380 ⁇ m to 420 ⁇ m, or the length of the input coupler and the length of the output coupler may be respectively in a range from 380 ⁇ m to 420 ⁇ m and a range from 180 ⁇ m to 220 ⁇ m.
  • the connection waveguides may have a difference ranging from 500 run to 550 nm in length therebetween.
  • FIG. 1 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention.
  • FIG.2 is an enlarged view of a portion D of FIG. 1.
  • FIG.3 is a cross-sectional view taken along line A-A of FIG. 1.
  • FIG.4 is a cross-sectional view taken along line B-B of FIG. 1.
  • FIG. 5 is a cross-sectional view taken along line C-C of FIG. 1.
  • FIGs. 6 and 7 are views illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to another embodiment of the present invention. ⁇ 19> FIGs.
  • FIG. 8 and 9 are graphs illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X2 multiple modes according to an embodiment of the present invention.
  • FIG. 10 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X16 multiple modes according to an embodiment of the present invention.
  • FIG. 11 is a view illustrating a waveguide-type optical splitter having an asymmetric Mach Zehnder structure with 2X32 multiple modes according to an embodiment of the present invention.
  • FIG. 10 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X16 multiple modes according to an embodiment of the present invention.
  • FIG. 11 is a view illustrating a waveguide-type optical splitter having an asymmetric Mach Zehnder structure with 2X32 multiple modes according to an embodiment of the present invention.
  • FIG. 10 is a view illustrating a waveguide
  • FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to a first input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention.
  • FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to a second input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention.
  • FIG. 14 is a graph illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X32 multiple modes according to an embodiment of the present invention. [Best Mode]
  • FIG. 1 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention
  • FIG. 2 is an enlarged view of a portion D of FIG. 1
  • FIG. 3 is a cross-sectional view taken along line A-A of FIG. 1
  • FIG. 4 is a cross-sectional view taken along line B-B of FIG. 1
  • FIG. 5 is a cross-sectional view taken along line C-C of FIG.
  • FIGs. 6 and 7 are views illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to another embodiment of the present invention
  • FIG. 8 and 9 are graphs illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X2 multiple modes according to an embodiment of the present invention
  • FIG. 10 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X16 multiple modes according to an embodiment of the present invention
  • FIG. 11 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X32 multiple modes according to an embodiment of the present invention
  • FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to a first input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention
  • FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to a second input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention
  • FIG. 14 is a graph illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure with 2X32 multiple modes according to an embodiment of the present invention.
  • an asymmetric Mach Zehnder optical interferometer circuit having two optical waveguide directional couplers is disposed on a substrate and configured to appropriately adjust the difference in optical path length between the optical waveguide directional couplers and attach the optical waveguide directional couplers to each other.
  • the optical waveguide directional couplers are disposed between two input ends and two output ends.
  • the input ends include a first input waveguide 10 and a second input waveguide 20, and the output ends include a first output waveguide 15 and a second output waveguide 25.
  • An input coupler 40, connection waveguides 30 and 35, and an output coupler 45 are disposed between the input ends and the output ends.
  • a length L of the coupler may range from 180 ⁇ m to 220 ⁇ m or from 380 ⁇ m to 420 ⁇ m. That is, Ll may range from 180 ⁇ m to 220 ⁇ m, and L2 ranges from 380 ⁇ m to 420 ⁇ m. Alternately, L2 may range from 180 ⁇ m to 220 ⁇ m, and Ll ranges from 380 ⁇ m to 420 ⁇ m.
  • the coupler width extension portion G may range from 0.5 ⁇ m to 1.5 ⁇ m.
  • connection waveguides 30 and 35 have an asymmetric arrangement.
  • the second connection waveguide 35 has a length WL+ ⁇ WL that is greater than the length WL by ⁇ WL.
  • the waveguide type optical splitter having the asymmetric Mach Zehnder structure according to the present invention includes a silica substrate 50, a silica glass thin layer 55, and core thin layers (SiO 2 -GeO 2 ) 10, 20, 30, 35, and 40, as illustrated in FIGs 3 through 5.
  • the first and the second input waveguides 10 and 20 are spaced apart from each other as illustrated in FIG. 3, the cross-sectional view (taken along the line A-A of FIG. 1).
  • the input coupler 40 includes the first and the second input waveguides 10 and 20 attached to each other through their sides as illustrated in FIG. 4, the cross-sectional view (taken along the line B-B of FIG. 1).
  • the first and the second connection waveguides 30 and 35 are also spaced apart from each other as illustrated in FIG. 5, the cross-sectional view (taken along the line C-C of FIG. 1).
  • the waveguide type optical splitter having the asymmetric Mach Zehnder structure according to the present invention is designed to have a transmittance of 50 ⁇ 10 % in a wavelength ranging from 1.25 ⁇ m to 1.65 ⁇ m.
  • the first and the second input waveguides 10 and 20 are spaced 127 ⁇ m from each other, and the first and the second output waveguides 15 and 25 are spaced 250 ⁇ m from each other .
  • the Mach Zehnder optical interferometer circuit of the optical waveguides includes a SiO 2 based layer having GeO 2 for increasing a transmittance on a silica substrate and has a size of approximately 6 ⁇ mx ⁇ ⁇ m, with a difference ranging from approximately 0.4 delta% to approximately 0.45 delta% in a transmittance between the optical waveguides and the substrate.
  • the input coupler 40 and the output coupler 45 have length O
  • the coupler width extension portion G where the waveguides are split or coupled has a width design value of 1.2 ⁇ m.
  • the first and the second connection waveguides 30 and 35 having the difference of ⁇ WL in length therebetween, should have an optimized design value required for an even splitting of 50:50 in a transmittance, like the couplers.
  • the length ⁇ WL is 525 nm.
  • FIGs. 8 and 9 are graphs each illustrating optical loss and polarization loss depending on wavelengths for a 2X2 optical splitter.
  • a ratio in an optical power between output ends was approximately 50:50 in a wide wavelength range, depending on positions of input ends.
  • the polarization loss was 0.15 dB or less in a wide wavelength range through a test.
  • FIG. 10 is a plan view illustrating an optical splitter with 2x16 channels, which includes the waveguide type optical splitter having the asymmetric Mach Zehnder structure and multiple modes according to the embodiment of the present invention.
  • FIG. 11 is a plan view illustrating an optical splitter with 2X32 channels.
  • FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to the first input waveguide 10
  • FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to the second input waveguide 20.
  • FIG. 14 is a graph illustrating output loss and polarization loss depending on wavelengths of the optical splitter with 2 X32 channels. Optical power values of output ends were evenly distributed in a wide wavelength range, depending on positions of input ends. Also, polarization loss was 0.2 dB or less in a wide wavelength range.
  • ⁇ 4i> As described above, according to the present invention, in the optical splitter having the two input ends with the asymmetric Mach Zehnder structure, when the couplers has no gap therebetween, even transmittance without being sensitive to wavelengths and less polarization loss can be achieved in a wide wavelength range. Thus, an optical device including the effective optical splitter can be manufactured while increasing the number of channels.

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Abstract

The present invention relates to an optical waveguide type splitter used in optical communication fields, and more particularly, to a waveguide type optical splitter having an asymmetric Mach Zehnder structure, which has two input ends, 2xN multiple modes (N= 2, 4, 8, 16, 32, and 64), and uniform values with less optical power and polarization dependence when optical power input through the input end is output through an output end within a wide wavelength range, by bringing asymmetric directional couplers in contact with each other. The waveguide type optical splitter includes two couplers and two connection waveguides between two input ends and two output ends, wherein the couplers include an input coupler and an output coupler, and each of the couplers has an integrally attached side.

Description

[DESCRIPTION] [Invention Title]
WAVEGUIDE TYPE OPTICAL SPLITTER HAVING THE ASYMMETRICAL MACH ZHENDER STRUCTURE OF MULTIMODE TYPE [Technical Field]
<i> The present invention relates to an optical waveguide type splitter used in optical communication fields, and more particularly, to a waveguide type optical splitter having an asymmetric Mach Zehnder structure, which has two input ends, 2XN multiple modes (N= 2, 4, 8, 16, 32, and 64), and uniform values with less optical power and polarization dependence when optical power input through the input end is output through an output end within a wide wavelength range, by bringing asymmetric directional couplers in contact with each other. [Background Art]
<2> As the number of wideband multimedia services including the Internet increases, advanced networks have become most important in telecommunication fields, and fiber to the home (FTTH) technology is a key to the advanced networks.
<3> The FTTH technology relates to facilities including a transmitting apparatus and a transmitting medium to connect networks into users. High speed access and transport are typically referred to as a technique for providing a utilization band of a few Mb/s to users. A passive optical network (PON) method, used to establish the FTTH, is applied to a network for connecting a center office as a service provider to subscribers as customers using only passive optical devices within the FTTH. According to the PON method, data signals including multiplexed voice, data, or video service are simultaneously transmitted. It is a waveguide type optical splitter of the PON system, which effectively split optical power.
<4> For a network designer to realize a more easy, stable, and effective PON system, an optical splitter having two input ends is required, thus monitoring the system and achieving effective backup against short of a line. <5> Optical splitters, also referred to as optical couplers, may be classified into a bulk type, a fiber type, and a waveguide type optical splitters. The bulk type optical splitter, including combinations of a microlens, a prism, and an interference film filter, can provide a device with less wavelength dependence, but assembly adjustment takes time, or a problem relating to reliability, costs, or the size of a device arises. The fiber type optical splitter, formed of optical fibers through grinding, welding, and extension processes, can provide a device with less wavelength dependence, but high technology is required and productivity is low. Thus, the fiber type optical splitter is not suitable for mass production. The waveguide type optical splitter can be formed on a planar substrate in a batch type through a photolithography process with a designed mask having a shape of the optical splitter, to achieve mass production. Thus, the waveguide type optical splitter has been noted as a promising technology in productivity and high-density. However, the waveguide type optical splitter has limitations with great polarization loss and great wavelength dependence according to process variables.
<6> In addition, the waveguide type optical splitter applied to a PON network should be formed to minimize optical power loss and polarization loss depending on the number of split waveguides and have uniform power values within wavelength regions used in optical communications. [Disclosure] [Technical Problem]
<7> The present invention has been made in an effort to solve the above- described problems of the related art. An object of the present invention is to provide a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes, which is designed to bring asymmetric Mach-Zehnder couplers in contact with each other and compensate for great wavelength dependence and polarization loss.
<8> In other words, evanescent wave coupling occurs between native modes of a plurality of optical couplers to cause optical output coupling, by bring arrangement of the optical couplers matching with characteristics near an optical wavelength unit. Thus, a portion of input power of the coupler can be delivered into another coupler. A distribution-coupling guide type optical modulator can be realized by making the efficiency of the optical coupler modulatable.
[Technical Solution]
<9> To achieve the objects of the present invention, there is provided a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes, the optical splitter including two couplers and two connection waveguides between two input ends and two output ends, wherein the couplers include an input coupler and an output coupler, and each of the couplers has an integrally attached side.
<io> The couplers may include a coupler width extension portion G between the input ends and the output ends to extend a width connected to the input ends and the output ends. The coupler width extension portion G may have a width ranging from 0.5 μm to 1.5 μm.
<π> Also, a length of the input coupler and a length of the output coupler may be respectively in a range from 180 μm to 220 μm and a range from 380 μm to 420 μm, or the length of the input coupler and the length of the output coupler may be respectively in a range from 380 μm to 420 μm and a range from 180 μm to 220 μm. The connection waveguides may have a difference ranging from 500 run to 550 nm in length therebetween.
[Description of Drawings] <13> FIG. 1 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention.
<i4> FIG.2 is an enlarged view of a portion D of FIG. 1. <i5> FIG.3 is a cross-sectional view taken along line A-A of FIG. 1. <16> FIG.4 is a cross-sectional view taken along line B-B of FIG. 1. <i7> FIG. 5 is a cross-sectional view taken along line C-C of FIG. 1. <i8> FIGs. 6 and 7 are views illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to another embodiment of the present invention. <19> FIGs. 8 and 9 are graphs illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X2 multiple modes according to an embodiment of the present invention. <20> FIG. 10 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X16 multiple modes according to an embodiment of the present invention. <2i> FIG. 11 is a view illustrating a waveguide-type optical splitter having an asymmetric Mach Zehnder structure with 2X32 multiple modes according to an embodiment of the present invention. <22> FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to a first input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention. <23> FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to a second input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention. <24> FIG. 14 is a graph illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X32 multiple modes according to an embodiment of the present invention. [Best Mode]
<25> Hereinafter, a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to the present invention will now be described with reference to the accompanying drawing.
<26> FIG. 1 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention; FIG. 2 is an enlarged view of a portion D of FIG. 1; FIG. 3 is a cross-sectional view taken along line A-A of FIG. 1; FIG. 4 is a cross-sectional view taken along line B-B of FIG. 1; FIG. 5 is a cross-sectional view taken along line C-C of FIG. Il FIGs. 6 and 7 are views illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to another embodiment of the present invention; FIGs. 8 and 9 are graphs illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X2 multiple modes according to an embodiment of the present invention; FIG. 10 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X16 multiple modes according to an embodiment of the present invention; FIG. 11 is a view illustrating a waveguide type optical splitter having an asymmetric Mach Zehnder structure and 2X32 multiple modes according to an embodiment of the present invention; FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to a first input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention; FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to a second input waveguide of a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to an embodiment of the present invention; and FIG. 14 is a graph illustrating output loss and polarization loss depending on an input position of a waveguide type optical splitter having an asymmetric Mach Zehnder structure with 2X32 multiple modes according to an embodiment of the present invention.
<27> As illustrated in FIGs. 1 through 7, in a waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes according to the preferred embodiments of the present invention, an asymmetric Mach Zehnder optical interferometer circuit having two optical waveguide directional couplers is disposed on a substrate and configured to appropriately adjust the difference in optical path length between the optical waveguide directional couplers and attach the optical waveguide directional couplers to each other. The optical waveguide directional couplers are disposed between two input ends and two output ends. Thus, optical distribution is achieved at a ratio of 50:50 from the output ends, and polarization loss and wavelength dependence in a wide wavelength range are reduced.
<28> That is, the input ends include a first input waveguide 10 and a second input waveguide 20, and the output ends include a first output waveguide 15 and a second output waveguide 25. An input coupler 40, connection waveguides 30 and 35, and an output coupler 45 are disposed between the input ends and the output ends.
<29> The input coupler 40 and the output coupler 45 have integrally attached sides, as illustrated in FIG. 2. Also, a coupler width extension portion G for extending the widths of the couplers is further provided. A length L of the coupler may range from 180 μm to 220 μm or from 380 μm to 420 μm. That is, Ll may range from 180 μm to 220 μm, and L2 ranges from 380 μm to 420 μm. Alternately, L2 may range from 180 μm to 220 μm, and Ll ranges from 380 μm to 420 μm. The coupler width extension portion G may range from 0.5 μm to 1.5 μm.
<30> The connection waveguides 30 and 35 have an asymmetric arrangement. When the first connection waveguide 30 has a length WL, the second connection waveguide 35 has a length WL+ΔWL that is greater than the length WL by ΔWL. <3i> The waveguide type optical splitter having the asymmetric Mach Zehnder structure according to the present invention includes a silica substrate 50, a silica glass thin layer 55, and core thin layers (SiO2-GeO2) 10, 20, 30, 35, and 40, as illustrated in FIGs 3 through 5. In other words, the first and the second input waveguides 10 and 20 are spaced apart from each other as illustrated in FIG. 3, the cross-sectional view (taken along the line A-A of FIG. 1). The input coupler 40 includes the first and the second input waveguides 10 and 20 attached to each other through their sides as illustrated in FIG. 4, the cross-sectional view (taken along the line B-B of FIG. 1). The first and the second connection waveguides 30 and 35 are also spaced apart from each other as illustrated in FIG. 5, the cross-sectional view (taken along the line C-C of FIG. 1).
<32> The waveguide type optical splitter having the asymmetric Mach Zehnder structure according to the present invention is designed to have a transmittance of 50 ± 10 % in a wavelength ranging from 1.25 μm to 1.65 μ m.
<33> According to the embodiment of the present invention, the first and the second input waveguides 10 and 20 are spaced 127 μm from each other, and the first and the second output waveguides 15 and 25 are spaced 250 μm from each other .
<34> The Mach Zehnder optical interferometer circuit of the optical waveguides includes a SiO2 based layer having GeO2 for increasing a transmittance on a silica substrate and has a size of approximately 6 μmxβ μm, with a difference ranging from approximately 0.4 delta% to approximately 0.45 delta% in a transmittance between the optical waveguides and the substrate.
<35> Also, there are various ratios in optical power depending on the lengths of the input coupler 40 and the output coupler 45, thus an optimized design value is required for effective optical splitting. According to the present invention, the input coupler 40 and the output coupler 45 have length O
design values of 194 μm and 400 μm, respectively, for an even splitting of 50:50 in a transmittance. Also, the coupler width extension portion G where the waveguides are split or coupled, has a width design value of 1.2 μm.
<36> Also, the first and the second connection waveguides 30 and 35, having the difference of ΔWL in length therebetween, should have an optimized design value required for an even splitting of 50:50 in a transmittance, like the couplers. According to this embodiment, the length ΔWL is 525 nm.
<37> FIGs. 8 and 9 are graphs each illustrating optical loss and polarization loss depending on wavelengths for a 2X2 optical splitter. A ratio in an optical power between output ends was approximately 50:50 in a wide wavelength range, depending on positions of input ends. Also, the polarization loss was 0.15 dB or less in a wide wavelength range through a test.
<38> FIG. 10 is a plan view illustrating an optical splitter with 2x16 channels, which includes the waveguide type optical splitter having the asymmetric Mach Zehnder structure and multiple modes according to the embodiment of the present invention. FIG. 11 is a plan view illustrating an optical splitter with 2X32 channels.
<39> FIG. 12 is a graph illustrating output loss depending on wavelengths of light sources input to the first input waveguide 10, and FIG. 13 is a graph illustrating output loss depending on wavelengths of light sources input to the second input waveguide 20. FIG. 14 is a graph illustrating output loss and polarization loss depending on wavelengths of the optical splitter with 2 X32 channels. Optical power values of output ends were evenly distributed in a wide wavelength range, depending on positions of input ends. Also, polarization loss was 0.2 dB or less in a wide wavelength range.
<40> While this invention has been particularly shown and described with reference to the embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The embodiment should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.
[Industrial Applicability]
<4i> As described above, according to the present invention, in the optical splitter having the two input ends with the asymmetric Mach Zehnder structure, when the couplers has no gap therebetween, even transmittance without being sensitive to wavelengths and less polarization loss can be achieved in a wide wavelength range. Thus, an optical device including the effective optical splitter can be manufactured while increasing the number of channels.
<42>

Claims

[CLAIMS] [Claim 1]
<44> A waveguide type optical splitter having an asymmetric Mach Zehnder structure and multiple modes, the optical splitter comprising two couplers and two connection waveguides between two input ends and two output ends, <45> wherein the couplers include an input coupler and an output coupler, and each of the couplers has an integrally attached side.
[Claim 2]
<46> The waveguide type optical splitter of claim 1, wherein the couplers comprises a coupler width extension portion (G) between the input ends and the output ends to extend a width connected to the input ends and the output ends.
[Claim 3]
<47> The waveguide type optical splitter of claim 2, wherein the coupler width extension portion (G) has a width ranging from 0.5 μm to 1.5 μm.
[Claim 4]
<48> The waveguide type optical splitter of any one of claims 1 through 3, wherein a length of the input coupler and a length of the output coupler are respectively in a range from 180 μm to 220 μm and a range from 380 μm to 420 μm, or the length of the input coupler and the length of the output coupler are respectively in a range from 380 μm to 420 μm and a range from 180 μm to 220 μm. [Claim 5]
<49> The waveguide type optical splitter of claim 4, wherein the connection waveguides have a difference ranging from 500 nm to 550 nm in length therebetween.
PCT/KR2008/002134 2007-04-16 2008-04-16 Waveguide type optical splitter having the asymmetrical mach zhender structure of multimode type WO2008127067A1 (en)

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