CA2172448A1 - Optical branch - Google Patents
Optical branchInfo
- Publication number
- CA2172448A1 CA2172448A1 CA 2172448 CA2172448A CA2172448A1 CA 2172448 A1 CA2172448 A1 CA 2172448A1 CA 2172448 CA2172448 CA 2172448 CA 2172448 A CA2172448 A CA 2172448A CA 2172448 A1 CA2172448 A1 CA 2172448A1
- Authority
- CA
- Canada
- Prior art keywords
- waveguide
- taper
- optical
- branch
- optical branch
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
Links
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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/14—Mode converters
-
- 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
- G02B6/125—Bends, branchings or intersections
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Optical Integrated Circuits (AREA)
- Optical Couplings Of Light Guides (AREA)
Abstract
In an optical branch (1) with a substrate (2) and an integrated waveguide structure configured into a Y branch, which is used to couple at least one glass fiber, the waveguide (3) is provided with a constriction that acts as an optical filter before the branching, and causes the forced radiation of undesirable modes. The constriction comprises a first taper (4), which reduces the width of the waveguide (3) to a narrow waveguide section (5) at the inlet to the optical branch (1), and then a mirror-image second taper (6) widens it to the width of the branching waveguides (branches 7).
Description
~, 2172448 .
Field of the Invention The invention concerns an optical branch comprising a s.~ h~te and an integ.~l-ed optical w-~veg~ide structure con.~i.sting of at least one waveguide for coupling glass fibers thereto and at least two branching waveguides. Such branches are used e~peci~lly in optical co~ nications systems.
~3c~ lion of the Prior Art An optical branch is known from publication EP 0 277 390 B1, wherein optical waveguides are integrated on a substrate, namely an input waveguide ext~ncling in a straight line from one end of the s tbsll~e to the opposite end, with two c~c~-lin~
10 branches, each of which contains two limbs. This achieves a distribution of 1:5. In addition, IOC modules with tree structures implemented by ~c~ding Y branches areknown, which have a distribution of 1:8 e.g. (EP 0 283 301 B1, Figure 34).
Since passive optical distributors have increasingly more ~ignific~nce in new optical distribution nelwulh~, optical distributors with partition ratios of l:N or 2:N (e.g.
N = 2, 4, 8, 16, 32...) have been designed for coupling single-mode glass fibers (ELEC-TRONICS Ll~l l~KS, Volume 26, No. 11 of May 24, 1990, pages 707 and 708, and ELECTRONICS Ll~l l~KS, Volume 27, No. 23 of November 7, 1991, pages 2131-2133).
The coupling between glass fibers and optical waveguides at the branch inlet is 20 problematic, particularly because of an unavoidable offset belween the glass fiber core and the optical waveguide. As r~olled in the "IEEE JOURNAL OF LIGHTWAVE
TECHNOLOGY, Volume 10, No. 11 of November 1992, pages 1570-1573" and in "OPTICS L~ KS, Volume 16, No. 5 of March 1, 1991, pages 309-311", the offset itself leads to the undesirable excitation of higher-order modes in w~vegl~ides of the mode field, which have been adapted to the glass fibers.
As quasi-guided modes, these higher-order modes can hltelÇele over relatively long distances of several millimeters for example, with one or even several guided modes in the optical waveguide, and thereby lead to an oscillatory line loss of the guided mode(s) along the length of the optical path. This leads to a greater attenuation and, in the branch areas, to unequal and polarization-dependent distribution of the optical output to the individual branches as well.
Sullln~ of the Invention The invention has the task of reducing the optical losses and the polarization-dependent unequal distribution of light by means of an optical branch comprising a sub-strate and an integrated optical waveguide structure consicting of at least one waveguide for coupling glass fibers thereto and at least two branching waveguides, ch~te.;7P~d in that before the branching point, the waveguide has a constriction. A configuration of the 10 branch includes constriction before each branching point if the wa~eguide structure is in the form of c~cc~-lP~ Y branches.
The constriction can further comprise a first taper and a second taper, the first taper reducing the width of the waveguide to a narrow waveguide section, and the second taper subse~luently widening the narrow waveguide section again.
Furthermore, the entire waveguide structure between each branch stage and the ~eclive widening second taper can be formed by constricted wa~eguide sections.
The optical branch can further be configured so that the first taper is located immediately at an input of the waveguide structure serving to couple a glass ffber thereto.
The optical branch can also be configured so that the second taper is located 20 immediately at an output of the waveguide structure serving to couple a glass fiber there-to.
21724~8 Desc~iplion of the DMwinP
The invention is described in greater detail in the following by means of a draw-ing which scl-e..,At;cally illustrates a configuration example of an optical branch.
Detailed Desc~ lion of the ~ler~lled Embodiment In the drawing, the optical branch as a whole has the number 1. It comprises a s.-bsl~te 2 with an inte~ led optical cGI~lponent, which in the configuration example has the wdveguide structure of a single Y branch.
A waveguide 3 is grown from doped SiO" on the s~bs~l~te 2, which is made of silicon e.g., and is separated from the latter by a buffer layer. The waveguide 3, which 10 is covered by another buffer layer, is 7 ~m thick for example, and its width is adapted to the profile of a single-mode fiber. Waveguide cross sections of 7x7 ~m2 are typical. The refractive index step between waveguide 3 and the buffer layers is 0.004 e.g. Of course, other mAtenAl~ can be used to construct the op~ical branch 1, such as III-V semiconduc-tors, quartz glass, lithium-niobate or lithium-tantalate.
The waveguide structure of the substMte 2 on the inlet side of the optical branch 1 compAses an optical waveguide 3, which is used to couple a glass fiber, a first taper 4 co~ ed thereto, and a n~lower waveguide section 5. A s.~l)s~uent second taper 6 is a mirror-image of the first taper 4, which widens the narrow waveguide section 5 again, e.g. to the width of the original optical waveguide 3. However, in the example illustrated 20 by the drawing, the second taper 6 widens even more to twice the width of one of the two outgoing branches 7, each ~f which is as wide as the optical waveguide 3. If nece~A~y to achieve a defined separation of the branches 7, a gap that inte.lu~ the optical waveguides can be provided bet~een the second taper 6 and the branches 7 (not illustrated).
With CA~Ca~1;ng Y branches, the diverging waveguides of each branch have generally different lengths to the point from where each branch 7 continues with a suit-able bend 8 at a distance and parallel to the neighboring branch 7.
The improvement of the optical branch 1 plo~ellies compAses in pareicular forcing the radiation of undesirable quasi-guided modes in the w~veguide very quickly over a short path, thereby avoiding the effect of the coherent coupling. This is achieved by constricting the waveguide 3 (waveguide section 5), which serves as an optical filter, before it branches off (branches 7). It is imm~teri~l whether the optical wa~eguide struc-ture consists of buried, planar integrated or strip lines. In the present configuration example of the optical con-ponent, the constriction is achieved by nal,owing the width of waveguide 3. However, as an altemative, the constriction can be a waveguide section whose width has been reduced accordingly.
It was ~el~milled that the inlelrelence effect described above can take place inall disturbances of the waveguide; the constriction can thelc~ro~ be provided for each optical col,-ponent which contains at least one waveguide that has been disturbed in some manner, for example by a bend in the line or wherever undesil~ble modes occur; e.g. in a coupling area between a laser that is integl~ed into the substrate and coupled to a waveguide, or between other optical co-nponents. The waveguide 3 on the inlet side can be omitted in this coupling area, as well as in the glass fiber coupling area, and the laser or the glass fiber can be coupled directly to the base of the first taper 4. This ~..eas.lle does not affect the intended effect of very quickly sul~lessing the quasi-guided modes, but it allows the manufacture of optical branches 1 with short lengths.
If the source of the disturbance producing undesirable modes is the bend 8 in a waveguide (branch 7), the constriction is located behind the bend in such a way, that the constriction encompasses the bent waveguide. This allows the length of the constricted linear waveguide to be shorter. With c~cading cG.--pollel-ts in general, the entire waveguide area belweell the branching steps can be configured for a reduced wa~eguide width, so that the entire waveguide path up to the widening taper of the next ~lanching step is constricted and functions as an optical filter. This allows the manufactured length to be shortened even further.
,~".
.
If the second taper 6 forms the outgoing end of the waveguide structure, it can be used to directly couple a glass fiber or another component, or a linear waveguide can be connected to the taper (6), to which the glass fiber or another col..pollent is coupled.
The dimensions of the constriction depend on the design of the optical compo-nent. Designs of 1300 nm and 1550 nm wavelengths are typical. In an optical branch 1 with integrated waveguides that are about 7 ,um wide, the tapers 4, 6 have a taper angle a that is e.g. 0.1 to 1.0 with reference to the central axis of the waveguide 3, a wdveguide section 5 that is between about 6.0 ~m and 6.5~m wide, and is applo~imately lmm to 4 mm long, including the first taper 4.
Field of the Invention The invention concerns an optical branch comprising a s.~ h~te and an integ.~l-ed optical w-~veg~ide structure con.~i.sting of at least one waveguide for coupling glass fibers thereto and at least two branching waveguides. Such branches are used e~peci~lly in optical co~ nications systems.
~3c~ lion of the Prior Art An optical branch is known from publication EP 0 277 390 B1, wherein optical waveguides are integrated on a substrate, namely an input waveguide ext~ncling in a straight line from one end of the s tbsll~e to the opposite end, with two c~c~-lin~
10 branches, each of which contains two limbs. This achieves a distribution of 1:5. In addition, IOC modules with tree structures implemented by ~c~ding Y branches areknown, which have a distribution of 1:8 e.g. (EP 0 283 301 B1, Figure 34).
Since passive optical distributors have increasingly more ~ignific~nce in new optical distribution nelwulh~, optical distributors with partition ratios of l:N or 2:N (e.g.
N = 2, 4, 8, 16, 32...) have been designed for coupling single-mode glass fibers (ELEC-TRONICS Ll~l l~KS, Volume 26, No. 11 of May 24, 1990, pages 707 and 708, and ELECTRONICS Ll~l l~KS, Volume 27, No. 23 of November 7, 1991, pages 2131-2133).
The coupling between glass fibers and optical waveguides at the branch inlet is 20 problematic, particularly because of an unavoidable offset belween the glass fiber core and the optical waveguide. As r~olled in the "IEEE JOURNAL OF LIGHTWAVE
TECHNOLOGY, Volume 10, No. 11 of November 1992, pages 1570-1573" and in "OPTICS L~ KS, Volume 16, No. 5 of March 1, 1991, pages 309-311", the offset itself leads to the undesirable excitation of higher-order modes in w~vegl~ides of the mode field, which have been adapted to the glass fibers.
As quasi-guided modes, these higher-order modes can hltelÇele over relatively long distances of several millimeters for example, with one or even several guided modes in the optical waveguide, and thereby lead to an oscillatory line loss of the guided mode(s) along the length of the optical path. This leads to a greater attenuation and, in the branch areas, to unequal and polarization-dependent distribution of the optical output to the individual branches as well.
Sullln~ of the Invention The invention has the task of reducing the optical losses and the polarization-dependent unequal distribution of light by means of an optical branch comprising a sub-strate and an integrated optical waveguide structure consicting of at least one waveguide for coupling glass fibers thereto and at least two branching waveguides, ch~te.;7P~d in that before the branching point, the waveguide has a constriction. A configuration of the 10 branch includes constriction before each branching point if the wa~eguide structure is in the form of c~cc~-lP~ Y branches.
The constriction can further comprise a first taper and a second taper, the first taper reducing the width of the waveguide to a narrow waveguide section, and the second taper subse~luently widening the narrow waveguide section again.
Furthermore, the entire waveguide structure between each branch stage and the ~eclive widening second taper can be formed by constricted wa~eguide sections.
The optical branch can further be configured so that the first taper is located immediately at an input of the waveguide structure serving to couple a glass ffber thereto.
The optical branch can also be configured so that the second taper is located 20 immediately at an output of the waveguide structure serving to couple a glass fiber there-to.
21724~8 Desc~iplion of the DMwinP
The invention is described in greater detail in the following by means of a draw-ing which scl-e..,At;cally illustrates a configuration example of an optical branch.
Detailed Desc~ lion of the ~ler~lled Embodiment In the drawing, the optical branch as a whole has the number 1. It comprises a s.-bsl~te 2 with an inte~ led optical cGI~lponent, which in the configuration example has the wdveguide structure of a single Y branch.
A waveguide 3 is grown from doped SiO" on the s~bs~l~te 2, which is made of silicon e.g., and is separated from the latter by a buffer layer. The waveguide 3, which 10 is covered by another buffer layer, is 7 ~m thick for example, and its width is adapted to the profile of a single-mode fiber. Waveguide cross sections of 7x7 ~m2 are typical. The refractive index step between waveguide 3 and the buffer layers is 0.004 e.g. Of course, other mAtenAl~ can be used to construct the op~ical branch 1, such as III-V semiconduc-tors, quartz glass, lithium-niobate or lithium-tantalate.
The waveguide structure of the substMte 2 on the inlet side of the optical branch 1 compAses an optical waveguide 3, which is used to couple a glass fiber, a first taper 4 co~ ed thereto, and a n~lower waveguide section 5. A s.~l)s~uent second taper 6 is a mirror-image of the first taper 4, which widens the narrow waveguide section 5 again, e.g. to the width of the original optical waveguide 3. However, in the example illustrated 20 by the drawing, the second taper 6 widens even more to twice the width of one of the two outgoing branches 7, each ~f which is as wide as the optical waveguide 3. If nece~A~y to achieve a defined separation of the branches 7, a gap that inte.lu~ the optical waveguides can be provided bet~een the second taper 6 and the branches 7 (not illustrated).
With CA~Ca~1;ng Y branches, the diverging waveguides of each branch have generally different lengths to the point from where each branch 7 continues with a suit-able bend 8 at a distance and parallel to the neighboring branch 7.
The improvement of the optical branch 1 plo~ellies compAses in pareicular forcing the radiation of undesirable quasi-guided modes in the w~veguide very quickly over a short path, thereby avoiding the effect of the coherent coupling. This is achieved by constricting the waveguide 3 (waveguide section 5), which serves as an optical filter, before it branches off (branches 7). It is imm~teri~l whether the optical wa~eguide struc-ture consists of buried, planar integrated or strip lines. In the present configuration example of the optical con-ponent, the constriction is achieved by nal,owing the width of waveguide 3. However, as an altemative, the constriction can be a waveguide section whose width has been reduced accordingly.
It was ~el~milled that the inlelrelence effect described above can take place inall disturbances of the waveguide; the constriction can thelc~ro~ be provided for each optical col,-ponent which contains at least one waveguide that has been disturbed in some manner, for example by a bend in the line or wherever undesil~ble modes occur; e.g. in a coupling area between a laser that is integl~ed into the substrate and coupled to a waveguide, or between other optical co-nponents. The waveguide 3 on the inlet side can be omitted in this coupling area, as well as in the glass fiber coupling area, and the laser or the glass fiber can be coupled directly to the base of the first taper 4. This ~..eas.lle does not affect the intended effect of very quickly sul~lessing the quasi-guided modes, but it allows the manufacture of optical branches 1 with short lengths.
If the source of the disturbance producing undesirable modes is the bend 8 in a waveguide (branch 7), the constriction is located behind the bend in such a way, that the constriction encompasses the bent waveguide. This allows the length of the constricted linear waveguide to be shorter. With c~cading cG.--pollel-ts in general, the entire waveguide area belweell the branching steps can be configured for a reduced wa~eguide width, so that the entire waveguide path up to the widening taper of the next ~lanching step is constricted and functions as an optical filter. This allows the manufactured length to be shortened even further.
,~".
.
If the second taper 6 forms the outgoing end of the waveguide structure, it can be used to directly couple a glass fiber or another component, or a linear waveguide can be connected to the taper (6), to which the glass fiber or another col..pollent is coupled.
The dimensions of the constriction depend on the design of the optical compo-nent. Designs of 1300 nm and 1550 nm wavelengths are typical. In an optical branch 1 with integrated waveguides that are about 7 ,um wide, the tapers 4, 6 have a taper angle a that is e.g. 0.1 to 1.0 with reference to the central axis of the waveguide 3, a wdveguide section 5 that is between about 6.0 ~m and 6.5~m wide, and is applo~imately lmm to 4 mm long, including the first taper 4.
Claims (9)
1. An optical branch comprising a substrate (2) and an integrated optical waveguide structure consisting of at least one waveguide (3) for coupling glass fibers thereto and at least two branching waveguides (7), characterized in that before the branching point, the waveguide (3) has a constriction.
2. An optical branch as claimed in claim 1, characterized in that the waveguide structure is implemented in the form of cascaded Y branches, and that a constriction is provided before each branching point.
3. An optical branch as claimed in claim 1, characterized in that the constriction comprises a first taper (4) and a second taper (6), the first taper (4) reducing the width of the waveguide (3) to a narrow waveguide section (5), and the second taper (6) subsequently widening the narrow waveguide section (5) again.
4. An optical branch as claimed in claim 3, characterized in that the entire waveguide structure between each branch stage and the respective widening second taper (6) is formed by constricted waveguide sections (5).
5. An optical branch as claimed in claim 3, characterized in that the first taper (4) is located immediately at an input of the waveguide structure serving to couple a glass fiber thereto.
6. An optical branch as claimed in claim 3, characterized in that the second taper (6) is located immediately at an output of the waveguide structure serving to couple a glass fiber thereto.
7. An optical branch as claimed in claim 3, characterized in that the waveguide (3) is approximately 7 µm wide and has a refractive-index step of approxi-mately 0.004, and that the narrow waveguide section (5) has a width between 6.0 µm and 6.5 µm.
8. An optical branch as claimed in claim 3, characterized in that the waveguide (3) is approximately 7 µm wide and has a refractive-index step of approximately 0.004, and that the tapers (4, 6), referred to the central axis of the waveguide (3), have a taper angle .alpha. between approximately 0.1° and 1°.
9. An optical branch as claimed in claim 2, characterized in that the entire waveguide structure between each branch stage and the respective widening second taper (6) is formed by constricted waveguide sections (5).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1995114042 DE19514042A1 (en) | 1995-04-13 | 1995-04-13 | Optical splitter |
| DE19514042.7 | 1995-04-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2172448A1 true CA2172448A1 (en) | 1996-10-14 |
Family
ID=7759659
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2172448 Abandoned CA2172448A1 (en) | 1995-04-13 | 1996-03-22 | Optical branch |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0737872A3 (en) |
| JP (1) | JPH08292340A (en) |
| CA (1) | CA2172448A1 (en) |
| DE (1) | DE19514042A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3448518B2 (en) * | 1999-07-30 | 2003-09-22 | 古河電気工業株式会社 | Array waveguide diffraction grating |
| JP2001235645A (en) * | 2000-02-25 | 2001-08-31 | Furukawa Electric Co Ltd:The | Optical waveguide circuit |
| KR100417002B1 (en) * | 2002-01-14 | 2004-02-05 | 삼성전자주식회사 | Optical power splitter with stabilizing waveguide |
| JP3543137B2 (en) | 2002-04-01 | 2004-07-14 | Ｔｄｋ株式会社 | Optical branch circuit |
| CN106526752B (en) * | 2016-11-23 | 2019-07-26 | 苏州易缆微光电技术有限公司 | Directional coupler and coupling process for multimode lightguide 3dB beam splitting |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3102874B2 (en) * | 1990-11-05 | 2000-10-23 | 日本板硝子株式会社 | Y-branch optical circuit |
| US5078516A (en) * | 1990-11-06 | 1992-01-07 | Bell Communications Research, Inc. | Tapered rib waveguides |
-
1995
- 1995-04-13 DE DE1995114042 patent/DE19514042A1/en not_active Withdrawn
-
1996
- 1996-03-22 CA CA 2172448 patent/CA2172448A1/en not_active Abandoned
- 1996-03-27 EP EP96104840A patent/EP0737872A3/en not_active Withdrawn
- 1996-04-11 JP JP8977096A patent/JPH08292340A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE19514042A1 (en) | 1996-10-17 |
| EP0737872A2 (en) | 1996-10-16 |
| JPH08292340A (en) | 1996-11-05 |
| EP0737872A3 (en) | 1997-03-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |