WO2009145383A1

WO2009145383A1 - Wavelength independent type optical waveguide tap coupler having the asymmetrical structure

Info

Publication number: WO2009145383A1
Application number: PCT/KR2008/003666
Authority: WO
Inventors: Seung-Chan Kwak; Hyung-Myung Moon; Jin-Bong Kim; Hun Han
Original assignee: Ppi Co., Ltd
Priority date: 2008-05-29
Filing date: 2008-06-26
Publication date: 2009-12-03
Also published as: KR20090124154A

Abstract

Provided is an optical waveguide splitting device. More particularly, an optical waveguide tap coupler device having a specific split ratio or monitoring an optical signal by splitting a part of the optical signal using an asymmetrical structure. A taper structure connected to an input port is designed to be asymmetrical to control a length and a width of the taper. A Y-branched optical waveguide tap coupler includes an asymmetrical taper having a structure of appropriately controlling widths of two output port waveguides. Also, an optical waveguide tap coupler having an asymmetrical Y- branched structure includes a structure of maintaining constant power ratios of a main waveguide and a tap waveguide by controlling an angle of one output port waveguide connected to one input port waveguide structure. The optical waveguide tap coupler includes a 1 x 2 asymmetrical waveguide structure having a constant split ratio, a low optical loss and a low polarization dependency over a wide wavelength region when an optical power incident to one input port exits to two output ports.

Description

[DESCRIPTION] [Invention Tit Ie]

WAVELENGTH INDEPENDENT TYPE OPTICAL WAVEGUIDE TAP COUPLER HAVING THE ASYMETRICAL STRUCTURE [Technical Field]

<ι> The present invention relates to an optical waveguide splitter device, and in particular, to an optical waveguide splitter device in the optical communication field etc. More particularly, the optical waveguide splitter device has a constant power ratio, but has a low optical loss and a polarization dependency over a wide wavelength region using a Y-branched 1 x 2 optical waveguide tap coupler device having the asymmetrical taper structure when an optical power incident to an input port exits to output ports. As demands on a broadband multimedia including Internet increase, the advancement of the subscriber network becomes the greatest interest in the communication industries. Fiber To The Home (FTTH) corresponds to the core of the subscriber network technologies.

<2> The FTTH technology includes transmission devices and transmission media to connect between a delivery network and a subscriber. The high-speed access transmission generally refers to a technology providing several Mb/s usage band to the subscriber. Passive Optical Network (PON) manner used in the construction of the FTTH is a network connecting between a central base station which is a provider of service and a subscriber which is a user in the FTTH using only a passive optical device. The PON manner simultaneously transmits data signals including multiplexed voice, data or video service. In this PON system, a waveguide optical splitter device acts as a device effectively splitting the optical power. [Background Art]

<3> In order to implement more convenient, stable and effective system, an optical splitter device is necessary for a network designer. The optical splitter device includes an optical device delivering an optical signal to a subscriber by uniformly splitting an optical power from one input port into N (e.g., 2, 4, 8, 16, 32, and 64) output ports. In order to provide a super^¬ high speed service such as broadcasting and communication using the optical device by installing an optical fiber to each home, the management of an optical fiber is important. For an efficient management of the optical fiber, a branched part of the optical signal needs to be monitored in order to effectively deal with potential problems. A tap coupler refers to a device capable of partially splitting the optical signal, which is classified into a bulky type, an optical fiber style, and a waveguide style according to its configuration. The bulky type includes a combination of a microlens, a prism, an interference filter, etc. The bulky type may provide a device having low wavelength dependency, but requires a long time for an assembly regulation or has a limitation in reliability, cost, or size of device. The optical fiber style is manufactured through abrasion, fusion and elongation processes of the optical fiber itself. The optical fiber style may provide a device having low wavelength dependency. However, the optical fiber style requires a high-level of technology, has low reproducibility, and is unsuitable for the mass-production. The waveguide style may be massively produced on a flat substrate through a photolithographic process using a mask having a shape of the optical splitter. Also, the waveguide style attracts a great attention as a promising technology due to high reproducibility and integration.

[Disclosure]

[Technical Problem]

<4> The present invention provides a wavelength independent type optical waveguide tap coupler having an asymmetrical structure, which can be massively and cheaply produced by forming an optical waveguide pattern on a flat substrate and using a series of a semiconductor process, and provide a structure improving a uniformity of a loss caused by splitting in a wide wavelength range of a communication region, and complementing a polarization loss.

[Technical Solution] <5> The object of the present invention is to design or manufacture a Y- branched 1 x 2 optical waveguide tap coupler structure having an asymmetrical taper structure as a flat optical splitter waveguide device, or to manufacture a waveguide tap coupler capable of monitoring a signal by designing a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical structure. [Advantageous Effects]

<6> According to the present invention, in case of a high tap ratio (10 to 30 %), a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure has a low polarization loss and a uniform optical split ratio over wide wavelength region. Accordingly, it is possible to effectively manufacture an optical splitter device having desired number of channels.

<7> Similarly, in case of a low tap ratio (1 to 10 %), an asymmetrical Y- branched 1 x 2 optical waveguide tap coupler has a low polarization loss and a uniform optical split ratio over wide wavelength region. Accordingly, it is possible to effectively manufacture an optical splitter device having desired number of channels, or an optical tap coupler for monitoring an optical signal with a low power ratio. [Description of Drawings]

<8> FIG. 1 is a diagram illustrating a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention; <9> FIG. 2 is a magnified view of a portion "A" in FIG. l;

<-io> FIG. 3 is a sectional view taken along a line a-a'in FIG. 1;

<π> FIG. 4 is a sectional view taken along a line b-b'in FIG. 1;

<i2> FIG. 5 is a sectional view taken along a line c-c'in FIG. l;

<i3> FIG. 6 is a diagram illustrating a 1 x 2 optical waveguide tap coupler having an asymmetrical Y-branched structure according to an embodiment of the present invention

<I4> FIG. 7 is a magnified view of a portion "B" in FIG. 6: <i5> FIG. 8 is a sectional view taken along a line a-a'in FIG. 6;

<i6> FIG. 9 is a sectional view taken along a line trb'in FIG. 6;

<17> FIG. 10 is a sectional view taken along a line c-c'in FIG. 6;

<I8> FIG. 11 is a graph illustrating a 70:30 split ratio with respect to wavelength in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention;

<I9> FIG. 12 is a graph illustrating a 80:20 split ratio with respect to wavelength in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention;

<20> FIG. 13 is a graph illustrating a 90:10 split ratio with respect to wavelength in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention;

<2i> FIG. 14 is a graph illustrating a 99:1 split ratio with respect to wavelength in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention;

<22> FIG. 15 is a graph illustrating a 70:30 split ratio with respect to wavelength in an 1 x 2 optical waveguide tap coupler having an asymmetrical Y-branched structure according to an embodiment of the present invention;

<23> FIG. 16 is a graph illustrating a 80:20 split ratio with respect to wavelength in an 1 x 2 optical waveguide tap coupler having an asymmetrical Y-branched structure according to an embodiment of the present invention;

<24> FIG. 17 is a graph illustrating a 90:10 split ratio with respect to wavelength in an 1 x 2 optical waveguide tap coupler having an asymnietr ical Y-branched structure according to an embodiment of the present invention; and

<25> FIG. 18 is a graph illustrating a 99:1 split ratio with respect to wavelength in a 1 x 2 optical waveguide tap coupler having an asymmetrical Y- branched structure according to an embodiment of the present invention. [Mode for Invention]

<26> Hereinafter, an optical waveguide tap coupler having an asymmetr ical structure according to the present invention will be described in detail with reference to the appended drawings.

<27> FIG. 1 is a diagram illustrating a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention. FIG. 2 is a magnified view of a portion "A" in FIG. 1. FIG. 3 is a sectional view taken along a line a-a' in FIG. 1. FIG. 4 is a sectional view taken along a line b^~b' in FIG. 1. FIG. 5 is a sectional view taken along a line c-c' in FIG. 1. FIG. 6 is a diagram illustrating a 1 x 2 optical waveguide tap coupler having an asymmetrical Y- branched structure according to an embodiment of the present invention. FIG. 7 is a magnified view of a portion "B" in FIG. 6. FIG. 8 is a sectional view- taken along a line a~a' in FIG. 6. FIG. 9 is a sectional view taken along a line b-b' in FIG. 6. FIG. 10 is a sectional view taken along a line c-c' in FIG. 6. FIGS. 11 and 12 are graphs illustrating losses in accordance with split ratios in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention. FIGS. 13 and 14 are graphs illustrating losses in accordance with split ratios with respect to wavelength in a Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure according to an embodiment of the present invention.

<28> Referring to FIGS. 1 and 2, the Y-branched 1 x 2 optical waveguide tap coupler according to a preferred embodiment of the present invention includes the asymmetrical taper structure between one input port and two output ports. In order to control the split ratio of the output port, a length of the asymmetrical taper and a width of a waveguide toward the output port from the asymmetrical taper may be appropriately regulated to control the split ratio of the output port. Specially, a loss ratio by split of the output port is designed to be uniform over a wide wavelength region to reduce a wavelength dependency and a polarization loss. <29> That is, the input port includes an input waveguide 11. Also, the output port includes a first output waveguide 15, and a second output waveguide 16. The asymmetrical taper 12, and first and second branched output connection waveguides 13 and 14 are included between the input port and the output port .

<30> The asymmetrical taper 12, as described in FIG. 2, is connected to the input waveguide 11, and has an asymmetrical structure of a specific angle Zi.

In this case, based on the split power ratio, an input width Wi of the asymmetrical taper may be 5 /mi, and an output width W₂ of the asymmetrical taper may be 14 /an, and an angle Zi of the asymmetrical taper may be 0.5 degree, and an output side width W₅ of the asymmetrical taper may be 0.4 /mi, and a length Li of the asymmetrical taper may be 300 to 1000 /zni. Also, a width of a width expansion part W_G where two waveguides are split toward the output port may be 0.8 to 1.2 /mi.

<3i> The Y-branched 1 x 2 optical waveguide tap coupler having the asymmetrical taper structure, as described in FIGS. 3 to 4, includes a silica substrate 50, a silica glass thin film 55 and core waveguides 25, 35, 40 and 45. As described in FIG. 3, a sectional view (a line a^~a' of FIG. 1) of the input waveguide 11 includes a single mode optical waveguide. FIG. 4 is a sectional view (a line b~b' of FIG. 1) of a first branched output connection waveguide 13 and a second branched output connection waveguide 14 extending from the Y-branched structure of the asymmetrical taper 12. The sectional sizes of the cores waveguides are asymmetrically different from each other. In FIG. 5, the output waveguides at an interval of 127 /mi or 250 /mi are shown to be the same size of single-mode waveguide 40 and 45 in order to combine with a single-mode optical fiber.

<32> The Y-branched optical waveguide tap coupler having the 1 x 2 asymmetrical taper structure according to the present invention is designed to have the split ratios of 70:30, 80:20, 90:10, 95:5, 98:2, and 99:1 in a wide wavelength region (1.25 /im to 1.65 _/im) . An exemplary embodiment of the present invention will be described as follows.

<33> The input waveguide is split into a first output waveguide 15 and a second output waveguide 16 at an interval of 127 /mi or 250 μni.

<34> FIGS. 11 and 12 are graphs illustrating an optical loss with respect to a wavelength in the Y-branched optical waveguide tap coupler having the 1 x 2 asymmetrical taper structure, which verify that the optical power of the output port is uniform over the wide wavelength region for each split ratio.

<35> As described in FIGS. 6 and 7, a Y-branched 1 x 2 optical waveguide tap coupler having another asymmetrical structure according to another embodiment of the present invention includes an asymmetrical Y-branched structure between one input port and two output ports. In order to control the split ratio of the output port, the waveguide is split into narrow waveguides. A split loss ratio of the output port is designed to be uniform in a wide wavelength region by regulating an angle between the narrow waveguides in order to reduce a wavelength dependency and a polarization loss.

<36> That is, the input port includes an input waveguide 31, and the output port includes a first output waveguide 33, and a second output waveguide 34. A tap output waveguide having a narrow and asymmetrical Y-branched structure is included between the input port and the output port.

<37> In the asymmetrical Y-branched structure, as described in FIG. 2, the tap output waveguide 32 is split from the input waveguide 31. In consideration of a polarization loss, the width W₈ of the tap output waveguide

32 is smaller than those of the single-mode waveguide. Also, the tap output waveguide 32 has a specific angle Z₂ according to a split ratio. In this case, a width W₈ of the asymmetrical Y-branched tap waveguide is 4 /ΛII in consideration of the power ratio split. A width W₉ of the waveguide connecting between the tap waveguide and the single-mode waveguide may be 2 im, and an angle Z₂ of the tap waveguide may be 1 to 8 degrees, and a length of the tap waveguide 32 may be 100 to 500 μm. Also, a width of a width expansion part WG where two waveguides are split toward the output port may be 0.8 to 1.2 μm.

<38> The asymmetrical Y-branched 1 x 2 optical waveguide tap coupler, as described in FIGS. 8 to 10, includes a silica substrate 50. a silica glass thin film 55, and core waveguides 60. 65, 75, and 80. As described in FIG. 8, a sectional view (a line a^~a' of FIG. 6) of the input waveguide 31 includes a single mode optical waveguide. FIG. 9 is a sectional view (a line b-b' of FIG. 3) of the tap output waveguide 32 extending from the asymmetrical Y-branched structure. The sectional sizes of the cores waveguides are asymmetrically different from each other because the width of the tap waveguide is small. In FlG. 10, the output waveguides at an interval of 127μm or 250/mι are shown to be the same size of single-mode waveguide 33 and 34 in order to combine with a single-mode optical fiber.

<39> The 1 x 2 optical waveguide tap coupler of the asymmetrical Y-branched structure according to another embodiment of the present invention is designed to have the split ratios of 70:30, 80:20, 90:10. 95:5, 98:2, and 99-'l in a wide wavelength region (1.25 μm to 1.65 ;cm) . An exemplary embodiment of the present invention will be described as follows.

<40> The input waveguide is split into a first output waveguide 33 and a second output waveguide 34 at an interval of 127 μm or 250 //m.

<4i> FIGS. 13 and 14 are graphs illustrating an optical loss with respect to a wavelength in the 1 x 2 optical waveguide tap coupler having the asymmetrical Y-branched structure, which verify that the optical power of the output port is uniform over the wide wavelength region for each split ratio. The optical waveguide includes an optical circuit of core waveguide size of 6 μm x 6 _/mi having a refractive index difference of approximately 0.4 Δ% to approximately 0.45 Δ% between the substrate and the optical waveguide by adding GeO₂ increasing the refractive index to SiOj series on the silica substrate. <42> As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.

<43> In the case where the output value of one port is 30 to 10 %, the present invention mainly relates to production of a device having low- polarization loss and a uniform power ratio between two output ports in a wavelength of the communication region by relatively controlling a width of the waveguide using a Y^~branched 1 x 2 optical waveguide tap coupler having an asymmetrical taper structure between one input port and two output ports.

<44> In the asymmetrical taper-typed Y-branched optical waveguide tap coupler, the width W_G between the asymmetrical output ports may be 0.5 to l.δ

//ni.

<45> Also, the length of the asymmetrical taper connected to the input port may be 300 to 1000 /an, and the width of the asymmetrical taper at the input port side may be 5 to 8 /an, and the width of the asymmetrical taper at the output port side may be 10 to 20 _/an.

<46> The angle of the asymmetrical taper connected to the input port may be 0.3 to 0.8 degrees.

<47> In the case where the output value of one port is 10 to 1%, the present invention mainly relates to production of a device having low polarization loss and a uniform power ratio between two output ports in a wavelength of the communication region by controlling a width and an angle of the waveguide using a 1 x 2 optical waveguide tap coupler having an asymmetrical Y-branched structure between one input port and two output ports.

<48> In the asymmetrical Y-branched optical waveguide tap coupler, the width W₀ between the asymmetrical output ports may be 0.5 to 1.5 /an. <49> Also, the width of the tap waveguide split from the input port may be 2 to 6 μm, and the angle of the tap waveguide may be 1 to 10 degrees, and the length of the tap waveguide may be 50 to 700 μm.

<50>

Claims

[CLAIMS] [Claim 1]

A Y-branched 1 x 2 optical waveguide tap coupler having an asymmetr ical taper structure combining or splitting an optical signal, characterized in that the optical waveguide tap coupler is controlled to have a constant power ratio with respect to the optical signal by controlling widths of an upper output port waveguide and a lower output port waveguide and a length of an asymmetrical taper.

[Claim 2]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 1, wherein a width (Wf₁) of a width expansion part of the optical waveguide tap coupler is

0.5 to l.δ μm.

[Claim 3]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 1, wherein a length (Li) of the asymmetrical taper is 300 to 2000 ιm.

[Claim 4]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 1, wherein an input width (Wi) of the asymmetrical taper is 5 to 8 /aii.

[Claim 5]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 1. wherein an output width (W₂) of the asymmetrical taper is 10 to 20 ;m.

[Claim 6]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 1, wherein an angle (Zi) of the asymmetrical taper is 0.3 to 0.8 degrees.

[Claim 7]

A Y-branched 1 x 2 optical waveguide tap coupler having an asymmetrical structure combining or splitting an optical signal, characterized in that the optical waveguide tap coupler is controlled to have a constant power ratio with respect to the optical signal by controlling a width and an angle of a lower output port waveguide.

[Claim 8]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 7, wherein a width (W_G) of a width expansion part of the optical waveguide tap coupler is

0.5 to 1.5 μm.

[Claim 9]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 7, wherein a width (W₈) of the lower output port waveguide is 2 to 6 ιιm.

[Claim 10]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 7, wherein a length (L>) of the lower output port waveguide is 50 to 700 μm.

[Claim 11]

The Y-branched 1 x 2 optical waveguide tap coupler of claim 7, wherein an angle (z₂) between the lower output port waveguide and an upper output port waveguide is 1 to 10 degrees.