WO1997032228A1

WO1997032228A1 - INTEGRATED OPTICAL 1xN SPLITTER

Info

Publication number: WO1997032228A1
Application number: PCT/EP1997/001019
Authority: WO
Inventors: Thomas Paatzsch; Ingo Smaglinski
Original assignee: INSTITUT FüR MIKROTECHNIK MAINZ GMBH
Priority date: 1996-02-29
Filing date: 1997-02-28
Publication date: 1997-09-04
Also published as: DE19708812A1

Abstract

The invention relates to an integrated optical 1xN splitter with an input waveguide (1) and N output waveguides, at least the outermost output waveguides (2a,b) slanting in relation to each other. The 1xN splitter also has a divider (3) containing a region (5) which is upstream of the intersection point (4) of the inner edges (9, 10) of the outermost output waveguides (2a,b) and has the same refractive index as the waveguide cladding (16). The 1xN splitter is characterised by a low attenuation while providing a wide branching angle. The width of the divider (3) may, for example, increase or decrease. There may also be a closed region (3, 5), the two output waveguides (2a, b) being connected to each other via a cross-member (15) made of nuclear material.

Description

Integrated optical 1 xN branch

The connection relates to an integrated optical IxN branching device according to the concept of claim 1. Such branching devices can be used, for example, in optical night technology or in sensor technology

The transmission of signals and data in telecommunications and sensor technology is increasingly based on optics. Instead of electrical connections, optical connections are created with the help of optical fibers, which together form an optical network. The so-called passive optical networks are of particular importance to which the data signals are distributed over a large number of channels at the same time In order to set up such networks, large numbers of optical lxN splitters are required at the lowest possible cost

Integnert-optical lxN branches are currently mainly produced using glass, silicon or polymer technology. Compared to other materials, polymeies have the great advantage that they can be processed inexpensively by molding processes such as injection molding or hot stamping In the polymer technology, in addition to the wave-guiding areas, fiber-optic structures are also integrated into the component, into which the fibers only have to be introduced without the need for adjustment. This results in an easy simplification of the manufacturing process

Integπeit-optical waveguide usually have a waveguide core and a waveguide cladding. The core refractive index is larger than the cladding bending index. The transpoit of the optical signal takes place essentially in the absence of the waveguide, particularly in the area of remote transmission. of

BESWIGUNGSK0P1E A so-called single-mode waveguide is required for data and sensors. Such waveguides suitable for single-mode transmission have core dimensions in the range of 3-10 μm at the common wavelengths (0.4-1.6 μm).

The optical properties of wave-guiding structures can be calculated, for example, by means of ^“ beam propagation simulation” (BPM simulations). An optical input field is specified and the further field along the wave-guiding structure is calculated step by step using numerical methods. These calculations are based on this Make sure that the discretization of the refractive index field and the 'propagation' step size are not too large. Various commercial programs are currently available for the BPM, some of which are based on different numerical methods. check the values obtained with the various numerical methods for agreement.

An overview of integrated optical branches is given, for example, in W. Karthe: 'Integrated optics': Akademische Verlagsgesellschaft Leipzig 1991, pp. 180-185. It describes a 'standard splitter' with one input waveguide and two output waveguides. A splitting device is provided between the output waveguides, which converts the input waveguide into the two output waveguides and has a refractive index that differs from the core and cladding material of the waveguides. In one embodiment, the two output waveguides are inclined with respect to the input waveguide and the splitting device is designed as a tapering region between the inner edges of the output waveguides.

In another embodiment of the Y-branch, the tip of the splitting device is replaced by a rounding. The disadvantage of this is that a low insertion loss of the branch can only be achieved if The radius of the rounding should be selected to be small (e.g. 0 1 μm). Due to the resulting high aspect ratio (waveguide height e.g. 8 μm), such a configuration is also associated with considerable technical problems. This applies in particular to the manufacture of a lxN vei to own in Abtoimtethnik. since if the aspect ratio is too large, a separation of 1 oi mwei tool and foam part (so-called demolding) is not non-destructive duich / utuhien

As a further disadvantage of the design, it follows that for a good function of the branch, the output waveguides may only be inclined by a small angle (for example <1 °) with respect to the input waveguide In the case of the oak of the branch This is based on the fact that the initial branches of the branch branch have to be separated so far apart that the fibers can be coupled (ie at least two fibers fit next to each other)

A triangular region is provided between the input waveguide and the two output waveguides, which has a refractive index which is lower than that of the input waveguide and the output waveguide

Published by M Seino, M. Shina. T Mekada, N Nakajima ^' Lou loss Mach-Zehndei modulatoi using mode coupling Y-branch waveguide ", Pioc 13ιh Euiop Conf Opt Commun. ECOC, Helsinki 1987. S 113-1 16 describes an innovative I-optic Y-Vei Zweig, in which the partition in the video part is formed as an essentially rectangular area. This is slightly beyond the intersection of the inner edges of the output waveguide and has a different refractive index than the waveguide and cladding drive the arithmetic mean of core and jacket plating A disadvantage of this Y-branch is that the front part of the splitting device has an area with a different refractive index value than in the waveguide core and jacket. This means that compatibility with common manufacturing processes (which only provide two refractive index values) is no longer guaranteed. To produce the branching device, a suitable, new manufacturing process must therefore be developed at great expense.

In Z. Weissman. E. Maroni, A. Hardy: 'Very low loss Y-junction power divider ^' : Optics Lett. Vol 14 No. 5, p. 293 (1989) describes a Y-splitter in which the splitting device has a substantially rectangular area which extends exactly to the intersection of the inner edges of the output waveguide and has a refractive index which corresponds to that of the waveguide cladding. Furthermore, the input and output waveguides have a different width.

The BPM calculations carried out in this publication show that a good function of the splitter with an attenuation of less than 1 dB is only guaranteed. when the first (antisymmetric) mode is present on the input waveguide. However, this is usually not the case because e.g. after the light emerges from the coupling fiber, essentially the zero (symmetrical) mode is excited. This Y-splitter therefore has the decisive disadvantage that special elements for selective excitation of the first mode must be provided in front of the splitter. However, the overall damping of the component is considerably increased by such elements, since on the one hand the mode conversion cannot take place without loss and, in addition, the overall length of the wave-guiding regions increases. The latter is disadvantageous in particular for polymeric waveguides because, because of their high material absorption, they are dependent on short waveguide lengths.

The lowest possible loss of attenuation of the lxN splitters is particularly important for use in telecommunications. B. larger transmission distances are possible. km ueiteiei disadvantage then ordered that the width of the waveguide core parallel to the front part of the device is only 1-2 μm (waveguide height 3 μm). The aspect ratio (high width) of approx. 2 1 with simultaneous structure widths of approx. 1 μm results to a considerable degree of possible spacing in the waveguide production due to diffraction effects, this is particularly the case when a shaping tool for waveguide molding is to be produced by means of UV lithography

In Z Weissman. k Mai om, A Hardy 'Novel passive mulübranch power splittcis toi integiated optics. Appl Optics, Vol 29 No 30, S 4426 (1990) describes a 1 x 4 branch which has an essentially rectangular distribution device in the front part. The leading edge of the distribution device lies exactly at the intersection of the inner edges of the output waveguide comes that the input waveguide is about four times wider than the output waveguide. A disadvantage of this configuration is that a taper has to be integrated into the branching device, which widens the input field from the initial diameter by a factor of 4. However, this taper increases the overall length of the component considerably ei hohi. which is particularly disadvantageous for polymeric waveguides

The 1P 63-60405 describes a Y-branch with an incision in the branching area. dei has a refractive index which lies in the range between that of the waveguide material and the substrate material. This kinsehmtt ei extends into the vicinity of the input waveguide

Starting from Z Weissman et al, Optics Lett Vol 14 No 5. S 293 (1 ° 89), Ls is the author of the mouth. to create an lxN branching device which has the smallest possible insertion vaporization and can graze hot on a simple basis You. Output with an optical-optical IxN branch according to claim

1 solved

BPM calculations have led to the surprising result that by the fact that the authentication direction comprises an area which lies in front of the intersection of the inner edges of the outermost output waveguide, the configuration of the distribution device according to the invention can result in a very low lintuge vaporization for a Y- The branching device is, for example, small 0 1 dB when optimizing the structural dimensions of a single wavelength (z λ = 1 3 μm) and less than 0 2 dB when optimizing on two wavelengths (7 B 1 3/1 55 μm) has the same refractive index as the waveguide cladding, contributes in an optimal manner / ui rianstoi mation of the optical field from the input waveguide into the output waveguide. which results in a small insertion vaporization with simultaneously large branching angles

In a preferred embodiment of the invention, the splitter has a paidllel axis of symmetry to the input waveguide. This makes it evenly distributed for each output waveguide that is symmetrical to one another. However, it may also be desirable that the \ eι to eιgeι does not have a rivet axis and the optical field points to it individual output arms with different proportions

Furthermore, the design of the distribution device allows a comparatively large branching angle of 2 ° to 5 ° for a Y-branch. This has the great advantage that the length of the low-frequency areas can be considerably reduced High internal material absorption of partial reverbs Fei nei can therefore a small insertion steaming with a large branching angle at the same time The design of the lxN splitter according to the invention provides that the transmission wave guide and the output wave guide have the same width, so that no tape converter or mode converter is required in front of the branch point, which means that the length of the branch can be considerably reduced

It is vveitei hiπ von Voπeil if the distance of the area from the intersection of the input waveguide edge and the assigned edge of the outermost output waveguide is smaller than its longitudinal extension from the intersection of the inner edges of the outermost output waveguide

In a further preferred embodiment, the area extends into the input waveguide

The distribution device can either contain different ones covered with oak or a coherent area. The latter is particularly advantageous for the production of waveguides in impression technique, because the stability of the mold insert is increased and trouble-free removal is possible

In a shared configuration, the distribution device in the front area has a substantially constant width. This avoids small aspects, which is particularly the separation of component and foam insert (so-called de-gum removal) from Voiteil. However, it may be desirable that Bee in the distribution device in front of Beieich increases continuously and that the width of the waveguide core running in parallel increases

The distribution device preferably has a substantially constant width at least in the region of the intersection point. There is also the possibility that the distribution device and this essentially affects the area between the intersection point narrows or blows in the direction of the input shaft guide The output waveguide can be connected to the intersection of the inside edges of the extreme output waveguide via a web made of waveguide core material

In a part of the arrangement of the participation, the input branch line is broadened essentially in a step-wise manner. This has the great advantage that the waveguide core lying parallel to the front area of the direction of the direction of spreading also spreads, and a smaller aspect, too, to a large extent. whereby an emiacheie and piaziseie Hei position of the IxN-branching is possible Autgrund dei in the structure with 7 uι UV radiation large structural dimensions, it is in particular possible to use a plastic tool for waveguide in impression technique also by means of UV lithographic plates, using the larger ones Bee of the wave guide does not insert the core material into the molded part! I disgust

Instead of a mare-sized distribution, the input waveguide can also be continuously widened to a length 1 as long as the optical field in the processing unit is not significantly enlarged in width.This is achieved with a small 1 "(e.g. equal to ten times the waveguide width of the input waveguide) As a result of the continuous widening, see the part that no corner areas as with the step-like vein broadening my renting results in a considerably simpler manufacture of the wave guide using abtoim technology. Furthermore, the lack of corner areas simplifies the filling of the key file into the molded part

\ oi the supply of the input waveguide is preferably before the distribution

The Vei lialtnis dei kingdiigswellenleiterbeiten voi and after dei Vei widening is partly partly giossei as 1 5 The distribution device can also be designed in such a way that the input waveguide and output waveguide are separated from one another and the key file is completely divided by the area before the intersection. The distribution device preferably has the same blue as the waveguide core

The interruption of the wave-guiding area has the advantage that the division device is additionally stabilized by the lateral areas. This achieves a high level of division device compared to the input waveguide and output waveguide and thus a high distribution uniformity of the branching device

The position of the shaft guide in Ablorm technique is advantageous. that the molding tool is manufactured by means of X-ray lithography and subsequent galvanomotivation. In contrast to UV lithography, diffraction etchings are considerably reduced when using X-ray beams, so that the design optimized by means of BPM calculations can be transferred to the molding tool with great precision. to manufacture the waveguide core, which is parallel to the front part of the distribution device, in high quality

Exemplary embodiments of the invention will be given below with reference to the drawings

Show it

1 Y-Vei zueigei according to a first embodiment,

Fig. 2 Y-delay with widened input waveguide,

Hg vei various execution norms with regard to the length of the front part of the distribution device, Tig 4 various geometrical configurations of the front end of the device and the device

1 i-i 5 a Y Vei branches with an interruption of the waveguide kei nmateπals

Fig. 1 shows a 2-dimensional cross-section of a symmetrical (Sv mmeti iaxisse 8) Y-branching ice with an input waveguide 1 and two output waveguides 2a, b. The input and output waveguides have a quadratic cross section with an edge length of dl = 8 μm (the waveguide is high is not shown in Fig. 1) The refractive indices are nM = 1 45 in the waveguide jacket 16 and nK = 1 454 in the waveguide core. The specified waveguide parameters are adapted to a standard glass fiber (SM 1300) and therefore a loss-free coupling is possible the standard length 1 3/1 55 μm is monomodal

The output waveguide 2a, b are each inclined at an angle γ = 2 5 ° with respect to the input waveguide 1. Between the output waveguides 2a, b are the distribution voi 3, which is ordered from the sheath material of the waveguide and has a refractive index nM = 1 45. Ulteilungsvoi nchiung has a region 5 of the intersection 4 of the inner edges 9 10 of the output waveguide 2a. b lies in the Vie bieiteiungsbeieich or Taperbeieich 1 1 of the Y-branch, which in the Dai position shown in the Dai position at the intersection 6 of the input waveguide edge 14 and zugeoidnetei edge 12 13 of the extreme output waveguide 2a begins. The λulteilungsvoi nchtungsung 3 is advantageous as a coherent 3 Area with a constant width of 5 meters

In the hot position of the waveguide, it is advantageous to round off all corners with a radius of 1 2 μin (not shown in FIG. 1) 1-ig 2 shows a Y-branch according to the invention with a widening 11 of the longitudinal waveguide 1, waveguide width d1, refractive indices nM / nK and winding angle are equal to the values in FIG. 1. The widening 1 1 of the input waveguide is advantageously carried out over a length of 1 ₍ , = 20 μm to a final value of d2 = 16 μm. The ratio of the waveguide width after and before the widening has the value 2. The waveguide core running parallel to the front part of the splitting device 3 7 has a width of

4 75 μm

Dei 5 of the splitting device 3 advantageously has a width of approximately b = 6.5 μm and a length of approximately Z = 95 μm.

3a. b and c different configurations of the distribution device 3 are shown. The front area is in FIG. 3a

5 of the splitting device 3 in the vicinity of the intersection 4 of the inner edges 9. 10 of the outermost output waveguides 2a, b. The distance of the front area 5 from the intersection 6 of the input waveguide edge 14 and the associated edge 12 of the outermost output waveguide 2a is greater than its distance from the intersection 4

In FIG. 3b the distance of the front area 5 from the intersection 6 is smaller than its distance from the intersection 4 of the inner edges 9, 10 of the outermost output waveguides 2a, b. In FIG. 3c the area 5 extends into the input waveguide "1 and lies in front of the intersection 6 of the Lingangs waveguide edge 14 and associated edge 12 of the outermost output waveguide 2a. The width of the splitting device 3 is smaller than the width of the input waveguide 1.

FIG. 4 shows a Y-branching device with a widened input waveguide 1 analogous to FIG. 2, with different execution forms of the division device 3 being shown. The width of the division device 3 can, for example, also decrease (FIG. 4a. B). A closed area 3.5 (FIG. 4c) can also be used. voi liet-eii wherein the two output shaft guide 2a, b are connected to each other by a web 15 from Ku nmaieπal

le turned to vei! The individual geometrical dimensions are to be optimized using simulation simulations. This should ensure that the branching manipulation is as smooth as possible and the dependence of the distribution uniformity on fluctuations in the geographic dimensions (1 tolerance tolerances) is as low as possible

FIG. 5 shows a Y branch according to the invention with a widened part of the dividing line 3. In the embodiment shown, the width of the parting line 3 corresponds to the width dl of the input waveguide 1

The result of the division of device 3 by the value given above means that the waveguiding area at the branching point will be separated. Duich simulation calculations based on the above-mentioned width for bending numbers, waveguide width and distribution angle result that the Uiuei biungung 17 des wave-guiding area advantageously follows over a length of 11 - 40-45 μm ei. This ensures that the branching device has a very small frequency manipulation of less than 0 1 dB. If you select a value in 11 outside the specified range, the loss loss increases

Claims

Inicgi ici-opticali l xN splitters with an input waveguide (1) and N output waveguide, where at least the outermost output waveguide (2a, b) are inclined towards one another, and with a distribution device (3) that have the same refractive index as the dei Has wave guide jacket (16),

daduich marked,

that the partition (3) comprises an area (5) which lies in front of the intersection (4) of the inner edges (9, 10) of the outermost output waveguide (2a, b)

l xN branching egg according to one of the preceding claims, characterized in that the IxN branching member has an axis of symmetry (8) lying parallel to the input waveguide "(1)

1

Refuser according to one of the preceding claims, characterized in that N = 2 and the angle of inclination between the output waveguide (2a, b) and the output waveguide (1) is 2 ° to 5 °

KN vein branch according to one of Claims 1 to 3, characterized in that the output waveguide (1) and the output waveguide (2a, b) have the same bee

1 \ N- Vei Zweiget according to one of the preceding claims, characterized in that the distance of the area (5) from the intersection (6) from the input waveguide edge (14) and zugeoidnetei edge (12.13) of the outermost output waveguide (2a. B) is smaller than his

1 angsei su corner from the intersection (4) o 1 \ N-Veι zueιgeι according to one of the preceding claims, characterized in that the region (5) extends into the input waveguide (1)

7 1 \ N- Branched "according to one of the preceding claims, characterized in that the distribution device (3) is a coherent area

8 1 \ N-Verzweιgeι according to any one of the preceding claims, characterized in that the distribution device (3) has a substantially constant width at least in the region of the intersection (4)

9 1 \ N-Veιzweιgeι according to any one of claims 1 to 7, characterized in that the distribution device (3) narrows in the direction of the input waveguide (1).

1U KN-Veivweiger according to one of claims 1 to 7, characterized in that the distribution device (3) widens in the direction of the receiving waveguide (1).

1 1 1 \ N-Veιzweιger according to one of claims 1 to 10, characterized in that the output waveguide (2a, b) behind the intersection (4) ubei emen web (15) made of waveguide core material are connected ver

12 l λN-splitter according to one of the preceding claims, characterized in that the input waveguide (1) widens in steps 1 \ N-Veι Zweιgeι after a dei Spiuche 1 to 1 1 characterized in that the Emi waveguide (1) bleed for a length 1 "continuously vei and that 1, less than ten times the width of the

1 output shaft guide (1)

I xN-Vei Zweigigei according to one of claims 12 or 13, characterized in that the widening of the input shaft guide (1) lies in front of the partitioning device (3)

I λN branch according to one of the preceding claims, characterized in that the ratio of the input waveguide widths to and from the widening is greater than 1 5

1 \ N-Veιzweιgeι according to one of claims 1 to 4 or 7, characterized in that the division device (3) separates the input waveguide (1) and the output waveguide (2a, b) from one another

Drawing reference list

Input shaft guide a. b Output shaft guide

Aufleilungsvoi direction

Intersection

Area

Intersection

Axis of symmetry inner edge 0 inner edge 2 assigned edge 3 assigned edge 4 optical wave conductor edge 5 web 6 waveguide jacket 7 interruption