CN1320400C - Digital optical switch in low cross talk - Google Patents

Abstract

The invention discloses a low crosstalk digital optical switch. It is composed of a Y-branched waveguide digital optical switch and S-curved waveguide variable optical attenuators respectively connected to both ends of the Y-branched waveguide digital optical switch. Using the negative refractive index effect of the material, the switching characteristics of the switching light are greatly improved without increasing the length of the device and the complex structure. In addition, the angle of the Y bifurcation can be expanded, and the structure of the Y bifurcation area can be modified at the same time, which reduces the difficulty of the process. According to the BPM method (beam transmission method) simulation analysis, the digital optical switch of the present invention has the advantages of low crosstalk, small insertion loss, small polarization correlation, good wave spectrum flatness, easy integration and the like.

Description

Low Crosstalk Digital Optical Switches

technical field

The invention relates to an optical component, in particular to a digital optical switch with low crosstalk.

Background technique

With the rapid development of optical fiber communication technology and dense wavelength division multiplexing (DWDM) system, digital optical switch (DOS), as an important optical waveguide device, has been used more and more widely. Common optical switches include Mach-Zehnder interferometer type, directional coupler type, X junction type, Y bifurcated type, etc. Among them, Y bifurcated digital optical switches are more concerned by people, but usually Y bifurcated The fork angle is designed to be very small, generally controlled between 0.05° and 0.15°, which increases the difficulty of the waveguide manufacturing process. Therefore, people continue to design switching devices with some excellent performance parameters starting from the structure of the switch, such as integrating with a variable optical attenuator (VOA) as an effective method, which can greatly improve the extinction ratio of the switch.

The end of the output waveguide of the common Y-branch type 1×2DOS generally has an S-curved transitional waveguide, which leads the output light out and facilitates coupling with the standard optical fiber array. According to the curved waveguide theory, the refractive index on the tangent surface of the waveguide bending area is not a step type, but can be equivalent to an outwardly inclined distribution. When the distance increases to the outside, the refractive index of the cladding increases continuously, even higher than that of the core. The larger the area, the electromagnetic field distribution will also translate to the direction of the increase of the refractive index, so radiation loss will occur. In addition, the conventional Y-branch digital optical switch uses the principle of mode coupling separation to realize the switching function, so the bifurcation angle α needs to be very small, generally between 0.05° and 0.15°, so the bifurcated waveguide fabrication The process is difficult.

Contents of the invention

According to the characteristics that the curved waveguide is easy to produce radiation loss and can be made into a curved optical variable attenuator by using the negative refractive index effect of the material, the purpose of the present invention is to provide a digital optical switch with low crosstalk. Directly use the S-shaped bend transition waveguide of the Y-branch DOS switch output waveguide, and design its curved waveguide into an S-shaped bend waveguide variable optical attenuator (VOA), forming an integration with the Y-branch 1×2DOS.

In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a Y-branched waveguide digital optical switch and an S-curved waveguide made of organic polymer material respectively connected to the two ends of a Y-branched waveguide digital optical switch The variable optical attenuator is integrated, and the electrodes of the S-bend waveguide type variable optical attenuator are respectively located on the side of the S-shaped bend with a smaller curvature radius.

The S-curved waveguide type variable optical attenuator is sequentially connected by a connecting waveguide through a tapered transition waveguide, an S-curved waveguide, another tapered transition waveguide and another connecting waveguide. The edge distance of the waveguide is ±1 micron, and the electrodes of the S-curved waveguide variable optical attenuator on both sides are respectively connected in series with the electrodes of the Y-branched waveguide digital optical switch.

The bifurcation angle α of the Y bifurcated waveguide digital optical switch is 0.3-1.0°, and the filling part of the bifurcation angle is filled at the bifurcation, and the top width d thereof is 1.5-2 μm.

The beneficial effect that the present invention has compared with background technology is:

The invention greatly improves the crosstalk characteristic of the switching light without increasing the device length and complex structure. And the angle of the Y bifurcation can be expanded, and at the same time, the structural modification of the bifurcation area is adopted to reduce the difficulty of the process. According to the BPM method (beam transmission method) simulation analysis, this new type of digital optical switch has the advantages of low crosstalk, small insertion loss, small polarization dependence, good spectral flatness, and easy integration.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Figure 1 is an effect diagram of the switching light simulated by the BPM method;

Fig. 2 is a schematic structural diagram of a digital optical switch of the present invention;

Fig. 3 is a schematic diagram of the structure of the digital switch light Y bifurcation part of the present invention;

Fig. 4 is a partial structural diagram of an S-curved waveguide variable optical attenuator in the digital switching light of the present invention;

Fig. 5 is the C-C sectional schematic diagram of Fig. 2;

FIG. 6 is a schematic cross-sectional view along D-D of FIG. 2 .

In the figure: 1. Y-branched waveguide digital optical switch, 2. S-curved waveguide type variable optical attenuator, 3. Input waveguide, 4. Filling part of bifurcation angle, 5. Electrodes of Y-branched waveguide digital optical switch, 6. Waveguide of Y bifurcated part, 7. Connecting waveguide, 8. Tapered transition waveguide, 9. Electrodes of S-curved waveguide type variable optical attenuator, 10. S-curved waveguide, 11. Silicon or glass substrate, 12 1. Waveguide cladding (that is, including upper and lower confinement layers).

Detailed ways

As shown in FIG. 2 , it is composed of a Y-branched waveguide digital optical switch 1 and S-curved waveguide variable optical attenuators 2 respectively connected to both ends of a Y-branched waveguide digital optical switch 1 .

As shown in Figure 4, the S-curved waveguide type variable optical attenuator 2 is sequentially connected by a connecting waveguide 7 through a tapered transition waveguide 8, an S-curved waveguide 10, another tapered transition waveguide 8 and another connecting waveguide 7, and the S-curved The electrodes 9 of the waveguide-type variable optical attenuator part are respectively located on the side with the small radius of curvature of the S-shaped bend; the distance between the edge of the electrode on one side of the edge of the waveguide and the edge of the S-shaped bend waveguide is ± 1 micron, and the S-shaped waveguide on both sides The electrodes 9 of the type variable optical attenuator part are respectively connected in series with the electrodes 5 of the Y-branched waveguide digital optical switch part.

As shown in FIG. 3 , the bifurcation angle α of the Y bifurcated waveguide digital optical switch 1 is 0.3-1.0°, and the bifurcation angle filling part 4 is filled at the bifurcation, and its top width d is 1.5-2 μm.

Figure 5 is a cross-sectional view of the waveguide structure at CC' in Figure 2. On a silicon or glass substrate 11, the waveguide cladding 12 (including the upper and lower confinement layers), the core layer of the S-curved waveguide 10, and the S-curved waveguide are fabricated respectively. type variable optical attenuator part of the electrode 9.

Fig. 6 is the sectional view of the waveguide structure at DD' place in Fig. 2, on silicon or glass substrate 11, make respectively waveguide cladding 12 (comprising upper and lower limit layer), the core layer of Y bifurcation part waveguide 6 and Y The electrode 5 of the bifurcated waveguide digital optical switch part.

Take the use of organic polymer materials, using its thermo-optic effect to realize the function of switching light as an example.

According to the device and structure design in Figures 2, 5 and 6, the device is fabricated on a silicon or glass substrate using a conventional organic polymer waveguide spin-coating film forming process. For a light wave with a wavelength of 1.55 μm, the refractive index of the waveguide is n=1.529/1.521 (TE/TM mode), the refractive index difference between the core layer and the cladding layer is Δn=0.005, and the thermo-optic coefficient is -2.5×10 ^-4 /K ^-1 , the thickness of the lower limiting layer is 10 μm, the thickness of the core layer is 7 μm, and the total thickness of the core layer and the cladding layer is 19 μm. After the Y bifurcation, there is an S-curved waveguide. The width of the waveguide in the Y-bifurcated area and the input and connecting waveguide is selected as 7 μm. The width of the waveguide in the S-shaped curved part is selected as 5 μm. The tapered waveguide transition, the radius of curvature of the S-shaped bending part is greater than 600 μm. Y bifurcation angle is α=0.4° Y bifurcation sharp part fill correction d=1.5μm, distance between Y bifurcation ends L=20μm; electrode can be chromium-gold double-layer metal electrode with a thickness of about 200-300nm, Y The electrodes in the bifurcated part are divided into two parts, the width of which is the same as that of the waveguide. The angle between the electrodes in area A and the waveguide is α, and the electrodes in area B are parallel to the waveguide. The length and specific position of each electrode are related to the properties of the material used in the device and α Angle related. The inner side of the S-curved waveguide is designed with series electrodes, and the outer edge of the electrodes basically coincides with the inner side of the waveguide, and is connected in series with the electrodes of the Y bifurcation part.

The S-curved waveguide part has two functions, one is to separate the output end to a distance that can be coupled with the fiber array, and the other is to function as a variable optical attenuator. When the right electrode works, first use the mode separation principle of Y bifurcation to couple most of the light energy to the left waveguide, and the remaining very little light energy enters the S-shaped curved waveguide, and then use the S-shaped curved waveguide Due to the electrode action of the waveguide, a temperature gradient is generated in the vertical direction of the waveguide. Due to the negative thermo-optic coefficient of the polymer material, a corresponding refractive index gradient in the vertical direction is formed, so that the refractive index distribution is more inclined outward, and the light energy in the horizontal direction is generated. Serious leakage, the remaining very little light energy is attenuated by the variable optical attenuator of the S-curved waveguide structure, so that the extinction ratio performance of the optical switch can be greatly improved. Figure 1 is an effect diagram of an optical switch simulated by the BPM method.

The function of Y bifurcation is mainly to complete the distribution of energy, and the performance of high extinction ratio is mainly realized by the variable optical attenuator, so the angle of Y bifurcation can be enlarged, and at the same time, considering the problem of manufacturing process, fill in the bifurcation For the sharp corners, the width of the top is within the width that is easy to achieve in the general waveguide manufacturing lithography process, such as 1.5 μm. The simulation analysis using BPM (beam transmission method) shows that the increase in insertion loss caused by this correction is only about 0.15dB. The distance (L) between the ends of the Y bifurcation is designed to be 20 μm. At this time, the mutual coupling between the two ends of the bifurcation is very small, which can shorten the length of the Y bifurcation waveguide.

Claims (2)

1. A low crosstalk digital optical switch, characterized in that: a Y bifurcated waveguide digital optical switch (1) and a Y bifurcated waveguide digital optical switch (1) two ends connected to each other, made of organic polymer material The manufactured S-bend waveguide variable optical attenuator (2) is integrated, and the electrodes (9) of the S-bend waveguide type variable optical attenuator are respectively located on the side of the S-bend with a smaller curvature radius. 2. The low-crosstalk digital optical switch according to claim 1, characterized in that: the S-curved waveguide type variable optical attenuator (2) sequentially consists of a connecting waveguide (7) via a tapered transition waveguide (8), an S-curved waveguide (10), another tapered transition waveguide (8) is connected with another connection waveguide (7), the distance between the electrode edge on one side of the S-curved waveguide edge and the edge of the S-curved waveguide is ± 1 micron, and the S-curved waveguide on both sides The electrodes (9) of the waveguide type variable optical attenuator part are respectively connected in series with the electrodes (5) of the Y-branched waveguide digital optical switch part.

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