KR20020005219A - Optical Path Controlling two by two Optical Switch - Google Patents

Abstract

PURPOSE: A two-by-two light switch for controlling light pathway is provided to do an operation regardless to a wavelength and polarity on switching and to improve a crosstalk property with an initial pathway maintained without power consumption. CONSTITUTION: First and second input asymmetric Y-branch optical waveguides are disposed in parallel on the sides of input terminals. The same is true to first and second asymmetric Y-branch optical waveguides. One wider optical waveguide(123) of two branch optical waveguides of the second asymmetric Y-branch optical waveguide is connected with one wider optical waveguide(133) of the first asymmetric Y-branch waveguide and an arc curved optical waveguide(160). The other narrower one of the first asymmetric Y-branch waveguide is connected with the other narrower optical waveguide of the first asymmetric Y-branch waveguide. The other narrower optical waveguide of the second asymmetric Y-branch optical waveguide is connected with the other narrower optical waveguide of the second asymmetric Y-branch optical waveguide.

Description

Optical Path Controlling two by two Optical Switch

The present invention relates to an optical switch for optical path control in an optical communication and optical exchange system. In detail, the present invention is composed of four asymmetrical Y-branched optical waveguides and two circular arc-shaped optical waveguides connecting them. The present invention relates to a 2 × 2 optical switch for optical path control that maintains an initial path without power consumption and improves crosstalk characteristics during optical path control.

Optical switch is an essential element for optical path control in optical communication and optical exchange system. It should be independent of wavelength and polarization, have good crosstalk, and have low power consumption during switching.

As a conventional technology of such an optical switch, [History: "Thermooptical Digital Switch Arrays in Silica-on-Silicon with Defined Zero-Voltage State." Proposed by Martin Hoffmann, Peter Kopka, and Edgar Voges, IEEE Journal of Lightwave Technology, vol. 16, no. 3, pp. 395-400, published: 1998. This optical switch has a structure using a silica material and an asymmetric X-branch optical waveguide. However, only one X-branch optical waveguide is used, so the power consumption of the optical switch is large because it is not connected in series.

As another conventional technique, [Paper name: "Low-Power Consumption Silica-Based 2 ×" proposed by R. Kasahara, M. Yanagisawa, A. Sugita, T. Goh, M. Yasu, A. Himeno, and S. Matsui. 2 Thermooptic Switch Using Trenchde Silicon Substrate ", Geography: IEEE Photonics Technology Letters, vol. 11, no. 9, pp. 1132-1134, published: 1999]. This optical switch is a structure using a directional coupler can maintain the initial path without power consumption, but has a disadvantage of high power consumption because it depends on the wavelength and polarization during operation.

In order to solve these problems, a thermo-optic switch using a polymer having a large thermo-optic effect has recently been mainly researched and published. As a representative thermo-optic switch of such a switch, proposed by R. Moosbruger, G Fischbeck, C. Kostrzwa and K. Petermann [Thesis name: "Digital optical switch based on 'oversized' polymer rib waveguides", . 32, no. 6, pp. 544-545, Announcement: 1996]. This switch has the advantage of reducing power consumption when switching due to the thermo-optic coefficient that is about 10 times larger than silica, but it is consumed in all switching states because it is implemented using symmetrical Y-branched optical waveguide. There is this.

An object of the present invention for solving the above problems of the prior art is to configure by connecting four asymmetrical Y-branch optical waveguides and two arc-curve optical waveguides, operating regardless of the wavelength and polarization during switching and without power consumption An object of the present invention is to provide a 2 × 2 optical switch for optical path control that improves crosstalk characteristics while maintaining an initial path.

1 is a structural diagram of a 2 × 2 optical switch for controlling an optical path consisting of an asymmetric Y-branch optical waveguide according to an embodiment of the present invention;

2 is a cross-sectional view taken along the line A-A of FIG.

3 is a graph showing the results of numerical simulation of crosstalk characteristics according to the difference (ΔW) of the branched optical waveguide width of the input Y-branched optical waveguide.

4 is a graph showing the results of numerical simulation of crosstalk and additional loss according to the change in the radius of curvature of an arc-curve optical waveguide;

FIG. 5 is a graph illustrating optical power transmission characteristics according to power applied to a 2 × 2 optical switch for controlling an optical path according to the present invention.

※ Explanation of code about main part of drawing ※

110: asymmetric Y-branch optical waveguide at input 1

120: Asymmetric Y-branch optical waveguide at input 2

130: Asymmetric Y-branch optical waveguide at output 1

140: Asymmetric Y-branch optical waveguide at output 2

150, 160: arc curve optical waveguide

R: radius of curvature of arc-curve waveguide

W ₁ : The width of the narrow one-branch optical waveguide among the branch waveguides of the asymmetric Y-branch optical waveguide

W ₂ is the width of another wider branching waveguide among the branching waveguides of the asymmetrical Y-branching optical waveguide.

θ ₁ : Branch angle which is the angle between branch waveguides of the input asymmetrical Y-branching optical waveguide

θ ₂ : crossing angle of circular curve optical waveguide

2 × 2 optical switch for controlling the optical path according to the present invention for achieving the above object,

A first input asymmetric Y-branch optical waveguide for outputting the optical signal input through the first input terminal to one of the two branch optical waveguides, and two optical signals inputted through the second input terminal. A second input asymmetrical Y-branch optical waveguide outputting to one of the branching optical waveguides, and an optical signal inputted through the branching optical waveguide of one of the two branching optical waveguides to the first output terminal. A first output asymmetric Y-branch optical waveguide, and a second output asymmetric Y-branch optical waveguide for outputting an optical signal input through one branch optical waveguide of two branch optical waveguides to a second output terminal,

One branch optical waveguide of the first input asymmetrical Y-branch optical waveguide is connected to one branch optical waveguide of the second output asymmetrical Y-branch optical waveguide and one branch optical waveguide of the second input asymmetrical Y-branch optical waveguide. Is cross-connected with one branched optical waveguide of the first output asymmetrical Y-branch optical waveguide, and the other branched optical waveguide of the first input asymmetrical Y-branch optical waveguide is the first output asymmetrical Y-branch The other branched optical waveguide of the second input asymmetrical Y-branch optical waveguide and the other branched optical waveguide of the second output asymmetrical Y-branch optical waveguide and connected to the other branched optical waveguide of the optical waveguide.

The first and second input asymmetrical Y-branch optical waveguides and the first and second output asymmetrical Y-branch optical waveguides of the first and second branched optical waveguides are formed differently from each other,

The cross state and the bar state are characterized in that connected to change depending on the external conditions.

Advantageously, a first circular curve optical waveguide connecting between one branch optical waveguide of the first input asymmetrical Y-branch optical waveguide and one branch optical waveguide of the second output asymmetrical Y-branch optical waveguide, and And a second arc optical waveguide connecting between one branch optical waveguide of the second input asymmetrical Y-branch optical waveguide and one branch optical waveguide of the first output asymmetrical Y-branch optical waveguide.

Hereinafter, a 2 × 2 optical switch for controlling an optical path according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a structural diagram of a 2 x 2 optical switch for controlling an optical path according to the present invention. First and second input asymmetrical Y-branched optical waveguides 110 and 120 are arranged in parallel on the input terminals 111 and 121, and the first and second output asymmetrical Y-branched optical waveguides are also arranged on the output terminals 131 and 141. 130 and 140 are arranged in pairs in parallel. The wide one branched optical waveguide 113 of the two branched optical waveguides 112 and 113 of the first input asymmetrical Y-branched optical waveguide 110 is the two of the second output asymmetrical Y-branched optical waveguide 140. One of the branching optical waveguides 142 and 143 is connected by a wider branching optical waveguide 143 and an arc-curve optical waveguide 150.

The wider one branched optical waveguide 123 of the two branched optical waveguides 122 and 123 of the second input asymmetrical Y-branched optical waveguide 120 has a width of the first output asymmetrical Y-branched optical waveguide 130. It is connected by a wide one-branch optical waveguide 133 and an arc curved optical waveguide 160.

The other narrow branched optical waveguide 112 of the first input asymmetrical Y-branch optical waveguide 110 is narrower than the other branched optical waveguide 132 of the first output asymmetrical Y-branched optical waveguide 130. Another branching optical waveguide 122 connected directly and having a narrow width of the second input asymmetrical Y-branching optical waveguide 120 is another narrowing optical waveguide of the second output asymmetrical Y-branching optical waveguide 140. Is directly connected with 142.

Here, the "asymmetrical" meaning of the asymmetrical Y-branched optical waveguides is defined as two branches of each of the first and second input asymmetrical Y-branched optical waveguides and the first and second output asymmetrical Y-branched optical waveguides. The width of the optical waveguide is W ₁ and W ₂ (= W ₁ -DELTA W: Difference in the output waveguide width of the Y-branching optical waveguide), and the widths of W ₁ and W ₂ are the same (△ W = 0) It is called symmetrical Y-branching optical waveguide, and it is called "asymmetrical Y-branching optical waveguide" when there is a difference in width between W ₁ and W ₂ (ΔW is not 0).

Various materials suitable for 2 × 2 optical switch for optical path control characterized by the above connection structure (silica, semiconductor, ferroelectric, polymer, etc.) are available. Among them, the thermo-optic coefficient is large and power consumption is reduced when switching. The polymer that can be used is most suitable as the material of the optical switch. In addition, the use of a polymer has the advantage that the manufacturing process is simple and mass production is easy because there is no restriction on the use of the substrate. The polymer uses a thermally stable thermosetting polymer.

Using this polymer, we implement a 2 × 2 optical switch for optical path control. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 to form an oversized rib channel waveguide structure having a large cross-sectional area. It is formed by sequentially laminating a lower cladding (thickness: 6.2 mu m), a core (thickness: 5.4 mu m), and an upper cladding (thickness: 4.7 mu m) on a silicon wiper. This structure satisfies the single mode condition despite the large difference in refractive index between the core (n _core = 1.543) and the cladding (n _clad = 1.488), and has the advantage of widening the choice of core and cladding material. At this time, the thickness of the core was 5.4 µm and the etching height was 1.5 µm. In addition, the thinner the thickness of the upper cladding (thickness: 4.7 mu m, see Fig. 2) is advantageous in terms of power consumption because the heat generated from the heat generating means is well transmitted to the core (thickness: 5.4 mu m, see Fig. 2). . If the refractive index difference between the core and the cladding material is large, the thickness of the upper cladding may be thinly coated. As a result, the optical switch consumes little power during operation.

Photo-BCB (Phtosensitive Benzocyclobutene, Tg> 350 ℃) and PFCB (Perfluorocyclobutane, Tg> 450 ℃) were used as core and cladding materials, respectively. Each refractive index is 1.543 for the core material and 1.488 for the cladding material. PFCB used as cladding material is a material that reduces loss in 1.55 ㎛ wavelength region by changing C-H bond to C-F bond in BCB molecular structure.

The 2x2 optical switch for controlling the optical path of the present invention made of the polymer has a property of lowering the refractive index when heat is applied, so that the first and second input asymmetrical Y-branched optical waveguides and the first and second output asymmetrics are used. Heat generating means are disposed on the optical waveguides 113, 123, 133, and 143, each of which has a thick width (output optical waveguide having a W ₁ width) of the respective branch optical waveguides of the red Y-branching optical waveguide.

Here, the angle (branching angle: θ ₁ ) between one branch optical waveguide of the first and second input asymmetric optical waveguides 110 and 120 and the other branch optical waveguide is 0.16 °, and the first and second input asymmetric waveguides are 0.16 °. The difference between the width (W ₁ ) of the one-wavelength optical waveguide of the red Y-branch optical waveguides 110 and 120 and the first and second output asymmetrical Y-branch optical waveguides (130,140) and the width of the other branch optical waveguide (W ₂ ). (ΔW) is 1.2 μm to 1.8 μm, the radius of curvature R of the first and second circular arc curved optical waveguides 150 and 160 is 20,000 μm to 30,000 μm, and the first and second circular arc curved optical waveguides 150 and 160 are shown. The crossing angle θ _{2 of} is between 14.5 ° and 17.8 °.

The operation of the optical path control 2x2 optical switch using the connection structure and the polymer as a component will be described.

In the initial state with no power consumption, the optical signal incident on the first input asymmetrical Y-branch optical waveguide 110 is a wide optical waveguide in which the heat generating means of the two branched optical waveguides 112 and 113 is located, that is, the effective refractive index. The wider optical beam is moved to this higher one branched optical waveguide 113 and is located in the branched optical waveguides 142 and 143 of the second output asymmetrical Y-branched optical waveguide 140 via the arc curved optical waveguide 150. The waveguide, i.e., one branch optical waveguide 143, having a higher effective refractive index, is moved. The optical signal incident on the second input asymmetrical Y-branch optical waveguide 120 is a wide optical waveguide in which the heat generating means of the two branched optical waveguides 122 and 123 is located, that is, a single branch optical waveguide having a higher effective refractive index ( 123 to the wide optical waveguide in which the heat generating means is located among the two branched optical waveguides 132 and 133 of the second output asymmetrical Y-branch optical waveguide 130 through the arc-curve optical waveguide 160. (Cross state).

On the contrary, when the respective heat generating means are acted at the same time, the effective refractive index is lowered when heat is applied due to the characteristic of the polymer, so that the effective temperature difference between each one-waveguide optical waveguide and the other branch optical waveguide is maximized, so that the first The optical signal incident on the input asymmetrical Y-branch optical waveguide 110 receives the first output asymmetrical Y-branch optical waveguide through the other branched optical waveguide 112 having the higher effective refractive index among the two branched optical waveguides 112 and 113. The optical signal incident on the second input asymmetric Y-branch optical waveguide 120 is directly transmitted to another branch optical waveguide 132 having a higher effective refractive index among the branch optical waveguides of 130, and two branch optical waveguides ( The other branched optical waveguide 142 having the higher effective refractive index among the two optical waveguides 142 and 143 of the second output asymmetrical Y-branched optical waveguide 140 through the other branched optical waveguide 122 having the higher effective refractive index among the 122 and 123. Direct to) The (Bar Status).

The next step is to design four asymmetrical Y-branch optical waveguides of a 2x2 optical switch for optical path control and two arc-shaped optical waveguides connecting them. For this purpose, numerical simulations were performed using the finite-difference beam propagation method, and numerical simulations were performed in two dimensions using the effective index method to reduce the computation time.

A divergence angle (see FIG. 1, θ ₁ ), which is an angle between one branched optical waveguides 112 and 122 of the input asymmetrical Y-branched optical waveguides 110 and 120 and the other branched optical waveguides 113 and 123, is a mode evolution phenomenon. Smaller is advantageous for the evolution effect conditions, while larger is advantageous in terms of the overall length of the device. To satisfy both of these conditions, θ ₁ = 0.16 °.

Next, in determining the different widths (W ₁ and W ₂ of FIG. 1) of the branched optical waveguides 112,113 or 122,123 of the input asymmetrical Y-branch optical waveguides 110 and 120, the difference of the widths of the branched optical waveguides (W ₁ −) W ₂ ) is determined by considering the crosstalk characteristics and power consumption during switching. Here, the difference of the widths of the branched optical waveguides (W _{1 to} W ₂ : FIG. 1) is defined as ΔW. 3 illustrates cross-sectional characteristics of the optical switch according to ΔW. As ΔW increases, the initial crosstalk characteristic is improved, but the power consumed during switching is increased. When θ ₁ = 0.16 ° and W ₁ = 6.5 μm, the numerical simulation results in FIG. 3 show that crosstalk is 20 dB or more when ΔW is larger than 1.2 μm. The range of W ₂ (= W ₁ -ΔW) can be determined by the result of ΔW and crosstalk characteristics. However, if ΔW is too large, the power consumed at the time of switching becomes large, so considering this, the range of ΔW is 1.2 μm ≦ ΔW ≦ 1.8 μm. Based on these results, the width of the output optical waveguide is determined to be W ₁ = 6.5 µm and W ₂ = 5.0 µm in the mask design.

Next, the radius of curvature (R: degrees) of the two arc-shaped optical waveguides 150,160 connecting the asymmetrical Y-branch optical waveguides 110,120 and the one-wavelength optical waveguides of the output asymmetrical Y-branch optical waveguides 130,140. 1) and the crossing angle (θ ₂ ).

As the radius of curvature R of the arc-guided waveguide becomes larger, the crossing angle increases, but the power loss in the arc-shaped waveguide becomes larger. Conversely, the smaller the radius of curvature R of the arc-shaped optical waveguide, the smaller the power loss, but the smaller the cross angle, the worse the crosstalk characteristics between the output waveguides. As a result, the radius of curvature R of the arc-shaped optical waveguide is determined so that the power loss is small and the crossing angle (see θ ₂ Fig. 1) is large. Crosstalk and additional loss results according to the change in the radius of curvature R of the two circular arc optical waveguides can be seen in FIG. 4. When the radius of curvature R is 20,000 µm or more, the additional loss is less than 0.2 dB. In the crosstalk characteristic, when the radius of curvature R is 30,000 µm or less, the additional loss is more than 30 dB. On the contrary, when R <20,000µm, the additional loss is 0.2 dB or more and the loss is too large, and when R> 30,000µm, the crosstalk characteristic is also 30 dB or less, which is not good because the crosstalk characteristic is not good. Based on this result, the range of the radius of curvature R of the arc-shaped optical waveguide is set to 20,000 µm ≤ R ≤ 30,000 µm.

Two arcuate curved cross angle (θ ₂₎ input waveguide and the distance between the output waveguides of the crystal when the optical input terminal and the output terminal of the switch of the optical waveguide (150, 160) (see Fig. 1, d) is constant in 500㎛ By the range of the radius of curvature of the arc curved optical waveguide, the crossing angle θ ₂ of the arc curved optical waveguide is determined to be 14.5 ° ≦ θ ₂ ≦ 17.8 °.

The optical output characteristics of the 2x2 optical switch for controlling the optical path of the present invention will be described. Figure 5 shows the results of measuring the optical output transmission characteristics of the optical switch according to the applied power. As can be seen from the result value (see Fig. 5), both the cross state when no heat is applied to the optical switch and the bar state when all the heat generating means are operated have a crosstalk characteristic of -25 dB or less. In addition, the power consumed by the four heat generating means during switching is about 350 kW.

That is, it can be seen that the fabricated optical path control 2 × 2 optical switch operates in a polarization independent manner while satisfying a single mode condition.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, according to the present invention, an optical asymmetric Y-branched optical waveguide structure and an arc-curve optical waveguide are connected in series by an optical path control 2x2 optical switch, which is an essential element for controlling the optical path in an optical communication and optical exchange system. By designing a structure that is designed to operate regardless of wavelength and polarization, the initial path can be maintained without any power consumption, and the crosstalk characteristic of the switch is also improved.

In addition, when designing 2 × 2 optical switch for optical path control, it is designed considering crosstalk characteristic, power loss, device length, etc. and implemented by using polymer with large thermo-optic coefficient. There is an effect to reduce.

Claims (9)

2 × 2 optical switch for optical path control having two input terminals and two output terminals and setting the path of the optical signal while the input terminals and the output terminals are connected in a cross state or a bar state To A first input asymmetric Y-branch optical waveguide for outputting the optical signal input through the first input terminal to one of the two branch optical waveguides, and two optical signals inputted through the second input terminal. A second input asymmetrical Y-branch optical waveguide outputting to one of the branching optical waveguides, and an optical signal inputted through the branching optical waveguide of one of the two branching optical waveguides to the first output terminal. A first output asymmetric Y-branch optical waveguide, and a second output asymmetric Y-branch optical waveguide for outputting an optical signal input through one branch optical waveguide of two branch optical waveguides to a second output terminal, One branch optical waveguide of the first input asymmetrical Y-branch optical waveguide is connected to one branch optical waveguide of the second output asymmetrical Y-branch optical waveguide and one branch optical waveguide of the second input asymmetrical Y-branch optical waveguide. Is cross-connected with one branched optical waveguide of the first output asymmetrical Y-branch optical waveguide, and the other branched optical waveguide of the first input asymmetrical Y-branch optical waveguide is the first output asymmetrical Y-branch The other branched optical waveguide of the second input asymmetrical Y-branch optical waveguide and the other branched optical waveguide of the second output asymmetrical Y-branch optical waveguide, connected to the other branched optical waveguide of the optical waveguide, Wherein the first and second input asymmetrical Y-branch optical waveguides and the first and second output asymmetrical Y-branch optical waveguides have different widths from one branch optical waveguide and other branch optical waveguides, The 2x2 optical switch for controlling the optical path, characterized in that the cross state and the bar state are connected depending on an external condition. The method of claim 1, A first arc optical waveguide connecting between one branch optical waveguide of the first input asymmetrical Y-branch optical waveguide and one branch optical waveguide of the second output asymmetrical Y-branch optical waveguide; And further comprising a second arc optical waveguide connecting between one branch optical waveguide of the second input asymmetrical Y-branch optical waveguide and one branch optical waveguide of the first output asymmetrical Y-branch optical waveguide. 2 × 2 optical switch for optical path control. The method according to claim 1 or 2, 2 × 2 optical switch for optical path control, characterized in that it is made of a polymer The method of claim 3, wherein The one branch optical waveguides of the first and second input asymmetrical Y-branch optical waveguides and the first and second output asymmetrical Y-branch optical waveguides have a larger effective refractive index than the other branched optical waveguides, Wherein said one branched optical waveguides of said first and second input asymmetrical Y-branched optical waveguides and said first and second output asymmetrical Y-branched optical waveguides further comprise heat generating means. × 2 optical switch. The method according to claim 1 or 2, 2 x 2 optical switch for optical path control, characterized in that the cross-sectional structure of the oversized rib channel waveguide having a large cross-sectional area. The method according to claim 1 or 2, 2 × 2 light for optical path control, wherein an angle (branching angle: θ ₁ ) between one branch optical waveguide and the other branch optical waveguide of the first and second input asymmetrical Y-branching optical waveguides is 0.16 °. switch. The method according to claim 1 or 2, The difference ΔW between the width of one branch optical waveguide of the first and second input asymmetric Y-branch optical waveguides and the first and second output asymmetric Y-branch optical waveguides and the other branch optical waveguide is 1.2. 2 x 2 optical switch for optical path control, characterized in that the micrometer to 1.8㎛. The method of claim 2, And a radius of curvature R of the first and second arc curved optical waveguides is 20,000 μm to 30,000 μm. The method according to claim 2 or 8, And a crossing angle (θ ₂ ) of the first and second circular arc optical waveguides is 14.5 ° to 17.8 °.