JP6622669B2 - Changeover switch - Google Patents

Description

  The present invention relates to a changeover switch.

  In general, a change-over switch that can switch a plurality of light beams that have passed through an optical waveguide such as an optical fiber to a plurality of different optical paths is configured based on a spatial optical component using a mirror or the like as shown in Patent Document 1. Has been. The reduction of insertion loss of these changeover switches has been promoted, and a changeover switch having a relatively low insertion loss of less than 1 dB has been realized.

  However, the above-described changeover switch is combined with a measuring instrument that receives and measures Rayleigh scattered light of an optical fiber based on OTDR (Optical Time Domain Reflectometer) for an optical path switching method using a spatial optical component. When used, a dead zone is created by Fresnel reflection at the switching portion, and there are cases where a portion that cannot be measured is generated. In order to cope with such a situation and realize a changeover switch that suppresses Fresnel reflection, a method of switching by physically connecting an optical fiber or the like is effective (for example, see Patent Document 2).

  In addition to the changeover switch that suppresses Fresnel reflection as described above, for example, as shown in Patent Documents 2 and 3, a changeover method using an optical waveguide has been proposed. In the optical path changeover switch described in Patent Document 2 and the optical fiber core line switching device described in Patent Document 3, switching is performed by devising an optical waveguide axis alignment method.

JP 2014-67004 A JP-A-6-300979 JP 2014-77919 A

  A common single mode fiber has a core diameter of about 10 μm. When an optical waveguide such as an optical fiber is physically connected, it is necessary to align the core in accordance with the core diameter. However, due to the current accuracy of mechanical control, it is difficult to manually realize an alignment mechanism with an accuracy within 10 μm, and there is a problem that connection loss increases or switching is not performed normally. As a method for solving this problem, there is a method of using an optical fiber with an expanded core diameter to keep it within the above-mentioned range of mechanical accuracy. However, the propagation mode of guided light becomes multimode, which may increase insertion loss. There was no problem.

  The present invention has been made in view of the above-described problems, and provides a changeover switch that allows an error in a mechanical control mechanism.

According to one aspect of the present invention, a first input unit including a first waveguide to which an optical fiber is connected , an axis can be moved in a direction orthogonal to the extending direction of the optical fiber, and the first waveguide is connected. A second input section having a plurality of second waveguides having a rectangular cross section, and a second input portion arranged in parallel to the axis line at a predetermined interval in a direction orthogonal to the axis line of the second waveguide. combined in an output section having a plurality of third waveguides, and one of the axis of one of said moving the second input unit the second waveguide axis and multiple third waveguide and a Ru aligning mechanism is connected Te, the alignment mechanism, the central portion of the respective ends of the second waveguide side of the third waveguide and the first waveguide in a plan view and width and protrusion-shaped fitting portion but to shrink outward, the center portion of both end portions of the extending direction of the second waveguide, in plan Width is composed of the fitted portion of the groove shape to shrink inward, the second waveguide, and each of the plurality of the third waveguide, the width of the output side of the second waveguide wherein The width dimension on the input side of the second waveguide is larger than the width dimension on the input side of the third waveguide, and the width dimension on the output side of the second waveguide is equal to the second waveguide and the third waveguide. waveguide mode number widest portion of the waveguide is 2, the cut-off wavelength of the third waveguide and said second waveguide is a changeover switch, wherein less der Rukoto 1550 nm.

According to one aspect of the present invention, a first input unit including a first waveguide to which an optical fiber is connected, an axis can be moved in a direction orthogonal to the extending direction of the optical fiber, and the first waveguide is connected. A second input section having a plurality of second waveguides having a rectangular cross section, and a second input portion disposed in parallel to the axis line at a predetermined interval in a direction orthogonal to the axis line of the second waveguide. The output unit including the plurality of third waveguides and the second input unit are moved to connect the axis of the second waveguide and one of the plurality of third waveguides together. An alignment mechanism, and the alignment mechanism has a central portion of each end of the first waveguide and the third waveguide on the second waveguide side, and the width in plan view faces outward. The protrusion-shaped fitting portion that shrinks and the center portion of both end portions in the extending direction of the second waveguide are viewed in plan view. The groove is configured to have a groove-shaped fitting portion whose width decreases toward the inside. Each of the second waveguide and the plurality of third waveguides has a width dimension on the output side of the second waveguide. The width dimension on the input side of the second waveguide is larger than the width dimension on the input side of the third waveguide, and the width dimension on the output side of the second waveguide is equal to the second waveguide and the third waveguide. The change-over switch is characterized in that the number of waveguide modes in the widest part of the waveguide is 2, and the cutoff wavelength of the waveguide is 1310 nm or less .

  According to the selector switch according to one aspect of the present invention, an error in mechanical accuracy is allowed. In addition, a single-mode optical waveguide switching structure having a waveguide width that allows an error in mechanical accuracy can be easily configured.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the selector switch of 1st embodiment to which this invention is applied, (a) is a top view in the state in which the input port and the some output port were spaced apart, (b) is Ib-Ib shown to (a). It is sectional drawing seen by the arrow at the line. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the changeover switch of 1st embodiment to which this invention is applied, (a) is a top view in the state in which the input port and the some output port were connected, (b) is Ib- shown to (a). It is sectional drawing seen by the arrow at Ib line. It is a graph which shows the relationship between the waveguide width in the design example of the changeover switch of 1st embodiment to which this invention is applied, and the cutoff wavelength with respect to a relative refractive index difference, (a) sets the height of an optical waveguide to 4 micrometers. (B) is a diagram when the height of the optical waveguide is set to 6 μm, and (c) is a diagram when the height of the optical waveguide is set to 8 μm. In the design example of the optical changeover switch according to one aspect of the present invention, the relationship between the waveguide width and the loss improvement amount from the misalignment loss between the SMFs with respect to the relative refractive index difference when the misalignment amount is set to 5 μm. (A) is a figure when the height of the optical waveguide is set to 4 μm, (b) is a figure when the height of the optical waveguide is set to 6 μm, and (c) is an optical waveguide. It is a figure at the time of setting the height of a waveguide to 8 micrometers. In the design example of the optical changeover switch according to one aspect of the present invention, the relationship between the waveguide width and the loss improvement amount from the misalignment loss between the SMFs with respect to the relative refractive index difference when the misalignment amount is set to 10 μm. (A) is a figure when the height of the optical waveguide is set to 4 μm, (b) is a figure when the height of the optical waveguide is set to 6 μm, and (c) is an optical waveguide. It is a figure at the time of setting the height of a waveguide to 8 micrometers. In the design example of the optical changeover switch according to one aspect of the present invention, the relationship between the waveguide width and the loss improvement amount from the misalignment loss between the SMFs with respect to the relative refractive index difference when the misalignment amount is set to 15 μm. (A) is a figure when the height of the optical waveguide is set to 4 μm, (b) is a figure when the height of the optical waveguide is set to 6 μm, and (c) is an optical waveguide. It is a figure at the time of setting the height of a waveguide to 8 micrometers. FIG. 4 is a graph showing a region that becomes two modes with respect to the width of the waveguide and the relative refractive index difference in the design example of the optical changeover switch according to one aspect of the present invention, and (a) sets the height of the optical waveguide to 4 μm. (B) is a diagram when the height of the optical waveguide is set to 6 μm, and (c) is a diagram when the height of the optical waveguide is set to 8 μm.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The drawings used in the following description are schematic, and the length, width, thickness ratio, and the like are not necessarily the same as the actual ones, and can be changed as appropriate.

  In general, since an optical fiber has a concentric circular cross-sectional structure, it is necessary to reduce the relative refractive index difference of the optical fiber in order to realize a single mode while increasing the core diameter. In contrast, optical waveguides (simply referred to as waveguides) such as the core of a planar lightwave circuit (PLC) have a rectangular shape, making it easy to change the height and width. It is possible to reduce the height and increase only the width. In the present invention, the relative refractive index difference, height, and width of the rectangular optical waveguide are controlled to realize a waveguide width that allows an error in mechanical accuracy.

(First embodiment)
FIG. 1 shows a configuration of a changeover switch 90 according to the first embodiment to which the present invention is applied. As shown in FIGS. 1A and 1B, the changeover switch 90 includes an input port 129, a plurality of output ports 127, an axis of the input port 129, and one axis of the plurality of output ports 127. And an aligning mechanism 130 for matching. The plurality of output ports 127 are arranged in parallel to the axial direction J with a predetermined interval Λ in the direction K orthogonal to the axial direction J. The predetermined interval Λ is, for example, 250 μm, and corresponds to twice the outer diameter of a normal single mode optical fiber.

  As shown in FIG. 1B, the input unit 114 having the input port 129 includes a substrate 105 on the base 100 of the changeover switch 90 and a waveguide 101 provided on the substrate 105. The output unit 112 having the output port 127 includes a substrate 106 on the base 100 and a waveguide 102 provided on the substrate 106.

A waveguide 103 connectable to the waveguides 101 and 102 and the waveguide 101 (that is, the input port 129) is an optical path for propagating single-mode light. That is, the input port 129 and the output port 127 are constituted by single-mode waveguides 101 and 102, respectively.
The optical fiber 104 connected to the waveguide 101 and the optical fiber 107 connected to the waveguide 102 are, for example, ITU-T G. Standard SMF (Single Mode Fiber) shown in 652D and the like. In addition, illustration of the optical fibers 104 and 107 is abbreviate | omitted in FIG.1 (b).
The waveguide 103 has a configuration corresponding to an input waveguide.

  As shown in FIG. 1A, the waveguides 102 and 103 are configured to be movable along the longitudinal direction D1 of the base 100 of the changeover switch 90 (that is, the axial direction J and the direction parallel to the axial direction J). ing. On the other hand, the waveguide 101 is configured to be movable along the short direction D2 (that is, the direction K) orthogonal to the longitudinal direction of the base 100.

The output side width dimension w2 of the input port 129 is larger than the input side width dimension w1 of the input port 129. The input side width dimension of the output port 127 is equal to the output side width dimension w2 of the input port 129. The output side width dimension of the output port 127 is equal to the input side width dimension w1 of the input port 129.
That is, the top view (plan view) shape of the output port 127 is the same as the top view shape in which the input side and the output side of the input port 129 are interchanged. The waveguides 101 and 102 have a so-called taper shape in a top view. Specifically, it is formed with a certain width dimension on the input side of the waveguide 101, but is formed so that the width dimension gradually increases toward the output side of the waveguide 101. Since the so-called tapered shape is formed in this way, in the waveguide 101, the mode field diameter of the light input to the changeover switch 90 is enlarged. Even if the alignment mechanism 130 larger than the core diameter of the waveguide 101 is used, highly accurate alignment can be performed.

  The light traveling direction (hereinafter referred to as traveling direction) and the horizontal direction in the waveguide 101 coincide with the traveling direction and horizontal direction of the waveguides 102 and 103. The waveguide 102 disposed on the substrate 106 has two or more (ie, a plurality) output ports 127, and FIG. 1A illustrates a configuration having three output ports 127.

The alignment mechanism 130 is provided on the input surface 106 a facing the input port 129 and the output surface 105 e facing the output port 127 and can be fitted to the fitting portion 120. The unit 122 is configured.
The fitting portion 120 is a V-shaped protrusion that decreases as it protrudes from the input surface 106a in a top view. The fitted portion 122 is a V-shaped groove that shrinks inward from the output surface 105e in a top view.
The interval between the fitted portions 122 adjacent in the K direction is 250 μm, similar to the predetermined interval Λ.

  With the above-described configuration, the waveguide 101 and the waveguide 102 are aligned with the alignment accuracy corresponding to the machining accuracy, and the input port 129 and the output port 127 as shown in FIGS. Can be connected.

According to the changeover switch 90 described above, an error in mechanical accuracy is allowed. In addition, a single-mode optical waveguide switching structure having a waveguide width that allows an error in mechanical accuracy can be easily configured.
In addition, the alignment mechanism 130 is configured by the fitting portion 120 made of a V-shaped protrusion and the fitted portion 122 made of a V-shaped groove, thereby sufficiently allowing a general mechanical accuracy error. It becomes possible.

(Second embodiment)
The changeover switch (not shown) of the second embodiment to which the present invention is applied includes the same components as those of the changeover switch 90 of the first embodiment shown in FIG. The waveguide 101 and the optical waveguide related to the waveguide 102 have the same structure. In the change-over switch according to the second embodiment, a plurality of waveguides 101 having the same structure are arranged in parallel, and the input / output directions are symmetrical between the input unit 110 and the output unit 112. The waveguide 101 and the waveguide 103 may be integrated in advance.

  In the change-over switch of the second embodiment, the waveguides 101, 102, and 103 have a width w, a height h, a relative refractive index difference Δ between the core and the clad, and a length L, respectively. The relative refractive index difference Δ is obtained by the following equation (1). The width w and height h shown below represent the width and height of the core portions of the waveguides 101, 102, and 103.

In the above equation (1), n ₁ is the refractive index of the core portion of the waveguides 101, 102, and 103, and n ₂ is the refractive index of the cladding portion made of quartz (SiO ₂ ) of the waveguides 101, 102, and 103. It is.

  Regarding the refractive index n, based on the following equation (2) and coefficient, the refractive index of the core part was adjusted according to the relative refractive index difference Δ with the value of the curve obtained by equation (2).

(Coefficient of SiO ₂ )
a1 = 0.6961663
a2 = 0.4079426
a3 = 0.8974794
b1 = 0.004679148
b2 = 0.01351206
b3 = 97.934002
(Coefficient of refractive index of core part)
a1 = 0.7136824
a2 = 0.4254807
a3 = 0.8964226
b1 = 0.003808952
b2 = 0.01614969
b3 = 97.93401

  FIG. 3 shows a result of calculating a region that becomes a single mode with respect to the width w and relative refractive index difference Δ of each waveguide (that is, a region where the E21 mode is cut off). FIGS. 3A, 3B, and 3C show calculation results when the height h of the waveguide is set to 4 μm, 6 μm, and 8 μm, respectively. The calculation results were calculated using a two-dimensional finite element method (FEM) based on scalar approximation.

  4, 5, and 6 show the amount of improvement in the axis misalignment loss from the SMF with respect to the waveguide structure when the axis misalignment amount (horizontal deviation of the waveguide cross section) is set to 5 μm, 10 μm, and 15 μm, respectively. Show. 4 to 6 show the off-axis loss when the wavelength λ is 1550 nm. The off-axis loss η was calculated using the following well-known formula (3) (see, for example, “optical fiber technology supporting the IT era”, IEICE, Corona, etc.).

In the above equation (3), w represents the mode field radius in the waveguide, w ₁ represents the mode field radius in the _first waveguide, and w ₂ represents the mode field radius in the other waveguide. When calculating the connection loss between the same waveguides, w ₁ and w ₂ are equal.

  As shown in FIGS. 3A and 4A, when the height h of the waveguides 101, 102, 103 is set to 4 μm, the width w of the waveguides 101, 102, 103 is 13.2 μm, When Δ is set to 0.4%, the connection loss can be improved by about 3.8 dB when the axis deviation is 5 μm at the wavelength of 1550 nm.

  Further, as shown in FIGS. 3B and 4B, when the height h of the waveguides 101, 102, 103 is set to 6 μm, the width w of the waveguides 101, 102, 103 is set to 13.2. When 2 μm and Δ are set to 0.35%, the connection loss can be improved by about 3 dB at a wavelength of 1550 nm when the amount of axis deviation is 5 μm.

  As shown in FIGS. 3C and 4C, when the height h of the waveguides 101, 102, and 103 is set to 8 μm, the width w of the waveguides 101, 102, and 103 is set to 13.2. When 2 μm and Δ are set to 0.28%, the connection loss can be improved by about 4 dB at a wavelength of 1550 nm when the amount of axial deviation is 5 μm.

  Next, FIG. 5 shows the connection loss improvement amount at a wavelength of 1550 nm when the axis deviation amount is set to 10 μm. 5A, 5B, and 5C show calculation results when the waveguide height h is 4 μm, 6 μm, and 8 μm, respectively.

  Next, FIG. 6 shows an improvement in connection loss at a wavelength of 1550 nm when the amount of axial deviation is set to 15 μm. (A), (b), and (c) of FIG. 6 are calculation results when the height h of the waveguide is 4 μm, 6 μm, and 8 μm, respectively. In the present invention, an effective structure may be selected as appropriate from FIGS. 4, 5, and 6 in accordance with an assumed amount of axis deviation.

The cut-off wavelength of the width dimension w2 portion (widest portion) of the waveguides 101, 102, 103 may be 1310 nm or less.
In addition, the cutoff wavelength of the width dimension w2 of the waveguides 101, 102, 103 may be 1250 nm or less.

(Third embodiment)
The changeover switch (not shown) of the third embodiment to which the present invention is applied includes the same components as those of the changeover switch 90 of the first embodiment shown in FIG. Also in the third embodiment, the waveguide 101 and the optical waveguide according to the waveguide 102 have the same structure. The changeover switch according to the third embodiment relates to a structure in which the waveguide modes at the widest part of the waveguides 101, 102, and 103 are limited to the fundamental mode (E ₁₁ ) and the first higher-order mode (E ₂₁ ).

When the waveguide mode is a two-mode, when an axial misalignment occurs in the matching of the two waveguides, the propagated E ₁₁ mode is coupled to the E ₂₁ mode and the radiation mode. If the waveguide is long and the number km is the signal degradation caused by the group delay difference E ₁₁ mode and the E ₂₁ mode group delay difference for the changeover switch is assumed to be a short distance of less than 1m of the present invention There is no need to consider. Further, even if the widest portion has two modes, as shown in FIG. 1, the E ₂₁ mode can be cut off by narrowing the width of the waveguide to a single mode. Third embodiment, by the widest portion to the second mode waveguide, it relates to the structure capable of reducing the axial displacement losses by expanding the MFD of E ₁₁ modes. FIG. 7 shows the result of calculating a region that becomes two modes with respect to the waveguide widths w and Δ (region where the E ₃₁ mode is cut off). FIGS. 7A, 7B and 7C show calculation results by FEM when the height h of the waveguide is set to 4 μm, 6 μm and 8 μm, respectively.

  As shown in FIGS. 7A and 4A, when the height h of the waveguides 101, 102, 103 is set to 4 μm, the width w of the waveguides 101, 102, 103 is 18.8 μm, When Δ is 0.4%, the connection loss can be improved by about 5.7 dB when the axis deviation is 5 μm at the wavelength of 1550 nm.

  As shown in FIGS. 7B and 4B, when the height h of the waveguides 101, 102, 103 is set to 6 μm, the width w of the waveguides 101, 102, 103 is set to 18.8 μm. When Δ is 0.35%, the connection loss can be improved by about 5 dB when the axis deviation is 5 μm at the wavelength of 1550 nm.

  As shown in FIGS. 7C and 4C, when the height h of the waveguides 101, 102, 103 is set to 8 μm, the width w of the waveguides 101, 102, 103 is 18.8 μm, When Δ is 0.28%, the connection loss can be improved by about 5 dB when the axis deviation is 5 μm at the wavelength of 1550 nm.

The change-over switch described above realizes the change-over switch 90 with low loss and reduced Fresnel reflection that makes use of the characteristics of optical fibers and maintains a single mode especially in the SMF and allows for errors in mechanical accuracy. can do.
Specifically, while maintaining high SMF propagation accuracy and low insertion loss, the waveguides 102 and 103 are moved in the longitudinal direction D1 of the base portion of the optical switch, and the waveguide 101 is moved to the base portion. The desired waveguides 101, 102, and 103 can be very easily connected to each other if they can be moved in the short direction D2 orthogonal to the longitudinal direction.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

  For example, the fitting part 120 and the fitted part 122 of the alignment mechanism 130 are not limited to a V shape in a top view, and may be formed in a rectangular shape or a U shape. Further, the fitting portion 120 and the fitted portion 122 of the alignment mechanism 130 are provided with protrusions provided so as to protrude in the optical axis direction of the waveguides 101, 102, 103 (that is, the direction parallel to the axial direction J). It is not limited to a groove | channel, The protrusion and groove | channel currently formed in the thickness direction of the base 100 may be sufficient.

The light changeover switch of the present invention can be widely used in application fields having the purpose of receiving light that has passed through an optical fiber and inputting light to one optical path selected from a plurality of optical paths.
Further, such a light changeover switch can be used as an emergency signal transmission source of the user in an emergency. In that case, it becomes possible to transmit individual information depending on which core part is connected in the waveguides 101, 102, and 103.

90 ... changeover switches 101, 102, 103 ... waveguides 105, 106 ... centering part 127 ... output port 129 ... input port 120 ... fitting part 122 ... mated part 130 ... centering mechanism

Claims (2)

A first input unit having a first waveguide to which an optical fiber is connected ;
A second input unit comprising a plurality of second waveguides having a rectangular cross section to which the first waveguide can be connected, the axis line being movable in a direction perpendicular to the extending direction of the optical fiber;
An output unit including a plurality of third waveguides arranged in parallel to the axis at a predetermined interval in a direction orthogonal to the axis of the second waveguide, and having a rectangular cross section ;
And one of the axis aligning mechanism Ru is connected together of said third waveguide axis and multiple second waveguide by moving the second input unit,
Equipped with a,
The alignment mechanism is
A center portion of each end of the first waveguide and the third waveguide on the second waveguide side has a protruding fitting portion whose width in plan view decreases toward the outside, and the second The center part of both ends in the extending direction of the waveguide is constituted by a groove-shaped mating portion whose width in plan view decreases toward the inside ,
Each of the second waveguide and the plurality of third waveguides has a width dimension on the output side of the second waveguide larger than a width dimension on the input side of the second waveguide. The width dimension on the input side of the waveguide is equal to the width dimension on the output side of the second waveguide,
And wherein the second waveguide 3 is guided modes number of widest part of the waveguide 2, the second waveguide and the third waveguide cutoff wavelength characteristics less der Rukoto 1550nm Changeover switch to be used. A first input unit having a first waveguide to which an optical fiber is connected;
A second input unit including a plurality of second waveguides having a rectangular cross section to which the first waveguide can be connected, the axis line being movable in a direction perpendicular to the extending direction of the optical fiber;
An output unit including a plurality of third waveguides arranged in parallel to the axis at a predetermined interval in a direction orthogonal to the axis of the second waveguide, and having a rectangular cross section;
An alignment mechanism that moves the second input unit to connect the axis of the second waveguide and one of the plurality of third waveguides together; and
With
The alignment mechanism is
A center portion of each end of the first waveguide and the third waveguide on the second waveguide side has a protruding fitting portion whose width in plan view decreases toward the outside, and the second The center part of both ends in the extending direction of the waveguide is constituted by a groove-shaped mating portion whose width in plan view decreases toward the inside,
Each of the second waveguide and the plurality of third waveguides has a width dimension on the output side of the second waveguide larger than a width dimension on the input side of the second waveguide. The width dimension on the input side of the waveguide is equal to the width dimension on the output side of the second waveguide,
The changeover switch , wherein the number of waveguide modes of the widest part of the second waveguide and the third waveguide is 2, and the cutoff wavelength of the waveguide is 1310 nm or less .

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