JP2016138966A - Optical isolator module and optical semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical isolator module capable of facilitating adjusting an optical axis when the optical isolator module is assembled into an optical semiconductor module, and downsizing a module outer shape after adjusting the optical axis.SOLUTION: An optical isolator module includes: an optical isolator provided with a Faraday rotator and polarization components disposed on two sides of the Faraday rotator, respectively; and an optical fiber having an end surface disposed on a light incident side or a light emission side and inclined at an angle θfrom a surface perpendicular to an optical axis, and is configured such that a surface, which faces the end surface of the optical fiber, of the polarization component near the end surface of the optical fiber is inclined at an angle θfrom the surface perpendicular to the optical axis, the inclined surface at the angle θand the inclined surface at the angle θare inclined in the same direction, a distance between the end surface of the optical fiber and the surface of the polarization component is less than 1 mm, and when it is assumed that an optical beam shift amount from the end surface of the optical fiber to the polarization component is ΔTand an optical beam shift amount within the optical isolator is ΔT, an absolute value of (ΔT-ΔT) is less than 0.5 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical isolator module and an optical semiconductor module such as a semiconductor optical amplifier module and a semiconductor laser module that are used by incorporating the optical isolator module.

  When light emitted from the semiconductor laser light source is reflected from the surface of a member provided in the middle of the transmission path and returns to the semiconductor laser in optical communication or optical measurement, laser oscillation becomes unstable. Therefore, in order to block the reflected return light, an optical isolator using a Faraday rotator that rotates the plane of polarization non-reciprocally is used (see, for example, Patent Document 1).

  Also, in an optical semiconductor module, in order to couple an optical fiber with a light beam incident / exited by a semiconductor chip such as a semiconductor optical amplifier, generally 1 to 3 condenser lenses are provided between the semiconductor chip and the optical fiber. Is. In recent years, there has been a strong demand for miniaturization and cost reduction of modules, and a type in which light is coupled through one or two lenses is becoming mainstream.

  When an optical isolator is incorporated in the optical semiconductor module as described above, the optical isolator is inserted between the condenser lens and the optical fiber.

  Here, as an optical isolator incorporated in an optical semiconductor module, a Faraday rotator, a pair of polarizing components disposed at both ends of the Faraday rotator, and a magnet that includes a main part are known.

When this type of optical isolator is inserted between the condenser lens and the optical fiber, for the purpose of reducing the reflected light in the optical path, as shown in FIG. The surface 114 of the polarizing component 113 facing the end face 118 of the optical fiber has an inclination angle opposite to the plane perpendicular to the optical fiber center extension axis (hereinafter also referred to as the optical axis of light propagation or simply the optical axis). It is common to arrange to have. In FIG. 6, the end face 118 of the optical fiber is inclined by an angle θ _{f ′ with} respect to a plane perpendicular to the optical fiber center extension axis when viewed in a cross section including the optical fiber center extension axis. The surface 114 facing the end surface 118 is inclined by an angle θ _{p ′ with} respect to a surface perpendicular to the optical fiber center extension axis when viewed in a cross section including the optical fiber center extension axis. At this time, the angle θ _{f ′} and the angle θ _{p ′} are directions opposite to each other with respect to a plane perpendicular to the fiber center extension axis. As a result, in the cross-sectional view shown in FIG. The space between the facing surfaces 114 is tapered from the top to the bottom (reverse taper shape). In FIG. 6, the optical isolator module 110 includes an optical isolator 111 and an optical fiber 117. The optical isolator 111 includes a Faraday rotator 112, an optical fiber side polarization component 113, a polarization component 115, and a magnet 116.

JP 2011-150208 A

  However, as described above, when the optical isolator is arranged so that the surface facing the end surface of the optical fiber of the polarization component on the optical fiber side is in the inclined direction opposite to the end surface of the optical fiber, the light beam from the optical fiber central extension axis is arranged. Since the shift (displacement) of the center position is large, it is difficult to adjust the optical axis when mounting the optical isolator module, and there is a problem that the outer shape of the module after the optical axis adjustment is large.

  The present invention has been made in view of the above problems, and facilitates optical axis adjustment when an optical isolator module is incorporated into an optical semiconductor module, and can reduce the outer shape of the module after optical axis adjustment. An object is to provide an isolator module and an optical semiconductor module incorporating the optical isolator module.

In order to achieve the above object, the present invention provides an optical isolator comprising a Faraday rotator and a pair of polarizing components disposed on both sides of the Faraday rotator, and disposed on the light incident side or the light emitting side of the optical isolator. An optical isolator module having an optical fiber with an end face inclined by an angle θ _f from a plane perpendicular to the optical axis of light propagation,
In the polarizing component disposed on the end face side of the optical fiber, a surface of the polarizing component facing the end face of the optical fiber is inclined by an angle θ _p from a plane perpendicular to the optical axis, and only the angle θ _f end surface and the angle θ plane of polarized components inclined by _p of the inclined optical fiber is inclined in the same direction with respect to a plane perpendicular to the optical axis,
The end face of the optical fiber and the polarizing component arranged on the end face side are arranged via an air layer, and the distance between the end face of the optical fiber and the surface of the polarizing component facing the end face of the optical fiber is the optical axis. Is less than 1 [mm] above,
A light beam shift amount by which the light beam is displaced from the optical axis between the end face of the optical fiber and the polarizing component disposed on the end face side is ΔT _f , and the light beam is displaced from the optical axis inside the optical isolator. Provided is an optical isolator module in which the absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm] when the beam shift amount is ΔT _i .

  With the optical isolator module having such a configuration, it is possible to easily adjust the optical axis when the optical isolator module is incorporated into the optical semiconductor module, and to further reduce the size of the optical semiconductor module after the optical axis adjustment. it can.

The present invention also provides an optical semiconductor module comprising a semiconductor chip, a condenser lens, and the above-described optical isolator module.
With the optical semiconductor module having such a configuration, the optical axis can be easily adjusted, the manufacturing efficiency can be improved, and the external shape of the optical semiconductor module can be reduced.

At this time, the semiconductor chip may have a semiconductor optical amplifier.
An optical semiconductor module having such a semiconductor optical amplifier can be used in a wide range of technical fields.

  As described above, according to the present invention, an optical isolator module with easy optical axis adjustment can be obtained. Moreover, a small optical semiconductor module can be obtained by incorporating the optical isolator module of the present invention.

It is a schematic diagram which shows the cross section of the structural example of the optical isolator module of this invention. It is a schematic diagram which shows the optical path in the optical isolator module of this invention. It is a schematic diagram which shows the cross section of a part of optical semiconductor module of this invention. It is a schematic diagram which shows the structural example of the optical semiconductor module of this invention. It is a schematic diagram which shows the cross section of the other structural example of the optical isolator module of this invention. It is a schematic diagram which shows the cross section of the structural example of the conventional optical isolator module.

Hereinafter, the present invention will be described in more detail.
As described above, in an optical isolator module and an optical semiconductor module incorporating the optical isolator module, there is a need for an optical isolator module that can easily adjust the optical axis when mounting the optical isolator module and can downsize the optical semiconductor module after mounting. .

As a result of intensive studies to achieve the above object, the present inventors have found that the optical isolator includes a Faraday rotator and a pair of polarizing components disposed on both sides of the Faraday rotator, and the optical isolator optically. An optical isolator module having an optical fiber disposed on an incident side or a light emitting side and having an end face inclined by an angle θ _f from a plane perpendicular to an optical axis of light propagation,
In the polarizing component disposed on the end face side of the optical fiber, a surface of the polarizing component facing the end face of the optical fiber is inclined by an angle θ _p from a plane perpendicular to the optical axis, and only the angle θ _f end surface and the angle θ plane of polarized components inclined by _p of the inclined optical fiber is inclined in the same direction with respect to a plane perpendicular to the optical axis,
The end face of the optical fiber and the polarizing component arranged on the end face side are arranged via an air layer, and the distance between the end face of the optical fiber and the surface of the polarizing component facing the end face of the optical fiber is the optical axis. Is less than 1 [mm] above,
A light beam shift amount by which the light beam is displaced from the optical axis between the end face of the optical fiber and the polarizing component disposed on the end face side is ΔT _f , and the light beam is displaced from the optical axis inside the optical isolator. An optical isolator module in which the absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm] when the beam shift amount is ΔT _i can solve the above problem. The headline and the present invention were completed.

  Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.

  As shown in FIG. 1, an optical isolator module 50 according to the present invention includes at least an optical isolator 11 and an optical fiber 17 having an inclined tip disposed on the light incident side of the optical isolator. Here, the optical isolator 11 includes a Faraday rotator 12, a pair of polarizing components 13 and 15 disposed at both ends of the Faraday rotator, and a magnet 16. The surface 14 of the optical fiber side polarizing component 13 facing the end face 18 of the optical fiber is inclined, and the inclination direction of the surface 14 is the same as the inclination direction of the end face 18 of the optical fiber.

Here, the inclination direction of the surface will be described below.
In the present invention, the tilt direction of the tilted surface of the polarizing component and the optical fiber includes a plane including the major axis of the tilted surface of the optical fiber (the major axis of the end surface that becomes an ellipse) and the extension line (optical axis) of the optical fiber central axis Considering the above, on this plane, the tilt direction from the plane perpendicular to the optical axis of the tilt surface of the polarizing component and the tilt direction from the plane perpendicular to the optical axis of the end face of the optical fiber may be the same. More specifically, the angle between the end face 18 of the optical fiber in FIG. 1 and the plane perpendicular to the optical axis on the plane is θ _f, and the clockwise direction with respect to the plane perpendicular to the optical axis is positive (plus ), The counterclockwise direction is expressed as negative (minus). Similarly, an angle formed by a surface 14 facing the end face of the optical fiber of the polarizing component 13 and a surface perpendicular to the optical axis is θ _p . The same inclination direction means that the signs of θ _f and θ _p are the same. In the configuration example of FIG. 1, both θ _f and θ _p are positive values (forward taper). On the other hand, in the configuration example of the conventional optical isolator module shown in FIG. 6, θ _{f ′} is a positive value, θ _{p ′} is a negative value, and the inclination directions are opposite (reverse taper). In the present invention, the values of the angles θ _f and θ _p need not be the same.

The material constituting the optical isolator is not particularly limited, but bismuth-substituted rare earth iron garnet or the like is preferably used for the Faraday rotator, and LiNbO ₃ , YVO ₄ , TiO ₂ or the like is preferably used for the polarizing component. The magnet is selected from ferrite magnets and rare earth magnets according to the configuration and the strength of the required magnetic field, but a neodymium magnet or samarium cobalt (SmCo) magnet having a high magnetic flux density is preferable from the viewpoint of miniaturization. Further, each member may be processed as necessary, and components other than those described above may be added to the optical isolator.

  The optical fiber to be used is not particularly limited, but a single mode fiber (SMF) having a numerical aperture (NA) of about 0.1 to 0.16 is preferable. Furthermore, although the optical isolator module of the present invention includes at least an optical fiber and an optical isolator, there is no limitation on adding other components.

In the present invention, the polarization component located on the light incident side of the optical fiber and the optical isolator is disposed via the air layer. At this time, in order to reduce the size of the optical isolator module, the thickness of the air layer is less than 1 [mm]. In this way, even if the spread angle of the light emitted from the optical fiber (NA = 0.1 to 0.16) is taken into consideration, the front projection area of the optical material such as a Faraday rotator or a polarizing component used in the optical isolator is used. Can be reduced to a small size of 1 [mm ² ] or less.
Here, the thickness of the air layer is the distance between the optical fiber and the polarizing component located on the light incident side of the optical isolator. In the present invention, the thickness on the optical axis (extension line of the optical fiber central axis). It represents the distance from the end face of the optical fiber to the face of the polarizing component facing the end face of the optical fiber. The front projection area of the optical material is an area when the optical material is viewed along the optical axis.

On the other hand, if the thickness of the air layer exceeds 1 [mm], the front projection area of the polarizing component also exceeds 1 [mm ² ], and the size of the polarizing component must be increased. In addition, the Faraday rotator must be enlarged in accordance with the increase in the size of the polarizing component, the entire optical isolator module is increased in size, and the size reduction specification cannot be satisfied.

FIG. 2 shows an optical path in the optical isolator module. The amount of light beam shift by which the light beam located on the optical axis is displaced from the optical axis between the optical fiber arranged on the light incident side and the polarizing component located on the light incident side is ΔT _f , and inside the optical isolator, Arrangement is made so that the absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm], where ΔT _i is the amount of light beam shift by which the light beam located on the optical axis is displaced from the optical axis. . More preferably the absolute value of (ΔT _i -ΔT _f) is less than 0.2 [mm], further the absolute value of preferably (ΔT _i -ΔT _f) is less than 0.1 [mm].
Here, the inside of the optical isolator means from the incident end face of the polarizing component located on the light incident side to the outgoing end face of the polarizing component located on the light exit side. The light beam shift amount in the present invention represents the shift amount when the light beam is projected onto a plane perpendicular to the optical axis (extension line of the optical fiber central axis). When radiated, it becomes a shift amount from the optical axis.

As described above, since the absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm], the distance that the light beam passing through the optical isolator module is separated from the optical axis can be suppressed small. A small optical material can be used, and the size of the entire optical isolator module can be reduced. And the size of the optical semiconductor module incorporating the optical isolator module can also be reduced. Further, since the light beam passes near the optical axis in the optical isolator module, the optical axis can be easily adjusted.
On the other hand, when the thickness of the air layer exceeds 1 [mm], the value of ΔT _f increases, and the absolute value of (ΔT _i −ΔT _f ) may be 0.5 [mm] or more. Also, when an optical isolator having a polarizing component with a large angle θp is used, the absolute value of (ΔT _i −ΔT _f ) may be 0.5 [mm] or more. When the absolute value of (ΔT _i −ΔT _f ) is 0.5 [mm] or more, the optical isolator module becomes large and optical axis adjustment becomes difficult.

The light that has passed through the optical isolator 11 is collected by a lens 19, for example, as shown in FIG.
In general, when an optical isolator module is mounted on an optical semiconductor module, the position of the semiconductor chip is fixed and the lens and the optical isolator module are displaced, or the position of the semiconductor chip and the lens is fixed and only the optical isolator module is displaced. However, if the optical isolator module is configured as described above, the amount of displacement of the lens and the optical isolator module can be suppressed, and the optical axis adjustment can be facilitated to manufacture the optical semiconductor module. Efficiency can be improved. Furthermore, since the displacement amount of the lens and the optical isolator module is small, the mounted optical semiconductor module can be reduced in size.

  Next, a case where the configuration of the optical isolator module according to the present invention is applied to the light emitting side will be described with reference to FIGS.

  FIG. 4 is a schematic diagram showing an example of the configuration of an optical semiconductor module 80 on which the optical isolator module of the present invention is mounted. Light propagates from right to left in FIG. The optical fiber 17 on the right side and the optical isolator 11 constitute the optical isolator module 50 on the light incident side already described. The light that has passed through the optical isolator 11 further reaches the semiconductor chip 20 through the lens 19, undergoes a predetermined process in the semiconductor chip 20, and is emitted. The light emitted from the semiconductor chip 20 further passes through the lens 19, passes through the optical isolator 31, and then enters the left optical fiber 37. The optical isolator 31 and the left optical fiber 37 constitute an optical isolator module 60 on the light output side as shown in FIG.

An example of the configuration of the optical isolator module 60 on the light emitting side is shown in FIG. To avoid duplication of description. Therefore, detailed description of the FIG. 5, an optical isolator module 60 of the light emitting side, the optical fiber 37 disposed on the light emission side with an end face 38 which is inclined at an angle theta _f and An optical isolator 31 is provided. The optical isolator 31 includes a Faraday rotator 32, a pair of polarizing components 33 and 35 disposed on both sides of the Faraday rotator, and a magnet 36.
In the optical fiber-side polarizing component 33, a surface 34 facing the end face of the optical fiber is inclined by an angle theta _p. Here, when the plane perpendicular to the optical axis is taken as a reference and the clockwise angle is positive (plus), θ _f and θ _{p in} FIG. 5 are both negative (minus) values, but the inclination direction is Are the same.

  The optical fiber arranged on the light emitting side and the polarizing component located on the light emitting side are arranged via the air layer, and the thickness of the air layer is 1 [mm] or less. In this way, the optical isolator module can be reduced in size.

Further, in the optical isolator, a light beam shift amount by which the light beam located on the optical axis is displaced from the optical axis is ΔT _i , and between the polarization component located on the light emitting side and the optical fiber arranged on the light emitting side. The absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm] where ΔT _f is the light beam shift amount by which the light beam positioned on the optical axis is displaced from the optical axis. . More preferably the absolute value of (ΔT _i -ΔT _f) is less than 0.2 [mm], further the absolute value of preferably (ΔT _i -ΔT _f) is less than 0.1 [mm].

  If the optical isolator module mounted on the light emitting side is configured as described above, the manufacturing efficiency of the optical semiconductor module can be improved in the same manner as the optical isolator module mounted on the light incident side. The size can be reduced.

  The semiconductor chip mounted on the optical semiconductor module of the present invention is not particularly limited, but is preferably a semiconductor chip having a semiconductor optical amplifier. Miniaturization is desired in an optical semiconductor module incorporating a semiconductor amplifier, and the present invention is particularly useful, and can be used in a wide range of technical fields.

表１から空気層の厚みを１［ｍｍ］以上とすると、ΔＴ_ｆが相対的に大きくなり、光軸調整が困難となることが判る。 EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(test)
The tip of an SMF with a wavelength of 1550 [nm] and a refractive index of 1.468 is tilted at 4, 6, 8 [°], and the thickness of the air layer to the polarizing component of the facing optical isolator is 0.2 to 3 [mm Table 1 shows the light beam shift amount [μm]. As the inclination angle θ _{f of the} end face of the optical fiber is larger and the thickness of the air layer is larger, the light beam shift amount ΔT _f is larger.

From Table 1, it can be seen that when the thickness of the air layer is 1 [mm] or more, ΔT _f becomes relatively large and the optical axis adjustment becomes difficult.

Next, an optical isolator was manufactured. As the Faraday rotator, a bismuth-substituted rare earth iron garnet having a thickness of 0.4 [mm] and a refractive index of 2.34 was used. The Faraday rotator was coated with a double-sided anti-reflective coating.
As the polarizing component, three kinds of materials of LiNbO ₃ , YVO ₄ , and TiO ₂ were used. The surface facing the LiNbO ₃ optical fiber is subjected to tilting of 7, 10, 13 [°], and the surface facing the YVO ₄ and TiO ₂ optical fiber is tilting of 3, 4, 5 [°]. Was given. Each polarizing component was provided with a double-sided non-reflective coating with a thickness of the central axis of 0.3 [mm].

Each processed polarizing component and the Faraday rotator were arranged so as to pass through an air layer of 0.1 [mm] or 0.005 [mm], and an SmCo magnet was arranged around the periphery. Each optical isolator was manufactured obtains a light beam shift amount [Delta] T _i inside the optical isolator, shown in Table 2.

(Example)
By combining each optical fiber described in Table 1 and each optical isolator described in Table 2, the inclined end surface of the optical fiber and the inclined direction of the inclined surface of the polarizing component facing the optical fiber are aligned in the same direction. An optical isolator module on the incident side was produced. Furthermore, each produced optical isolator module was mounted in the optical semiconductor module using the apparatus for incorporation. At this time, the optical axis was adjusted by fixing the position of the semiconductor chip and displacing the lens and the optical isolator module. The thickness of the air layer between the optical fiber end face and the polarizing component facing it is 0.5 [mm], θ _f is 8 [°], ΔT _f is 33 [μm], the polarizing component is LiNbO ₃ and θ _p is 10 [°], the thickness of the air layer between the polarizing component and the Faraday rotator is 0.1 [mm], ΔT _i is 138 [μm], and the absolute value of (ΔT _i −ΔT _f ) is 105 [μm]. The time required to adjust the optical axis when mounting an optical isolator module was 10 minutes.
Then, an optical semiconductor module having a configuration including an optical isolator module on the light incident side, an optical isolator module on the light output side, a semiconductor chip, and two lenses shown in FIG. 4 was produced. All of the optical isolator modules have the specifications described above. The size of the outer shape of the optical semiconductor module could be reduced to 30 [mm] × 20 [mm] × 70 [mm].

(Comparative example)
Using the same optical fiber and optical isolator as in the previous example, an optical isolator module was manufactured so that the inclined end surface of the optical fiber and the inclined direction of the inclined surface of the polarizing component facing it were opposite to each other. . Each of the produced optical isolator modules was mounted on an optical semiconductor module using an assembly apparatus. At this time, the optical axis was adjusted by fixing the position of the semiconductor chip and displacing the lens and the optical isolator module. The optical isolator module having the above specifications was used. The time required for adjusting the optical axis was 24 minutes.
Then, similarly to the example, an optical semiconductor module having a configuration including an optical isolator module on the light incident side, an optical isolator module on the light output side, a semiconductor chip, and two lenses was manufactured. The size of the outer shape of the optical semiconductor module was 34 [mm] × 24 [mm] × 70 [mm], which was larger than that of the example.

  From the results of Examples and Comparative Examples, it was found that the optical axis adjustment time when mounting the optical isolator module on the optical semiconductor module can be shortened by using the configuration of the optical isolator module according to the present invention. Furthermore, the optical semiconductor module incorporating the optical isolator module of the present invention can be reduced in size as compared with a module incorporating a conventional optical isolator module.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 11 ... Optical isolator, 12 ... Faraday rotator, 13 ... Optical fiber side polarizing component,
14 ... Face facing the end face of the optical fiber, 15 ... Polarizing component, 16 ... Magnet,
17 ... Optical fiber, 18 ... End face of optical fiber, 19 ... Lens,
20 ... Semiconductor chip, 31 ... Optical isolator, 32 ... Faraday rotator,
33: Optical fiber side polarizing component 34: Surface facing the end surface of the optical fiber,
35 ... Polarizing component, 36 ... Magnet, 37 ... Optical fiber, 38 ... End face of optical fiber,
50 ... Optical isolator module, 60 ... Optical isolator module,
80: optical semiconductor module, 110: optical isolator module,
111 ... Optical isolator, 112 ... Faraday rotator,
113 ... Optical fiber side polarization component, 114 ... Face facing the end face of the optical fiber,
115: Polarizing component, 116: Magnet, 117 ... Optical fiber,
118: An end face of the optical fiber.

Claims (3)

An optical isolator including a Faraday rotator and a pair of polarizing components disposed on both sides of the Faraday rotator, and a plane that is disposed on the light incident side or light output side of the optical isolator and is perpendicular to the optical axis of light propagation An optical isolator module having an optical fiber with an end face inclined by an angle θ _f ,
In the polarizing component disposed on the end face side of the optical fiber, a surface of the polarizing component facing the end face of the optical fiber is inclined by an angle θ _p from a plane perpendicular to the optical axis, and only the angle θ _f end surface and the angle θ plane of polarized components inclined by _p of the inclined optical fiber is inclined in the same direction with respect to a plane perpendicular to the optical axis,
The end face of the optical fiber and the polarizing component arranged on the end face side are arranged via an air layer, and the distance between the end face of the optical fiber and the surface of the polarizing component facing the end face of the optical fiber is the optical axis. Is less than 1 [mm] above,
A light beam shift amount by which the light beam is displaced from the optical axis between the end face of the optical fiber and the polarizing component disposed on the end face side is ΔT _f , and the light beam is displaced from the optical axis inside the optical isolator. An optical isolator module, wherein an absolute value of (ΔT _i −ΔT _f ) is less than 0.5 [mm] when a beam shift amount is ΔT _i .   An optical semiconductor module comprising a semiconductor chip, a condensing lens, and the optical isolator module according to claim 1. The optical semiconductor module according to claim 2, wherein the semiconductor chip has a semiconductor optical amplifier.

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