JP2005070710A - Optical attenuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable attenuation type optical attenuator that has the ability to obtain a target attenuation with a simple configuration, that needs no highly accurate driving mechanism, and that has high setting resolution for attenuation as well as small dependency on wavelength. <P>SOLUTION: The optical attenuator 10 is equipped with a first collimator lens 11 to which an incident optical fiber 21 is connected, a second collimator lens 12 which is connected with a outgoing optical fiber 22 and which is placed in a manner inclined to the first collimator lens 11, and a triangular prism 13 which is disposed between these first and second collimator lenses 11, 12. The triangular prism 13 moves back and forth in the Z direction on an optical path between the first and second collimator lenses 11, 12 by means of an actuator 30. With the triangular prism 13 transferred, a position for bending an optical beam is shifted, so that a light beam entering the second collimator lens 12 is deviated from the center of the lens and that a light beam entering the outgoing optical fiber 22 is made incident in an inclined manner. As a result, the coupling efficiency of the outgoing radiation optical fiber 22 is lowered, thereby increasing the optical attenuation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical attenuator used in an optical transmission device or the like, and more particularly to an optical attenuator that can be realized with a simple configuration.

  In the conventional optical transmission device, in order to operate the optical transmission device with a predetermined performance, it is necessary to keep the power of the input optical signal within a predetermined range. For the purpose of attenuating the power of the excessive optical signal, An optical component called an attenuator is used. In particular, optical amplifiers that optimize the amount of light and wavelength dependency in combination with optical fiber amplifiers, and chromatic dispersion compensators that adjust the gain of wavelength-separated light need to have the same amount of light for each wavelength channel. A variable optical attenuator capable of adjusting the attenuation is used.

  Conventionally, as this type of optical attenuator, an incident optical fiber and an outgoing optical fiber are arranged opposite to each other with their optical axes aligned, and a lens whose optical axis is aligned is disposed between both optical fibers. There is a technique for setting the optical attenuation by changing the fiber coupling efficiency by defocusing the light incident on the outgoing optical fiber depending on the position of the lens (see Patent Document 1). Further, this Patent Document 1 also describes that a light-attenuation amount is made variable by providing a drive mechanism for moving a lens and changing the defocus state of light incident on the outgoing optical fiber.

JP 2002-221675A (page 4-5, FIG. 1)

  However, in the technique described in Patent Document 1, the amount of light attenuation is adjusted using the focused light from the lens. Therefore, if the lens is decentered, the amount of light attenuation increases significantly, making it difficult to adjust the amount of light attenuation. turn into. Further, even if the optical axis of the lens is slightly inclined, the light attenuation amount is remarkably increased, and similarly, the adjustment of the light attenuation amount becomes difficult. Furthermore, when viewed as a variable optical attenuator, the amount of light attenuation changes significantly even if the lens is moved slightly by the drive mechanism, so it is necessary to use extremely high-precision parts as the drive mechanism. Has led to increased complexity and cost.

The present invention has been made to solve such a technical problem, and an object of the present invention is to provide an optical attenuator capable of obtaining a target optical attenuation with a simple configuration. is there.
Another object of the present invention is to provide a variable optical attenuation type optical attenuator that does not require a high-precision drive mechanism, has high optical attenuation setting resolution, and has low wavelength dependency.

  For this purpose, an optical attenuator to which the present invention is applied includes a first optical fiber that inputs a light beam and a first collimator that converts the light beam emitted from the first optical fiber into parallel light. A second collimating lens that collects the light beam emitted from the first collimating lens, a second optical fiber that outputs the light beam emitted from the second collimating lens, and the first collimating lens. It includes a prism that is disposed between the lens and the second collimating lens and whose light beam incident surface and light exit surface are not parallel to each other.

  Here, the first optical fiber and the first collimating lens constitute a first fiber collimator, and the second optical fiber and the second collimating lens constitute a second fiber collimator. It is preferable in that the configuration can be simplified. In addition, if the prism further includes a drive member that linearly moves on the optical path of the light beam emitted from the first collimating lens, a variable optical attenuator capable of adjusting the amount of light attenuation is configured. It is preferable in that it can be performed.

  From another viewpoint, the optical attenuator to which the present invention is applied is a first optical fiber that inputs a light beam and a first optical fiber that converts the light beam emitted from the first optical fiber into parallel light. One collimating lens, a second collimating lens that collects the light beam emitted from the first collimating lens, a second optical fiber that outputs the light beam emitted from the second collimating lens, The first collimating lens is disposed between the first collimating lens and the second collimating lens, and the first collimating lens side light beam entrance surface and the second collimating lens side light beam exit surface are not parallel to each other. The second prism is disposed between the first prism and the second collimator lens, and the light incident surface on the first prism side and the light exit surface on the second collimator lens side are not parallel. No pre And an arm.

  Here, the first optical fiber and the first collimating lens constitute a first fiber collimator, and the second optical fiber and the second collimating lens constitute a second fiber collimator, and the first fiber If the optical axis of the collimator and the optical axis of the second fiber collimator are set on the same axis, the configuration of the optical module becomes easy and the workability during connection is improved. preferable. The light attenuation amount may further include a drive member that linearly moves the first prism and / or the second prism on the optical path of the light beam emitted from the first collimating lens. This is preferable in that a variable optical attenuator capable of adjusting the above can be configured. If the exit surface of the first prism and the entrance surface of the second prism are arranged substantially parallel to each other, the first prism and the second prism can be arranged close to each other. It is preferable in terms of possible.

  Furthermore, from another viewpoint, the optical attenuator to which the present invention is applied is a first optical fiber that inputs a light beam and a first optical fiber that converts the light beam emitted from the first optical fiber into parallel light. One collimating lens, a transmissive member that tilts and transmits parallel light emitted from the first collimating lens while maintaining a parallel state, and a second collimating lens that condenses the light beam emitted from the transmissive member And a second optical fiber that outputs a light beam emitted from the second collimating lens.

  Here, if the transmissive member is composed of one or a plurality of prisms, it is preferable in that the configuration can be facilitated. In addition, it is preferable that an inclination position adjusting member that adjusts the inclination position of the parallel light by the transmission member is further provided in that a variable optical attenuator capable of adjusting the amount of light attenuation can be configured.

According to the optical attenuator of the present invention, the target optical attenuation can be obtained with a simple configuration.
In addition, according to the optical attenuator of the present invention, a high-precision drive mechanism is not required, the optical attenuation amount setting resolution is high, and the wavelength dependency can be reduced.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
—Embodiment 1—
FIG. 1 is a view showing an optical attenuator (VOA) 10 which is a kind of optical component module used in a wavelength division multiplexing optical communication device or the like. This optical attenuator 10 is connected to a first collimating lens 11 to which an incident optical fiber 21 as a first optical fiber is connected and an outgoing optical fiber 22 as a second optical fiber, and to the first collimator. A second collimating lens 12 which is disposed to be inclined with respect to the lens 11, and a triangular prism 13 as a transmission member disposed between the first collimating lens 11 and the second collimating lens 12. I have. In the present embodiment, the triangular prism 13 is moved in the Z direction (straight line) on the optical path between the first collimating lens 11 and the second collimating lens 12 by the actuator 30 as a driving member or an inclination position adjusting member. You can move forward and backward. The incident optical fiber 21 and the first collimating lens 11 are configured as an incident fiber collimator unit 23 (first fiber collimator) in which both are integrated. Similarly, the output optical fiber 22 and the second collimating lens 12 are also configured as an output fiber collimator unit 24 (second fiber collimator) in which both are integrated.

  Further, as the incident optical fiber 21 and the outgoing optical fiber 22, single mode optical fibers are used. Further, the first collimating lens 11 and the second collimating lens 12 have a focal length of 1.5 mm and a numerical aperture NA = 0.25 on the fiber side. Furthermore, as the triangular prism 13, the optical glass SF11 (n = 1.75) is used as the glass material, the light incident surface (opposite side to the first collimating lens 11) 13a and the emitting surface (second collimating lens). A right-angle prism having an angle of 15 ° with the side 13b) is used. Naturally, the entrance surface 13a and the exit surface 13b of the triangular prism 13 are non-parallel.

  The first collimating lens 11, the second collimating lens 12, the actuator 30 that drives the triangular prism 13, the incident optical fiber 21, and the outgoing optical fiber 22 are attached to a rectangular substrate 40. The substrate 40 includes a V groove 41 for fixing the incident optical fiber 21, a V groove 42 for fixing the outgoing optical fiber 22, a recess 43 for fixing the first collimating lens 11, and the second collimating lens 12. A recess 44 for fixing and a recess 45 for fixing the actuator 30 for driving the triangular prism 13 are provided. The first collimating lens 11, the second collimating lens 12, the actuator 30, the incident optical fiber 21, and the outgoing optical fiber 22 are fixed to the substrate 40 with a metal such as an ultraviolet curable adhesive or solder. . As the substrate 40, for example, hard materials such as ceramics, glass, and plastic can be used in addition to silicon.

  Next, the actuator 30 provided for moving the triangular prism 13 will be described. FIG. 2 is a side sectional view of the actuator 30, and FIG. 3A is an exploded view of the actuator 30. The actuator 30 has a cylindrical shape, in which the triangular prism 13 is housed, and a prism holding member 31 having a thread (not shown) cut on its outer peripheral surface, a cylindrical main body 32a, and the main body 32a. Electrodes 32b to 32e that are divided into four along the axial direction on the outer peripheral surface, the piezoelectric element 32 that can accommodate the prism holding member 31 inside, and one end side of the piezoelectric element 32 that has a ring shape And a ring 33 that is threaded into which the prism holding member 31 can be screwed, and a housing 34 that accommodates the prism holding member 31, the piezoelectric element 32, and the ring 33. Yes. In FIG. 3A, the description of the housing 34 is omitted.

  Here, the piezoelectric element 32 is bonded and fixed to the inner peripheral surface of the housing 34 with an adhesive 35. Further, ribs 36 and 37 are formed on the inner peripheral surface of the casing 34 with the piezoelectric element 32 and the ring 33 interposed therebetween, and the movement of the ring 33 in the axial direction of the prism holding member 31 is restricted. . Further, a shaft 38 is formed in the housing 34 along the axial direction, and the shaft 38 is inserted through a through hole 31 a provided in the prism holding member 31. Further, as shown in FIG. 3B, among the electrodes 32b to 32e formed on the outer peripheral surface of the piezoelectric element 32, the first AC power supply 39a is connected to the electrode 32b and the electrode 32d, and the electrode 32c and A second AC power supply 39b is connected to the electrode 32e and functions as an ultrasonic motor.

Next, the basic operation of the optical attenuator 10 according to the present embodiment will be described with reference to FIGS.
The light beam emitted from the incident optical fiber 21 is incident on the first collimating lens 11, converted into parallel light, and then emitted from the first collimating lens 11. Then, the light beam emitted from the first collimating lens 11 enters the triangular prism 13. At this time, the incident surface 13a of the triangular prism 13 is substantially perpendicular to the incident direction of the light beam, and the light beam emitted from the first collimating lens 11 hardly changes its direction according to Snell's law. 13 is incident. The light beam incident on the triangular prism 13 is emitted from the triangular prism 13. At this time, the exit surface 13b of the triangular prism 13 is inclined by 15 ° with respect to the entrance surface 13a, and the light beam emitted from the exit surface 13b is directed in a predetermined angle while maintaining a parallel state according to Snell's law. Instead, the light is emitted from the triangular prism 13. Further, the light beam emitted from the triangular prism 13 enters the second collimating lens 12, is converted into focused light, and is emitted from the second collimating lens 12. Then, the light beam emitted from the second collimating lens 12 enters the outgoing optical fiber 22 in a condensed state, and is transmitted through the outgoing optical fiber 22. The light beam transmitted through the outgoing optical fiber 22 is combined with light beams of other wavelengths in, for example, a multiplexer (not shown).

In the optical attenuator 10, the position of the triangular prism 13 is adjusted using the actuator 30, so that the intensity of the light beam output through the outgoing optical fiber 22 can be attenuated.
First, the movement operation of the triangular prism 13 by the actuator 30 will be described. When an alternating current is applied to the electrodes 32b to 32e of the piezoelectric element 32 using the alternating current power supplies 39a and 39b, a traveling wave is generated on the bottom surface of the piezoelectric element 32. At this time, torque in the direction of arrow A shown in FIG. 3C acts on the ring 33, and the ring 33 starts to rotate in the direction of arrow A. Then, since the screw cut on the outer peripheral surface of the prism holding member 31 is screwed into the screw cut inside the ring 33, the prism holding member 31 also tries to rotate as the ring 33 rotates. Here, since the shaft 38 provided in the housing 34 fixed as shown in FIG. 2 passes through the through hole 31a formed in the prism holding member 31, the prism holding member 31 rotates. It cannot move, but moves in the direction of arrow B shown in FIG. That is, when an alternating current is passed through the piezoelectric element 32, the ring 33 rotates and the prism holding member 31 moves linearly. As a result, the triangular prism 13 attached to the prism holding member 31 moves in the Z direction shown in FIG. 1 and can move away from or approach the first collimating lens 11. At that time, since the prism holding member 31 does not rotate, the triangular prism 13 also does not rotate.

  FIG. 4 is a graph showing the relationship between the amount of movement of the triangular prism 13 in the Z direction and the attenuation amount (light attenuation amount) of the light beam output via the outgoing optical fiber 22. In the present embodiment, the state shown in FIG. 1, that is, the position where the triangular prism 13 is closest to the first collimating lens 11 is Z = 0, and the light attenuation is minimized when Z = 0. Each part is arranged in For this reason, the farther the triangular prism 13 is from the first collimating lens 11 (the closer it is to the second collimating lens 12), the greater the amount of light attenuation.

  The reason is as follows. When the triangular prism 13 is moved in the Z direction, the position where the light beam is inclined (position where the light beam is bent) is shifted. As a result, the light beam incident on the second collimating lens 12 is shifted from the center of the lens, and the light beam incident on the output optical fiber 22 is incident on the output optical fiber 22 with an inclination. As a result, the coupling efficiency of the outgoing optical fiber 22 decreases and the light attenuation increases. In the optical attenuator 10 according to the present embodiment, an optical attenuation amount of 30 dB or more can be obtained by moving the triangular prism 13 in the direction of about 2 mmZ. Here, FIG. 9 shows the relationship between the amount of movement of the lens in the optical attenuator described in Patent Document 1 described above and the attenuation amount (light attenuation amount) of the light beam output through the optical fiber. In the optical attenuator 10 according to the present embodiment, unlike the optical attenuator of Patent Document 1 shown in FIG. 9, the optical attenuation does not become 15 dB just by moving the lens by about 10 μm. Since the positioning accuracy of the triangular prism 13 is not so required, there is an advantage that a desired light attenuation amount can be obtained while using the actuator 30 having a low accuracy. Further, in the present embodiment, since the phase difference of light is not used unlike the optical waveguide, the wavelength dependency of light can be reduced.

  In the present embodiment, the angle formed by the incident surface 13a and the exit surface 13b of the triangular prism 13 is 15 °. The reason for selecting this angle is as follows. FIG. 5 is a graph showing the relationship between the angle at which the optical axis of the light beam transmitted through the triangular prism 13 is bent and the insertion loss caused by inserting the triangular prism 13. From the figure, it can be seen that in order to suppress the insertion loss to 0.1 dB or less, the angle of bending of the optical axis must be suppressed to 20 ° or less. The angle at which the optical axis is bent follows Snell's law as described above. Therefore, in the present embodiment, SF 11 having a refractive index n = 1.75 is selected as the glass material constituting the triangular prism 13, and the angle formed by the incident surface 13a and the outgoing surface 13b of the triangular prism 13 is 15 °. Thus, the angle of bending of the optical axis is set to 20 ° or less.

  In the present embodiment, the triangular prism 13 is used. However, for example, a trapezoidal prism may be used when the angle formed by the entrance surface and the exit surface is small. In the present embodiment, the first collimating lens 11, the second collimating lens 12, the actuator 30 to which the triangular prism 13 is attached, the incident optical fiber 21, the outgoing optical fiber 22, etc. are fixed on the substrate 40. However, the present invention is not limited to this, and it is also possible to employ a configuration in which an optical fiber collimator in which a collimator lens and an optical fiber are integrated is directly joined to the casing 34 of the actuator 30. . Further, in the present embodiment, an ultrasonic motor is used as the actuator 30, but the present invention is not limited to this, and for example, an electrostatic force drive type or an electromagnetic force variable type may be used. Furthermore, in the present embodiment, the variable optical attenuator is configured by moving the triangular prism 13 using the actuator 30. For example, the triangular prism 13 is fixed at a predetermined position by bonding or the like. Thus, an optical attenuator that obtains a certain amount of attenuation can also be configured.

-Embodiment 2-
The present embodiment is substantially the same as the first embodiment, but by using two triangular prisms, the incident optical fiber (incident fiber collimator unit) and the outgoing optical fiber (outgoing fiber collimator unit) are substantially straight. It can be arranged on the same axis. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6 is a diagram showing the optical attenuator 10 in the present embodiment. This optical attenuator 10 includes a first collimating lens 51 to which an incident optical fiber 61 as a first optical fiber is connected, and a second collimating lens to which an outgoing optical fiber 62 as a second optical fiber is connected. 52, and a first triangular prism 53 (first prism) and a second triangular prism as transmission members disposed to face each other between the first collimating lens 51 and the second collimating lens 52. 54 (second prism). In the present embodiment, the first triangular prism 53 is disposed on the first collimating lens 51 side, and the second triangular prism 54 is disposed on the second collimating lens 52 side. The first triangular prism 53 is moved back and forth in the Z direction (straight line) on the optical path between the first collimating lens 51 and the second triangular prism 54 by an actuator 70 as a driving member or an inclination position adjusting member. On the other hand, the second triangular prism 54 is fixedly arranged. As in the first embodiment, the incident optical fiber 61 and the first collimating lens 51 are configured as an incident fiber collimator unit 63 (first fiber collimator) in which both are integrated. Similarly, the output optical fiber 62 and the second collimator lens 52 are also configured as an output fiber collimator unit 64 (second fiber collimator) in which both are integrated.

  As the incident optical fiber 61 and the outgoing optical fiber 62, single-mode optical fibers are used as in the first embodiment. Furthermore, the first collimating lens 51 and the second collimating lens 52 have a focal length of 1.5 mm and a numerical aperture NA = 0.25 on the fiber side. Furthermore, as the first triangular prism 53, an optical glass SF11 (n = 1.75) is used as a glass material, a light incident surface (opposite side to the first collimating lens 51) 53a and an emission surface (second). A right-angle prism having an angle of 15 ° with the triangular prism 54) is used. In addition, as the second triangular prism 54, optical glass SF11 (n = 1.75) is used as a glass material, a light incident surface (opposite side to the first triangular prism 53) 54a and an emission surface (second surface). A right angle prism having an angle of 15 ° with the collimating lens 52 (on the side facing the collimating lens 52) is used. That is, the first triangular prism 53 and the second triangular prism 54 are the same. Naturally, the entrance surface 53a and the exit surface 53b of the first triangular prism 53 are non-parallel, and the entrance surface 54a and the exit surface 54b of the second triangular prism 54 are non-parallel. However, in the present embodiment, the emission surface 53b of the first triangular prism 53 and the incident surface 54a of the second triangular prism 54 are arranged so as to be substantially parallel.

  The first collimating lens 51, the second collimating lens 52, the actuator 70 that drives the first triangular prism 53, the second triangular prism 54, the incident optical fiber 61, and the outgoing optical fiber 62 are rectangular. The substrate 80 is attached. The substrate 80 includes a V groove 81 for fixing the incident optical fiber 61, a V groove 82 for fixing the outgoing optical fiber 62, a recess 83 for fixing the first collimating lens 51, and a second collimating lens 52. A concave portion 84 for fixing, an actuator 70 for driving the first triangular prism 53 and a concave portion 85 for fixing the second triangular prism 54 are provided. The first collimating lens 51, the second collimating lens 52, the actuator 70, the second triangular prism 54, the incident optical fiber 61, and the outgoing optical fiber 62 are made of an ultraviolet curable adhesive or a metal such as solder. It is fixed to the substrate 80. The actuator 70 is the same as the actuator 30 described in the first embodiment.

Next, the basic operation of the optical attenuator 10 according to this embodiment will be described.
The light beam emitted from the incident optical fiber 61 is incident on the first collimating lens 51, converted into parallel light, and then emitted from the first collimating lens 51. Then, the light beam emitted from the first collimating lens 51 enters the first triangular prism 53. At this time, the incident surface 53a of the first triangular prism 53 is substantially perpendicular to the incident direction of the light beam, and the light beam emitted from the first collimating lens 51 changes its direction almost in accordance with Snell's law. Without being incident on the first triangular prism 53. The light beam incident on the first triangular prism 53 is emitted from the first triangular prism 53. At this time, the emission surface 53b of the first triangular prism 53 is inclined by 15 ° with respect to the incidence surface 53a, and the light beam emitted from the emission surface 53b is maintained at a predetermined angle while maintaining a parallel state according to Snell's law. The light is emitted from the first triangular prism 53 while changing the direction only. Further, the light beam emitted from the first triangular prism 53 enters the second triangular prism 54. At this time, the light beam emitted from the emission surface 53b of the first triangular prism 53 is incident on the second triangular prism 54 while changing its direction by a predetermined angle while maintaining a parallel state according to Snell's law. The light beam incident on the second triangular prism 54 is emitted from the second triangular prism 54. Further, the light beam emitted from the second triangular prism 54 enters the second collimating lens 52, is converted into focused light, and is emitted from the second collimating lens 52. Then, the light beam emitted from the second collimating lens 52 enters the outgoing optical fiber 62 in a condensed state, and is transmitted through the outgoing optical fiber 62. The light beam transmitted through the outgoing optical fiber 62 is combined with light beams of other wavelengths in, for example, a multiplexer (not shown).

In the optical attenuator 10, as in the first embodiment, the position of the first triangular prism 53 is adjusted by using the actuator 70, so that the intensity of the light beam output through the outgoing optical fiber 62 is increased. It can be attenuated.
FIG. 7 is a graph showing the relationship between the amount of movement of the first triangular prism 53 in the Z direction and the attenuation of the light beam output through the outgoing optical fiber 62 (light attenuation). In the present embodiment, unlike the first embodiment, the first triangular prism 53 is brought into contact with the second triangular prism 54 (the output surface 53b of the first triangular prism 53 and the second triangular prism 53 are in contact with each other). The position where the incident surface 54a of the triangular prism 54 is in contact is Z = 0, and each component is arranged so that the light attenuation amount is minimized when Z = 0. For this reason, the light attenuation amount increases as the first triangular prism 53 is moved away from the second triangular prism 54 (closer to the first collimating lens 51).

The reason is as follows. When the first triangular prism 53 is moved in the Z direction, the position where the light beam tilts (the position where the light beam is bent) is shifted, and the light beam emitted from the first triangular prism 53 enters the second triangular prism 54. The position to do is also shifted. Then, the light beam incident on the second collimating lens 52 is shifted from the center of the lens, and the light beam incident on the outgoing optical fiber 62 is incident on the outgoing optical fiber 62 with an inclination. As a result, the coupling efficiency of the outgoing optical fiber 62 decreases, and the light attenuation increases. In the optical attenuator 10 according to the present embodiment, an optical attenuation amount of 30 dB or more can be obtained by moving the first triangular prism 53 in the direction of about 0.45 mmZ.
In this embodiment, the first triangular prism 53 and the second triangular prism 54 are used, and the light beam tilted by the first triangular prism 53 is tilted in the opposite direction by the second triangular prism 54. As a result, since the incident optical fiber 61 (incident fiber collimator unit 63) and the outgoing optical fiber 62 (outgoing fiber collimator unit 64) can be arranged on the same axis, workability when connecting to other optical components or the like is possible. Will be better.

  FIG. 8 shows the first triangle when the optical glass BK7 (n = 1.51) is used instead of the optical glass SF11 as the glass material constituting the first triangular prism 53 and the second triangular prism 54. 6 is a graph showing the relationship between the amount of movement of the prism 53 in the Z direction and the attenuation amount (light attenuation amount) of the light beam output through the outgoing optical fiber 62. FIG. The shapes of the first triangular prism 53 and the second triangular prism 54 are the same as those described above. As described above, when the refractive index of the glass material constituting the first triangular prism 53 and the second triangular prism 54 is lowered, the first triangular prism 53 may be moved by about 1 mm in order to obtain an attenuation of 30 dB or more. I understand that. That is, the desired characteristics can be easily obtained by appropriately selecting the angle formed by the glass material (refractive index) constituting the prism and the entrance surface and the exit surface as necessary.

  In the present embodiment, only the first triangular prism 53 is moved. However, the present invention is not limited to this, and only the second triangular prism 54 may be configured to be movable. Of course, both the first triangular prism 53 and the second triangular prism 54 may be configured to be movable. In this embodiment, two triangular prisms (first triangular prism 53 and second triangular prism 54) are used. However, three or more prisms may be used. Furthermore, in the present embodiment, the variable optical attenuator is configured by moving the first triangular prism 53 using the actuator 70. For example, the first triangular prism 54 is similar to the first triangular prism 54. By fixing the triangular prism 53 by bonding or the like, an optical attenuator that obtains a certain amount of attenuation can also be configured.

1 is a diagram illustrating an optical attenuator according to Embodiment 1. FIG. It is side part sectional drawing of an actuator. (a) is an exploded view of the actuator, (b) is an electrical system diagram of the actuator, and (c) is a diagram for explaining the operation of the actuator. It is a graph which shows the relationship between the moving amount | distance to the Z direction of a triangular prism, and the attenuation amount of the output light beam. It is a graph which shows the relationship between the angle which the optical axis of the light beam which permeate | transmits a triangular prism bends, and the insertion loss which arises. 6 is a diagram illustrating an optical attenuator according to Embodiment 2. FIG. It is a graph which shows the relationship between the moving amount | distance to the Z direction of a 1st triangular prism, and the attenuation amount of the output light beam. It is a graph which shows the relationship between the moving amount | distance to the Z direction of the 1st triangular prism, and the attenuation amount of the output light beam at the time of making the constituent material of a 1st, 2nd triangular prism different. It is a graph which shows the relationship between the movement amount of the lens in the conventional optical attenuator, and the attenuation amount of the output light beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical attenuator, 11 ... 1st collimating lens, 12 ... 2nd collimating lens, 13 ... Triangular prism, 13a ... Incident surface, 13b ... Outgoing surface, 21 ... Incident optical fiber, 22 ... Outgoing optical fiber, 23 DESCRIPTION OF SYMBOLS ... Incident fiber collimator unit, 24 ... Outgoing fiber collimator unit, 30 ... Actuator, 31 ... Prism holding member, 31a ... Through hole, 32 ... Piezoelectric element, 32a ... Main body, 32b-32e ... Electrode, 33 ... Ring, 34 ... Housing Body 35 ... Adhesive 36,37 ... Rib 38 ... Shaft 39a, 39b ... AC power source 40 ... Substrate 51 ... First collimating lens 52 ... Second collimating lens 53 ... First triangle Prism, 54 ... second triangular prism, 61 ... incident optical fiber, 62 ... outgoing optical fiber, 63 ... incident fiber collimator unit, 4 ... emission fiber collimator unit, 70 ... actuator, 80 ... substrate

Claims (10)

A first optical fiber for inputting a light beam;
A first collimating lens that converts a light beam emitted from the first optical fiber into parallel light;
A second collimating lens that collects the light beam emitted from the first collimating lens;
A second optical fiber that outputs a light beam emitted from the second collimating lens;
An optical attenuator including a prism disposed between the first collimating lens and the second collimating lens and having a light beam incident surface and a light output surface which are not parallel to each other. The first optical fiber and the first collimating lens constitute a first fiber collimator;
2. The optical attenuator according to claim 1, wherein the second optical fiber and the second collimating lens constitute a second fiber collimator.   2. The optical attenuator according to claim 1, further comprising a drive member that linearly moves the prism on an optical path of a light beam emitted from the first collimating lens. A first optical fiber for inputting a light beam;
A first collimating lens that converts a light beam emitted from the first optical fiber into parallel light;
A second collimating lens that collects the light beam emitted from the first collimating lens;
A second optical fiber that outputs a light beam emitted from the second collimating lens;
Between the first collimating lens and the second collimating lens, an incident surface of the light beam on the first collimating lens side and an exit surface of the light beam on the second collimating lens side A first prism that is not parallel;
The first prism and the second collimator lens are disposed between the first prism side and the light beam incident surface on the first prism side and the light exit surface on the second collimator lens side are not parallel. An optical attenuator including a second prism. The first optical fiber and the first collimating lens constitute a first fiber collimator;
The second optical fiber and the second collimating lens constitute a second fiber collimator,
The optical attenuator according to claim 4, wherein an optical axis of the first fiber collimator and an optical axis of the second fiber collimator are set on the same axis.   5. The driving member for linearly moving the first prism and / or the second prism on an optical path of a light beam emitted from the first collimating lens. Light attenuator.   5. The optical attenuator according to claim 4, wherein the exit surface of the first prism and the entrance surface of the second prism are arranged substantially parallel to each other. A first optical fiber for inputting a light beam;
A first collimating lens that converts a light beam emitted from the first optical fiber into parallel light;
A transmission member that transmits the parallel light emitted from the first collimating lens while tilting it while maintaining a parallel state;
A second collimating lens that collects the light beam emitted from the transmission member;
And an optical attenuator including a second optical fiber that outputs a light beam emitted from the second collimating lens.   The optical attenuator according to claim 8, wherein the transmission member includes one or a plurality of prisms.   The optical attenuator according to claim 8, further comprising an inclination position adjusting member that adjusts an inclination position of the parallel light by the transmission member.

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