JP2005024728A - Optical variable attenuator and optical variable attenuator module - Google Patents

Abstract

An optical variable attenuator and an optical variable attenuator module capable of monitoring the light quantity of an optical signal after attenuation without increasing optical loss.
An optical variable attenuator has a planar waveguide. The planar waveguide has an input optical waveguide core for inputting an optical signal and an output optical waveguide core for outputting an optical signal. And a monitoring optical waveguide core 5 for monitoring the light quantity of the optical signal. The planar waveguide 2 is provided with groove portions 6 connected to the optical waveguide cores 3 to 5. The input optical waveguide core 3 and the output optical waveguide core 4 are opposed to each other with the groove 6 interposed therebetween. The input optical waveguide core 3 and the monitor optical waveguide core 5 are formed on the same side with respect to the groove 6. A movable mirror 10 that reflects light from the input optical waveguide core 3 toward the monitor optical waveguide core 5 is disposed in the groove 6. The movable mirror 10 is movable in a direction crossing the input optical waveguide core 3.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical variable attenuator and an optical variable attenuator module used in optical communication and the like.
[0002]
[Prior art]
As a conventional optical variable attenuator, there is an optical variable attenuator in which two optical fibers are opposed to each other and a shutter is inserted and removed between them to control light transmission intensity (for example, see Non-Patent Document 1).
[0003]
[Non-Patent Document 1]
IEICE Technical Report PS2001-31
[0004]
[Problems to be solved by the invention]
In the above prior art, in order to monitor the light intensity (light quantity) after attenuation control, for example, it is necessary to connect an optical directional coupler or the like to the output side of the optical variable attenuator and extract a part of the optical signal. . However, if a part of the optical signal is branched in such a manner, an optical loss occurs at that part, so that the optical loss of the entire module increases.
[0005]
The objective of this invention is providing the optical variable attenuator and optical variable attenuator module which can monitor the light quantity of the optical signal after attenuation | damping, without increasing an optical loss.
[0006]
[Means for Solving the Problems]
An optical variable attenuator of the present invention is provided so as to face an input optical waveguide for inputting an optical signal, an output optical waveguide for outputting an optical signal, and the same side as the input optical waveguide Is disposed between the input optical waveguide and the output optical waveguide, and directs the light from the input optical waveguide toward the monitor optical waveguide. It comprises a movable mirror to be reflected and a driving means for moving the movable mirror in a direction crossing the input optical waveguide.
[0007]
In such an optical variable attenuator, the optical signal is attenuated by adjusting the amount of optical signal from the input optical waveguide to the output optical waveguide by moving the movable mirror in the direction crossing the input optical waveguide. Control the amount. At this time, light transmitted from the input optical waveguide without being reflected by the movable mirror is incident on the output optical waveguide, and the remaining light is reflected by the movable mirror and incident on the monitor optical waveguide. The Therefore, by measuring the amount of reflected light incident on the monitoring optical waveguide, it is possible to confirm the amount of light signal after attenuation. In this case, since a part of the attenuated optical signal is not branched, an increase in optical loss can be suppressed.
[0008]
The optical variable attenuator of the present invention is provided on the same side as the input optical waveguide for inputting the optical signal, the output optical waveguide for outputting the optical signal, and opposed to the input optical waveguide. And is disposed between the input optical waveguide and the monitor optical waveguide, and the light from the input optical waveguide is output to the output optical waveguide. And a driving means for moving the movable mirror in a direction crossing the input optical waveguide.
[0009]
In such an optical variable attenuator, the optical signal is attenuated by adjusting the amount of optical signal from the input optical waveguide to the output optical waveguide by moving the movable mirror in the direction crossing the input optical waveguide. Control the amount. At this time, of the optical signal from the input optical waveguide, the light reflected by the movable mirror is incident on the output optical waveguide, and the remaining light is transmitted without being reflected by the movable mirror and incident on the monitor optical waveguide. The Therefore, by measuring the amount of transmitted light incident on the monitoring optical waveguide, it is possible to confirm the amount of light signal after attenuation. In this case, since a part of the attenuated optical signal is not branched, an increase in optical loss can be suppressed.
[0010]
Preferably, the input optical waveguide, the output optical waveguide, and the monitor optical waveguide are formed of a planar waveguide, and the planar waveguide is connected to the input optical waveguide, the output optical waveguide, and the monitor optical waveguide, and is movable mirror. The groove part which arrange | positions is provided. By using a planar waveguide in this way, the optical variable attenuator can be miniaturized and highly integrated.
[0011]
The optical variable attenuator module of the present invention is characterized by including the above-described optical variable attenuator. By providing the optical variable attenuator having the monitoring optical waveguide as described above, the light amount of the attenuated optical signal can be monitored without increasing the optical loss as described above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of an optical variable attenuator and an optical variable attenuator module according to the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 is a plan view showing an embodiment of an optical variable attenuator according to the present invention. In the figure, an optical variable attenuator 1 of this embodiment has a planar waveguide 2 made of quartz glass or the like.
[0014]
The planar waveguide 2 includes an input optical waveguide core 3 for inputting an optical signal, an output optical waveguide core 4 for outputting an optical signal, and a monitoring optical waveguide core 5 for monitoring the light quantity of the optical signal. Is provided. The planar waveguide 2 is provided with a groove portion 6 that is connected to the input optical waveguide core 3, the output optical waveguide 4, and the monitor optical waveguide core 5 and extends in the width direction of the planar waveguide 2. The input optical waveguide core 3 and the output optical waveguide core 4 are formed so as to face each other with the groove 6 interposed therebetween. The input optical waveguide core 3 and the monitor optical waveguide core 5 are formed in a V shape on the same side with respect to the groove 6.
[0015]
On the planar waveguide 2, an actuator structure 7 formed using a micro electro mechanical system (MEMS) technique is provided. The actuator structure 7 has a cantilever beam 8 that is cantilevered on the upper surface of the planar waveguide 2, and the cantilever beam 8 has a groove 6 in a direction perpendicular to the width direction of the planar waveguide 2. Extends to position. A plurality of comb teeth 9 are provided at the tip side portion of the cantilever 8. The cantilever beam 8 is made of conductive Si or the like.
[0016]
A movable mirror 10 that reflects light from the input optical waveguide core 3 toward the monitoring optical waveguide core 5 is fixed to the tip of the cantilever 8. The movable mirror 10 has a knife edge shape, for example, and is configured to enter the groove 6 of the planar waveguide 2. The surface of the movable mirror 10 is coated with Au or the like. Thereby, since the reflectance becomes high with respect to light in the wavelength band for optical communication such as infrared light, insertion loss can be reduced.
[0017]
The actuator structure 7 has an electrode 11 provided on the upper surface of the planar waveguide 2. The electrode 11 extends parallel to the cantilever 8. A plurality of comb teeth 12 are provided on the electrode 11 so as to be disposed between the comb teeth 9 of the cantilever 8. The electrode 11 is also made of conductive Si or the like, similar to the cantilever 8.
[0018]
The cantilever 8 and the electrode 11 are connected via a voltage source 13. Then, a voltage is applied between the cantilever 8 and the electrode 11 by the voltage source 13 to generate an electrostatic force therebetween, and the movable mirror 10 is moved in a direction crossing the input optical waveguide core 3. (See FIG. 2). By driving the movable mirror 10 using the electrostatic force in this way, it is not necessary to pass a current, so that power saving can be achieved.
[0019]
In addition, since the cantilever 8 is provided with a plurality of comb teeth 9 and the electrode 11 is provided with a plurality of comb teeth 12, the surface area of the cantilever 8 and the electrode 11 is increased overall. . Accordingly, the electrostatic force generated between the cantilever 8 and the electrode 11 is increased accordingly, so that the voltage value applied between the cantilever 8 and the electrode 11 can be lowered.
[0020]
In the optical variable attenuator 1 as described above, transmitted light that is not reflected by the movable mirror 10 is used as signal light, and reflected light from the movable mirror 10 is used as monitor light. Then, the amount of transmitted light is varied by changing the voltage value applied between the cantilever 8 and the electrode 11, that is, the amount of movement of the movable mirror 10, thereby controlling the amount of light attenuation.
[0021]
Specifically, when the applied voltage is zero, the cantilever beam 8 extends straight as shown in FIG. In this state, most of the light emitted from the input optical waveguide core 3 is transmitted through the groove 6 without being reflected by the movable mirror 10 and is incident on the output optical waveguide core 4. An attenuation amount is obtained.
[0022]
When the applied voltage is increased from such an initial state, the tip side portion of the cantilever 8 is attracted to the electrode 11 by the electrostatic force generated between the cantilever 8 and the electrode 11 as shown in FIG. As a result, the movable mirror 10 moves toward the electrode 11 side. In this state, of the light emitted from the input optical waveguide core 3, more light is reflected by the movable mirror 10 and incident on the monitor optical waveguide core 5, and the light is transmitted through the groove 6 and output light. Since the amount of light incident on the waveguide core 4 decreases, the amount of light attenuation increases.
[0023]
FIG. 3 is a configuration diagram illustrating an example of an optical variable attenuator module including the optical variable attenuator 1 described above. In the figure, an optical variable attenuator module 20 includes the optical variable attenuator 1, an optical directional coupler 21, and light receivers 22 and 23.
[0024]
The optical directional coupler 21 is an optical component that is connected to the input optical waveguide core 3 of the optical variable attenuator 1 and branches a part of the optical signal input to the optical variable attenuator 1. The optical directional coupler 21 transmits, for example, 95% of the optical signal and sends it to the optical variable attenuator 1, and reflects and branches the remaining 5% of the light.
[0025]
The light receiver 22 receives the light branched by the optical directional coupler 21. The light receiver 23 is connected to the monitoring optical waveguide core 5 of the optical variable attenuator 1 and receives light passing through the monitoring optical waveguide core 5. The light receivers 22 and 23 are, for example, photodiodes (PD).
[0026]
In such a variable optical attenuator module 20, the incident light to the movable mirror 10 of the variable optical attenuator 1 is reflected by the movable mirror 10 without passing through the groove 6 and is reflected on the monitoring optical waveguide core 5. The intensity (light quantity) of the incident light is monitored by the light receiver 23. Therefore, by calculating the monitoring result and the monitoring result by the light receiver 22 together, the amount of transmitted light in the groove 6 can be estimated, and the attenuation target amount of the optical variable attenuator 1 can be obtained.
[0027]
Here, as a comparative example, one of conventional optical variable attenuator modules having an input monitor function and an output monitor function is shown in FIG.
[0028]
In the figure, an optical variable attenuator module 100 has an optical variable attenuator 101. The optical variable attenuator 101 has optical directional coupling for branching a part of an optical signal input to the optical variable attenuator 101. An optical directional coupler 103 that branches a part of the attenuated optical signal output from the optical variable attenuator 101 is connected. The lights branched by the optical directional couplers 102 and 103 are received by the light receivers 104 and 105, respectively.
[0029]
In such an optical variable attenuator module 100, since the optical directional couplers 102 and 103 are connected to two locations upstream and downstream of the optical variable attenuator 101, the loss in each optical directional coupler 102 and 103 is lost. As a result, the optical loss of the entire module increases. In addition, the number of parts of the module increases and the module increases in size.
[0030]
On the other hand, in the optical variable attenuator module 20 of this embodiment, the amount of light incident on the monitoring optical waveguide core 5 of the optical variable attenuator 1 is monitored. It is possible to check the amount of light of the optical signal after the attenuation control by the optical variable attenuator 1 without connecting an optical device and branching a part of the optical signal. In this case, since the optical signal after attenuation control is not affected, the optical loss of the entire module can be reduced. Further, since only one optical directional coupler is used, the module can be miniaturized.
[0031]
FIG. 5 is a plan view showing another embodiment of the optical variable attenuator according to the present invention. In the drawing, the same reference numerals are given to the same or equivalent members as those of the above-described embodiment, and the description thereof is omitted.
[0032]
In the figure, the optical variable attenuator 30 of the present embodiment has a planar waveguide 31. The planar waveguide 31 has an input optical waveguide core 32 for inputting an optical signal and an output for outputting an optical signal. An optical waveguide core 33 and a monitoring optical waveguide core 34 for monitoring the light quantity of the optical signal are provided. The planar waveguide 31 is provided with a groove 35 that is connected to the input optical waveguide core 32, the output optical waveguide 33, and the monitor optical waveguide core 34 and extends in the width direction of the planar waveguide 31. The input optical waveguide core 32 and the output optical waveguide core 33 are formed in a V shape on the same side with respect to the groove portion 35. The input optical waveguide core 32 and the monitor optical waveguide core 34 are formed so as to face each other with the groove 35 interposed therebetween. The optical variable attenuator 30 has the same actuator structure 7 as in the above-described embodiment.
[0033]
In such an optical variable attenuator 30, unlike the above-described embodiment, the reflected light from the movable mirror 10 is used as signal light, and the transmitted light that is not reflected by the movable mirror 10 is used as monitor light. Then, the amount of reflected light at the movable mirror 10 is varied by changing the voltage value applied between the cantilever 8 and the electrode 11, that is, the amount of movement of the movable mirror 10, thereby controlling the amount of light attenuation.
[0034]
Specifically, when the applied voltage is zero, the cantilever beam 8 extends straight as shown in FIG. In this state, most of the light emitted from the input optical waveguide core 32 is reflected by the movable mirror 10 and is incident on the output optical waveguide core 33, so that the minimum optical attenuation is obtained. .
[0035]
When the applied voltage is increased from such an initial state, the tip side portion of the cantilever 8 is attracted to the electrode 11 by the electrostatic force generated between the cantilever 8 and the electrode 11 and is bent accordingly. The movable mirror 10 moves to the electrode 11 side. In this state, of the light emitted from the input optical waveguide core 32, the light that is transmitted through the groove 6 without being reflected by the movable mirror 10 and is incident on the monitoring optical waveguide core 34 increases. Since the amount of light that is reflected by 10 and incident on the output optical waveguide core 33 is reduced, the amount of light attenuation increases.
[0036]
FIG. 6 is a schematic configuration diagram showing an example of an optical variable attenuator having an array structure as still another embodiment of the optical variable attenuator according to the present invention.
[0037]
In the figure, the optical variable attenuator 40 of this embodiment has a planar waveguide 41, and the optical waveguide cores 3 to 5 described above are formed in an array on the planar waveguide 41. Yes. The planar waveguide 41 is provided with a groove portion 42 that is connected to each pair of the optical waveguide cores 3 to 5 and extends in the parallel arrangement direction of the optical waveguide cores 3 to 5 (width direction of the planar waveguide 41). .
[0038]
At one end of the planar waveguide 41, the arrangement pitch D ₁ of the the input optical waveguide core 3 and the monitoring optical waveguide core 5 is 127 [mu] m. Further, at the other end of the planar waveguide 41, the arrangement pitch D2 of the _two adjacent output optical waveguide cores 4 is 250 μm.
[0039]
A fiber array 47 holding each optical fiber 44 of the optical fiber ribbon 43 and each optical fiber 46 of the optical fiber ribbon 45 is fixed to one end face of the planar waveguide 41. At this time, the fiber array 47 is formed so that each optical fiber 44 of the optical fiber ribbon 43 is connected to the input optical waveguide core 3 and each optical fiber 46 of the optical fiber ribbon 45 is connected to the monitoring optical waveguide core 5. The optical fibers 44 and 46 are configured to be held alternately. The arrangement pitch of the optical fibers 44 of the optical fiber ribbon 43 and the arrangement pitch of the optical fibers 46 of the optical fiber ribbon 45 are 250 μm, respectively, and the arrangement pitch of the optical fibers 44 and 46 of the fiber array 47 is 127 μm. .
[0040]
With this configuration, the input optical fiber connected to the input optical waveguide core 3 and the monitor optical fiber connected to the monitor optical waveguide core 5 are grouped. The wiring configuration is simplified without being complicated. In addition, since the monitoring optical fibers are configured in an array, direct connection with a light receiver array (for example, a PD array) for monitoring the amount of light is possible, and a reduction in size and cost can be achieved.
[0041]
A fiber array 50 holding each optical fiber 49 of the optical fiber ribbon 48 is fixed to the other end face of the planar waveguide 41. Each optical fiber 49 is connected to the output optical waveguide core 4. The arrangement pitch of each optical fiber 49 is 250 μm.
[0042]
On the planar waveguide 41, a plurality of actuator structures 7 having the above-described movable mirror 10 are provided corresponding to the respective optical waveguide cores 3 to 5.
[0043]
FIG. 7 is a configuration diagram showing an optical add / drop multiplexer (OADM) as an application example of the optical variable attenuator module including the optical variable attenuator 40 described above. The OADM 60 has a function of adding / dropping a signal of an arbitrary wavelength from among the wavelength multiplexed signals.
[0044]
In the figure, an OADM 60 includes a duplexer 61, an optical switch 62, an input monitor 63, the optical variable attenuator 40, an output monitor 64, a multiplexer 65, and a controller 66. . The demultiplexer 61 demultiplexes a plurality of optical signals having different wavelengths that have propagated through one optical fiber 67 for each wavelength.
[0045]
The optical switch 62 has a plurality of 2 × 2 switch units. The optical switch 62 is connected to the duplexer 61 via a plurality of input optical fibers 68, and is connected to the input monitor 63 via a plurality of output optical fibers 69. The optical switch 61 is connected to a plurality of Add optical fibers 70 and a plurality of Drop optical fibers 71. The optical switch 62 switches the optical path between the input optical fiber 68 and the add optical fiber 70 and switches the optical path between the output optical fiber 69 and the drop optical fiber 71.
[0046]
The input monitor 63 has a plurality of sets of optical directional couplers and light receivers as shown in FIG. 3 and detects the power (light quantity) of light passing through each output optical fiber 69. The variable optical attenuator 40 is connected to the input monitor 63 via a plurality of input optical fibers 44 (see FIG. 6) and coupled via a plurality of output optical fibers 49 (see FIG. 6). It is connected to a waver 65. The output monitor 64 is connected to the optical variable attenuator 40 via a plurality of monitoring optical fibers 46 (see FIG. 6). The output monitor 64 includes, for example, a light receiver array, and detects the light amount of the optical signal after the attenuation amount control by the optical variable attenuator 40.
[0047]
The multiplexer 65 multiplexes the optical signals of each wavelength attenuated by the optical variable attenuator 40 and guides them to one optical fiber 72. The controller 66 has a plurality of voltage sources for supplying a voltage to the optical switch 62 and a plurality of voltage sources for supplying a voltage to the optical variable attenuator 40 (corresponding to the voltage source 13 in FIG. 1). The controller 66 sends a voltage signal to the optical switch 62 to perform optical path switching control, and based on the detection values of the input monitor 63 and the output monitor 64, the variable optical attenuator 40 so that the optical attenuation amount becomes a desired value. A voltage signal is sent to.
[0048]
The present invention is not limited to the above embodiment. For example, in the above embodiment, the movable mirror 10 is driven by the electrostatic force generated between the cantilever 8 and the electrode 11, but the means for driving the movable mirror 10 is not particularly limited to this, and electromagnetic force is generated. You may use the electromagnetic actuator etc. which were utilized.
[0049]
In the above embodiment, the light attenuation amount is minimized in the initial state in which the cantilever 8 extends straight. However, the light attenuation amount may be maximized in the initial state.
[0050]
Furthermore, in the above-described embodiment, a planar waveguide having an input optical waveguide core, an output optical waveguide core, and a monitor optical waveguide core is provided. However, the present invention uses an optical fiber as an input optical waveguide and an output optical waveguide. The present invention can also be applied to a waveguide and a monitor optical waveguide.
[0051]
【The invention's effect】
According to the present invention, it is possible to monitor the light amount of the attenuated optical signal without branching a part of the attenuated optical signal, so that it is possible to suppress an increase in optical loss of the optical variable attenuator module. it can.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of an optical variable attenuator according to the present invention.
FIG. 2 is a plan view showing an operating state of the optical variable attenuator shown in FIG.
FIG. 3 is a configuration diagram illustrating an example of an optical variable attenuator module including the optical variable attenuator illustrated in FIG. 1;
FIG. 4 is a configuration diagram showing another optical variable attenuator module having an input monitor function and an output monitor function as a comparative example.
FIG. 5 is a plan view showing another embodiment of an optical variable attenuator according to the present invention.
FIG. 6 is a plan view showing still another embodiment of the variable optical attenuator according to the present invention.
7 is a configuration diagram showing an optical add / drop multiplexer (OADM) as an application example of the optical variable attenuator module including the optical variable attenuator shown in FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical variable attenuator, 2 ... Planar waveguide, 3 ... Input optical waveguide core, 4 ... Output optical waveguide core, 5 ... Monitor optical waveguide core, 6 ... Groove part, 7 ... Actuator structure, 8 ... Piece Holding beam (driving means), 10 ... movable mirror, 11 ... electrode (driving means), 13 ... voltage source (driving means), 20 ... variable optical attenuator module, 30 ... variable optical attenuator, 31 ... planar waveguide, 32 ... Optical waveguide core for input, 33 ... Optical waveguide core for output, 34 ... Optical waveguide core for monitoring, 35 ... Groove, 40 ... Optical variable attenuator, 41 ... Planar waveguide, 42 ... Groove, 60 ... Variable optical attenuation Module.

Claims (4)

An input optical waveguide for inputting an optical signal;
An output optical waveguide that is provided to face the input optical waveguide and outputs the optical signal;
A monitoring optical waveguide provided on the same side as the input optical waveguide, for monitoring the light quantity of the optical signal;
A movable mirror that is disposed between the input optical waveguide and the output optical waveguide, and reflects light from the input optical waveguide toward the monitor optical waveguide;
A variable optical attenuator comprising driving means for moving the movable mirror in a direction crossing the input optical waveguide. An input optical waveguide for inputting an optical signal;
An output optical waveguide provided on the same side as the input optical waveguide and outputting the optical signal;
A monitoring optical waveguide provided to face the input optical waveguide, and for monitoring the amount of the optical signal;
A movable mirror that is disposed between the input optical waveguide and the monitor optical waveguide and reflects light from the input optical waveguide toward the output optical waveguide;
A variable optical attenuator comprising driving means for moving the movable mirror in a direction crossing the input optical waveguide. The input optical waveguide, the output optical waveguide and the monitor optical waveguide are formed of planar waveguides,
3. The planar waveguide is provided with a groove portion that is connected to the input optical waveguide, the output optical waveguide, and the monitor optical waveguide and in which the movable mirror is disposed. Optical variable attenuator. An optical variable attenuator module comprising the optical variable attenuator according to claim 1.

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