JP3696024B2 - Optical waveguide modulator with output light monitor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical waveguide modulator with an output light monitor. More specifically, the present invention uses radiation mode light radiated from the optical waveguide as output light for monitoring in an appropriate direction, and without changing the substantial structure of the modulator itself, by simple monitoring means, The present invention relates to an optical waveguide modulator with an output light monitor capable of monitoring output light.
[0002]
[Prior art]
As a method of monitoring the output light of the optical waveguide device, there is a method in which a directional coupler (coupler) or the like is arranged in the optical waveguide device and a monitor light output waveguide is provided separately from the optical signal output waveguide. Generally done. In this method, it is necessary to newly provide an optical circuit for monitoring light branching in the optical waveguide element, and the optical fiber for monitor output is connected to the optical waveguide element separately from the optical fiber for optical output signal. There is a need to.
[0003]
As another monitoring method, as disclosed in Japanese Patent Laid-Open No. 11-194237, an inclined hole is formed in the clad portion on the optical waveguide, or a diffraction lens is disposed on the optical waveguide element, and the optical waveguide A system is known in which a part of the signal output light is taken out of the element substrate by this lens or the like. In this method, it is necessary to newly install a monitor light extraction lens or the like on the optical waveguide type optical waveguide element, and the monitor light is extracted above the optical waveguide element. The light receiving member must be attached to the optical waveguide type element after it is mounted in the housing case, and this attachment requires considerable labor.
[0004]
Furthermore, Japanese Patent Laid-Open No. 5-34650 discloses a system in which the end of an optical waveguide element is formed obliquely, a part of light output from the waveguide is reflected obliquely, and this reflected light is received as monitor light. Has been. In this method, it is necessary to select the inclined shape of the element end face within a range that does not adversely affect the main output light from the element. Therefore, there is a problem with the practicality of this method.
[0005]
Japanese Patent Application Laid-Open No. 5-53086 describes a device that directly installs a light receiving element on an optical waveguide element and directly receives and monitors a part of signal output light in the optical waveguide. In this device, it is necessary to mount the light receiving element mounting means on the optical waveguide element, and the mounting of the mounting means and the work for connecting the light receiving element to it and the adjustment work are performed by attaching the optical waveguide element to the optical waveguide element. Since it is performed after being mounted in the housing case, it is quite difficult to attach and adjust the light receiving element, and the possibility of damaging the optical waveguide element is increased.
[0006]
[Problems to be solved by the invention]
The present invention uses the radiation mode light emitted from the optical waveguide as the output light for monitoring in an appropriate direction, and allows the output by the monitoring means having a simple structure without changing the substantial structure of the modulator itself. It is an object of the present invention to provide an optical waveguide modulator with an output light monitor that can monitor the intensity of light.
[0007]
[Means for Solving the Problems]
An optical waveguide modulator with an output light monitor of the present invention includes an optical waveguide element having a dielectric substrate and an optical waveguide formed on a surface portion thereof, and
An optical fiber bonded to the output end of the optical waveguide;
A reinforcing member that reinforces a joint between the optical waveguide and the optical fiber;
A light receiving element that receives radiation mode light emitted from the substrate output side end face of the optical waveguide element;
Including
The optical waveguide has a plurality of waveguide sections, a coupling section where these waveguide sections converge and couple, and an output section continuous to the coupling section,
The reinforcing member has a size sufficient to receive and propagate radiation mode light emitted from the coupling portion of the optical waveguide, and is bonded to the output-side end surface of the optical waveguide element And an inclined end face that is opposed to the inclined end face and is formed to be inclined with respect to the joined end face, and a through hole or a groove that communicates the joined end face and the inclined end face,
The optical fiber is held in the through hole or groove of the reinforcing member and joined to the output end of the optical waveguide,
A light reflection film is formed on the inclined end surface of the reinforcing member, and the radiation mode light emitted from the coupling portion of the optical waveguide and propagated through the reinforcing member is reflected.
The light receiving element is disposed at a position for receiving the reflected radiation mode light on the inclined surface of the reinforcing member.
It is characterized by this.
In the optical waveguide modulator with an output light monitor according to the present invention, the reinforcing member is a glass cylindrical body, the optical fiber through hole or groove is formed along the longitudinal axis, and the longitudinal The shaft and the inclined end surface may be oblique.
In the optical waveguide modulator with an output light monitor according to the present invention, the light reflecting film formed on the inclined end face of the reinforcing member is preferably made of a metal or a dielectric.
In the optical waveguide modulator with an output light monitor of the present invention, an excess portion of the adhesive used for bonding the reinforcing member and the optical waveguide element is accommodated in the vicinity of the joint end surface of the bottom surface of the reinforcing member. It is preferable to form a first dirt prevention groove, thereby preventing dirt on the radiation mode light emitting surface of the reinforcing member.
In the optical waveguide modulator with an output light monitor according to the present invention, an excess portion of the adhesive used for bonding the optical fiber and the through hole or groove in the vicinity of the inclined end surface of the bottom surface of the reinforcing member It is preferable that a second anti-stain groove is formed so as to prevent the radiating surface of the reinforcing member from emitting radiation mode light.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In an optical modulator that obtains an ON / OFF signal output using a Mach-Zehnder type waveguide or the like, radiation mode light generated in an OFF mode state, that is, a state in which no optical signal is output, is an output in which the optical signal output is guided. The light is emitted into the substrate obliquely outward with respect to the optical waveguide. This radiation mode light usually propagates in the substrate, and is finally emitted to the outside from the end face of the substrate. Further, since the amount of radiation mode light is inversely proportional to the amount of optical signal output passing through the output optical waveguide, the optical signal output can be monitored by detecting the radiation mode light.
[0009]
An optical fiber for receiving an optical signal output from the optical waveguide and guiding it to the outside of the modulator is attached to the substrate end face of the optical modulator, but the outer diameter of this optical fiber is as very thin as 125 μm. Simply bonding to the end face will result in insufficient adhesive strength. For this reason, the "fiber reinforcing member" is used to cover the optical fiber, and one end face of the reinforcing member is adhered to the end face of the substrate to reinforce and protect the connection portion between the optical fiber and the optical waveguide, and the adhesive strength is increased. Can be improved. Generally, a silicon material or a ceramic material is usually used for the optical fiber reinforcing member. Here, if the fiber reinforcing member is made of a material that transmits signal light / radiation mode light, and is formed to have a size that can receive the radiation mode light emitted from the end face of the substrate, the radiation mode light can be obtained. Can be guided into the fiber reinforcing member.
[0010]
The opposite end surface of the optical fiber reinforcing member (the surface of the optical fiber reinforcing member opposite to the bonding end surface bonded to the output end surface of the optical waveguide element) is formed so as to be inclined with respect to the bonding end surface. When the light reflecting film is formed on the inclined end face, the reflection mode light propagating through the reinforcing member is reflected on the inclined end face, and the outside of the reinforcing member (different from the direction in which the output optical fiber is taken out, , Down or left). This radiated light is detected by disposing a light receiving element such as a photodiode (PD) disposed separately from the optical waveguide element in the optical waveguide element case, and measuring the amount of radiation mode light. From the value, the amount of light output from the optical waveguide can be monitored.
[0011]
By setting the inclination angle and direction of the inclined end face of the reinforcing member, the reflection radiation direction of the radiation mode light can be set, and the light receiving element can be arranged, attached and wired at a position where the radiation light can be received. . Therefore, it is possible to select the arrangement position of the light receiving element so as not to affect the function of the optical waveguide element and the arrangement position of each member by setting the inclined end face of the reinforcing member. The reflective film on the inclined end surface of the reinforcing member is preferably made of a metal or a dielectric, and can improve the reflection efficiency of the radiation mode light. This reflective film can be formed, for example, by sputtering metal aluminum.
[0012]
The optical waveguide of the optical waveguide element has a plurality of waveguides, a coupling portion where they converge and couple, and an output portion continuous to the coupling portion, and these are formed on the surface portion of the dielectric substrate. The plurality of waveguides may be branched from one light input section, or may be one that inputs light at the end face opposite to the coupling section.
[0013]
One end face of the optical fiber is bonded to the output end of the optical waveguide, and the bonded end portion of the optical fiber is reinforced by a reinforcing member. The reinforcing member has a size sufficient to receive and propagate the radiation mode light radiated from the optical waveguide, and one end surface thereof is bonded to the output side end surface of the optical waveguide element to form a joint end surface. The opposite end face forms an inclined end face that is inclined with respect to the joining end face, and a light reflecting film is formed thereon. The reinforcing member has a through hole or a groove for communicating the inclined end surface and the inclined end surface and holding the optical fiber. The through hole or groove is formed along the longitudinal direction of the reinforcing member, and the longitudinal axis and the inclined end surface are obliquely crossed. The groove may or may not be covered by a lid after the optical fiber is placed. The end face of the optical fiber held in the through hole or groove of the reinforcing member is joined to the output end face of the optical waveguide as described above.
[0014]
FIG. 1 is an explanatory plan view (excluding a ceiling plate) showing an example of the configuration of an optical waveguide modulator with an output light monitor of the present invention, and FIG. 2 is an explanatory side sectional view of the modulator of FIG. FIG. 3 is an explanatory side view showing the configuration of the joint portion between the end face of the optical waveguide element, the optical fiber, and the reinforcing member of the modulator shown in FIGS. 1 and 2. FIG. 4 is a plan view showing a configuration of an example of a conventional optical waveguide modulator with an output light monitor.
1, 2, 3 and 4, a Mach-Zehnder (MZ) type optical waveguide 2 and its control electrode 3 are arranged on a substrate 1 of an optical waveguide type device, and output signal light 4 is output from the output end of the optical waveguide 2. Is output. Radiation mode light 5 is emitted from the coupling portion 16 of the optical waveguide 2, propagates through the substrate 1, and is emitted toward the outside of the substrate 1.
The modulator is accommodated in the modulator case 14, and the input light 13 is input to the optical waveguide 2 by the input side optical fiber 11. The optical fiber 11 is held and reinforced by the input side fiber reinforcing member 12, and the tip thereof is connected to the input end of the optical waveguide 2. The control electrode is controlled by a control signal that is input through the control signal input connector 17a and output through the output connector 17b.
In the modulator with an output light monitor of the present invention shown in FIGS. 1 to 3, the joint end face of the reinforcing member 6 is joined to the output end face of the optical waveguide element, and the radiation propagated in the substrate 1 The mode light 5 is guided inside the reinforcing member 6. In the light reflecting film formed on the inclined end surface 7 of the reinforcing member 6, the radiation mode light 5 is reflected and emitted outside the reinforcing member, and this radiation mode light 9 is received and monitored by the light receiving element 10. . A monitor signal output from the light receiving element 10 is output through a connector 18 provided in the case 14. The end face of the optical output fiber 8 held by the through hole formed in the reinforcing member 6 is joined to the output end face of the optical waveguide 2.
On the other hand, in the conventional modulator with an output light monitor shown in FIG. 4, the optical waveguide 20 for monitor light is connected to the downstream portion of the coupling portion 16 of the optical waveguide 2 by the directional coupler 19. In addition, a part of the light output through the coupling portion 16 is guided as monitor light, and its output end is joined to the monitor light optical fiber 22 at the reinforcing member 6, and this monitor light optical fiber The monitor light output through 22 is received by the light receiving element 10, and a monitor signal is output from the light receiving element 10.
[0015]
1 to 3, the end face of the input side optical fiber 11 is joined to the input end face of the optical waveguide 1, and this joined part is reinforced by the input side reinforcing member 12. Input light 13 is input from the optical fiber 11 to the optical waveguide 2.
Each member joined as described above is accommodated in the case 14, and its upper opening is sealed by a ceiling plate (not shown). The other ends of the input side and output side optical fibers are led out of the case through through holes provided in the case side wall. The through hole may be sealed, but the case ceiling and the case through hole part may not be sealed only by attaching and fixing the respective members.
[0016]
The reinforcing member used in the present invention is formed of a silicon material or a ceramic material (for example, borosilicate glass or the like) that is transparent to the radiation mode light, and has a special dimension as long as the desired radiation mode light can be monitored. Although there is no restriction | limiting, it is preferable that it is a glass cylinder. The optical fiber holding through-hole or groove is preferably formed along the longitudinal axis of the cylindrical body, and the longitudinal axis and the inclined end surface cross each other.
[0017]
As shown in FIG. 2, a first dirt prevention groove 15 a is formed in the vicinity of the joint end face of the bottom surface of the reinforcing member 6, and a second dirt prevention groove 15 b in the vicinity of the inclined end face of the bottom surface of the reinforcing member 6. Is formed. The first dirt prevention groove 15a accommodates an excess portion of the adhesive used for bonding the reinforcing member and the optical waveguide element, thereby causing dirt on the radiation mode light emitting surface of the reinforcing member. To prevent that. Further, the second anti-stain groove 15b accommodates an excess portion of the adhesive used for bonding the optical fiber and the through hole or groove of the reinforcing member, whereby the radiation mode light of the reinforcing member is received. The contamination of the radiation surface can be prevented.
[0018]
The optical waveguide modulator with an output light monitor of the present invention has the following advantages.
1) The structure is simple.
That is, the shape and structure of the light intensity modulator element, the element mounting method and the technique are the same as those having no monitor output, and no new technique is required.
2) The monitor output light is spatially propagated and does not require a light guiding fiber.
Therefore, special work such as fiber connection to the monitor light output waveguide, mounting of the light receiving element on the optical waveguide element and wiring is not required when the optical waveguide element is assembled in the case. In addition, the light receiving element and its wiring can be incorporated in the case in advance, and it is not necessary to perform a special design in the case in order to perform the above operation.
3) Monitor light can be emitted in any direction.
Therefore, since the position of the light receiving element can be freely selected, it is possible to place the light receiving element in an empty part in the case, and it is unnecessary to perform a special design for placing the light receiving element in the case. Become.
4) Use radiation mode light.
As a non-intensity modulator, radiation mode light, which is normally discarded, is used as a monitor, so there is no need to provide a special design part such as a branch part for monitor light output in the optical waveguide element. There will be no increase in the transmission loss of light which becomes a problem.
Therefore, the conventional light intensity modulation element can be used as it is, and the arrangement of the monitoring optical waveguide branching portion and the monitor light extraction lens is unnecessary.
[0019]
【The invention's effect】
The optical waveguide modulator with output light monitor of the present invention has an advantage that the monitor light detection means can be provided with a simple structure and arrangement because the radiation mode light is used as the monitor light, and it is advantageously practically used. it can.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view showing a configuration of an example of an optical waveguide modulator with an output light monitor according to the present invention.
FIG. 2 is an explanatory front view showing the configuration of the modulator shown in FIG. 1;
FIG. 3 is a side cross-sectional explanatory view showing the arrangement of reinforcing members and optical fibers on the output end face of the optical waveguide device and the state of output light and radiation mode light of the modulator shown in FIGS. 1 and 2;
FIG. 4 is an explanatory plan view showing a configuration of an example of a conventional optical waveguide modulator with an output light monitor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Modulator board | substrate 2 ... MZ type | mold optical waveguide 3 ... Control electrode 4 ... Output signal light 5 ... Radiation mode light 6 ... Output side fiber reinforcement member 7 ... Inclined end surface 8 with a light reflection film ... Output optical fiber 9 ... Radiation mode Light 10 ... Light receiving element 11 ... Input side optical fiber 12 ... Input side fiber reinforcing member 13 ... Input light 14 ... Modulator cases 15a and 15b ... First and second antifouling grooves 16 ... Coupling portions 17a and 17b of the optical waveguide 2 ... Control signal input / output connector 18 ... Monitor signal output connector 19 ... Directional coupler (coupler)
20 ... Optical waveguide for monitor light 21 ... Monitor light 22 ... Optical fiber for monitor light

Claims (5)

An optical waveguide element having a dielectric substrate and an optical waveguide formed on a surface portion thereof;
An optical fiber bonded to the output end of the optical waveguide;
A reinforcing member that reinforces a joint between the optical waveguide and the optical fiber;
A light receiving element that receives radiation mode light emitted from the substrate output side end face of the optical waveguide element;
Including
The optical waveguide has a plurality of waveguide sections, a coupling section where these waveguide sections converge and couple, and an output section continuous to the coupling section,
The reinforcing member has a size sufficient to receive and propagate radiation mode light emitted from the coupling portion of the optical waveguide, and is bonded to the output-side end surface of the optical waveguide element And an inclined end face that is opposed to the inclined end face and is formed to be inclined with respect to the joined end face, and a through hole or a groove that communicates the joined end face and the inclined end face,
The optical fiber is held in the through hole or groove of the reinforcing member and joined to the output end of the optical waveguide,
A light reflection film is formed on the inclined end surface of the reinforcing member, and the radiation mode light emitted from the coupling portion of the optical waveguide and propagated through the reinforcing member is reflected.
The light receiving element is disposed at a position for receiving radiation mode light reflected on the inclined end surface of the reinforcing member,
An optical waveguide modulator with an output light monitor. The reinforcing member is a glass cylinder, the optical fiber through-hole or groove is formed along the longitudinal axis thereof, and the longitudinal axis and the inclined end surface are obliquely crossed.
The optical waveguide modulator with an output light monitor according to claim 1.   The optical waveguide modulator with an output light monitor according to claim 1, wherein the light reflecting film formed on the inclined end face of the reinforcing member is made of a metal or a dielectric.   A first antifouling groove for accommodating an excess portion of the adhesive used for bonding the reinforcing member and the optical waveguide element is formed in the vicinity of the joint end surface of the bottom surface of the reinforcing member, thereby forming the reinforcing member The optical waveguide modulator with an output light monitor according to claim 1, wherein contamination of the radiation mode light radiation surface is prevented.   In the vicinity of the inclined end surface of the bottom surface of the reinforcing member, a second antifouling groove for accommodating an excess portion of the adhesive used for bonding the optical fiber and the through hole or groove is formed, 2. The optical waveguide modulator with an output light monitor according to claim 1, wherein contamination of the radiation mode light radiation surface of the reinforcing member is thereby prevented.

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