JP3587757B2 - Optical waveguide type optical modulator with output light monitor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical waveguide modulator with an output light monitor. More specifically, the present invention utilizes radiation mode light emitted from an optical waveguide as an output light for monitoring in an appropriate direction, without changing the substantial structure of the modulator itself, and by simple monitoring means. The present invention relates to an optical waveguide type modulator with an output light monitor capable of monitoring output light and performing feedback control of an operating point of the optical modulator.
[0002]
[Prior art]
As a method of monitoring the output light of the optical waveguide device, a method of disposing a directional coupler (coupler) or the like in the optical waveguide device and providing a monitor light output waveguide separately from the optical signal output waveguide is known. Generally done. In this method, it is necessary to newly provide a monitor light branching optical circuit in the optical waveguide element, and connect the monitor output optical fiber to the optical waveguide element separately from the optical output signal optical fiber. There is a need to.
[0003]
Further, as another monitoring method, as disclosed in Japanese Patent Application Laid-Open No. 11-194237, an inclined hole is formed in a clad portion on an optical waveguide, There is known a method in which a part of the signal output light inside is taken out of the element substrate by using 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 since the monitor light is extracted above the optical waveguide element, the monitor light is removed. The light receiving member must be attached to the optical waveguide element after the optical waveguide element has been mounted in the housing case, and this attachment requires considerable time and effort.
[0004]
Further, Japanese Patent Application Laid-Open No. Hei 5-34650 discloses a method in which an element end of an optical waveguide element is formed obliquely, a part of light output from the waveguide is reflected obliquely, and the reflected light is received as monitor light. Have been. In this method, it is necessary to select the inclination shape of the element end surface within a range that does not adversely affect the main output light from the element. Therefore, there is a problem in the practicality of this method.
[0005]
Japanese Patent Application Laid-Open No. 5-53086 describes a device in which a light receiving element is provided directly on an optical waveguide element, and a part of signal output light in the optical waveguide is directly received and monitored. In this device, it is necessary to mount the light receiving element mounting means on the optical waveguide element, and the mounting of this mounting means and the work of connecting the light receiving element thereto and the adjustment work are performed by connecting the optical waveguide element to the optical waveguide element. Since the mounting and adjustment work of this light receiving element is performed after mounting in the case to be accommodated, it is very difficult, and the possibility of damaging the optical waveguide element is increased.
[0006]
[Problems to be solved by the invention]
The present invention utilizes a radiation mode light emitted from an optical waveguide as an output light for monitoring in an appropriate direction, without changing the substantial structure of the modulator itself, and having a simple structure and excellent processability. Another object of the present invention is to provide an optical waveguide type modulator with an output light monitor capable of monitoring the intensity of output light by a monitor using a capillary having optical fiber operability.
[0007]
[Means for Solving the Problems]
An optical waveguide type optical modulator with an output light monitor of the present invention is formed on a dielectric substrate, a surface portion of the substrate, and extends from two or more branch optical waveguide portions and a union point of these branch optical waveguide portions. An optical waveguide having an optical waveguide output portion, and an optical waveguide element having an optical waveguide output end portion reinforcing member for reinforcing an output end portion of the optical waveguide output portion,
An optical fiber having one end face connected to the output end of the optical waveguide output section,
An optical fiber reinforcing member for reinforcing a connection between the output end of the optical waveguide output section and the end face of the optical fiber,
A photoelectric receiving part of the radiation mode light radiated from the unifying point of the branch optical waveguide part and propagated through both sides of the optical waveguide output part via the dielectric substrate and the optical fiber reinforcing member. A conversion element;
Has,
The optical fiber reinforcing member has a hollow portion that accommodates the optical fiber connection end portion, and is a capillary that propagates the radiation mode light,
One end surface of the capillary is bonded to the dielectric substrate and an end surface of the optical waveguide output end reinforcing member,
Only about a half of the other end surface forming the tip end surface of the capillary, a part of the radiation mode light is reflected toward the photoelectric conversion element, and a reflection surface for monitor light for receiving the light is formed, The other half forms a non-monitor surface where the radiation mode light is not received by the photoelectric conversion element.
It is characterized by the following.
In the optical waveguide type optical modulator with an output light monitor of the present invention, the reflection surface of the capillary is inclined with respect to a longitudinal axis of the hollow portion of the capillary, and a radiation mode reflected on the reflection surface is provided. Preferably, light is received by the photoelectric conversion element.
In the optical waveguide type optical modulator with output light monitor of the present invention, it is preferable that the capillary has a hollow cylindrical shape.
In the optical waveguide type optical modulator with an output light monitor of the present invention, a boundary line between the approximately half part of the tip end surface of the capillary forming the reflection surface and the other approximately half part forms the reflection surface. Half, and in the middle of the propagation path of the radiation mode light passing through each of the other halves, and this boundary line intersects the central axis of the hollow portion of the capillary at the tip end surface of the capillary, And a center line extending in the same direction as the boundary line, and a tangent line parallel to the center line and in contact with the outer peripheral line of the hollow portion of the capillary, which is in contact with the approximately half-side portion forming the reflection surface. It is preferably located between them.
In the optical waveguide type optical modulator with an output light monitor of the present invention, the non-monitor surface of the capillary is formed by cutting the other approximately half inward while removing the reflection surface at the tip end surface of the capillary. It may be.
In the optical waveguide type optical modulator with an output light monitor of the present invention, the non-monitor surface of the capillary may be a non-reflection surface that does not reflect the radiation mode light.
In the optical waveguide type optical modulator with an output light monitor according to the present invention, the means for blocking the reflection mode light reflected on the non-monitor surface with respect to the non-monitor surface of the capillary, comprises: It may be arranged between the element and the light receiving surface.
In the optical waveguide type optical modulator with an output light monitor of the present invention, means for blocking the radiation mode light upstream of the non-monitor surface is provided in the capillary with respect to the non-monitor surface of the capillary. You may.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In an optical modulator that obtains an ON / OFF signal output using a Mach-Zehnder waveguide or the like, the radiation mode light generated in the OFF mode state, that is, in a state where no optical signal is output, is transmitted through the optical signal output in the substrate. The wave is radiated obliquely outward with respect to the output optical waveguide. This radiation mode light normally propagates through the substrate while leaving the waveguide output portion at a radiation angle of about 0.7 degrees, and is finally radiated outside from the end face of the substrate. Further, since the light quantity of the radiation mode light is complementary to the light quantity of the 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 the optical signal output from the optical waveguide and guiding the light to the outside of the modulator is attached to the end face of the substrate of the optical modulator. However, since the outer diameter of this optical fiber is very thin, 125 μm, Simply adhering to the end face results in insufficient adhesive strength. For this reason, the optical fiber is covered using a “fiber reinforcing member”, and one end face of the reinforcing member is bonded to the end face of the substrate to reinforce and protect the connection portion between the optical fiber and the optical waveguide, thereby reducing the bonding strength. Can be improved. Generally, a silicon material or a ceramic material is used for the optical fiber reinforcing member. Here, if the fiber reinforcing member is made of a material through which signal light / radiation mode light is transmitted and is formed to have a size capable of receiving the radiation mode light radiated from the end face of the substrate, the radiation mode light Can be guided into the fiber reinforcing member.
[0010]
When the opposite end face of the optical fiber reinforcing member (the face of the optical fiber reinforcing member opposite to the joining end face bonded to the output end face of the optical waveguide element) is formed so as to be inclined with respect to the joining end face. At this inclined end surface, the radiation mode light propagating through the reinforcing member is reflected and radiated outside the reinforcing member (any direction different from the direction in which the output optical fiber is taken out, either right, down, or left). Is done. The emitted light is detected by arranging a light receiving element, for example, a photodiode (PD) arranged separately from the optical waveguide element in the optical waveguide element case, and measuring the light amount of the 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 the direction of the inclined end surface of the reinforcing member, the reflected radiation direction of the radiation mode light can be set, and the light receiving element can be arranged, mounted, 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 surface of the reinforcing member.
[0012]
The radiation mode light will be described with reference to FIGS. In FIG. 1A, an optical waveguide 1a is formed on a dielectric substrate 1, and the optical waveguide 1a is branched from the input section (not shown) connected to an optical input source. The branch portions 2 and 3, the output side portions 4 and 5 of the branch portions of the branch portions 2 and 3, and the output side portions 4 and 5 converge, and light passing through the branch portions 2, 3, 4 and 5 interferes. It has a merging point 6 to be multiplexed, and an output section 7 extending from the merging point 6. When an RF signal is applied to an electrode (not shown) arranged near the branching portions 2 and 3, the optical phases of the light waves passing through the branching portions 2 and 3 change differently, and these light waves are merged into a single point. When multiplexed at 6, the light interferes with each other, the light intensity changes according to the RF signal, and becomes a so-called optical signal, which is output from the waveguide output unit 7. Light complementary to the optical signal is emitted as radiation mode light 8 and 9 from the junction 6 into the substrate 1 and propagates through obliquely outward propagation paths 8 and 9 on both sides of the output unit 7. . The radiation mode lights 8 and 9 are higher-order mode lights than the single mode light output from the output unit 7 of the optical waveguide 1a, and the radiation mode lights 8 and 9 are 180 degrees out of phase with each other. .
[0013]
FIG. 1B is an explanatory view showing a right end face of the optical waveguide device of FIG. 1A, in which a signal light 11 passing through an output portion 7 of the optical waveguide and radiation mode light propagation paths 8a and 9a are shown. The passing radiation mode lights 8 and 9 form an angle of about 0.7 degrees.
[0014]
FIG. 2 is a plan view (partial cross section) of a part of an example of a conventional apparatus that uses the radiation mode light for monitoring. In FIG. 2, an optical waveguide output end partial reinforcing member 12 made of a material having the same optical characteristics as the substrate 1 and reinforcing the end surface is bonded to an output side end surface of the substrate 1. The substrate 1 and the reinforcing member 12 have the same optical axis.
[0015]
One end surface 16 of the capillary 13 is bonded and fixed to the output end surface 10 of the substrate 1. In FIG. 2, the substrate end face 10 and the capillary end face 16 are drawn apart from each other, but they are firmly bonded and fixed by an adhesive. A hollow portion 14 is formed along a central axis in the longitudinal direction of the capillary 13, and an optical fiber 15 is accommodated in the hollow portion 14 and fixed by an adhesive. The output end of the optical waveguide output part 7 is exposed to the hollow part 14 of the capillary 13, and the distal end face of the optical fiber 15 is bonded and fixed to this output end. The diameter of the hollow portion 14 is set to approximately the same as or slightly larger than the diameter of the optical fiber 15 so that the optical fiber 15 can be accommodated and the loss of the optical fiber can be prevented. You.
[0016]
The other end surface (tip surface) 17 of the capillary 13 is formed to be inclined with respect to the longitudinal axis of the hollow portion 14 of the capillary 13. The radiation mode lights 8 and 9 propagating in the interior 18 of the capillary 13 are reflected by the tip end face 17, and the reflected radiation mode lights 23 and 24 are received by the light receiving surface of the photoelectric conversion element 20. The photoelectric conversion element outputs a monitor signal based on the received radiation mode light.
[0017]
FIG. 3 exemplifies a waveform of light reflected from the reflection surface 17 and monitored and output by the photoelectric conversion element 20 in the apparatus of FIG. 2, and a curve 21 is output from the output optical fiber 15. The curve 22 is the waveform of the light obtained by monitoring the reflected radiation mode light 23 with the photoelectric conversion element 20. The two light waves 21 and 22 are different from each other, but have a complementary relationship.
[0018]
In the conventional device shown in FIG. 2, the radiation mode light 23 reflected from the upper half 17 a of the reflection surface 17 of the capillary 13 near the photoelectric conversion element 20 and the reflection mode light 23 reflected from the lower half 17 b far from the photoelectric conversion element 20. The emitted radiation mode light 24 is incident on the incident rectangular surface areas 25 and 26 of the light receiving surface of the photoelectric conversion element 20, as shown in FIG. The rectangular plane areas 25 and 26 overlap with each other in the plane area 27, and the radiation mode light incident on this plane area interferes with each other, so that the monitor light output of the photoelectric conversion element 20 changes the environmental temperature and other factors. The problem of fluctuation (fluctuation) due to disturbance occurs.
[0019]
The present invention solves the above problems and stabilizes the monitor light output from the photoelectric conversion element.
In the optical waveguide type optical modulator with an output light monitor of the present invention, the portion of the radiation mode light propagating inside the capillary 13 is directed to the photoelectric conversion element only at about half of the tip end surface of the capillary 13. A reflection surface for monitor light is formed in the front half so that light is reflected and received, and a non-monitor surface in which the photoelectric conversion element does not receive radiation mode light is formed in approximately half of the reflection surface. ing.
[0020]
FIG. 5 shows an example of an optical waveguide modulator with an output light monitor according to the present invention.
In FIG. 5, the end face of the output end of the substrate 1 and the end face of the output end of the reinforcing member 12 bonded thereto are inclined with respect to a plane perpendicular to the longitudinal center axis of the optical waveguide output section 7, for example, 5 degrees. It is formed with an inclination angle.
The direction of the longitudinal center axis of the capillary 13 also extends in a direction inclined with respect to the longitudinal direction of the optical waveguide output section 7, and accordingly, the output end face of the optical waveguide output section 7 and the connection end face of the optical fiber (shown in FIG. Are not connected). For example, the end surface of the reinforcing member 12 and a plane perpendicular to the longitudinal center axis 14a of the hollow portion 14 of the capillary 13 form an inclination angle of 7 degrees.
[0021]
In FIG. 5, a reflection surface is formed in the upper half portion 17a (approximately half portion near the photoelectric conversion element 20) of the distal end surface of the capillary 13, and only the radiation mode light 23 reflected on the upper half reflection surface 17a is photoelectrically reflected. The light is received by the conversion element 20. As shown in FIG. 5, the lower half of the capillary tip portion is cut to a depth W from the tip surface, and a portion 28 having a depth F from the peripheral surface of the capillary is removed. At the end face 29 formed in the lower half of the capillary 13 due to the removal of the removal portion 28, the radiation mode light is reflected in the direction of the arrow 29a, and is not received by the photoelectric conversion element 20. For this reason, in the optical modulator of FIG. 5, a part of the radiation mode light is reflected from the lower half of the capillary tip surface, and is not received by the photoelectric conversion element. As a result, as shown in FIG. The monitor light output from the photoelectric conversion element is stabilized without causing an interference area such as the surface area 27 that is present.
[0022]
The angle formed between the reflection surface 17a of the capillary 13 and the longitudinal center axis 14a of the hollow portion 14 can be appropriately set so that the reflected light is received by the photoelectric conversion element 20, but generally, the angle is 40 to 46 degrees. Preferably, the angle is set. The length of the capillary 13 is preferably set in the range of 2 to 4 mm so that the optical fiber can be securely held. The diameter of the capillary 13 is such that the desired amount of radiation mode light is received by the photoelectric conversion element. Although it can be appropriately set so as to form a required reflection surface for the formation, it is generally preferable that the thickness is about 0.25 to 2.5 mm. It is preferable that the radiation mode light reflected from the reflection surface 17a of the capillary 13 be incident on the light receiving surface of the photoelectric conversion element as incident light that forms a substantially right angle.
Preferably, the peripheral surface of the capillary has a cylindrical peripheral surface, in which case the peripheral surface of the capillary exhibits a cylindrical lens effect and has a finite focal length. It is preferable to arrange the light receiving surface of the photoelectric conversion element in the vicinity of the focal length, thereby improving the S / N.
[0023]
As shown in FIG. 5, the following effects are obtained by removing the lower half 28 of the tip end surface of the capillary 13.
(1) It is desirable that the hollow portion 14 of the capillary 13 has a diameter as large as possible to allow the optical fiber 15 to pass therethrough. However, since the radiation angle of the radiation mode light is as small as about 0.7 °, the radiation mode light is transmitted to the fleshy portion of the capillary. In order to propagate 18, the smaller the hole diameter of the hollow portion, the better. For this reason, the hole diameter is set to be about 1 μm larger than the outer diameter of the optical fiber, but in this case, as shown in FIG. is there. Usually, a tapered portion is provided in the optical fiber introduction portion to facilitate introduction of the optical fiber, but such a tapered introduction portion cannot be adopted for the same reason as described above. However, if the structure shown in FIG. 5 is adopted, the hollow portion facing the removal portion 28 functions as a hole fiber introduction groove, guides the optical fiber, and facilitates the introduction of the hollow portion of the optical fiber.
(2) Also, the optical fiber is usually fixed to the capillary for reinforcement after the alignment. However, this adhesive wraps around the reflection surface 17a and causes a problem that the reflection performance is fluctuated. The adhesive has a trapping function, and can prevent the adhesive from wrapping around the reflection surface 17a.
[0024]
In order for the capillary removal portion 28 to exhibit the above-described effect, the boundary line between the approximately half part of the tip surface of the capillary forming the reflection surface and the other approximately half forms the reflection surface. And the middle of the propagation path of the radiation mode light passing through each of the other halves, and this boundary line intersects the central axis of the hollow portion of the capillary at the tip end surface of the capillary. And a tangent line extending in the same direction as the boundary line, and a tangent line parallel to the center line and in contact with a portion of the outer peripheral line of the hollow portion of the capillary that is about a half-side portion forming the reflection surface. And it should be located between them. That is, in FIG. 5, when viewed in a section perpendicular to the longitudinal center line of the hollow portion of the capillary, as shown in FIG. 6, the boundary line between the approximately half portion forming the reflection surface 17a and the removed portion 28, as shown in FIG. It is preferable that the reference numeral 40 be located between the propagation paths 8a and 9a of the radiation mode light and between a center line 40a intersecting with the center axis 14a of the hollow portion 14 and a tangent line 40b contacting the outer periphery of the hollow portion 14. . In other words, in FIG. 5, the relationship among the depth of cut F from the outer periphery of the capillary, the radius R of the capillary, and the radius r of the hollow portion is as follows.
R ≦ F ≦ R + r
It is preferable that
[0025]
The capillary 13 and the hollow portion 14 are desirably concentric as described above, but may be slightly eccentric within a range where desired reflection can be made with respect to the radiation mode light. Further, the cut depth W of the removed portion 28 from the tip end of the capillary can be appropriately set, but is generally preferably set to 0.2 to 1 mm so as to achieve both workability and strength of the capillary. . Further, in order to eliminate the influence of the reflection of the radiation mode light on the reinforcing member 12 attached to the substrate 1 and the end face 10 of the substrate 1, the end face 10 is disposed between the end face 10 and a plane perpendicular to the optical waveguide output section 7. It is preferable to have an inclination angle of about 5 ° as described above, and to have an inclination angle of about 7 degrees between the end face 10 and a plane perpendicular to the longitudinal direction of the capillary hollow portion 14. Is preferred.
[0026]
In order to increase the reflectivity of the radiation mode light reflecting surface of the capillary, a metal film (for example, gold, chromium or aluminum film) or a dielectric multilayer film (for example, TiO. ₂ Film and SiO ₂ (Alternate multilayer film with film) is preferably deposited.
It is preferable to use a photodiode (PD) as the photoelectric conversion element, which receives radiation mode light, converts the light into an electric signal, and outputs the electric signal.
[0027]
【Example】
FIG. 7 shows an example of the optical modulator of the present invention. In FIG. 7, LiNbO is placed in a case (frame) 30. ₃ An optical waveguide 1a is formed on the surface of the substrate 1 made of a ferroelectric material such as an optical waveguide. The optical waveguide 1a is composed of an optical waveguide input section 32, branch sections 2 and 3 branched therefrom, and an output of the branch section. The electrodes 33, 34 are disposed on the branch portions 3, 4. An input end reinforcing member 12a is disposed at an input end of the substrate 1, and an input side capillary 31 is joined to the input end face thereof (in FIG. 7, both are separated from each other). The input side optical fiber 15 a is introduced through a section (not shown), and the distal end face is connected to the input end face of the optical waveguide input section 32.
[0028]
The output end of the optical waveguide 1a is connected to the output side capillary 13 and the output side optical fiber 15 in the same manner as in FIG.
Light is input from the input side optical fiber 15a reinforced by the reinforcing member 31 to the optical waveguide input section 32, and the light is distributed to the branch sections 2 and 3, and the electric signal 35 is applied to the electrodes 33 and 34, for example. When the voltage is applied to the branch portions 2 and 3 via the connector 36 disposed on the side surface of the case 30, the optical phase of the light wave propagating through the branch portions 2 and 3 changes according to the applied signal 35, and this light wave is The light is multiplexed at the coupling part 6 and interferes with each other to generate signal light. The signal light after this interference is output to the outside of the case 30 through the optical fiber 15 reinforced by the capillary 13.
[0029]
In the combined part 6, the radiation mode light 8 of the two radiation mode lights 8 and 9 emitted into the substrate 1 passes through the inside 18 of the capillary 13 and is formed in the upper half of the tip end surface of the capillary 13. While being reflected on the reflecting surface 17a and condensed on the cylindrical peripheral surface of the capillary 13, the light is emitted in a direction substantially perpendicular to the output portion 7 of the optical waveguide 1a (a direction substantially perpendicular to the side surface of the case 30). You. The radiated light flux 23 is arranged so that it can be received at a substantially right angle and at an angle at which the reflected light from the light receiving surface does not return to the reflecting surface (fixed to the side surface of the case 30). ) Light is received on the light receiving surface of the photoelectric conversion element (PD) 20. The signal of the received radiation mode light is converted into an electric signal in the photoelectric conversion element 20, and the electric signal 38 is output to the outside of the case 30 via the connector 37 as a light output monitor signal.
[0030]
The radiation mode light 9 radiated from the combined part propagates inside the capillary 13 and reaches the end face 29 of the removed part 28 formed in the lower half of the tip end face thereof. Is reflected in the direction 29a that does not reach the.
The above monitoring function can be obtained, for example, in an optical element having a Mach-Zehnder type optical waveguide and a configuration in which a branch portion is Y-type multiplexed.
[0031]
In the optical modulator of the present invention, the configuration of the non-monitor half of the tip side of the output side capillary that does not allow the photoelectric conversion element to receive the radiation mode light propagated through the output side capillary is described in FIGS. The non-monitor half may be formed by a non-reflective surface with respect to the radiation mode light, or the radiation mode light reflected from the non-monitor half may be formed by the non-monitor. The light may be shielded by a light shielding means disposed between the peripheral surface of the capillary and the photoelectric conversion element, or a means for blocking radiation mode light directed to the non-monitor half inside the capillary, for example, light shielding A concave portion may be formed, or a light shielding plate may be inserted.
[0032]
In FIGS. 5, 6 and 7, in order to reduce the reflection of radiation mode light on the end surface of the substrate, the end surface of the substrate is moved from a plane perpendicular to the direction of the optical waveguide output section 7 on the surface of the substrate. In the above, the case where the substrate is inclined by about 5 degrees (in the horizontal direction) has been described. However, when the end surface of the substrate is inclined with respect to the substrate surface, it is possible to form the capillary as shown in FIG. It is effective to make it easier.
[0033]
In FIG. 8, the substrate and its reinforcing member 12 are supported and arranged on the bottom surface in the case 30 by the support 39, and the output side end surface thereof is vertically inclined from a plane perpendicular to the substrate surface. One end surface of the capillary 13 is joined to the substrate output side end surface. At this time, the longitudinal center line of the hollow portion (not shown) of the capillary 13 is inclined by 42 to 48 degrees with respect to the substrate surface. Let it. The tip end face 17 of the capillary 13 is divided into two parts by an intersection line between the tip end face and a plane parallel to a vertical plane including the longitudinal center line of the hollow part (in this case, two minutes on the left and right sides of the intersection line). One half of the two halves is used as a reflecting surface, and the radiation mode light reflected from the reflecting surface is condensed by the cylindrical peripheral surface of the capillary, and the photoelectric conversion element (for example, the case 30) is used. (Located on the bottom surface of the light receiving surface). The other half of the capillary 13 is a non-monitor surface. The boundary between the reflection surface and the non-monitor surface is preferably set in the same manner as in FIG. 6, and the non-monitor surface may be formed in the same manner as described above.
[0034]
【The invention's effect】
The optical waveguide modulator with output light monitor according to the present invention has the following effects.
1) The structure is simple.
That is, the shape and structure of the light intensity modulator element, the method of mounting the element, and the technology are the same as those having no monitor output, and do not require a new technology.
2) The monitor output light is transmitted in space and does not require a light guiding fiber or the like.
Therefore, when assembling the optical waveguide element into the case, there is no need for special work such as connecting the fiber to the monitor light output waveguide, mounting the light receiving element on the optical waveguide element, and wiring. 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 to perform the above operation.
3) The 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 portion of the case, and it is not necessary to perform a special design for placing the light receiving element in the case. Become.
4) Use radiation mode light.
As the non-intensity modulator uses radiation mode light, which is normally discarded light, as a monitor, it is not necessary to provide a special design part such as a monitor light output branch in the optical waveguide element. There is no increase in transmission loss of light, which is a problem.
Therefore, the conventional light intensity modulating element can be used as it is, and the arrangement of the monitor optical waveguide branch portion and the monitor light extraction lens is unnecessary.
5) Accurate monitoring of monitor output with little or no disturbance fluctuation due to environmental climate is possible.
The optical waveguide modulator with an output light monitor of the present invention uses the radiation mode light as the monitoring light, so that the monitor light detecting means can be provided with a simple structure and arrangement, and further, the fluctuation due to disturbance is small, With or without the advantage, it can be used advantageously.
[Brief description of the drawings]
FIG. 1A is an explanatory plan view showing generation of radiation mode light in an optical waveguide element having a branch portion and a joining portion.
FIG. 1B is an explanatory side view showing generation of radiation mode light in the optical waveguide device of FIG. 1A.
FIG. 2 is an explanatory plan view showing a main part of a conventional optical waveguide type optical modulator with an output light monitor.
FIG. 3 is an explanatory diagram showing waveforms of signal light and monitor light output from the optical modulator of FIG. 2;
FIG. 4 is an explanatory diagram showing an incident surface area of a reflected radiation mode light in a photoelectric conversion element in the optical modulator of FIG. 2;
FIG. 5 is an explanatory plan view showing a configuration of a main part of the optical modulator according to the present invention.
FIG. 6 is an explanatory diagram showing an example of a shape of a radiation mode light reflecting surface on a tip end surface of a capillary of the optical modulator of FIG. 5;
FIG. 7 is an explanatory plan view showing an example of the configuration of the optical modulator according to the present invention.
FIG. 8 is an explanatory front view showing a main part of another example of the optical modulator according to the present invention.
[Explanation of symbols]
1. Dielectric substrate
1a: Optical waveguide
2,3 ... branch
4, 5 ... output part of branching part
6 ... united point
7 Output unit
8, 9 ... radiation mode light
8a, 9a: Propagation path of radiation mode light 8, 9
10. End face of reinforcing member
11 ... Signal light
12 ... Reinforcing member
12a: Input side reinforcing member
13. Capillary
14 ... hollow part
14a ... hollow part center line
15 Output optical fiber
15a ... input optical fiber
16: Connection end face of the capillary
17 ... Reflective surface
17a: Upper half of reflection surface
17b: lower half of reflection surface
18. Inside the capillary
20: photoelectric conversion element
21 ... Signal light waveform
22 ... waveform of radiation mode light
23, 24 ... reflected radiation mode light
25: Area of incidence of radiation mode light from the upper half of the reflecting surface
26: Area of incidence of radiation mode light from lower half of reflective surface
27: overlapping part of the incident surface areas 25 and 26
28 ... Removal part
W: Depth from the tip of the capillary
F: Depth from capillary surface
29: End face of lower half of capillary
29a: Direction of radiation mode light reflected on end face 29
30 ... Case
31 ... Input side capillary
32 ... input section
33, 34 ... electrodes
35 ... applied signal
36, 37… Connector
38 ... Electric signal
39 ... Support
40 ... borderline
40a: minimum end of the boundary line range
40b: Maximum end of boundary line range
R: radius of the capillary
r: radius of the hollow part

Claims (8)

A dielectric substrate, an optical waveguide formed on a surface portion of the substrate, having two or more branch optical waveguide portions, and an optical waveguide output portion extending from a union point of these branch optical waveguide portions, and the optical waveguide An optical waveguide element having an optical waveguide output end portion reinforcing member for reinforcing an output end portion of the output portion,
An optical fiber having one end face connected to the output end of the optical waveguide output section,
An optical fiber reinforcing member for reinforcing a connection between the output end of the optical waveguide output section and the end face of the optical fiber,
A photoelectric receiving part of the radiation mode light radiated from the unifying point of the branch optical waveguide part and propagated through both sides of the optical waveguide output part via the dielectric substrate and the optical fiber reinforcing member. A conversion element;
Has,
The optical fiber reinforcing member has a hollow portion that accommodates the optical fiber connection end portion, and is a capillary that propagates the radiation mode light,
One end surface of the capillary is bonded to the dielectric substrate and an end surface of the optical waveguide output end reinforcing member,
Only about a half of the other end surface forming the tip end surface of the capillary, a part of the radiation mode light is reflected toward the photoelectric conversion element, and a reflection surface for monitor light for receiving the light is formed, An optical waveguide type optical modulator with an output light monitor, characterized in that the other approximately half has a non-monitor surface on which the photoelectric conversion element does not receive the radiation mode light. The said reflection surface of the said capillary is inclined with respect to the longitudinal direction axis | shaft of the said hollow part of this capillary, The radiation mode light reflected in the said reflection surface is made to receive the said photoelectric conversion element. Optical waveguide type optical modulator with output light monitor. The optical waveguide type optical modulator with an output light monitor according to claim 2, wherein the capillary has a hollow cylindrical shape. A boundary line between the approximately half of the capillary tip surface that forms the reflective surface and the other approximately half is the half of the capillary that forms the reflective surface and the radiation that passes through the other half. A center line, which is located in the middle of the propagation path of the mode light, and whose boundary line intersects the center axis of the hollow portion of the capillary at the tip end surface of the capillary and extends in the same direction as the boundary line; 2. The output light according to claim 1, wherein the output light is parallel to the line and located between an outer peripheral line of the hollow portion of the capillary and a tangent line which is in contact with a half-side portion forming the reflection surface. 3. Optical waveguide type optical modulator with monitor. 2. The light guide with an output light monitor according to claim 1, wherein the non-monitor surface of the capillary is formed by cutting the other approximately half inward while leaving the reflective surface at the tip end surface of the capillary. 3. Waveguide optical modulator. The optical waveguide type optical modulator with an output light monitor according to claim 1, wherein the non-monitor surface of the capillary is a non-reflection surface that does not reflect the radiation mode light. The non-monitor surface of the capillary, wherein means for blocking reflection mode light reflected on the non-monitor surface is arranged between the non-monitor surface and the light receiving surface of the photoelectric conversion element. 2. An optical waveguide type optical modulator with an output light monitor according to item 1. 2. The optical waveguide type with an output light monitor according to claim 1, wherein a means for blocking the radiation mode light upstream of the non-monitor surface is provided in the capillary with respect to the non-monitor surface of the capillary. Light modulator.

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