JP2004317628A - Optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission module in which a surface light emitting type light emitting element, an optical fiber and a monitor light receiving element are provided, optical coupling efficiency to the fiber is high, no fluctuation in light beams that are made incident on the light receiving element, caused by temperature change exists, no breakage exists for bonding wires connected to the optical elements during handling and highly precise optical axis alignment is conducted without using high precision parts. <P>SOLUTION: An optical fiber 2 is stored in a mount 1 which is made of a transparent material. A surface light emitting type light emitting element 4 that is a one-side both electrode type, is mounted on a first side surface 1a to which a tip surface of the fiber 2 of the mount 1 is exposed. A one-side both electrode type monitor light receiving element 5 is mounted on a second side surface which is orthogonally crossed with the first side surface of the mount. A groove 6 is formed on a third side surface which is orthogonally crossed with the first and the second side surfaces of the mount. The groove 6 is tilted with an angle of 30 to 60 degrees relative to the longitudinal direction of the fiber 2 and has a depth that reaches the fiber 2. A material having a refractive index different from that of the fiber 2 is filled into the groove 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention includes a surface-emitting type light-emitting element, an optical fiber for guiding light emitted from the surface-emitting type light-emitting element, and a monitor light-receiving element for monitoring light emitted from the surface-emitting type light-emitting element. The present invention relates to an optical transmission module in which an optical output of a surface-emitting type light emitting element is controlled to be constant by an output signal from a light receiving element.
[0002]
[Prior art]
Conventionally, an optical transmission module of this type is disclosed in JP-A-2002-72025. This device divides outgoing light from the surface-emitting type light-emitting element by the spectral base, enters the monitor light-receiving element, feeds back a signal from the monitor light-receiving element to the integrated circuit for driving the surface-emitting type light-emitting element, The light output of the surface-emitting type light-emitting element is always controlled to be constant.
[0003]
However, this optical transmission module has a drawback that the light coupling efficiency to the optical fiber is low because the light emitted from the surface-emitting type light-emitting element is branched by the spectral base.
In addition, since the light emitting point and the radiation angle of the surface emitting light emitting element are small, the branching ratio is greatly affected by the mounting accuracy of the surface emitting light emitting element or the dimensional accuracy of the spectral base, so that high component accuracy and mounting accuracy are required. You.
Further, there is also a disadvantage that the branching ratio fluctuates due to deformation and expansion of the spectral base caused by a temperature change during operation.
[0004]
Further, in the optical transmission module disclosed in WO97 / 06458, light from a light emitting element that has propagated through an optical fiber is reflected by a light reflecting substrate disposed in a groove, and received by a light receiving element.
[0005]
However, in this optical transmission module, since the dielectric multilayer filter chip is inserted into the groove, the cost of the dielectric multilayer filter chip and the step of inserting the filter chip are required. Furthermore, in order to insert the filter chip, a groove having a width large enough for the thickness of the filter chip must be formed. If the width of the groove is narrow, it becomes difficult to insert the filter chip.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-072025 [Patent Document 2]
WO / 06458
[0007]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a surface emitting light emitting device, an optical fiber that guides light emitted from the surface emitting light emitting device, and a monitoring light receiving device that monitors light emitted from the surface emitting light emitting device. In the optical transmission module provided, the loss of light from the surface-emitting type light emitting element to the optical fiber is low, the light intensity incident on the monitoring light receiving element does not fluctuate due to a temperature change, the number of parts is small, and the manufacturing accompanying this is small. An object of the present invention is to provide an optical transmission module which has a small number of steps, has a simple structure, has good productivity, and can be downsized.
[0008]
[Means for Solving the Problems]
To solve this problem,
According to the first aspect of the present invention, an optical fiber is accommodated and fixed in a mount made of a transparent material, and a surface emitting type light emitting element is provided on the first side surface of the mount where the distal end surface of the optical fiber is exposed. The surface is mounted facing the optical fiber, and on a second side surface orthogonal to the first side surface of the mount, a single-sided dual-electrode monitoring light receiving element is mounted with the light receiving surface facing the mount. And a third side surface orthogonal to the first side surface and the second side surface of the mount, which is inclined at an angle of 30 to 60 degrees with respect to the longitudinal direction of the optical fiber, and has a depth of reaching the optical fiber. A groove is formed, and the groove is filled with a material having a refractive index different from the effective refractive index of the material forming the optical fiber, and a part of the light from the surface-emitting type light-emitting element guided by the optical fiber. Is filled with the material filled in the groove. It occurs panel reflecting, through the mount, an optical transmission module, characterized in that is adapted to be incident on the monitoring light-receiving element.
[0009]
According to a second aspect of the present invention, an electrode for mounting a surface-emitting type light emitting element is provided on the first side surface of the mount, and the electrode is in contact with the center of the light emitting portion of the surface emitting type light emitting element. The light emitting device according to claim 1, further comprising a pattern corresponding to an outer shape of the surface emitting light emitting device or a pattern corresponding to an alignment pattern of the surface emitting light emitting device such that the center of the fiber coincides with the center. An optical transmission module.
[0010]
According to a third aspect of the present invention, an electrode for mounting the monitor light receiving element is provided on the second side surface of the mount, and the electrode is provided between the center of the light receiving portion of the monitor light receiving element and the Fresnel reflected light. 2. The optical transmission module according to claim 1, wherein the optical transmission module has a pattern corresponding to the outer shape of the monitor light receiving element or a pattern corresponding to the alignment pattern of the monitor light receiving element so as to match the position of (b).
[0011]
The invention according to a fourth aspect is the optical transmission module according to the first aspect, wherein the tip end surface of the optical fiber is inclined with respect to the light emitting surface of the surface emitting type light emitting element.
According to a fifth aspect of the present invention, a driver integrated circuit is mounted on a mount, a signal from a monitor light receiving element is input to the driver integrated circuit, and the light output of the surface emitting type light emitting element is made constant. The optical transmission module according to claim 1, wherein:
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
FIG. 1 shows an example of the optical transmission module of the present invention. The optical transmission module of this example is schematically constituted by a mount 1. The mount 1 has a quadrangular prism shape in this example, but the mount 1 is not limited to this and any shape can be used.
[0013]
The material forming the mount 1 is a material that is transparent at least in the wavelength band used, and may be either an insulator or a semiconductor, and specific examples include quartz glass, crystallized glass, and heat-resistant glass.
[0014]
A circular through hole 3 for inserting and fixing the optical fiber 2 is formed inside the mount 1. In this example, the circular through hole 3 extends along the longitudinal direction of the mount 1, and the first side surface of the mount 1 is provided. It is formed so as to penetrate the center portion from 1a to the side surface 1d facing the side surface 1a. The number of the optical fibers 2 and the through holes 3 passing therethrough is not limited to one, and a plurality of the optical fibers 2 may be provided.
[0015]
Further, the first side surface 1a of the mount 1 faces the opening of the optical fiber 2 so as to expose the distal end surface of the optical fiber 2 inserted into the through hole 3. The tip surface of the optical fiber 2 may be parallel to a light emitting surface of the surface emitting light emitting element 4 described later, or may be inclined with respect to the light emitting surface of the surface emitting light emitting element 4. When the distal end surface of the optical fiber 2 is inclined, the light reflected on the distal end surface is less likely to return directly to the surface-emitting light emitting element 4, and the effect of the return light can be reduced. The optical fiber 2 and the mount 1 are joined with an adhesive 7.
In the present invention, instead of the through hole 3, a V-groove may be formed along the longitudinal direction, and the optical fiber may be accommodated and fixed in the V-groove.
[0016]
An electrode (not shown) is provided on the outer surface of the mount 1. This electrode is used for electrical connection and mechanical connection with the surface emitting light emitting element 4 and the monitor light receiving element 5 for mounting. In this example, the surface emitting light emitting element is provided on the first side surface 1a. Four electrodes are formed.
[0017]
The electrode for the surface-emitting light-emitting element 4 is arranged such that the center of the light-emitting portion of the surface-emitting light-emitting element 4 coincides with the center of the core of the optical fiber 2 fixed to the mount 1. It has a pattern that matches the outer shape or a pattern corresponding to the alignment pattern of the surface-emitting light-emitting element 4, and the electrode itself also serves as an index for alignment of the surface-emitting light-emitting element 4.
The pattern of the electrode is not limited to the one having the above-described alignment function, and may be a pattern that simply achieves electrical conduction and mechanical bonding.
[0018]
An electrode (not shown) for the monitor light receiving element 5 is provided on a second side surface 1b of the mount 1 orthogonal to the first side surface 1a.
The electrode for the monitor light receiving element 5 has a pattern or a pattern that matches the outer shape of the monitor light receiving element 5 so that the center of the light receiving portion of the monitor light receiving element 5 matches the position of the Fresnel reflected light as described later. The electrode has a pattern corresponding to the positioning pattern of the monitoring light receiving element 5, and the electrode itself also serves as an index for positioning the monitoring light receiving element 5.
In addition, the pattern of the electrode is not limited to the above-described pattern having the alignment function, and may be a pattern simply achieving electrical conduction and mechanical joining.
[0019]
Further, these electrodes are made of a conductive film having a thickness of 0.5 to 5 μm, and are preferably composed of two or more layers. It is made of a chemically active metal such as chromium, nickel, or titanium having good adhesion, and the uppermost layer is made of a noble metal such as gold or platinum, which is not deteriorated by oxidation and has low contact resistance. One or more layers made of another conductive material may be provided between the lowermost layer and the uppermost layer.
[0020]
A surface-emitting light emitting element 4 and a monitoring light receiving element 5 are mounted on each electrode of the first side surface 1a and the second side surface 1b of the mount 1. The surface-emitting type light emitting element 4 here includes a single-sided double-electrode type surface-emitting laser (VCSEL) having a light-emitting surface provided with both anode and cathode electrodes, and a double-sided double-electrode type surface-emitting laser. The monitoring light-receiving element 22 is a single-sided double-electrode photodiode having a light-receiving surface provided with both anode and cathode electrodes.
[0021]
The fixing of the optical elements 4 and 5 is performed, for example, as follows. First, a eutectic solder layer is provided in advance on the light receiving / emitting surfaces of the optical elements 4 and 5 or the electrodes by a thin film forming process such as vapor deposition and sputtering. The eutectic solder applied to the electrodes by screen printing or a dispenser is heated and pre-emulsified. The eutectic solder layer is formed by a method of forming a eutectic solder layer, a method of transferring a thin spread eutectic solder paste to the light receiving and emitting surfaces of the optical elements 4 and 5, or a method of arranging a eutectic solder preform on an electrode. I do.
[0022]
After the eutectic solder layer is provided in this manner, the optical elements 4 and 5 are aligned and placed on the electrodes, and then heated to melt the eutectic solder layer, cooled, and fixed.
As another fixing method, gold bumps may be provided on the light receiving / emitting surfaces or the electrodes of the optical elements 4 and 5 and fixed by heating, load pressing, scrubbing, or a combination thereof.
[0023]
By fixing the surface emitting light emitting element 4 and the monitoring light receiving element 5, electrical connection between both electrodes on the light receiving and emitting surface side of the optical elements 4 and 5 and the electrode provided on the mount 1 is simultaneously performed. .
Further, the alignment of the optical elements 4 and 5 can be easily performed by using the outer shape or the alignment pattern of the optical elements 4 and 5 and the pattern formed on the electrode.
[0024]
A groove 6 is formed on a third side surface 1c of the mount 1 which is orthogonal to the first side surface 1a and also orthogonal to the second side surface 1b. The groove 6 has a width of 10 to 100 μm and a linear shape having a depth reaching at least the clad of the optical fiber 2 fixed to the through hole 3 of the mount 1. The position where the groove 5 is formed is determined so that Fresnel reflected light by the material filling the groove 6 described later efficiently enters the monitoring light receiving element 5, and usually, an intersection where the groove 6 and the optical fiber 2 intersect with each other. Is set immediately below the monitoring light receiving element 5.
[0025]
Further, the groove 6 is inclined at an inclination angle of 30 to 60 degrees, preferably 40 to 50 degrees, with respect to the longitudinal direction of the optical fiber 2. The inclination angle is determined so that the Fresnel reflected light from the groove 6 is efficiently incident on the monitoring light receiving element 5, and if the angle is outside the above range, the light receiving sensitivity of the monitoring light receiving element 5 deteriorates. Lack of practicality.
[0026]
The inside of the groove 6 is made of a material forming the optical fiber 2, for example, a material having a refractive index n2 different from the refractive index n1 such as quartz or PMMA, and n1 / n2 ≦ 0.95 or n1 / n2 ≧ 1. 05, preferably a material satisfying n1 / n2 ≦ 0.9 or n1 / n2 ≧ 1.1, for example, a liquid resin such as an epoxy resin or an ultraviolet curable resin is filled and solidified.
At this time, the reflectance R on one side of the groove is
R = ((n1-n2) / (n1 + n2)) ^{2
It becomes.}
The groove 6 is formed by mounting the surface-emitting light emitting element 4 and the monitoring light receiving element 5 on the mount 1 and then using a dicing saw, a precision slicer, or the like.
[0027]
In such an optical transmission module, light emitted from the surface emitting light emitting element 4 is incident on the distal end surface of the optical fiber 2 and is guided. Part of the light guided into the optical fiber 2 is filled in the cladding of the optical fiber 2 and the groove 6 because the refractive index of the material filling the groove 6 and the refractive index of the glass forming the optical fiber 2 are different. Fresnel reflection occurs at the interface with the material, and the reflected light passes through the mount 1 and travels in the direction of the second side surface 1b of the mount 1 according to Fresnel's law.
[0028]
This reflected light is received by the monitoring light receiving element 5 mounted on the second side surface 1b, and the output light of the surface emitting light emitting element 4 is monitored. The output from the monitor light-receiving element 4 is fed back to the driver integrated circuit of the surface-emitting light-emitting element 4 so that the intensity of light emitted from the surface-emitting light-emitting element 4 is kept constant.
[0029]
In such an optical transmission module, a surface emitting laser which can be obtained at a low cost as the surface emitting light emitting element 4 and a photodiode or the like can be used as the light receiving element 5 for monitoring, so that it can be manufactured at low cost. Further, since the driver integrated circuit can be mounted on the mount 1, the entire module can be reduced in size.
[0030]
Further, a part of light guided to the optical fiber 2 from the surface emitting light emitting element 21 mounted on the first side surface 1 a of the mount 1 is Fresnel-reflected by the material filled in the groove 6, and Since the light is incident on the monitor light receiving element 5 mounted on the second side surface 1b, no special light splitting means such as a spectroscopic substrate is required, the structure is simple, and the monitor light receiving element 5 is changed due to a temperature change or the like. The input light quantity does not change.
[0031]
When the surface-emitting type light-emitting element 4 and the monitor light-receiving element 5 are fixed to the mount 1, by using a flip-chip bonder or the like, the electrodes are used as an index for alignment, and then the alignment is performed with high accuracy. Therefore, an optical transmission module with high coupling efficiency can be obtained.
[0032]
Furthermore, since the single-sided and dual-electrode surface-emitting light-emitting element 4 and the monitoring light-receiving element 5 are used, there is no need to use a bonding wire for connection between the electrodes. The bonding wire will not be damaged in later handling.
[0033]
In the present invention, an array-type light emitting element and a monitoring light receiving element can be used as the surface emitting light emitting element and the monitoring light receiving element, whereby the transmission capacity can be increased. Further, as shown in FIG. 2, the driving element 8 of the surface-emitting type light emitting element 4 can be mounted on the mount 1, so that the size of the optical transmission module can be reduced, and the noise can be reduced in a high frequency band.
Further, in the above-described example, an example in which a single-sided, dual-electrode surface-emitting light emitting element is mounted is shown, but a double-sided, dual-electrode surface-emitting light emitting element using a submount may be used.
[0034]
In the above-described example, the surface-emitting light-emitting element having both electrodes on one side is mounted. However, a normal surface-emitting light-emitting element (a surface having an anode on one side and a cathode on the backside) is formed using a submount. (A light emitting element).
[0035]
Further, as shown in FIG. 3, a thin plate 9 made of a transparent material having a refractive index np different from the effective refractive index neff of the optical fiber is inserted into the groove 6 having a depth reaching the optical fiber 2, and A liquid resin having a refractive index nr substantially equal to the refractive index may be filled and cured by heating or irradiation with ultraviolet rays.
[0036]
This requires a step of inserting the thin plate 9 as compared with the case where only the resin is filled in the groove 6, but the selection range of the material is widened, and the reflection at the interface between the resin and the thin plate 9 becomes main. In addition, it is possible to prevent the influence of the multiple reflection between the optical fiber 2 end face and the resin.
[0037]
Materials in this example include nr / np ≦ 0.95 or nr / np ≧ 1.05, preferably nr / np ≦ 0.9 or nr / np ≧ 1.1, and 0.9 ≦ neff / A combination of materials satisfying nr ≦ 1.1, preferably 0.95 ≦ neff / nr ≦ 1.05, more preferably 0.98 ≦ neff / nr ≦ 1.02 is preferable. Further, by setting the combination of nr <neff <np, the reflectance on the surface of the thin plate 9 increases.
[0038]
【The invention's effect】
As described above, according to the optical transmission module of the present invention, the Fresnel reflection is used without using a filter as a part of reflecting the light of the surface emitting type light emitting element to the monitor light receiving element. This eliminates the need for an expensive dielectric multilayer filter chip and a step of inserting the same into the groove, thus facilitating fabrication. In addition, since there is no wavelength dependency, it is effective for various wavelengths. That is, the wavelength can be shared for the transparent region of the mount material. Further, no special light-splitting means such as a light-splitting substrate is required, the structure is simple, and the amount of light input to the monitoring light-receiving element does not change due to a temperature change or the like.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of an optical transmission module of the present invention.
FIG. 2 is a schematic configuration diagram showing another example of the optical transmission module of the present invention.
FIG. 3 is a schematic configuration diagram showing another example of the optical transmission module of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mount, 1a ... 1st side, 1b ... 2nd side, 1c ... 3rd side, 2 ... Optical fiber, 3 ... Through-hole, 4 ...・ Surface emitting type light emitting element, 5 ... monitoring light receiving element, 6 ... groove.

Claims (5)

An optical fiber is housed and fixed in a mount made of a transparent material, and a surface emitting type light emitting element is mounted on the first side surface of the mount where the tip end surface of the optical fiber is exposed, with its light emitting surface facing the optical fiber. On a second side surface orthogonal to the first side surface of the mount, a single-sided double-electrode monitoring light receiving element is mounted with its light receiving surface facing the mount. On a third side surface orthogonal to the side surface and the second side surface, a groove is formed which is inclined at an angle of 30 to 60 degrees with respect to the longitudinal direction of the optical fiber and has a depth reaching the optical fiber. Is filled with a material having a refractive index different from the effective refractive index of the material forming the optical fiber, and a part of the light from the surface-emitting type light emitting element guided to the optical fiber is filled in the groove. Fresnel reflection occurs depending on the material, Optical transmission module, characterized in that through the bets, and is incident on the monitoring light-receiving element. An electrode for mounting the surface emitting light emitting element is provided on the first side surface of the mount, and this electrode matches the center of the light emitting portion of the surface emitting light emitting element with the center of the core of the optical fiber. The optical transmission module according to claim 1, wherein the optical transmission module has a pattern corresponding to an outer shape of the surface emitting light emitting device or a pattern corresponding to an alignment pattern of the surface emitting light emitting device. On the second side of the mount, an electrode for mounting the monitor light receiving element is provided, and this electrode is aligned with the center of the light receiving section of the monitor light receiving element and the position of the Fresnel reflected light. 2. The optical transmission module according to claim 1, wherein the optical transmission module has a pattern corresponding to an outer shape of the monitor light receiving element or a pattern corresponding to an alignment pattern of the monitor light receiving element. The optical transmission module according to claim 1, wherein a tip end surface of the optical fiber is inclined with respect to a light emitting surface of the surface emitting type light emitting element. A driver integrated circuit is mounted on the mount, a signal from the monitor light receiving element is input to the driver integrated circuit, and the light output of the surface emitting type light emitting element is made constant. 2. The optical transmission module according to 1.

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