JP4263506B2 - Manufacturing method of optical fiber array - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an optical fiber array having a mode conversion section and the like by forming a refractive index increasing region in an optical fiber core near an optical junction.
[0002]
[Prior art]
An optical fiber array has a plurality of optical fibers arranged on a substrate at an accurate pitch, and is applied as an optical junction with a semiconductor laser or an optical waveguide component.
[0003]
FIG. 6 shows a schematic perspective view of the optical fiber array. The optical fiber array includes a fixing member 24 subjected to high-precision V-groove processing, a bare optical fiber 22 drawn from the optical fiber tape core wire 25 and arranged in alignment on the V-groove, and a pressing member 21 for pressing the bare optical fiber 22. The adhesive 23 is filled in the gap.
When manufacturing an optical fiber array, first, the bare optical fibers 22 are arranged on the fixing member 24, pressed by the pressing member 21 from above, filled with the adhesive 23 in the gap, and cured and integrated. is there. After the bonding, the connection end face is polished obliquely so as to have an angle of 8 °, for example.
[0004]
FIG. 7 is a cross-sectional view of a portion surrounded by a line segment DD ′ and a line segment EE ′ in FIG. In such an optical fiber array, the end surface on the line DD ′ side becomes a connection end surface when connecting to another optical waveguide component or the like. The end surface on the side of the line segment DD ′ is an inclined surface having an inclination angle α of about 8 ° with respect to the vertical direction of the upper surface of the pressing member 21, and part of the signal light is bare. It is prevented from being reflected on the end face of the optical fiber 22 and propagating to the transmitting side.
[0005]
In recent years, optical waveguide components that are miniaturized and highly integrated by increasing the refractive index of the core have been widely used. Such optical waveguide components and normally used single mode fibers have different relative refractive index differences and different core diameters, so that the mode field diameters are different. For this reason, when an optical fiber is connected to an optical waveguide component, a connection loss occurs due to a difference in mode field diameter.
[0006]
Therefore, in order to suppress problems caused by the difference in mode field diameter, it is necessary to form a mode conversion portion at the joint portion of the optical fiber.
The mode conversion part is the relative refractive index difference between the core and the clad and the core diameter are adjusted so that the mode field diameter at the connection part is equivalent to that of the optical waveguide component to be connected. The difference and the core diameter are formed so as to gradually change in the light propagation direction and become the value of the optical fiber. Thereby, when connecting to the optical waveguide component, the connection loss caused by the difference in the mode field diameter can be reduced.
[0007]
For example, a method of forming a refractive index increasing region by focusing and irradiating a femtosecond pulse laser inside a transparent material such as glass has been disclosed (see Patent Document 1).
Using this method, a femtosecond pulse laser is incident from one end of the core of the optical waveguide component, and the refractive index on one end side is high. From this one end side, the light is gradually refracted along the light propagation direction of the core. There has been proposed a method of manufacturing an optical waveguide component that forms a refractive index gradient such that the refractive index decreases and becomes the refractive index of the core, and serves as a mode converter (see Patent Document 2).
In addition, a method of manufacturing an optical waveguide component in which a femtosecond pulse laser is focused and irradiated from the side of the core to form a mode conversion unit has been proposed (see Japanese Patent Application No. 2002-247404).
[0008]
However, in the case of forming a mode conversion unit or the like using the method proposed in Patent Documents 1 and 2 and Japanese Patent Application No. 2002-247404 described above for the optical fiber arrays shown in FIGS. As shown, there is a problem that a desired refractive index increase region cannot be formed for the bare optical fiber 22.
[0009]
FIG. 8A shows a case where the end face of the optical fiber faces the side opposite to the incident side of the femtosecond pulse laser, and the end face is focused and irradiated with the femtosecond pulse laser using the objective lens. Indicates. In such a case, if the focal point 33 of the femtosecond pulse laser is accidentally brought too close to the surface of the end face 34a of the optical fiber, ablation occurs, and the glass near the surface of the end face 34a of the optical fiber blows away. A dimple is formed and the connection loss increases.
[0010]
FIG. 8B shows a state where the end face of the optical fiber faces the incident side of the femtosecond pulse laser and the optical fiber is focused and irradiated with the femtosecond pulse laser. The femtosecond pulse laser 42b is refracted in the optical fiber 44 as it passes through the optical fiber 44, as shown in FIG. 8 (b) (ii). For this reason, normally, when the femtosecond pulse laser 42b is focused and irradiated, the position in the depth direction of the focal point 43b of the femtosecond pulse laser is adjusted in consideration of the influence of refraction by the optical fiber 44.
[0011]
FIGS. 8B and 8I show a state where the condensing point 43a of the femtosecond pulse laser is focused and irradiated with the femtosecond pulse laser 42a in the vicinity of the end face 44a of the optical fiber. At this time, since the femtosecond pulse laser 42a does not pass through the optical fiber 44, the femtosecond pulse laser 42a is not refracted by the optical fiber 44, and the position of the condensing point 43a in the depth direction changes.
Thus, when the condensing point 43a of the femtosecond pulse laser is scanned, the position of the condensing point 43a in the depth direction fluctuates, so that the refractive index increasing region is shifted from the center of the core of the optical fiber 44. 8b or (i), the femtosecond pulse laser 42a is not focused in the optical fiber 44, and a refractive index increasing region cannot be formed in the core of the optical fiber 44. Occurs.
[0012]
In order to solve this problem, there is a method of scanning the condensing points 43a and 43b while adjusting the positions of the condensing points 43a and 43b of the femtosecond pulse laser in the depth direction. It is difficult to estimate the fluctuation amount of the position of the condensing points 43a and 43b in the depth direction from the surface state and the inclination angle of the connection end surface 44a, and the position is adjusted accurately in the depth direction of the condensing points 43a and 43b. The current situation is not done. Therefore, it cannot be processed continuously from the inside of the optical fiber 44 to one end surface, or ablation is caused in the end surface 44a portion.
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-311237 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-182045
[Problems to be solved by the invention]
Therefore, the object of the present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a method for manufacturing an optical fiber array in which a refractive index increasing region such as a mode conversion unit capable of optical coupling with low loss can be formed accurately and easily.
[0015]
[Means for Solving the Problems]
In order to solve this problem, in the invention according to claim 1, the optical fiber is fixed to a fixing member, and a femtosecond pulse laser is condensed and irradiated to one end of the optical fiber to form a refractive index increasing region. An optical fiber array manufacturing method is characterized in that an end surface of one end portion of the optical fiber in which the refractive index increasing region is formed later is an inclined surface.
[0016]
According to a second aspect of the present invention, the optical fiber is fixed to a fixing member after the femtosecond pulse laser is focused and irradiated on one end portion of the optical fiber, and the refractive index increasing region is fixed. An optical fiber array manufacturing method is characterized in that an end face of one end of an optical fiber formed with an inclined surface is an inclined surface.
[0017]
The invention according to claim 3 is characterized in that a rectangular pressing member is provided above the optical fiber, and the optical fiber is fixed to the fixing member. Is the method.
[0018]
The invention according to claim 4 is characterized in that a femtosecond pulse laser is focused and irradiated from above the optical fiber to form a refractive index increasing region. It is a manufacturing method.
[0019]
The invention according to claim 5 is characterized in that the fixing member is a V-groove substrate having a plurality of V-grooves, and an optical fiber is fixed to each of the V-grooves. The manufacturing method of the optical fiber array of description.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the optical fiber array manufacturing method of this embodiment, first, a bare optical fiber is fixed to a fixing member, and a refractive index increasing region is formed at one end of the bare optical fiber.
FIG. 1 is a perspective view of an optical fiber array in a state where optical fibers are fixed to a fixing member. Reference numeral 4 denotes a fixing member. The fixing member 4 is made of rectangular quartz glass in which a slightly thicker front part and a slightly thinner rear part are integrated, and has a plurality of V grooves on the upper surface. Is. The V-groove accommodates the bare optical fiber 2 drawn from the optical fiber ribbons 5 and 5 and is fixed by the optical adhesive 3.
[0021]
A pressing member 1 made of rectangular quartz glass is provided above the bare optical fiber 2, and the bare optical fiber 2 and the pressing member 1 are fixed by an optical adhesive 3. The bare optical fibers 2 are arranged in parallel at equal intervals by the V-groove, and are fixed by the V-groove and the pressing member 1.
Here, the optical fiber ribbon 5 is a bare optical fiber 2 coated with a coating resin 6, and the bare optical fiber 2 is a silica-based optical fiber including a core 8 and a clad 7.
[0022]
FIG. 2 is a cross-sectional view of a portion surrounded by a line segment AA ′ and a line segment BB ′ in FIG. As a method of fixing the bare optical fiber 2 to the fixing member 4, a slightly thicker front part and a slightly thinner rear part are integrated, and a rectangular groove having V-grooves provided at desired intervals in this front part. A fixing member 4 having a shape is prepared, and the bare optical fiber 2 is arranged in each V groove of the fixing member 4, and the tip portion of the tape core wire 5 is pressed against the step between the thick portion and the thinner portion. Arrange as follows. Further, a pressing member 1 is provided above the bare optical fiber 2 and the gap is filled with the optical adhesive 3 and bonded.
[0023]
FIG. 3 is a schematic configuration diagram showing an example of a manufacturing apparatus used in the method of manufacturing an optical waveguide component according to this embodiment. Reference numeral 11 denotes a laser device using a titanium sapphire laser or the like. In this embodiment, the laser device 11 is controlled to emit a femtosecond pulse laser 13 having a center wavelength of 800 nm, a pulse width of 200 fs, and a repetition frequency of 200 kHz.
In addition, an ND filter 12 is installed so as to face the laser emission port of the laser device 11, and the average output of the femtosecond pulse laser 13 emitted from the laser device 11 can be adjusted.
[0024]
A mirror 14 is installed on the path of the femtosecond pulse laser 13 that has passed through the ND filter 12, and the traveling path of the femtosecond pulse laser 13 can be adjusted. The objective lens 16 focuses the femtosecond pulse laser 13 whose traveling path is adjusted by the mirror 14.
[0025]
Behind this mirror 14 is a CCD camera 15 or the like for observing markings for alignment (not shown) and visible light included during light emission generated near the condensing point 17 of the femtosecond pulse laser. Can be monitored.
The optical fiber array 10 with the bare optical fiber 2 fixed to the fixing member 4 is fixed to the XYZ stage 18. By moving the XYZ stage 18 in any direction of the X, Y, and Z directions, the condensing point 17 can be precisely moved inside the optical fiber.
[0026]
In this optical waveguide component manufacturing apparatus, the femtosecond pulse laser 13 emitted from the laser device 11 passes through the ND filter 12, is reflected by the mirror 14, and is further collected by the objective lens 16, and is optical fiber array. Irradiated into the core 8 of 10 bare optical fibers 2.
[0027]
As a method of condensing and irradiating the femtosecond pulse laser 13 to a desired position inside the core 8, as shown in Japanese Patent Application No. 2002-81927, the femtosecond pulse laser 13 is condensing and irradiated on the upper surface of the holding member 1 to obtain an ablation mark. And this ablation mark is used as a reference position. Then, considering the fact that the depth of the actual focusing point 17 varies due to the refraction of the femtosecond pulse laser 13 inside the holding member 1 and the bare optical fiber 2, the position of the focusing point 17 in the depth direction is considered. And the femtosecond pulse laser 13 is focused and irradiated to a desired depth inside the bare optical fiber 2.
[0028]
Then, as described in Japanese Patent Application No. 2002-247404, a refractive index increasing region is formed in the core 8 of the bare optical fiber 2. First, the position of the end face 8a of the bare optical fiber is confirmed so that the focal point 17 of the femtosecond pulse laser comes.
[0029]
Next, with the laser device 11 fixed, the XYZ stage 18 is driven at a constant acceleration along the longitudinal direction of the optical fiber, so that the condensing point 17 is relatively moved inside the fiber core 8 and is bare. A refractive index increasing region is formed from the end face 8a of the optical fiber toward the inside.
FIG. 4 shows an example of the relationship between the amount of increase in the refractive index of the portion irradiated with the femtosecond pulse laser 13 and the scanning speed of the XYZ stage 18. It can be seen that the faster the scanning speed of the XYZ stage 18, the smaller the number of induced refractive index changes because the number of irradiations of the femtosecond pulse laser 13 per unit area decreases. Accordingly, when the XYZ stage 18 is scanned at a constant acceleration, the relative refractive index difference gradually decreases from the end face 8a of the bare optical fiber toward the inside, and becomes sufficiently close to the relative refractive index difference of the core 8. Actually, considering that some parts may be removed by the subsequent polishing process, the XYZ stage 18 is first moved at an acceleration of 0, that is, at a constant scanning speed, so that a region where the relative refractive index difference is constant is desired. A region where the relative refractive index difference continuously changes is formed by changing the acceleration from the middle.
[0030]
FIG. 5 is a cross-sectional view showing a state in which an end surface of the optical fiber array in which the refractive index increasing region is formed in the core of the optical fiber is an inclined surface. Reference numeral 8b denotes a formed refractive index increasing region.
As described above, after the refractive index increasing region 8b is formed at one end of the bare optical fiber 2 that is the core 8 in the vicinity of the end face 8a, the pressing member 1 and the fixing member 4 together with the end face 8a of the bare optical fiber. Also polish the sides. And as shown by line segment CC 'in FIG. 5, it is set as the inclined surface which has an inclination | tilt angle of about 8 degrees with respect to the orthogonal | vertical direction of the upper surface of the pressing member 1. FIG.
[0031]
In this embodiment, the core 8 at one end of the bare optical fiber 2 is focused and irradiated with the femtosecond pulse laser 13 to form the refractive index increasing region 8b, and then the naked light in which the refractive index increasing region 8b is formed. The end surface 8a of the fiber is an inclined surface. For this reason, when the femtosecond pulse laser 13 is focused and irradiated, the end face 8a of the bare optical fiber can be a plane perpendicular to the side face of the bare optical fiber 2, not an inclined face.
[0032]
As a result, as described in the prior art, the condensing point 17 of the femtosecond pulse laser is set to the bare optical fiber as in the case where the refractive index increasing region 8b is formed in the bare optical fiber 2 whose end face 8a is an inclined surface. When scanning from the vicinity of the end face 8a, the position of the condensing point 17 in the depth direction does not change, and in this embodiment, a desired refractive index increasing region 8b can be formed, and light connection loss can be reduced.
[0033]
Further, a rectangular pressing member 1 is provided above the bare optical fiber 2, and a femtosecond pulse laser 13 is focused and irradiated from the pressing member 1 side. For this reason, compared with the case where the femtosecond pulse laser 13 is focused and irradiated directly on the side surface of the cylindrical bare optical fiber 2, the upper surface of the pressing member 1 is flat, and it is easy to determine the target position of irradiation. Excellent in properties.
Furthermore, since the femtosecond pulse laser 13 is focused and irradiated via the pressing member 1, no ablation trace remains on the surface of the side surface of the bare optical fiber 2. For this reason, strength deterioration due to ablation formation can be suppressed.
[0034]
The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, as a method of condensing and irradiating the femtosecond pulse laser 13 to a desired position inside the core 8, as shown in Japanese Patent Application No. 2002-54455, the core is obtained by condensing the femtosecond pulse laser 13 by the CCD camera 15. It is also possible to monitor the light emission generated inside 8 and determine the focused irradiation position so that the light emission is guided with the maximum amount of light in the light propagation direction inside the core 8.
[0035]
Further, the condensing point 17 may be scanned a plurality of times. By refocusing and irradiating the femtosecond pulse laser 13 with the femtosecond pulse laser 13, it is possible to induce a refractive index change in the core 8 again. By increasing the number of scans, the refractive index of the core 8 can be increased. For this reason, by performing a desired number of scans, the refractive index increasing region 8b can be formed with the refractive index of the core 8 as a desired value.
[0036]
The refractive index increasing region 8b may be one that has been subjected to refractive index modulation at a constant period, such as an optical fiber grating, in addition to the above. Further, the refractive index increasing region may be provided not only in the core 8 but also in the clad 7.
[0037]
Further, the bare optical fiber 2 may be fixed to the fixing member 4 after the femtosecond pulse laser 13 is focused and irradiated on one end of the bare optical fiber 2 to form the refractive index increasing region 8b.
[0038]
【The invention's effect】
As described above in detail, according to the first and second aspects of the present invention, after forming a refractive index increasing region by condensing and irradiating the femtosecond pulse laser to one end of the optical fiber, this refraction is performed. The end surface of the optical fiber in which the rate increasing region is formed is defined as an inclined surface. For this reason, when the femtosecond pulse laser is focused and irradiated, the end face of the optical fiber can be a plane perpendicular to the side face, not an inclined face.
As a result, when the focal point of the femtosecond pulse laser is scanned from the vicinity of the end face of the optical fiber, the position of the focal point in the depth direction does not change, and a desired refractive index increasing region can be formed. Connection loss can be reduced.
[0039]
Further, in the invention according to claim 3, the upper surface of the pressing member is flat compared to the case where the side surface of the cylindrical optical fiber is focused and irradiated with the femtosecond pulse laser, and the target position of irradiation can be easily determined. Optical waveguide parts can be manufactured with excellent workability.
Furthermore, since the femtosecond pulse laser is focused and irradiated via the pressing member, no ablation trace remains on the surface of the side surface of the optical fiber. For this reason, strength deterioration due to ablation formation can be suppressed.
[0040]
Further, in the invention according to claim 4, for example, when the femtosecond pulse laser is focused and irradiated only from the end face of the optical fiber, no ablation trace remains on the surface of the end face of the optical fiber. It is possible to reduce the connection loss at the end surface that is the connection surface with the waveguide component.
[0041]
Furthermore, in the invention according to claim 5, the fixing member is a V-groove substrate having a plurality of V-grooves, and an optical fiber is fixed to each of the V-grooves. Thus, it can be easily arranged at a desired position.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example of an optical fiber array before forming a refractive index increasing region.
2 is a schematic cross-sectional view showing a portion surrounded by a line segment AA ′ and a line segment BB ′ in FIG. 1; FIG.
FIG. 3 is a schematic configuration diagram showing an example of a manufacturing apparatus used in the method of manufacturing an optical waveguide component according to the present embodiment.
FIG. 4 is a diagram illustrating an example of a relationship between a refractive index increase amount of a portion irradiated with a femtosecond pulse laser and a scanning speed of an XYZ stage.
FIG. 5 is a schematic cross-sectional view showing an optical fiber array having an inclined end surface at one end where a refractive index increasing region is formed.
FIG. 6 is a schematic perspective view showing an optical fiber array.
7 is a schematic cross-sectional view showing a portion surrounded by a line segment DD ′ and a line segment EE ′ in FIG. 6;
FIG. 8 is a schematic cross-sectional view showing a state in which a femtosecond pulse laser 32 is focused and irradiated on a connection end face of an optical fiber.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Holding member, 2 ... Optical fiber, 4 ... Fixing member, 8a ... End surface of optical fiber, 8b ... Refractive index increase area | region used as mode conversion part, 13 ... Femto Second pulse laser

Claims (5)

After fixing the optical fiber to the fixing member, condensing and irradiating a femtosecond pulse laser at one end of the optical fiber, and forming a refractive index increasing region,
An optical fiber array manufacturing method, wherein an end surface of one end of an optical fiber in which the refractive index increasing region is formed is an inclined surface. After focusing and irradiating a femtosecond pulse laser to one end of the optical fiber to form a refractive index increase region, the optical fiber is fixed to a fixing member,
An optical fiber array manufacturing method, wherein an end surface of one end of an optical fiber in which the refractive index increasing region is formed is an inclined surface. 3. The method of manufacturing an optical fiber array according to claim 1, wherein a rectangular pressing member is provided above the optical fiber, and the optical fiber is fixed to the fixing member. 4. The method of manufacturing an optical fiber array according to claim 1, wherein the refractive index increasing region is formed by focusing and irradiating a femtosecond pulse laser from above the optical fiber. The fixing member is a V-groove substrate having a plurality of V-grooves;
5. The method of manufacturing an optical fiber array according to claim 1, wherein an optical fiber is fixed to each of the V grooves.

Images