WO2004057396A1

WO2004057396A1 - Optical device

Info

Publication number: WO2004057396A1
Application number: PCT/JP2003/016348
Authority: WO
Inventors: Masashi Fukuyama; Yasunori Iwasaki; Akiyoshi Ide
Original assignee: Ngk Insulators, Ltd.
Priority date: 2002-12-20
Filing date: 2003-12-19
Publication date: 2004-07-08
Also published as: JPWO2004057396A1

Abstract

An optical device (10) comprises an optical fiber (15) having a core (40) and a cladding (42), a slit (18) extending from the upper surface of the optical fiber (15) to a glass substrate (12), a filter member (20) inserted in the slit (18), and a PD array (28) for detecting branch light (24). And a first polymer gel material (50) is filled in a clearance in the slit (18) between the slit (18) and a filter member (20). A second polymer gel material (52) is interposed between an optical fiber array (16) and the PD array (28) and placed in an optical path for the light (24) branched at the filter member (20).

Description

Description Optical Device Technical Field

The present invention relates to an optical fiber array having one or more optical fibers, or an optical device having one or more optical waveguides, and is particularly suitable for monitoring signal light propagating through these optical transmission means on the way. Optical devices. Background art

In current optical communication technology, monitoring technology of communication quality is an important item. Above all, monitoring of optical output occupies an important position, especially in the field of wavelength division multiplexing communication technology.

In recent years, there has been a growing demand for miniaturization, high performance, and low cost for such optical output monitoring technology.

Conventionally, a technique as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-264954 has been proposed. In this technique, an optical fiber is placed in a V-groove of a glass substrate, and then a parallel groove is formed so as to obliquely cross the optical fiber (with respect to its optical axis) with respect to the glass substrate. Then, a light reflecting substrate (optical member) is inserted into the parallel groove, and the gap is filled with an ultraviolet curable resin (adhesive).

Thus, of the signal light propagating through the optical fiber, the light component (reflected light) reflected by the light reflecting substrate is extracted out of the clad. Therefore, the signal light can be monitored by detecting the reflected light with, for example, a light receiving element.

By the way, when connecting an optical path such as an optical fiber with low loss, a resin for connecting an optical fiber or a refractive index matching material is used.

Generally, a resin having a Young's modulus of several MPa to several GPa is selected and used for fixing an optical fiber at a certain position. Therefore, when a resin for optical fiber connection is used as the resin to be filled in the parallel groove, In such a case, such a hard resin having a large Young's modulus is filled in a parallel groove having a width of about 10 m, so that an excessive stress is generated, which may cause a problem in reliability, for example. is there.

In addition, when a refractive index matching material is used as a resin to be filled in the parallel groove, generally, such a refractive index matching material is in a low-viscosity liquid state. This may make it difficult and reduce the yield.

The present invention has been made in consideration of such problems, and has as its object to provide an optical device capable of improving the reliability of a signal light monitoring function and improving the yield. . Disclosure of the invention

An optical device according to the present invention includes: a slit provided in a light transmitting means; a filter member inserted into the slit, for branching a part of light propagating through the light transmitting means; and a filler filled in the slit. And a gel material having a light transmitting ability. Examples of the light transmission means include an optical fiber and an optical waveguide.

Here, it is preferable to use a polymer gel material as the gel material. The polymer gel material refers to a low stress polymer or resin material having a Young's modulus of less than IMPa in a gel state. The gel state refers to a state in which colloid particles and polymer solutes have lost their independent motility due to interaction and have gathered together, and have solidified. Gel that solidifies while containing the dispersion medium is called jelly. In a narrow sense, gel refers to jelly. In contrast, the state in which colloid particles are dispersed in a liquid and exhibit fluidity is called sol, and the solidification of sol is called gelation.

As described above, the gel material has a very low Young's modulus. Therefore, even if the slit is filled with a gel material, no excessive stress is generated due to, for example, thermal fluctuation. That is, the temperature characteristics are improved, which leads to an improvement in the reliability of the signal light monitoring function. The gel state is a state generally located between a liquid and a solid, as described above. Therefore, even if the slit is filled with a gel material, there is no problem that it is difficult to maintain the shape due to fluidity generated when a liquid is used. This leads to higher yields. To

The gel material preferably has a refractive index of 1.41 to 1.48. This generally indicates that the refractive index of the light transmission means such as an optical waveguide or an optical fiber is 1.44, and that a material close to this is used. In particular, when the slit is formed obliquely with respect to the optical axis, if the refractive index of the filling material in the slit deviates more than ± 0.04 from the refractive index of the light transmitting means, the light transmitting means and the An etalon effect (multiple interference) may occur between the filter and the filter member, and the monitoring function and signal light propagation characteristics may be significantly reduced. However, when the refractive index of the gel material is set to 1.41 to 1.48, even if the slit is formed obliquely with respect to the optical axis, the etalon effect described above is reduced, and the monitoring function is reduced. Also, it is possible to suppress the deterioration of the propagation characteristics of the signal light.

The gel material is preferably made of a silicone-based material. Silicone has the advantage that it is easy to match the refractive index of the light transmission means. In addition, silicone-based materials generally have low moisture retention properties, and in particular, have the advantage that the refractive index does not easily change due to humidity.

In the configuration, an optical element is arranged at least on an optical path of light branched by the filter member, outside the light transmitting means, between the light transmitting means and the optical element, and A gel material may be interposed on the optical path of the light split by the filter member.

When an optical element is installed on the light transmitting means, if a filler or an adhesive having a large Young's modulus is used between the light transmitting means and the optical element, the surface of the optical element may be damaged or excessive stress may be applied. The occurrence may cause a problem such as an optical axis shift of reflected light or signal light. From this, the problem described above can be avoided by interposing a gel material between the light transmitting means and the optical element as in the above configuration. Here, the optical element is, for example, a PD (Photodiode). Further, an optical fiber or an optical waveguide may be provided. Further, the gel material filled in the slit of the light transmitting means and the gel material interposed between the light transmitting means and the optical element are made of the same material, so that the transmission due to the difference in refractive index is achieved. This is advantageous for improving the characteristics such as reducing the polarization dependence (PDL) of light. The width of the slit is preferably 15 to 50 m. If the width is too narrow, it may be difficult to insert the filter member into the slit.If the width is too wide, the insertion loss may increase, and the attenuation of the signal light may increase. .

The angle of the slit with respect to the reference plane is preferably 15 ° to 25 °. If the angle is too small, the spread of the branch light from the filter member becomes too large, and crosstalk may be deteriorated when applied to multiple channels. On the other hand, if the angle is too large, the polarization dependence of the split light from the filter member increases, which may lead to deterioration of characteristics.

The filter member can be configured to include a quartz substrate and a multilayer film formed on a main surface of the quartz substrate. Here, for example, a polymer material (polyimide or the like) may be used as the substrate material. When polyimide or the like is used, a large warp may occur due to generation of stress by the multilayer film. Therefore, it is preferable to use a transparent inorganic material having a large elastic coefficient such as quartz. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing the optical device according to the present embodiment as viewed from the front. FIG. 2 is a cross-sectional view showing the optical device according to the present embodiment as viewed from the side. FIG. 3 is an enlarged view showing a branch portion of the optical device according to the present embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment in which the optical device according to the present invention is applied to, for example, a 4ch in-line power monitor module will be described below with reference to FIGS.

As shown in FIG. 1, the optical device 10 according to the present embodiment includes a glass substrate 12 and a plurality of optical fibers 15 fixed to a plurality of V-grooves 14 provided in the glass substrate 12. An optical fiber array 16 consisting of: a slit 18 provided from the upper surface of each optical fiber 15 to the glass substrate 12 as shown in FIG. 2; and a filter member 2 inserted into the slit 18 0 and light 2 2 transmitted through each optical fiber 1 5 A PD (photodiode) array 28 in which a plurality of active layers 26 for detecting at least the light (branched light) 24 branched by the filter member 20 or the like are mounted, and the PD array 28 is mounted; and And a submount 30 for fixing the PD array 28 toward the optical fiber array 16 and a spacer 32 for stably fixing the PD array 28 at least. As shown in FIG. 2, the two end surfaces of the slit 18 and the front and back surfaces of the filter member 20 function as branch portions 33 for branching a part of the light 22 transmitted through the optical fiber 15. Will be. The optical fiber 15 has a core 40 and a clad 42 as shown in FIG.

Note that, here, an example in which the optical fiber array 16 is configured by a plurality of optical fibers 15 is shown, so that “each optical fiber 15” means “each of four optical fibers”. become. However, since the optical fiber array 16 can be constituted by one optical fiber 15, in this case, “each optical fiber” or “multiple optical fibers” is replaced with “one optical fiber”. Just do it.

Then, in the optical device 10 according to the present embodiment, as shown in FIG. 3, the gap between the slit 18 and the filter member 20 in the slit 18 is filled with the first polymer gel material 50. It is configured. Further, in the present embodiment, the second polymer gel material 5 is provided between the optical fiber array 16 and the PD array 28 and on the optical path of the light 24 branched by the filter member 20. 2 are interposed.

In the present embodiment, the first and second polymer gel materials 50 and 52 are both made of the same material, that is, a silicone-based material. The first and second polymer gel materials 50 and 52 more preferably have a Young's modulus of I M Pa or less and a refractive index of 1.41 to 1.48.

The method for measuring the Young's modulus of the first and second polymer gel materials 50 and 52 was performed as follows. For the measurement of the Young's modulus, the nominal Young's modulus was calculated from a tensile test according to JIS K 649.

On the other hand, the angle of the V-groove 14 formed on the glass substrate 12 is preferably 45 ° or more in consideration of the load applied to each optical fiber of the optical fiber array 16 when the slit 18 is added later. Conversely, a sufficient amount of adhesive is required to make the optical fiber array without lid In order to secure (= adhesion strength), the angle is preferably 95 ° or less, and in this embodiment, it is 70 °.

To fix the optical fiber array 16 to the glass substrate 12, first, the optical fiber array 16 is housed and placed in the V-groove 14, and in this state, an ultraviolet curable adhesive is applied, and the optical fiber array 16 is fixed. This is performed by irradiating ultraviolet rays from the back surface and from above to fully cure the adhesive.

The width "W f of the slit 18 (see FIG. 3) is desirably 15 to 50 / m, and if the width W f is too narrow, the filter member 20 is inserted into the slit 18. If the width Wf is too large, the insertion loss increases, and the attenuation of the signal light 22 may increase.

It is desirable that the depth L of the slit 18 be 130 x m to 250 m. If the depth L i is too shallow, the bottom of the slit 18 may be stopped in the middle of the optical fiber 15, so that the bottom of the slit 18 is used as a starting point for the optical fiber 15. May cause damage. Further, if the depth Lf is too deep, the strength of the glass substrate 12 decreases, which is not preferable.

The inclination angle α of the slit 18 (see FIG. 2), that is, the angle between the slit 18 and the vertical plane is preferably 15 ° to 25 °. If the inclination angle E is too small, the spread of the branched light 24 from the filter member 20 becomes too large, and when applied to multiple channels, crosstalk may be deteriorated. On the other hand, if the inclination angle is too large, the polarization dependence of the branched light 24 from the filter member 20 will increase, which may lead to deterioration of the characteristics.

The filter member 20 has a quartz substrate 54 and a multilayer film 56 for branching formed on the main surface of the quartz substrate 54. The material of the filter member 20 may be a plastic material, a polymer material, or a polyimide material in consideration of the handling of the filter member 20 or the like, but the inclination angle α of the slit 18 is 15 ° to 25 °. Therefore, a material having the same refractive index as that of the optical fiber 15 (quartz) is preferable in order to prevent the optical axis on the transmission side from being shifted due to the bending.

As the structure of the PD array 28, as shown in FIG. 2, a back-illuminated structure was adopted. Activity The upper part of the conductive layer 26 (on the side of the submount 30) was made of an anisotropic conductive paste 58 instead of Au solder, electrodes or silver paste. This portion is preferably made of a material having a low reflectance such as anisotropic conductive paste 58 or air from the viewpoint of crosstalk, instead of a material having a high reflectance such as Au. Of course, a front-illuminated type PD array may be used as the PD array 28.

The light receiving portion (active layer 26) of the back-illuminated PD array 28 was set to about 60 m in diameter. The size of the light receiving portion (active layer 26) is desirably 40 to 80 m in diameter. If the length is less than 40 m, the size of the light receiving portion (active layer 26) is too small, and there is a concern that the PD light receiving efficiency may be reduced. If it is 80 zm or more, stray light can be easily picked up and crosstalk characteristics may be degraded.

Further, a light-shielding mask (not shown) made of Au is provided on the surface of the PD array 28. Specifically, the surface of the PD array 28 is covered with an Au film, and the Au film is removed only in the portion where the branch light 24 is incident. In particular, when the back-illuminated PD array 28 is used, the center position of the portion where the Au film is removed is offset by about 50 m with respect to the light receiving section of the PD array 28. This is because, in the case of the present embodiment, the beam position on the surface of the PD array 28 is different from the beam position on the light receiving section of the PD array 28 because the branched light 24 is obliquely incident on the PD array 28. That's why. Further, it is desirable that the diameter of the light-shielding mask is 30 m to 100 xm. This limits the amount of light if the diameter is less than 30 because the aperture is too small. On the other hand, if it is larger than 100, the light leaks to the adjacent channel, and the crosstalk characteristics may be deteriorated. Further, the shape of the light-shielding mask may be circular, but is more preferably elliptical. The ellipse here refers to an ellipse whose major axis is the same as the traveling direction of the branched light 24. This is because, in the case of the present embodiment, the spot shape at the position of the light-shielding mask of the branched light 24 branched by the branch portion 33 is elliptical.

The mounting structure of the submount 30 was an optical fiber 15—PD array 28-one submount 30. Optical fiber 15—submount 30—PD array 28 can be used, but in this case, the submount 30 Since the light exists between Aino 15 and the PD array 28, the optical path length of the branched light 24 becomes longer, and the spread of the branched light 24 becomes larger, which is preferable from the viewpoint of PD light receiving efficiency and crosstalk. Because there is no. Incidentally, the material of the submount 3 0 was A 1 ₂ o _3.

The back-illuminated PD array 28 has an anode electrode and a force electrode on the active layer 26 side (submount 30 side), and the submount 30 has a common cathode electrode and a common cathode electrode. The anode electrode of each channel is patterned with an Au electrode pattern 60. Au bumps 62 were provided on portions corresponding to the anode electrode and the force source electrode of each channel, and the active layer 26 was filled with an anisotropic conductive paste 58. The Au bumps 62 are used not only to ensure reliable conduction but also to reduce stray light due to reflection and scattering of this part by increasing the distance between the electrodes of the active layer 26 and the submount 30. It was adopted. The anisotropic conductive paste 58 has a property that a conductive material such as silver in the anisotropic conductive paste 58 is collected on a conductive material such as the Au bump 62 by applying heat. As a result, conductivity is provided only with the Au electrode pattern 60.

A portion of the lower surface of the submount 30 corresponding to the active layer 26 was also coated with SiN (not shown) for the purpose of suppressing reflection due to a difference in refractive index. Also were multilayer coated by S i N, A 1 ₂ 〇 _3, T A_〇 like in order to suppress the polarization-dependent generation by the refractive index difference on the surface of the PD array 2 8.

Also, the optical fiber array 16 and the PD array 2

A spacer 32 for determining the gap with 8 is fixed with, for example, an ultraviolet curable adhesive.

As described above, in the optical device 10 according to the present embodiment, the gap between the slit 18 and the filter member 20 in the slit 18 is filled with the first polymer gel material 50. The polymer gel material has an extremely small Young's modulus of less than IMPa. Therefore, even if the slit 18 is filled with the first polymer gel material 50, for example, excessive stress due to thermal fluctuation does not occur. In other words, the temperature characteristics are improved, and the reliability of the monitoring function of the signal light 22 is improved. Further, the first polymer gel material 50 is in a gel state, that is, It is a state located between a liquid and a solid. Therefore, even if the slit 18 is filled with the first polymer gel material 50, there is no problem that it becomes difficult to maintain the shape due to fluidity generated when a liquid is used. This leads to an increase in yield.

When the slit 18 is formed obliquely with respect to the optical axis as in the present embodiment, the refractive index of the filling material in the slit 18 is 0.0 with respect to the refractive index of the optical fiber 15. If the distance is more than 4, an etalon effect (multiple interference) occurs between the optical fiber 15 and the filter member 20, and the monitoring function and the propagation characteristics of the signal light 22 may be significantly reduced. However, in the present embodiment, since the refractive index of the first polymer gel material 50 is set to 1.41-1.48, the slit 18 may be formed obliquely with respect to the optical axis. However, the influence of the etalon effect as described above is reduced, and the deterioration of the monitoring function and the propagation characteristics of the signal light 22 can be suppressed.

Further, in the present embodiment, since the first polymer gel material 50 is made of a silicone-based material, the first polymer gel material 50 is easily matched with the refractive index of the optical fiber 15 and has a property of low moisture retention. In particular, there is an advantage that a change in refractive index due to humidity hardly occurs.

By the way, if a filler or an adhesive having a large Young's modulus is used between the optical fiber array 16 and the PD array 28, the thin film (such as SiN) formed on the surface of the PD array 28 may be damaged, The occurrence of excessive stress may cause problems such as optical axis deviation of the split light 24 and the signal light 22.

However, in the present embodiment, the second polymer gel material 52 having a Young's modulus of IMPa or less is interposed between the optical fiber array 16 and the PD array 28, as described above. Problems can be avoided.

In addition, since the first and second polymer gel materials 50 and 52 are both made of a silicone material, the polarization dependence (PDL) of transmitted light due to the difference in refractive index is reduced. This is advantageous in improving characteristics.

Next, examples of the optical device 10 according to the present embodiment will be described. First, a glass substrate 12 used for an in-line optical fiber array 16 was manufactured by grinding. As the glass substrate 12, a borosilicate glass material (here, in particular, Pyrex (registered trademark) glass material) was used. The dimensions of the glass substrate 12 were 16 mm in length and 1 mm in thickness, and the V-grooves 14 for aligning the optical fiber array 16 were formed by 12 grindings at a pitch of 250 × m and a depth of about 90 / m.

Next, the optical fiber array 16 was assembled. Fiber optic array 16 is 2

A 12-core tape core wire having a pitch of 50 xm was used. The 12-core tape was stripped so that the coating removal part (middle stripping part) in the middle became 12 mm, placed on the V-groove 14 of the glass substrate 12, and fixed with an ultraviolet curing adhesive.

Next, a slit 18 was formed on the optical fiber array 16. The slit 18 had a width Wf = 30 ^ m, a depth 1 ^ = 200111, and an inclination angle α of 20 °. Next, the filter member 20 was manufactured. For example S i 0 ₂ on a quartz substrate 54 was formed at _{_{Τ i 0 2, A 1 2}} 0 3 of the multilayer film 56 vapor deposition. The quartz substrate 54 provided with the multilayer film 56 was cut into a size of 6 mm × 2 mm to form a chip. The chipped quartz substrate 54 was polished to 25 m and thinned. The inclination design was 20 °, the branching ratio was 93% for transmission and 7% for reflection.

After that, the filter member 20 was inserted into the slit 18, the first polymer gel material 50 was filled in the gap between the slit 18 and the filter member 20 in the slit 18, and the filter member 20 was mounted. .

The PD array 28 was mounted on the submount 30. The number of channels of the PD array 28 was 12 ch, and the dimensions were 150 m in height, 420 m in width, and 3 mm in length.

As the structure of the PD array 28, as in the optical device 10 according to the present embodiment, a back-illuminated type was adopted. The upper part of the active layer 26 (on the side of the submount 30) was filled with an anisotropic conductive base 58.

Next, the PD array 28 was aligned. Specifically, a spacer 32 for determining a gap between the optical fiber array 16 and the PD array 28 was attached to the submount 30.

The material of the spacer 32 is borosilicate glass, in this case, in particular, Pyrex. (Registered trademark) glass material. The gap length was set to 10 m. That is, since the thickness of the PD array 28 including the Au bumps 62 is 190 m, the spacer 32 is set to 200 m.

Then, a required amount of a second polymer gel material 52 was applied to the upper part of the optical fiber 15 which is the optical path of the branched light 24. The alignment with the PD array 28 is such that light enters the channels at both ends of the optical fiber array 16 so that the PD light receiving power of the branch light 24 (the light receiving power in the active layer 26 corresponding to the both-end channels) is maximized. , Conducted at the activiation. At this time, the PD light-receiving power was monitored by monitoring the output from the active layer 26 corresponding to both ends of the channels while applying a probe to the submount 30. Thereafter, the PD array 28 was fixed to the optical fiber array 16 by ultraviolet rays. At this stage, the optical device according to the example is completed. Finally, the optical device according to the example was mounted on a package to obtain a product.

Then, measurement and evaluation of the optical device according to the example were performed. The polarization dependence of the branched light 24 was good at less than 0.3 dB, and the variation of the light receiving efficiency due to the temperature change was good at less than 0.2 dB. In addition, long-term reliability showed good characteristics after a lapse of 1000 hours in a thermal test at a temperature of 85 ° (:, 85% humidity).

In addition, the optical device according to the present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the gist of the present invention.

Claims

The scope of the claims

1. A slit (18) provided in the light transmission means (15),

A filter member (20) inserted into the slit (18) and branching a part of the light (22) propagating through the light transmitting means (15);

An optical device comprising: a gel material (50) having a light transmitting ability filled in the slit (18).

2. The optical device according to claim 1,

The optical device, wherein the gel material (50) has a Young's modulus of IMPa or less.

3. The optical device according to claim 1 or 2,

The optical device, wherein the gel material (50) has a refractive index of 1.41 to 1.48.

4. The optical device according to any one of claims 1 to 3,

The optical device, wherein the gel material (50) is made of a silicone material.

5. The optical device according to any one of claims 1 to 4,

An optical element (28) is arranged at least on the optical path of the light (24) branched by the filter member (20) outside the light transmitting means (15),

A gel material (52) is interposed between the light transmitting means (15) and the optical element (28) and on the optical path of the light (24) branched by the filter member (20). An optical device, comprising:

6. The optical device according to claim 5, A gel material (50) filled in the slit (18) of the light transmission means (15); and a gel material (52) interposed between the light transmission means (15) and the optical element (28). An optical device, wherein both are made of the same material.

7. The optical device according to any one of claims 1 to 6,

The optical device, wherein the light transmitting means (15) is an optical fiber.

8. In the optical device according to any one of claims 1 to 7,

An optical device characterized in that the width of the slit (18) is 15 to 50 mm.

9. In the optical device according to any one of claims 1 to 8,

An optical device, wherein the angle of the slit (18) with respect to a reference plane is 15 ° to 25 °.

10. The optical device according to any one of claims 1 to 9,

The filter member (20) is

A quartz substrate (54),

An optical device comprising: a multilayer film (56) formed on a main surface of the quartz substrate (54).