JPS5857102A - Optical fiber end face lens - Google Patents

Abstract

PURPOSE:To obtain an optical fiber end face lens which does not lose the light converging function even if it is adhered directly to an optical waveguide film with an adhesive, by packing materials having a high refractive index in a spherical recess formed in the core part of the optical end face. CONSTITUTION:A spherical recess 2 is formed in a core part 11 on the end face of an optical fiber 1 where the core part 11 having the round section in the center is surrounded with a clad part 12, and a transparent high-refractive index material 3 which has a refractive index higher than that of the core part 11 is packed in this recess 2. In case of formation of this optical fiber end face lens, the core part 11 in one end of the optical fiber 1 is etched to form a recess part 13. The end face of the optical fiber 1 is heated for a short time with a propane gas flame or a weak oxyhyrogen flame to make the recess part 13 into the recess 2 having a smooth spherical curved surface. The transparent high-refractive index material 3 which has a refractive index higher than that of the glass of the core part 11 is packed in this recess 2, thus forming the end face lens.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens at the end of an optical fiber used in the field of optical communication.In recent years, there has been remarkable progress in optical communication systems using original fibers. One of the major problems to be solved in connection with the spread of such optical communication systems is the coupling between semiconductor lasers and optical fibers, or the coupling between optical fibers and original integrated circuits using 1N optical waveguides. In particular, in a single mode optical fiber system, the core (7 is 5 to 1
Since μ is extremely small, on the order of 0 μm, various methods have been proposed to improve this coupling efficiency.One method is to insert a lens system between the optical 7-eyeper and the semiconductor laser. As is known, in this case, the coupling efficiency is certainly improved, but it requires alignment at three or more points, including the optical 7-eyeper, the lens, and the semiconductor laser, which requires a long time for adjustment, and reduces productivity. The problem was that it was bad.

As a solution to the above-mentioned drawbacks, it has been proposed to form a mold-free convex lens on the end face of the optical fiber. For example, P. Kayeun et al.
9111, No. 17111, No. 2, pages 400-402, the etching speed for the end face t1 of the original fiber consisting of the core and cladding portions is p larger than the etching speed for the core portion by 11V&
By immersing it in an etching solution and selectively etching the cladding part, a convex lens is formed at the end of the core part. The adjustment time required for coupling with is significantly reduced.

However, although the convex lens formed in the core between the ends of the optical fiber is effective in optical coupling through air such as in the case of coupling with a semiconductor laser, it is especially effective in optical integration. When it is necessary to use adhesive to secure the relative positional stability, such as when connecting to a circuit, the refractive index of the adhesive is generally close to the oil curvature of the microconvex lens. However, a convex lens has the disadvantage that it loses its focusing effect and cannot serve its intended purpose.

The present invention has been made in view of the above circumstances.
OJI's main objective is to provide an optical 7-eye glass end face lens that does not lose its light focusing effect even if it is directly bonded to a small optical waveguide antinode with an adhesive.

Another object of the present invention is to create an optical 7-eyeper end lens that can realize a wide range of y-z parameters! - It is about providing.

Below, we will use the actual M moga! A will be explained in detail.

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
a [In Q, the original fiber 1 has a circular cross section at the center;
It consists of an a part 11 and a clad part 12 surrounding it, t and p, and has a spherical shape formed in the core part 11 of 10 mm. The reed is filled with a transparent high refractive index material S having a large refractive index,
Core portion 11t - A convex lens-shaped optical 7-eyeper end lens is formed for the propagating light.

When forming an optical 7-eyeper end lens having the above structure WILt, as shown in 2M), the core part 11 and the cladding 1
! When the Hikari 7 Eyeper 1O1jll consisting of A12 is immersed for a certain period of time in an etching solution that etches the core part 11 more quickly than the Clarard part 12, the core part 11 is selectively etched and the recessed part 13 is formed ( jf!
2B(b)). The shape of this recessed portion 13 is similar to that of the core portion 11KI.
When the distribution of dopant added to i is in a constant step shape in the radial direction, it is cylindrical. Next, when this party fiber 10 end l1ir is heated for a short time with a 1p pan gas flame or a weak oxyhydrogen flame, the 8-flange-shaped recess 13 is caused by the core part 110 glass being locally Ki! In order to melt, it has one smooth spherical surface (which becomes the depression 2 (Fig. 1g2 (@)ノ).

Subsequently, by filling this depression 2 with a transparent high refractive index material 3 having a refractive index greater than that of the glass of the core portion 11, an optical fiber end face y-z as shown in FIG. 4 can be formed. 0, as the optical fiber 1, the core part 11
If the to-bar/toad distribution is graded, selective etching will create a spherical shape on its own!
is formed, making it possible to omit surface IIIA heating by flame.

For such an optical fiber curved lens, the core portion 11 is selected as Elatin! Since the grooves 2 are formed using epoxy resin, alignment with the core portion 11 is not a problem, and since the convex lens is formed by the high refractive index material 3, the epoxy resin is used.

03 No. 311i that does not lose its light focusing effect even when fixed to an optical integrated circuit etc. through a transparent adhesive layer such as 7 Otobo/D
In this embodiment, the core part 11 is not only filled with minerals, high refractive index materials 3 and 2tC, but also filled with a metal body of 7 mm in diameter. However, when the convex lens is formed by the high refractive index material 3 at the end 20, the same focusing effect as described above can be obtained.In carrying out the present invention, the light 7 As for AIPA, for example, the composition of the gore part is atom-G.01 gas, and the composition of the cladding part is 810. You can use the glass light 7 eyelid. Such optical fibers are usually fabricated by the MCVDv & Medium WAD method, but the WAD method is more preferable because there is no irregularity called delag in the center of the core. As an etching solution for the above composition. For example, 5ft of HF water can be used.0, that is, tThis etching wave 0810s - Since the etching liquid level for G@Os-based glass increases rapidly as the degree of G@pseudo-minal increases, the present invention It is extremely suitable for the purpose of ◎Similarly, this OH
The F aqueous solution acts effectively in achieving the object of the present invention even on 7-Aipers whose core composition is gio, -P, O, glass. 7 Eyepa S* (transparent IIi high refractive index material that fills the cavity is Gabemus S18B glass (refractive index! LD medium).
3) etc. Chalcogenga 5x, 2m8 (no-13
), compounds such as ZHO (mn=1-9), phenol formaldehyde resin (!ID -1,70)
These high refractive index materials are formed on the end face of an optical fiber to form a spherical surface. 8, Z,
It is possible to use means such as (in the case of O), melt coating (in the case of chalcogen glass, plastic), etc.Next, we will review the forming method for specific implementations.

The optical fiber is manufactured using the vAD method and has a good outer diameter Is!
5% m+ () using a single mode light 7 eyeper; The cladding part is made of StO and glass, and the refractive index difference between the core and cladding part is α3-.
1 aqueous solution for a certain period of time, and then pulled out and washed with water.

Subsequently, this end face was heated for several seconds with a Glo A gas flame, and then observed under a scanning electron microscope.As a result, smooth spherical depressions were formed on the end face Ka. Figure 4 shows that the radius of curvature of the concave formed at that time is 14 times the etching time. , the core diameter was about the same as that of the ninety-nine fiber used.

Next, in the round spherical depression formed in this way, 18 g
Filled with glass. As a filling method, a vacuum evaporation method was used to perform vacuum evaporation between 1 and zIiIP under a vacuum condition of about I x 10-' nu+sHf using glass fragments as a source, as shown in Figure 515 (a). As shown in FIG.
111iK formed and mourning (including buried 5st, covering the Shima armpit end 15~2011wa thick Mus18 guff layer 54
was deposited, and then the Am
By polishing the ass glass layer 54, the desired light 7 eyes/(
The end lens has been formed.
When forming a G-0 core with a graded shape.
In the case of having a snow density distribution, the process of heating the end face using flame can be omitted, and the manufacturing accuracy of the end face can be improved.
The Getys concentration decreases towards the periphery and reaches 0 at the part in contact with the cladding.
By using a single mode optical fiber with a core diameter of 10 μm, it was possible to precisely control the medium diameter of the spherical depression by changing the etching time. In the case of an optical fiber with a concentration distribution, it is also effective to use a short graded fiber with a lens formation as described above as a big tail. If light reflection at the boundary m'''C with the high refractive index material filling there is a problem, 810
1-TasOg-based glass thin glass thin film A reflective coating film may be formed in a spherical recess by means such as sputtering.

According to the present invention, since the spherical depression formed in the core part is filled with a high refractive index material and has a nine-structure structure, the photobond in the resin in the epoxy resin can be bonded without impairing the light focusing effect. It can be fixed to an optical integrated circuit etc. through a transparent adhesive layer such as It can also serve as a refractive index material. That is,
In this case, (rather than just forming a tube and attaching it with the adhesive described above), at the same time as fixing the Hikari 7 eyelid to the optical integrated circuit etc., fill the recess with the adhesive. However, in general, it is preferable to use the above-mentioned photobond in epoxy resin as the adhesive in terms of stability such as life span.In addition, in the theory lJ! mentioned above, It is formed in the core part between the ends of the optical fiber and filled with a II4 refractive index material tube (the filling is made into a spherical depression, but it goes without saying that this expansion is not limited to a true spherical surface, and one element is effective. It suffices if O can form a lens that has a focusing effect,
In particular, when the core portion of the optical fiber has an elliptical cross section, this corner also becomes an ellipsoid.

As explained above, according to the present invention, the spherical depression formed in the m-plane core of the optical fiber is filled with a high refractive index material. When bonding to large integrated circuits, etc., alignment is easy and the light focusing effect is effectively maintained through an adhesive layer such as epoxy resin or photobond, which has an O refractive index similar to that of the core glass. In addition, by selecting the refractive index value of the high refractive index material, it is possible to adjust the degree of focusing effect to various extents (even if the index radius of the pin is the same). It has various excellent effects such as the ability to realize a wide range of lens parameters depending on the bore glass 111w, etching time, type of high refractive index material, etc., and contributes to the spread and development of optical integrated circuits. There is a huge amount to do.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the first part of the present invention;
Figures (a)t (b)t (c+) are cross-sectional views at each manufacturing process 8, Figure 3 is a cross-sectional view showing another embodiment of the present invention, and Figure 4 is the dependence of the self-weight radius of the recess on etching time. Figures 5(a) and 5(b) are cross-sectional views showing still another embodiment of the present invention in each manufacturing process. 51...Core f
l, 12, 52... Talarado part, 13... Fist recessed part, 2. ! ! 3. Fist... (#Work, 3... High refractive index material, 54... Asm11m glass layer. Patent applicant Nippon Telegraph and Telephone Public Corporation agent Masaki Yamakawa Figure 4 Gopken '7-El Fi [,1

Claims (1)

[Claims] An optical fiber surface-increasing lens formed by providing a spherical recess in the core of the optical fiber, and filling this recess with a transparent material having a larger refractive index than the core of the optical fiber.