JPH0456912A - Distributed refractive index type lens fixation structure and lens and optical fiber assembly - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a structure for fixing a gradient index lens to a lens holder and a structure of a gradient index lens/optical fiber assembly, which prevents deterioration of the optical characteristics of the gradient index lens. (And for the purpose of providing a low-cost gradient index lens fixing structure and a lens/optical fiber assembly, 7 flanges are provided on one end surface of the cylindrical body, and a slit parallel to the axis is provided in the shell portion.) a lens holder, each having an axial center hole, the inner diameter of which is larger than the outer diameter of the gradient index lens, and a pair of rings, each of which has an axial center hole that has an inner diameter larger than the outer diameter of the gradient index lens; The rings are inserted into the openings of the axial holes so as to sandwich the gradient index lens inserted into the holes, and the outer periphery of each ring is laser welded to the end surface of the lens holder. composition.

[Industrial application field]

The present invention relates to a structure for fixing a gradient index lens to a lens holder, and a structure of a gradient index lens/optical fiber assembly.

[Conventional technology]

Figure 4 is a sectional view of a conventional lens/optical fiber assembly, and Figure 5 is a diagram of another conventional example, where (a) is a sectional view, and (b)
is a perspective view of a lens holder portion.

In FIG. 4, 10 is a cylindrical assembly housing made of stainless steel or the like. One side of the axial hole of the assembly housing 10 is connected to a lens system insertion hole Ill having an inner diameter slightly larger than the outer diameter of the gradient index lens 1.
The other side of the axial hole is the ferrule insertion hole 12.

By inserting the gradient index lens 1 into the lens system insertion hole 11-1 and soldering the circumferential surface of the gradient index lens 1 to the inner wall of the lens system insertion hole Ill, the gradient index lens 1 is inserted into the assembly housing 10. It's stuck.

The ferrule (not shown) has a cylindrical shape made of stainless steel or the like, and the end of the optical fiber is inserted and fixed into the axial hole of the ferrule.

The end face of the ferrule is polished to match the input/output end face of the optical fiber to give a smooth finish to the desired end face shape, and the inner diameter of the ferrule insertion hole 12 is dimensioned to allow the ferrule to be inserted snugly. be.

The ferrule is inserted into the ferrule insertion hole 12 with its input/output end face facing the lens, and is fixed to the assembly housing IO by laser welding or the like.

In FIG. 5, one side of the axial hole of the assembly housing IO is a lens system insertion hole 11-2 into which the lens holder 5 is loosely inserted, and the other side of the axial hole is a ferrule insertion hole 1.
2. Note that the inner diameter of the lens system insertion hole 112 is
It is sufficiently larger than the outer diameter of the cylindrical body of the lens holder 5, which will be described later.

The lens holder 5 is made of stainless steel or the like and has a substantially cylindrical shape, and has a flange 5B on one end surface of a cylindrical body 5A.

As shown in detail in FIG. 5(b), a slit 7 parallel to the axis is provided from the cylindrical main body 5A to the flange 5B. Note that the axial hole 6 of the lens holder 5
The inner diameter of the gradient index lens I is slightly smaller than the outer diameter of the gradient index lens I.

Further, by enlarging both openings of the axial hole 6, the solder 2 can easily adhere to the outer periphery of the gradient index lens l.

The gradient index lens l is press-fitted into the axial hole 6 of such a lens holder 5, and the outer periphery of both ends of the gradient index lens l is soldered to the lens holder 5 to prevent misalignment in the axial direction. However, the gradient index lens l is fixed to the lens holder 5 by soldering.

The lens holder 5 as described above is loosely inserted into the lens system insertion hole 11-2 of the assembly housing 10, and the flange 5B is inserted.
After bringing the end face of the assembly housing IO into contact with the end face of the assembly housing IO and aligning the optical axes of the gradient index lens l and the optical fiber, the outer periphery of the flange 5B and the end face of the assembly housing IO are laser welded (P is (indicates welding location)
In other words, attach the lens holder 5 to the assembly housing
It is stuck to.

[Problem to be solved by the invention]

However, in the former case, the gap between the outer peripheral surface of the gradient index lens l and the lens system insertion hole 11-1 is filled with solder 2. Therefore, due to changes over time due to creep of the solder 2, there is a risk that the gradient index lens 1 may be misaligned (particularly angularly misaligned), and the optical axis of the gradient index lens l and the axis of the lens system insertion hole 11-1 may shift. There was a problem in that it was not possible to adjust the position so that they matched.

The latter is because the soldering of the gradient index lens l is asymmetrical, so that sometimes non-uniform thermal stress is applied to the gradient index lens l during soldering, and the polarization plane of the gradient index lens l is There was a problem that storage stability deteriorated.

In the latter case, the inner diameter of the axial hole 6 is reduced by providing the slit 7 in the lens holder 5.

Therefore, after providing the slit 7, the inner diameter of the axial hole 6 is further cut to a predetermined size, which may increase the cost of the lens holder 5.

In addition, in both cases, in order to secure the gradient index lens l to the assembly housing or lens holder,
There is a problem in that the outer peripheral surface of the gradient index lens 1 must be plated with gold or the like, resulting in high cost.

The present invention was created in view of these points, and it provides a low-cost gradient index lens fixing structure and a lens/optical fiber assembly. It is intended to.

[Means to solve the problem]

In order to achieve the above object, the present invention, as illustrated in FIG. 22 is provided.

The inner diameter of this axial hole 21 of the lens holder 20 is desirably larger than the outer diameter of the gradient index lens l.

On the other hand, a pair of rings 30A and 30B having an outer diameter smaller than the outer diameter of the gradient index lens I are provided.

Then, the gradient index lens l is inserted into the axial hole 21 of the lens holder 20, and the rings 30A and 30B are inserted into the axial hole 2.
Insert the gradient index lens l into both openings of 1.
abut against each end face of the

In this state, the outer peripheral portions of the rings 30A and 30B are laser welded to the end face of the lens holder 20.

Further, as illustrated in FIG. 3, the ferrule 40 is inserted into one side of the axial hole of the assembly housing IO, and the lens holder 20 is loosely inserted into the other side of the axial hole.

Then, the outer circumferential portion of the flange 20B of the lens holder 20 and the end face of the assembly housing 10 are laser welded and fixed to each other.

[Effect]

As mentioned above, the inner diameter of the axial hole 21 of the lens holder 20 is
Outer diameter of gradient index lens 1 and ring 3°A, 3
It is larger than the outer diameter of 0B.

Therefore, as shown in FIG. 2(a), it is not only easy to insert the gradient index lens and the ring into the axial hole, but also the inner diameter of the axial hole needs to be highly accurate. do not have.

Furthermore, as shown in FIG. 2(b), when the outer circumference of the ring and the lens holder are laser welded, the shell of the cylindrical body is drawn toward the ring, reducing the gap between the slits.
The inner diameter of the axial hole is reduced so that the lens holder holds the gradient index lens.

Therefore, movement of the gradient index lens in the radial direction is prevented, and since the gradient index lens is sandwiched between the pair of rings, movement in the optical axis direction is prevented.

On the other hand, since soldering is not fixed, there is no need to metalize the outer peripheral surface of the gradient index lens with gold or the like, and thermal stress is not applied to the gradient index lens, so the gradient index lens There is no risk of deterioration of polarization preservation property.

Further, as shown in FIG. 3, when the lens holder is assembled into the assembly housing to form a lens/optical fiber assembly, the outer diameter of the lens holder is sufficiently smaller than the inner diameter of the lens system insertion hole of the assembly housing.

Therefore, the lens holder can be moved and adjusted as desired in the radial direction. That is, since it is easy to align the optical axis of the optical fiber and the optical axis of the gradient index lens,
The degree of optical coupling of the resulting lens/optical fiber assembly is high.

〔Example〕

The present invention will be specifically described below with reference to the drawings. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 is a diagram of an embodiment of the first invention, in which (a) is a perspective view shown in separated form, (b) is a perspective view, (C) is a sectional view, and (a) in FIG. b) is a diagram for explaining the action, and FIG. 3 is a sectional view of the second invention.

As shown in FIG. 1(a), the lens holder 20 made of stainless steel or the like has a flange 20B on one end surface of a cylindrical main body 20A, and a slit 22 parallel to the axis in the shell. be.

The inner diameter of the axial hole 21 of the lens holder 20 is larger than the outer diameter of the gradient index lens 1 by a desired value (approximately 0.1 mm).

Further, the length of the lens holder 20 is approximately equal to (gradient index lens length + 2 x ring width).

On the other hand, 30A and 30B are hollow disk-shaped rings made of stainless steel or the like, the outer diameter of which is equal to or smaller than the outer diameter of the gradient index lens l.

As shown in FIG. 1 (bL (C)), the gradient index lens I is inserted into the axial hole 21 of the lens holder 20, and the rings 30A and 30B are inserted into both openings of the axial hole 21, respectively. , after bringing the end faces into contact with the respective end faces of the gradient index lens l, key points on the outer periphery of each of the rings 30A and 30B (Q indicates a welding location) are attached to the end face of the lens holder 20, The gradient index lens l is assembled into the lens holder 20 by laser welding and fixing.

Therefore, as shown in FIG. 2(a), it is easy to insert the gradient index lens and the ring into the axial hole. Further, it is not necessary to make the inner diameter dimension of the shaft center hole highly accurate.

Note that a slit 22 is provided in the shell portion of the lens holder 20,
When the inner diameter is reduced and the inner diameter of the axial hole 21 is significantly larger than the outer diameter of the gradient index lens l, press the cylindrical body 20A with your hand or the like so that the slit width is reduced. By doing so, the inner diameter of the axial hole 21 is set as desired (for example, about 0.1 mm larger than the outer diameter of the gradient index lens).
All you have to do is reduce it to the size of .

The axial hole 21 having such an inner diameter size is a ring 30A.

30B to the lens holder 20, the shell portion of the cylindrical body 20A is drawn toward the ring side, the gap between the slits 22 is reduced, and the axial hole is closed, as shown in FIG. 2(b). The inner diameter is reduced. Therefore, the lens holder 20 holds the gradient index lens 1.

Therefore, the gradient index lens 1 is prevented from moving in the radial direction and in the optical axis direction, and the gradient index lens 1 does not move.

Further, since the gradient index lens 1 is not fixed by soldering as in the conventional case, there is no need to metalize the outer peripheral surface of the gradient index lens 1 with gold or the like.

That is, since the lens holder is easy to process and there is no need to perform surface treatment on the gradient index lens, the lens holder according to the present invention is low in cost.

Furthermore, although laser welding reduces the axial hole, this stress is much smaller than the thermal stress caused by conventional soldering. Therefore, unnecessary asymmetric compressive stress is not applied to the gradient index lens. Therefore, there is no possibility that the polarization preservation property of the gradient index lens will deteriorate.

The gradient index lens fixing structure according to the present invention is combined with an optical semiconductor element such as a light receiving element and a semiconductor laser to form a lens/optical semiconductor element assembly. Alternatively, the above effects can be achieved by combining it with an optical fiber to form a lens/optical fiber assembly.

In FIG. 3, a cylindrical assembly housing 10 made of stainless steel or the like has a lens system insertion hole 11-2 on one side of the axial hole into which the lens holder 20 is loosely inserted, and a lens system insertion hole 11-2 on the other side of the axial hole. is the ferrule insertion hole 12.

The inner diameter of the lens system insertion hole 11-2 is sufficiently larger than the outer diameter of the cylindrical body 20A of the lens holder 20.
The inner diameter of the ferrule insertion hole 12 is such that the ferrule 40 can be inserted snugly.

The cylindrical ferrule 10 made of stainless steel etc.
The end of the optical fiber 45 is inserted into the pore provided at its axis and fixed.

The end face of the ferrule 40 is polished to match the output end face of the optical fiber 45 to give a smooth finish to the desired end face shape.

Lens holder 20 and ferrule 40 are assembled into assembly housing IO in the following manner.

In the ferrule insertion hole 12 of the assembly housing 10,
Insert the ferrule 40, while the lens system insertion hole 11-2
Insert the lens holder 20 into.

Next, with the end surface of the flange 20B of the lens holder 20 in contact with the end surface of the assembly housing IO, light is projected onto the gradient index lens 1, and while observing from the optical fiber 45 side, the lens holder 20 is - Adjust movement within the Y plane (plane perpendicular to the optical axis).

Then, at the position where the light intensity emitted from the optical fiber 45 is the highest, the outer circumference of the seven flange 20B and the end face of the assembly housing IO are laser welded (P indicates a welding point), so that the lens holder 20 is attached to the assembly housing IO. sticks to.

Next, the ferrule 40 is moved and adjusted in the Z-axis (optical axis direction) direction within the ferrule insertion hole 12, and the optical fiber 4
At the position where the light intensity emitted from 5 is the highest, the ferrule 40
The outer periphery of the assembly housing IO and the end face of the assembly housing IO are laser welded and fixed.

Therefore, in the lens/optical fiber assembly according to the present invention, the degree of optical coupling between the gradient index lens l and the optical fiber 45 is high, and the degree of coupling is stable.

〔Effect of the invention〕

As explained above, the gradient index lens fixing structure of the present invention has a large tolerance in the machining accuracy of holes in the lens holder, and there is no need to metalize the outer peripheral surface of the gradient index lens with gold or the like. , low cost.

Further, since unnecessary asymmetric compressive stress is not applied to the gradient index lens, there is no risk of deterioration of polarization preservation property.

On the other hand, the lens/optical fiber assembly according to the present invention has excellent practical effects in that the degree of optical coupling between the gradient index lens and the optical fiber is high and the degree of coupling is stable.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the first invention, (a) is a perspective view shown in separated form, (b) is a perspective view, (C) is a sectional view, (a) of FIG. b) is a diagram explaining the action, FIG. 3 is a sectional view of the second invention, FIG. 4 is a sectional view of the conventional example, FIG. 5 is a diagram of another conventional example, (a) is a sectional view, b) is a perspective view of the lens holder portion. In the figure, l is a gradient index lens, 5.20 is a lens holder, 5A and 20A are cylindrical bodies, 5B and 20B are flanges, 6.21 is a central hole, 7.22 is a slit, and 1O is an assembly housing. , 11-1, 11-2 is a lens system insertion hole, 12 is a ferrule insertion hole, 30A and 30B are rings, 40 is a ferrule, and 45 is an optical fiber. 20 Lens Holder (b) (C) Concave 1st Captured Example of the 1st Ceramic Example Country of Other Introduced Examples

Claims (1)

[Claims] [1] A flange (2
0B), a lens holder (20) each having a slit (22) parallel to the axis in the shell portion, and an inner diameter of the axis hole (21) being larger than the outer diameter of the gradient index lens (1); an outer diameter smaller than the outer diameter of the gradient index lens (1);
A pair of rings (30A, 30B), the axial hole (
The rings (30A, 30B) are each inserted into the opening of the axial hole (21) so as to sandwich the gradient index lens (1) inserted into the ring (30A, 30B).
, 30B) are connected to the lens holder (20B).
) A gradient index lens fixed structure characterized by laser welding to the end face of the lens. [2] The lens holder (20) according to claim 1 is loosely inserted into the axial hole of the assembly housing (10), facing the ferrule (40) inserted into the axial hole, and the flange (20B) and the assembly housing (10)
A lens/optical fiber assembly characterized in that the end face of the lens and the end face of the lens are laser welded.