JPH073495B2 - Optical coupler - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical coupler between a light emitting element and an optical fiber used in the fields of optical fiber communication, optical fiber data transmission and the like.

(Conventional Technology) Conventionally, as a technology in such a field, IEEE Journal of Quantum Electronics, QE-18
[4] (1982-4) (US) P.705-717. The configuration will be described below with reference to the drawings.

FIG. 2 is a sectional view showing an example of the configuration of the conventional optical coupler described in the above document. This optical coupler shows an example of optical coupling between a laser diode (hereinafter, referred to as LD) and a single mode optical fiber (hereinafter, simply referred to as optical fiber) by a compound lens system using two lenses. is there.

In the figure, 1 is a circular base of an optical coupler, and an LD 3 is fixed to the front surface of the base 1 via an LD fixing base 2. In front of the laser light output end face of the LD3, a first lens 4 consisting of a spherical lens whose center is aligned with the optical axis of the laser light
The first lens 4 is fixed to a cylindrical first lens fixing base 5 and attached to the base 1. First
In front of the lens 4, a second lens 6 which is also a rod lens of a focusing type that is aligned with the optical axis is fixedly provided on a cylindrical second lens fixing base 7, and this second lens fixing base is provided. Reference numeral 7 is attached to the base 1. Further, at the optical axis position in front of the second lens 6, the optical fiber 8
Is fixed to a cylindrical optical fiber fixing base 9, and the optical fiber fixing base 9 is attached to the front part of the second lens fixing base 7. As the material of the base 1, the LD fixing base 2, the first lens fixing base 5, the second lens fixing base 7, and the optical fiber fixing base 9, metal is mainly used, and each of them is joined by solder or adhesive. Has been done.

The optical coupler having the above configuration is assembled by the following procedure. First, the LD 3 is attached to the front surface of the base 1 via the LD fixing base 2 so that the optical axis thereof is vertical. Then, align the center of the sphere of the first lens 4 with the optical axis of LD3,
In addition, the first lens 4 is moved to the first position while maintaining a predetermined distance from the LD3.
It is attached to the base 1 via the lens fixing base 5. Next, the second lens fixing base 7 is adjusted and fixed to the base 1 so that the axis of the cylindrical second lens 6 and the optical axis of the LD 3 are aligned. At this time, if the optical axis of LD3 is not perpendicular to the base 1 due to an attachment error with respect to the base 1, or if the first lens 4 is deviated from the optical axis, the correction should be performed first. Two
Since the lens 6 is used, the second lens fixing base 7 is attached to the base 1 tilted by the correction angle. At this time, since a gap corresponding to the inclination is formed on the joint surface between the base 1 and the second lens fixing base 7, the gap is filled with solder or adhesive or the like to adjust the inclination angle while fixing them. . Then, the optical coupler is assembled by attaching the optical fiber fixing base 9 to the second lens fixing base 7 while adjusting the optical fiber fixing base 9 so that the tip of the optical fiber 8 is aligned with the axis of the second lens 6.

In the optical coupler configured as described above, the laser light emitted from the light emitting region on the front end face of the LD3 is refracted by the first lens 4 as shown by a dashed line 10 in the figure and becomes a substantially parallel light beam. Become. This substantially parallel light beam is transmitted to the second lens 6
After being incident on, the light is refracted and focused on the tip of the optical fiber 8 to perform an optical coupler between the LD 3 and the optical fiber 8.

In this type of optical coupler, since a lens having a relatively large diameter is used, as described in the above-mentioned document, the mounting tolerance of each lens with respect to the optical axis for performing stable optical coupling. Has the advantage of being relatively large. Therefore, when the angle between the optical axis of the laser light and the axis of the second lens 6 is the same, the tolerance of the lateral deviation of the axis of the second lens 6 from the optical axis is large, and the second If the lens 6 is within this tolerance range, the decrease in the efficiency of optical coupling is small, and a stable optical coupling state can be maintained.

(Problems to be Solved by the Invention) However, the optical coupler having the above configuration has the following problems.

(1) When the inclination of the optical axis of LD3 and the displacement of the first lens 4 with respect to the optical axis are large, the correction angle with respect to the vertical of the second lens fixing base 7 with respect to the base 1 is large in order to correct these. In this case, the gap generated at the joint surface between the base 1 and the second lens fixing base 7 becomes large, and it becomes difficult to adjust the correction angle by filling with solder or adhesive. Therefore, not only the mounting accuracy deteriorates and the optical coupling efficiency decreases, but also the assembly work efficiency deteriorates.

(2) The optical fiber fixing base 9 is attached to the second lens fixing base 7 by adjusting the position and angle of the axis of the optical fiber 8 while maintaining the distance between the second lens 6 and the optical fiber 8 at a predetermined dimension. However, it is difficult to maintain the mounting accuracy and the work efficiency is poor.

The present invention has the problems that the prior art has, because the correction of the angle with respect to the optical axis by the second lens 6 is limited to a small angle and the correction range is narrow, and it is difficult to accurately attach the optical fiber 8. Therefore, the present invention provides an optical coupler that solves the problem that the optical coupling efficiency may be deteriorated and the assembly work efficiency is poor.

(Means for Solving Problems) In order to solve the above problems, the present invention includes a light emitting element that emits light and a first lens that converges light emitted from the light emitting element into substantially parallel light fluxes. A first lens fixing base for fixing and a second lens for focusing the emitted light that has passed through the first lens
An optical coupler including a second lens fixing base for fixing a lens and an optical fiber fixed to the second lens fixing base for receiving the emitted light having passed through the second lens, wherein the second lens fixing base is provided. A housing member fixing cylinder having a through hole and a sliding surface formed therein, and a protruding portion that is in contact with the sliding surface and that is slidable and can be adjusted in angle, and has the second inner portion. It is configured by a second lens / optical fiber housing member having a through hollow portion that houses the lens and the optical fiber with their respective axes aligned.

(Operation) According to the present invention, since the optical coupler is configured as described above, the second lens / optical fiber accommodating member whose protrusion is in contact with the inner surface of the accommodating member fixing cylinder is the second lens and the optical fiber. Accurately house each on a straight line that matches the axis of each
In addition, it serves to enable free and highly accurate correction of the optical axis direction and the angle with respect to the optical axis in the housing member fixing cylinder. At the same time, adjustment of the second lens and the optical fiber,
It serves to facilitate the correction of the direction of the optical axis and the angle with respect to the optical axis. Therefore, the problem can be eliminated.

(Embodiment) FIG. 1 is a cross-sectional view of a compound lens type optical coupler showing a first embodiment of the present invention, in which an LD is used as a light emitting element and a single mode optical fiber is used as an optical fiber. Is.

In the figure, 21 is a base of the optical coupler, and an LD 23 is fixed to the front surface of the base 21 via an LD fixing base 22. LD
In front of the laser light output end face 23, a first lens 24 composed of a spherical lens having its center aligned with the optical axis of the laser light is arranged. The first lens 24 holds the first lens 24 and at the same time adjusts its position.
The first lens fixing barrel 25 is housed in the first lens fixing cylinder 25 and is fixed to the base 21 via the first lens fixing base 26. A second lens / optical fiber housing member (hereinafter simply referred to as a housing member) having a spherical outer shape on the laser light incident side in front of the first lens 24 and a cylindrical rear surface on the laser light emitting side. 27 are provided. A hollow portion having a circular cross section that extends completely in the optical axis direction is provided inside the housing member 27, and a laser beam incident side of the hollow portion is formed of a spherical lens that is cut into a cylindrical shape according to the inner diameter of the hollow portion. The second lens 28 is housed, and the optical fiber 30 covered with the cylindrical ferrule 29 is housed inside the laser light emitting side. The accommodating member 27 is fixed by contacting the outer surface of its spherical portion with the inner surface of a cylindrical accommodating member fixing cylinder 31. The housing member fixing cylinder 31 is fixed at its flange portion to a cylindrical housing member fixing base 32. The base 21, the LD fixing base 22, the first lens fixing cylinder 25, the first lens fixing mold 26, the housing member 27, the ferrule 29, the housing member fixing cylinder 31, and the housing member fixing base 32 are mainly made of metal. The respective connections are made by solder or an adhesive such as an epoxy resin.

Next, a method of assembling the optical coupler configured as described above will be described. First, mount the LD 23 via the LD fixing base 22
After being fixed to 21, the first lens 24 is held by the first lens fixing barrel 25, and then the first lens fixing barrel 25 is inserted into the opening of the first lens fixing base 26. Subsequently, the first lens fixing base 26 is fixed to the base 21, and at this time, the first lens fixing barrel 25
The first lens 24 is adjusted so as to be set at a predetermined position with respect to the optical axis while holding the opposite end of the lens holding side. When the adjustment is completed, the first lens fixing base 26 is finally fixed to the base 21. Separately from this, the second lens 28 and the optical fiber 30 are previously housed and fixed in the housing member 27 at predetermined positions. Next, the housing member 27 is fixed to the base 21 via the housing member fixing cylinder 31 and the housing member fixing base 32. At this time, the base 21 and the housing member fixing base 32 are fixed with screws, solder, adhesive or the like. The accommodating member fixing base 32 and the accommodating member fixing cylinder 31 are adjusted in position by smoothly moving in the surface direction by planar contact using the flange surface of the accommodating member fixing cylinder 31, and the first member in the accommodating member 27. The two lenses 28 and the optical fiber 30 are attached at predetermined positions so that the optical axes thereof coincide with the optical axes. Further, since the accommodating member 27 is accommodated with the outer surface of the spherical portion thereof in contact with the inner surface of the accommodating member fixing cylinder 31, the accommodating member 27 can slide in the front-back direction of the optical axis, and at the same time, the angle with respect to the optical axis can be freely set. It can be adjusted to a predetermined value by changing to. In this way, the position and the angle of the housing member 27 are set, and as a result, the second lens 28 and the optical fiber 30 are set to the predetermined position and the angle with respect to the optical axis, and then the housing member is fixed from the open end of the fixed barrel 31. The contact portion of the spherical portion of the member 27 is filled with solder or an adhesive agent and fixed.

This embodiment has the following advantages.

Since the accommodating member 27 is provided, and a hollow portion having a cylindrical shape that accurately sees through the axial center is provided inside the accommodating member 27, the second lens 28 and the optical fiber 30 are accurately preliminarily set at predetermined positions therein. Can be accommodated. Moreover, it is possible to save the trouble of adjusting these shaft cores.

The accommodating member 27 has a spherical outer shape, and the spherical part is in contact with the inner surface of the accommodating member fixing cylinder 31.
Since the optical axis direction can be freely adjusted, the second lens 28 and the optical fiber 30 can be accurately adjusted with respect to the optical axis because the angle can be adjusted freely in the housing member fixing cylinder 31 and at a large angle. It can be easily adjusted.

Since the second lens is a spherical lens instead of a rod lens, the incident lens surface of the laser light has a certain curvature, and the rate at which the reflected light on the lens surface returns to the light source is smaller than that of a flat rod lens. Therefore, the LD modulation characteristics are rarely adversely affected.

Since the first lens fixing cylinder 25 is provided, the adjustment at the time of mounting the first lens 24 becomes easy and accurate by mounting by adjusting the end portion.

In the present embodiment, as a result of the above advantages, the assembling accuracy of the optical coupler can be dramatically improved, and the optical coupling efficiency can be improved. In addition, since the adjustment at the time of assembling each part is facilitated, it can be expected that the work efficiency and the yield in the assembling process are improved.

FIG. 3 is a sectional view of an optical coupler showing a second embodiment of the present invention. The main difference of this embodiment from the first embodiment is that
That is, a non-reflective film was formed on the laser light incident side end surface of the optical fiber, and an annular first lens holder for holding the first lens was provided.

That is, an LD fixing base 42 that projects integrally with the base 41 is provided on the front surface of the base 41 of the optical coupler, and the LD 43 is fixed to the LD fixing base 42. The first lens 44, which is arranged in front of the LD 43 with its optical axis aligned, is held by the annular first lens holder 45 and fixed to the front surface of the LD fixing base 42. A glass window 46 for hermetically sealing is provided in front of the first lens 44 by being fixed to a housing member fixing base 47. The glass window 46 and the housing member fixing base 47 form an airtight sealing structure together with the base 41, and the inert gas is injected into the interior to seal the LD 43. A non-reflective film 50 formed by vapor deposition or the like is applied to the front end surface of the optical fiber 49 fixed to the housing member 48.

With the above configuration, the same operation as in the first embodiment,
Not only the effect is obtained, but also the structure of the LD fixing base 42 and the first lens holder 45 integrated with the base 41 is simplified,
Its manufacture and installation work become easy. Also, a non-reflective film
By providing 50, it is possible to improve the optical coupling efficiency and at the same time prevent reflected light from returning to the light source and adversely affecting the modulation characteristics.

FIG. 4 is a sectional view of an optical coupler showing the third embodiment of the present invention. The difference of this embodiment from the second embodiment is that a glass plate which is separately subjected to an antireflection treatment is provided instead of forming an antireflection film on the front end face of the optical fiber.

The ferrule 52 for holding the optical fiber including the front end face of the optical fiber 51 is attached to the laser light incident side end face with a glass plate 53 having one surface subjected to anti-reflection treatment with the anti-reflection treatment surface facing outside as an adhesive. Has been. As the adhesive, an optical adhesive having a refractive index substantially the same as that of the optical fiber is used.

With such a configuration, substantially the same action and effect as those of the second embodiment can be obtained, and at the same time, the glass which has been subjected to the antireflection treatment by a simpler process than the formation of the antireflection film on the end face of the optical fiber 51. A plate 53 can be provided.

FIG. 5 is a sectional view of an optical coupler showing the fourth embodiment of the present invention. This embodiment is different from the first embodiment in that
That is, a gear-shaped protruding portion is provided on the cylindrical outer peripheral portion of the lens / optical fiber housing member, and a receiving portion that engages with the gear-shaped protruding portion is provided on the inner surface of the housing member fixing cylinder. FIG. 6 shows a front sectional view (A) of the gear-shaped protruding portion and a front sectional view (B) of the receiving portion.

The cylindrical outer peripheral portion of the housing member 61 has concentric gear-shaped protrusions.
62 is provided, and a receiving portion 64 in which a groove is carved so as to mesh with the gear-shaped protruding portion 62 is formed on the inner surface of the housing member fixing cylinder 63.
Is provided. The gear-shaped protruding portion 62 and the receiving portion 64,
By inserting the gear-shaped protruding portion 62 from the opening end of the housing member fixing barrel 63 along the optical axis to the light source side, the structure is such that they mesh with each other. There is some play to allow adjustment.

With the above configuration, the same operation as in the first embodiment,
At the same time that the effect can be expected, the contact area between the housing member 61 and the housing member fixing cylinder 63 becomes larger than that in the first embodiment, and moreover, the rotation direction is restricted with respect to the shaft core. If fixed by an adhesive or the like, there is an advantage that a stronger joint strength can be obtained.

The present invention is not limited to the illustrated embodiment, and various modifications can be made. For example, the following modifications can be given.

In the first to fourth embodiments, L is used as the light emitting element.
Although a single mode optical fiber is used as the optical fiber D, the invention is not limited to this, and a light emitting diode or a multimode optical fiber may be used.

The accommodating member fixing cylinder and the accommodating member fixing base in the first to fourth embodiments may be integrated structures instead of separate structures.

The accommodating member has a cylindrical outer shape provided with a spherical or gear-shaped protrusion, but the present invention is not limited to this. For example, instead of the spherical protrusion, a concentric disk-shaped protrusion may be provided, and the portion in contact with the inner surface of the housing member fixing cylinder may have a curvature. Further, the gear-shaped protruding portion may be changed in shape and number of teeth, and accordingly, the shape of the receiving portion on the inner surface of the housing member fixing cylinder may be changed accordingly.

The optical fiber is attached to the hollow portion of the housing member through the ferrule, but the invention is not limited to this.
For example, the portion corresponding to the ferrule may be provided as an integral structure in the hollow portion of the housing member.

The second lens is not limited to a spherical lens and may be, for example, a rod lens.

(Effects of the Invention) As described in detail above, according to the present invention, the housing member fixing cylinder forming a part of the fixing member of the optical coupler and the inner surface of the housing member fixing cylinder are slidable in contact with each other. Since the second lens and the optical fiber housing member that can change the angle with respect to the optical axis are provided, the correction range of the angle of the second lens with respect to the optical axis can be widened, and at the same time, the second lens and the optical fiber can be mounted with high accuracy. Therefore, the optical coupling efficiency can be increased. Furthermore, since adjustment and correction at the time of mounting the second lens and the optical fiber are facilitated, an effect of improving the assembly work efficiency of the optical coupler can be expected.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical coupler showing a first embodiment of the present invention, and FIG. 2 is a sectional view showing a constitutional example of a conventional optical coupler.
3 is a sectional view of an optical coupler showing a second embodiment of the present invention, FIG. 4 is a sectional view of an optical coupler showing the third embodiment of the present invention, and FIG. 5 is a sectional view of the present invention. FIG. 6 and FIG. 6 are sectional views of the optical coupler showing the fourth embodiment and show the sectional shapes of the gear-like protrusion and the receiving portion in the partial sectional view of FIG. 21,41 …… Base, 22,42 …… LD fixed base, 23,43 …… Laser diode (LD), 24,44 …… First lens, 25 …… First
Lens fixing tube, 26 …… First lens fixing base, 27,48,61 ……
Second lens / optical fiber housing member, 28 ... Second lens,
29,52 …… Ferrule, 30,49,51 …… Optical fiber, 31,63
...... Accommodating member fixing cylinder, 32, 47 …… Accommodating member fixing base, 45…
… First lens holder, 46 …… Glass window, 50 …… Non-reflective film, 53 …… Glass plate, 62 …… Gear-shaped protrusion, 64 …… Receiving part

Claims (1)

[Claims] 1. A light emitting element that emits light, a first lens fixing base that fixes a first lens that converges the light emitted from the light emitting element into substantially parallel light fluxes, and the light emitted through the first lens. A second lens fixing base for fixing a second lens for focusing the second lens, and the second lens fixing base fixed to the second lens fixing base.
In an optical coupler including an optical fiber that receives the emitted light that has passed through a lens, the second lens fixing base includes a housing member fixing cylinder that has a through hole and has a sliding surface formed therein. A second protrusion having an external protrusion that is in contact with the sliding surface and is slidable and whose angle can be adjusted; and a second internal hollow portion that accommodates the second lens and the optical fiber with their axes aligned
An optical coupler comprising a lens and an optical fiber housing member.