JP3080394B2 - Fixing method of optical coupling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical coupling fixing method for coupling light from a light emitting element to a light incident element.

<Prior art and its problems> Various configurations have been proposed for an optical coupling system between a semiconductor laser (also referred to as an LD) and a single mode optical fiber. Proposed a pseudo-confocal compound lens system with low tolerance for off-axis during module fabrication [Kono et al., Optical coupling method: Japanese Patent Application No. 58-16]
9383], and reported on the characteristics of the module [Kono et al., Efficient and highly stable laser diode module
for single-mode fiber employing combination of h
emispherical-ended GRIN rod lense and single-mod
e fiber, Appl. opt. vol. 28, pp. 2012, 1989].

FIG. 2 is a schematic diagram of a semiconductor laser module using this pseudo-confocal compound lens system (hereinafter, abbreviated as pseudo-confocal system). In the figure, 10 is a semiconductor laser, 1 is a first
Lens, 2 a second lens, 4 a single mode optical fiber,
Reference numeral 5 denotes a core, 6 denotes an integrated holder, 7 denotes a guide of the integrated holder, 8 denotes a nylon cord of the optical fiber 4, and 9 denotes a stem. In manufacturing such an optical coupling system, the semiconductor laser 10 is fixed to the stem 9 by bonding with a human hand, and the first lens 1 which is a spherical ball GRIN rod lens is fixed to the semiconductor laser 10 based on the reference plane. Is fixed in position.

For an optical output system having such a semiconductor laser 10 and a first lens, a second lens 2 which is in close contact with the end face of the optical fiber 4 and converges light on the end face, and a core 5 in which the single mode optical fiber 4 is fixed. And the integrated part integrated with the holder 6 is arranged on the guide 7. In this case, the integrated portion is integrated as a single unit to easily manufacture the module, and the LD module is formed only by aligning the integrated portion with the light output system.

Here, the principle of optical coupling in the pseudo-confocal system will be described with reference to FIG. This pseudo confocal system, the distance between the semiconductor laser end surface and the first lens has taken longer than the focal length, the first lens 1 to the output light from the semiconductor laser 10 of the spot size W _LD spot size
The beam is converted to a slightly narrower beam so that it becomes W _LD '. On the other hand, from a single mode optical fiber 4 of the spot size W _F fixed to the core 5, the single-mode optical fiber 4 and the same second lens which is combined as an integral unit (GRIN rod lens) 2 Third when considering the case of injecting light as shown in FIG. (b), the opposite direction of the light is expanded by the presence of the second lens 2, the virtual fiber W _F 'is the spot size W _F as the spot size of the integrated portion Can be regarded as.

Then, by making the beam converged by the first lens 1 incident on the virtual fiber which is an integrated part, the light emitted from the semiconductor laser 10 is incident on the single mode optical fiber 4. This is, in other words, a bond between the virtual fiber spot size W _LD 'beam after the first lens 1 emission of the spot size W _F', therefore, W
It is designed so that both the spot size of the _LD 'and W _F' coincide, high coupling efficiency is to be achieved.

Then, the two spot sizes W _LD ', W _F' is tolerance of the shaft misalignment for larger spot size W _F of the single mode optical fiber 4, the virtual fiber is an integral part to the light emitting system is a fixed part Is relaxed, which leads to a drastic relaxation of the manufacturing tolerance of the semiconductor laser module. On the other hand, if the occurrence of the displacement of the first lens 1 is expressed by a mathematical expression,
Assuming that the first lens 1 is displaced by γ from a predetermined position in the optical axis direction, the beam waist (the spot size W _LD ′) after emission from the first lens 1 is expressed in the optical axis direction by the following formula:
The position is shifted by Z.

ΔZ = −m ² γ (1) where m is the image magnification of the spot size of the semiconductor laser by the first lens 1 and is expressed by the following equation (2).

m = W _LD ′ / W _LD (2) If the spot size becomes too large, the tolerance of the angle shift becomes strict. Therefore, in the pseudo-confocal system, the image magnification is generally selected to be about 13 to 20. Usually, the spot size W _LD of the semiconductor laser 10 is about 1 μm, so that the spot size W _LD ′ of the beam waist is about 13 μm to 20 μm.

In the manufacture of the semiconductor laser module, the semiconductor laser 1 is bonded to the stem 9 as described above, and in this case, it is practically about ± 10 μm in the optical axis direction with respect to a desired fixed position.
m (that is, γ = ± 10 μm). In the pseudo-confocal system, it is difficult to adjust the first lens 1 to a predetermined position in the optical axis direction due to the structure of the semiconductor module.

As a result, in the conventional fixing method in the quasi-confocal system, the spread of the beam after exiting the first lens 1 varies due to the variation in the displacement of the first lens 1, and the light exiting system including the first lens 1 is displaced. On the other hand, the optimal position of the virtual fiber, which is the integrated portion, varies from ± 1.69 mm to ± 4 mm in the optical axis direction. However, this displacement causes a problem that the virtual fiber comes out of the guide 7 of the integrated holder in the optical axis direction.

In addition, the manufacturing defect of the semiconductor laser module causes a problem that the yield of the laser module using the expensive communication semiconductor laser is deteriorated.

Further, when positioning the integrated portion that compensates for the positional deviation based on the positional deviation of the first lens 1 described above,
Also a problem of the optical coupling efficiency of the alignment of the spot size W _LD 'and the integrated portion spot size W _F' of the first lens 1 is not taken.

FIG. 2 shows a quasi-confocal semiconductor laser module, which has been described based on it.
A semiconductor laser module using the second lens division type confocal compound lens system shown in FIG. 4 can also be said. FIG. 4 shows the second
Lens split type confocal compound lens based semiconductor laser module [Kawano et al .: Laser diode module for singie-mode fiber
r based on new confocal combination lens method: IE
EE Journal of Lightwave Technol.vol.LT-4, pp.1407,
1986] is shown. In this second lens split type confocal compound lens system, the light is converted into substantially parallel light by the first lens 1 which is a spherical lens disposed at a position substantially in focus with respect to the optical semiconductor laser 10 emitted from the semiconductor laser 10. . This parallel light is converted into a beam of the same degree as the beam after the first lens in the quasi-confocal system shown in FIG. 1 by the second lens 2 which is a GRIN rod lens. That is, the optical coupling of the second lens splitting system is performed by the beam narrowed by the second lens 2 and the third lens (GRIN rod lens) 3 and the single mode optical fiber 4 as in the case of the pseudo-confocal system. It can be considered as coupling with a virtual fiber.

In the case of the second lens splitting system, the setting error γ of the mutual position of the semiconductor laser 10 and the first lens 1 in the optical axis direction and the displacement of the beam waist after emitting the second lens 2 in the optical axis direction ΔZ Is given by equation (1) as in the case of the pseudo-confocal system. The effect of the setting error in the optical axis direction of the first lens 1 becomes important in the second lens division system as in the pseudo-confocal system. In addition, a problem similar to that of the pseudo co-end point system occurs.

The present invention has been made in view of the above-described problems, and provides a method of fixing an optical coupling system that eliminates a decrease in yield and coupling efficiency, which is an effect of a positional shift between a light emitting element and a first lens in an optical axis direction. For the purpose of providing.

<Means for Solving the Problems> The configuration of the present invention that achieves the above object has the following features.

1) A lens fixed to an integrated holder, and a single mode fiber fixed to a core, wherein the core is a virtual fiber formed so as to be movable with respect to the integrated holder. In the method of adjusting the position of the single-mode fiber in the optical axis direction and fixing the integrated holder in the plane while moving the single mode fiber in the optical axis direction, the maximum coupling efficiency with respect to the light emission system is increased. Fixing after adjusting the position to the state that can be obtained.

2) a lens fixed to an integrated holder, and a single mode fiber fixed to a core, wherein the core is a light emitting element formed by moving a virtual fiber formed to be movable with respect to the integrated holder; In the method of adjusting the position and fixing the light emitting system to the light emitting system, the light emitting element, the first lens, and the virtual fiber are arranged in this order, and the distance between the light emitting element and the first lens is set to the first distance. By arranging the light beam to be larger or smaller than the focal length of one lens, the light beam emitted from the light emitting element is formed as a convergent beam after the light beam is emitted from the first lens. Fixing the emitting element to the stem, then fixing the position of the first lens with respect to the light emitting element, and adjusting the integrated holder in-plane while moving the single mode fiber in the optical axis direction. Fixed to it after position adjustment state maximum coupling efficiency is obtained Ri to the light emitting system.

3) A lens fixed to an integrated holder, and a single mode fiber fixed to a core, wherein the core is a light emitting element formed by a virtual fiber movably formed with respect to the integrated holder. In the method of adjusting the position and fixing the light emitting system to the light emitting system, the light emitting element, the first lens, and the virtual fiber are arranged in this order, and the distance between the light emitting element and the first lens is set to the first distance. By arranging them so as to be close to the focal length of one lens, a light beam emitted from the light emitting element is formed as a substantially parallel beam after emitting the first lens, and a convergent beam or divergent beam after emitting the second lens. In the optical coupling system formed as a squeezed beam, after fixing the light emitting element to the stem, fixing the position of the first lens with respect to the light emitting element; While moving in the optical axis direction is fixed after positioning in a state of maximum coupling efficiency is obtained with respect to the light exit system by adjusting the integrated holder plane that the.

4) a lens fixed to an integrated holder, and a single mode fiber fixed to a core, wherein the core is a virtual fiber formed so as to be movable with respect to the integrated holder; In the method of adjusting the position and fixing the light emitting system, the light emitting element, the first lens, the second lens, and the virtual fiber are arranged in this order, and the light emitting element and the first lens are By arranging the distance so as to be substantially equal to the focal length of the first lens, a light beam emitted from the light emitting element is formed as a substantially parallel beam after the light is emitted from the first lens. Fixing the element to the stem, then fixing the position of the first lens with respect to the light emitting element, and adjusting the integrated holder in-plane while moving the single mode fiber in the optical axis direction. It is fixed after positioning in a state of maximum coupling efficiency is obtained with respect to the light exit system.

5) In any one of the above 1) to 3), the arrangement of the light emitting element and the light incident element is interchanged.

<Operation> In the present invention, since the virtual fiber in which the optical axis of the lens and the single mode fiber coincide with each other via the integrated holder and the core is used, the first lens is aligned with the light emitting element. After fixing, the single mode fiber is aligned in the optical axis direction, and the core is fixed to the integrated holder.
The fixing of the optical coupling system is completed only by a two-step alignment fixing operation of aligning the entire virtual fiber in the direction perpendicular to the optical axis of the first lens and fixing the integrated holder.

<Embodiment> An embodiment of the present invention will now be described with reference to FIG. FIG. 1 is a schematic view of a quasi-confocal semiconductor laser module. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals. That is, 10 is a semiconductor laser which is a part of a light emitting system, 1 is a first lens which is a spherical GRIN rod lens, 2 is a second lens which is a GRIN rod lens, and 4 is a single mode light which is a light incident element. The fiber 5 is a core, 6 is an integrated holder, 8 is a nylon cord, and 9 is a stem.

The manufacture of such a semiconductor laser module is the same as the conventional method until the semiconductor laser 10 is fixed to the stem 9 and the first lens 1 is fixed.

The fixing of the integrated portion to such a light emitting system is different from the conventional one. That is, first, the second lens 2 is fixed to the integrated holder 6. While the second lens 2 fixed to the integrated holder 6 exists, the single mode optical fiber 4 fixed to the core 5 can move with respect to the integrated holder 6.

Then, by moving the single-mode optical fiber 4 in the direction of the optical axis within the core 5 and adjusting the integrated holder 6 in-plane, a state is obtained in which the maximum coupling efficiency with respect to the light emitting system can be obtained. In this state, the core 5 is fixed to the integrated holder 6.

As a result, the relative position of the second lens 2 and the single mode optical fiber 4 in the optical axis direction is determined, and a virtual fiber is formed by the second lens 2 and the single mode optical fiber 4. Here, even in the present embodiment, the fixing of the first lens 1 is the same as the conventional method, so that the position setting error γ of the first lens 1 in the optical axis direction is about ± 10 μm.

However, in this example, since the position of the single mode optical fiber 4 can be adjusted in the optical axis direction, the image magnification m of the above equation (1) is changed to the spot size of the single mode optical fiber 4.
W W When _F and, for example, 5.5μm to W _LD as 1 [mu] m _LD '/ W
_LD = m can be set to m = 5.5, and m can be made very small as compared with the conventional case.
ΔZ becomes ± 300 μm, and the setting error in the optical axis direction by the first lens 1 can be easily eliminated.

Also in this case, since the tolerance of the single-mode optical fiber 4 for the axial deviation is loose, for example, laser welding or the like can be applied to fix the single-mode optical fiber 4.

The virtual fiber of the single mode optical fiber 4 and the second lens 2 integrated by the integration holder 6 is thereafter fixed in position in the direction perpendicular to the optical axis, and a semiconductor laser module is manufactured.

FIG. 1 shows the quasi-confocal system, but also in the case of the second lens division system shown in FIG.
The present invention can be applied. Also, although not shown, in the case of integrating the lens and the single mode optical fiber in the conventional confocal compound lens system using the first lens and the second lens and the beam between the lenses is almost parallel light, The present invention can be applied.

It should be noted that even in configurations other than the quasi-confocal system, the second lens-divided confocal system, and the conventional confocal system, any optical coupling system using a virtual fiber in which a lens and a single mode optical fiber are integrated can be used. The invention can be applied. Further, the case where a single mode optical fiber is used as the light incident element has been described, but it goes without saying that the same applies to the case where an optical waveguide is used.

In the above example, the case where a semiconductor laser is used as the light emitting element has been described. However, the same applies to other light emitting elements such as a semiconductor optical waveguide such as a light modulation element.

Further, the present invention can be applied to a configuration in which the optical fiber is not used as a light incident element, and light emitted from the optical fiber is incident on a light receiving element via a lens.

<Effects of the Invention> According to the present invention as described in the above embodiments, since the position of the light incident element is adjusted with respect to the lens, the light is emitted without greatly displacing the entire virtual fiber in the optical axis direction. It can be coupled to the incident element, so that the module yield as a product is improved and the coupling efficiency is not deteriorated. After the fixing, the virtual fiber is formed after the lens and the light incident element are fixed. Therefore, the effect of reducing the tolerance of the axial deviation due to the enlargement of the spot size can be maintained as it is.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a quasi-confocal semiconductor laser module manufactured by a fixing method according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a quasi-confocal semiconductor laser module manufactured by a conventional fixing method. FIG. 3 is a diagram for explaining the principle of the pseudo-confocal system, and FIG. 4 is a configuration diagram of a second lens-divided confocal semiconductor laser module manufactured by a conventional fixing method. In the figure, 1 is a first lens in a pseudo-confocal system or a second lens division system, 2 is a second lens, 3 is a third lens in a second lens division system, 4 is a single mode optical fiber, and 5 is a core. , 6
Is an integrated holder, 7 is a guide for the integrated holder, 8 is a nylon cord, 9 is a stem, and 10 is a semiconductor laser.

Claims (5)

(57) [Claims] 1. A lens comprising: a lens fixed to an integrated holder; and a single mode fiber fixed to a core, wherein the core includes a virtual fiber movably formed with respect to the integrated holder. In the method for adjusting the position of the single-mode fiber in the optical axis direction while fixing the position to the light-emitting system having the light-emitting element, by adjusting the integrated holder in-plane while moving the single mode fiber in the optical axis direction, A method for fixing an optical coupling system, wherein the optical coupling system is fixed after adjusting the position so that coupling efficiency is obtained. 2. A virtual fiber, comprising: a lens fixed to an integrated holder; and a single mode fiber fixed to a core, wherein the core includes a virtual fiber movably formed with respect to the integrated holder. In a method of adjusting the position of a light emitting element having a light emitting element and fixing the light emitting element, a light emitting element, a first lens, and the virtual fiber are arranged in this order, and a distance between the light emitting element and the first lens. Is arranged so as to be larger or smaller than the focal length of the first lens, so that a light beam emitted from the light emitting element is formed as a convergent beam after exiting the first lens. Fixing the light emitting element to the stem, then fixing the position of the first lens with respect to the light emitting element, and adjusting the integrated holder in-plane while moving the single mode fiber in the optical axis direction. Optical coupling system fixing method, characterized in that to fix after position adjustment state maximum coupling efficiency is obtained with respect to the light exit system by. 3. A lens fixed to an integrated holder and a single mode fiber fixed to a core, wherein the core includes a virtual fiber movably formed with respect to the integrated holder. In the method of adjusting the position of the light emitting element having the light emitting element and fixing the light emitting element, the light emitting element, the first lens, the second lens, and the virtual fiber are arranged in this order, and the light emitting element and the first By arranging the lens so as to be closer to the focal length of the first lens, a light beam emitted from the light emitting element is formed as a substantially parallel beam after the first lens is emitted, and the light emitted from the second lens is emitted. After fixing the light emitting element to a stem in an optical coupling system formed later as a convergent beam or a divergent beam, the first
By fixing the position of the lens with respect to the light emitting element and moving the single mode fiber in the optical axis direction and adjusting the integrated holder in-plane, the maximum coupling efficiency with respect to the light emitting system can be obtained. A method for fixing an optical coupling system, comprising: adjusting the position after adjusting the position; 4. A lens comprising: a lens fixed to an integrated holder; and a single mode fiber fixed to a core, wherein the core includes a virtual fiber movably formed with respect to the integrated holder. In a method of adjusting the position of a light emitting element having a light emitting element and fixing the light emitting element, a light emitting element, a first lens, and the virtual fiber are arranged in this order, and a distance between the light emitting element and the first lens. Is disposed so as to be substantially the focal length of the first lens, so that the light beam emitted from the light emitting element is formed as a substantially parallel beam after exiting the first lens. Is fixed to the stem, then the first lens is fixed in position with respect to the light emitting element, and the integrated holder is adjusted in-plane while moving the single mode fiber in the optical axis direction. Optical coupling system fixing method, characterized in that to fix after position adjustment state maximum coupling efficiency is obtained with respect to the light emitting system. 5. The method for fixing an optical coupling system according to claim 1, wherein the arrangement of the light emitting element and the light incident element is changed.