JPS63318508A - Optical fiber coupling module - Google Patents

Abstract

PURPOSE:To always obtain maximum coupling efficiency by observing reflected light from the end face of an optical fiber worked as a specific shape to position a light converging means. CONSTITUTION:A flat part 11 having about 10 deg. inclination to separate incident light 5 from a semiconductor laser 1 from reflected light 6 and a core part 10 having a projected shape are formed on the end face of the optical fiber 4 and the height of the projected part is 1/4 wavelength lambda or the odd times of lambda/4. When a part having a different height corresponding to 1/4 wavelength lambdais formed of the focus position of the light converging means like an optical pickup on an optical disk, etc., reflected light goes to a Fourier-transformed shape and a positioning control signal is obtained by a divided photodetector based on a method called push-pull method. When a cylindrical lens is arranged between the four-divided photodetector and the end face of the optical fiber, a focusing control signal can be obtained by astigmatism method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser and optical fiber coupling module.

BACKGROUND OF THE INVENTION When coupling a semiconductor laser to an optical fiber, the light emitted from the semiconductor laser typically has a divergence angle of 20 degrees. In order to efficiently couple with optical fiber, (
Methods include 1) installing a focusing lens between the semiconductor laser and the optical fiber, (2) attaching a microlens to the tip of the optical fiber, and (3) shaping the tip of the optical fiber into a lens shape. It has been thought of. However, in either case, it is necessary to fix the optical fiber at a position where maximum coupling efficiency can be obtained. Therefore, as shown in FIG. 3, the light emitted from the semiconductor laser 101 is transmitted to the ball lens 10.
2 and enters the core portion of the optical fiber 103. In order to fix the tip of the optical fiber, a ceramic ferrule 104 is generally used.
It is fixed with.

The stem is divided into 3 parts, each stem A1os.

Stem B106. If stem C107 is used, stem A1
An electrode lead 108 is passed through and attached to the ots. The ball lens 102 is aligned and fixed with respect to the semiconductor laser by the positions of the stem AlO3 and the stem B106. Furthermore, stem B106 and stem C107
A method has been adopted in which the optical fiber 103 is fixed so as to be focused depending on its position.

Problems to be Solved by the Invention In FIG. 3, the optical fiber 103 is a semiconductor laser 1o1.
After positioning is performed to maximize the light coupling efficiency, the fixing agent is (1) polymeric fat adhesive or solder, or (2) fixing.
In some cases, the parts are fixed by welding, but in either case, the position may shift by 1 μm or more during fixation, making it difficult to manufacture a coupling module with maximum coupling efficiency.

Furthermore, there is a problem in that the multi-coupling efficiency changes due to temperature changes during use.

Means for solving the problem The technical means for solving the above problem is to separate the incident light and the reflected light into the optical fiber by processing the end of the optical fiber diagonally. By making only the core portion of the optical fiber convex by a quarter wavelength or an odd multiple of a quarter wavelength, and by observing the reflected light from the end face of the processed optical fiber, light focusing can be achieved. Feedback control is performed so that the maximum coupling efficiency is always obtained by aligning the means.

Effects The effects of this technical means are as follows. That is, as seen in optical pickups such as optical discs, by providing portions that differ in height by a quarter wavelength at the focal point of the light focusing means, the reflected light has a shape that has been subjected to 7-lier transformation. For example, a control signal for alignment can be obtained using a method called a push-pull method using divided photodetectors. Further, by installing a cylindrical lens between the four-divided photodetector and the end face of the optical fiber, a control signal for focus positioning can be obtained by the astigmatism method.

Embodiment Hereinafter, an optical fiber coupling module according to an embodiment of the present invention will be explained based on the accompanying drawings.

FIG. 1 is a perspective view of the module of the same embodiment.

Laser light 2 emitted from semiconductor laser 1 is focused by rod lens 3 and enters the core portion of optical fiber 4 . The end face of the optical fiber 4 is obliquely processed to have an inclination of about 10 degrees in order to separate the incident light 6 and the reflected light 6. The reflected light 6 from the optical fiber is configured to pass through an imaging lens 7 and a cylindrical lens 8 and enter a four-split photodetector.

The optical fiber 4 has, for example, a wavelength of 1.
In the case of O7 single mode fiber for 3 μm band, the diameter is 1
The diameter of the core portion 10 is approximately 10 μm.
It is. As shown in FIG. 2, the end face of the optical fiber 4 is formed with a flat portion 11 having an inclination angle of θ=11° and a convex core portion 1o. Only the core portion of the optical fiber 4 has a convex shape, and the height of the convex portion is set to be a percentage of the wavelength λ or an odd multiple of λ/4. Further, a flat portion 11 around the core portion 1o is a square with a side of 20/Im, and a cladding portion outside the flat portion is processed into a square pyramid shape 12.

As shown in FIG. 1, the optical fiber 4 is configured so that its movement can be controlled in three-dimensional directions by an actuator 13 using an electromagnet, a piezo element, or the like. Furthermore, four photodetectors 14 are installed facing the four surfaces of the quadrangular pyramid-shaped cladding 12 to prevent the focal position of the incident light 6 from shifting on the end surface of the optical fiber 4 other than the flat portion 11. If this occurs, the opposing photodetector 14
The structure is such that the incident light 6 is incident on one of the two. Further, a reflective film may be formed on the quadrangular pyramid-shaped cladding 12 in order to guide more incident light to the photodetector.

First, regarding the principle of focus alignment, the reflected light 6 from the optical fiber 4 is incident on the 4-split photodetector 9 through the cylindrical lens 8, but when it is focused due to the astigmatism caused by the cylindrical lens 8, A perfect circular image is formed on the split detector and the four alignment signals 16 are equal.

If closer or further away, 9 o each.
Since images of Sui circles with different degrees are formed, it is possible to determine whether the image is near or far from the focal point, and the focal position is adjusted by the actuator so that the sum of the output signals of the two opposing elements of the 4-split photodetector 60 is equal. It can be carried out.

The diffraction pattern due to the convex core portion 1o of the optical fiber 4 changes depending on the positional relationship between the core portion and the focal point. When the focus is on the core part, the diffracted light intensity distribution detected by the 4-split photodetector 9 is symmetrical, but if the focus is biased to either side, it becomes asymmetrical. Positioning can be performed by the actuator 13 so that the sum of the output signals of two adjacent elements of the four-division photodetector 9 is equal.

Furthermore, if the light focusing means is significantly displaced due to disturbance or the like and exceeds the position adjustment range of the 4-split detector 6, the flat portion 11 on the end face of the optical fiber 4 should be made smaller than the position adjustment range. By doing so, the focal point of the incident light 6 is incident on one side of the square pyramid shape 12 of the optical fiber 4, so that the light is incident on one element of the four photodetectors 14 provided facing each other. Therefore, the four coarse movement signals 1
6, a control signal for correcting the direction of deviation can be obtained, and the actuator 13 is used to pull the optical fiber back to a position adjustment range where highly accurate positioning can be performed by the push-pull method. I can do it.

Therefore, for large positional deviations of the light focusing means due to disturbances, etc., coarse movement signals from the four photodetectors 14 can be used, and for more accurate focusing and positioning, refer to the 4-split photodetector edition. It is possible to correct each position according to the positioning signal of .

Note that the reason why only the core portion 1o of the optical fiber 4 is made convex by an odd number multiple of wavelength λ or λ/4 is that although the same alignment method can be used even if it is a concave shape, it is better to use a convex shape. This is because the effective apertures N and A of the optical fiber can be increased, and the light coupling efficiency can be increased.

Furthermore, by processing the end face of the optical fiber 4 obliquely, the amount of reflected light from the optical fiber 4 returning to the semiconductor laser 1 can be reduced, so that the emission noise of the semiconductor laser 1 is not increased.

Effects of the Invention When manufacturing an optical fiber coupling module, it becomes easy to align the optical components when attaching them, and it is possible to eliminate the influence of positional deviation when fixing the components on the coupling efficiency. Furthermore, the effects of temperature changes during use can be eliminated, and a stable optical fiber coupling module with high coupling efficiency can be constructed.

[Brief explanation of drawings]

FIG. 1 shows an optical fiber according to an embodiment of the present invention. FIG. 1 is a sectional view of a conventional optical fiber coupling module. 1... Semiconductor laser, 3... Light focusing lens, 4... Optical fiber, 7... Imaging lens, 8... Cylindrical Lens, 9...
...4-split photodetector, 13... actuator, 14... photodetector. Name of agent: Patent attorney Toshio Nakao and 1 other person
3 Figure rot-hand nose body lede insole lens end fiber ferrule Stem A Stem B Stem C Electric lead

Claims (3)

[Claims] (1) Focus the emitted light from a semiconductor laser onto the end face of an optical fiber in which only the core portion is convex with respect to the cladding portion by a height of a quarter wavelength or an odd multiple of a quarter wavelength. An optical fiber coupling module comprising a light focusing means, a light separating means for separating the reflected light from the optical fiber from the incident light, and a means for aligning the light focusing means using the reflected light. . (2) The optical fiber coupling module according to claim 1, wherein the optical fiber coupling module is a means for separating incident light and reflected light by tilting the light incident end face of the optical fiber. (3) A patent in which the light incident end face of the optical fiber is shaped like a square pyramid, a photodetector is installed at a position facing the four slopes of the square pyramid, and the position of the light focusing means is aligned based on the signal from the photodetector. An optical fiber coupling module according to claim 1.