JPH0447982Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention relates to a multi-output laser module, and in particular aims to improve the coupling efficiency between a semiconductor laser diode (hereinafter referred to as LD) and multiple optical fibers. Regarding the laser module that can be used.

[Prior Art] Fig. 2 shows a conventional example of a 7-distribution module that simultaneously couples laser light from an LD chip to seven multimode optical fibers. The LD chip 21 is mounted on a disk-shaped LD stem 22 and hermetically sealed by a cap 24 with a glass window 23, and this LD stem 22 is fixed within a guide sleeve 25.

On the other hand, the nylon coating on the tips of the seven optical fibers 26 is removed, and the optical fibers 26 are converged into a 1-6 configuration with one fiber in the center and six fibers around it.
is inserted and fixed into the optical fiber holder 28.

After mirror-polishing the distal end surface of the optical fiber bundle 27 inserted into the optical fiber holder 28, the optical fiber holder 28 and the guide sleeve 25 are each held by a fine movement device, and the optical fiber holder 2
8 inserted into the guide sleeve 25, the optical axes of the LD chip 21 and the optical fiber bundle 27 are aligned using a fine adjustment device. Once the optical axes have been aligned, the resin between the optical fiber holder 28 and the guide sleeve 25 is cured.

In a laser module with such a configuration,
After the laser light emitted from the LD chip 21 passes through the glass window 23 of the cap 24, it enters the mirror-polished end face of the optical fiber bundle 27 and is distributed to each fiber 26.

[Problems that the invention attempts to solve] By the way, LDs are easily affected by return light;
It is known that when a reflective surface exists near the LD output end face, the reflected light returns to the LD, making the LD's oscillation state unstable. For example, when the distance between the LD output end face and the reflective surface is 0.4 mm or more, the optical output fluctuation of the LD is within 0.1 dB, and the noise (relative noise intensity) of the output light is about -130 dB/Hz. If the spacing is within 0.4mm, the optical output fluctuation will be ±1dB,
The noise of the output light reaches -100dB/Hz.
Therefore, the distance between the LD chip 21 and the glass window 23 has conventionally been set to about 0.4 mm or more.

In addition, since the glass window 23 of the cap 24 needs to have a thickness of about 0.2 mm from the viewpoint of strength, the distance between the glass window 23 and the end surface of the optical fiber bundle 27 should be adjusted.
When configuring the laser module as 0.1mm, the LD
The distance from the chip 21 to the end surface of the optical fiber bundle 27 is 0.7 mm or more.

However, the LD chip 21 and the optical fiber 2
In order to improve the coupling efficiency with the optical fiber bundle 27 and increase the optical input to each fiber, it is desirable to bring the tip end of the optical fiber bundle 27 as close as possible to the LD chip 21, and as mentioned above, the distance between the two should be set at 0.7 mm. There was a problem that the coupling efficiency decreased when the value was set to a value higher than that.

Thus, an object of the present invention is to provide a multi-output laser module that can solve the problems of the prior art described above and improve the coupling efficiency while stably maintaining the oscillation state of the LD.

[Means for Solving the Problems] In order to achieve the above object, the multi-output laser module of the present invention is a multi-output laser module that couples a plurality of multi-mode optical fibers to a semiconductor laser diode and distributes the optical output in multiple ways. In the laser module, an optical fiber holder that focuses and inserts and fixes the tip portions of the plurality of optical fibers from which the coating material has been removed; a glass thin film formed on the tip surface of the optical fiber holder; A guide that surrounds the outer periphery of the optical fiber holder and extends forward by a predetermined length from the distal end surface of the optical fiber holder, and the rear end portion and the outer circumferential surface of the optical fiber holder are sealed. The guide sleeve includes a sleeve, and a laser diode stem on which the laser diode is mounted and whose peripheral edge and the front end of the guide sleeve are sealed.

[Function] Since the thickness of the glass thin film can be set to be extremely thin, approximately 1 to 50 μm, the above configuration allows the LD chip to be hermetically sealed while also connecting the output end face of the LD chip and the input of the optical fiber. By reducing the distance from the end face, this distance can be set to about 0.4 mm, the minimum value at which the LD can stably oscillate.

The glass thin film has two purposes: to ensure airtightness between the optical fiber holder and the outside through the optical fiber bundle inserted therein, and to reduce the reflectance of laser light at the input end face of the optical fiber. have. Therefore, in order to achieve this objective, it is desirable to use a material such as SiO ₂ or MgF ₂ as the glass thin film, which has a lower refractive index than the core of the optical fiber and is transparent in the emission wavelength range of the _LD . A multilayer film such as /TiO ₂ or MgF ₂ /ZnS may be used as an anti-reflection coating.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing the configuration of a multi-output laser module according to an embodiment of the present invention. This embodiment is a seven-output laser module that uses an LD chip 1 as a light emitting element and obtains output from seven multimode optical fibers 2. LD chip 1 is disc-shaped
It is installed on the LD stem 3, and the peripheral edge of the LD stem 3 is fixed to one surface of the ring 4.
A front end surface of a guide sleeve 5 is joined to the other surface of the ring 4, and an optical fiber holder 6 is inserted and fixed into the guide sleeve 5 from its rear end. Seven optical fibers 2 from which the coating material on the tips have been removed are inserted into the optical fiber holder 6 in a bundle, and the optical fiber bundle 7 is inserted onto the tip surface of the optical fiber holder 6 through which it is guided. glass thin film 8
is formed.

A laser module having such a configuration is created as follows.

First, after removing the nylon coating at the tip of each of the seven 50/125GI optical fibers 2, these were focused in a 1-6 configuration with one fiber in the center and six fibers around it.
The optical fiber bundle 7 at the tip is inserted into the optical fiber holder 6 so that it reaches the tip surface of the optical fiber holder 6 and fixed with resin 9. Furthermore, the end surfaces of the optical fiber holder 6 and the optical fiber bundle 7 are mirror-polished, and a glass thin film 8 made of SiO ₂ is formed on the polished surfaces to a thickness of about 1 to 50 μm by vapor deposition.
This glass thin film 8 covers the tip surface of the optical fiber holder 6, the tip surface of the optical fiber bundle 7, and the optical fiber bundle 7.
It covers the end face of the resin 9 on which the is fixed.

On the other hand, install LD chip 1 on LD stem 3,
The entire periphery of this LD stem 3 is welded to the ring 4. In this case, electric resistance welding, high frequency heating welding, YAG laser welding, _CO2 laser welding, etc. can be used.

Next, the optical axes of the LD chip 1 and the optical fiber bundle 7 are aligned, and the distance between them is set to 0.4 mm.
It was set to First, the optical fiber holder 6 is inserted into the guide sleeve 5, and with the front end surface of the guide sleeve 5 in contact with the ring 4, the optical fiber holder 6 inside the guide sleeve 5 is slightly moved back and forth.
The optical fiber holder 6 and the guide sleeve 5 are fixed by welding over the entire circumference, with the distance between the LD chip 1 and the end face of the optical fiber bundle 7 being 0.4 mm. Next, the guide sleeve 5 is slightly moved up and down to align the optical axes of the LD chip 1 and the optical fiber bundle 7, and when the optical axes are aligned, the guide sleeve 5 is moved slightly up and down.
and ring 4 are welded over the entire circumference thereof.

Welding of this guide sleeve 5 and ring 4 and the above-mentioned optical fiber holder 6 and guide sleeve 5
YAG laser welding or CO ₂ laser welding is used for welding. This is done in consideration of the fact that it is a non-contact type and that the temperature of the entire laser module is not increased due to local welding, and to reduce the amount of axis deviation after welding.

In this way, the deviation of the optical axes between the LD chip 1 and the optical fiber bundle 7 before and after welding is within 10 μm, and the interval is 0.4 μm.
We were able to assemble the laser module with mm deviations within 50 μm.

Here, LD chip 1 welds between LD stem 3 and ring 4, welds between ring 4 and guide sleeve 5,
The guide sleeve 5 and the optical fiber holder 6 are hermetically sealed by welding and a glass thin film 8.

When the output of the 7-output laser module of this embodiment was measured, it was confirmed that the output was increased by about 5 dB compared to the conventional example shown in FIG. 2, which uses the same chip as LD chip 1.

Note that the ring 4 may be omitted and the LD stem 3 may be directly welded to the front end surface of the guide sleeve 5 by YAG laser welding or CO ₂ laser welding.

In addition to SiO ₂ , the glass thin film 8 also contains MgF ₂ , SiO ₂ /
It may be composed of TiO ₂ or MgF ₂ /ZnS,
A sputtering method or an ion plating method can also be used as a forming method.

Furthermore, although the above embodiment describes a laser module with seven outputs, the laser module is not limited to seven outputs, and may have more or fewer outputs.

[Effects of the invention] As explained above, according to the present invention, the following excellent effects are achieved.

(1) While the LD chip is hermetically sealed, the distance between the LD chip output end face and the optical fiber input end face is set to 0.4
By setting it to about mm, it is possible to improve the coupling efficiency while stably maintaining the oscillation state of the LD chip.

(2) Therefore, the multi-output laser module according to the present invention can obtain high output power and is highly useful for application to various optical communication systems.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a multi-output laser module according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a conventional example. In the figure, 1 is a laser diode chip, 2 is an optical fiber, 3 is a laser diode stem, 4 is a ring, 5 is a guide sleeve, 6 is an optical fiber holder, 7 is an optical fiber bundle, and 8 is a glass thin film.

Claims (1)

[Claims for Utility Model Registration] (1) In a multi-output laser module that couples a plurality of multi-mode optical fibers to a semiconductor laser diode and multi-distributes optical output, the plurality of optical fibers from which the coating material has been removed an optical fiber holder that focuses the tip of the fiber and inserts and fixes it;
a glass thin film formed on the tip surface of the optical fiber holder; A guide sleeve whose end portion and the outer peripheral surface of the optical fiber holder are sealed; and a laser diode stem on which the laser diode is mounted and whose peripheral portion and the front end of the guide sleeve are sealed. A multi-output laser module characterized by: (2) The above glass thin film is composed of MgF ₂ , SiO ₂ , MgF ₂ /
A multi-output laser module according to claim 1, characterized in that it is made of ZnS or SiO ₂ /TiO ₂ . (3) Sealing between the rear end of the guide sleeve and the outer peripheral surface of the optical fiber holder, and between the front end surface of the guide sleeve and the peripheral edge of the laser diode stem are performed by YAG laser welding or
3. The multi-output laser module according to claim 1 or 2, characterized in that it is made by CO ₂ laser welding.