JPS6144296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber device in which the optical fiber itself has active functions such as branching and optical coupling.

In general, optical fibers that can transmit light with high efficiency are considered promising as optical communication networks in optical communication systems, and for this purpose, it is necessary to perform optical branching and optical coupling at the optical fiber portion.

Conventionally, as a means of optical coupling using optical fibers, for example, as shown in FIG. As shown in FIG. 2, the branching and joining means employs a method in which the sides of the two optical fibers 3 and 4 are polished and cut, and the two are joined at that surface.

However, these conventional optical coupling and branching means using optical fibers are merely optical coupling paths and optical branching paths formed in an optical transmission path.
It does not have any active function that can adjust the degree of optical coupling and optical branching.

There is still no functionalized optical fiber itself, so conventionally, as shown in FIG. However, at present, functions such as optical switching and selective branching are performed in the optical waveguide 5 portion.
Note that 7 in the figure indicates a control device that controls the optical waveguide 5. However, such a thin film optical waveguide 5
When trying to apply this to a communication network using optical fibers, a method for efficiently directly joining the optical fiber 6 and the thin film optical waveguide 5 has not yet been established, so light reflection at the joint becomes a problem. Since a separate optical coupler is required, the device as a whole becomes complicated. In addition, the film thickness of a thin film optical waveguide is only about a few μm, and requirements for alignment for optical coupling and flatness of the end face of the optical fiber are extremely strict, making it practically impossible to obtain highly reliable coupling efficiency. It's becoming a difficult problem.

The present invention has been made in consideration of the above points, and
The optical fiber itself, which conventionally only served as an optical transmission path, can now branch or split light in response to external control signals.
An object of the present invention is to provide an optical fiber device that is simple in structure and easy to manufacture and allows the degree of optical coupling to be adjusted.

The optical fiber device according to the present invention has a transducer formed at one end of the optical fiber that can propagate ultrasonic waves into the optical fiber, and changes the propagation constant of the light waves in the optical fiber by the ultrasonic waves, In order to arbitrarily adjust the degree of optical branching and optical coupling between optical fibers while satisfying the phase matching condition, and to make the device itself easy to manufacture and reliable, optical fibers are embedded in resin and polished as one unit. Adopting a processing method to facilitate the alignment of joints,
The optical loss in that part is suppressed as much as possible to increase the degree of coupling.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the optical fiber device according to the present invention, as shown in FIG. The two optical fibers 10 and 11 are joined together with the resins 8 and 9 at the converted portion L (the optical fibers 10 and 11 are formed so that they do not contact each other except at the L portion), and the optical fiber 10 is It is composed of an ultrasonic transducer 12 attached to one of the extraction points from the resin 8 using the surface of the resin 8, and an AC variable power source 13 that drives the transducer 12.

In the optical fiber device according to the present invention configured as described above, an excitation voltage is applied to the transducer 12 to excite it while transmitting light from the input ends A and C of the optical fibers 10 and 11, respectively. When an ultrasonic signal S is sent into the optical fiber 10 along the propagation direction of the light, the propagation constant ka of the light passing through the optical fiber 10 is k=ka±K (K: ultrasonic wave) due to the propagation of the ultrasonic signal S. propagation constant of signal S). Therefore, the optical fiber 11
If the propagation constant of light at
It will be transferred to the first side. At this time, the length L of the joint between the optical fibers 10 and 11 is L=
It is set to have a perfect bond length determined by c/2π. Therefore, in such an optical fiber device, the AC variable power supply 13
By controlling the magnitude of the output of the ultrasonic signal S oscillated from the transducer 12 or changing its frequency, that is, by changing the value of K, the output end D of the optical fiber 11 is The transmitted light can be changed according to the degree of the ultrasonic signal S, and the optical fiber itself can have an active function of arbitrarily adjusting the degree of optical branching and optical coupling. Note that the ultrasonic signal S is transmitted only to the optical fiber 10 portion,
There is almost no excitation in the resin 8 portion, and the attenuation of the ultrasonic signal S due to the presence of the resin 8 is almost negligible.

FIG. 5 shows one manufacturing process of the optical fiber device according to the present invention as explained above.
As shown in , in the present invention, the outer diameter is 150
An optical fiber 10 (which may be a single or multimode fiber, or a step-index type or graded-index type fiber) of approximately 200 μm is bent into a predetermined shape and placed in the resin 8. Embed and solidify. One of the optical fibers does not have to be bent. Furthermore, it is more efficient if the ultrasonic waves are propagated to the side of the fiber that is not bent. Next, as shown in FIG.
Perform polishing treatment up to step m). Next, as shown in FIG. 3c, an ultrasonic transducer 12 is formed on one end surface of the optical fiber 10. This ultrasonic transducer 12 has a thin film 12 formed between electrodes 121 and 122 by sputtering ZnO, for example.
3 (approximately 1 to 5 .mu.m), and the electrodes 121 and 122 are formed by laminating, for example, Al or the like to a thickness of several thousand angstroms by vapor deposition. When it is necessary to connect another optical fiber to the ultrasonic transducer 12, the electrodes 121 and 122 are made transparent. Further, if the ZnO thin film 123 has a thickness of about 1 to 5 μm over the visible and near infrared regions, light absorption in that portion can be ignored. Further, the formation of the ultrasonic transducer 12 is performed using the optical fiber 1.
Although it is somewhat difficult because the outer diameter of the optical fiber 10 is very small, about 150 to 200 μm, in this case, as shown in FIG. electrode 121,1
22, it is relatively easy to attach the ultrasonic transducer 12 to the end of the optical fiber 10.
This means that it is possible to form a that time,
The end face of the optical fiber 10 is polished together with the resin 8,
A thin film 123 may be formed on the polished surface. Also, if you use the surface of the resin 8, you can connect the electrode 12 from there.
It is also possible to draw out 1,122 individual leads. Further, a side part of the optical fiber 11 embedded in the resin 9 is polished and cut along with the resin 9 in the same manner as described above. At this time, the length of the cutting part of the optical fiber 11 is
It is necessary to form it so that it matches that of .
Next, as shown in FIG. 4, these constituent elements are joined by bringing their polished surfaces together, but at this time, in order to improve the coupling efficiency between the two, the refraction of each core of the optical fibers 8 and 9 is adjusted. It is desirable to interpose a transparent thin film layer 14 having a refractive index equal to or close to the index. This thin film layer 14 may be a liquid such as silicone oil. If the refractive index of this joint portion L is too large compared to the refractive index of each core of the optical fibers 10 and 11, light will leak out of the optical fiber and the optical loss will increase; conversely, if it is too small, the degree of optical coupling will deteriorate. I end up. As an example, when an optical fiber whose core has a refractive index of 1.54 is used, the refractive index of the thin film layer 14 may be selected to be approximately 1.50 to 1.58.

As described above, in the optical fiber device according to the present invention, when polishing the joint surfaces of the optical fibers 10 and 11, each of the optical fibers 10 and 11 is fixed by the resins 8 and 9, and Since the resins 8 and 9 are both polished and cut, the work can be done easily, and the polished surface can be smoothed with high precision, making it possible to create optical fibers with excellent optical coupling properties. This means that a branch road can be formed. Similarly, the end face of the optical fiber 10 on which the ultrasonic transducer 12 is formed can be easily and precisely processed.

As described above, in the optical fiber device according to the present invention, two elements are formed by polishing and cutting the entire resin until part of the lateral core of the optical fiber, which is curved and embedded in the resin, is exposed. are bonded together with their polished surfaces brought against each other, and an ultrasonic transducer is formed at one end of the optical fiber in either element, thereby giving the optical fiber itself an active function. By controlling the ultrasonic signal sent into the optical fiber and changing the propagation constant of light in the optical fiber, optical branching or optical coupling can be performed arbitrarily and with high precision while satisfying the phase matching condition for adjacent optical fibers. Moreover, it has various excellent advantages such as simple structure, high reliability, and easy manufacture.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional optical fiber optical coupling path and an optical coupling path, respectively, FIG. 3 is a simplified diagram showing a device using a conventional thin film optical waveguide, and FIG. 4 is a diagram showing a device using a conventional thin film optical waveguide. A front sectional view showing an optical fiber device according to an embodiment, and FIGS. 5A to 5D are diagrams showing a manufacturing process of the optical fiber device according to the embodiment. 8, 9...resin, 10,11...optical fiber,
12... Ultrasonic transducer, 13... AC variable power supply, 14... Thin film layer.

Claims (1)

[Claims] 1. At least two elements formed by polishing and cutting part of the sides of an optical fiber embedded in a resin together with the resin until the core is exposed, and abutting the polished surfaces against each other. At the same time, an ultrasonic transducer capable of sending an ultrasonic signal in the direction of propagation of light is formed on the end face of the optical fiber in either element, and the optical fiber itself has active optical branching or optical coupling. Optical fiber device with added functionality. 2. The optical fiber device according to item 1 above, characterized in that a transparent thin film having a refractive index substantially the same as that of the core of the optical fiber is formed on the bonding surface of each of the elements.