JPS6148694B2 - - 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 optical 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 in the optical fiber sections.

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 a dedicated element with an active function, such as a thin film optical waveguide 5, is connected between the optical fibers 6, as shown in FIG. Currently, 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, when trying to apply such a thin film optical waveguide 5 to a communication network using optical fibers, a method for directly joining the optical fiber 6 and the thin film optical waveguide 5 in a timely manner has not yet been established. The optical loss is large, and therefore an optical coupler for matching is required separately, making the device as a whole 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 difficult to obtain highly reliable coupling efficiency. This has become a very 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 includes a transducer capable of propagating ultrasonic waves in the optical fiber, and changes the propagation constant of the light wave in the optical fiber using the ultrasonic signal to satisfy the phase matching condition. In addition to arbitrarily adjusting the degree of optical branching and optical coupling between optical fibers, it is also possible to propagate ultrasonic signals through the joints of optical fibers in order to make the device itself easy to manufacture and reliable. It is designed to provide a substance.

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.
A bonding layer 10 through which ultrasonic waves can propagate is made of two optical fibers 8 and 9, each polished and cut until
The ultrasonic transducer 11 is provided at one end of the bonding layer 10, and the ultrasonic transducer 11 is provided at one end of the bonding layer 10. Note that 12 in the figure indicates an excitation power source for the ultrasonic transducer 11.

In the optical fiber device according to the present invention configured in this manner, for example, the light P is incident on the optical fiber 8 from one end I, and the ultrasonic transducer 11 is excited to
When an ultrasonic signal is sent along the propagation direction of the light P, the propagation constant ka of the light P passing through the optical fiber 8 is k=ka±K, where K is the propagation constant of the ultrasonic signal.
It will be changed to. Therefore, if the propagation constant of the light P in the optical fiber 8 is equal to k, then
A phase matching condition is obtained between these optical fibers 8 and 9, and the light P sent to the optical fiber 8 is transferred to the optical fiber 9 side. At this time, the length L of the joint between the optical fibers 8 and 9 is L=c/2π, where c is the coupling constant between the optical fibers 8 and 9.
The full bond length is determined by . Therefore, in such an optical fiber device, the AC variable power supply 12 is controlled to change the output magnitude or frequency of the ultrasonic signal oscillated from the transducer 11, that is, the K By changing the value of , the light sent to the output end of the optical fiber 9 can be changed depending on the degree of the ultrasonic signal, and the degree of optical branching and optical coupling in the optical fiber itself can be adjusted as desired. Be able to perform active functions.

The material for the bonding layer 10 is preferably a glass material such as quartz glass or tellurite glass, which has properties similar to those of the optical fibers 8 and 9. The refractive index is selected to be equal to or close to the optical refractive index of the core of the optical fibers 8 and 9 in order to improve the efficiency of optical coupling between the optical fibers 8 and 9. This bonding layer 1
If the refractive index of light at the 0 part is too large compared to that of the core part, the light P will leak to the outside of the optical fibers 8 and 9, resulting in increased optical loss, and if it is too small, the degree of optical coupling will decrease. It will end up being put away. In this case, for example, when the optical refractive index of the core of the optical fibers 8 and 9 is 1.54, a material having an optical refractive index of about 1.50 to 1.58 for the bonding layer 10 is selected. The ultrasonic transducer 11 may be, for example, one in which a thin crystal plate of LiNbO ₃ or the like is adhered to the end face of the bonding layer 10, or a
A ZnO thin film formed by sputtering is used.

FIG. 5 shows another embodiment of the optical fiber device according to the present invention. In this case, a support 13 made of epoxy resin or the like is embedded with an optical fiber 8 so that the cut surface A is exposed. On one side of
A thin film 14 such as ZnO is formed by sputtering, and the bonding layer 10 and the ultrasonic transducer 1 are bonded to each other.
By applying an excitation voltage to the thin film 14, which also serves as the optical fiber 1, a surface acoustic wave is generated at the joint surface between the optical fiber 8 and the optical fiber 9.
In this case, the ZnO thin film 1 is placed on one surface of the support 13.
4, as shown in FIG.
A part of the support 13 is sputtered with ZnO to form the ultrasonic transducer 11, and is structured to propagate surface acoustic waves to the cut surface A of the optical fiber 8 embedded in the support 13. Good too. In this case, there is no need to provide a ZnO thin film as the bonding layer.

Furthermore, FIG. 7 shows another embodiment of the present invention, in which the ultrasonic transducer 11 is easily formed on the end face of the bonding layer 10 having a small cross-sectional area, and the optical fiber 8 , 9 are respectively attached to a support 15 made of epoxy resin or the like so that the cut surfaces A and B are exposed, as in the case described above.
16, each cut surface A of the optical fibers 8 and 9,
These supports 15 and 16 are bonded by interposing the bonding layer 110 so that the supports 1
A relatively large ultrasonic transducer 11 is formed by utilizing one end portion of the bonding layer 10 whose end surfaces are aligned with those of 5 and 16. In this case, the ultrasonic transducer 11 is
The ultrasonic signals are also provided overlappingly on the supports 15 and 16 when excited.
It is not transmitted to the 6 parts, but is propagated mainly to the bonding layer 10.

As described above, in the optical fiber device according to the present invention, ultrasonic signals can be propagated through at least two optical fibers in which a part of the side cladding is polished until the core is exposed, and each cut surface of the optical fiber is polished. The optical fibers are bonded to each other via a bonding layer, and an ultrasonic transducer is provided on a part of the bonding layer, or one of the optical fibers is placed in a support so that the cut surface thereof is exposed. It is constructed by embedding the optical fiber in the support body, directly joining the other optical fiber with its cut surface, and installing an ultrasonic transducer in a part of the support so that surface acoustic waves are transmitted to the cut surface. By controlling the output of the ultrasonic transducer and changing the propagation constant of the light sent into the optical fiber, it is possible to selectively and precisely couple adjacent optical fibers, and the structure is simple. It has the excellent advantage of high reliability.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an optical coupler using a conventional optical fiber, FIG. 3 is a simplified diagram showing a device using a conventional thin film optical waveguide, and FIG. 4 is an embodiment of the present invention. FIGS. 5 and 7 are simplified configuration diagrams showing other embodiments of the present invention, and FIG. 6 shows an optical fiber embedded in a support and an ultrasonic transformer. FIG. 3 is a perspective view showing an example of a configuration with a juicer. 8, 9... Optical fiber, 10... Bonding layer, 11... Ultrasonic transducer, 13, 15, 16... Support, 14... ZnO thin film.

Claims (1)

[Claims] 1. At least two optical fibers, each of which has been abrasively cut through a portion of its lateral cladding until its core is exposed, are bonded to each other on each cut surface via a bonding layer through which ultrasonic signals can propagate. An optical fiber device constructed by bonding and creating an ultrasonic transducer in the bonded layer. 2. At least two optical fibers each having a part of the side cladding polished and cut until the core is exposed, one of which is embedded in a support so that the cut surface is exposed, and the other optical fiber is polished and cut until the core is exposed. An optical fiber device constructed by forming an ultrasonic transducer on the support so that surface acoustic waves are transmitted to the surface.