JPS58159503A - Optical switch - Google Patents

Abstract

PURPOSE:To obtain an optical switch which has high reliability and less insertion loss by destroying a reflection part thermally through Joule heat generation by feeding and thus performing switching. CONSTITUTION:This optical switch consists of the 1st lens 4 for the image conversion of incident light from an optical fiber 1, a switching element 7 which reflects or transmits the light passed through the lens 4, and a lens 5 for coupling the light reflected by the switching element 7 with a fiber 3 while converging it. The switching element 7 once fed at electrodes 8 varies in reflectivity inreversibly to change optical paths and when the switching element 7 is powered on, Joule heat destroys the reflecting film to allow the light to pass through it. Namely, the element has high reflectivity before being powered on and decreases in reflectivity after being powered on. Consequently, the optical switch which has high reliability and less insertion loss is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switch inserted into an optical transmission line to switch the optical transmission line in optical fiber communication.

Optical switches are important optical functional circuit components for advancing and diversifying optical fiber communications, and are already used for bypass switching in optical fiber links and switching between active and backup light sources and lines in systems that require high reliability. It has been put into practical use.

Optical switches can be roughly divided into two types: those that switch optical paths by mechanically driving optical elements of appropriate shapes such as fibers and prisms, and those that use electro-optic or magneto-optic effects and have no moving parts. It can be divided. Although the former type of switch currently has a lower switching speed than the latter type of switch, it is practical because it has low insertion loss and low crosstalk and can be used with multimode fibers, which are currently mainstream. On the other hand, various systems have been proposed for the latter switch, but all of them have large insertion loss and crosstalk, and there are still many problems to be solved before they can be put into practical use.

One of the promising fields of application of optical fiber communications is optical submarine relay transmission systems. In this method, the repeater is sunk to the ocean floor,
Because it is difficult to collect and costs a lot of money,
The components used in repeaters are required to be extremely reliable. Although a semiconductor laser (LD) is used as a light source in the optical submarine relay transmission system, it cannot be said that it is sufficiently reliable at present. For this reason, methods of duplicating or quadrupling the light sources using a light switch are being studied and experimented with. However, currently, the switches that can be used in this method are mechanical optical switches that have a moving part as described above, but because they have a moving part, this type of switch also has excellent reliability. It is hard to say that this is sufficient.

An object of the present invention is to provide an optical switch that can be used in the above-mentioned optical communication system that requires extremely high reliability, has a switching type that does not have any moving parts, is highly reliable, and has low insertion loss.

The optical switch of the present invention includes a first lens that converts incident light from a light source into an image, a switching element that switches the optical path by reflecting or transmitting the light after passing through the first lens, and a switching element that switches the optical path by reflecting or transmitting the light after passing through the first lens. In an optical switch consisting of a second lens that focuses the light transmitted through the switching element and a third lens that focuses the light transmitted through the switching element, the reflective portion is thermally destroyed by Joule heat generated by energizing the switching element. It is characterized in that the optical path is switched from a reflective state to a transmitting state.

An embodiment of the optical switch of the present invention is shown in FIG.

The switch of the present invention includes a first lens 4 that converts the incident light from the optical fiber 1 into an image, a switching element 7 that reflects or transmits the light after passing through the lens 4, and a switching element 7 that focuses the light reflected by the switching element 7. It consists of a lens 5, which is coupled to the fiber 2, and a lens 6, which focuses the light transmitted through the switching element 7 and couples it to the fiber 3. When the switching element 7 is energized to the electrode 8J, the reflectance irreversibly changes and the optical path is switched.When the switching element 7 is energized, the reflective film is destroyed by Joule heat and the light is transmitted. We are using.

That is, the reflectance is high before energization, and decreases after energization. Once energized, the reflectance remains reduced, and the switching operation is performed at one-time intervals.

FIG. 2 shows a first example of the switching element 7 shown in FIG. A single metal film 10 is coated on the glass plate 9 so that it is narrow only at a portion 11 through which light passes. 12 is an electrode. Before energization, the metal film is in the portion through which light passes, so the transmittance is 0 and the reflectance is 1 (ignoring light absorption loss).

Thus, in FIG. 1 fibers 1 and 2 are in a coupled state.

When electricity is applied, the constricted part of the metal film generates the most heat due to 1 Joule heat, and the metal film in the part 11 through which light passes melts.
They gather on the electrode side due to surface tension, and as a result, the transmittance is 1,
The reflectance is O (however, the Fresnel loss of the glass is ignored). The width of the constriction needs to be only one inch wider than the spot diameter condensed by the lens. For example, in the case of one-to-one image conversion using a lens using a single mode fiber, the width is about 10 μm. When At is used as the metal film, the reflectance is 95% and the insertion loss of this switching element is about 0.3 dB. The time required for switching is 0.1 to several seconds depending on the energizing power.

Figure 3 shows a second example of the switching element shown in Figure 1.
It is. 13 is a triangular prism, and 14 is a prism whose surface facing the transparent electrode and prism 13 is coated with a material that is transparent with a low melting point and has approximately the same refractive index as the prism. There is a gap of about several μm between the prisms 13 and 14. 15 is an electrode for supplying electricity to the transparent electrode.

The switching operation will be explained with reference to FIGS. 4 and 5.

Before energization, the light incident on the prism 13 is totally reflected and emitted as shown in FIG. That is, the reflectance is 1 and the transmittance is O. On the other hand, when the electrode 15 is energized, the transparent electrode 17 made of indium oxide sous 6= several hundred λ thick generates Joule heat, and the low melting point material 16 melts, closing the gap between the prisms 13 and 14. Since the prism 13 is filled in, the light incident on the prism 13 is transmitted as shown in FIG. Transparent electrode, prism and low melting point material 16
If the reflection caused by the slight refractive index difference l between the two is ignored, the reflectance will be 0 and the transmittance will be 1. Refractive fishing rod 1 as a low melting point material
．． Using No. 5 epoxy, the gap between the prisms was 41 μm.
I was able to switch at about 100°C. The insertion loss of the switching element of C is mostly due to the transparent electrode, and is 1~
It is about 2 dB. The time required for switching depends on the energizing power, but is in the range of 0.1 to several seconds.

As described above in detail, in the optical switch of the present invention, switching is performed by thermally destroying the reflective portion by Joule heat generation due to energization. Therefore, since there is no movable part, there is no need for a mechanism to guide or align the movable parts as in conventional mechanical type optical switches, and it is more reliable than these optical switches.

In addition, the insertion loss can be made equivalent to that of conventional mechanical type switches.

Although the switching of this switch is only done once and is irreversible, it is useful for highly reliable systems such as optical submarine relay systems that require only one switching.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the optical switch of the present invention, Fig. 2 is a plan view showing an example of the switching element shown in Fig. 1, and Fig. 3 is another example of the switching element shown in Fig. 1 of the present invention. FIGS. 4 and 5 are side views showing the operation of the switching element shown in FIG. 3. 1, 2.3...Fiber, 4,6,6...
...Lens, 7...Switching element, 8...
Electrode, 9... Glass plate, 10... Metal film, 11... Portion through which light passes, 12°15.
... Electrode, 13.14 ... Prism, 1
6...Low melting point transparent material, 17...Transparent electrode.蓼1 MEMU2 fig.

Claims (3)

[Claims] (1) a first lens that converts the incident light from the light source into an image;
a switching element that reflects or transmits the light after passing through the first lens to switch the optical path; a second lens that focuses the light reflected by the switching element; and a second lens that focuses the light that has passed through the switching element. 3. An optical switch comprising three lenses, characterized in that the reflective portion is thermally destroyed by Joule heat generated by energizing the switching element to switch the optical path from a reflective state to a transmitting state. (2) The switching element is characterized in that the optical path is switched by coating a metal film on a glass plate and melting the metal film by applying electricity to the metal film. light switch. (3) The switching element has the total reflection surfaces of the triangular prisms facing each other, the total reflection surface of one prism is coated with a transparent material having a low melting point and approximately the same refractive index as the electrodes and the prism, and the electrode number is energized. The optical switch according to claim 1, wherein the optical path is switched by melting a transparent material to fill gaps between total reflection surfaces of the prisms.