JPH0421824A - Excess light protective method for optical circuit and photosensitive type light attenuating element - Google Patents

Abstract

PURPOSE:To easily and inexpensively protect optical circuit parts against excess light by increasing the intensity of incident light in excess of a prescribed value and absorbing excess light energy, thereby changing a photosensitive body into an opaque state. CONSTITUTION:The photosensitive type light attenuating element 3 is constituted by inserting a photosensitive resin layer 3c which is transparent at the intensity of light for irradiation smaller than the prescribed value and is sharply decreased in light transmittance on increasing of the irradiation intensity between two sheets of glass plates 3a and 3b and sticking the glass plates to each other. The photosensitive resin layer 3c acts like a fuse in an electric circuit. Namely, the photosensitive resin layer 3c absorbs the energy of the light on excessive increasing of the intensity of the incident light on the layer itself and is rapidly made opaque by photochemical decomposition or the like, thereby decreasing the light transmitted therethrough to zero or to an extremely low level. The optical circuit parts are inexpensively protected against the excess light in this way.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a protection method for preventing excessive light having an intensity exceeding a set level from reaching optical circuit components such as optical measuring devices and optical communication devices. and a photosensitive light attenuation element used therein.

(Conventional technology) With the advancement of optical circuit technology, the output of laser light sources used for optical communication etc. has gradually become larger, and when a laser light source or optical amplifier causes abnormal transmission, the output power is much higher than the set level. This light may propagate into the optical circuit and destroy optical components such as the laser light source, optical isolator, and light receiving element. It has become necessary to protect optical circuit components from such excessive light.

Traditionally, variable optical attenuators and optical switches were placed on the optical circuit transmission path as a method to protect optical circuit components from excessive light, and abnormally strong light propagated along the optical transmission path. is detected by another sensor system, and in response to the detection signal, the attenuation rate of the variable optical attenuator is rapidly increased or the optical switch is turned off.

(Problem to be solved by the invention) In a method of detecting the incidence of abnormally strong light and operating an optical attenuator or optical switch to block the propagation of excessive light (significantly attenuate or block it), A sensor system is required to detect the excess light, making the device complex, expensive and unreliable. Furthermore, the response time from detection of excess light to the end of operation of the optical attenuator or optical switch is relatively long, and the reliability of the protection operation is also low from this point of view.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide reliable protection of optical circuit components from excessive light by means that are simple and inexpensive to implement.

(Means for Solving the Problems) Therefore, in the present invention, a photoreceptor whose light transmittance rapidly decreases when the intensity of incident light increases beyond a predetermined value is interposed on the transmission path of an optical circuit, and the photoreceptor is This is to prevent excessive light from reaching the optical u-path components on the exit side.

In addition, as an optical device embodying the above-mentioned photoreceptor, two photosensitive resin layers are sandwiched between the layers, which are transparent when the intensity of the irradiated light is lower than a predetermined value, and whose light transmittance rapidly decreases when the intensity of the irradiated light increases. We have developed a photosensitive light attenuation element made by laminating glass plates.

(Function) The photoreceptor and the photosensitive resin layer perform a function similar to a fuse in an electric circuit. When a fuse in an electrical circuit receives too much current, it heats up and blows, stopping the current from flowing. When the intensity of light incident on itself becomes excessive, the photoreceptor and the photosensitive resin layer absorb the energy of the light and rapidly become opaque due to photochemical decomposition, reducing the amount of light transmitted to zero or significantly. reduce

(Example) FIG. 1 shows a configuration example of a photosensitive optical attenuator incorporating a photosensitive optical attenuator of the present invention. The case 1 of this attenuator is of a plug-jack type, and an optical fiber 2 is built into the tip of the plug part 1a, and the jack part 1b is connected to the plug part of another device having the same configuration as the plug part 1a. It is configured.

A photosensitive light attenuation element 3 is disposed in the center of the case 1, and a lens 4 is disposed between the attenuation element 3 and the plug section 1a, and a lens 5 is disposed between the attenuation element 3 and the jack section 1b. It is arranged.

The photosensitive light attenuation element 3 is made up of two glass plates 3a with a photosensitive resin layer 3C sandwiched between them, which is transparent when the intensity of irradiated light is lower than a predetermined value and whose light transmittance rapidly decreases when the irradiated intensity increases. and 3b are pasted together. For example, an epoxy adhesive is used as the photosensitive resin layer. The glass plates 3a and 3b are coated with anti-reflection coating. The photosensitive resin layer 3c has the property that when the intensity of the irradiated light increases, it absorbs the light energy and causes photochemical decomposition, thereby rapidly becoming opaque.

The lens 4 focuses the light emitted from the optical fiber 2 onto the photosensitive resin layer 3C of the element 3, and the lens 5 focuses the light emitted from the optical fiber 2 onto the photosensitive resin layer 3C.
The light transmitted through C is focused on a predetermined position of the jack portion 1b. This optical path is of course reversible.

The photosensitive optical attenuator configured as described above is connected to the plug section 1a.
and insert it into the transmission path of a predetermined portion of the optical circuit using the jack portion 1b. For example, if light is incident from the plug part 1a side, if the intensity of the incident light is within the set level, the light will pass through the attenuation element 3 with almost no attenuation and will be coupled to the jack part 1b. It propagates into the fibers of other optical connectors with little loss. However, when the intensity of the incident light becomes excessive, the light transmittance of the photosensitive resin layer 3C decreases rapidly, and almost no light is transmitted to the jack portion 1b side. This can prevent excessive light from reaching the optical circuit components on the output side.

As shown in FIG. 2, if the position of the light attenuation element 3 is changed so that the focus of the lenses 4 and 5 is not focused on the photosensitive resin layer 3C, the intensity of light per unit area irradiated onto the resin layer 3C will decrease. becomes smaller. Therefore, even if the same photosensitive light attenuation element 3 as shown in FIG. 1 is used, by appropriately adjusting its position as shown in FIG. 2, the operating characteristics seen from the input and output ends can be adjusted as appropriate.

(Effects of the Invention) As explained in detail above, in this invention, when the intensity of incident light increases beyond a predetermined value, the photoreceptor (photosensitive resin layer) becomes opaque by absorbing the excess light energy. Since the light changes rapidly, there is no need for a sensor system to detect excess light, and the attenuation element itself becomes opaque in response to excess light, resulting in very high responsiveness and reliability, as well as very low cost. can be carried out.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing an example of the configuration of a photosensitive optical attenuator using the photosensitive optical attenuator of the present invention. 1...Case 1a...
・Plug part 1b... Jack part 2...
......Optical fiber 3...Photosensitive optical attenuation element 3a...Glass plate 3b...
...Glass plate 3c...Photosensitive resin layer 4.
・・・・・・・・・Lens 5・・・・・・・・・Lens

Claims (2)

[Claims] (1) A photoreceptor whose light transmittance decreases rapidly when the intensity of incident light increases beyond a predetermined value is interposed on the transmission path of the optical circuit, and excessive light reaches the optical circuit components on the output side of this photoreceptor. A method for protecting optical circuits from excessive light. (2) A photosensitive type made of two glass plates bonded together with a photosensitive resin layer that is transparent when the intensity of the irradiated light is lower than a predetermined value and whose light transmittance rapidly decreases when the intensity of the irradiated light increases. Optical attenuation element.