JPH036504A - Optical branch element with light cutting function - Google Patents

Abstract

PURPOSE:To reduce the size of the optical branch element and to improve the reliability by providing a branch optical waveguide of quartz-based glass arranged on a silicon substrate and an optical cutoff switch arranged on the branch optical waveguide. CONSTITUTION:This element is equipped with the silicon substrate 1, an input port 2, output ports 3a - 3h, the optical branch part 4 constituted on the substrate 1 by using the quartz-based glass waveguide, and an optical switch part 5, and further equipped with micromechanical or thermo-optic switches 5a - 5h which consist principally of quartz-based optical waveguides. The branch part 4 consists of Y-shaped optical branch parts 6a - 6g and the input port 2 and output ports 3a - 3h are connected to a terminal device and a subscriber device respectively. Consequently, the optical branch element with a light cutting function is obtained which is reducible inside and suitable for mass-production and has an enough speed light to disconnect a subscriber device where trouble occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical branching element with a light blocking function that is compact and can be manufactured in batches for use in the field of optical communications.

[Prior Art] In order to popularize optical fiber communication, it is desirable to share facilities such as optical fiber transmission lines among many people in order to reduce costs. Communication network configurations in which signal light sent via optical fibers is divided into 8, 16, or 32 branches for use by a large number of subscribers are being actively studied. The request signal light from the subscriber flows backward through the optical branching element and is delivered to the terminal station. Optical branching elements that play an important role in such communication networks are also called star couplers or tree couplers.

However, the communication network using the above-mentioned optical branching element has the following problems. In other words, if one subscriber's transmitting/receiving device connected to an optical branching element breaks down and a failure occurs in the form of continuous oscillation of request signal light, all devices and terminals connected to this optical branching element will fail. Communication between stations sometimes became impossible. In order to avoid this problem,
Proposal by Togura et al., “Broadband optical subscriber network configuration method applying optical star coupler” IEICE Technical Research Report Vol.
1.87 No. 108. lN37-43 (1987
, 7, 17), a communication network configuration has been proposed in which a cutoff optical switch is connected to each branch port of an optical branching element, and a failed device is cut off in the event of a failure.

[Problems to be Solved by the Invention] Until now, electrochromic elements, liquid crystal elements, electromagnetic shutters, etc. as optical switches have been installed in each branching boat of a fiber-type optical branching element configured by connecting a plurality of fiber-type couplers in multiple stages. Star couplers with switches that are individually connected have been proposed and realized, but because they are constructed by combining individual parts, it is difficult to downsize, lacks reliability, and lacks productivity and price. There were many problems such as the high cost of optical fiber communication, which contradicted the original purpose of disseminating optical fiber communication to each subscriber at a low cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical branching element with a light blocking function that solves the above-mentioned drawbacks.

[Means for Solving the Problems] In order to achieve such an object, the optical branching element of the present invention includes a silicon substrate, a branching optical waveguide made of a silica glass material disposed on the substrate, and a branching optical waveguide in the middle of the branching optical waveguide. It is characterized by consisting of a light cutoff switch arranged.

In the present invention, an integrated optical circuit configuration is used in which an optical branching element made of a quartz-based leading waveguide and an optical cutoff switch are manufactured all at once on a flat silicon substrate. In order to avoid the polarization dependence often seen in integrated optical circuit type optical switches, it is preferable to employ a micromechanical type or a thermo-optic type as the optical cutoff switch mechanism. Further, in order to minimize the connection loss with the optical fiber serving as the transmission line, it is preferable that the dimensions of the core portion of the silica-based optical waveguide be made comparable to the diameter of the optical fiber core.

[Function] FIG. 1 is a schematic plan view showing a configuration example of a light branching element with a light blocking function of the present invention, and is an example of an 8-branching element. 1 is a silicon substrate, 2 is an input port, 3a to 3h are output ports, 4 is an optical branch section configured on the substrate 1 by a silica-based glass waveguide, and 5 is an optical switch section, which also uses a silica-based leading waveguide. It mainly consists of micromechanical or thermo-optical optical switches 58 to 5h that are constructed and arranged. The light branching section 4 is composed of seven Y-shaped light branching sections 6a to 6g. Human powered boat 2, output capo) 3a to 3h
Optical fibers (not shown) are usually connected to the terminals and to the terminal equipment and subscriber equipment, respectively.

The signal light sent from the terminal station is input to this device from the input boat 2, is distributed one after another by the optical branching element, passes through the optical switches 58 to 5h, and is sent to the output ports 38 to 38.
After 3h, it is distributed to the subscriber equipment. Request optical signals from each subscriber pass through the output ports 38 to 3h, are collected into the input port 2, and are transmitted to the terminal station. If a failure occurs in a particular subscriber's transmitting/receiving device, the corresponding optical switch among the optical switches 5a to 5h is activated, optically disconnecting the subscriber's transmitting/receiving device, and disconnecting the terminal station from other subscribers. It acts so as not to interfere with normal communication with.

The optical branching element with a light blocking function of the present invention has a light branching section and a light blocking switch section formed on the same substrate by the same continuous glass waveguide, so that it is compact and has excellent batch productivity. In addition, the silica-based optical waveguide used in the present invention has the same material as an optical fiber and can have a core size comparable to the core of an optical fiber, so it has the advantage of low connection loss with the optical fiber. have. Furthermore, since the optical switch part is a micromechanical or thermo-optic type, there is no polarization dependence often seen in integrated optical circuit type switches, and there is no need for complicated polarization compensators, etc. It can be set arbitrarily.

[Examples] Hereinafter, the present invention will be described in detail by way of examples, with respect to cases in which 1) a micromechanical type and 2) a thermo-optical type are used as the optical switch section.

FIG. 2 is a diagram showing an example of the detailed structure of the micromechanical optical switch portion of the optical branching element with a light blocking function according to the first embodiment of the present invention. FIG. 2(a) is a partial plan view including two optical switches 5a and 5b of the optical switch section 5 in FIG. 1. (b) is a side sectional view of the optical switch 5a. (c) and (d) are enlarged cross-sectional views taken along lines AA' and BB' in figure (a), respectively. The inside of the optical switch 5a includes a movable waveguide section 21a that is partially separated from the silicon substrate and can be moved up and down. An electrode film 22a is arranged on the upper surface of the movable waveguide section 21a. The silicon substrate 1 also serves as a lower electrode.
Other optical switches 5b and the like have similar structures.

The above structure was fabricated by a known combination of a technique for depositing a silica-based glass film on a silicon substrate, a reactive ion etching technique for the glass film, and an isotropic etching technique for silicon. The core portion dimensions of the optical waveguides 7a, 7b, etc. are 8 μm square, and the thickness of the quartz-based cladding layer 8 is 50 μm. The length of the movable waveguide 21a, etc. is 3 mm, and the cavity 24a,
The gap such as 24b was set to 20 μm. This movable waveguide section was formed by removing the cladding layer on both sides in the form of a groove, and then etching away the portion of the silicon substrate corresponding to the lower part of the movable waveguide. The electrode film 22a etc. are
It was formed by vapor depositing a chromium metal film. Of course, photolithography was applied to the formation of the waveguide pattern and electrode pattern in the above process.

For example, when no electrostatic voltage is applied to the electrode film 22a, the movable waveguide 21a is in a horizontal state, and the gap 24a is
The signal light can pass by jumping over the , and the optical switch is in the passing state. When an electrostatic voltage (approximately 500 volts) is applied to the electrode film 22a, the movable waveguide is drawn toward the silicon substrate due to the electrostatic force between it and the silicon substrate electrode, and the signal light is blocked in the gap 24a, causing the optical switch to be in a blocked state. becomes. FIG. 3 is a side sectional view showing the cut-off state of the mechanical optical switch, and when compared with the passing state shown in FIG. 2(b), the effect of the mechanical optical switch in the present invention can be clearly seen.

Note that in FIG. 2(a), the optical waveguide end face such as the cavity 24a is formed obliquely with respect to the signal light traveling direction, but this suppresses the Fresnel reflected light at the end face from traveling in the opposite direction. It's for a reason. If the cavity is filled with a refractive index matching liquid, etc., such oblique end face processing can be omitted.

A typical performance example of the optical branching element with a light blocking function of this example is described below in the case of eight branches.

Excessive loss: 2dB (input/output optical fiber connection load) Optical switch passage loss when cut off: 35dB Optical switch response speed: 20m5ec Polarization dependence: None Wavelength dependence: None Element size: Silicon chip size 50mm x 5m
m package size 100mm x 10mm input/output fiber single mode fiber (core diameter lOμm) In the above example, electrostatic force was used to drive the movable waveguide section, but in addition to this, a piezo element could be used. It is also possible to move the movable waveguide up and down. Fig. 4 is an explanatory diagram showing the detailed structure of the thermo-optic optical switch section of the device according to the second embodiment of the present invention; 5
5B is a partial plan view including portions a and 5b, and FIG. 5B is an enlarged sectional view taken along line segment BB' in FIG.

In FIG. 4, for example, the optical switch 5a has a Matsuhatsu Enda optical interferometer configuration in which Y-shaped optical branching parts 41a and 41b are connected by two waveguide arms 43a and 44a of equal length, and a waveguide arm 43a, Thin film heaters 45a and 46a are formed on the cladding layer 8 corresponding to the cladding layer 44a. The dimensions of the core portion of each waveguide, etc. are the same as in Example 1.

The thin film heaters 45a, 46a, etc. are made of chromium metal film,
Selectively lower the temperature of the lower guiding waveguide core by applying current.
It has the effect of raising the temperature by about 0℃. Heater length is 5ml
It is about 11. Here, the silicon substrate effectively acts as a heat sink.

Here, for example, the thin film heater 45a of the optical switch 5a.

When no current is applied to any of the optical switches 46a, the signal light passes through the optical switch 5a with almost no attenuation. Electricity is supplied to either one of the thin film heaters 45a, 48a, and the leading waveguide arm 43a is activated by the thermo-optic effect.

When the optical path length of one of the optical switches 44a is set to be longer than the other by the equivalent of a half wavelength, the optical switch 5a is brought into a cut-off state according to the well-known principle of the Matsuhatsu Enda optical interferometer, and the desired effect is obtained. The performance of the device of this example (8 branches) is as follows.

Excess loss: 1.5 dB Light cutoff loss: 25 dB Response speed: 20 m5ec Polarization dependence: None Wavelength dependence: Yes Element size: Implementation - (same as Ml In this example, the Matsuha Tsuenda optical interferometer type thermo-optic switch is Y-shaped Although the configuration is based on a type optical branching section, it is possible to replace this with a directional coupler type optical branching section.Also, it is also possible to replace each figure 7 shape of the optical branching section 4 with a directional coupler type. It's okay.

Although the above embodiments have been described using eight branches as an example, the present invention is of course not limited to this and generally applies to N branches.

[Effects of the Invention J As explained above, in the present invention, the optical branching section and the optical switch section can be formed all at once on a silicon substrate mainly using planar photolithography technology, and therefore miniaturization is possible. Moreover, since it is a form suitable for mass production, it is also suitable for economicalization. Since the optical switch section has no polarization dependence, it can be easily inserted into the optical transmission line. The response speed is also approximately several + osec - 20 msec, which is sufficient to disconnect a subscriber device in which a failure has occurred. In addition, there is an advantage that no holding power is required when there is no fault, and the device of the present invention will be used in the future as a so-called fiber to the
It is expected that the company will make a significant contribution in response to trends in OME.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the basic configuration of a light branching element with a light blocking function according to the present invention, and FIG. 2 is a section illustrating the structure of a light blocking switch section (micromechanical type) according to the first embodiment of the present invention. Figure 3 is a diagram showing the cut-off state of the light cutoff switch according to the first embodiment of the present invention, and Figure 4 is a partial diagram illustrating the structure of the light cutoff switch section (thermo-optic type) according to the second embodiment of the present invention. It is. 1...Silicon substrate, 2...Input boat, 3a, 3b,..., 3h...Output boat, 4...
Optical branching section, 5... Optical switch section, 5a,..., 5h... Optical switch, 6a,...
6g...Y-shaped light branching section, 7a,..., 7h...
Branch waveguide, 8... Cladding layer, 21a, 21b... Movable waveguide section, 22a, 22b - Electrode film, 23a, 23b... Silicon substrate removed section, 24a, 2
4b--Gap portion, 41a, 42a, 41b, 42b--Y-shaped optical branching portion, 43a, 44a, 43b, 44b--Optical waveguide arm, 45a, 46a, 45b, 46b--Thin film heater. 3 ℃

Claims (1)

[Claims] 1) An optical system comprising: a silicon substrate; a branched optical waveguide made of silica-based glass disposed on the substrate; and an optical cutoff switch disposed in the middle of the branched optical waveguide. Optical branching element with blocking function. 2) The optical branching element with a light blocking function according to claim 1, wherein the optical blocking switch is a micromechanical optical switch that includes a movable optical waveguide portion remote from the silicon substrate as a part of the branching optical waveguide. . 3) The optical cutoff switch includes a waveguide-type Mach-Zehnder optical interferometer placed in the middle of the branched optical waveguide, and an optical waveguide arm constituting the Mach-Zehnder optical interferometer that controls the optical path length of the optical waveguide arm by a thermo-optic effect. 2. The optical branching element with a light blocking function according to claim 1, further comprising a heater for changing the signal light and blocking the signal light passing through the Mach-Zehnder optical interferometer.