JP4427635B2 - Optical cross-connect device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an optical cross that can directly change the path of an optical signal without converting it into an electrical signal in a WDM (wavelength division multiplexing) transmission apparatus, which is a high-speed transmission technique in an optical backbone network. It relates to a connect device.
[0002]
[Prior art]
With the explosive spread of personal computers and mobile phones for connecting to the Internet, higher bandwidths using broadband, higher speeds such as xDSL, and constant connection have begun to spread in communication infrastructures. In order to facilitate the development and popularization of telephones, it is desired to significantly increase the speed of the backbone network.
[0003]
When transmitting a signal using an optical fiber cable, the conventional TDM (time division multiplexing) method can transmit only one wavelength to one optical fiber cable, but the WDM method can transmit a number of wavelengths having different wavelengths. Therefore, the bandwidth and transmission speed can be greatly improved by using the existing optical fiber cable. In the WDM transmission apparatus using the WDM technology, in order to change the path of the input side optical signal and the output side optical signal at high speed, that is, to cross-connect, the optical signal is converted directly into an electric signal without being converted. An optical switch that can be used is indispensable.
[0004]
At the present time, the optical switch method includes a path change by reflecting incident light at a specific reflection angle by rotating or moving up and down a micro mirror made of a Si substrate or the like called “mirror type”. In a waveguide having a crossing portion in which a heater is embedded in a substrate called an “optical waveguide type”, the path is changed by changing the refractive index of light by heating the heater, or in place of the heater called a “bubble type” A groove filled with liquid is provided, and the path is changed by changing the reflection angle of light by controlling the generation of bubbles in the groove, or the path is changed by bending an optical fiber cable called "mechanical type" with an electromagnet etc. There are four types of methods.
[0005]
[Problems to be solved by the invention]
In the above-mentioned various methods, the “mirror type” has the largest number of channels at present, with several hundred channels. However, in order to change the path of the optical signal, it involves mechanical movement by rotating or moving the mirror up and down. Therefore, there was a problem in durability. In addition, the switching speed is as low as about 50 msec. In addition, the “mechanical type” has a problem that the switching speed is relatively high at 10 msec or less, but only a few channels can be configured, and it can be used only for small-scale applications. In addition, the “planar optical waveguide type” and “bubble type” have a relatively high switching speed of about 10 msec and can be configured with several tens of channels. However, a groove filled with a heater or liquid is formed in the substrate. Due to the buried structure, there was some concern about durability. In addition, although there is no mechanical movement, some mechanical components are required and the structure becomes complicated.
[0006]
The present invention has been made to solve the above-described problems, has no mechanical moving parts, has a simple structure, and has hundreds to thousands of channels. It is an object of the present invention to provide an optical cross-connect device that can cope with a device and can process at a very high switching speed, and can rapidly promote the construction of a next-generation photonic network.
[0007]
[Means for Solving the Problems]
FIG. 1 is a conceptual diagram of the entire optical cross-connect device of the present invention, and FIG. 2 is a conceptual diagram of an optical switch for applying an electro-optic effect to a multimode optical waveguide in the optical cross-connect device of the present invention. As shown in FIG. 1, the input light input from the input optical fiber 1 is input to the multimode optical waveguide 4 via the AWG type multiplexer / demultiplexer 12 and the dichroic mirror 13. The input light switched by the holographic filter 5 is further output to the output optical fiber 2 via the dichroic mirror 13 and the AWG multiplexer / demultiplexer 12. As is apparent from the figure, the configuration of the optical cross-connect device of the present invention has no driving part and is made of only an optical material.
[0008]
The multimode optical waveguide 4 is formed of a non-linear optical crystal or an organic material having an electrooptic effect on the multimode optical waveguide support substrate 3, and is optimal for controlling a speckle pattern on the multimode optical waveguide 4. An electrode 10 having a shape and an electrode 10a as a counter electrode are disposed below. In the figure, a triangular electrode 10 is shown as an example. Then, by applying a voltage to the electrode 10, the laser beam 9a passing through the multimode optical waveguide 4 under the electrode 10 generates a speckle pattern corresponding to the condition by the electro-optic effect. The speckle pattern is primarily determined by the structure of the electrode 10, the applied voltage, and the optical characteristics of the multimode optical waveguide 4. The generated speckle pattern does not change with time unless the external environment changes. For this reason, it is possible to realize a stable device with a simple structure and high reliability and economy. FIG. 3 is a cross-sectional view showing the positional relationship between the electrode for the electro-optic effect and the multimode optical waveguide in FIG. 2, and shows the positional relationship between the electrode 10 and the multimode optical waveguide 4 in an easy-to-understand manner. FIG. 4 is a plan view conceptually showing a state in which a laser beam input in a single mode generates a speckle pattern determined by an electrode in the multimode optical waveguide and is input to the holographic filter from the multimode optical waveguide. The speckle pattern formed by the multimode optical waveguide 4 joins the multimode optical waveguide 4 ′ as it is, and it is easy to understand how it is input from the single multimode optical waveguide 4 ′ to the holographic filter 5. Indicated.
[0009]
FIG. 5 is an arrangement diagram of an optical system when creating a holographic filter in the optical cross-connect device of the present invention. In order to add an optical switching function, a laser device 6, a lens system 7a, a beam splitter 7b, and a holographic filter are shown. A hologram is formed in advance on the holographic filter 5 by an optical system composed of the reflection mirror 7c attached to the reflection mirror driving device 7d that translates in parallel to the lens 5. Since this is performed before the optical cross-connect device operates in the system, the time required for hologram formation recording does not affect the switching speed of optical communication. For this reason, in this process, the laser device 6 does not have high output, and the holographic filter 5 does not necessarily have high sensitivity. Therefore, the optical cross-connect device of the present invention is economical and is characterized by many choices of materials for the holographic filter 5.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described based on an arrangement diagram of an optical system when creating a holographic filter in the optical cross-connect device of the present invention shown in FIG. First, as a production process of the holographic filter 5, the laser beam 9 oscillated from the laser device 6 is converted into uniform parallel light having a constant diameter by the lens system 7a, and the parallel light is combined with the optical fiber 1 for signal input and the holographic signal. In order to irradiate the nonlinear optical crystal or organic material used as the filter 5, the beam splitter 7b divides it into two paths. One of the divided parallel lights 9a is directly input to the input optical fiber 1 via the lens array 7e. Other parallel light 9b is illuminated by a reflecting mirror 7c attached to the reflecting mirror driver 7d translating and to the left and right to the holographic filter 5 to the nonlinear optical crystal or organic material. In this way, the light of the two optical paths output from the same light source intersects in the nonlinear optical crystal or organic material and interferes with light to form a hologram. As a result, the hologram necessary for the optical cross-connect device of the present invention is recorded in the holographic filter 5 in advance.
[0011]
Next, means for forming a hologram on a nonlinear optical crystal or organic material will be described in more detail. The basic means for generating various speckle patterns is determined by the shape and number of electrodes 10 formed on the multimode optical waveguide 4 and the voltage applied to the electrodes 10. A switching condition is set, and holograms are formed on the nonlinear optical crystal or the organic material at regular intervals. By using this as the holographic filter 5, the light path can be selectively determined. As described above, since the hologram is not formed during communication, there is no time restriction on the formation or deletion.
[0012]
After the holographic filter 5 is completed, the laser device 6, the lens system 7a, the beam splitter 7b, the reflection mirror 7c, and the reflection mirror driving device 7d used for forming the hologram are removed from the communication system of the optical cross-connect device. For this reason, it is possible to provide a system that is extremely simple, easy to maintain, and economical.
[0013]
Next, the optical switching function that is the heart of the optical cross-connect device of the present invention will be described. The basic principle is the application of “correlation matching of laser speckle patterns emitted from an optical waveguide”. In this case, the cross-correlation function is given by Equation 1.
[0014]
[Expression 1]
C _{i , j} = P _i × P _j
C _{i , j} : Cross-correlation function P _i : Speckle pattern emerging from multimode optical waveguide when no externally applied voltage is applied P _j : Speckle pattern emerging from multimode optical waveguide when externally applied voltage is applied [0015]
According to the theorem, 1 (MAX) when i = j, that is, the maximum when the patterns match 0 (MIN) when i ≠ j, the minimum when the patterns do not match. The optical signal input from the input optical fiber 1 generates a required speckle pattern by a control voltage applied to the electrode 10 on the multimode optical waveguide 4, and an address is selected by the holographic filter 5 for output. Connected to the optical fiber 2.
[0016]
The functions of the method shown in the previous section will be explained using specific examples.
[0017]
[Creation of holographic filter]
FIG. 6 is a diagram showing a principle of creating a holographic filter. When forming the hologram H1, _one of the beams obtained by dividing the laser beam 9a output from the laser device 6 by the beam splitter 7b is used for signal control from the input side. The speckle pattern corresponding to each applied voltage is generated by passing through the multimode optical waveguide 4 below the electrode 10. Here, when these are combined into one multi-mode optical waveguide 4 as V ₁₁ , the speckle pattern S ₁ of the beam emitted therefrom becomes the sum of the respective speckle patterns as shown in the figure. This beam hologram occurs optical interference in this intersection is irradiated at right angles to from S ₁ to the other beam divided by the beam splitter 7b as the reference light R ₁ is formed. Similarly speckle pattern S ₂ generated as V _21, to interfere with the reference wave R ₂ to form a hologram H _2. Thereafter, the same number of holograms are formed by the same method to complete one holographic filter 5.
[0018]
[Diffraction of light by holographic filter]
FIG. 7 is a diagram showing the principle of light diffraction by the holographic filter. Now, assuming that two input signals receive applied voltages of V ₁₂ and V ₂₁ , respectively, a speckle pattern input to the holographic filter 5. Becomes S. When passing through the existing holograms H ₁ and H ₂ , the beam is diffracted at a location that satisfies the above-described conditions of the cross-correlation function and enters the optical waveguide on the output side. That is, the beam is switched to a necessary position by controlling the voltage applied to the electrode 10.
[0019]
【The invention's effect】
As described above, when the optical cross-connect device of the present invention is used for an optical switch in a WDM transmission device, the speckle pattern is changed at high speed by using the photoelectric effect, and passes through a preset holographic filter. It is possible to perform path conversion, that is, cross connect, between the input side optical signal and the output side optical signal at high speed simply by making them. The holographic filter is characterized in that it is formed before the operation of the device, and therefore has an excellent feature that does not affect the switching speed during operation. Since a large number of speckle patterns can be created as required, the number of channels can correspond to hundreds to thousands of channels, and it can handle very large-scale WDM transmission devices. Furthermore, the switching speed is very high. Therefore, it is possible to achieve a great effect that the construction of the next-generation photonic network can be promoted rapidly.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an entire optical cross-connect device according to the present invention.
FIG. 2 is a conceptual diagram of an optical switch for applying an electro-optic effect to a multimode optical waveguide in the optical cross-connect device of the present invention.
3 is a cross-sectional view showing a positional relationship between an electrode for an electro-optic effect and a multimode optical waveguide in FIG. 2. FIG.
FIG. 4 is a plan view conceptually showing a state in which a laser beam input in a single mode generates a speckle pattern determined by an electrode in a multimode optical waveguide and is input to the holographic filter from the multimode optical waveguide. is there.
FIG. 5 is an arrangement diagram of an optical system when creating a holographic filter in the optical cross-connect device of the present invention.
FIG. 6 is a diagram showing the principle of creating a holographic filter.
FIG. 7 is a diagram showing the principle of light diffraction by a holographic filter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical fiber for input 2 Optical fiber for output 3 Multimode optical waveguide support substrate 4 Multimode optical waveguide 5 Holographic filter 6 Laser apparatus 7a Lens system 7b Beam splitter 7c Reflective mirror 7d Reflective mirror drive apparatus 7e Lens array 8 Power supply apparatus 9 Laser beam 10 Multimode waveguide upper electrode 10a Multimode waveguide lower electrode 11 Slitter 12 AWG multiplexer / demultiplexer 13 Dichroic mirror 14 Address photodetector

Claims (6)

An electrode (10) was formed on M input optical fibers (1), N output optical fibers (2), and a multimode optical waveguide support substrate (3) for speckle mode conversion installed in the middle. Multi-mode optical waveguide (4) with M input and 1 output and speckle pattern hologram for optical path address selection were formed at regular intervals by setting switching conditions in the light traveling direction of nonlinear optical crystal or organic material An optical cross-connect device comprising a holographic filter (5). A speckle pattern for an optical cross-connect device that switches the input light to a predetermined optical path address is formed in advance in the holographic filter (5), so that it is oscillated from a laser device (6) that oscillates a uniform mode laser beam. The laser beam (9) is converted into uniform parallel light having a constant diameter by the lens system (7a), and the parallel light is divided into two paths by the beam splitter (7b). ) Passes through the lens array (7e) and the input optical fiber (1), generates a speckle pattern corresponding to the switching condition by the electro-optic effect in the multimode optical waveguide (4), and produces a nonlinear optical crystal or organic material. And the other parallel light (9b) becomes the non-linearity that becomes the holographic filter (5). 2 is output from the same light source by irradiating the non-linear optical crystal or organic material by a reflecting mirror (7c) attached to a reflecting mirror driving device (7d) that moves parallel to the crystal or organic material and moves left and right. The hologram in which the speckle pattern hologram is formed at a constant interval in the traveling direction of the light of the nonlinear optical crystal or organic material by crossing light in the nonlinear optical crystal or organic material to interfere with light in the optical path. Equipment for producing graphic filter (5) . Input light input from the M input optical fibers (1) is input to the multimode optical waveguide (4) via an AWG multiplexer / demultiplexer (12) and a dichroic mirror (13), Speckle patterns corresponding to different optical path addresses are applied to the input light propagating through each of the multimode optical waveguides (4) by the electrodes (10) formed on the multimode optical waveguide (4). The output optical fiber (2) is selectively selectively connected to the output optical fiber (2) only at locations that are generated by the voltage V _i (i = 1, 2,...) And coincide with the speckle pattern corresponding to the optical path address of the holographic filter (5). The optical cross-connect device according to claim 1, wherein an input is sent. The multimode optical waveguide support substrate (3) on which the multimode optical waveguide (4) for controlling the input light is formed has an optical signal λ _i (i = 1, 2,...) From the input optical fiber (1).・), For example, λ _{1 for} the first input fiber, λ ₂ for the next input fiber Further, the next input fiber is composed of a number of layers corresponding to each optical signal λ _i , such as λ ₃ , etc., and the upper part and the lower part of the multimode optical waveguide (4) of each layer are specified. Several upper electrodes (10) having a shape and a lower electrode (10a) as a counter electrode are respectively formed, and a control voltage output from the power supply device (8) is applied to selectively select a light path. The optical cross-connect device according to claim 3, wherein the optical cross-connect device is defined.   The laser beam (9a) passing through each multimode optical waveguide (4) has different specifications according to the voltage applied to the upper electrode (10) and the lower electrode (10a) and the number of optical path addresses. The optical cross-connect device according to claim 3 or 4, wherein the optical cross-connect device is linearly synthesized after being generated and incident on the holographic filter (5).   4. A constant voltage or a necessary analog voltage is applied between the upper electrode (10) and the lower electrode (10a) in a binary manner between the multimode optical waveguide (4) and the lower electrode (10a). The optical cross-connect device according to any one of 5.

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