Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2002-02-15
2003-01-07
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06504966
ABSTRACT:
CROSS-REFERENCE TO RELATED APLICATIONS
This application is based upon and claims priority of Japanese Patent Applications No. 2001-040006, filed in Feb. 16, 2001 and Japanese Patent Applications No. 2001-332169, filed in Oct. 30, 2001, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical deflecting element for deflecting the light, an optical switch module for switching a propagation destination of the light signal between a plurality of input ports and a plurality of output ports, a light signal switching device employing the optical switch module, and an optical wiring substrate having a mirror for changing the propagation direction of the light signal.
2. Description of the Prior Art
In recent years, the transmission band of the optical communication is increased steadily and also the higher speed and the larger capacity are accelerated conjointly with the progress of the WDM (wavelength division multiplexing) technology. In order to construct the hardware infrastructure of the optical fiber network in the trunk communication network, the light signal switching device f or switching the transmission destination of the optical signal is needed.
In th e prior art, the optical cross-connecting device that converts the light signal the electric signal once, then switches the transmission destination of the signal by the crossbar switch, and then converts the electric signal into the light signal once again is the mainstream as the light signal switching device. In this case, if the data transmission rate exceeds 10 Gb/s, it is difficult to construct the switching device by the electric switching elements like the prior art.
If the optical transmission path is switched by using the optical switching elements in place of the electric switching elements, the conversion between the light and the electricity is not needed and thus the optical cross-connecting device that does not depend on the rate (frequency) of the light signal can be constructed. At present, the optical switch module whose input port number is 32 and whose output port number is 32 (32×32 channels) is implemented. Also, there is the example in which the nonocclude switching network (light signal switching device) is constructed by connecting such optical switch modules in a multi-stage fashion.
In the optical switch module in the prior art, normally the movable micro mirror is employed as the optical switching element. That is, the propagation direction of the light signal is switched by controlling the direction of the micro mirror by the electric signal. The micro mirror can be formed by using the MEMS (MicroElectroMechanical System) technology. The optical switch module is constructed by arranging a number of micro mirrors in two directions (the X direction and the Y direction).
Also, the switching element (optical deflecting element) utilizing the electrooptic effect has been developed.
FIG. 1A
is a plan view showing the optical deflecting element in the prior art, and
FIG. 1B
is a sectional view showing the same (Patent Application Publication (KOKAI) Hei 9-5797). As shown in
FIGS. 1A and 1B
, in the optical deflecting element in the prior art, the optical waveguide
11
having the electrooptic effect is formed on the conductive or semi-conductive single crystal substrate
10
, and then the upper electrode
12
is formed thereon. The upper electrode
12
is formed as a wedge shape (right triangle shape) having a side that orthogonally intersects with the optical axis of the incident light (called a base hereinafter) and a side that obliquely intersects with the optical axis (called an oblique side hereinafter).
In the optical deflecting element constructed in this manner, as shown in
FIG. 1A
, the light is incident upon the optical waveguide
11
from the base side of the upper electrode
12
and is emitted from the oblique side of the upper electrode
12
. If the voltage is applied between the upper electrode
12
and the lower electrode while using the substrate
10
as the lower electrode, the refractive index of the optical waveguide
11
under the upper electrode
12
is changed to cause the difference in the refractive index of such portion among the periphery. The light passing through the optical waveguide
11
is refracted at the portion whose refractive index is changed and thus the traveling direction is changed. In other words, the outgoing direction of light can be controlled by changing the voltage that is applied between the upper electrode
12
and the substrate
10
.
Meanwhile, in the case that the light signal is transmitted between the optical devices, it is possible to connect the optical devices via the optical fibers if the number of the wirings (optical wirings) is small. However, if the number of the wirings is in excess of several hundreds to several thousands, it is advantageous from respects of the easiness of the connecting operation and the space to connect the optical devices by the optical waveguides rather than the connection via the optical fibers.
It is rarely the case that all the optical waveguides for connecting the optical devices can be formed by the straight line. Normally, the optical waveguides are formed to detour the electric parts, the electric wirings, the connectors, and other optical waveguides mounted on the substrate. In this case, since the light has the high straight traveling property, the optical waveguides must be formed along the curve having the large curvature or the propagation direction of light must be changed sharply by the reflection mirror.
If the optical waveguides must be formed along the curve having the large curvature, the layout space of the optical waveguides is increased. Therefore, there is the drawback that it is difficult to form a large number of optical waveguides. In contrast, if the reflection mirror is employed, there is the advantage that the optical waveguides of high density can be integrated. As the reflection mirror, there are the total reflection mirror that totally reflects the light based on the difference in the refractive index and the metal mirror that is formed of the metal film.
The inventors of the present invention consider that problems described in the following are present in the above optical switch module in the prior art.
In the optical switch module that is constructed by integrating the micro mirrors, a module size of the 32×32 channel module containing light input/output ports (fiber connectors), for example, becomes several tens cm square. In order to achieve the nonocclude optical cross-connecting device on a scale of 1000×1000 channels that is requested in the market, the optical switch modules must be constructed in a three-stage fashion by using 192 optical switch modules, for example.
Also, as described above, the wavelength division multiplexing (WDM) technology is employed to improve the throughput of the data transmission, and the light signal having plural wavelengths is transmitted collectively over one optical fiber. Therefore, the multiplied light signal must be passed through the optical branching filter to separate plural wavelengths into individual wavelengths before such multiplied light signal is input into the optical switch module. As the optical branching filter, there are the optical branching filter using the interference filter, the AWG (Arrayed Waveguide Grating) optical branching filter based on the waveguide technology, etc.
In addition, the optical multiplexer is needed to transmit the wavelength-multiplexed light signal once again after the propagation path of the light signal is switched by the light signal switching device. The optical multiplexer executes the multiplexing of the light signal based on the opposite principle to the optical branching filter.
Both the optical branching filter and the optical multiplexer are formed in the form of module and are connected to the optical switch module via the optical fiber. If the light signal switching device o
Aoki Tsuyoshi
Ishii Masatoshi
Kato Masayuki
Nishizawa Motoyuki
Sugama Akio
Coudert Brothers LLP
Fujitsu Limited
Ullah Akm E.
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