Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-12-31
2004-10-19
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S247000, C359S223100
Reexamination Certificate
active
06806992
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro mirror unit to be used in e.g. an optical switching device for switching optical paths provided by optical fibers.
2. Description of the Related Art
In recent years, optical communications technology is utilized widely in a variety of fields. In the optical communications, optical fibers serve as a medium through which optical signals are passed. When the optical signal passing through a given optical fiber is switched to another optical fiber, so-called optical switching devices are used. In order to achieve high quality optical communications, the optical switching device must have such characteristics as high capacity, high speed and high reliability in switching action. In view of these, micro mirror units manufactured by micro-machining technology are very popular as a switching element to be incorporated in the optical switching device. The micro mirror units enable the switching operation without converting optical signals into electric signals between the optical paths on the input side and the output side of the optical switching device. This is advantageous to achieving the above-mentioned characteristics.
Optical switching devices utilizing micro mirror units manufactured by micro-machining technologies are disclosed, for example, in International Publication WO00/20899, and the article
Fully Provisioned
112×112
Micro-Mechanical Optical Crossconnect with
35.8
Tb/sec Demonstrated Capacity
(Proc. 25
th
Optical Fiber Communication Conf. Baltimore. PD12(2000).
FIG. 18
outlines an ordinary optical switching device
500
. The optical switching device
500
includes a pair of micro mirror arrays
501
,
502
, an input fiber array
503
, an output fiber array
504
, and a plurality of micro lenses
505
,
506
. The input fiber array
503
includes a predetermined number of input fibers
503
a
. The micro mirror array
501
is provided with the same number of micro mirror units
501
a
each corresponding to one of the input fibers
503
a
. Likewise, the output fiber array
504
includes a predetermined number of input fibers
504
a
. The micro mirror array
502
is provided with the same number of micro mirror units
502
a
each corresponding to one of the output fibers
504
a
. Each of the micro mirror units
501
a
,
502
a
has a mirror surface to reflect light. The orientation of the mirror surface is controllable. Each of the micro lenses
505
faces an end of a corresponding input fiber
503
a
. Likewise, each of the micro lenses
506
faces an end of a corresponding output fiber
504
a.
In transmitting optical signals, lights L
1
coming out of the input fiber array
503
a
pass through the corresponding micro lenses
505
, thereby becoming parallel to each other and proceeding to the micro mirror array
501
. The lights L is reflected on their corresponding micro mirror units
501
a
respectively, thereby directed toward the micro mirror array
502
. The mirror surfaces of the micro mirror unit
501
a
are oriented, in advance, in appropriate directions so as to direct the light L
1
to enter the desired micro mirror units
502
a
. Then, the light L
1
is reflected on the micro mirror units
502
a
, and thereby directed toward the output fiber array
504
. The mirror surfaces of the micro mirror units
502
a
are oriented, in advance, in appropriate directions so as to direct the light L
1
to the desired output fibers
504
a.
As described, according to the optical switching device
500
, the light L
1
coming out of the input fibers
503
a
reaches the desired output fibers
504
a
due to the reflection by the micro mirror arrays
501
,
502
. In this manner, a given input fiber
503
a
is linked to the relevant output fiber
504
a
in a one-to-one relationship. By appropriately changing the orientation, of the micro mirror units
501
a
,
502
a
, switching can be performed and the light L
1
can be directed toward the selected output fiber
504
a.
FIG. 19
outlines another ordinary optical switching device
600
. The optical switching device
600
includes a micro mirror array
601
, a fixed mirror
602
, an input-output fiber array
603
, and a plurality of micro lenses
604
. The input-output fiber array
603
includes a number of input fibers
603
a
and output fibers
603
b
. The micro mirror array
601
includes the same number of micro mirror units
601
a
each corresponding to one of the fibers
603
a
,
603
b
. Each of the micro mirror units
601
a
has a mirror surface for reflection of light, the orientation of the mirror surfaces being controllable. Each of the micro lenses
604
faces an end of a corresponding one of the fibers
603
a
,
603
b.
In transmitting optical signals, light L
2
coming out of the input fiber
603
a
passes through the corresponding micro lens
604
and is directed toward the micro mirror array
601
. The light L
2
is then reflected by a corresponding first micro mirror unit
601
a
, and thereby directed toward the fixed mirror
602
, reflected by the fixed mirror
602
, and then enters a corresponding second micro mirror unit
601
a
. The mirror surface of the first micro mirror unit
601
a
is oriented, in advance, in a predetermined direction so as to direct the light L
2
to enter a selected one of the micro mirror units
601
a
. Then, the light L
2
is reflected on the second micro mirror unit
601
a
, and thereby directed toward the input-output fiber array
603
. The mirror surface of the second micro mirror unit
601
a
is oriented, in advance, in a predetermined direction so as to direct the light L
2
to enter a predetermined one of the output fibers
603
b.
As described, according to the optical switching device
600
, the light L
2
coming out of the input fiber
603
a
reaches the desired output fiber
603
b
due to the reflection by the micro mirror array
601
and the fixed mirror
602
. In this manner, a given input fiber
603
a
is linked to the relevant output fiber
603
b
in a one-to-one relationship. With this arrangement, by appropriately changing the orientation of the first and the second micro mirror units
601
a
, switching can be performed and the light L
2
can be directed toward the selected output fiber
603
b.
According to the optical switching devices
500
,
600
as described above, the number of fibers increases with increase in the size of optical communications network. This means that the number of micro mirror units, or mirror surfaces, incorporated in the micro mirror array also increases. With a greater number of mirror surfaces, a greater amount of wiring is required to drive the mirror surfaces and therefore, an increased amount of area must be provided for the wiring per micro mirror array. If the mirror surfaces and the wiring pattern are to be formed in the same substrate, an increased amount of wiring requires an increased pitch between the mirror surfaces. As a result, the substrate itself or the micro mirror array as a whole must be big. In addition, an increase in the number of mirror surfaces tends to make it difficult to form the mirror surfaces together with the wiring pattern in the same substrate.
SUMMARY OF THE INVENTION
The present invention has been proposed under the circumstances described above. It is therefore an object of the present invention to provide a micro mirror unit capable of reducing the size-increasing tendency resulting from the increase in the number of mirror surfaces.
According to a first aspect of the present invention, there is provided a micro mirror unit provided with: a micro mirror substrate that includes a moving part, a first frame and torsion bars connecting the moving part to the frame, the moving part being provided with a mirror-formed portion; a wiring substrate formed with a wiring pattern; and an electroconductive spacer for electrically connecting the frame to the wiring pattern and for spacing the micro mirror substrate and the wiring substrate apart from each other.
With the above arrangement, the moving part (carrying a m
Kouma Norinao
Mizuno Yoshihiro
Nakamura Yoshitaka
Okuda Hisao
Sawaki Ippei
Schwartz Jordan M.
Stultz Jessica
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