U.S. patent application number 09/921779 was filed with the patent office on 2003-02-06 for optical switch system and method for aligning optical axis therein.
Invention is credited to Horino, Masaya, Ishikawa, Tadaaki.
Application Number | 20030026011 09/921779 |
Document ID | / |
Family ID | 31995452 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030026011 |
Kind Code |
A1 |
Ishikawa, Tadaaki ; et
al. |
February 6, 2003 |
OPTICAL SWITCH SYSTEM AND METHOD FOR ALIGNING OPTICAL AXIS
THEREIN
Abstract
In an optical switch system for switching over plural input
lights and plural output lights corresponding thereto through
spatial optical connection therebetween, having: a first reflection
mirror to be directed with an input light and being controllable in
position thereof; a second reflection mirror disposed opposite to
the first reflection mirror, for reflecting the light reflected on
the first reflection mirror, so as to outputted it therefrom; means
for controlling positions of the first and second reflection
mirrors, respectively; and means for adjusting the position of the
first and second mirrors, which are controller by the controlling
means, wherein a reference light being substantially different from
the input light in wavelength is generated; both the reference
light and the input light reflect upon the first and second
reflection mirrors; and (c) optical intensity of the reference
light selectively diverged from the reflection light is detected,
thereby controlling positions of the first and said second
reflection mirrors, so as to obtain the maximum in optical
intensity of the input light.
Inventors: |
Ishikawa, Tadaaki;
(Tsuchiura, JP) ; Horino, Masaya; (Yasato,
JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
31995452 |
Appl. No.: |
09/921779 |
Filed: |
August 6, 2001 |
Current U.S.
Class: |
359/857 ;
359/298; 359/850 |
Current CPC
Class: |
G02B 6/359 20130101;
G02B 6/3512 20130101 |
Class at
Publication: |
359/857 ;
359/298; 359/850 |
International
Class: |
G02F 001/29; G02B
026/08; G02B 005/08; G02B 007/182 |
Claims
What is claimed is:
1. An optical switch system, for switching over plural input lights
and plural output lights corresponding thereto through spatial
optical connection therebetween, comprising: a first reflection
mirror to be directed with an input light and being controllable in
position thereof; a second reflection mirror disposed opposite to
said first reflection mirror, for reflecting the light reflected on
said first reflection mirror, so as to outputted it therefrom;
means for controlling positions of said first reflection mirror and
said second reflection mirror, respectively; and means for
adjusting the position of at least one of said first and second
mirrors, which are controller by said controlling means by means of
a reference light being substantially different from said input
light in wavelength thereof.
2. An optical switch system, as defined in the claim 1, wherein
said position adjusting means adjusts the position of at least the
one of said first and second mirrors, so that the input light,
reflecting upon said first reflection mirror and propagating onto
said second reflection mirror, comes to the maximum in the optical
intensity thereof.
3. An optical switch system, as defined in the claim 1, wherein
said position adjusting means adjusts the position of at least the
one of said first and second mirrors by means of difference in
intensity between the reference light irradiated upon said first
reflection mirror and the reference light propagating onto said
second reflection mirror.
4. An optical switch system, as defined in the claim 1, wherein in
an input side, there are further provided a reference light
generator means for generating the reference light therefrom and an
optic mixer for mixing the said input light and said reference
light to be irradiated upon said first reflection mirror, and in an
output side are provided an optic divider for selectively
reflecting said reference light thereupon so as to separate it form
said input light, and a light receiving means for detecting the
intensity of said reference light selected.
5. An optical switch system, as defined in the claim 1, wherein in
an input side, there are further provided a reference light
generator means for generating the reference light therefrom, an
optic mixer for mixing the said input light and said reference
light to be irradiated upon said first reflection mirror and means
for collimating said input light while dispersing said reference
light selectively, so as to be irradiated upon said first
reflection mirror, and in an output side is provided means for
selectively detecting irradiating position of said dispersed
reference light upon said second reflection mirror, wherein said
position adjusting means adjusts the position of said first
reflection mirror.
6. An optical switch system, as defined in the claim 5, wherein
said means for detecting the irradiating position of said dispersed
reference light upon said second reflection mirror comprises plural
numbers of light receiving elements, being disposed neighboring
with each other, around a central portion thereof where a
penetrating opening is formed for passing through the input
light.
7. An optical switch system, as defined in the claim 6, wherein
said plural numbers of light receiving elements are provided in
number of four (4).
8. An optical switch system, as defined in the claim 5, wherein on
a light path after said second reflection mirror, there is further
provided a light receiving element having plural numbers of
elements, being disposed neighboring with each other, around a
central portion thereof where a penetrating opening is formed for
passing through the input light, wherein said adjusting means
control the position of said second reflection mirror upon basis of
an output of said light receiving element.
9. An optical switch system, as defined in the claim 1, wherein in
an input side, there are further provided a reference light
generator means for generating the reference light therefrom and
means for collimating said input light and superimposing said
reference light from said reference light generating means thereon
in coaxial manner, so as to be irradiated upon said first
reflection mirror, and in an output side is provided light
receiving element for selectively detecting said reference light
from the light propagating through reflection upon said first and
said second reflection mirrors, wherein said position adjusting
means adjusts the position of at least one of said first and said
second reflection mirrors.
10. An optical switch system, as defined in the claim 9, wherein
said light receiving element comprises plural numbers of light
receiving elements, being disposed neighboring with each other,
around a central portion thereof where a penetrating opening is
formed for passing through the input light.
11. An optical switch system, as defined in the claim 10, wherein
said plural numbers of light receiving elements constructing said
light receiving element are in number of four (4) .
12. An optical switch system, as defined in the claim 10, wherein
there is further provided means for selectively removing said
reference light from the light irradiating upon said light
receiving element.
13. A method for aligning axis of an optic signal, in an optical
switch system for switching over plural input lights and plural
output lights corresponding thereto through spatial optical
connection therebetween, having: a first reflection mirror to be
directed with an input light and being controllable in position
thereof; a second reflection mirror disposed opposite to said first
reflection mirror, for reflecting the light reflected on said first
reflection mirror, so as to outputted it therefrom; means for
controlling positions of said first reflection mirror and said
second reflection mirror, respectively; and means for adjusting the
position of at least one of said first and second mirrors, which
are controller by said controlling means comprising the following
steps of: (a) generating a reference light being substantially
different from said input light in wavelength thereof; (b)
reflecting both said reference light generated and said input light
upon at least one of said first and said second reflection mirrors;
and (c) detecting optical intensity of said reference light
selectively diverged from said reflection light, and controlling
position of at least one of said first and said second reflection
mirrors, so that said input light is at maximum in optical
intensity thereof.
14. A method for aligning axis of an optic signal, as defined in
the claim 13, wherein said steps (a) to (c) are conducted when
switching-over operation of said optical switch system.
15. A method for aligning axis of an optic signal, as defined in
the claim 13, wherein in said step (b), said reference light is
superimposed with said input light, in coaxially therearound, to be
irradiated upon at least one of said first and said second
reflection mirrors.
16. A method for aligning axis of an optic signal, as defined in
the claim 15, wherein in said step (c), the position of at least of
said first and said second reflection mirrors are so controlled
that said reference light, being superimposed abound said input
light, comes to at a center of at least one of said first and said
second reflection mirrors.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an optical switch system
for switching optic signal to be used as an exchanger or switch in
an optical communication, and in particular, to an optical switch
system for enabling multi-channeling through spatial switching by
means of a three-dimensional (3-D) beam steering with using the 2-D
matrix and a method for aligning optical axis in such the switch
system.
[0002] Conventionally, accompanying with development of an optical
communication system with using an optic fiber, an optical switch
is adopted as a switch or exchanger of such the system. In
particular, with the demand for high-speed and large capacity of
the communication system, in recent years, the optical switch of
multi-channels, so-called an optical switch of matrix-type is
applied therein.
[0003] The optical switch of so-called a matrix-type is disclosed
as an example of a two dimensional (2-D) type, for example, in
Japanese Patent Laying-Open No. 2000-330044, wherein connection of
optic signals is exchanged or switched over on a plane. However,
though this 2-D type optical switch of the conventional art is
simple in the structure thereof, it has a limit in multiplexing of
channels because of the structure of aligning the optic fibers on
the plane, therefore in recent years, there is a strong demand for
an optical switch with using the spatial optical connection
therein, i.e., an optical switch of 3-D type, which can be
manufactured in compact and/or in small-sized.
[0004] In such the optical switch of such the spatial connection
type, being called by the 3-D, as is shown in Japanese Patent
Laying-Open No. 2000-247065, for example, a collimated light beam
is reflected upon a mirror, so as to switched over the optical
connection, in the structure thereof. For this reason, an accurate
control in position (or angle) of this reflection mirror is
important. However, only with the control in the position of the
mirror upon the basis of detected data from an angle sensor
attached thereto, it is impossible to fully absorb or dissolve an
influence due to thermal deformation of a housing, positional
shifting due to secular deterioration or aged change, and further
an error of the angle sensor, etc., therefore an efficiency is
lowered in connection of optic signals.
[0005] Therefore, according to the conventional art, in general,
after rough controlling on position of the mirror through an angle
control with using such the angle sensor, a portion of the light
beam for communication data, which passes through the optical
switch, is divided, i.e., from several to several tens % thereof,
to be received on a photo diode (hereinafter, by "PD") for
estimating an intensity of optical data, through a branch provided
on an output side of the system for separation of the optic signal,
and the mirror is finely adjusted on the position thereof, so that
the light appears the maximum intensity on the light received by
the PD for data light intensity estimating.
[0006] However, in the optical switch according to the conventional
art mentioned above, the difference in the optical intensity
between an input light and an output light comes to be the optical
loss within said the system. In general, there is provided criteria
on the optical intensity of the communication light within the
system. If the optical loss is large in the communication path,
including the optical switch therein, the optic signal passing
through such the optical switch cannot be transmitted, as it is, in
the form of an output, in such the case, there is necessity of
further operation, such as, amplification for the optical intensity
thereof with using an optical amplifier, etc. This brings the
optical switch system to be complex in the structure and to be
large in sizes thereof. For this reason, it is necessary to reduce
the optical loss therein, to be as small as possible.
[0007] By the way, as sources of the optical loss in the optical
switch of such the spatial connection type, utilizing the mirror
therein, there exist various losses, such as, a connection loss in
an optic fiber to the optical switch, a loss due to transparency or
transmittivity of a collimator lens for collimating the input
light, a reflection loss upon the reflection mirror, a loss when
re-forming image by the collimated light in an output side, and so
on. For this reason, if there is further provided the optical
branch for the position control of the reflection mirror mentioned
above, since the communication light is consumed, in a part
thereof, from a several to several tens percent (%), it constitutes
a very large one, of the optical loss in such the optical
switch.
[0008] Also, in the conventional art, for assuming that the optical
connection is in an optimal condition, i.e., the optical intensity
is at the maximum, it is necessary to search or find out the mirror
position that comes up to the maximum in the optical intensity,
while swinging the reflection mirror slightly in a certain degree,
so as to change the optic path thereby. However, with this method,
the optical intensity is also changed on the communication light
during the search operation of the optimal position, therefore
there is also a problem, in practical viewpoint.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object according to the present invention
is, for dissolving such the problems of the conventional arts as
mentioned above, thus, to provide an optical switch system, having
no such the optical loss irrespective of searching of the
reflection mirror, with superior optical connection efficiency,
being suitable to be used as the switch or exchanger in the optical
communications, and further enabling multiplex channel
corresponding to the current tendency of high speed and large
capacity in the optical communications, and further being able to
be compact and small-sized, and also to provide a method for
aligning optical axis in such the switch system.
[0010] According to the present invention, for accomplishing the
above-mentioned object, firstly, there is provided an optical
switch system, for switching over plural input lights and plural
output lights corresponding thereto through spatial optical
connection therebetween, comprising: a first reflection mirror to
be directed with an input light and being controllable in position
thereof; a second reflection mirror disposed opposite to said first
reflection mirror, for reflecting the light reflected on said first
reflection mirror, so as to outputted it therefrom; means for
controlling positions of said first reflection mirror and said
second reflection mirror, respectively; and means for adjusting the
position of at least one of said first and second mirrors, which
are controller by said controlling means by means of a reference
light being substantially different from said input light in
wavelength thereof.
[0011] Also, according to the present invention, in the optical
switch system as mentioned in the above, wherein said position
adjusting means adjusts the position of at least the one of said
first and second mirrors, so that the input light, reflecting upon
said first reflection mirror and propagating onto said second
reflection mirror, comes to the maximum in the optical intensity
thereof.
[0012] Also, according to the present invention, in the optical
switch system as mentioned in the above, wherein said position
adjusting means adjusts the position of at least the one of said
first and second mirrors by means of difference in intensity
between the reference light irradiated upon said first reflection
mirror and the reference light propagating onto said second
reflection mirror.
[0013] And, according to the present invention, in the optical
switch system as mentioned in the above, wherein in an input side,
there are further provided a reference light generator means for
generating the reference light therefrom and an optical mixer for
mixing the said input light and said reference light to be
irradiated upon said first reflection mirror, and in an output side
are provided an optic divider for selectively reflecting said
reference light thereupon so as to separate it form said input
light, and a light receiving means for detecting the intensity of
said reference light selected.
[0014] Further, according to the present invention, in the optical
switch system as mentioned in the above, wherein in an input side,
there are further provided a reference light generator means for
generating the reference light therefrom, an optic mixer for mixing
the said input light and said reference light to be irradiated upon
said first reflection mirror and means for collimating said input
light while dispersing said reference light selectively, so as to
be irradiated upon said first reflection mirror, and in an output
side is provided means for selectively detecting irradiating
position of said dispersed reference light upon said second
reflection mirror, wherein said position adjusting means adjusts
the position of said first reflection mirror.
[0015] In addition thereto, according to the present invention, in
the optical switch system as mentioned in the above, wherein said
means for detecting the irradiating position of said dispersed
reference light upon said second reflection mirror comprises plural
numbers of light receiving elements, being disposed neighboring
with each other, around a central portion thereof where a
penetrating opening is formed for passing through the input
light.
[0016] Further in addition thereto, according to the present
invention, in the optical switch system as mentioned in the above,
wherein said plural numbers of light receiving elements are
provided in number of four (4).
[0017] Also, according to the present invention, in the optical
switch system as mentioned in the above, wherein on a light path
after said second reflection mirror, there is further provided a
light receiving element having plural numbers of elements, being
disposed neighboring with each other, around a central portion
thereof where a penetrating opening is formed for passing through
the input light, wherein said adjusting means control the position
of said second reflection mirror upon basis of an output of said
light receiving element.
[0018] Also, according to the present invention, in the optical
switch system as mentioned in the above, wherein in an input side,
there are further provided a reference light generator means for
generating the reference light therefrom and means for collimating
said input light and superimposing said reference light from said
reference light generating means thereon in coaxial manner, so as
to be irradiated upon said first reflection mirror, and in an
output side is provided light receiving element for selectively
detecting said reference light from the light propagating through
reflection upon said first and said second reflection mirrors,
wherein said position adjusting means adjusts the position of at
least one of said first and said second reflection mirrors.
[0019] And, according to the present invention, in the optical
switch system as mentioned in the above, wherein said light
receiving element comprises plural numbers of light receiving
elements, being disposed neighboring with each other, around a
central portion thereof where a penetrating opening is formed for
passing through the input light.
[0020] Further, according to the present invention, in the optical
switch system as mentioned in the above, wherein said plural
numbers of light receiving elements constructing said light
receiving element are in number of four (4).
[0021] In addition thereto, according to the present invention, in
the optical switch system as mentioned in the above, wherein there
is further provided means for selectively removing said reference
light from the light irradiating upon said light receiving
element.
[0022] Also, according to the present invention, also for
accomplishing the above mentioned object, there is further provided
a method for aligning axis of an optic signal, in an optical switch
system for switching over plural input lights and plural output
lights corresponding thereto through spatial optical connection
therebetween, having: a first reflection mirror to be directed with
an input light and being controllable in position thereof; a second
reflection mirror disposed opposite to said first reflection
mirror, for reflecting the light reflected on said first reflection
mirror, so as to outputted it therefrom; means for controlling
positions of said first reflection mirror and said second
reflection mirror, respectively; and means for adjusting the
position of at least one of said first and second mirrors, which
are controller by said controlling means comprising the following
steps of: (a) generating a reference light being substantially
different from said input light in wavelength thereof; (b)
reflecting both said reference light generated and said input light
upon at least one of said first and said second reflection mirrors;
and (c) detecting optical intensity of said reference light
selectively diverged from said reflection light, and controlling
position of at least one of said first and said second reflection
mirrors, so that said input light is at maximum in optical
intensity thereof.
[0023] And, according to the present invention, in the method for
aligning axis of an optic signal as mentioned in the above, wherein
said steps (a) to (c) are conducted when switching-over operation
of said optical switch system.
[0024] Further, according to the present invention, in the method
for aligning axis of an optic signal as mentioned in the above,
wherein in said step (b), said reference light is superimposed with
said input light, in coaxially therearound, to be irradiated upon
at least one of said first and said second reflection mirrors.
[0025] And, according to the present invention, in the method for
aligning axis of an optic signal as mentioned in the above, wherein
in said step (c), the position of at least of said first and said
second reflection mirrors are so controlled that said reference
light, being superimposed abound said input light, comes to at a
center of at least one of said first and said second reflection
mirrors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Those and other features, objects and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings wherein:
[0027] FIG. 1 is a view for showing the structure of an optical
switch system, a 2.times.2 matrix switch, according to a first
embodiment of the present invention;
[0028] FIG. 2 shows a flowchart for showing a method for aligning
an optical axis in the optical switch system shown in the FIG. 1
according to the present invention;
[0029] FIG. 3 shows a graph of the wavelength-transmittivity
(permeability) curve of a reference light wavelength band
reflection filter of an optic divider in the optical switch system
shown in the FIG. 1;
[0030] FIG. 4 shows an example of the structure of the optic
divider, which uses the reflection filter having the characteristic
curve shown in the FIG. 3 therein;
[0031] FIG. 5 is a view for showing the structure of another
optical switch system, a matrix switch, according to a second
embodiment of the present invention;
[0032] FIG. 6 is a cross-section view for showing a positional
relationship between a four(4)-divided light receiving element with
an opening and a second reflection mirror, in the optical switch
system shown in the FIG. 5;
[0033] FIG. 7 is a view for showing a principle of the control on
optical position in the optical switch system shown in the FIG. 5,
in which is applied the four(4)-divided light receiving element
shown in the FIG. 6;
[0034] FIG. 8 is a cross-section view for showing a positional
relationship between the four(4)-divided light receiving element
and a collimator lens provided at an output side in the optical
switch system shown in the FIG. 5;
[0035] FIG. 9 is a view for showing the structure of other optical
switch system, i.e., also a matrix switch, according to a third
embodiment of the present invention;
[0036] FIG. 10 is a cross-section view of a collimated
communication light-coaxial reference light-forming device, which
is used in the third embodiment mentioned above;
[0037] FIG. 11 is a view for showing an example of a pattern in
projection of the light, which is produced by the collimated
communication light-coaxial reference light-forming device shown in
the FIG. 10 mentioned above; and
[0038] FIG. 12 is a view for showing an example of the condition,
where the light from the collimated communication light-coaxial
reference light-forming device shown in the above FIG. 10 is
irradiated upon the four(4)-divided light receiving element
mentioned above.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0039] Hereinafter, explanation will be given on embodiments of the
present invention, by referring to the attached drawings.
[0040] First of all, FIG. 1 attached herewith shows the structure
of a so-called 2.times.2 optic matrix switch, according to a first
embodiment of the present invention. In this figure, a reference
numeral 1 indicates an optical switch system, 2a a first reflection
mirror, 2b a second reflection mirror, 2c a reflection mirror
surface, 3a a collimator lens of input side, 3b a collimator lens
of output side, 4 a housing of optic matrix switch, 5 a mirror
position controller circuit, 5a a mirror driver signal, 5b a mirror
angle signal, 5c a mirror driver circuit, 6 an optical intensity
detector circuit for a reference light, 6a a light source for a
reference optic beam, 6b a light receiving element, 6c an optical
intensity signal, 7a a mixer, 7b a divider, 7c a reflection-type
filter for reference light wavelength, 8 an optic path for
reference light, 9 an optic path for communication light, 10a an
input connector, 10b an output connector, 11 a switching circuit of
optical switch, and 11a a switching signal for optical switch,
respectively.
[0041] In the present embodiment, two (2) pieces of reflection
mirrors 2a and 2b are provided, and on each of those mirrors 2a or
2b is provided an angle sensor (not shown in the figure) for
measuring an angle of thereof. Further, data for positions or
angles of those reflection mirrors 2a and 2b, corresponding to
respective optic paths between inputs and outputs thereof, are
stored or memorized in a mirror position controller circuit 5, in a
form of initial values thereof, in advance. Also, in this figure,
for easy looking and understanding thereof, one of the two (2)
optic paths is removed from the figure, on the way from the input
to the output.
[0042] Each broken line, in the figure, indicates an optic path 8
for the reference light, including one defined within the optical
fiber, on the other hand, each thick and solid line indicates an
optic path 9 for the communication light, also including one
defined within the optical fiber therein. In ordinal, a light
laying within a wavelength band from 1,200 nm to 1,600 nm is used
as that communication light, but in more details thereof,
practically, the light laying in a wavelength band of 1,310 nm or
of 1,550 nm, in many cases. Further, for example, a semiconductor
laser device is suitable as a light source thereof.
[0043] On the other hand, for the reference light, a light is used
of wavelength band being different apparently and substantially
from the communication light mentioned above, i.e., lower than
1,000 nm, not to appear on the communication light, namely for
obtaining good separation between them. In particular, if using a
visual light ray laser of wavelength being equal or less than 680
nm, since a semiconductor laser is applicable as the light source
thereof which can be ordinarily available on the market, it is
possible to obtain the light source with relatively cheap price for
it, and further, this is particularly preferable, since a cheap
semiconductor light receiving element (i.e., a photo diode,
hereinafter by PD) of Si group can be applied as an optical
detector used for detecting the laser light.
[0044] Also as the divider 7b, it is possible to apply a wavelength
selective reflection filter, which is practically used, for
example, in a video camera, and so on. Adoption of such the
technology being available on the market enables the system to be
realized with relatively cheap prices. Further, the collimator
lenses 3a and 3b are provided for obtaining a parallel light or a
light ray being nearly equal to that from the output light emitted
from the optic fiber forming an optic path in the system, and in
many cases, each of them is constructed with a combination of
plural numbers of lenses, or a lens of varied refractive index type
or a rod lens, etc.
[0045] The communication light passing through this collimator lens
3a in an input side directs toward a first reflection lens 2a,
which is correspondingly located just below thereof. On the other
hand, the light reflecting upon the second reflection light 2b is
controlled to direct toward a collimator lens 3b in an output side,
which is located correspondingly just above thereof, therefore the
both light rays are in a relationship of being parallel with each
other. With the reflection mirrors mentioned above, because the
light used as the communication light lies in the wavelength band
from 1,200 nm to 1,600, i.e., within so-called a region of infrared
light, optimally it is a flat film made of material, in particular
gold (Au), however in the place thereof, it may be formed with a
film made of aluminum, since it is also possible to obtain high
reflectivity for the communication light in that infrared region
with the film made of material, i.e., aluminum, and this is
advantageous economically.
[0046] Also for driving of the reflection mirrors 2a and 2b
mentioned above, it is common to apply an attracting or absorbing
power due to the dielectric force, a power due to the piezo effect,
the electromagnetic power, and so on. In particular, the driving
method of applying the dielectric force is advantageous, since only
a small amount of current is sufficient for the driving, and/or
that of applying the electromagnetic power has also an advantage
that strong driving power can be generated thereby.
[0047] Next, explanation will be given by referring to FIG. 2
attached herewith, on the operations of the optical switch system,
the structure of which was mentioned in the above. In particular,
this FIG. 2 shows a flowchart of a method for aligning an optical
axis in the optical switch system.
[0048] First of all, when the optical switch switching signal 11a
is outputted, instructing to connect a certain input to a
corresponding output, and it is inputted from an outside to the
optical switch switching circuit 11 (step S 21), the mirror
position controller circuit 5 issues or outputs an order or
instruction to the driver 5c, for changing the position of the
reflection mirrors while compensating them through data obtained
from the angle sensors attached to the reflection mirror position
which are predetermined and stored in advance therein, and with
this, the driver 5c drives the reflection mirrors 2a and 2b into
the initial position of them which are memorized in advance (step
S22).
[0049] With such the mirror position control as mentioned above,
for example, the communication light 9 inputted from an outside
through the optic fiber is mixed (or superimposed) with the
reference light 8 (see broken lines in the above FIG. 1) generated
by the reference light source 6a in the mixer 7a. After being
collimated by the collimator lens 3a, this mixed light reflects
upon the first reflection mirror 2b to be directed toward the
second reflection mirror 2b, and further reflects thereupon. Then,
this light is guide into the optical fiber which is provided within
the system as a wave-guide, through the collimator lens provided in
an output side, again.
[0050] Thereafter, the mixed light led into the optical fiber is
guided into an inside of the optic divider 7b, and only the
reference light is divided and taken out from it through the
function of the filter for reflecting the wavelength band of the
reference light (i.e., reflection filter for reference light
wavelength band) which is provided within an inside thereof,
thereby to be guided into the light receiving element 6b through an
optical fiber, too. On the other hand, the communication light
passing through the above-mentioned optic divider 7b is outputted
to an outside through the connector 10b provided in the
outside.
[0051] Further, the reflection filter for reference light
wavelength band in the above-mentioned optic divider 7b has such a
wavelength-transmittivity (permeability) characteristic curve as
shown in FIG. 3, for example. Namely, this reflection filter passes
the communication light of the wavelength from 1,200 nm to 1,600
nm, through it, and it reflects the reference light of the visible
light wavelength band lower than 680 nm, thereon, but not passing
it therethrough, thereby enabling effective separation of the light
of the wavelength.
[0052] Also, as an example of the structure of this optic divider
7b, as shown in attached FIG. 4, a slit 14 is formed on the way of
the straight line portion of the wave-guide 12 made from a quartz
or Si substrate or made of organic resin, being inclined a little
bit to this straight line, and a reflection filter 13 for the
reference light wavelength band is inserted into an inside thereof.
Furthermore, a wave-guide 16 is provided in the opposite direction,
with inclination of an angle (.theta.) being same to the angle 15
(.theta.) of the wave-guide 12 with respect to this slit 14.
[0053] With the optic divider 7b of such the structure, the
communication light advancing (or propagating) within the optic
wave-guide 12 penetrates through the filter 13 mentioned above to
be outputted, however the reference light is guided into the
wave-guide 16 for the reference light through total reflection
thereof upon the filter 13 mentioned above. Other than this, there
are methods as the principle of the optic divider mentioned above,
such as, a MZ type optic divider and utilizing of a prism, etc.
[0054] Next, the intensity signal of the reference light received
upon the above-mentioned light receiving element 6b is compared and
inspected within the reference light intensity detector circuit 6.
Herein, because of a possibility that the initial values of the
reflection mirrors memorized in advance into the mirror position
controller circuit 5 may be shifted in the position or angle
thereof due to temperature and/or secular changes, and influences
of noises, etc., those initial positions (or angles) necessarily do
not bring about the optimal optic connection.
[0055] Then, turning back to the FIG. 2 mentioned above again, the
reflection mirror makes a slight movement (a tremor) thereof (step
S23). Thereafter, a decision is made on whether the reference light
received upon the light receiving element 6b shows the maximum
value of optical intensity or not (step S24). If being decided to
be at the maximum in optical intensity of the reference light
("yes") in the decision, the initial position of reflection mirror,
which is stored in advance into the mirror position controller
circuit 5, is corrected by using that position bringing about the
maximum optical intensity of the reference light (step S 24), and
then finishing the series of processes for the switching operation
(step S 25). On the other hand, when not decided at the maximum
("no") in the optical intensity of the reference light, the process
turns back to the step S23, again, and repeats the steps S23 and
S24, continuingly until when the reference light shows the maximum
value in the optical intensity thereof.
[0056] In this manner, according to the optical switch system and
the method for aligning the optic axis therein of the present
invention, the optical intensity is intestinally shifted, on the
reference light that is received upon the light receiving element
6b, by making the reflection mirror stirring (the slight movement)
in the angle thereof, thereby determining the angle of the
reflection mirror for obtaining the maximum optical intensity
within the reference light intensity detector circuit 6. And, once
the angle (i.e., the position) of the reflection mirror for
bringing about the maximum optical intensity is determined, the
position is memorized as a new initial potion therein.
[0057] According to such the method for aligning the optical axis
as was mentioned in the above, it is possible to start the position
control of the reflection mirrors from the values being nearer to
the position (i.e., the angle) of the reflection mirror bringing
about the maximum optical intensity than before, i.e., the preset
value stored in advance, in the switching operation for the next
time in the optical switch system. Further, the present embodiment
shown herein is that, in which the present invention is applied
into the 2.times.2 optic matrix switch, however the present
invention is also applicable, further into other optical switch
system of a multi-channel optic matrix switch, provided that
conditions are prepared for the maximum driving angle, degree of
horizontality between the collimated light rays, and dispersion of
the reflection mirror, etc. For example, in the case of applying it
into the a 32.times.32 optic matrix switch, the following condition
must be satisfied, on calculation, the distance between the
neighboring reflection mirrors is about 2 mm, the distance between
the first and second reflection mirrors about 100 mm, and the
driving angle of the reflection mirrors about .+-.10.degree., and
so on.
[0058] As apparent from the above, with the optical switch system
according to the present invention, since the position (i.e., the
angle) of the reflection mirrors can be always kept at the optimal
position by means of the method for aligning the optic axis thereof
mentioned above, although there is a possibility that it may be
shifted or changed due to the secular changes and/or the change of
temperature in actual circumferences where it is practically
applied into, etc., even in optical connection path in the system
being determined at the optimal value once (for example, the time
of shipment of the product), therefore, it is possible to obtain
the condition for the optimal connection, though it may change the
optical intensity of the communication light but only a little bit,
during the control operation thereof.
[0059] Next, FIG. 5 also shows the structure of the matrix-type
optical switch system, according to a second embodiment of the
present invention, briefly. In this figure, also one of the two (2)
optic paths from the input to the output is removed from, for easy
looking and understanding thereof.
[0060] In this second embodiment, the positional relationship
between each the collimator lens and the reflection mirror is same
to that mentioned in the above. However, in the present embodiment,
intentionally, the material is selected to use for forming the
collimator lenses 3a and 3b mentioned above, which brings about a
large difference in the refractive index with respect to the
wavelength, i.e., the material having large chromatic aberration.
In the case where the collimator lens formed of such the material
is so constructed that a collimated parallel light or that near to
this can be obtained from the light beam at wavelength of the
communication light, to be applied therein, then the reference
light, i.e., the other light beam used in this system, is also
collimated through the collimator lens, however as a result of the
chromatic aberration thereof, it comes to be such a diffused light
18, as depicted by broken lines in the figure, around the center of
the communication light (depicted by the thick solid line in the
figure). Also, in the present embodiment, although both the first
and second reflection mirrors 2a and 2b are not equipped with angle
sensors therewith, however those may be equipped with, depending
upon the necessity thereof.
[0061] With such the structure as was mentioned above, as apparent
from the figure, though a reflection mirror surface 2c on the first
reflection mirror 2a has an area being sufficient to cause the
total reflection upon all the reference light 18 diffused in the
collimator lens 3a thereon, on the other hand, a reflection mirror
surface 2c on the second reflection mirror 2b has only an area
thereof, though being sufficient to cause the total reflection upon
all the communication light 17 which is not diffused in the
above-mentioned collimator lens on it, but to cause the total
reflection only in a part, in particular, of the diffused reference
light 18.
[0062] Also, in a front of the second reflection mirror 2b, as
shown in attached FIG. 6, a four (4)-divided light receiving
element 19 is provided in parallel with the second reflection
mirror surface, which has an opening of a size for allowing the
communication light 17 not diffused to passing through it.
Therefore, a portion of the reference light 18 diffused in the
collimator lens 3a is unable to pass through the opening formed in
the four (4)-divided light receiving element 19, thereby being cut
down. Then, comparing those of the reference light, which are
received upon the respective portions of the four (4)-divided light
receiving element 19, in the optic intensity thereof, enables
determination of the position of the diffused reference light 18,
and further assumption of the position of the communication light
17, as well, since the communication light 17 which is not diffused
passes through at the central portion of the reference light 18.
Then, using of the position of the assumable communication light 17
allows the position of the first reflection mirror 2a to be
controlled, so that the communication light 17 is directed toward
the reflection surface 2c of the second reflection mirror 2b,
correctly. However, this four (4)-divided light receiving element
19 is disposed in such the position that does not obstruct the
change of position of the reflection mirror 2b .
[0063] This method will be explained in more details thereof, by
referring to attached FIG. 7. First, assuming that the direction
from the collimator lens 3a of input side toward the first
reflection mirror 2a corresponding thereto is the vertical
direction, then it is apparent that the axial direction
perpendicular to the vertical direction within the mirror surface
2c of the first reflection mirror 2a and the axial direction
perpendicular to the vertical direction within the mirror surface
2c of the second reflection mirror 2b are in parallel with each
other, from the positional relationship of the reflection mirrors
corresponding to the respective collimator lenses, for example,
which was mentioned about relating to the embodiment shown in FIG.
1 of the above. Accordingly, the optical intensity of the received
reference light 18 on the four (4)-divided light receiving element
19 disposed in the manner shown in this FIG. 7 should be symmetric
on both sides, when the communication light 17 is directed to the
center of the reflection mirror. However, as is shown in the above
FIG. 7 exemplarily, when the diffused reference light 18 irradiates
upon the four (4)-divided light receiving element 19, in
particular, on the right-hand side much more, it is apparent that
the position of the first reflection mirror 2a should be adjusted
so that the collimated communication light 17 is shifted to the
left-hand side on the figure.
[0064] Also, adjustment of the communication light 17 in a
direction of up and down will be explained, hereinafter. As was
shown in the FIG. 7 in the above, the optical intensity of the
reference light 18 is not symmetric in the direction up and down
upon the four (4)-divided light receiving elements 19, due to the
difference in the distance from the first reflection mirror 2a.
However, if obtaining the difference (i.e., value) of the optical
intensity of the reference light 18 in advance, which was detected
by elements in the direction of up and down on the four (4)-divided
light receiving element 19 when the communication light 17 comes up
to the center of the reference light 18, it is possible to adjust
or compensate the angle in the up and down direction of the first
reflection mirror 2a through an output from the four (4)-divided
light receiving element 19, but without the provision of the angle
sensor. This is also true in the case where the optical intensity
is not equal on both sides (the right-hand side and the left-hand
side), and application of the same method to the above-mentioned
enables correct control on the position of the first reflection
mirror in that case.
[0065] Thereafter, the collimated communication light 17 and a part
of the reference light 18, reflecting upon the second reflection
mirror 2a mentioned above, are directed toward the collimator lens
3b of output side corresponding thereto. According to the present
embodiment, in a front of the collimator lens 3b of the output side
(i.e., on the side of the second reflection mirror 2b) is also
provided or positioned a four (4)-divided light receiving element
20, in which is opened at the central portion thereof an opening of
the diameter being at least necessary for passing the collimated
communication light 17 therethrough. Namely, herein also, it is
possible to obtain the position control of the second reflection
mirror 2b, by the method similar to that of the position control of
the first reflection mirror 2a by use of the four (4)-divided light
receiving element 19.
[0066] As was mentioned in the above, the position control by use
of the four (4)-divided light receiving element(s) 19 and/or 20,
since the communication light can pass through those openings as it
is, enables much more suppression of the optical loss therein,
comparing to the embodiment shown in the FIG. 1 mentioned above.
However, in general, the reference light 18 forming an image on the
collimator lens 2b on output side is fully small in the size (i.e.,
diameter), but further provision of a filter, in front of the
collimator lens 3b of the output side, for cutting off this
reference light, enables prevention of the reference light from
being superimposed or appearing as noises thereon, with
certainty.
[0067] Also, the dived light receiving element(s) 19 and/or 20, as
was mentioned previously, detects the reference light near to the
visible one, and the light receiving element(s) can be constructed
with a semiconductor light receiving element made of Si, being used
widely in various kind of electronic apparatuses, therefore it is
possible to construct or obtain such the light receiving element(s)
with good quality and cheaply. In the embodiment mentioned above,
the explanation was given about only the example of using the
divided light receiving element(s) 19 and/or 20, such as, into the
four (4)-divided light receiving element with opening, in more
concrete or detail, however, principally, a three (3)-divided light
receiving element with opening can also be applied as that light
receiving element, for example, in the place of the four(4)-divided
light receiving element. However, in this case, when obtaining the
shift direction of mirror position, other calculations will be
necessary, other than a simple calculation for comparison, in
addition thereto. For such the necessity of the further
calculation, obstruction, such as delay in the operation and/or
complexity of the circuit, can be prospected, therefore, from this
reason, it is preferable to utilize the four(4)-divided light
receiving element.
[0068] Furthermore, FIG. 9 also shows the structure of the
matrix-type optical switch system, according to a third embodiment
of the present invention, briefly. In this figure, in the same
manner as in the embodiment shown in the FIG. 5, only one of the
two (2) optic paths from the input to the output is shown in the
figure, but others are removed therefrom, for easy looking and
understanding thereof.
[0069] In the matrix-type optical switch system of this third
embodiment, as apparent from the figure, a collimated communication
light/coaxial reference light forming device 21 is adopted or
provided for mixing or combining the collimated communication light
and the reference light on the same axis, in the place of the
above-mentioned optic mixer 7a and the collimator lens 3a, under
the optimal condition of the optical path. The vertical line drawn
from this forming device 21 down to the first reflection mirror 2a
is also parallel to the vertical line drawn from the collimator
lens 3b for the output down to the second reflection mirror 2b,
however in this embodiment, the direction is opposite (in down
direction) to that of the embodiments mentioned above. With such
the structure, the plane including the mirror surface 2a of the
first reflection mirror 2a and the plane including the mirror
surface of the second reflection mirror 2b are in the cento- or
point symmetry around the central point on the optical path between
those reflection mirrors 2a and 2b .
[0070] Thus, according to this third embodiment, differing from the
embodiment shown in the FIG. 5, both the light hitting or
irradiating upon the reflection mirror in the vicinity of the
center thereof and that in the vicinity of the periphery thereof
have the same length or distance in the optical path from the
collimated communication light/coaxial reference light forming
device 21 to the collimator lens of output side. Accordingly, as
shown in FIG. 11 attached, irradiation of the reference light 18,
being collimated into the parallel light beam in the coaxial
relationship with respect to the communication light 17 which is
also collimated into the parallel light beam, brings about a circle
pattern of the reference light, as shown in FIG. 12 attached, upon
the upper surface of the four (4)-divided light receiving element
20, which is disposed in front of the collimator lens 3b of output
side. Thus, the optical intensity on each light-receiving element
comes to be equal to each other. Because of this, only controlling
the mirror position, so that each element detects the equal optical
intensity on the (4)-divided light receiving element 20, enables
control of directing the collimated communication light 17 into the
center of the opening. Thus, the adjustment by comparison of the
distribution of intensity of the light received under the optimal
condition is not necessitated, therefore being preferable. Also,
the shape of the projection pattern of light thereupon should not
be restricted only to such the circle one as mentioned above,
however it is needless to say, for example, an oval shape is also
able to bring about the same effect as was mentioned, which is in
symmetry with respect to a line, in the directions up and down and
both sides (the right-hand side and the left-hand side).
[0071] Also, as was mentioned in the above, in the structure of
this third embodiment, since the plane including the mirror surface
of the first reflection mirror 2a and the plane including the
mirror surface of the second reflection mirror 2b are disposed in
the positional relationship of the cento- or point symmetry
relationship to each other, the positions of the both mirror
surfaces are controlled, so as to be in the point symmetry
relationship to each other, therefore the control can be
simplified.
[0072] Further, the collimated communication light 17 and the
reference light 18 coaxial therewith, which are formed in the
collimated communication light/coaxial reference light forming
device 21, are shown in FIG. 10 attached. As is shown in the
figure, on the way of the communication light 17 collimated into
the parallel light beam through the collimator lens 3a of input
side, a wavelength-selective permeation/reflection filter 23 is
positioned inclining with an angle 450 thereto. On the other hand,
the reference light 18a is irradiated, which is generated by a
collimated reference light generator 22 and collimated into a
parallel light beam to be larger in the beam diameter and the
cross-section area than the above-mentioned communication light 17,
so that the center thereof comes up to a point where the
communication light can pass through the wavelength-selective
permeation/reflection filter 23. Also, as the wavelength-selective
permeation/reflection filter 23 is selected to one that can
penetrate the light beam of wavelength (from 1,200 nm to 1,600 nm)
of the communication light therethrough, but reflects that of
wavelength (equal or lower than 1,000 nm) of the reference light
thereupon. In more details, that having the same wavelength
characteristics to those of the reflection-type filter 7c for the
reference light wavelength shown in the FIG. 1 may be suitable for
it.
[0073] In this manner, in the optical switch system according to
the present invention, the reference light is utilized as that for
accurate determination of the reflection mirror(s), which is
different in the wavelength from the communication light. Due to
the difference in the wavelength band, both the reference light and
the communication light are free from being mixed up with each
other. In this manner, with the system, in which only the reference
light for the purpose of axial aligning is detected, after passing
through the same optical path of the communication light, it is
possible to reduce the loss of the communication light. Further, in
general, an optical coupler or mixer is needed to couple or
superimpose the reference light and the communication light with
each other, however the loss of the communication light in this
optical coupler is the penetration loss. Or, in the place of the
optical branch, an optical divider is necessary, for example,
however with the provision of such the filtering function of
penetrating through or reflecting the specific wavelength, it is
possible to suppress attenuation of the communication light, as
well as to separate only the reference light therefrom. Since this
reference light divided passes through the same optical path of the
communication light, it is possible to adjust or control the
position of the reflection mirror(s), so that the optical
connection within the system comes to be the optimal, by checking
the optical intensity of the reference light and controlling the
position of the reflection mirror upon the basis of the optical
intensity thereof.
[0074] Furthermore, daring to select the collimator lens of input
side being large in the chromatic aberration thereof, while the
aberration to the light beam of wavelength of the reference light
to be largely different, comparing to that of the communication
light, makes the reference light much more diffused around the
center of the communication light. On the other hand, the light
receiving element is provided on the second reflection mirror
located in the output side, which is divided into at lease three
(3) or more pieces (preferably, into four (4) pieces) around the
opening gouged out at the position corresponding to the reflection
mirror surface thereon. With this, both the reference light and the
communication light reflecting upon the first reflection mirror are
directed toward the second reflection mirror, however herein, only
the collimated communication light passing through the
above-mentioned opening reaches onto the second reflection mirror,
while a portion of the diffused reference light is widen largely
than the opening mentioned above, therefore it can be detected by
the light receiving elements provided in three (3) or more in
number around this opening. And, the direction of the first
reflection mirror can be assumed upon basis of the fact that the
optical intensity detected of which one of those light receiving
elements is strong, thereby it is possible to control the position
of the first mirror, so as to direct the communication light
reflecting upon the first reflection mirror to the second
reflection mirror correctly.
[0075] Also, in the input side of the collimator lens of output
side, for use of image forming of the collimated light, namely on
the side of the second reflection mirror, the other light receiving
element is provided, which has an opening of size enough for
passing the collimated communication light therethrough, and is
divided into at lease three (3) or more pieces (preferably, into
four (4) pieces) around the opening. With this, a portion of the
communication light and the reference light can be detected by
those light receiving elements, when the second reflection mirror
is positioned appropriately, therefore it is possible to direct the
communication light reflecting upon the second reflection mirror
toward the collimator lens for use of image forming, correctly, by
controlling the position of the reflection mirror upon the basis
thereof. Namely, by use of the method mentioned above, it is
possible to reduce the attenuation of the communication light in
the optical switch much more, but without necessity of using the
optical diver on an optical output side thereof.
[0076] In the embodiments mentioned in the above, only the examples
are explained, in which the present invention is apply to the
2.times.2 matrix switch, however, the present invention should not
be restricted only to those, but it can be applied to an optical
matrix switch of N.times.N, for example.
[0077] As was fully explained in the above, according to the
present invention is, there are provided an optical swathing
system, having no such the optical loss irrespective of searching
of the reflection mirror, with superior optical connection
efficiency, being suitable to be used as the switch or exchanger in
the optical communications, and further enabling multiplex channel
corresponding current tendency of high speed and large capacity in
the optical communication, and further being able to be compact and
small-sized, and further a method for aligning optical axis in such
the switch system.
[0078] While we have shown and described several embodiments in
accordance with our invention, it should be understood that the
disclosed embodiments are susceptible of changes and modifications
without departing from the scope of the invention. Therefore, we do
not intend to be bound by the details shown and described herein
but intend to cover all such changes and modifications falling
within the ambit of the appended claims.
* * * * *