Optical: systems and elements – Collimating of light beam
Reexamination Certificate
2003-01-15
2004-08-03
Ben, Loha (Department: 2873)
Optical: systems and elements
Collimating of light beam
C359S619000, C359S621000, C385S018000, C385S031000, C385S033000, C385S039000, C385S047000, C385S074000, C385S089000
Reexamination Certificate
active
06771426
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to an input-output optical system of spatially optical coupled type which is suitable for use in effecting optical coupling between an input and an output by sending and receiving light beam in a space without use of an optical fiber connection, as well as to an optical switch of spatially optical coupled type having the input-output optical system.
(2) Description of the Related Art
In association with recent speedup of an optical signal flowing through a trunk cable system, there arises a necessity for even an optical switch, such as an optical cross-connect device, to handle a high-speed optical signal having a speed exceeding 10 Gbps (gigabits per second). As a result of an increase in the number of wavelengths to be multiplexed (currently up to thousands of channels), a required scale of optical switching is becoming massive.
Against such a background, development of an optical switch of spatially optical coupled type using a micro tilt mirror array to which a micro electromechanical system (MEMS) is applied has recently been pursued as a technique for rendering the scale of an optical switch larger. There are available optical switches such as that described in, e.g., “Fully-provisioned 112×112 micro-mechanical optical cross-connect with 35.8T b/s demonstrated capacity” by D. T. Neilson et al., Optical Fiber Communications Conference (OFC 2000), Post-deadline paper PD-12, March 2000,” or that described in Published International Publication WO 00/20899. In relation to a micro tilt mirror using a MEMS, a technique proposed in, e.g., U.S. Pat. No. 6,044,705, has already been known.
In an optical switch of spatially optical coupled type using a mirror, an input-output optical system becomes important, wherein signal light having propagated through an (input) optical fiber is output into a space as a collimated beam, and the beam is subjected to processing, such as switching, through use of a micro tilt mirror. Then, the beam again enters an (output) optical fiber. For this reason, a technique for easily manufacturing a highly-accurate, stable input-output optical system is sought for commercializing a large-scale optical switch.
A conventional input-output optical system will now be described.
FIG. 17
schematically shows an example of three-dimensional mount structure of a conventional input-output optical system. The input-output optical system shown in
FIG. 17
has a predetermined substrate
100
; a pair of optical systems (optical transmission units)
200
mounted thereon with bolts or the like; i.e., one optical system for input and the other optical system for output (hereinafter, an input optical system
200
is sometimes denoted as an input optical system
200
a
, and an output optical system
200
is sometimes denoted as an output optical system
200
b
), each optical system being constituted by combination of a collimator lens
201
and a fiber block
202
; an attachment member
300
a
on which the optical system
200
a
is to be mounted with bolts or the like; and an attachment member
300
b
on which the optical system
200
b
is to be mounted with bolts or the like. Here, illustration of an optical switch mechanism is omitted from FIG.
17
. Here, the fiber block
202
is for housing a plurality of optical fibers in the form of an array.
In the input-output optical system having such a construction, in order to accurately align a light exist surface of the input optical system
200
a
to a light incidence surface of the output optical system
200
b
(i.e., to accurately align optical axes of the respective optical systems
200
with each other), an optical axis is aligned in a three-dimensional direction by means of individually adjusting mount positions and orientations (angles) of the optical systems
200
and those of the attachment members
300
a
,
300
b.
However, such a three-dimensional optical axis alignment requires alignment of six axes; that is, alignment of a longitudinal axis, alignment of a lateral axis, alignment of an optical axis, alignment of rotation around an optical axis, alignment of rotation around the longitudinal axis, and alignment of rotation around the lateral axis. Hence, an extremely large number of processes are required for assembling the input-output optical system. As described in, e.g., Japanese Patent Application Laid-Open No. 220405/1996, repetition of the following steps is required; namely, a step of fastening the attachment members
300
a
,
300
b
and the respective optical systems
200
with bolts, a step of detecting optical axes, and a step of temporarily loosening the bolts if no match exists between the optical axes and adjusting the mount positions and angles of the optical systems
200
and those of the attachment members
300
a
,
300
b
. Hence, adjustment of optical axes requires consumption of much time. For this reason, an improvement in manufacturing yield is not expected, resulting in high product costs.
Proposed in the aforesaid patent publication
220405
/
1996
is an optical transmission unit
2
such as that shown in
FIGS. 18A and 18B
.
FIG. 18A
is a front view of the optical transmission unit
2
, and
FIG. 18B
is a transverse plan view of the optical transmission unit
2
.
In the optical transmission unit
2
, the amount of fastening of respective fastening screws
19
is adjusted individually through use of the three mount screws
19
and three springs (compression coil springs)
20
, thereby adjusting the angle of an outgoing beam (i.e., a beam into which the light output from a light-emitting element
5
is collimated by a collimator lens
3
).
In
FIGS. 18A and 18B
, reference numeral
4
designates a polarization beam splitter;
5
designates a light-emitting element;
6
designates a light-receiving element;
7
designates an optical axis;
11
designates a main body frame;
9
designates a front frame of the main body frame
11
;
9
a
designates an attachment hole formed in the front frame
9
;
9
b
designates screw holes;
14
designates a cylindrical section inserted into the attachment hole
9
a
so that the angle of the cylindrical section can be displaced;
16
designates a flange;
15
designates an attachment hole by which it is formed in the flange
16
perimeter at intervals of 120 degrees, and the screw
19
is inserted;
17
designates a cylinder;
18
designates an element unit formed by attaching the polarization beam splitter
4
, the light-emitting element
5
, and the light-receiving element
6
to the cylinder
17
; and
19
a
designates the head of a mount screw
19
.
Under the foregoing known technique, adjustment of an optical axis becomes easier than that shown in FIG.
17
. However, use of the springs
20
results in unstable fastening of the unit, which may cause an unexpected offset in an optical axis. Further, an offset may arise in an optical axis for reasons of long-term variations in elastic moduli of the springs
20
. Therefore, the known technique is insufficient in terms of accuracy and reliability (stability) of adjustment of an optical axis.
SUMMARY OF THE INVENTION
The invention has been conceived in light of such a drawback and aims at providing an input-output optical system of spatially optical coupled type and an optical switch, which enable highly accurate, highly stable, and easy alignment of an optical axis.
To achieve the object, the invention provides an input-output optical system of spatially optical coupled type comprising:
a substrate;
an input optical system which is provided on the substrate and which has an input fiber block and an input lens array block, wherein a plurality of input optical fibers are connected to the input fiber block in an array, and a plurality of collimating lenses which collimate light input from the optical fibers connected to the input fiber block and output collimated light are arranged in the input lens array block in an array;
an output optical system which is provided on the substrate and which has an output lens array block an
Akashi Tamotsu
Takeuchi Shinichi
Yamamoto Tsuyoshi
Ben Loha
Fujitsu Limited
Staas & Halsey , LLP
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