Optical: systems and elements – Collimating of light beam
Reexamination Certificate
2001-03-21
2002-08-06
Mack, Ricky (Department: 2873)
Optical: systems and elements
Collimating of light beam
C359S627000, C359S290000
Reexamination Certificate
active
06429976
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates optical switches applicable to various devices for optical communication. In particular the invention relates to optical switches of the spatially optical coupled type using a plurality of tilt mirrors each of which has a reflective surface with an angle thereof being controllable.
(2) Related Art
For example, as conventional optical switches applied to various optical communication devices such as optical cross-connection devices, constructions which mechanically switch an optical fiber, or which use a waveguide device are generally known. However, conventional optical switches of this construction are limited to a scale of only tens of channels, and to realize large scale optical switches extending to thousands of channels as required for recent years, it is necessary to introduce new technology.
As one technology for realizing large-scale optical switches, the development of optical switches of the spatially optical coupled type which use micro-tilt mirror arrays manufactured for example by applying the technology for micro machining (MEMS: Micro Electric Mechanical System), is progressing. More specifically, there are the optical switches known for example by an article by D. T. Neilson et al., “Fully provisioned 112×112 micro-mechanical optical cross-connect with 35.8 Tb/s demonstrated capacity,” Optical Fiber Communications Conference (OFC 2000), Post deadline paper PD-12, March 2000, or by International Patent Publication WO 00/20899. Moreover, in relation to the micro tilt mirror by the MEMS, there is known the technology disclosed for example in the specification of U.S. Pat. No. 6,044,705.
The basic construction of optical switches using such conventional tilt mirrors, comprises for example, as shown in the perspective view of FIG.
13
and the plan view of
FIG. 14
, an input collimator array
51
A, an output collimator array
51
B and two MEMS tilt mirror arrays
52
A and
52
B. By switching an optical path by changing an angle of input light from the input collimator
51
A by the first tilt mirror array
52
A, and making the angle of beam return by the second tilt mirror array
52
B, the light for which the optical path is switched is incident on the output collimator array
51
B.
However, with an optical switch using the conventional tilt mirrors as described above, there has been a problem that high precision is required in mounting the input and output collimators
51
A and
51
B and the tilt mirror arrays
52
A and
52
B. As a technique for solving this problem, there is proposed a construction such as that shown in the perspective view of FIG.
15
and the plan view of
FIG. 16
where by turning back input light with a mirror
53
, and using a collimator array
51
and a tilt mirror array
52
with input sides and output sides formed integrally, respectively, a reduction in the members and adjustment parts is achieved.
However, in an optical switch constructed using a turn-back mirror
53
as shown in the aforementioned FIG.
15
and
FIG. 16
, because the input section and the output section of the tilt mirror array
52
are arranged on the same plane, then compared to the case of the construction shown in the aforementioned FIG.
13
and
FIG. 14
, for example when the swing angles of the input tilt mirrors are all set identically, the spatial propagation distance (the optical path length) of the beam in the switch is doubled. Therefore, there is a disadvantage that the optical switch increases in size. In order to reduce the optical path distance, for example, the swing angle of the input tilt mirror may be increased. However, there is a limit to a range of the controllable swing angle of the tilt mirror. Also with a tilt mirror having a large swing angle, since the constructional size becomes large, miniaturization of the overall optical switch is difficult.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the abovementioned points and has an object of providing an optical switch using tilt mirrors, in which easy mounting of optical components is possible by the simplification of construction, and in which a short spatial propagation distance for a light beam is realized.
In order to achieve the abovementioned object, the optical switch using tilt mirrors of the present invention comprises: a collimator array formed with an input section arranged with a plurality of input collimators and an output section arranged with a plurality of output collimators, the input section and the output section being aligned within the same plane; a tilt mirror array formed with an input section arranged with a plurality of input tilt mirrors each of which has a reflection surface with an angle thereof being controllable and an output section arranged with a plurality of output tilt mirrors each of which has a reflection surface with an angle thereof being controllable, the input section and the output section being aligned within the same plane; and a shift type turn-back mirror for shifting an optical path of incident light in a predetermined direction and turning back and outputting this light, wherein the light output from the respective input collimators of the collimator array, is reflected by the corresponding input tilt mirrors of the tilt mirror array so that the optical path is changed, and is then sent to the shift type turn-back mirror, and the light which has been shifted and turned back by the shift type turn-back mirror is reflected by the corresponding output tilt mirrors of the tilt mirror array and then respectively output from the respective output collimators of the collimator array.
With such a construction, after the propagation direction of the light reflected by the input section of the tilt mirror array has been shifted and turned back with the shift type turn-back mirror, the light is sent to the output section of the tilt mirror array. Hence, it is possible to realize a construction where the input and output sections of the collimator array and those of the tilt mirror array are integrated, respectively, without increasing the spatial propagation distance of the light inside the switch. As a result, it is possible to provide an optical switch using small size tilt mirrors with easy mounting for the optical components. Moreover, by reducing the number of optical components, it is also possible to improve stability against disturbances such as temperature fluctuations and vibrations.
Furthermore, for a specific construction of the abovementioned optical switch using tilt mirrors, the tilt mirror array is arranged so that a normal direction of a plane on which the respective reflection surfaces of the input tilt mirrors and the output tilt mirrors are arranged, and a propagation direction of the light output from the input section of the collimator array are not parallel. In particular, preferably the tilt mirror array is arranged so that an angle subtended by the normal direction and the propagation direction of the light from the collimator array is approximately 45°. By arranging in this manner, it is possible to minimize the distance between the input section and the output section of the tilt mirror array with respect to the swing angles of the respective tilt mirrors.
Further, with the optical switch using tilt mirrors as described above, the arrangement may be such that the direction in which the input section and the output section of the collimator array are aligned, the direction in which the input section and the output section of the tilt mirror array are aligned, and the shift direction of the optical path of the shift type turn-back mirror, are made parallel, respectively, with respect to a reference plane which contains the normal direction for the tilt mirror array and the propagation direction of the light output from the input section of the collimator array. Alternatively, the arrangement may be such that the respective directions are perpendicular to the reference plane. In this case, the spatial propagation dis
Akashi Tamotsu
Mori Kazuyuki
Tanaka Kazuhiro
Tochio Yuji
Yamamoto Tsuyoshi
Fujitsu Limited
Mack Ricky
Staas & Halsey , LLP
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