Free-space optical switch

Details Free-space optical switch Free-space optical switch

2001-09-18

2003-01-14

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

With optical coupler

Switch

C385S016000, C385S017000

Reexamination Certificate

active

06507683

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a free-space optical switch for switching an optical signal path in fields of optical communication, information processing, etc.
It is to be noted that in this specification, the term “micromirror” represents a micro-electro-mechanical system (MEMS) mirror.
2. Description of the Prior Art
FIG. 11
shows an arrangement of a free-space optical switch described at page 168 in a tutorial “Optical-Layer Networking: Opportunities for and Progress in Lightwave Micromachines” by L. Y. Lin et al. in proceedings of the 25th Optical Fiber Communication Conference (OFC 2000). In
FIG. 11
, a signal light ray incident from an input port array
11
is reflected at a desired angle by an input micromirror array
21
and is propagated to an output port array
12
through angular control of an output micromirror array. Namely, a signal light array
31
incident from a port
111
in the input port array
11
is initially reflected at a desired angle by a micromirror
211
in the input micromirror array
21
and is propagated to a desired port
121
in the output port array
12
through angular control of a micromirror
221
in the output micromirror array
22
.
Then, as a switching function of the optical switch, the output port
121
is switched to an output port
122
. To this end, the micromirror
211
of the input micromirror array
21
undergoes angular change so as to propagate to a micromirror
222
of the output micromirror array
22
the signal light ray
31
from the input port
111
and the micromirror
222
performs corresponding angular control of the signal light ray
31
so as to propagate the signal light ray
31
to the output port
122
such that the optical path is switched. In angular control of the micromirrors in switching of the optical path, when the optical path proceeds from the micromirror
211
at one diagonal end of one micromirror array
21
in the opposing micromirror arrays
21
and
22
to the micromirror
222
at the other diagonal end of the other micromirror array
22
, the micromirror
211
undergoes a maximum angular change.
Meanwhile,
FIG. 12
shows an arrangement of a free-space optical switch described at page 167 of the above mentioned tutorial. In
FIG. 12
, a fixed mirror
4
is arranged and the input port array
11
and the output port array
12
of
FIG. 11
are integrally formed into a port array
13
, while the input micromirror array
21
and the output micromirror array
22
of
FIG. 11
are integrally formed into a micromirror array
23
such that a function similar to that of
FIG. 11
is fulfilled. Also in the arrangement of
FIG. 12
, when the optical path proceeds from the micromirror
211
to a micromirror
223
which are, respectively, disposed at one diagonal end and the other diagonal end in the integral micromirror array
23
, the micromirror
211
undergoes a maximum angular change.
In the conventional optical switches of
FIGS. 11 and 12
, the micromirrors
211
,
221
,
222
and
223
should be subjected to angular control. However, the micromirror produced by micromachine technology has such a drawback that it is structurally difficult to cause a large angular change owing to difficulty in materializing a large scale in a vertical direction of the micromirror in comparison with that in a horizontal direction of the micromirror in thin film deposition technology, etching technology or the like.
Meanwhile, the micromirror is disadvantageous in that since it is difficult to produce a large driving force such as electrostatic force, magnetic field of the like in the vertical direction of the micromirror in terms of its driving principle, it is difficult to effect a large angular change.
SUMMARY OF THE INVENTION
Accordingly, an essential object of the present invention is to provide, with a view to eliminating the above mentioned drawbacks of prior art free-space optical switches, a free-space optical switch which is highly reliable by minimizing amount of angular change of an input micromirror or is more compact by minimizing an overall optical path length in case the amount of angular change of the input micromirror is identical on the contrary.
In order to accomplish this object of the present invention, a free-space optical switch according to the present invention comprises: a micro-electro-mechanical system (MEMS) mirror array for switching an optical transmission path, in which an input MEMS mirror array and an output MEMS mirror array confronting an input fiber port array and an output fiber port array, respectively are provided, wherein the input MEMS mirror array and the output MEMS mirror array are formed integrally with each other; wherein instead of equally dividing the MEMS mirror array into the input MEMS mirror array and the output MEMS mirror array simply by a single boundary line, one or both of the input MEMS mirror array and the output MEMS mirror array are further divided so as to be arranged.


REFERENCES:
patent: 6253001 (2001-06-01), Hoen
Line et al., “Optical-Layer Networking: Opportunities For And Progress In Lightwave Micromachines”, AT&T, Labs-Research, Redbank, New Jersey, 2000, pp. 150-195.

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