Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-11-14
2003-12-02
Mack, Ricky (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S291000
Reexamination Certificate
active
06657771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch for outputting to one of a plurality of output ports an optical signal that is input to one of a plurality of input ports.
2. Description of the Related Art
Some conventional optical switches are disclosed in the following references:
(1) Proceedings of 3rd International Conference on Micro-Opto-Electro-Mechanical Systems (MOEMS)'99, Paper 26, Aug. 29, 1999,
(2) U.S. Pat. No. 5,923,480 issued Jul. 13, 1999,
(3) Japanese Patent Application Kokai No. 2000-10029, and
(4) Optical Fiber Communication (OFC) 2000, Treaties, Lecture PD20, March 2000.
The optical switch described in JP 2000-10029 is shown in FIGS.
44
(A) and (B) as an example of the conventional optical switches.
In FIG.
44
(A), the optical switch
4400
comprises a plurality of optical deflectors
4402
a
and
4402
b
and a mirror
4404
. The mirror
4404
is fixed in place in the optical switch
4400
. The optical deflectors
4402
are arranged on a substrate
4406
. An optical input/output port is provided for each of the optical deflectors
4402
. An end of each of optical fibers
4408
a
and
448
b
is inserted into the optical I/O port and fixed in the optical deflector
4402
.
In operation, the optical switch
4400
makes simultaneous input and output of light beams at each of the light I/O ports. A light beam leaving from the optical fiber
4408
b
is input to the optical deflector
4402
b
and deflected therein. Then, the deflected beam is reflected by the mirror
4404
into the optical deflector
4402
a
, wherein it is guided into the optical fiber
4408
a
and output from the optical I/O port.
In FIG.
44
(B), the optical deflector
4402
comprises the optical fiber
4408
inserted through the I/O port, a collimating lens
4410
, a fixed mirror
4412
, and a movable mirror
4414
.
A light beam from the I/O port leaves from the end of the optical fiber
4408
that is housed in the optical deflector
4402
. This light beam is focused or condensed by the collimating lens
4410
and reflected or deflected by the fixed mirror
4412
into the movable mirror
4414
at which it is reflected at a given deflection angle. The movable mirror
4414
has two rotation axes that are perpendicular to the incident direction of a light beam so as to be movable on two axes. The rotation of the movable mirror
4414
may be adjusted by an ordinary technique. Thus, the movable mirror
4414
is able to reflect the light beam to the mirror
4404
at a given deflection angle. The mirror
4404
then reflects the light beam toward the optical deflector
4402
a.
The light beam put into the light deflector
4402
a
travels in the direction opposite to that of FIG.
44
(B) and is deflected by the movable mirror
4414
. Then, it is reflected by the fixed mirror
4412
, condensed by the collimating lens
4410
, and output from the I/O port via the optical fiber
4408
a
. The deflection angle is adjusted at the movable mirror
4414
to input the light beam into the optical fiber
4408
a.
As has been described above, this optical switch is composed of one stage of optical deflectors using a movable mirror or lens to control the direction of a light beam into the predetermined I/O port. This optical switch employs 3-D wiring or interconnection so that it is easy to increase the number of ports.
However, the conventional optical switch requires very high precisions with which the light beam is deflected by a single deflector. Consequently, it has the following disadvantage.
The diameter of optical fibers for usual optical communication systems is approximately eight microns. If a light beam is input with a positional error of about one micron, a loss of one dB or more is generated, presenting a practical problem. The distance between the output ports required for mounting is a few 100 microns or more so that even a piece of two-channel equipment requires a precision of about 0.1% in deflection angle. If the equipment has tens of channels or more, the required precision is in the order of 10-4. The 100-channel equipment using movable mirrors requires a precision of about 1% in deflection angle. The equipment of 1000 channels or more requires a precision of 0.3%.
In order to solve the problem, it has been proposed to superimpose a position detecting signal on the light beam to detect the deflection angle and feedback the detected angle to the deflection angle control unit. This unit, however, is unable to make high speed switching because of the limited speed of electrical process. Also, it is well known that an angle detection mechanism is incorporated in the deflection mirror for feedback control, but this method is unable to provide high precision.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an optical switch that requires lower precision for each optical deflector than ever before.
It is another object of the invention to provide an optical switch that is able to increase the number of channels and provide high switching speed.
According to the first embodiment of the invention there is provided an optical switch which includes an input switching element having a plurality of light input ports and an output switching element having a plurality of light output ports so as to output from one of the light output ports an optical signal that is input to one of the light input ports. The input switching element has a plurality of input optical deflector sets. Each set consists of a plurality of optical deflectors arranged in an incident direction of optical signals at each of the light input ports. The output switching element having a plurality of output optical deflector sets. Each set consists of a plurality of optical deflectors arranged in an emergent direction of optical signals at each of the light output ports.
With the optical switch according to the first embodiment, a light beam leaving from the optical fiber is input to the optical deflector and deflected by the at least two optical deflectors toward the predetermined light output port so that the precision for the deflection angle is distributed to the respective optical deflectors in the input optical deflector set. Thus, the precision required for each optical deflector is lowered.
According to the second embodiment of the invention there is provided an optical switch, which includes a plurality of light input ports and a plurality of light output ports so as to output from one of the output ports an optical signal that is input to one of the light input ports, comprises a plurality of input optical deflectors provided one for each of the light input ports; a plurality of output optical deflectors provided one for each of the light output ports; a plurality of input optical fibers connected one to each of the light input ports; a plurality of output optical fibers connected one to each of the light output ports; a plurality of optical systems provided one for each of the light input or output ports to increase an incident or emergent angle of each of the input or output optical fibers.
With the optical switch according to the second embodiment, the increased deflection angle makes it possible to reduce the distance between the lens and the lens focal plane while maintaining the required beam width so that the number of channels is increased while the required precision is maintained.
According to the third embodiment of the invention there is provided an optical switch, which includes a plurality of light input ports and a plurality of light output ports so as to output from one of the output ports an optical signal that is input to one of the light input ports, comprises a plurality of input optical deflectors provided one for each of the light input ports; a plurality of output optical deflectors provided one for each of the light output ports; a plurality of input optical fibers connected one to each of the light input ports; a plurality of output optical fibers connected one to each of the light output ports; and a plurality of
Kanesaka & Takeuchi
Mack Ricky
Oki Electric Industry Co. Ltd.
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