Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-10-31
2004-11-23
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S017000, C385S039000
Reexamination Certificate
active
06823099
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No.
2001-11731
, filed Mar. 7, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical bench, and more particularly, to an optical bench with improved structure, in which an optical path is shortened and tolerance is high for misalignment of optical elements.
2. Description of the Related Art
Recently, with an increase in an amount of data transmitted through an optical communications network, data transfer methods for an optical communication system are changing to wavelength division multiplexing (WDM) transfer methods. As such WDM systems need a connection between networks and an optical crossing connector, i.e., an optical bench, which is considered an essential element of the WDM systems.
In a conventional optical bench, as shown in
FIG. 1
, a plurality of micro-mirrors
40
are arranged in a matrix on a substrate
10
. The substrate
10
includes a plurality of input optical fibers
20
, each transferring an optical signal to the micro-mirrors
40
, and a plurality of output optical fibers
50
, each receiving and transmitting an optical signal reflected from the micro-mirror
40
. A plurality of input and output optical elements
30
and
60
for condensing and/or diverging an incident beam are arranged between the micro-mirrors
40
and the input and output optical fibers
20
and
50
.
As shown in
FIG. 2
, the input and output optical fibers
20
and
50
are placed in parallel first V-grooves
25
arranged with a predetermined separation gap therebetween, and the input and output optical elements
30
and
60
are placed in second V-grooves
35
connected to the first V-grooves
25
. The input and output optical fibers
20
and
50
are aligned with the input and output optical elements
30
and
60
, respectively, along a line. The input optical fiber
20
and the input optical element
30
are aligned in one optical axis with the micro-mirrors
40
and the output optical fiber
50
and the output optical element
60
are aligned in another optical axis with the micro-mirrors
40
.
For the optical bench having the configuration described above, a light beam emitted from a light source (not shown) enters one of the input optical fibers
20
and a corresponding input optical element
30
. The light beam is then reflected by a predetermined micro-mirror
40
. The light beam reflected by the micro-mirror
40
is output through one of the output optical elements
60
and a corresponding output optical fiber
50
.
An optical path of an incident beam can be changed toward an intended output channel by positioning the micro-mirrors
40
flat or upright on the substrate
10
. In particular, when the micro-mirrors
40
are positioned upright on the substrate
10
, the incident beam is reflected by the micro-mirrors
40
towards the intended output channel. When the micro-mirrors
40
are positioned flat on the substrate
10
, the incident beam goes straight, passing over the micro-mirrors
40
without being reflected.
When transferring the optical signal to the intended channel by changing the optical path, as described above, a minimum optical path is formed when an input optical signal received from, for example, an input channel ch_
1
, through the input optical fiber
20
and the input optical element
30
, reaches the micro-mirror
40
nearest to the input optical element
30
through an optical path S′, and is reflected by the micro-mirror
40
. The optical signal is output through the optical path S′, an output optical element
60
a
, an output optical fiber
50
a
, and an output channel ch_(N+1). In this case, the minimum optical path is formed as 2S′.
Meanwhile, a maximum optical path is formed when the optical signal received from an input channel ch_N through an input optical fiber
20
′ and an input optical element
30
′ reaches a micro-mirror
40
′ farthest from the input optical element
30
′ through an optical path L′, and is reflected by the micro-mirror
40
′ and enters an output optical channel ch_(N+M) through an optical path L′. Here, M is the number of output channels, and N is the number of input channels. Supposing M is equal to N, a maximum optical path 2L′ can be expressed as formula (1), using the unit optical path S′ and a channel pitch P′ between each input and output optical element
30
(
60
):
2
L′=
2(
S
′+(
N−
1)
P
′) (1)
The channel pitch P′ is greater than a diameter D of each optical element
30
and
60
because the input and output optical elements
30
and
60
typically do not perfectly fit into the second V-grooves
35
for the structural characteristic of the V-shaped grooves. Thus, the greater the diameter of the optical elements
30
and
60
, the greater the channel pitch P′ and the greater the maximum optical path 2L′.
FIG. 3
shows the maximum optical path 2L′ for each N×N channel structure when the input and output optical elements
30
and
60
have a diameter (D) of 0.3 mm and 1 mm, respectively, and the unit optical path S′ is equal to 1 mm. For this maximum optical path calculation, the channel pitch P′ is determined to be 66% greater than the diameter (D) of optical element.
In
FIG. 3
, it is apparent that the length of the maximum optical path 2L′ markedly increases with an increased number N of channels. For example, for a 128×128 channel structure, when the input and output optical elements
30
and
60
have a diameter (D) of 1 mm, the optical signal should travel a distance 400 times greater than the diameter (D) of the input and output optical elements
30
and
60
. As the optical path becomes longer, optical path alignment becomes difficult. Thus, to maintain optical efficiency, an error in reflection angle of the micro-mirror, and an alignment error between the optical elements and optical fibers or between the optical elements and micro-mirrors should be precisely controlled to be small. As a result, manufacturing cost increases due to an increase in assembly expense.
SUMMARY OF THE INVENTION
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To solve the above-described problems, it is an object of the present invention to provide an optical bench with an improved structure in which optical fibers and optical elements are arranged in a staggered fashion to reduce a maximum optical path and tolerance for misalignment of the optical fibers or micro-mirrors becomes great.
To achieve the above and other objects of the present invention, there is provided an optical bench including: a substrate; input and output optical fibers arranged on the substrate with a predetermined separation gap therebetween, wherein far ends of the input and output optical fibers form a zigzag pattern to guide input and output beams; input and output optical elements arranged at the far end of each input and output optical fiber, respectively, condensing and/or diverging the input and output beams; and micro-mirrors receiving the input beam from the input optical elements and reflecting the received input beam toward predetermined channels.
The optical bench satisfies a relation of P≦D, where P is a channel pitch and D is a diameter of the input and output optical elements.
The input optical fibers and the input optical elements, or the output optical fibers and the output optical elements are arranged on different planes.
The input and output optical fibers and the input and output optical elements are arranged as multiple layers and the arrangement for each multiple layer alternates.
To achieve the above and other objects of the present invention, an
Choi Hyung
Kim Jin-hwan
Lee John D.
Song Sarah
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