Optical switch and method of producing the same

Details Optical switch and method of producing the same Optical switch and method of producing the same

2001-04-18

2003-02-11

Feild, Lynn D. (Department: 2839)

Optical waveguides

With optical coupler

Switch

C385S013000, C385S140000, C250S227220

Reexamination Certificate

active

06519381

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch used for switching of an optical path in an optical communication equipment.
2. Description of the Background Art
A conventional optical switch
100
will be described with reference to FIG.
13
. This optical switch
100
is one shown in TuM
1
(J. E. Fouquet, “Compact optical cross-connect switch based on total internal reflection in a fluid-containing planar lightwave circuit”) at OFC 2000 (Optical Fiber communication Conference, Mar. 7, 2000). Optical switch
100
is formed by a silica planar optical circuit substrate
51
, where a two-dimensional optical circuit is formed by providing a rectangular optical waveguide having a slightly high refractive index within silica planar optical circuit substrate
51
. Generally, silica planar optical circuit substrate
51
having a refractive index of about 1.5 is employed, while optical waveguide
2
portion is made of a material with a refractive index that is higher by about 1%. The portion of optical waveguide
2
is in general also referred to as a “core.” A trench
52
is formed such that it traverses a position that partially overlaps with a crosspoint of optical waveguides
2
, and trench
52
is filled with refractive index-matching oil
56
. Refractive index-matching oil
56
is oil having a refractive index equal to that of optical waveguide
2
.
An operation of optical switch
100
will be described. In optical switch
100
, a bubble generating mechanism, not shown, is provided which can generate a bubble
53
and also make bubble
53
disappear in the liquid of refractive index-matching oil
56
at a crosspoint of optical waveguides
2
. For the bubble generating mechanism, the same mechanism as that used for a head of a bubble-jet printer may be employed.
When bubble
53
is generated at a crosspoint, a light that enters into the crosspoint is totally reflected by a surface of bubble
53
, while when no bubble
53
exists, the light travels in a straight line because optical waveguide
2
and refractive index-matching oil
56
have an equal refractive index. By utilizing this property, an optical path can be switched between two states of reflection/straight travel by generation/disappearance of bubble
53
.
In optical switch
100
formed in the above-described manner, accuracy of an etching process requires a width of trench
52
to be at least about 15 &mgr;m. In addition, there is a problem of optical loss of at least 0.07 dB per crosspoint. On the other hand, optical loss L [dB] of optical switch
100
as a whole is given by the following formula:
L=
2
C
+(
m−
1)
T
+(
n−
1)
T+R,
where
m is a number of input ports,
n is a number of output ports,
C is a loss [in dB] upon entry of a light into an optical switch from an optical fiber and during travel through an optical waveguide to an active area which is a crosspoint,
T is a loss [in dB] upon traversing one trench and during transmission through a section of a short optical waveguide between two crosspoints, and
R is a loss [in dB] for reflection upon a sidewall of an empty trench and transmission through a section of a short optical waveguide between two crosspoints.
For instance, when configuring a large-scale 1000×1000 optical switch, specific numerical values substituted into the above formula give L=2×0.25+(1000−1)×0.07+(1000−1)×0.07+2.1=142.46 dB. Thus, even with an ideally produced optical switch, optical loss of 142.46 dB would occur. It is necessary to limit optical loss L to 10 dB or below in order for an optical switch to function without degrading signal quality. In this manner, there is a disadvantage in that a larger scale than about 32×32 is difficult to form with such type of configuration when optical loss is considered.
Moreover, silica planar optical circuit substrate
51
is produced by a device similar to that which produces a semiconductor so that a large optical switch would disadvantageously become extremely expensive to produce. Further, since bubble
53
is produced and utilized each time it is needed in refractive index-matching oil
56
, there is a problem of optical switching malfunction occurring when the generated bubble
53
is too small or when the bubble is generated out of position. Furthermore, depending on the condition of refractive index-matching oil
56
, local absorption of light would take place with a small globule of refractive index-matching oil
56
such that an optical path in its periphery would disadvantageously burn due to the energy of a signal light.
It is, therefore, an object of the present invention to provide an optical switch that facilitates production, that can be formed in large scale with little optical loss, and that does not involve switching malfunction or burning as described above.
SUMMARY OF THE INVENTION
To achieve the above object, an optical switch according to the present invention includes a plate material basically made of polymer and a drive element. The plate material has optical waveguides that extend linearly within the plate material and a cut provided such that it traverses the optical waveguides, and the drive element selects a path of light by reducing and increasing the gap of the cut.
By adopting the above-described arrangement, the distance of a gap can be switched between being as narrow as ¼ the wavelength of a signal light or narrower and being wider than ¼ the wavelength by reducing and increasing the gap of a cut so that switching between connection/reflection of the signal light can be performed. With this type, accuracy with which a gap is controlled may be low so that an optical switch can be formed in a simple manner.
According to the present invention, the cut preferably is cut in from one side of the plate material and is a path selective slit that does not reach the other side of the plate material. By adopting this arrangement, misalignment of optical waveguides can be prevented since a portion of the plate material remains connected.
According to the present invention, the optical waveguides cross one another inside the plate material, and the cut is arranged such that it transverses a crosspoint of the optical waveguides. By adopting this arrangement, switching between connection/reflection at a crosspoint can be effected so that a direction of a signal light can be selected as either of the optical paths at the crosspoint.
According to the present invention, the optical waveguides preferably cross one another inside the plate material, and the cut is arranged such that it transverses a plurality of crosspoints of the optical guides, and the path selective slit extends linearly such that it traverses a plurality of the crosspoints, and plate material has a stress release slit that crosses the path selective slit between one of the crosspoints and another of the crosspoints.
According to the present invention, the drive element preferably is a pressuring element for pressing the cut from one side, and a gap of the cut is reduced to a distance that is ¼ a wavelength of light propagating a signal or less by pressing effected by a pressuring element. By adopting this arrangement, optical waveguides can be connected by pressing effected by a pressuring element so that a signal light can be transmitted as it is.
According to the present invention, the drive element preferably is a pressuring element for pressing the cut from one side, and a gap of the cut is increased to a distance that is greater than ¼ a wavelength of light propagating a signal by pressing effected by a pressuring element. By adopting this arrangement, optical waveguides can be blocked by pressing effected by a pressuring element so that a signal light cannot be transmitted and is totally reflected. With this type, the natural form of optical waveguides with substantially no local deformation can be maintained upon transmission so th

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