Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
  • G02B6/3584—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
  • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
  • G02B6/3514—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element moving along a line so as to translate into and out of the beam path, i.e. across the beam path
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
  • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
  • G02B6/3518—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
  • G02B6/3546—NxM switch, i.e. a regular array of switches elements of matrix type constellation

Definitions

• the present invention relates to an optical switch utilizing a multi layer structure wafer for WDM (Wavelength Division Multiplex) optical communication system, and more particularly, to an optical switch utilizing a multi layer structure wafer comprised of a structural layer, a sacrificial layer and a supporting layer, the sacrificial layer being partially etched to release the structural layer-with a minimum area, and the supporting layer being etched to define a panel to support the waveguides, a mirror for reflecting transmission light between the waveguides, a mirror driving means.
• WDM Widelength Division Multiplex
• multiple channel signals are transmitted by light with several wavelengths in the WDM optical fiber communication.
• Single mode fibers supporting light signals with the wavelength of 1.3 or 1.55 urn are widely used for this optical fiber communication because of low transmission loss.
• the apparatus for implementing the WDM is called 'Wavelength division multiplexers' and functions as a kind of optical coupler, which make one optical fiber channel work multiple signal optical paths by the separation of the channel signals with respect to their wavelengths.
• wavelength division multiplexers For example, light signals with wavelengths of 1.3 ⁇ m and 1.31 ⁇ m can be transmitted through one optical fiber. Each of wavelength signals has the individual information and is transmitted independently through the fiber.
• the wavelength division multiplexer system uses an optical add/drop mutiplexer.
• the optical add/drop mutiplexer uses a MEMS (Micro Electro Mechanical Switch) type optical switch.
• MEMS Micro Electro Mechanical Switch
• the MEMS type optical switches blocking light signals or changing the light paths.
• Micromachined optical switch is big issue because its usual insertion losses, crosstalk, wavelength dependent losses, polarization dependent losses are lower than any other switching mechanism.
• Optical waveguide is a transmitting medium with the shape of cylindrical or rectangular bar in the optical switch.
• index matching oil is used to reduce the return loss at the end facets of waveguides, but its handling of the index matching oil for fiber aligning or packaging is difficult.
• the refractivity of optical waveguide is about 1.5.
• index matching oil is supplied between the input port and the output port so as to allow the space to have the same refractivity as the optical waveguide.
• the index matching oil may be vaporized or frozen. To avoid this phenomenon, the optical switch should be packaged.
• optical switch In addition, the optical and mechanical properties of the optical switch are different to a considerable degree.
• a first object of this invention is to provide an optical switch utilizing a multi layer structure wafer enabling optical communication between input and output ports without the usage of index matching liquid.
• a second object of this invention is to provide an optical switch utilizing multi layer structure wafer comprised of structural, sacrificial, and supporting layers to finely actuate the optical switch.
• an optical switch utilizing a multi layer structure wafer by comprising: optical waveguides each having an input port 11 and an output port 12 for optical signal transmission, the input port 11 and the output port 12 being configured in a beveled facet; a structural layer 100 provided with fixing parts for fixing the waveguides, a mirror 20 for changing an optical communication direction between the input port 11 and the output port 12, an actuator for driving the mirror; a sacrificial layer 200 arranged below the structural layer and etched to have a small area relative to the structural layer 100, for supporting the structural layer 100 apart therefrom; and a supporting layer arranged below the sacrificial layer, for supporting the sacrificial layer 200 and the structural layer 100.
• the fixing part 30 comprises a first fixed panel 31 face-contacted with the optical waveguide 10, for supporting the optical waveguide from a side portion of the optical waveguide 10, and a second fixed panel 32 line-contacted with the optical waveguide 10, for elastically supporting the optical waveguide 10 from the side portion of the optical waveguide.
• a lens 1100 is further disposed between the input port 11 and the output port 12.
• the structural layer 100 and the supporting layer 300 are of silicon, and the sacrificial layer 200 is of silicon oxide.
• the input port 11 and the output port 12 of the optical waveguide 10 have an end facet, which is coated with an antireflection film.
• Figure 1 represents a cross-sectional view of the wafer structure of the optical switch fabrication according to the present invention
• Figure 2 is a schematic view illustrating a light transmission principle between optical waveguides according to the present invention
• Figure 3 is a schematic view illustrating a first operation of the optical switch according to a first embodiment of the present invention
• Figure 4 is a schematic view illustrating a second operation of the optical switch according to a first embodiment of the present invention
• Figure 5 is a schematic view illustrating a first operation of the optical switch according to a second embodiment of the present invention.
• Figure 6 is a schematic view illustrating a second operation of the optical switch according to a second embodiment of the present invention
• Figure 7 represents the first concept images of the optical waveguide according to the present invention
• Figure 8 represents the second concept images of the optical waveguide according to the present invention.
• Figure 9 represents the third concept images of the optical waveguide according to the present invention.
• Figure 1 is a cross-sectional view of the wafer structure for the optical switch fabrication in accordance with the invention.
• the wafer is used to form a fixing part 30 for supporting a waveguide 10, a mirror 20 for shutting light or changing the direction of the light between waveguides, and a driving mean for driving the mirror 30 in the optical switch 1000.
• the uppermost layer of the wafer is a structural layer 100.
• a sacrificial layer is
• the wafer 200 is placed beneath the structural layer 100, and a supporting layer 300 of the lowermost layer is placed beneath the sacrificial layer 200.
• the wafer is composed of the structural layer 100, the sacrificial layer 200, and the supporting layer 300 along its height direction.
• the usual material of the structural layer 100 is silicon.
• the structural layer is usually etched by using
• the material of the supporting layer 300 is silicon.
• the supporting layer 300 acts as a base to support the structural layer 100 and the sacrificial layer 200 therebeneath.
• the sacrificial layer 200 is of silicon dioxide and is etched by using HF.
• the sacrificial layer 200 is etched in a small size relative to the size of each size between the structural layer 100 and the supporting layer 300 and non-etched portions of the sacrificial layer 200 functions to connect the other two layers 100, 300 mechanically.
• Figure 2 represents the schematic diagram of the principle of the light transmission between optical waveguides according to the present invention.
• the end faces of waveguides for input / output ports(11 ,12) are preferred to have a beveled angle.
• the beveled angle is about 3 - 20 degrees. Small part of light is reflected at the end facet while the other part is transmitted by refraction. The reflected light cannot return to the original waveguide 10 because its reflected angle is larger than the acceptance angle of the waveguide. Therefore, the retum loss can be reduced.
• the refracted light to the air is transmitted to the corresponding waveguide 10.
• Small part of the refracted light is reflected at the end facet of the corresponding waveguide 10 while the other part is propagated through the corresponding waveguide 10.
• the light reflected at the other side waveguide 10 is nearly not propagated along the one side waveguide through which the initial light is outputted, and is released to nearly not influence the reflection loss.
• Figure 3 is a schematic view illustrating a first operation of the optical switch according to a first embodiment of the present invention
• Figure 4 is a schematic view illustrating a second operation of the optical switch according to a first embodiment of the present invention.
• two pairs of beveled waveguides 10 and a mirror 20 for changing the path of light are provided as a preferred example of the 2x2 optical switch.
• Fixing parts 30 are equipped at both sides of each waveguide 10.
• Each of the fixing parts 0 is composed of a first fixing panel 31 for supporting the side of the waveguide and a second fixing panel 32 for supporting the other side of the waveguide.
• the first fixing panel 31 is face-contacted with the waveguide 10 to support the waveguide 10 at its side portion and the second fixing panel 32 is line- contacted with the waveguide 10 to elastically support the waveguide 10 at its side portion.
• the waveguides 10 are optically aligned in their position and direction using the first and second fixing panels 31 and 32 for easy alignment.
• the panels 31, 32 and the mirror 20 are fabricated using the multi layer structure wafer by the vertical etching of the structural layer.
• the sacrificial layer 200 is formed in a smaller size to function only to connect the structural layer 100 and the supporting layer 300 by the floating of the structural layer 100. Additionally, metal can be coated on the mirror 20 for higher reflectivity.
• Figure 3 and 4 represent plane views of the construction of the optical switch
• optical waveguides 10 are aligned to match light between optical waveguides 10. Two light signals from the two input ports 11 are propagated to their corresponding output ports 12 straightly. This is usually named as off state.
• figure 4 shows the on state done by operation of the mirror 20 to the crossing point of two light paths.
• the lights go the other output ports 12.
• the reflection angle of the mirror 20 is obtuse angle, over 90°, but may be changed in accordance with a beveled angle of the waveguide 10 and arrangement of mirror 20 and waveguide 10.
• the mirror 20 can be driven by the micromachined actuators (not shown in the figure) utilizing forces such as electrostatic, electromagnetic, thermal, piezoelectric, bi-metal, etc.
• the facets of the beveled waveguide can be directed toward the front surface of the rear surface, too. In those cases, lateral offset may be different depending on the refraction direction shown in Figure 2.
• Figure 5 is a schematic view illustrating a first operation of the optical switch according to a second embodiment of the present invention
• Figure 6 is a schematic view illustrating a second operation of the optical switch according to a second embodiment of the present invention.
• a 2x2 optical switch 1000 according to anther preferred example of the present invention is to expand the moving channels of the light signal, and includes four mirrors 20 and two pairs of waveguies 10.
• Figure 5 shows off state that lights from optical waveguides 10 are aligned to be propagated to the remaining two optical waveguides 10 using two mirrors 20. The lights from the two input ports 11 are propagated along two reflection paths.
• figure 6 shows the on state done by the operation of the mirrors
• the reflection angle of the mirror 20 is an acute angle, i.e., smaller than 90 degrees relatively, but can be different depending on the beveled angle of the waveguides 10 and the alignment between the mirror 20 and the waveguides 10.
• the mirror 20 can, be driven by micromachined actuators using electrostatic, electromagnetic, thermal, piezoelectric, bi-metal, etc.
• the optical waveguides 10 can be aligned at a right angle or different angles for the convenience of alignment of optical axis.
• the beveled angle of the waveguides 10 can be directed toward the front surface of the wafer or the rear surface, and the lateral offset can be different depending on the refraction direction shown in FIG. 2.
• Figure 7, 8, 9 represent the first, second, third concept images of the optical waveguide in this invention, respectively.
• the light emitted from the beveled optical waveguide diverges.
• the end portion of each of the input and output ports 11 and 12 of the waveguides 10 is coated by anti-reflection coating material such as Ti0 2 , thereby reducing the light reflection loss.
• the light emitted from the beveled optical waveguide can be collimated or focused by its rounded shape at the end facets of the input and output ports 11 and 12 can be made in a round shape like a convex lens for light transmission, thereby improving the aforementioned light divergence.
• a convex lens 1100 can be installed between the waveguides 10 shown in figure 7 to collimate or focus light emitted from the beveled optical waveguide.
• the inventive optical switch 1000 utilizing multi layer structure wafer without the usage of index matching liquid can be applied to 1x2 or 2x2 optical switches.
• the numbers of optical waveguides and mirror can be changed within the region that the micromachining technology supports.
• the reflection angle of the mirror 20 can be varied variously depending on the beveled angle of the waveguides 10 and the alignment degree between the mirror 20 and the waveguides 10, i.e., a relative moving position of the mirror 20 in addition to the aforementioned acute angle of obtuse angle.
• the structural layer 100 can be etched by using one selected from the group consisting of PMAH solution, KOH solution and EDP solution, in addition to the aforementioned SF 6 .
• the sacrificial layer 300 can be etched by using BOE solution which HF solution is diluted, in addition to the aforementioned HF solution.
• the characteristics of this invention provides the solution to make the optical switch utilizing multi layer structure wafer without the usage of index matching liquid with the problems of fiber alignment and packaging. Also, multi layer structure wafer composed of structural, sacrificial, and supporting layers support the optical switch by the simple fabrication process.

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Citations (5)

Family Cites Families (7)

• 2002
  • 2002-09-27 KR KR10-2002-0058954A patent/KR100492488B1/ko not_active IP Right Cessation
• 2003
  • 2003-09-25 WO PCT/KR2003/001963 patent/WO2004029683A1/en not_active Application Discontinuation
  • 2003-09-25 AU AU2003264969A patent/AU2003264969A1/en not_active Abandoned

Patent Citations (5)

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