WO2004083916A1 - Optical routing device comprising hollow waveguides and mems reflective elements - Google Patents
Optical routing device comprising hollow waveguides and mems reflective elements Download PDFInfo
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- WO2004083916A1 WO2004083916A1 PCT/GB2004/001213 GB2004001213W WO2004083916A1 WO 2004083916 A1 WO2004083916 A1 WO 2004083916A1 GB 2004001213 W GB2004001213 W GB 2004001213W WO 2004083916 A1 WO2004083916 A1 WO 2004083916A1
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- 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
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- 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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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- 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
- G02B6/3596—With planar waveguide arrangement, i.e. in a substrate, regardless if actuating mechanism is outside the substrate
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- 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
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- 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
- G02B6/353—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being a shutter, baffle, beam dump or opaque element
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- 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
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- 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
- G02B6/356—Switching arrangements, i.e. number of input/output ports and interconnection types in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links
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- 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
- G02B6/3566—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details involving bending a beam, e.g. with cantilever
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- 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
- G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
- G02B6/3572—Magnetic force
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- 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
- G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
- G02B6/3576—Temperature or heat actuation
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- 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
- G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
- G02B6/3578—Piezoelectric force
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- 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
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- 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
- G02B6/3598—Switching means directly located between an optoelectronic element and waveguides, including direct displacement of either the element or the waveguide, e.g. optical pulse generation
Definitions
- This invention relates to optical routing devices for use in telecommunicatior-- ⁇ systems and the like, and in particular to an optical routing device incorporating am array of moveable reflective elements.
- Telecommunication and data networks are increasingly being implemented using optical fibre links.
- the optical signals carried by the fibres were converted to electrical signals and any signal routing functions performed in the electrical domain.
- all-optica_l switching devices offer the potential to reduce the cost and complexity associated with routing signals across optical fibres networks.
- EP0221288 An early example of an all-optical switch is described in EP0221288.
- the arrangement comprises a mirror that can be moved by an electromagnetic actuator to route an optical signal to either one of two outputs .
- An alternative and more complex optical switching system is described in GrB2193816.
- the system of GB2193816 comprises a housing block having multiple hollow core waveguides and control rods that carry mirrors which are inserted into trie block to provide a desiretd optical routing function.
- devices of this type are physically large and, Ln the case of EP0221288, require relatively power hungry actuators.
- Optical routing devices are also known in which micro-electro-mechanical syste_tn (MEMS) devices are used to provide a selective routing capability.
- MEMS micro-electro-mechanical syste_tn
- a MEMS based two dimensional matrix switch is described by Wood, R. I---., Madadevan, R and Hill, E in paper TU05 of the proceedings of the Optical Fitore Communications Conference, March 2002, Los Angeles, USA.
- the device comprises a two dimensional array of pop-up MEMS mirrors that are magneticaOy rotated into the "up” state and held there electrostatically.
- the arrangement allows, a free space input light beam to be selectively routed from a "through” channel to any one of a number of "cross” channel. In this manner, a two dimensional matrix switch is provided.
- a disadvantage of optical devices of the type described by Wood et. al. is the high level of optical loss that is associated with the inclusion of the free space region in which the MEMS mirrors are located.
- diffraction effects result in an increase of the beam diameter as it propagates along each free space path. This reduces the efficiency with which light is subsequently coupled into an output optical fibre.
- any angular misalignment of the MEMS minor will produce an lateral offset in the optical beam.
- Angular misalignment effects of this type are cumulative; in other words, the lateral offset is amplified when light is reflected from multiple misaligned, minors. This further decreases the coupling efficiency into an output optical fibre.
- the device of US2003/0035613 comprises upper and lower layers in which hollow core multi-mode optical waveguides are formed.
- the hollow core waveguides of the upper and lower layers are ananged to overlap and flexible metal levers are provided in the vicinity of the overlapping w veguide regions.
- the metal levers can be deformed to guide light out of a waveguide formed in, say, the lower layer to a waveguide of the upper layer. In this manner, an optical routing function is obtained.
- accurate alignment of the upper and lower layers and providing mechanically robust and reliable flexible levers makes the fabrication of such a device rather complex.
- an in-plane optical routing device comprises a semiconductor substrate having at least one optical input, a plurality of optical outputs and an anay of micro -electromechanical system (MEMS) moveable reflective elements, said anay of moveable reflective elements being configurable such that light can be selectively routed from any one optical input to any one of two or more of said plurality of optical outputs, characterised in that light selectively routed from any one optical input to any one of two or more of said plurality of optical outputs is guided within a hollow core waveguide.
- MEMS micro -electromechanical system
- a device of the present invention thus provides a so-called matrix switch in which light is selectively routed from at least one input to any one of two or more outputs using an anay of MEM-S moveable reflective elements.
- the various optical paths between the input(s) and outputs comprise hollow core optical waveguides and lie in a plane that is substantially parallel to the plane of the substrate; i.e. the device is an "in-plane" optical routing device.
- the optical routing device of the present invention may be a standalone co ponent, or may form part of a planar light circuit ⁇ PLC) of the type described in PCT patent application GB2O03/000331.
- a device of the present invention is advantageous over prior art matrix switch devices of the type described previously by Woods et. al. because guiding light to, and from, the MEMS moveable reflective elements within a hollow core waveguide reduces unwanted beam attenuation from free-space diffraction and angular misalignment effects.
- the reduced losses due to the guiding effect of the hollow core waveguide also enable the separation between reflective elements in the array, and the numerical order of the anay, to be ' increased.
- the device of the present invention is especially advantageous when used with small diameter bea s where diffraction effects in a free space device would be proportionally greater. It should also be remembered that an angular rmsa ⁇ g trxent enor.
- angular misalignment of a reflective element in a device of the present invention imparts a certain coupling loss depending on the amount of misalignment; any such misalignment error is not amplified by subsequent reflections.
- the device of the present invention is also significantly less complicated to fabricate and more mechanically robust than dual plane hollow core waveguide devi ces of the type described in US2OO3/0035613. It should also be noted that the device described in US2003/0035613 only supports multi-mode propagation and is thus inherently more lossy than a device of the present invention.
- the non-guided regions can be arranged to constitute o_nly a small proportion of the waveguide, the gaps may slightly increase the optical loss of the waveguide. However, this effect is negligible and even with such gaps the hollow core waveguides provide reduced losses compared with prior art free space propagation devices.
- hollow core optical waveguide structures when hollow core optical waveguide structures are produced, the hollow core is likely to fill with air. However, this should be seen in no way as limiting the scope of this invention.
- the hollow core may contain any fluid ⁇ jfor example a liquid or an inert gas such as nitrogen) or be a vacuum.
- the term hollow core simply means a core which is absent any solid material.
- the texms "light” and “optical” are used herein to refer to any electromagnetic radiation having a wavelength from the ultraviolet to the far infra-red.
- Semiconductor substrates such as Silicon are prefened because they can be etohed with good accuracy using micro-fabrication techniques such as deep reactive ion etching.
- the substrate may advantageously comprise a multiple layer wafer; for example silicon on germanium (SiGe), silicon on sapphire, silicon-on-ins ⁇ l ator (SOI) or silicon-on-glass.
- SiGe silicon on germanium
- SOI silicon-on-ins ⁇ l ator
- mi ro- fabrication techniques typically involve a lithography step to define a pattern, followed by an etch step to transform the pattern in to one or more layers on, ox in, the substrate material.
- the lithography step may comprise photolithography, x--ray or e-beam lithography.
- the etch step may be performed using ion beam millir-c-g, a chemical etch, a dry plasma etch or a deep dry etch (also termed deep silicon etch).
- Micro-fabrication techniques of this type are also compatible with various layer deposition techniques such as sputtering, CND, electro-less plating and electroplating.
- the semi-conductor substrate comprises a base portion and a lid portion which together define the hollow core waveguide. Such an arrangement is described in more detail in PCT patent application GB2003/000331 and provides a. convenient way to fabricate the device.
- MEMS moveable reflective element depends on the speed and amount of movement required.
- the reflective element may be formed as an integral part of a MEMS actuation device, or may be attached to the MEMS actuator.
- MEMS is taken to include micro-machined elements, micro-systems technology, micro-robotics and micro-engineering and the like.
- the MEMS moveable reflective elements may advantageously comprise an electro-thermal actuation mechanism (e.g. a bent beam anangement) to provide large throw (e.g. 5-10O ⁇ m full scale deflection) actuation.
- Alternative actuation mechanisms such as electromagnetic, electrostatic (e.g comb drive), bimorph or piezoelectric may also be used. More detail on MEMS device actuation technologies and the associated fabrication techniques can be found in "Fundamental of Microfabrication” by Marc Madou, published by CRC Press (Boca Raton) in 1997; ISBN 0-8493-9451-1.
- the MEMS moveable reflective elements comprise a reflective coating.
- the reflective coating may be provided by any material having suitable reflective properties at the wavelength of operation.
- a material having a refractive index less than the material forming the waveguide core typically air
- the reflective coating may conveniently be provided by a layer of metal such as gold, silver or copper.
- Metals will exhibit a suitably low refractive index over a wavelength range that is governed by the physical properties of the metal; standard text boolcs such as "the handbook of optical constants" by E. D. Palik, Academic Press, London, 1998, provide accurate data on the wavelength dependent refractive indices of various materials.
- gold has a refractive index less than that of air at wavelengths within the range of around 500nm to 2.2 ⁇ m; this encompasses wavelengths within the important telecommunications band of 1400nm to 1600nm.
- Copper exhibits a refractive index less than unity over the wavelength range of 560nm to 2200nm, whilst silver has similar refractive index properties over a wavelength range of 320nm to 2480nm.
- a layer of metal may be deposited using a variety of techniques known to those skilled in the art. These techniques include sputtering, evaporation, chemical vapour deposition (CND) and (electro or electro-less) plating. CVD and plating techniques allow the metal layers to be deposited without significant direction dependent thickness variations. Sputtering using a rotating sample and/or source would also provide even coverage. Plating techniques are especially advantageous as they permit batch (i.e. multi-substrate parallel) processing to be undertaken.
- adhesion layers and/or barrier diffusion layers could be deposited on the reflective element prior to depositing the layer of metal.
- a layer of chrome or titanium could be provided as an adhesion layer prior to the deposition of gold.
- a diffusion barrier layer such as platinum, may also be deposited on the adhesion layer prior to gold deposition.
- a combined adhesion and diffusion layer (such as titanium nitride, titanium tungsten alloy or an insulating layer) could be used.
- the reflective coating may also be provided by an all-dielectric, a semiconductor- dielectric or a metal-dielectric stack.
- the dielectric material may be deposited by CND or sputtering or reactive sputtering.
- a dielectric layer could be formed by chemical reaction with a deposited metal layer. For example, a layer of silver could be chemically reacted with a halide to produce a thin surface layer of silver halide.
- the reflective coating may be provided by an all-dielectric, a semiconductor-dielectric or a metal-dielectric, stack.
- the optical thickness of the dielectric layer(s) gives the required interference effects and thus determines the reflective properties of the coating.
- the reflective properties of the coating may also be dependent, to some extent, on the properties of the material on which it is located.
- the material from whicti the reflective element is formed may also form a base layer, and be a part of, any such multiple layer dielectric stack.
- the internal surface of the hollow core waveguide compris.es a reflective coating.
- the reflective coating applied to the internal surface of the hollow core waveguide may be a metal or a dielectric or a metal-dielectric stack of the type described above. Any coating applied to the internal surface of the hollow core waveguide may be the same as, or different to, any coating applied to the moveable reflective elements.
- At least one of the MEMS moveable reflective elements is a pop-up minor.
- an electro-magnetic pop-up minor of the type described by Wood et al could be used.
- at least one of the MEMS moveable reflective elements may advantageously comprise a shutter.
- the shutter may be formed integrally with, or attached to, an appropriate actuation mechanism.
- the shutter could be also formed as a "flip-up" structure which removes geometrical constraints on shutter edge shape. It should be noted that, as described in more detail below, the use of hollow core waveguides enables the MEMS moveable reflective elements to be fabricated with reduced alignment tolerances.
- each MEMS moveable reflective element is formed monolithically with the hollow core waveguides.
- the MEMS element is formed in the same process as the hollow core waveguide thereby providing a simple to produce a device without requiring additional processing or device assembly.
- MEMS moveable reflective elements could advantageously be formed in a separate process and hybrid integration techniques used to attach it to the substrate in which the hollow core waveguide is formed.
- the provision of hollow core optical waveguides to optically link: the MEMS moveable reflective elements will reduce the optical losses associated with a given angular misalignment of the reflective elements.
- hollow core optical waveguide could be used to reduce the required angular alignment accuracy of the MEMS moveable reflective elements whilst providing a device with a given optical efficiency.
- each moveable reflective device is moveable between a fully (»_r partly) inserted position in which it protrudes into the hollow core waveguide, and ⁇ L fully retracted position.
- the reflective device could be moveable between two different positions within the waveguide.
- the moveable reflective elements are advantageously ananged in a regular array.
- the anay may be regularly spaced, or may be any anangement that provides the desired routing effect.
- Linear (i.e. one dim-ensional) or two dimensional anays may be used.
- the anay comprises sixteen or more moveable reflectiv ⁇ e devices. It is also possible to stack a number of the in-plane devices and provide linking waveguides between each two dimensional anay in the stack. ,
- the plurality of optical outputs include at ieast one through output and at least one cross output.
- the MEMS moveable reflective elements can, in the inserted position, have a reflective surface angled -at approximately 45° to the "through" and "cross" hollow core waveguide channels. -In this way, the device can be ananged such that when, the moveable reflectrve elements are retracted light is routed from the at least one input to the at least one through output and when a minor is inserted light is routed from the input to tt e associated cross output.
- a two-dimensional cross switch can be fabricated. Such a cross-switch would have an optical attenuation lower than pri or art devices of the type described by Wood et al.
- At least one of said at least one optical input and plurality of optical outputs comprise a means for receiving an optical fibre.
- the means ffor receiving an optical fibre may comprise an alignment slot formed in the device that is ananged to clamp an optical fibre in place thereby allowing optical connection to the device.
- stepped optical fibre alignment slots may be provided to hold both the buffer layer and the cladding.
- the alignment of the core of a hollow core optical fibre with the hollow core waveguide of the device may also be achieved; for example by clamping the optical fibre cladding in a alignment slot.
- the use of hollow core optical fibres would be especially advantageous as the air core to air core connection would be free from any unwanted reflections.
- At least one of said optical input and/or said optical outputs may conveniently comprise an out of plane reflector element.
- a plurality of devices of the present invention may be ananged in a stack.
- the cross-section of the hollow core waveguide should be appropriate for the cross-section of the optical fibre core.
- leakage into the cladding means that the width of the mode carried by the fibre is actually greater than the core diameter; for example typically the lO ⁇ m solid core of a single mode glass fibre has a total 1/e 2 TEM 0 o field width of around 14 ⁇ m diameter.
- lenses e.g. ball or GRIN rod etc
- Fibre ends of solid core fibres may be anti- reflection coated.
- Lensed fibres may also be used which would negate the requirement for separate collimating means to coupled the light into the hollow core waveguides of the device.
- portions of the one or more hollow core optical waveguides have a substantially rectangular (which herein shall include square) cross-section.
- a square, or almost square, cross-section hollow core waveguide provides a waveguide in which the losses are substantially polarisatio ⁇ ri independent and is piefened when the polarisation state of the light is unknown or varying.
- Dimensioning the waveguide to have a depth greater than its width or vice versa increases polarisation dependent losses, but may be advantageous when the polarisation state of light propagating through the waveguide is known.
- waveguides are convenient, many alternative waveguide shapes could be employed. For example, circular, elliptical or v-shaped waveguides could be provided.
- the hollow core waveguides are dimensioned to support fundamental mode propagation.
- the present invention can provide accurate ali.gnm.ent of MEMS moveable reflective elements with respect to the associated hollow core optical waveguides and consequently efficient fundamental mode coupling between sections of hollow core optical waveguide c an be achieved.
- the hollow core waveguides may be dimensioned to support multi- mode propagation. If multi-mode hollow core wave guide structures are provided, adjacent moveable reflective elements can advantageously be spaced apart by the re- imaging distance of the hollow core waveguide.
- the re-imaging phenomena, and details concerning calculation of the re-ima-ging distance for a given waveguide, are described in more detail below.
- the re-imaging effect provides a replication of an input field a certain distance from the injection of the field into a multi-mode waveguide. Spacing the moveable reflective elements by the re-i naging distance of light propagating through the inter-connecting waveguide enables a re-imaging point to be located in the vicinity of the moveable reflective elements.
- the invention provides an optical routing device that comprises- at least one input connected via a plurality of optical paths to a plurality of outputs.
- the device has a plurality of reflective elements that can be moved to change the optical path through the device, and light is guided along each optical path in a hollow core waveguide.
- substrates comprising semiconductor materials are described above, similar devices could also be formed on a variety of alternative substrate.
- the substrate could advantageously be silicon oxide based; for example formed from quartz, silica or glass.
- Substrates could, also be embossed, or patterns could be lithographically defined in polymer layers. From a manufacturing perspective, it can be advantageous to use batch micro-fabrication techniques.
- Figure 1 shows a prior art matrix switch
- Figure 2 shows a matrix switch of the present invention
- Figure 3 shows a further matrix switch of the present invention that utilises the re-imagin effect
- Figure 4 provides an expanded view of a portion of the device shown in figure 3;
- Figure 5 illustrates the potential angular misalignment of reflective devices
- Figure 6 shows the effect of such angular misalignment on the coupling efficiency between two sections of hollow core waveguide
- Figure 7 illustrates the use of hollow core optical waveguides for intra-chip optical coupling
- Figure 8 shows a plan view of intra-chip optical coupling using a matrix switch
- Figure 9 shows a side view of the coupling scheme of figure 8.
- FIG. 1 a prior art matrix switch 2 shown.
- the matrix switch 2 comprises four input optical fibres 4a to 4d (collectively refened to as the input fibres 4), four output optical fibres 6a to 6d (collectively refened to as the output fibres 6) and four cross-connect output optical fibres 8a to 8d (collectively refened to as the cross-connect output fibres 8).
- Each of the inpu-t fibres 4, output fibres 6 and cross-connect output fibres 8 have an associateci collimating lens 10.
- a substrate 20 is provided that carries a four-by-four anay of MEMS pop-up minors 22a to 22p Ccollectively refened to as the MEMS anay 22>.
- Each minor in the MEMS anay 22 can be placed in a stowed configuration or an upright configuration by application of an appropriate control signal by an array control means (not shown).
- the input fibres 4, output fibres 6 and substrate 20 are ananged such that, when eac-h minor in the MEMS array 22 is in a stowed configuration, the light from input fibre 4a propagates as a collimated beam in free space over the substrate and is directly coupled into the output fibre 6a.
- the substrate is also ananged such that any of the minors 22a, 22e, 22i and 22m cam be inserted into the free space optical path that is defined between the input fibre 4- a and the output fibre 6a.
- the minors 22a, 22e, 22i and 22m are orientated such that when in the upright configuration, light is directed out of the optical path betwee- i the input fibre 4a and the output fibre 6a and towards the cross-connect output 8a, 8b, 8c or 8d as appropriate.
- the light from each of the input fibres 4 may pass to its conespondmg output fibre 6 or may be routed by the appropriate minor of the MEMS anay 22 to any one of the four cross-connect output fibres 8.
- a two dimensional matrix switch is thus formed.
- prior art devices of the type illustrated in figure 1 have several disadvantages arising from the free-space propagation of light between the input and output fibres.
- beam diffraction causes the beam diameter to increase as it propagates through the matrix which results in poorer coupling to output fibre.
- any inaccuracy in angular alignment of a MEMS minor causes a lateral offset at the output plane resulting in the poor coupling of light in to the relevant output fibre.
- the matrix switch 50 is designed to provide the same optical routing function as the prior art device described with reference to figure 1.
- the matrix switch 50 comprises a silicon substrate 52 having a number of rectangular cross-section channels 54.
- the attachment of a lid portion (not shown) to the substrate defines hollow core optical waveguides.
- Lenses 56 are provided to optically couple the hollow core waveguides of the substrate to input optical fibres 4, output optical fibres 6 and cross-connect output optical fibres 8.
- An anay of reflective MEMS components 58a-58p (collectively referred to as the MEMS anay 58) is also provided.
- the components of the MEMS anay 58 comprise reflective surfaces that may be inserted into the hollow core optical waveguides to provide redirection of light propagating down a particular waveguide channel.
- the MEMS components may comprise pop-up minors of the type described by Wood et al and described with reference to figure 1 above.
- the MEMS components may comprises reflective shutters and associated MEM-S actuation means to move the shutters into and out of the hollow core waveguides of the substrate as appropriate.
- a benefit of using such MEMS devices, which may be integrally formed with the hollow core waveguide, is the high degree of minor alignment that can be obtained by forming the MEMS device in the material sunounding the hollow core waveguides, h addition, the hollow core waveguides reduce diffraction effects and thereby increases the overall optical efficiency of the device.
- the device comprises a silicon substrate 52 having a number of rectangular cross-section channels 54 formed therein to define, in combination with an appropriate lid portion (not shown), multi-mode hollow core optical waveguides.
- An anay of reflective MEMS components 102a-102p (collectively refened to as the MEMS anay 102) is also provided.
- Input optical fibres 4, output optical fibres 6 and cross-connect output optical fibres 8 are ananged to implement the two-dimensional matrix switch routing function described above.
- the components of the MEMS anay 102 are located in a regular four-by-four grid anangement in which each row and column of components is separated by the distance "a".
- the ends of each input optical fibre 4, each output optical fibre 6 and each cross-connect output optical fibre 8 are also located a distance "a" from the associated component of the MEMS anay 102.
- the anangement of the matrix switch 100 is dimensioned to exploit the so-called "re-imaging" phenomena that is found with multi-mode waveguides.
- the length "a" is selected to be the re-imaging length (or a multiple thereof) of the hollow core waveguide such that, for a multi-mode waveguide of given cross-section dimensions, an image of the input beam profile is reproduced in the vicinity of the components in the MEMS array 102.
- multi-mode waveguides in particular those with a rectangular cross-section
- multi-mode waveguides can be designed to provide re-imaging of symmetric, anti-symmetric or asymmetric optical fields of a given wavelength by designing the length of the waveguide to have an appropriate relationship to its width and depth.
- the Gaussian input profile of a input beam is re-imaged (i.e. reproduced), after propagating a certain distance along a given waveguide.
- This effect also gives rise to beam replication; i.e. multiple images of the beam being formed at distances shorter than the re-imaging length.
- MMI multi-mode interference
- a symmetric field in a square sectioned waveguide This will have a re-imaging length that is given by the square of the waveguide width over the wavelength of the propagating radiation. Re-imaging of the symmetric field occurs at the re-imaging length and multiples of the re-imaging length.
- the re-imaging occurs at eight times the length required for symmetric field re-imaging, i.e. at 12.09 -mm for a 50.0 ⁇ m wide hollow waveguide.
- a minor image of the asymmetric field is also formed at half this length i.e. at 6.05 mm.
- the re-imaging lengths associated with the two waveguide cross-sectional dimensions are themselves different.
- any field can be re-imaged.
- a symmetric field can be re- imaged in a hollow rectangular waveguide by ananging that the re-imaging lengths associated with axes of width Wi and w 2 to be identical.
- the anangement shown in figures 3 and 4 has the advantage that collimating means (e.g. lenses) are not required in order to couple light between the hollow core waveguides and the associated optical fibres. Furthermore, placing each component of the MEMS anay 102 at a re-imaging distance further eases the acceptable angular alignment tolerances of the MEMS components. In addition ' , use of the xe-imaging effect also reduces diffraction losses where the waveguide has to be broken in order to facilitate the location of a moveable reflective element. R-eferring to figures 5 and 6, the effect of angular misalignment of the reflective components on the coupling efficiency between sections of hollow cor ⁇ waveguide is shown.
- collimating means e.g. lenses
- Figure 5 shows a silicon substrate 52 in which a first hollow waveguide 140 and a second hollow waveguide 142 are formed.
- a reflective element 144 is located in the waveguide and ananged to reflect light carried by the first hollow waveguide 140 into the second hollow waveguide 142.
- the reflective element 144 has a certain angular misalignment (30) determined by the device manufacturing tolerances.
- Figure 6 shows the power coupling efficiency of a fundamental (EH ⁇ ) mode from the first hollow waveguide 140 to the second hollow waveguide 142 as a function of angular misalignment ( ⁇ ) of a minor 144. It can be seen that the acceptable angular alignment tolerances for efficient coupling between sections of hollow core fibre are greatly relaxed compared to the angular alignment requirements for a matrix switch of the type described by Wood et al; see, in particular, figure 4 and the associated description in Wood et al where minor alignment accuracy better than 0.05° is considered necessary.
- anays including linear (i.e. one dimensional) anays could be used.
- the benefits of the invention are increased as the anay size (and hence path length between input and output fibres) is increased.
- the use of hollow core waveguide devices of the type described above thus permits high order optical switches to be provided. It would also be possible to stack a number of devices of the present invention so as to form a three dimensional matrix array; light being coupled from parallel planes in hollow core waveguides or in free space.
- FIG. 7 shows a silicon substrate 200 that comprises a plurality of channels defining hollow core optical xvaveguides 202.
- the hollow corre waveguides 202 of the substrate 200 are used to connect the twelve optical outputs of a vertical cavity surface emitting laser (VCSEL) 204 to twelve conesponding detector elements of an InGaAs detector anay 206.
- VCSEL vertical cavity surface emitting laser
- the hollow core optical waveguides may be dimensioned so that re-imaging of the input field produced by each NCSEL occurs at the detector element.
- a semiconductor substrate 210 that comprises hollow core optical waveguide channels 211 and a plurality of pop-up MEMS minors 212.
- This arrangement provides a matrix switch of the type described in more detail above.
- the matrix switch can be used to route light from each element of the NCSEL array 204 to a detector element of either a first detector array 206 or a second detector anay 208. In this manner, the optical interconnects between the various components of the chip can be readily re-configured.
- Figure 9 shows an exploded cross-sectional view of the device of figure 8 along line I-I. It can be seen that the VCSEL array 204 and the first detector anay 206 are integrally formed on a chip 218 using known fabrication techniques.
- the semiconductor substrate 210 is comb ned with a lid portion 216 which together define hollow core optical waveguides 211 in the plane of the substrate. Angled minors 214 are provided in the substrate 210, and hollow waveguide portions 220 are provided through the lid 216, to enable light to be coupled to/from the components on the substrate into the plane of the matrix switch. In this manner, re- configurable intrachip optical connections are provided.
- optical coupling anangements of this type may be used to optically connect two or more chips or to provide intra-chip opitcal connections between various components formed on a single chip.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Mechanical Light Control Or Optical Switches (AREA)
- Optical Integrated Circuits (AREA)
- Use Of Switch Circuits For Exchanges And Methods Of Control Of Multiplex Exchanges (AREA)
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002518070A CA2518070A1 (en) | 2003-03-22 | 2004-03-22 | Optical routing device comprising hollow waveguides and mems reflective elements |
EP04722315A EP1606658B1 (en) | 2003-03-22 | 2004-03-22 | Optical routing device comprising hollow waveguides and mems reflective elements |
JP2006505992A JP4478145B2 (en) | 2003-03-22 | 2004-03-22 | Optical path setting device including hollow waveguide and MEMS reflecting element |
US10/548,665 US20060215954A1 (en) | 2004-03-22 | 2004-03-22 | Optical routing device comprising hollow waveguides and mems reflective elements |
AT04722315T ATE550686T1 (en) | 2003-03-22 | 2004-03-22 | OPTICAL ROUTING DEVICE WITH HOLLOW WAVEGUIDES AND MEMS REFLECTION ELEMENTS |
US12/923,656 US8165433B2 (en) | 2003-03-22 | 2010-09-30 | Optical routing device comprising hollow waveguides and MEMS reflective elements |
Applications Claiming Priority (2)
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GBGB0306638.8A GB0306638D0 (en) | 2003-03-22 | 2003-03-22 | Optical routing device |
GB0306638.8 | 2003-03-22 |
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US10548665 A-371-Of-International | 2004-03-22 | ||
US12/923,656 Continuation US8165433B2 (en) | 2003-03-22 | 2010-09-30 | Optical routing device comprising hollow waveguides and MEMS reflective elements |
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WO2004083916A1 true WO2004083916A1 (en) | 2004-09-30 |
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PCT/GB2004/001213 WO2004083916A1 (en) | 2003-03-22 | 2004-03-22 | Optical routing device comprising hollow waveguides and mems reflective elements |
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EP (1) | EP1606658B1 (en) |
JP (1) | JP4478145B2 (en) |
CN (2) | CN100397120C (en) |
AT (1) | ATE550686T1 (en) |
CA (1) | CA2518070A1 (en) |
GB (1) | GB0306638D0 (en) |
WO (1) | WO2004083916A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009017862A1 (en) * | 2007-08-01 | 2009-02-05 | Hewlett-Packard Development Company, L.P. | Systems and method for routing optical signals |
US20120263414A1 (en) * | 2009-12-21 | 2012-10-18 | Michael Renne Ty Tan | Circuit switched optical interconnection fabric |
US20130272651A1 (en) * | 2012-04-11 | 2013-10-17 | Terrel Morris | Routing optical signals |
US8811778B2 (en) | 2007-08-01 | 2014-08-19 | Hewlett-Packard Development Company, L.P. | Systems and method for routing optical signals |
US9011020B2 (en) | 2010-01-06 | 2015-04-21 | Hewlett-Packard Development Company, L.P. | Optical interconnect |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2010210782A (en) * | 2009-03-09 | 2010-09-24 | Ricoh Co Ltd | Micromirror apparatus |
JP5183575B2 (en) * | 2009-06-10 | 2013-04-17 | 日本電信電話株式会社 | Method and apparatus for adjusting optical path length using magnetic field in hollow optical waveguide |
KR20140122709A (en) | 2012-01-31 | 2014-10-20 | 휴렛-팩커드 디벨롭먼트 컴퍼니, 엘.피. | Optical architectures, optical distribution matrices, and methods of manufacturing optical structures |
WO2013154553A1 (en) * | 2012-04-11 | 2013-10-17 | Hewlett-Packard Development Company, L.P. | Routing optical signals |
CN104216052A (en) * | 2013-05-29 | 2014-12-17 | 鸿富锦精密工业(深圳)有限公司 | Optical signal transmission device |
CN107678098B (en) * | 2016-08-01 | 2019-09-03 | 华为技术有限公司 | Photoswitch and optical switching system |
CN114815274B (en) * | 2022-04-28 | 2023-02-14 | 厦门大学 | Optical vortex generating system with locally controllable near field |
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JPS5387746A (en) * | 1977-01-13 | 1978-08-02 | Nec Corp | Optical path changer of hollow waveguide |
US6501869B1 (en) * | 2000-03-20 | 2002-12-31 | George Mason University | Optical switching system |
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US6212314B1 (en) * | 1998-07-08 | 2001-04-03 | Lucent Technologies | Integrated opto-mechanical apparatus |
CN1402070A (en) * | 2002-09-30 | 2003-03-12 | 华中科技大学 | Temp-non-sensitive array waveguide grating |
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- 2003-03-22 GB GBGB0306638.8A patent/GB0306638D0/en not_active Ceased
-
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- 2004-03-22 JP JP2006505992A patent/JP4478145B2/en not_active Expired - Fee Related
- 2004-03-22 WO PCT/GB2004/001213 patent/WO2004083916A1/en active Application Filing
- 2004-03-22 CA CA002518070A patent/CA2518070A1/en not_active Abandoned
- 2004-03-22 AT AT04722315T patent/ATE550686T1/en active
- 2004-03-22 EP EP04722315A patent/EP1606658B1/en not_active Expired - Lifetime
- 2004-03-22 CN CNB2004800078212A patent/CN100397120C/en not_active Expired - Fee Related
- 2004-03-22 CN CNA2008100952038A patent/CN101334503A/en active Pending
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JPS5387746A (en) * | 1977-01-13 | 1978-08-02 | Nec Corp | Optical path changer of hollow waveguide |
US6501869B1 (en) * | 2000-03-20 | 2002-12-31 | George Mason University | Optical switching system |
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009017862A1 (en) * | 2007-08-01 | 2009-02-05 | Hewlett-Packard Development Company, L.P. | Systems and method for routing optical signals |
US8811778B2 (en) | 2007-08-01 | 2014-08-19 | Hewlett-Packard Development Company, L.P. | Systems and method for routing optical signals |
US20120263414A1 (en) * | 2009-12-21 | 2012-10-18 | Michael Renne Ty Tan | Circuit switched optical interconnection fabric |
US8885991B2 (en) | 2009-12-21 | 2014-11-11 | Hewlett-Packard Development Company, L.P. | Circuit switched optical interconnection fabric |
US9011020B2 (en) | 2010-01-06 | 2015-04-21 | Hewlett-Packard Development Company, L.P. | Optical interconnect |
US20130272651A1 (en) * | 2012-04-11 | 2013-10-17 | Terrel Morris | Routing optical signals |
Also Published As
Publication number | Publication date |
---|---|
CN100397120C (en) | 2008-06-25 |
GB0306638D0 (en) | 2003-04-30 |
CA2518070A1 (en) | 2004-09-30 |
JP4478145B2 (en) | 2010-06-09 |
ATE550686T1 (en) | 2012-04-15 |
EP1606658B1 (en) | 2012-03-21 |
CN1764854A (en) | 2006-04-26 |
EP1606658A1 (en) | 2005-12-21 |
JP2006520925A (en) | 2006-09-14 |
CN101334503A (en) | 2008-12-31 |
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