The invention relates to wavelength selective switches and integrated optical waveguides.
Wavelength selective switches typically have one or more input ports and one or more output ports and are capable of routing each of a number of wavelengths from any input port to a selected output port. In some wavelength selective switches, the output ports are not wavelength specific and any wavelength can be routed to any output. These output ports are referred to as “colourless”. In other wavelength selective switches, the output ports are wavelength specific. These output ports are referred to as “coloured”. In these devices, only one particular wavelength can be routed to each output port.
Conventionally, in order to have both colourless and coloured output ports, two separate switching devices were required.
According to one broad aspect, the invention provides an apparatus comprising: an input port; at least one colourless output port, each colourless output port outputting a respective signal containing a combination of all wavelengths switched to that colourless output port; a plurality of coloured output ports each for outputting a respective predetermined wavelength; a bulk optical element associated with the plurality of coloured output ports; a wavelength selective arrangement adapted to selectively switch each of a plurality of wavelengths of an input signal to a respective one of: a) a selected colourless output port; b) the bulk optical element which then routes the wavelength to the coloured output port of the plurality of coloured output ports that outputs that wavelength.
In some embodiments, the bulk optical element comprises a secondary routing lens.
In some embodiments, the at least one colourless output port comprises a plurality of colourless output ports.
According to another broad aspect, the invention provides an apparatus comprising: an input port; a plurality of colourless output ports, each colourless output port outputting a respective signal containing a combination of all wavelengths switched to that colourless output port; a plurality of coloured output ports each for outputting a respective predetermined wavelength; an optical element associated with the plurality of coloured output ports; a wavelength selective arrangement adapted to selectively switch each of a plurality of wavelengths of an input signal to a respective one of: a) a selected colourless output port; b) the optical element which then routes the wavelength to the coloured output port of the plurality of coloured output ports that outputs that wavelength.
In some embodiments, the optical element is a waveguide dispersive element.
In some embodiments, the apparatus comprises a respective first output dispersive element associated with each of the colourless output ports, and an input dispersive element associated with the input port having substantially similar dispersion characteristics to the first dispersive output elements, and wherein the optical element comprises a second output dispersive element having a different dispersive characteristic from the input dispersive element such that a net dispersion exists after light is dispersed by the input dispersive element and the second output dispersive element.
In some embodiments, each dispersive element is a waveguide dispersive element.
According to another broad aspect, the invention provides an integrated optical waveguide device comprising: a plurality of arrayed waveguides each having a first dispersion; for each of the plurality of arrayed waveguides having a first dispersion, a respective first integrated optics coupling element adapted to couple light between the waveguide and a respective port; at least one arrayed waveguide having a second dispersion differing from said first dispersion; for the arrayed waveguide having the second dispersion, a second integrated optics coupling element adapted to couple light between the arrayed waveguide and a plurality of ports; wherein the first dispersion and the second dispersion differ enough such that after passing through one of the plurality of dispersive elements and the second dispersive element and the second integrated optics coupling element, optical wavelengths have a physical separation such that each wavelength is coupled to a respective one of the plurality of ports.
In some embodiments, each first integrated coupling optics comprises a respective substantially non-dispersive waveguide coupled to a slab waveguide.
In some embodiments, the second integrated coupling optics comprises a plurality of substantially non-dispersive waveguides coupled to a slab waveguide.
According to another broad aspect, the invention provides an apparatus comprising: a plurality of optical ports including at least one input optical port for receiving at least one wavelength channel and at least one colourless output optical port; at least one set of coloured optical ports; for each input optical port, a respective dispersive element optically connected to the optical port; at least one dispersive element optically connected to the at least one colourless output optical port; a bulk optical element having optical power; a plurality of reflective routing elements; wherein for each wavelength channel: the dispersive element of the input port and the bulk optical element disperses wavelengths of the wavelength channel towards a respective one of said plurality of routing elements, and the respective one of said plurality of routing elements directs the wavelengths of the wavelength channel via the bulk optical element to a selected colourless output port of said at least one colourless output port via the respective dispersive element of the selected colourless output port or to a selected set of coloured output ports, the selected colourless output port or set of coloured output ports being determined by the respective routing element; whereby wavelengths routed to a given colourless output port are re-combined into a single output signal for the port, and each wavelength routed to a given set of coloured output ports appears at a wavelength specific port of the set.
In some embodiments, said at least one colourless output port comprises at least two colourless output ports.
In some embodiments, the dispersive elements are transmissive and are between the optical ports and the bulk optical element having power.
In some embodiments, the apparatus comprises a respective dispersive element for each colourless output port.
In some embodiments, the apparatus comprises a single dispersive element for the colourless output ports.
In some embodiments, each dispersive element comprises an array of waveguides having a predetermined first optical path length difference spread across the array.
In some embodiments, the apparatus further comprises a dispersive element comprising an array of waveguides having a predetermined second optical path length difference spread across the array associated with the set of coloured output ports, the first and second optical path length difference being different.
In some embodiments, the dispersive elements are collectively integrated onto a single waveguide device.
In some embodiments, the apparatus further comprises micro-optics coupling elements adapted to couple light from each port to/from the respective dispersive element.
In some embodiments, the apparatus further comprises integrated optical coupling elements adapted to couple light from each port to/from the respective dispersive element.
In some embodiments, each dispersive element comprises a transmissive diffraction grating.
In some embodiments, the dispersive elements and the routing elements are placed substantially at focal planes of the bulk optical element having optical power.
In some embodiments, the dispersive elements are integrated on a waveguide substrate, and the bulk optical element having power comprises a main cylindrical lens element adapted to focus light in a first plane in the plane of the waveguide substrate, the apparatus further comprising a transverse cylindrical lens adapted to substantially collimate light in a second plane perpendicular to the first plane.
In some embodiments, the main cylindrical lens has a focal length such that the dispersive elements are in a focal plane of the lens on a first side of the lens, and the routing elements are in a focal plane of the lens on a second side of the lens.
In some embodiments, the dispersive elements are selected from a group comprising: echelle grating, echellon gratings, prisms, and arrayed waveguides.
In some embodiments, each routing element is a tiltable micro-mirror.
In some embodiments, the apparatus further comprises: an athermal mount for the routing elements adapted to shift the routing elements to compensate for changes in dispersive characteristics of the dispersive element for the input port as a function of temperature.
In some embodiments, the dispersive elements comprise non-transmissive diffraction gratings, and a secondary lens is used to route light to the coloured ports.
According to another broad aspect, the invention provides an apparatus comprising: a plurality of optical ports including an input optical port for receiving at least one wavelength channel and at least two colourless output optical ports and at least a set of coloured output optical ports; for the input optical port and each colourless optical port, a respective dispersive element optically connected to the respective input optical port; a plurality of transmissive routing elements; a first bulk optical element having optical power; and a second bulk optical element having optical power; wherein for each wavelength channel: the dispersive element of the input port and the first bulk optical element direct any light of the wavelength channel towards a respective one of said plurality of transmissive routing elements, and an appropriate setting of the respective one of said plurality of transmissive routing elements directs the light of said wavelength channel via the second bulk optical element to a respective selected colourless output port of said at least two colourless output ports via the respective dispersive element or to a selected set of coloured ports.
In some embodiments, each routing element is one of a liquid crystal beam steering element, an acousto-optic beam deflector, part of a solid state phase array, a controllable hologram, and a periodically polled Lithium Niobate beam deflector.
In some embodiments, the apparatus comprises a secondary lens associated with each set of coloured ports that routes each wavelength to a wavelength specific port.
In some embodiments, the apparatus comprises a dispersive element associated with each set of coloured ports that has a different dispersion characteristic from the other dispersive elements such that a net dispersion remains after being dispersed by a combination of one of the other dispersive elements and one of the dispersive elements associated with a set of coloured ports.
According to another broad aspect, the invention provides an apparatus comprising: a stacked plurality of rows of optical ports, the ports comprising an input optical port for receiving at least one wavelength channel and at least two output optical ports; for each optical port, a respective dispersive element optically connected to the optical port; a bulk optical element having optical power; a plurality of routing elements; wherein for each wavelength channel: the dispersive element of the input port and the bulk optical element disperse any light of the wavelength channel towards a respective one of the plurality of routing elements, and the respective one of the plurality of routing elements directs the light of said wavelength channel via the bulk optical element to a respective selected output port via the respective dispersive element, the selected output port being determined by the respective routing element; at least one set of coloured optical ports wherein light of each wavelength can also be routed by the routing elements to a selected set of coloured optical ports, and each wavelength so routed appears at a wavelength specific port of the selected set.
According to another broad aspect, the invention provides an apparatus comprising: a stacked plurality of rows of optical ports, the ports comprising an input optical port for receiving at least one wavelength channel and at least two output optical ports; for each row of optical ports, a respective dispersive element optically connected to the row of optical ports; a bulk optical element having optical power; a plurality of routing elements; wherein for each wavelength channel: the dispersive element of the input port and the bulk optical element disperses any light of the wavelength channel towards a respective one of the plurality of routing elements, and the respective one of the plurality of routing elements directs the light of said wavelength channel via the bulk optical element to a respective selected output port via the respective dispersive element of the row of optical ports to which the selected output port belongs, the selected output port being determined by the respective routing element; at least one set of coloured optical ports wherein light of each wavelength can also be routed by the routing elements to a selected set of coloured optical ports, and each wavelength so routed appears at a wavelength specific port of the selected set.
According to another broad aspect, the invention provides an arrangement comprising: at least one input port, at least one input dispersive element associated with the at least one input port; at least one colourless output port, at least one output dispersive element being associated with the at least one colourless output port; at least one set of coloured output ports; at least one bulk optical element; for each of a set of wavelength channels, a respective switching element adapted to redirect the wavelength channel; wherein the dispersive elements, the at least one bulk optical element and the switching elements are arranged to: demultiplex wavelength channels received at the at least one input port; redirect each wavelength channel towards one of a selected colourless output port or a selected set of coloured output ports; for each colourless output port, remultiplex any wavelength channels routed towards the colourless output port; for each set of coloured output ports, output wavelength channels individually without remultiplexing.
According to another broad aspect, the invention provides a method comprising: using an input dispersive element, demultiplexing a multi-wavelength input signal into a plurality of wavelength channels; using a combination of switching elements and at least one bulk optical element, routing each of the plurality of wavelength channels to: a selected one of a plurality of colourless output ports via a dispersive element associated with the selected colourless output port; or a selected set of at least one set of coloured output ports; wherein for each colourless output port, any wavelengths routed to the colourless output port are combined to produce a colourless output; wherein for each set of coloured output ports, any wavelengths routed to the set of coloured output ports are output on wavelength channel specific output ports of the set.
Preferred embodiments of the invention will now be described with reference to the attached drawings in which:
Referring now to
In some embodiments, the arrangement of
Also, in the example of
The arrangement of
Referring now to
In operation, a multi-wavelength signal arrives at the input port 50 and is dispersed at the incoming dispersive element 52. Routing lens 54 routes each wavelength to a respective beam steering element of the beam steering array 56. The beam steering elements of the array 56 steer each wavelength through main lens 58. Each wavelength can be steered so as to be dispersed by one of the dispersive elements array 60 so as to be output by a selected one of the multiplexed output ports 61. Additionally, each wavelength can be steered so as to be routed by the secondary routing lens 62 to a wavelength specific demultiplexed output port 64. It can be seen that any wavelength in the input signal can be routed to any one of the multiplexed output ports 61. Also, any wavelength in the input signal can be routed to a pre-determined one of the demultiplexed output ports 64. In other words, a given wavelength can only ever appear at a particular one of the demultiplexed output ports 64. In this sense, the demultiplexed output ports 64 are “coloured”. The multiplexed outputs 61 are colourless.
The design of
For the embodiments of
The schematics of
Also, in the illustrated example, there are two multiplexed output ports 61, and three demultiplexed output ports 64. This is for the purpose of illustration only. Any appropriate number of multiplexed output ports 61 and any appropriate number of demultiplexed output ports 64 can be implemented. Furthermore, in some embodiments, there may be multiple secondary routing lenses 62 each having a respective set of demultiplexed output ports. An example of this is shown in
In the event the wavelengths produced at a given demultiplexed output are too closely spaced, some embodiments may employ a waveguide concentrator to provide proper spacing such that the wavelengths at each output port can be separately processed.
Advantageously, with the embodiments of
Referring now to
The output of the routing lens 134 passes through free-space to a main lens 136 which routes light from the input port 143 to a diffraction grating 183 forming part of an array of diffraction gratings 137. The array of diffraction gratings includes a diffraction grating for the input port, and a diffraction grating for each of one or more colourless output ports. In the illustrated example, there are four diffraction gratings in the array 137, three of which are for three colourless output ports 141. The array of diffraction gratings reflects the incoming light of each port according to wavelength. There is an array of switching elements 138 shown to consist of tiltable mirrors 138A, 138B and 138C, although likely there would be more mirrors than shown. More generally, there is a respective switching element for each wavelength channel to be switched. It is noted that the switching elements 138 are not in the same horizontal plane as the routing lens 134. This can be most clearly seen in the side view 130 SIDE. Each switching element performs a switching of light of a given wavelength from one input port to another optical port by tilting of the mirror. Also shown is a secondary routing lens 139 that has an associated set of demultiplexed or coloured output ports 140.
The operation of
In the illustrated example, beam 180 represents an input multi-wavelength signal received at input port 143. This is demultiplexed by dispersive element 183 to produce beams 182,184. Beam 182 travels through main lens 136, and is redirected by switching element 138A back through the main lens 136 to the set of coloured output ports 140 where it is output on a wavelength channel specific output port. Beam 184 travels through main lens 136, and is redirected by switching element 138C back through the main lens 136 to dispersive element 185 from where the beam is directed back through the main lens 136 to a output port 161 of the colourless output ports 141.
The examples of
One such two dimensional embodiment is similar to that of
Referring now to
The output of the routing lens 1402 passes through free-space to a main lens 1406 which routes light from the input port 1410 to a diffraction grating 1414 forming part of an array of diffraction gratings 1408. In the illustrated example, the array of diffraction gratings includes a respective diffraction grating for each row of ports in the two dimensional array of ports. In the illustrated example, there is a single set of coloured ports 1411 having associated secondary routing lens 1416. Thus, there are four diffraction gratings in the array 1408, three of which are for three rows of multiplexed output ports 1412. The array of diffraction gratings reflect the incoming light of each port according to wavelength. There is an array of switching elements 1404 shown to consist of tiltable mirrors 1404A, 1404B and 1404C, although likely there would be more mirrors than shown. The switching elements 1404 tilt in two dimensions. There would be a respective switching element for each wavelength channel. It is noted that the switching elements 1404 are not in the same horizontal plane as the routing lens 1402. This can be most clearly seen in the side view 1450 SIDE. Each switching element 1404 performs a switching of light of a given wavelength from one input port to another optical port by tilting of the mirror.
The operation of
In the illustrated example, beam 1420 represents an input multi-wavelength signal received at input port 1410. This is demultiplexed by dispersive element 1414 to produce beams 1422,1424. Beam 1424 travels through main lens 1406, and is redirected by switching element 1404A back through the main lens 1406 to the set of coloured output ports 1411 where it is output on a wavelength channel specific output port. Beam 1422 travels through main lens 1406, and is redirected by switching element 1404C back through the main lens 1406 to dispersive element 1418 from where the beam is directed back through the main lens 1406 to a particular colourless output port 1400 of the colourless output ports 1412.
In the illustrated example, there is a single set of coloured output ports 1411 and as such, a single secondary routing lens 1416. More generally, there may be multiple sets of coloured output ports. For the particular example of
Furthermore, while in the illustrated example, there is a respective diffraction grating for each row of ports, in another implementation there can be a respective diffraction grating per port, or a mix of diffraction gratings per port and diffraction gratings per row of ports.
A two dimensional embodiment can also be realized using waveguide dispersive elements. In that case, a row of dispersive elements can be implemented together on a waveguide device. A stacked arrangement of such devices provides a dispersive element per port in a 2-D array. One or more sets of coloured ports are provided, either by providing a dispersive element having different dispersion characteristics (as described in detail below with reference to
The above-described embodiments have employed either prisms or diffraction gratings as the dispersive elements. It is noted that any appropriate diffraction grating type might be employed. For example reflective, transmissive, echelle, echellon, or grisms, to name a few examples. Array waveguides and echelle waveguide gratings might be employed. More generally, any dispersive element that can achieve the desired wavelength dependent function may be employed by embodiments of the invention.
The described embodiments have featured MEMS mirror arrays to perform the switching of wavelengths. More generally, any appropriate switching elements may be used. For example, a tiltable micro-mirror, liquid crystal beams steering elements (phase array), accouto-optic beam deflectors, solid-state phase array, controllable holograms, periodically polled Lithium Niobate beam deflectors.
With the embodiment of
In operation, the dispersive element 312 associated with the input port 301 disperses all the wavelength channels received at the input port to the appropriate wavelength specific switching element in the array 240 via the collimating and focussing lenses 242,244. The switching elements switch each wavelength to a selected one of dispersive elements 312 for colourless output ports or to dispersive element 324 for coloured output ports. The dispersive elements 312 associated with the colourless output ports 302,303,304 re-multiplex wavelengths back to the associated colourless output port. This complete re-multiplexing occurs because of the fact that the dispersive elements for these colourless output ports are substantially identical to the dispersive elements for the input port. On the other hand, the dispersive element 324 associated with the coloured output port 305 has some amount of dispersion different from that of the other dispersive elements such that there is a net remaining dispersion after a wavelength is coupled back through the dispersive element 324 and integrated coupling optics 322. This means that the wavelengths at the output of device 322 are still separated by some small amount. Waveguide concentrator 320 separates the individual wavelengths into individual waveguides that are connected through to the coloured output ports 305.
The difference in the dispersion of the dispersive element for the colourless ports and the dispersive element for the coloured ports needs to be great enough such that it is possible to resolve individual channels for coloured outputs 305. The physical implementation of device 300 shown in the arrangement of
In the example implementation of
In one example, the order of the input dispersive elements and the dispersive elements for the colourless output ports is 33, whereas the order is 20 for the dispersive element for the coloured output ports. This is simply an example and of course any appropriate numbers can be used.
In a preferred embodiment, an athermal mount 241 is provided for the array of switching elements 240. This athermal mount moves the array of switching elements up and down as a function of temperature to compensate for changes in the dispersive characteristics of the dispersive element of the input port as a function of temperature.
The examples described have been specific to one input port and multiple multiplexed output ports and a single set of demultiplexed output ports. More generally, any number of ports of each type can be provided. Furthermore, a two dimensional array of ports can be provided in combination with one or more sets of demultiplexed output ports while preferably a MEMS mirror array is used for the switching elements, any appropriate switching element technology can be employed.
The examples described feature a single input port and multiple output ports. It is to be understood that any of the embodiments described can be operated in reverse such that the single input port is an output port, and the output ports are input ports.
Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
This application claims the benefit of prior U.S. Provisional Application Ser. No. 60/617,042 filed Oct. 12, 2004.
Number | Date | Country | |
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60617042 | Oct 2004 | US |