The present invention is generally directed to optical transmission networks, and more particularly to systems that permit flexible configuration of optical components in the field.
Passive optical networks are becoming prevalent in part because service providers want to deliver high bandwidth communication capabilities to customers. Passive optical networks are a desirable choice for delivering high-speed communication data because they may not employ active electronic devices, such as amplifiers and repeaters, between a central office and a subscriber termination. The absence of active electronic devices may decrease network complexity and/or cost and may increase network reliability.
The portion of the network 100 that is closest to central office 101 is generally referred to as the F1 region, where F1 is the “feeder fiber” from the central office 101. The portion of the network 100 closest to the end users 105 can be referred to as an F2 portion of network 100. The network 100 includes a plurality of break-out locations 102 at which branch cables are separated out from the main cable lines. Branch cables are often connected to drop terminals 104 that include connector interfaces for facilitating coupling of the fibers of the branch cables to a plurality of different subscriber locations 105.
An FDH 103 receives signals from the central office 101 via an input fiber. The incoming signal may be split at the FDH 103, using one or more optical splitters (e.g., 1×8 splitters, 1×16 splitters, or 1×32 splitters) to generate different user signals that are directed to the individual end users 105. In typical applications, an optical splitter is provided prepackaged in an optical splitter module housing and provided with a splitter output in pigtails that extend from the module. The optical splitter module provides protective packaging for the optical splitter components in the housing and thus provides for easy handling for otherwise fragile splitter components. This modular approach allows optical splitter modules to be added incrementally to FDHs 103 as required.
The number of end users may change, however, for example through the addition of new customers to the network or by customers dropping out of the network, and so occasions arise where the splitter in the FDH 103 may need to be replaced. In the case where more customers are added to the network, a splitter may need to be replaced by one having more outputs, for example a 1×16 splitter may need replacing by a 1×32 splitter. In other situations, for example where the number of customers drops, it may be useful to replace a splitter with one having fewer outputs. The replacement of a splitter at an FDH 103 requires that a technician travel to the FDH 103 to physically swap out the splitter. This can be costly and time-consuming. Also, a technician visit may be necessary when taking other actions, such as switching over to more OLTs when the number of customers increases, or when switching users between different service levels, such as different bitrates or video channels.
Furthermore, the splitters that are conventionally used in optical networks are passive devices whose configuration cannot be changed, which can lead to difficulties in monitoring the performance of the optical network. For example, one way of tracking down the cause of a signal loss at one or more end users is to use optical time-domain reflectometry (OTDR), which involves transmitting a pulsed optical signal along the fiber. Breaks, cracks or other issues with the fiber can result in a portion of the optical pulse being reflected to the source of optical pulses. The arrival times of the reflected pulses can be recorded and the time-of-flight measurement can be correlated with the position in the fiber where the reflection occurred. If there is a problem with transmission of signals to a particular end user, a technician has to set up the OTDR equipment downstream of the splitter output in the FDH 103 in order to isolate the end user's fiber from other fibers. This requires that the technician travels to the FDH 103 and physically disconnects the end user's fiber from the splitter in order to initiate the OTDR measurements. Again, this can be costly and time-consuming.
Therefore, there is a need for remote access to the FDH for changing the configuration of the splitter to add or drop fibers to end users, or to reconfigure the optical network to allow monitoring of one or more end users' fibers.
One embodiment of the invention is directed to an optical circuit that has a first input waveguide, at least a first output waveguide and an optical path between the first input waveguide and the at least a first output waveguide. A first totally internally reflecting (TIR) waveguide switch, such as a TIR electro-wetting on dielectric (EWOD) switch, lies on the optical path between the first input waveguide and the at least a first output waveguide. A wavelength selective filter is disposed on the optical path between the first input waveguide and the at least one output waveguide, the wavelength selective filter being transmissive for light in a first wavelength range and reflective for light in a second wavelength range.
Another embodiment of the invention is directed to an optical circuit that includes a first wavelength pass/drop unit comprising an input coupled to a first TIR optical switch, a first output from the first TIR optical switch is coupled to a first wavelength selective filter, and an output from the wavelength selective filter comprises a first output of the first wavelength pass/drop unit. A second output from the first TIR optical switch is coupled as a first input to a second TIR optical switch, a second output from the first wavelength selective filter is coupled as a second input to the second TIR optical switch, and an output from the second TIR optical switch comprises a second output from the first wavelength pass/drop unit. A second wavelength pass/drop unit comprises an input coupled to a third TIR optical switch, a first output from the third TIR optical switch coupling to a second wavelength selective filter, and an output from the second wavelength selective filter comprises a first output of the second wavelength pass/drop unit output. A second output from the third TIR optical switch is coupled as a first input to a fourth TIR optical switch, a second output from the second wavelength selective filter is coupled as a second input to the fourth TIR optical switch, and an output from the fourth TIR optical switch comprises a second output of the second wavelength pass/drop unit. The second output of the first wavelength pass/drop unit is coupled as the input to the third TIR optical switch of the second wavelength pass/drop unit.
Another embodiment of the invention is directed to an optical circuit that has a first wavelength pass/drop unit comprising an input coupled to a first TIR optical switch, a first output from the first TIR optical switch is coupled to a first wavelength selective filter, a second output from the first TIR optical switch is coupled as a first input to a second TIR optical switch, an output from the first wavelength selective filter is coupled as a second input to the second TIR optical switch, and an output from the second TIR optical switch comprises an output from the first wavelength pass/drop unit coupled to a first end user. The optical circuit also has a second wavelength pass/drop unit that includes an input coupled to a third TIR optical switch, a first output from the third TIR optical switch coupled to a second wavelength selective filter, a second output from the third TIR optical switch coupled as a first input to a fourth TIR optical switch, an output from the second wavelength selective filter coupled as a second input to the fourth TIR optical switch, and an output from the fourth TIR optical switch comprising an output of the second wavelength pass/drop unit coupled to a second end user. The first and second wavelength pass/drop units receive respective optical signals from an optical splitter, the respective optical signals each comprising an optical signal in a first wavelength band and an optical signal in a second wavelength band. When the first wavelength pass/drop unit is in a first state, the output from the first wavelength pass/drop unit coupled to the first end user carries an optical signal in the first wavelength band only and when the first wavelength pass/drop unit is in a second state, the output from the first wavelength pass/drop unit coupled to the first end user carries optical signals in both the first and second wavelength bands.
Another embodiment of the invention is directed to an optical circuit having a selectable output. The optical circuit includes a first input coupled to receive a first optical signal and a first intermediate optical circuit coupled to the first input. The first intermediate circuit has first and second intermediate circuit outputs. The first intermediate circuit has a first state and a second state. The first intermediate circuit directs the first optical signal only to the first intermediate circuit output when in the first state and directs a first portion of the first optical signal to the first intermediate circuit output and a second portion of the first optical signal to the second intermediate circuit output when in the second state. The circuit includes a second input coupled to receive a second optical signal. A second intermediate optical circuit is coupled to the second input. The second intermediate circuit has third and fourth intermediate circuit outputs. The second intermediate circuit has a first state and a second state. When in the first state, the second intermediate circuit directs the second optical signal only to the fourth intermediate circuit output. When in the second state, the second intermediate circuit directs a first portion of the second optical signal to the fourth intermediate circuit output and a second portion of the second optical signal to the third intermediate circuit output.
Another embodiment of the invention is directed to a tunable optical splitter circuit having a first basic splitting circuit that includes a first input to receive a first input optical signal and a first switchable optical circuit coupled to receive the input optical signal from the first input. The first switchable optical circuit has first, second, third and fourth outputs. The switchable optical circuit has an input splitter stage that splits the first input optical signal into first and second input signal portions. The first switchable optical circuit comprises a switchable first intermediate circuit that either directs substantially all of the first input signal portion to the first output or splits the first input signal portion between the first and second outputs. It also includes a switchable second intermediate circuit that either directs substantially all of the second input signal portion to the fourth output or splits the second input signal portion between the third and fourth outputs.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.
The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
The present invention is directed to various optical devices and systems that can provide benefit in optical networks by providing for remote configuration, thus reducing the need for technician visits to a fiber distribution hub (FDH) and allowing various operations to be carried out more quickly than using conventional passive optical components.
In an illustrated embodiment of the invention, the optical network 100 includes a cable 110 that connects to an FDH 103. The cable 110 includes at least an optical data transmission fiber and an FDH control channel, which may be optical or electrical.
An illustrated embodiment of the FDH 103 and cable 110 is seen in greater detail in
According to an embodiment of the present invention the optical circuit 216 includes one or more remotely-controlled TIR electro-wetting on dielectric (EWOD) optical switches that may be used, for example, to change the configuration of the optical circuit or the ratio of signal split into different output channels. An advantage of the microfluidic approaches of EWOD switching is that a microfluidically-controlled optical circuit can be manufactured on a glass substrate, which is relatively inexpensive, whereas an electro-optical approach to switching requires the use of electro-optic crystals that are more expensive than glass. A remotely-controllable optical circuit (RCOC) may, for example include one or more TIR switches, such as TIR EWOD switches, that can change a splitter system from a configuration having a first number of outputs to a splitter system having a second number of outputs. In another example of an RCOC, TIR optical switches are able to provide multiple levels of coupling between two waveguides, thus allowing a user to control the amount of light that is coupled from one waveguide into one or more other waveguides.
Other approaches to moving the index matching liquid in a TIR optical switch may be used in addition to EWOD approaches, for example approaches based on moving a liquid droplet based on thermally expanding or contracting an adjacent gas bubble, and the like, as are known in the art. Where a TIR switch does not depend on EWOD activation of the liquid, non-polar liquids may be employed, such as OCF (optical coupling fluid) 446 available from Nye Lubricants, Inc., Fairhaven, Mass., USA or MIRASIL® DM 100 (a linear polydimethylsiloxane fluid) available from Bluestar Silicones USA, East Brunswick, N.J., USA
The optical circuits described herein use various combinations of three basic building blocks, the first of which is the TIR optical switch, which is discussed with reference to
In the illustrated embodiment, the channel 310 is empty at the crosspoint 312, so light 314 in the input waveguide 304 is total internally reflected at the wall of the channel 310 into the second output waveguide 308, hence this type of optical switch is referred to as a totally internally reflecting (TIR) optical switch.
The substrate 302 also includes a second TIR optical switch 320. In the illustrated embodiment the second TIR optical switch 320 is in a second, transmissive state. The second TIR optical switch 320 is formed with an input waveguide 324 terminating at the channel 310, a first output waveguide 326 across the channel 310 from the input waveguide 324, and a second output waveguide 328 that terminates at the channel 310 at a second crosspoint 332. A droplet 330 of liquid material is located within the channel 310 at the crosspoint 332. The refractive index of the liquid material is selected so that light 334 propagating along the first waveguide is incident on the wall of the channel 310 at an angle that does not result in total internal reflection at the wall of the channel 310. Accordingly, the light 334 propagates through the droplet 330 of liquid material and into the first output waveguide 326. Thus, a TIR optical switch can be in either of two states, a reflective state or a transmissive state, depending on whether the liquid material is present at its crosspoint.
Different liquids may be used as index-matching liquids in the channel 310. For example, when the TIR optical switch is an EWOD TIR optical switch, a liquid such as hydroxypropylene carbonate or propylene carbonate may be used. Additional liquids that may be used include preferably polar organic compounds such as methanol, ethanol, and other alcohols, ethylene glycol and propylene glycol, methyl formamide, or formamate, are discussed in U.S. Provisional Patent Application No. 62/393,463, titled “Liquids For Use With Electro-Wetting On Dielectric Active Optical Switch,” filed on Sep. 12, 2016, and incorporated herein by reference. Additionally, non-polar organic compounds may be used as the liquid in embodiments where the liquid is moved using an approach that does not involve the use of a polar compound. Examples include OCF (optical coupling fluid) 466 available from Nye Lubricants, Inc., Fairhaven, Mass., USA, and silicon-based liquids such as MIRASIL® DM 100 (a linear dimethylsiloxane fluid), available from Bluestar Silicones USA, East Brunswick N.J., USA.
It should be understood that the angle α between the input and second output waveguide may be selected to be any suitable angle, depending on various factors including, but not restricted to, the refractive indices of the waveguides, the waveguide numerical aperture, the refractive index of the liquid material and manufacturing tolerances. The value of α is 90° in the illustrated embodiment, but values smaller or greater than this value may also be selected that result in total internal reflection when the TIR optical switch is in the reflective state and transmission through the liquid material when it is present at the crosspoint.
The droplet 330 of liquid material may be moved along the channel 310 using an applied electro-wetting force, which results from the application of an electric field asymmetrically across the droplet 330. A cross-sectional view through the substrate 302, along line AA′, is shown in
The droplet 330 of liquid may be made to move via an electro-wetting force applied via the electrodes. The application of an electric field to an electro-wetting liquid reduces its surface energy. If the electric field is applied asymmetrically to only one side of a droplet of the liquid, the surface energy of that part of the droplet exposed to the electric field is reduced, resulting in the liquid droplet flowing to the side of the droplet of the applied electric field. Thus, the liquid droplet can be moved via sequential application of an electric field to electrode 360c, then electrode 360d and then electrode 360e.
Thus, a TIR optical switch has the following states:
The second building block is a y-branch coupler, an exemplary embodiment of which is shown in
The third optical circuit building block is a wavelength-dependent reflector unit 500, an embodiment of which is schematically illustrated in
A first waveguide 508 and a second waveguide 510 are directed to cross at the surface of the thin film filter 504 that contains the multilayer dielectric stack. The slot 506 for the thin film filter 504 cuts across the waveguides 508, 510 and so is preferably thin, for example around 20 μm or less. In one embodiment, light at a first wavelength λ1 is injected into the right side of the first waveguide 508 while light at a second wavelength, λ2, and third wavelength, λ3, is injected into the left side of the first waveguide 508. In this embodiment, λ1<λ2, λ3, and the thin film filter 504 reflects light having a wavelength longer than λ2, i.e. operates as a short pass filter. Thus, the light at λ1 is transmitted through the thin film filter and propagates to the left side of the first waveguide 508, and the light at λ2 is transmitted through the thin film filter and propagates to the right side of the first waveguide 508. The light at λ3, however, is reflected by the thin film filter 504 and propagates along the left side of the second waveguide 510. In other embodiments, the thin film filter 504 may be a short pass filter having a shorter cutoff wavelength, e.g. having a cutoff wavelength between λ1 and λ2 so that it transmits light at λ1 while reflecting light at λ2 and λ3), or may be a high pass filter (e.g. transmitting light at λ3 while reflecting light at λ1 and λ2), a notch filter (e.g. transmitting light at λ1 and λ3, while reflecting light at λ2), or a bandpass filter (e.g. transmitting light at λ2, while reflecting light at λ1 and λ3).
The building block elements described above may be integrated into optical chips based on silica glass, e.g. PLC chips, using low index contrast or high index contrast waveguides. Low index contrast waveguides are typically easier to connect to via a pigtailed fiber as they have a relatively large core dimension. High index contrast waveguides, on the other hand, allow low-loss implementation of tighter fiber bends than low index contrast waveguides, and fiber pig-tailing can be accomplished via the use of spot-size converters. In PLC chips, the channel in a TIR optical switch and the slot in a wavelength-dependent reflector unit may be formed using an etching technique such as reactive ion etching (RIE), including deep reactive ion etching (DRIE).
A first embodiment of an optical circuit, or part of an optical circuit, using these building blocks is schematically represented in
In the description provided herein, the optical circuits are implemented as waveguide circuits on a substrate. Thus, when the description refers to an “input” or an “output,” it should be understood that these terms respectively refer to a waveguide along which light propagates into a circuit element and a waveguide along which light propagates from a circuit element. It should also be appreciated that many optical circuits are reversible, in that light can propagate in a forward direction or in a backwards direction through an optical circuit. Accordingly, the present description, the terms “input” and “output” do not require that light propagate only in a single direction through the optical elements of the circuit. Instead, these terms are used to describe one of the directions of propagation through the optical circuit in order to help the reader understand how the optical circuit operates. For example, in one direction an optical splitter may be used to split an optical signal propagating along a single path into several optical signals propagating along respective paths. In reverse, the optical splitter will combine optical signals propagating along different paths into an optical signal propagating along one path.
In the embodiment illustrated in
In the embodiment illustrated in
Another embodiment of an optical circuit 700, which operates as a wavelength band switch, is schematically illustrated in
A second output 718 from the first optical switch 704 is directed to a first wavelength selective reflector unit 720, which reflects light having a wavelength up to around 1. Light having a wavelength of up to around 1 is referred to as being in band 131, see
Light having wavelength of up to around λ2, where λ2 is longer than is referred to as being in band B2 while light having a wavelength of greater than around λ2 is referred to as being in band B4. Thus, when a light signal containing light having a wavelength component greater than λ1 and a wavelength component less than λ1 is incident on the first wavelength selective reflector unit 720, only light having a wavelength of up to around λ1, i.e. light in band B1, is reflected while light in band B2 is transmitted.
The light reflected from the first wavelength selective reflector unit 720 is directed along path 721 as a second input to the second optical switch 708. A first output 722 of the second optical switch 708 is coupled as a second input to the fourth optical switch 716. A second output 724 of the second optical switch 708 may be used as a second circuit output. When the fourth optical switch 716 is in the bar state, the optical signal on the third switch output waveguide 714 is directed to the output waveguide 726.
Another embodiment of wavelength selector circuit 740 is schematically illustrated in
The second circuit input 744 is coupled to a second wavelength selective reflector unit 758. Light reflected by the second wavelength selective reflector unit 758 is directed along path 760 as a second input to the first TIR optical switch 750. Light transmitted through the second wavelength selective reflector unit 758 propagates along path 762 as a first input to a third TIR optical switch 764. A second output 766 from the first TIR optical switch 750 is coupled as a second input to the third TIR optical switch 764. First and second circuit outputs 768, 770 are coupled to receive light signals from the second TIR optical switch 754, while third and fourth circuit outputs 772, 774 are coupled to receive light signals from the third TIR optical switch 764.
In the illustrated embodiment, the first wavelength selective reflector unit 744 reflects light having a wavelength of no more than about 1, i.e. reflects light in band B1, and transmits light in band B3. Thus, if light having wavelength components both greater than and less than λ1 is incident along the first circuit input 742, then light in band B1 is directed to the first optical switch 750 along path 748 and light in band B3 is directed along path 752 to the second optical switch 754. Also, the second wavelength selective reflector unit 758 reflects light having a wavelength of no more than about λ2, i.e. reflects light in band B2, and transmits light in band B4. Thus, if light having wavelength components both greater than and less than λ2 is incident along the second circuit input 744, then light in band B2 is directed to the first TIR optical switch 750 along path 760 and light in band B4 is directed along path 764 to the third TIR optical switch 764.
In the circuit configuration illustrated in
It will be appreciated that other configurations of this circuit may be employed. For example, changing the second TIR optical switch 754 from the cross state to the bar state will result in swapping the optical signals appearing at the first and second circuit outputs 768, 770.
Another optical circuit 780 is schematically presented in
In the illustrated embodiment, the first optical switch 750 is in the bar state, and so the light propagating along path 748b into the first optical switch 750 is directed along the first optical switch first output 756 to a second input to the second switch 754. The second optical switch 754 is in the cross state, so the light in band B3, entering the first input to the second optical switch 754 is directed to the second circuit output 770, and the light in band ΔB12, propagating along path 756 is directed to the first circuit output 768.
Another light signal enters the optical circuit 780 along the second circuit input 744 to the third wavelength selective reflector unit 758a. In this embodiment, the third wavelength selective reflector unit 758a reflects light having a wavelength less than λ4, so light in band B8 propagates along the transmitted output path 762 from the third wavelength selective reflector unit 758a as an input to the third TIR optical switch 764. The light reflected along path 760a from the third wavelength selective reflector unit 758a is in band B6 and is directed to a fourth wavelength selective reflector unit 758b. The second wavelength selective reflector unit 758b reflects light having a wavelength less than about λ3, i.e. light in band B5, along path 784. Light transmitted by the fourth wavelength selective reflector unit 758b along path 760b lies in the wavelength band between about λ3 and λ4, and is designated as being in band ΔB56.
In the illustrated embodiment, the first TIR optical switch 750 is in the bar state, and so the light propagating along path 760b, in band ΔB56. into the first optical switch 750 is directed along the first optical switch second output 766 to a second input to the third TIR optical switch 764. The third TIR optical switch 764 is in the cross state, so the light in band B8, entering the second input to the third optical switch 764 is directed to the third circuit output 772, and the light in band ΔB56, propagating along path 766, is directed to the fourth circuit output 774. In this switch configuration, the optical circuit 780 may be said to be in a “pass state,” as light in the wavelength band ΔB12, which entered along the upper half of the circuit 780, passes along the upper half of the circuit 780. Also, light in the wavelength band ΔB56, which entered along the lower half of the circuit 780, passes along the lower half of the circuit 780.
It will be appreciated that other configurations of the circuit 780 may be employed. For example, changing the second optical switch 754 from the cross state to the bar state will result in swapping the optical signals appearing at the first and second circuit outputs 768, 770.
An optical circuit 800 that operates as a wavelength pass drop unit is schematically illustrated in
In the embodiment illustrated in
In the embodiment illustrated in
The optical circuit 800 may be repeatedly used in a cascaded fashion to provide switchable separation of multiple wavelength bands. For example, an optical circuit 850 shown in
The second wavelength pass/drop unit 854 contains a wavelength-selective reflector unit that reflects light in the wavelength bands B1 and B3, and transmits light in the wavelength band B2. The optical signals passed through the second wavelength pass/drop unit 854 are output along output 864, while the optical signal dropped by the second wavelength pass/drop unit 854 is output along output 862. Thus, the second wavelength pass/drop unit can separate the optical signal in the wavelength band B2 from the other wavelength bands.
The appearance of optical signals at different wavelength bands on the different outputs 860, 862, 864 depends on the state of the wavelength pass/drop units 852, 854. The following table shows the wavelength bands of optical signals appearing on the various outputs 860, 862, 864 for the various possible combinations of states of the wavelength pass/drop units 852, 854.
Thus, the optical signals in the various wavelength bands may be separated from each other. It will be appreciated that additional wavelength pass/drop units might be cascaded in a similar manner in order to provide capabilities for separating optical signals in a different number of wavelength bands.
An exemplary application of a wavelength pass/drop unit is shown schematically in
Another embodiment of the present invention relates to a circuit that is effectively a splitter circuit having selectable splitting ratios. One example of a circuit 900 having selectable splitting ratios is schematically illustrated in
The second output 918 from the second TIR switch 910 is input to a first y-branch coupler 920, which may be a 3 dB coupler or an asymmetric coupler. For consideration of the present embodiment, the first y-branch coupler 920 is a 3 dB coupler. The first y-branch coupler 920 has a first output 922 that is coupled as an input to a fourth TIR switch 924. One of the outputs 926 of the fourth TIR switch 924 is coupled as a second input to the third TIR switch 914. The other output 925 from the first y-branch coupler 920 may be used as a circuit output, Output 2.
The lower half of the circuit 900 is the mirror image of the top half. The second output 928 from first TIR switch 906 is directed to a fifth TIR switch 930. A first output 932 from the fifth TIR switch 930 is directed as a first input to a sixth TIR switch 934. When the fifth TIR switch 930 is in the cross state, the optical signal propagating along the second output 928 from the first TIR switch 906 is directed by the fifth TIR switch 930 to its first output 932. Only one output 936 from the sixth TIR switch 934 is used as a circuit output, Output 4. Light propagating along waveguide 932 into the sixth TIR switch 934 is passed to the output 936 when the sixth TIR switch 934 is in the bar state.
The second output 938 from the fifth TIR switch 930 is input to a second y-branch coupler 940, which may be a 3 dB coupler or an asymmetric coupler. For consideration of the present embodiment, the second y-branch coupler 940 is a 3 dB coupler. The second y-branch coupler 940 has a first output 942 that is coupled as an input to a seventh TIR switch 944. One of the outputs 946 of the seventh TIR switch 944 is coupled as a second input to the sixth TIR switch 934. The other output 948 from the second y-branch coupler 940 may be used as a circuit output, Output 3.
In the embodiment shown in
In this this switch configuration, no optical signal is directed through either the fourth or the seventh TIR optical switches 924, 944, and so their switch states do not affect the output of the circuit 900. Thus, in some embodiments, these switches 924, 944 may be omitted.
In the embodiment of circuit 900 illustrated in
In addition, one half of the light entering the first y-branch coupler 920 is output along waveguide 925 to Output 2, and one half of the light entering the second y-branch coupler 940 is output along waveguide 948 to Output 3. Thus, in this switch configuration, the circuit 900 provides P1/2 to each of Outputs 1 and 2 and provides P2/2 to each of Outputs 3 and 4.
The circuit 900 may be configured in other ways, for example, to split light from one of its inputs but not from the other. For example, in
In another switch configuration, schematically illustrated in
It will be appreciated that there may be variations on the selective splitter circuit 900 shown in
A variation of the selective splitter circuit 900, schematically illustrated in
A selective splitter circuit as discussed above may be used a basic building block for a larger circuit that provides more splitting ratio options.
A further example of an optical circuit 1100, configured with two basic selective splitter circuits operating in parallel, is shown in
In
Another example of optical circuit 1200 that can be built using two stages of basic selective splitter circuits is schematically illustrated in
In the illustrated configuration, the first basic selective splitter circuit 1206 is in State 1, and so 50% of the input optical signal is transmitted along waveguide 1208 and 50% is transmitted along waveguide 1224. The second basic selective splitter circuit 1212 is in State 1, so the power entering along waveguide 1208 is transmitted to output 1214. The third basic selective splitter circuit 1226 is in State 2, so the power entering along waveguide 1224 is split evenly between outputs 1232 and 1234.
A different configuration of the optical circuit 1200 is shown in
Another configuration of the optical circuit 1200 is shown in
It will be appreciated that the optical power in the various outputs from the optical circuit 1200 can be varied by selecting the states of the various basic selective splitter circuits.
Another approach for an optical splitter 1300 having a tunable splitting ratio is schematically illustrated in
Each y-branch coupler 1314 has associated with it a TIR switch 1310 on the input waveguide 1304 that directs light from the input waveguide 1304 to the respective y-branch coupler 1314. Also, each y-branch coupler 1314 has an associated TIR optical switch 1320 on the first output waveguide 1306 and an associated TIR optical switch 1322 on the second output waveguide 1306. When it is desired to split the incoming optical signal using a ratio of one of the y-branch couplers 1314, the TIR switches 1310, 1320, 1322 associated with that particular y-branch coupler 1314 are set to the cross (reflective) state, while all other TIR switches that the optical signal has to pass through are set to the bar (transmissive) state. In the illustrated embodiment, the optical signal is split at a ratio of 70:30, so the TIR optical switch 1310 associated with the second y-branch coupler 1314b is set to reflect the optical signal from the input waveguide 1304 to the 70:30 y-branch coupler 1314b.
It will be appreciated that the tunable optical splitter 1300 may include y-branch couplers having splitting ratios different from those shown in the exemplary embodiment, and may also include a different number of y-branch couplers. While it is important that the TIR optical switches that the optical signals pass through are in a transmissive state, the state of the TIR optical switches through which the optical signals do not pass is not important. For example, in the illustrated embodiment, the second TIR switch 1310 along the input waveguide 1304 is in the reflective state. Accordingly, the first TIR switch 1310 along the input waveguide 1304 has to be in the transmissive state for the optical signal to reach the second TIR optical switch 1310. However, the state of the third and fourth TIR optical switches 1310 on the input waveguide 1304 is unimportant, as the optical signal does not reach these switches before being reflected output of the input waveguide to a y-branch coupler 1314. Therefore, the third and fourth TIR switches on the input waveguide 1304 may be either in the reflective or transmissive state. Likewise, once reaching the first and second output waveguides 1306, 1308, the optical signals do not pass through the first TIR optical switches 1320, 1322 associated with y-branch coupler 1314a, so the state of these switches is not important. Thus, the first TIR switches 1320, 1322 may be in either the reflective or transmissive state.
While various examples were provided above, the present invention is not limited to the specifics of the examples. For example, various combinations of elements shown in different figures may be combined together in various ways to form additional optical circuits not specifically described herein. It is intended that the invention cover certain embodiments of the optical circuits discussed above in which all of the optical switches in a circuit are TIR EWOD optical switches.
As noted above, the present invention is applicable to fiber optical communication and data transmission systems. Accordingly, the present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
This application is being filed on Aug. 16, 2018 as a PCT International Patent Application and claims the benefit of U.S. Patent Application Ser. No. 62/546,410, filed on Aug. 16, 2017, the disclosure of which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/000187 | 8/16/2018 | WO | 00 |
Number | Date | Country | |
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62546410 | Aug 2017 | US |