Abstract:
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for optical switching. An optical switch device includes a first multicast switch unit; and a second multicast switch unit, wherein each of the first and second multicast switch units respectively include: multiple optical input ports; multiple optical switches; multiple optical splitters/combiners; and multiple optical output ports.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119 to U.S. Provisional Application 61/803,082, filed on Mar. 18, 2013, which is incorporated here by reference. 
     
    
     BACKGROUND 
       [0002]    This specification relates to optical switching. 
         [0003]    There are a large number of various types of optic switches, all aiming to achieve light beam switching between one or more input optical fiber and one or more corresponding output optical fibers. Optic switches are typically used in the optical fiber communication industries, instrument industries, and defense industries. 
       SUMMARY 
       [0004]    In general, one innovative aspect of the subject matter described in this specification can be embodied in optical devices that include a drop optical multicast switch unit, including: multiple input optical ports, multiple optical splitters, each optical splitter coupled to a corresponding input optical port, multiple optical switches, each optical switch coupled to each optical splitter of the multiple optical splitters, and multiple output optical ports; and an add optical multicast switch unit, including; multiple input optical ports; multiple optical switches, each optical switch coupled to a corresponding input optical port; multiple optical splitters, each optical combiner coupled to each optical switch of the multiple optical switches, and multiple output optical ports coupled to a corresponding optical combiner. 
         [0005]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. The first optical multicast switch unit and the second optical multicast switch unit are symmetrical. The first optical multicast switch unit is N×M and second optical multicast switch unit is A×B, where N×M is distinct from A×B. The optical switches are MEMS based optical switches. The multiple optical switches in first optical multicast switch unit include L×1 selectors, wherein L≧N. Extra input ports (L−N) of the L×1 selectors of the multiple optical switches are reserved as expansion ports. An input optical signal at a first optical input port of the first optical multicast switch unit is split into M portions by a corresponding optical splitter and distributed to each of the multiple optical switches. Each optical switch of the multiple optical switches in the first optical multicast switch unit receives an input from each input optical port and selects one to output to an output optical port. An input optical signal at a first optical input port of the second optical multicast switch unit is input to a first switch of the multiple optical switches, wherein the first switch is coupled to each of the multiple optical combiners such that the first switch can pass the input optical signal to any one of the multiple optical combiners. 
         [0006]    In general, one innovative aspect of the subject matter described in this specification can be embodied in twin multicast switch modules including a first multicast switch unit; and a second multicast switch unit, wherein each of the first and second multicast switch units respectively includes: multiple optical input ports; multiple optical switches; multiple optical splitters/combiners; and multiple optical output ports. 
         [0007]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. The first multicast switch unit is a drop unit and the second multicast switch unit is an add unit. 
         [0008]    Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. A twin multicast switch provides both an add unit and a drop unit in a compact module. The twin multicast switch also has the advantages of low insertion loss, low electrical power consumption, hitless operation, as well as very low cross-talks. 
         [0009]    The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a diagram of an example twin N×M multicast switch module. 
       
    
    
       [0011]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0012]      FIG. 1  is a diagram of an example twin multicast switch module  100 . The twin multicast switch module  100  includes a first optical multicast switch (MCS) unit  102  and a second MCS unit  104 . The first and second MCS units  102  and  104  are configured as part of the same module, but operate independently. In particular, the first MCS unit  102  and second MCS unit  104  can operate in opposite directions where the first MCS unit  102  is configured to drop optical signals while the second MCS unit  104  can be configured to add optical signals. 
         [0013]    The first MCS unit  102  includes N input optical ports  106 , N optical splitters  108 , M optical switches  110 , and M output optical ports  112 . Each input optical port  106  is coupled to a corresponding input optical fiber. Similarly, each output optical port  112  is coupled to a corresponding output optical fiber. 
         [0014]    Each input optical port  106  is optically coupled to a corresponding optical splitter  108 . For example, input optical port  106   a  is optically coupled to optical splitter  108   a . The optical splitters  108  are, for example, planar lightwave circuit splitters, that separate an incoming light signal into a specified number output of light signal branches. For example, in the example shown in  FIG. 1 , each optical splitter  108  separates an incoming optical signal from a corresponding input optical port  106  into M optical branches. In particular, each optical splitter  108  can be configured to separate an incoming optical signal into a number of optical signals that corresponds to the number of optical switches  110 . 
         [0015]    The optical switches  110  can be any suitable compact, low loss, and lower power switch. For example, the optical switches  110  can be micro-electro-mechanical-systems (MEMS) based optical switches. The optical switches  110  include L×1 selectors where L is greater than or equal to the number of input optical ports N. In particular, each optical switch  110  receives an input to a selector of the L selectors from each respective optical splitter  108 . Thus, each optical switch  110  has an input corresponding to each optical input port  106 . 
         [0016]    For example, a first input port of each L×1 optical switch  110  is optically coupled to one branch of a first optical splitter  108 , a second input port of each optical switch  110  is optically coupled to one branch of a second optical splitter  108  and a N-th input port of each optical switch  110  is optically coupled to one branch of a N-th optical splitter  108 . 
         [0017]    Additionally, there can be additional unused selectors in one or more of the optical switches  110  when L is greater than N. In some implementations, these extra selector ports of the optical switches  110  are reserved for upgrade purposes as expansion ports. There are (L−N) expansion ports. The extra ports are grouped by sequentially selecting one of the extra ports from each optical switch and each group is used as an expansion array-port for future upgrade. The expansion array-port can be used, for example, if an additional input optical port is added to the MCS unit  102 . 
         [0018]    In operation, optical signals into any optical input port  106  are split into M portions by the optical splitters  108 . The optical signals are then distributed to each of the M switches  110 . Thus, each of the M optical switches  110  receives optical signals from all of the N input optical ports  106 . The optical switches  110  each controllably couple one of the received optical signals to a corresponding output optical port  112 . As a result, one or more signals from the N input optical ports  106  are selectively output by M output optical ports  112 . For example, the optical signal from a first input optical port  106  can be switched to any number of output optical ports from zero to M. 
         [0019]    The second MCS unit  104  includes M input optical ports  114 , M optical switches  116 , N optical combiners  118 , and N output optical ports  120 . Each input optical port  114  is coupled to a corresponding input optical fiber. Similarly, each output optical port  120  is coupled to a corresponding output optical fiber. 
         [0020]    Each input optical port  114  is optically coupled to a corresponding optical switch  116 . For example, input optical port  114   a  is optically coupled to optical switch  116   a . The optical switches  116  can be any suitable compact, low loss, and lower power switch. For example, the optical switches  116  can be MEMS based optical switches. The optical switches  116  include 1×L selectors where L is greater than or equal to the number of output ports N. At least N selectors of each optical switch  116  are optically coupled to branches of the respective optical combiners  118 . However, additional selectors when L is greater than N can be included as expansion ports as described above. 
         [0021]    The optical combiners  118  are, for example, planar lightwave circuit combiners, that combine multiple incoming light signals into a single light signal that corresponds to an optical output port  120 . For example, in the MCS unit  104  of  FIG. 1 , each of the optical combiners  118  includes a branch that is optically coupled to a respective port of each optical switch  116 . 
         [0022]    Thus, each optical switch  116  has output corresponding to a branch of each optical combiner  118 , and therefore to each output optical port  120 . For example, a first output port of each 1×L optical switch  116  is optically coupled to one branch of a first optical combiner  118 , a second output port of each optical switch  116  is optically coupled to one branch of a second optical combiner  118  and a N-th output port of each optical switch  116  is optically coupled to one branch of a N-th optical combiner  118 . 
         [0023]    In operation, optical signals into any optical input port  114  are input into corresponding optical switches  116 . Each optical switch  116  selectively passes the input optical signals to a particular output port of the optical switch  116 . The optical signal is routed to a particular optical combiner  118  based on the selected output port. One or more optical signals received at a particular optical combiner  118  are combined and passed to a corresponding output optical port  120 . Thus, each of the M received optical signals are selectively routed to one or more of the N output optical ports  120 . For example, a first optical signal from a first input port and a second optical signal from a second input port can be switched to the same output optical port or different optical ports depending on the switch positions. 
         [0024]    Both the first MCS unit  102  and the second MCS unit  104  as shown are symmetrical N×M units. The value of N can be, for example, 4, 8, 12 or 16 ports while the corresponding value of M can be, for example, 4, 8, 12, or 16 ports. 
         [0025]    The first MCS unit  102  and the second MSC unit  104  can also be asymmetrical. For example, the first MCS unit  102  can be an N×M unit while the second MCS unit  104  can be an A×B unit having a distinct number of input and output optical ports. 
         [0026]    The optical splitters  108  and optical combiners  118  can be optically bi-direction. Therefore, the optical splitters  108  and optical combiners  118  can be the same optical devices. The optical splitters and optical switches can be wideband devices such that the ports of twin multicast switch module  100  are wavelength independent. 
         [0027]    While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
         [0028]    Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
         [0029]    Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.