Patent Publication Number: US-2021181423-A1

Title: Multi-Channel Mode Converters With Silicon Lenses

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of International Patent App. No. PCT/CN2019/091406 filed on Jun. 14, 2019, which claims priority to U.S. Prov. Patent App. No. 62/784,928 filed on Dec. 26, 2018, both of which are incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate to silicon photonics in general and mode converters for silicon photonics in particular. 
     BACKGROUND 
     Silicon photonic devices use silicon and its derivatives to form waveguides. In addition to the waveguides, silicon photonic devices often comprise fibers. There is a need to convert modes of the waveguides to modes of the fibers and vice versa. 
     A mode is a shape of a light beam at an entrance or an exit of a waveguide, a fiber, or another medium. A mode size is the physical size of a mode. The physical size may be based on optical intensity. For instance, a light beam below a specified optical intensity may not be considered part of the physical size. 
     SUMMARY 
     In an embodiment, a multi-channel mode converter includes a lens array having a first lens, a second lens, a glass block coupled to the lens array, and a fiber assembly unit (FAU) array coupled to the glass block and including a first fiber corresponding to the first lens, and a second fiber corresponding to the second lens. The lens array can be formed from a composition comprising silicon. In any of the preceding embodiments, the glass block can be formed from a composition comprising optical glass, which can be a borosilicate crown glass such as BK7. In any of the preceding embodiments, the glass block is a glass capillary block comprising a glass capillary. In any of the preceding embodiments, the lens array includes a third lens, and the FAU array includes a third fiber corresponding to the third lens. In any of the preceding embodiments, the lens array includes a fourth lens, and the FAU array includes a fourth fiber corresponding to the fourth lens. In any of the preceding embodiments, the FAU array is offset from centers of the first lens and the second lens. In any of the preceding embodiments, the lens array has a width of about 1 mm-about 5 mm, a length of about 0.5 mm-about 1 mm, and a height of about 0.5 mm-about 2 mm. In any of the preceding embodiments, the glass block has a width of about 1 mm-about 5 mm, a length of about 0.5 mm to about 2 mm, and a height of about 0.5 mm-about 2 mm. In any of the preceding embodiments, the FAU array has a width of about 1 mm-about 5 mm, a length of about 2 mm-about 5 mm, and a height of about 0.5 mm-about 2 mm. 
     In an embodiment, a mode converter system includes a lens array having a first silicon lens configured to convert a first mode between a first waveguide and a first fiber, and a second silicon lens configured to convert a second mode between a second waveguide and a second fiber; and a glass block coupled to the lens array and configured to provide an optical path for a first light beam corresponding to the first silicon lens and a second light beam corresponding to the second silicon lens. The mode converter system can include a waveguide block coupled to the lens array, the waveguide block having a first waveguide configured to guide the first light beam into the waveguide block, and a second waveguide configured to guide the second light beam into the waveguide block. In any of the preceding embodiments, the mode converter system further includes a fiber assembly unit (FAU) array coupled to the glass block, the FAU array including the first fiber and the second fiber. In any of the preceding embodiments, the FAU array is offset from centers of the first silicon lens and the second silicon lens. In any of the preceding embodiments, the first silicon lens and the second silicon lens have a magnification of about 1.5-about 5. In any of the preceding embodiments, the first silicon lens and the second silicon lens are configured to reduce an FAU array pitch tolerance by a ratio based on the magnification. 
     In an embodiment, a method is provided for manufacturing a mode converter. The method includes coupling a reflector to a lens to form a lens assembly, coupling a coupler to a fiber of a fiber assembly unit (FAU), a light source to the coupler, and a power meter to the coupler to form an FAU assembly. The lens assembly and a glass block are positioned at an end of the FAU assembly. A light beam is emitted from the light source into the coupler, and a power of a reflected light beam is obtained using the power meter, the reflected light beam is associated with the light beam; and aligning the lens assembly and the FAU assembly based on the power. In any of the preceding embodiments, the method includes aligning the lens assembly and the FAU assembly until the power is greatest at the exit end of the FAU assembly. In any of the preceding embodiments, the method further includes removing, after the aligning, at least one of the reflector, the coupler, the light source, or the power meter. 
     Any of the above embodiments may be combined with any of the other above embodiments to create a new embodiment. These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
         FIG. 1A  is a perspective view of a schematic diagram of a multi-channel mode converter according to an embodiment of the disclosure. 
         FIG. 1B  is an exploded view of a schematic diagram of the multi-channel mode converter in  FIG. 1A . 
         FIG. 1C  is a light diagram of the multi-channel mode converter in  FIGS. 1A and 1B  used with a straight waveguide according to an embodiment of the disclosure. 
         FIG. 1D  is a light diagram of the multi-channel mode converter in  FIGS. 1A and 1B  used with an angled waveguide according to an embodiment of the disclosure. 
         FIG. 1E  is a pitch tolerance diagram of the multi-channel mode converter in  FIGS. 1A and 1B  according to an embodiment of the disclosure. 
         FIG. 2  is a schematic diagram of a single-channel mode converter according to an embodiment of the disclosure. 
         FIG. 3A  is a mode converter manufacturing system according to an embodiment of the disclosure. 
         FIG. 3B  is a flowchart illustrating a mode converter manufacturing method using the mode converter manufacturing system in  FIG. 3A  according to an embodiment of the disclosure. 
         FIG. 4  is a schematic diagram of a single-channel mode converter according to another embodiment of the disclosure. 
         FIG. 5  is a schematic diagram of a single-channel mode converter system according to an embodiment of the disclosure. 
         FIG. 6  is a schematic diagram of a multi-channel mode converter system according to an embodiment of the disclosure. 
         FIG. 7  is a schematic diagram of a multi-channel mode converter system according to another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that, although illustrative implementations of embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
     The following abbreviations apply: 
     FAU: fiber assembly unit 
     LED: light-emitting diode 
     mm: millimeter(s) 
     PLC: planar lightwave circuit 
     PM: polarization-maintaining 
     SMF: single-mode fiber 
     SOI: silicon on insulator 
     μm: micrometer(s). 
     In silicon photonic devices, mode sizes of waveguides are typically about 2 μm-about 6 μm and mode sizes of fibers are typically about 9 μm. Due to the difference between the mode sizes, silicon photonic devices comprise mode converters, or optical mode converters, to move light beams between the waveguides and the fibers. Such mode converters may be single-channel mode converters, meaning they move light beams between one waveguide and one fiber to form one channel, or multi-channel mode converters, meaning they move light beams between more than one waveguide and more than one fiber to form multiple channels. Challenges faced in developing and deploying silicon photonic devices include the following: 
     A pitch tolerance is a difference between a designed pitch and an actual pitch. A pitch is a distance between centers of two adjacent light media. The light media may be waveguides or fibers. Pitch tolerances of waveguides are typically about ±0.3 μm or less because lithography processes provide for small tolerances. However, pitch tolerances of fibers are typically about ±1.0 μm. The differences in pitch tolerances between waveguides and fibers increase mode coupling losses. 
     Waveguides often are angled in order to reduce back reflection at their interfaces. To accommodate waveguide angling, the components comprising the fibers, which are often FAU arrays, are also angled. However, FAU angling introduces difficulties in assembling silicon photonic devices. 
     PLC mode converters are about 3 mm long in a direction from a waveguide to a fiber and suffer additional insertion losses from the PLC mode converter chips themselves. Furthermore, PLC mode converters suffer from coupling losses due to air gaps between the PLC mode converters and the waveguides and due to bonding of the PLC mode converters to FAUs. Moreover, to reduce the air gaps and thus the coupling loss, epoxy coupling the PLC mode converters and the waveguides is often thin, which can introduce mechanical instability. 
     Some mode converters couple components using passive coupling in a housing. However, the passive coupling requires high precision. In addition, the mode converters are single-channel mode converters. It is therefore desirable to provide mode converters that overcome the issues described above. 
     Disclosed herein are embodiments for multi-channel mode converters with silicon lenses. The mode converters include lens arrays with silicon lenses, glass blocks, FAUs, and fibers. The silicon lenses provide a reduction of an FAU pitch tolerance, which reduces a mode coupling loss. When waveguides are angled, the FAUs are offset instead of angled, which simplifies an assembly process. Mode converters with silicon lenses provide for shorter lengths, do not suffer from on-chip losses like PLC mode converters, do not suffer from air gaps and thus coupling losses like PLC mode converters, and do not suffer from thin epoxy coupling and thus mechanical instability like PLC mode converters. The mode converters may be actively aligned to ease precision requirements. Finally, the mode converters are single-channel mode converters or multi-channel mode converters. 
       FIG. 1A  is a perspective view of a schematic diagram of a multi-channel mode converter  100  according to an embodiment of the disclosure.  FIG. 1B  is an exploded view of a schematic diagram of the multi-channel mode converter  100  in  FIG. 1A . The multi-channel mode converter  100  comprises a lens array  110 , a glass block  120 , and an FAU array  130 . The FAU array  130  comprises four fibers  140 . 
     The lens array  110  has a composition comprising silicon. The lens array  110  has a width of about 1 mm-about 5 mm, a length of about 0.5 mm-about 1 mm, and a height of about 0.5 mm-about 2 mm. The lens array  110  is dry etched to form four lenses. Like the lens array  110 , the lenses have a composition comprising silicon and may therefore be referred to as silicon lenses. The lenses convert modes between a waveguide (not shown) and the fibers  140 , meaning the lenses convert the mode diameter of the waveguide to the same mode diameter as the fiber and vice versa. The lenses have a magnification of about 1.5-about 5.0, for instance, 1.5-5.0×. Details concerning the lenses and waveguide are provided below. 
     The glass block  120  has a composition comprising optical glass. For example, the optical glass is a borosilicate crown glass such as BK7. The glass block  120  has a width of about 1 mm-5 mm, a length of about 0.5 mm-2 mm, and a height of about 0.5 mm-about 2 mm. The length is proportional to a conversion ratio, which is a ratio of the mode diameter of the fibers  140  to the mode diameter of the waveguide. The glass block  120  provides an optical path between the lens array  110  and the FAU array  130 . 
     The FAU array  130  can be provided with a pitch of, for instance, about 127 μm, about 250 μm, or about 500 μm. As used herein, “pitch” refers to the center distance between two adjacent fibers. The FAU array  130  has a width of about 1 mm-about 5 mm, a length of about 2 mm-about 5 mm (exclusive of the fibers  140 ), and a height of about 0.5 mm-about 2 mm. 
     The fibers  140  are single-mode fibers (SMFs) or polarization-maintaining (PM) fibers. The fibers  140  include a core, an inner cladding, and an outer cladding (not shown) formed of, for example, glass. The core has a diameter of about 2-about 10 μm and, the inner cladding has a diameter of about 125 μm, and the outer cladding is a coating and has a diameter of about 0.25 mm-about 1 mm. The inner cladding protects the core, and the outside coating protects the inner cladding. A first fiber  140  corresponds to, or is paired with, a first lens; a second fiber  140  corresponds to a second lens; a third fiber  140  corresponds to a third lens; and a fourth fiber  140  corresponds to a fourth lens. The multi-channel mode converter  100  is multi-channel because it comprises more than one fiber-in this case, four fibers  140 . 
     In operation, in a direction from the waveguide to the fibers  140 , light beams exit the waveguide and enter the lenses, the lenses convert a mode of the light beams from a waveguide mode to a fiber mode, and the glass block  120  passes the light beams to the fibers  140 . In a direction from the fibers  140  to the waveguide, light beams exit the fibers  140  and enter the glass block  120 , the glass block  120  passes the light beams to the lenses, the lenses convert a mode of the light beams from a fiber mode to a waveguide mode, and the light beams enter the waveguide. 
     Alternatively, the lens array  110  comprises two, three, or more than four lenses, and the FAU array  130  comprises two, three, or more than four fibers  140 . In that case, each lens corresponds to one of the fibers  140 . The number of lenses and fibers  140  may affect the sizes of the components in the multi-channel mode converter  100 . 
     The overall length of the multi-channel mode converter  100  is about 2 mm shorter than other mode converters like PLC mode converters. The reduced size of the multi-channel mode converter  100  provided through practice of the disclosed embodiments affords advantages such as a more compact configuration in high-density optoelectronic packaging applications. In addition, the multi-channel mode converter  100  does not suffer the additional insertion loss coming from the PLC mode converters chip. Furthermore, the multi-channel mode converter  100  does not suffer from air gaps and thus coupling losses like PLC mode converters. Moreover, the multi-channel mode converter  100  need not comprise a housing to couple to the components. Rather, the components may be bonded directly together. Thus, the multi-channel mode converter  100  may be said to be independent of a housing. 
       FIG. 1C  is a light diagram  150  of the multi-channel mode converter  100  in  FIGS. 1A and 1B  used with a straight waveguide according to an embodiment of the disclosure. The light diagram  150  shows the lens array  110  and the glass block  120  of the multi-channel mode converter  100  in  FIGS. 1A and 1B . The light diagram  150  also shows a lens  165  in the lens array  110  and shows a light beam  160  traveling through the lens array  110 , the lens  165 , and the glass block  120 . As shown, the lens  165  focuses the light beam  160  in order to convert modes between the waveguide and one of the fibers  140 . The light beam  160  travels in a straight direction in and out of the waveguide, so the waveguide is a straight waveguide or a non-angled waveguide 
       FIG. 1D  is a light diagram  170  of the multi-channel mode converter  100  in  FIGS. 1A and 1B  used with an angled waveguide according to an embodiment of the disclosure. The light diagram  170  is similar to the light diagram  150  in  FIG. 1C . Specifically, the light diagram  170  shows the lens array  110 , the lens  165 , the glass block  120 , and a light beam  180  traveling through the lens array  110 , the lens  165 , and the glass block  120 . 
     However, unlike the light diagram  150  in which the light beam  160  travels in a straight direction in and out of the waveguide, in the light diagram  170 , the light beam  180  travels in an angled direction in and out of the waveguide. The angled direction is at an angle θ, which is about 2°-about 15°. As shown, the glass block  120  and thus the FAU array  130  need not be angled because the lens  165  straightens the light beam  180 , or changes a direction of the light beam  180 , due to an offset between where the light beam  180  enters the lens  165  and a center of the lens  165 . The offset is about 5-about 50 μm depending on the angle θ. 
       FIG. 1E  is a pitch tolerance diagram  190  of the multi-channel mode converter  100  in  FIGS. 1A and 1B . The pitch tolerance diagram  190  shows how the lens  165  provides a reduction of an FAU array pitch tolerance on a side of the FAU array  130  to a reduced FAU array pitch tolerance on a side of the waveguide. A ratio of the reduction is a ratio of the FAU array pitch tolerance to the reduced FAU array pitch tolerance. The ratio is proportional to the magnification of the lens  165 . The reduction of the FAU array pitch tolerance reduces a mode coupling loss of the multi-channel mode converter  100 . 
     As a first example, if the lens  165  has no magnification, a pitch tolerance of the waveguide is 0.3 μm, and a pitch tolerance of the FAU array  130  is 1.0 μm, then the multi-channel mode converter  100  may have a significant coupling loss. As a second example, if the lens  165  has a magnification of 3.0, then a pitch tolerance of the FAU array  130  reduces from 1.0 μm to 0.3 μm, which matches the 0.3 μm pitch tolerance of the waveguide and therefore significantly reduces a coupling loss compared to the first example. In the second example, the waveguide has a mode size of 3.0 μm and the fiber  140  has a mode size of 9.0 μm. 
       FIG. 2  is a schematic diagram of a single-channel mode converter  200  according to an embodiment of the disclosure. The single-channel mode converter  200  is similar to the multi-channel mode converter  100  in  FIGS. 1A and 1B . Specifically, like the multi-channel mode converter  100 , the single-channel mode converter  200  comprises a lens  210 , a glass block  220 , and an FAU  230 . 
     However, unlike the lens array  110 , which comprises four lenses  165 , the lens  210  is a single lens. Unlike the FAU array  130 , which comprises four fibers  140 , the FAU  230  comprises one fiber  240 . The single-channel mode converter  200  is single-channel because it comprises one fiber  240 . The single-channel mode converter  200  has a width of about 1 mm-about 3 mm, a length of about 2 mm-about 5 mm when not including the fibers  240 , and a height of about 1 mm-about 3 mm. 
       FIG. 3A  is a mode converter manufacturing system  300  according to an embodiment of the disclosure. The mode converter manufacturing system  300  comprises a lens  310 , a glass block  315 , an FAU  320 , and a fiber  325  similar to the lens  210 , the glass block  220 , the FAU  230 , and the fiber  240 , respectively, in the single-channel mode converter  200  in  FIG. 2 . 
     In addition, the mode converter manufacturing system  300  comprises a reflector  305 , a coupler  330 , a light source  335 , and a power meter  340 . Alternatively, the coupler  330  is a circulator. The light source  335  and the power meter  340  are coupled to the coupler  330  via fibers or other suitable media. The light source  335  is a laser, an LED, or another suitable light source. 
       FIG. 3B  is a flowchart illustrating a mode converter manufacturing method  345  using the mode converter manufacturing system  300  in  FIG. 3A  according to an embodiment of the disclosure. A manufacturer implements the mode converter manufacturing method  345 . At step  350 , the manufacturer couples components. For instance, the manufacturer couples the reflector  305  to the lens  310  to form a lens assembly and couples the coupler  330  to the fiber  325 , the light source  335  to the coupler  330 , and the power meter  340  to the coupler  330  to form an FAU assembly. 
     At step  355 , the lens assembly and the glass block  315  are placed at an end of the FAU assembly. For instance, the end is opposite the fiber  325 . The manufacturer places the lens assembly and the glass block  315  such that light paths of the lens  310  and the glass block  315  align with a light path of the FAU  320 . 
     At step  360 , the light source  335  is caused to emit a light beam into the coupler  330 . For instance, a laser is powered on and emits a continuous, highly-collimated light beam incident to the coupler  330 . The light beam passes through the coupler  330 , the fiber  325  in the FAU  320 , the glass block  315 , and the lens  310 , then reflects off of the reflector  305  as a reflected light beam. The reflected light beam is therefore associated with the incident light beam. The reflected light beam passes through the lens  310 , the glass block  315 , the fiber  325  in the FAU  320 , and the coupler  330 , then enters the power meter  340 . 
     At step  365 , a power of the reflected light beam is measured using the power meter  340 . At step  370 , the manufacturer aligns the lens assembly and the FAU assembly until the power is greatest or aligns the lens assembly and the FAU assembly to achieve a maximum measured power. The power is greatest when light paths of the lens  310  and the FAU  320  align. When the lens  310  is a lens array comprising multiple lenses like the lens array  110  in  FIGS. 1A and 1B , the manufacturer need align only the two lenses on the ends of the lens  310 . The process of measuring the power and aligning the components based on that measuring is referred to as “active alignment”. 
     At step  375 , the glass block  315  is secured to the lens assembly and the FAU assembly to the glass block  315 . The manufacturer does so using an optical epoxy or another suitable bonding material. Alternatively, the manufacturer does so using another suitable bonding method. 
     At step  380 , the reflector  305 , the coupler  330 , the light source  335 , and the power meter  340  are removed. Finally, at step  385 , the manufacturer completes remaining manufacturing steps. Those steps may include testing the components. Although the mode converter manufacturing method  345  uses the mode converter manufacturing system  300 , which comprises a single channel, the same principles apply to a mode converter manufacturing system comprising multiple channels. 
       FIG. 4  is a schematic diagram of a single-channel mode converter  400  according to another embodiment of the disclosure. The single-channel mode converter  400  is similar to the single-channel mode converter  200  in  FIG. 2 . Specifically, like the single-channel mode converter  200 , the single-channel mode converter  400  comprises a lens  410 , a glass block  420 , and a fiber  440 . 
     However, instead of the FAU  230  in the single-channel mode converter  200 , the single-channel mode converter  400  comprises a glass capillary block  430 . The glass capillary block  430  has a composition comprising glass. The glass capillary block  430  has a width of about 1 mm-about 3 mm, a length of about 2 mm-about 5 mm, and a height of about 1 mm-about 3 mm. The glass capillary block  430  comprises a glass capillary that runs along the length of the glass capillary block  430 . The diameter of the glass capillary is the same as the diameter of the fiber  440  so that the fiber  440  may be plugged into the glass capillary block  430 . The glass capillary block  430  provides a cost-effective alternative to the FAU  230 . 
       FIG. 5  is a schematic diagram of a single-channel mode converter system  500  according to an embodiment of the disclosure. The single-channel mode converter system  500  comprises the single-channel mode converter  200 . Alternatively, the single-channel mode converter system  500  comprises the single-channel mode converter  400 . The single-channel mode converter system  500  further comprises a waveguide block  510 . 
     The waveguide block  510  has a composition comprising silicon and may be referred to as an silicon on insulator (SOI) block. The waveguide block  510  is transparent to show that it comprises a waveguide  520 . The waveguide  520  guides a light beam into the waveguide block  510 . 
     A manufacturer aligns the waveguide  520  and the single-channel mode converter  200 . The manufacturer then bonds the waveguide block  510  and the single-channel mode converter  200  using an optical epoxy, or another suitable bonding material. The bonding material should fill a gap between the waveguide block  510  and the single-channel mode converter  200 . The gap is about 10 μm-30 μm, which provides improved mechanical bonding strength and thus reliability. 
       FIG. 6  is a schematic diagram of a multi-channel mode converter system  600  according to an embodiment of the disclosure. The multi-channel mode converter system  600  is similar to the single-channel mode converter system  500  in  FIG. 5 . Specifically, like the single-channel mode converter system  500 , the multi-channel mode converter system  600  comprises a waveguide block  610 . 
     However, unlike the waveguide block  510 , which comprises a single waveguide  520 , the waveguide block  610  comprises four waveguides  620 . A manufacturer need align only the two waveguides  620  on the ends of the waveguide block  610 . Alternatively, the waveguide block  610  comprises two, three, or more than four waveguides  620 . Unlike the single-channel mode converter system  500 , which comprises the single-channel mode converter  200 , the mode converter system  600  comprises the multi-channel mode converter  100 . 
       FIG. 7  is a schematic diagram of a multi-channel mode converter system  700  according to another embodiment of the disclosure. The multi-channel mode converter system  700  is similar to the multi-channel mode converter system  600  in  FIG. 6 . Specifically, like the multi-channel mode converter system  600 , the multi-channel mode converter system  700  comprises a waveguide block  710  and the mode converter  100 . In addition, like the waveguide block  610 , which comprises the waveguides  620 , the waveguide block  710  comprises waveguides  720 . 
     However, unlike the waveguides  620 , which are straight with respect to a length of the waveguide block  610 , the waveguides  720  are angled with respect to a length of the waveguide block  710 . The waveguides  720  are angled at an angle ϕ, which is about 2°-15°. The angling of the waveguides  720  reduces or eliminates back reflection of light beams at an interface between the waveguide block  710  and the lens array  110 . To match the angling of the waveguides  720 , the FAU  130  is offset from centers of lenses in the lens array  110  to produce angled light beams in a manner similar to that shown in  FIG. 1D . The offset obviates the need to angle the FAU  130  in the same direction as the waveguides  720 , which simplifies an assembly process. 
     A multi-channel mode converter comprises: a lens array element comprising: a first lens element, and a second lens element; a glass block element coupled to the lens array element; and an FAU array element coupled to the glass block element and comprising: a first fiber element corresponding to the first lens element, and a second fiber element corresponding to the second lens element. 
     The term “about” means a range including ±10% of the subsequent number unless otherwise stated. While several embodiments have been provided in the present disclosure, it may be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. 
     In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, components, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled may be directly coupled or may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and may be made without departing from the spirit and scope disclosed herein.