Patent Publication Number: US-10313045-B2

Title: Wavelength-division multiplexing optical assembly with increased lane density

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Application Ser. No. 62/453,643, filed Feb. 2, 2017, U.S. Provisional Application Ser. No. 62/461,532, filed Feb. 21, 2017, and U.S. Provisional Application Ser. No. 62/461,521, filed Feb. 21, 2017, the content of each of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The disclosure relates generally to wavelength-division multiplexing (WDM) and demultiplexing, and more particularly, to WDM optical assemblies with increased lane density using a WDM filter having a passband in optical communication with two different WDM common ports. 
     Wavelength-division multiplexing (WDM) is a technology that multiplexes (e.g., adds) a number of distinct wavelengths of light onto a single optical fiber and demultiplexes (e.g., divides) a number of distinct wavelengths of light from a single optical fiber, thereby increasing information capacity and enabling bi-directional flow of signals. Multiple optical signals are multiplexed with different wavelengths of light combined by a multiplexer at a transmitter, directed to a single fiber for transmission of the signal, and split by a demultiplexer to designated channels at a receiver. By combining multiple channels of light into a single channel, WDM assemblies and associated devices can be used as components in an optical network, such as a passive optical network (PON). 
       FIG. 1A  is a perspective view of a typical WDM optical core subassembly  100 . In particular, the WDM optical core subassembly  100  comprises a single WDM common port  102  in optical communication with four WDM channel ports  104 A- 104 D by a plurality of WDM filters  106 A- 106 D, each having a width (W 1 ), and a mirror  108  mounted to a substrate  110 . The WDM optical core subassembly  100  positions all of the WDM filters  106 A- 106 D and the mirror  108  on one surface of the substrate  110 . The WDM filters  106 A- 106 D and the mirror  108  are arranged to form an optical path  112  between the common port  102  and each of the four channel ports  104 A- 104 D. In particular, each of the WDM filters  106 A- 106 D has a unique passband to allow a portion of the optical signal to pass through the WDM filter  106 A- 106 D and to reflect the remaining portion of the optical signal towards the mirror  108 , which in turn reflects the remaining portion of the optical signal towards another one of the remaining WDM filters  106 B- 106 D. 
       FIG. 1B  is a perspective view of a WDM optical assembly  114 . The WDM optical assembly  114  includes a WDM optical core subassembly  116  with a common collimator  118  and four channel collimators  120 A- 120 D. The WDM optical core subassembly  116  includes a plurality of WDM filters  106 A- 106 D positioned on opposing sides of a substrate  122  (WDM filter  106 B is located on a bottom side of the substrate  122  and is not visible in  FIG. 1B ). The WDM optical core subassembly  116  further includes a trapezoidal-shaped prism  124  for routing an optical signal between upper and lower sides of the substrate  122  as the optical signal is directed between the plurality of WDM filters  106 A- 106 D (WDM filter  106 B is located on a bottom side of the substrate  122  and is not visible in  FIG. 1B ). However, in each of the WDM optical core assemblies  100 ,  114  of  FIGS. 1A-1B , the WDM filters  106 A- 106 D are in optical communication with a single WDM common port (e.g., a single common collimator  118 ). 
     One of the components in an optical network that utilizes a WDM assembly is a transceiver (e.g., pluggable transceiver), such as a quad small form-factor pluggable (QSFP) transceiver for example. In particular, a QSFP transceiver interfaces networking hardware to a network connection (e.g., fiber optic cable or electrical copper connection). The QSFP has a form factor and electrical interface specified by a multi-source agreement. Accordingly, a QSFP transceiver must meet certain dimension requirements in order to properly interface with other components. 
     No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents. 
     SUMMARY 
     The disclosure relates generally to wavelength-division multiplexing and demultiplexing, and more particularly, to a wavelength-division multiplexing (WDM) optical core subassembly with increased lane density using a WDM filter having a passband in optical communication with two different common ports. In exemplary aspects disclosed herein, the WDM optical core subassembly, and corresponding WDM optical assembly, includes an optical signal router for routing an optical signal between a first side and a second side of a substrate. The WDM optical core subassembly further includes a first WDM filter having a first passband and a second WDM filter having a second passband. The WDM optical core subassembly forms a first optical path between a first common port, the first WDM filter, and a first channel port, and to form a second optical path between the second WDM filter, a second common port, and a second channel port. The WDM optical core subassembly increases lane density while decreasing size and complexity by including a plurality of common ports in optical communication with the same plurality of WDM filters (e.g., same passbands). In particular, in certain embodiments, the WDM optical core subassembly includes four WDM common ports, each in optical communication with four WDM channel ports (e.g., sixteen channel collimators) and four WDM filters. 
     One embodiment of the disclosure relates to a wavelength-division multiplexing (WDM) optical assembly, comprising an optical signal router, a first WDM filter having a first passband, a first common port, a first channel port, a first optical path, a second common port, a second channel port, and a second optical path. The first common port is configured for optical communication of a first multiplexed signal. The first channel port is configured for optical communication of a first demultiplexed signal. The first multiplexed signal comprises the first demultiplexed signal. The first optical path comprises the optical signal router, the first WDM filter, the first common port, and the first channel port. The second common port is configured for optical communication of a second multiplexed signal. The second channel port is configured for optical communication of a second demultiplexed signal. The second multiplexed signal comprises the second demultiplexed signal. The second optical path comprises the optical signal router, the first WDM filter, the second common port, and the second channel port. 
     An additional embodiment of the disclosure relates to a wavelength-division multiplexing (WDM) optical assembly, comprising a first WDM filter having a first passband, a second WDM filter having a second passband, a first common port, a second common port, a first optical path, and a second optical path. The first common port is configured for optical communication of a first multiplexed signal. The second common port is configured for optical communication of a second multiplexed signal. The first optical path comprises the optical signal router, the first WDM filter, the second WDM filter, and the first common port. The second optical path comprises the optical signal router, the first WDM filter, the second WDM filter, and the second common port. 
     An additional embodiment of the disclosure relates to a method of manufacturing a wavelength-division multiplexing (WDM) optical assembly. The method comprises positioning a first set common port relative to the optical signal router, the first set common port configured for optical communication of a first multiplexed signal. The method further comprises positioning a first set first channel port relative to the optical signal router, the first set first channel port configured for optical communication of a first demultiplexed signal, the first multiplexed signal comprising the first demultiplexed signal. The method further comprises forming a first optical path comprising the optical signal router, the first WDM filter, the first set common port, and the first set first channel port. The method further comprises positioning a second set common port relative to the optical signal router, the second set common port configured for optical communication of a second multiplexed signal. The method further comprises positioning a second set first channel port relative to the optical signal router, the second set first channel port configured for optical communication of a second demultiplexed signal, the second multiplexed signal comprising the second demultiplexed signal. The method further comprises forming a second optical path comprising the optical signal router, the first WDM filter, the second set common port, and the second set first channel port. 
     An additional embodiment of the disclosure relates to a method of manufacturing a wavelength-division multiplexing (WDM) optical assembly. The method comprises positioning a first WDM filter having a first passband relative to an optical signal router. The method further comprises positioning a second WDM filter having a second passband relative to the optical signal router. The method further comprises positioning a first common port relative to the optical signal router, the first common port configured for optical communication of a first multiplexed signal. The method further comprises positioning a second common port relative to the optical signal router, the second common port configured for optical communication of a second multiplexed signal. The method further comprises forming a first optical path comprising the optical signal router, the first WDM filter, the second WDM filter, and the first common port. The method further comprises forming a second optical path comprising the optical signal router, the first WDM filter, the second WDM filter, and the second common port. 
     An additional embodiment of the disclosure relates to a wavelength-division multiplexing (WDM) device, comprising a housing, a first common collimator, a first common fiber optic pigtail, a second common collimator, a second common fiber optic pigtail, a first channel collimator, a first channel fiber optic pigtail, a second channel collimator, a second channel fiber optic pigtail, and a wavelength-division multiplexing (WDM) optical assembly. The first common collimator is positioned within the housing and is configured for optical communication of a first multiplexed signal. The first common fiber optic pigtail is operatively coupled to the first common collimator and extends from the housing. The second common collimator is positioned within the housing and is configured for optical communication of a second multiplexed signal. The second common fiber optic pigtail is operatively coupled to the second common collimator and extends from the housing. The first channel collimator is positioned within the housing and is configured for optical communication of a first demultiplexed signal. The first channel fiber optic pigtail is operatively coupled to the first channel collimator and extends from the housing. The second channel collimator is positioned within the housing and is configured for optical communication of a second demultiplexed signal. The second channel fiber optic pigtail is operatively coupled to the second channel collimator and extends from the housing. The WDM optical assembly is positioned within the housing. The WDM optical assembly comprises an optical signal router, a first WDM filter having a first passband, a first optical path, and a second optical path. The first optical path comprises the optical signal router, the first WDM filter, the first common collimator, and the first channel collimator. The second optical path comprises the optical signal router, the first WDM filter, the second common collimator, and the second channel collimator. 
     An additional embodiment of the disclosure relates to a transceiver, comprising a housing, a first common collimator, a second common collimator, a first channel collimator, a second channel collimator, and a wavelength-division multiplexing (WDM) optical assembly. The first common collimator is positioned within the housing and is configured for optical communication of a first multiplexed signal. The second common collimator is positioned within the housing and is configured for optical communication of a second multiplexed signal. The first channel collimator is positioned within the housing and is configured for optical communication of a first demultiplexed signal. The second channel collimator is positioned within the housing and is configured for optical communication of a second demultiplexed signal. The WDM optical assembly is positioned within the housing. The WDM optical assembly comprises an optical signal router, and a first WDM filter having a first passband. The first WDM filter is optically positioned relative to the optical signal router to form a first optical path between the first common collimator and the first channel collimator, and a second optical path between the second common collimator and the second channel collimator. 
     An additional embodiment of the disclosure relates to a wavelength-division multiplexing (WDM) optical assembly comprising an optical signal router and a first WDM filter having a first passband. The first WDM filter is optically positioned relative to the optical signal router to form a first optical path and a second optical path. The first optical path is between a first common port configured for optical communication of a first multiplexed signal and a first channel port configured for optical communication of a first demultiplexed signal. The first multiplexed signal comprises the first demultiplexed signal. The second optical path is between a second common port configured for optical communication of a second multiplexed signal and a second channel port configured for optical communication of a second demultiplexed signal. The second multiplexed signal comprises the second demultiplexed signal. 
     An additional embodiment of the disclosure relates to a wavelength-division multiplexing (WDM) optical assembly comprising an optical signal router, a first WDM filter having a first passband, and a second WDM filter having a second passband. The first WDM filter is optically positioned relative to the optical signal router. The second WDM filter is optically positioned relative to the optical signal router. Each of the first and second WDM filters are configured to cooperate with the optical signal router to form (i) a first optical path routed between the first WDM filter, the second WDM filter, and a first common port configured for optical communication of a first multiplexed signal, and (ii) a second optical path routed between the first WDM filter, the second WDM filter, and a second common port configured for optical communication of a second multiplexed signal, wherein the second common port differs from the first common port. 
     Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. 
     The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an exemplary perspective view of a typical WDM optical core subassembly; 
         FIG. 1B  is an exemplary perspective view of a typical WDM optical assembly; 
         FIG. 2A  is a perspective view of an exemplary WDM optical core subassembly with increased lane density, according to an embodiment of the present disclosure; 
         FIG. 2B  is a perspective view of an exemplary WDM optical assembly with increased lane density, and wherein the WDM optical assembly includes the WDM optical core subassembly of  FIG. 2A ; 
         FIG. 3A  is a perspective view of an exemplary transceiver that includes the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B ; 
         FIG. 3B  is a perspective view of an exemplary WDM device that includes the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B ; 
         FIG. 3C  is a perspective view of another exemplary WDM device that includes the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B ; 
         FIG. 3D  is a perspective view of exemplary components of WDM devices of  FIGS. 3B-3C ; 
         FIG. 4A  is a front perspective view of the optical core subassembly of  FIG. 2A ; 
         FIG. 4B  is a top view of the optical core subassembly of  FIG. 4A  illustrating a first optical path between a first common port of a first WDM port set and four channel ports of the first WDM port set; 
         FIG. 4C  is a top view of the optical core subassembly of  FIG. 4A  illustrating a second optical path between a second common port of a second WDM port set and four channel ports of the second WDM port set; 
         FIG. 4D  is a top view of the optical core subassembly of  FIG. 4A  illustrating a third optical path between a third common port of a third WDM port set and four channel ports of the third WDM port set; 
         FIG. 4E  is a top view of the optical core subassembly of  FIG. 4A  illustrating a fourth optical path between a fourth common port of a fourth WDM port set and four channel ports of the fourth WDM port set; 
         FIG. 5A  is a back perspective view of another exemplary embodiment of the optical core subassembly of  FIGS. 2A and 4A-4E ; 
         FIG. 5B  is a top view of the optical core subassembly of  FIG. 5A  illustrating a first optical path between a first common port of a first WDM port set and four channel ports of the first WDM port set; 
         FIG. 5C  is a top view of the optical core subassembly of  FIG. 5B  illustrating a second optical path between a second common port of a second WDM port set and four channel ports of the second WDM port set; 
         FIG. 5D  is a top view of the optical core subassembly of  FIG. 5C  illustrating a third optical path between a third common port of a third WDM port set and four channel ports of the third WDM port set; 
         FIG. 5E  is a top view of the optical core subassembly of  FIG. 5D  illustrating a fourth optical path between a fourth common port of a fourth WDM port set and four channel ports of the fourth WDM port set; 
         FIG. 6A  is a top view of another exemplary embodiment of the WDM optical assembly of  FIG. 2B  incorporating the WDM optical core subassembly of  FIGS. 4A-4E  and illustrating a first optical path between a first common optical collimator of a first WDM collimator set and four channel collimators of the first WDM collimator set; 
         FIG. 6B  is a bottom view of the WDM optical assembly of  FIG. 6A ; 
         FIG. 7A  is a front perspective view of another exemplary embodiment of the WDM optical assembly of  FIGS. 6A-6B  including a channel port router to decrease depth of the WDM optical assembly, the channel port router including a plurality of pentagonal-shaped prisms; 
         FIG. 7B  is a front perspective view of the pentagonal-shaped prism of  FIG. 7A ; 
         FIG. 7C  is a top view of the pentagonal-shaped prism of  FIG. 7A ; 
         FIG. 7D  is a top view of the WDM optical assembly of  FIG. 7A  illustrating a first optical path between a first common optical collimator of the first WDM collimator set and four channel collimators of the first WDM collimator set; 
         FIG. 7E  is a bottom view of the WDM optical assembly of  FIG. 7B ; 
         FIG. 8A  is a front perspective view of another embodiment of the optical assembly of  FIGS. 6A-7C  including another exemplary embodiment of the channel port router of  FIGS. 7A-7C , the channel port router including a plurality of octagonal-shaped prisms; 
         FIG. 8B  is a front perspective view of the upper octagonal-shaped prism of the optical assembly of  FIG. 8A ; 
         FIG. 8C  is a side view of the WDM optical assembly of  FIG. 8A ; 
         FIG. 8D  is a top view of the WDM optical assembly of  FIG. 8A  illustrating a first optical path between a first common optical collimator of the first WDM collimator set and four channel collimators of the first WDM collimator set; 
         FIG. 8E  is a bottom view of the WDM optical assembly of  FIG. 8A ; 
         FIG. 9A  is a top perspective view of another exemplary embodiment of the optical assembly of  FIGS. 6A-6B  including a mirror positioned between a first common optical collimator and a second common optical collimator on an upper side of a substrate, and illustrating a first optical path between the first common optical collimator of the first WDM collimator set and four channel collimators of the first WDM collimator set; 
         FIG. 9B  is a bottom perspective view of the optical assembly of  FIG. 9A ; 
         FIG. 9C  is a top view of the optical assembly of  FIG. 9A ; 
         FIG. 9D  is a bottom view of the optical assembly of  FIG. 9A ; 
         FIG. 9E  is a top perspective view of the optical assembly of  FIG. 9A  illustrating a second optical path between a second common optical collimator of the second WDM collimator set and four channel collimators of the second WDM collimator set; 
         FIG. 9F  is a bottom perspective view of the optical assembly of  FIG. 9E ; 
         FIG. 9G  is a top view of the optical assembly of  FIG. 9E ; 
         FIG. 9H  is a bottom view of the optical assembly of  FIG. 9E ; 
         FIG. 10A  is a perspective view of the WDM device of  FIG. 2B ; 
         FIG. 10B  is a top view of the WDM device of  FIG. 10A  illustrating a first optical path between a first common optical collimator of the first WDM collimator set and four channel collimators of the first WDM collimator set; 
         FIG. 11  is a perspective view of a steel-tube collimator for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B ; 
         FIG. 12A  is a perspective view of a square tube collimator for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B ; 
         FIG. 12B  is a cross-sectional side view of the square tube collimator of  FIG. 12A ; 
         FIG. 13A  is a perspective view of a compact collimator for use with the WDM optical core assemblies and/or WDM device of  FIGS. 2A-10B ; 
         FIG. 13B  is a side view of the compact collimator of  FIG. 13A ; 
         FIG. 14A  is a perspective view of an array of the compact collimators of  FIGS. 13A-13B ; 
         FIG. 14B  is a front view of the array of compact collimators of  FIG. 14A ; 
         FIG. 15  is a perspective view of another exemplary embodiment of a fiber array unit (FAU) for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B ; and 
         FIG. 16  is a flowchart illustrating an exemplary process that can be employed to manufacture a WDM optical core subassembly of  FIGS. 2A-10B . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     The disclosure relates generally to wavelength-division multiplexing and demultiplexing, and more particularly, to a wavelength-division multiplexing (WDM) optical core subassembly with increased lane density using a WDM filter having a passband in optical communication with two different common ports. In exemplary aspects disclosed herein, the WDM optical core subassembly, and corresponding WDM optical assembly, includes an optical signal router for routing an optical signal between a first side and a second side of a substrate. The WDM optical core subassembly further includes a first WDM filter having a first passband and a second WDM filter having a second passband. The WDM optical core subassembly forms a first optical path between a first common port, the first WDM filter, and a first channel port, and to form a second optical path between the second WDM filter, a second common port, and a second channel port. The WDM optical core subassembly increases lane density while decreasing size and complexity by including a plurality of common ports in optical communication with the same plurality of WDM filters (e.g., same passbands). In particular, in certain embodiments, the WDM optical core subassembly includes four WDM common ports, each in optical communication with four WDM channel ports (e.g., sixteen channel collimators) and four WDM filters. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. 
     There is increasing demand for greater bandwidth, driving the telecommunications industry toward increasing the number of wavelength channels. Adding to this trend, the dimensions of the optical transceivers are decreasing, requiring increasingly smaller WDM assemblies to keep the size of the WDM device as small as possible. For example, there is a desire to increase the number of channels of a WDM device within a quad small form-factor pluggable (QSFP) transceiver while maintaining the same form factor of the QSFP transceiver. In other words, there is a desire to increase the lane density of WDM devices. 
       FIG. 2A  is a perspective view of an exemplary WDM optical core subassembly  200  for bidirectional multiplexing and/or demultiplexing of optical signals. The WDM optical core subassembly  200  (also referred to as a WDM optical core assembly, optical core subassembly, optical core assembly, etc.) includes a substrate  202  having a first, upper side  204 A and a second, lower side  204 B. Directional terms, such as “top,” “bottom,” “upper,” “lower,” “left,” “right,” “medial,” “distal,” etc. are used for non-limiting illustrative purposes only. The WDM optical core subassembly  200  further includes an optical signal router  206  for routing an optical signal between the upper side  204 A and the lower side  204 B of the substrate  202 . The WDM optical core subassembly  200  further includes a first WDM filter  208 A having a first passband positioned on the upper side  204 A of the substrate  202  towards a first side (also referred to as a left side) of the substrate  202  and/or optical signal router  206 , a second WDM filter  208 B having a second passband positioned on a lower side  204 B of the substrate  202  towards the left side of the substrate  202  and/or optical signal router  206 , a third WDM filter  208 C having a third passband positioned on the upper side  204 A of the substrate  202  towards a second side (also referred to as a right side) of the substrate  202  and/or optical signal router  206 , and a fourth WDM filter  208 D having a fourth passband positioned on a lower side  204 B of the substrate  202  towards the right side of the substrate  202  and/or optical signal router  206 . As explained in more detail below, the WDM filters  208 A- 208 D are positioned relative to the optical signal router  206  to increase lane density while decreasing size and minimizing complexity (e.g., fewer components) by forming multiple optical paths with multiple common ports as explained in more detail below. Lane density is directed to the number of ports in a multiplexer (e.g., demultiplexed ports). Increased lane density pertains to increasing the number of ports in a specified area, maintaining the number of ports in a smaller area, or increasing the number of ports and decreasing the area for the ports. As used herein, reference number ranges with the same ending letter include only those other numbers with the same ending letter. For example, 10A-14A would include 10A, 11A, 12A, 13A, 14A. However, reference number ranges with different ending letters include all numbers in that range with the same or different ending letter. For example, 10A-14B would include 10A, 10B, 11A, 11B, 12A, 12B, 13A, 13B, 14A, 14B. As explained in more detail below, the four WDM filters  208 A- 208 D provide four common ports and sixteen channels for a total of twenty ports by interleaving (e.g., overlapping) a plurality of optical paths from a plurality of common ports. 
       FIG. 2B  is a perspective view of an exemplary WDM optical assembly  210  including the WDM optical core subassembly  200  of  FIG. 2A  and a plurality of WDM port sets  212 A- 212 B (embodied as WDM collimator sets  214 A- 214 B) to transmit and receive multiplexed and/or demultiplexed optical signals. In particular, the first WDM port set  212 A (embodied as a first WDM collimator set  214 A) includes a first set WDM common port  216 A (embodied as a first set WDM common collimator  226 A), a first set first WDM channel port  218 A (embodied as a first set first WDM channel collimator  228 A), a first set second WDM channel port  220 A (embodied as a first set second WDM channel collimator  230 A), a first set third WDM channel port  222 A (embodied as a first set third WDM channel collimator  232 A), and a first set fourth WDM channel port  224 A (embodied as a first set fourth WDM channel collimator  234 A). The second WDM port set  212 B (embodied as a second WDM collimator set  214 B) includes a second set WDM common port  216 B (embodied as a second set WDM common collimator  226 B), a second set first WDM channel port  218 B (embodied as a second set first WDM channel collimator  228 B), a second set second WDM channel port  220 B (embodied as a second set second WDM channel collimator  230 B), a second set third WDM channel port  222 B (embodied as a second set third WDM channel collimator  232 B), and a second set fourth WDM channel port  224 B (embodied as a second set fourth WDM channel collimator  234 B). Each of the ports may include a light receiving element and/or light emitting element, such as a collimator, lens, fiber optic pigtail, fiber array unit, photodiode, laser diode, etc. 
     Accordingly, the WDM optical core subassembly  200  and/or WDM optical assembly  210  increases lane density while decreasing size and minimizing complexity by using a plurality of common ports  216 A- 216 B (embodied as a plurality of common collimators  226 A- 226 B), such as in optical communication with the same plurality of WDM filters  208 A- 208 D and accordingly, the same passbands. 
       FIG. 3A  is a perspective view of an exemplary transceiver  300  that includes the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B . The transceiver  300  is a device that can both transmit and receive signals (e.g., optical signals). The transceiver  300  could be any of a variety of sizes, forms, and/or configurations, such as a quad small form-factor pluggable (QSFP) transceiver (e.g., backward compatible). In certain embodiments, the transceiver  300  supports up to 400 Gb/s in aggregate over an 8×50 GB/s electrical interface. However, the transceiver  300  provides double density (e.g., eight lanes) and/or quadra density (e.g., sixteen lanes). Such a transceiver  300  may be hot-pluggable (where the transceiver  300  may be added or removed while the computer system is running) and may be used to interface networking hardware to a fiber optic cable or electrical connection, such as for transmitting and/or receiving multiplexed/demultiplexed signals between network components. The transceiver  300  includes both a transmitter and a receiver within a housing  302  (e.g., cage) with a plurality of ports  304  (e.g., electronic ports, optical ports, etc.) to interface with other network components. The housing  302  and/or ports  304  may provide backwards compatibility with other transceivers  300 , such as a QSFP28 module (e.g., which may be inserted into four of eight electrical lanes) or a CFP2/4/8 module. Further, the transceiver  300  may include a multiplexer (e.g., mux) and/or demultiplexer (e.g., demux) to multiplex and/or demultiplex communication signals (e.g., optical signals), such as by wavelength. The transceiver  300  may be backwards compatible. In particular, the transceiver  300  may include a transmitter optical sub-assembly (TOSA), a receiver optical sub-assembly (ROSA), and/or a bidirectional optical sub-assembly (BOSA). 
       FIG. 3B  is a perspective view of an exemplary WDM device  306  with a housing  308  containing the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B . Further, the WDM device  306  comprises a plurality of fiber optic pigtails  309  (e.g., first common fiber optic pigtail, second common fiber optic pigtail, first channel fiber optic pigtail, second channel fiber optic pigtail, etc.) operatively coupled to WDM ports and/or WDM collimators within the WDM device  306 .  FIG. 3C  is a perspective view of another exemplary WDM device  310  with a housing  312  containing the WDM optical core subassembly and/or WDM optical assembly of  FIGS. 2A-2B . Further, the WDM device  306  comprises a plurality of fiber optic pigtails  311  (e.g., first common fiber optic pigtail, second common fiber optic pigtail, first channel fiber optic pigtail, second channel fiber optic pigtail, etc.) operatively coupled to WDM ports and/or WDM collimators within the WDM device  306 . The housing  312  of the WDM device  310  may be narrower than the housing  308  of the WDM device  306 . The WDM devices  306 ,  310  are designed for multiwavelength network applications, and may be designed for uni-directional and/or bi-directional transmissions. The WDM devices  306 ,  310  may have a center wavelength (λ c ) between 1200 nm and 1700 nm (e.g., 1291 nm, 1311 nm, 1331 nm, 1351 nm, 1471 nm, 1491 nm, 1511 nm, 1531 nm, 1511 nm, 1531 nm, 1551 nm, 1571 nm, 1551 nm, 1571 nm, 1591 nm, 1611 nm, and/or combinations thereof). Further, the WDM devices  306 ,  310  may utilize any of a variety of connectors, such as LC/PC (Lucent connector/physical contact), FC/PC (fiber-optic connector/physical contact), FC/APC (fiber-optic connector/angled physical contact), SC/PC (standard connector/physical contact), SC/APC (standard connector/angled physical contact), MU/PC (miniature unit/physical contact), etc. The WDM devices  306 ,  310  could be any of a variety of sizes, forms, and/or configurations (e.g., bidirectional, epoxy-free optical path), and for a variety of applications (e.g., 40 G transceiver, 100 G transceiver, etc.). 
       FIG. 3D  is a perspective view of exemplary components of WDM devices of  FIGS. 3B-3C . More specifically, the components include a first set WDM common port  216 A (embodied as a receptacle interface  313 ), a plurality of channel ports  218 A- 224 A (embodied as a photodiode/laser diode (PD/LD) array  314 ), a unibody substrate  316  for mounting the components thereto, and an optical core subassembly  200 , including an optical signal router  206  for directing and routing multiplexed and demultiplexed optical signals, as discussed in more detail below. These components, as used herein, cooperate to form multiple optical paths between a plurality of common ports and a plurality of channel ports. 
       FIGS. 4A-4E  are views of the optical core subassembly  200  of  FIG. 2A  illustrating multiple optical paths  414 A- 414 D formed between the optical signal router  206  and the WDM filters  208 A- 208 D. As discussed above, the optical core subassembly  200  includes a substrate  202  with a first side  204 A (also referred to as an upper side, first surface, upper surface, etc.) and a second side  204 B (also referred to as a lower side, second side, second surface, lower surface, etc.) opposite the upper side  204 A. 
     In this exemplary embodiment, the optical signal router  206  includes a trapezoidal-shaped prism  400  horizontally positioned relative to the substrate  202  for routing optical signals between the upper side  204 A and the lower side  204 B of the substrate  202 . In particular, the trapezoidal-shaped prism  400  (also referred to as a trapezoidal-shaped prism) includes a first base  402 A (also referred to as a left base, etc.), and a second base  402 B (also referred to as a right base, etc.) opposite the first base  402 A. The first and second bases  402 A,  402 B are trapezoidal-shaped. The trapezoidal-shaped prism  400  further includes a plurality of faces  404 - 408 B (also referred to as surfaces) extending between the first base  402 A and the second base  402 B. At least a portion of the plurality of faces  404 - 408 B provide surfaces for entry and/or exit of an optical signal therein, and/or reflective surfaces for routing (e.g., redirecting, rerouting) an optical signal therein. In particular, the trapezoidal-shaped prism  400  further includes a narrow face  404  (also referred to as a front face), a broad face  406  (also referred to as a back face) opposite the narrow face  404 , an upper oblique face  408 A positioned between upper edges of the narrow face  404  and the broad face  406 , and a lower oblique face  408 B positioned between lower edges of the narrow face  404  and the broad face  406 . 
     The narrow face  404  acts as a chamfer and minimizes stress points, reducing damage (e.g., chipping) to the trapezoidal-shaped prism  400 . In this way, in this exemplary embodiment, a chamfer may be provided between the broad face  406  and the upper oblique face  408 A and/or between the broad face  406  and the lower oblique face  408 B. Further, the distance between the narrow face  404  and the broad face  406  (e.g., the height of the trapezoid) may be reduced as long as the optical path intersects the upper oblique face  408 A and/or the lower oblique face  408 B, such as to avoid the narrow face  404 . 
     In this exemplary embodiment, the broad face  406  is positioned approximately perpendicular to the substrate  202  with at least an upper portion  410 A of the broad face  406  extending above the upper side  204 A of the substrate  202  and at least a lower portion  410 B of the broad face  406  extending below the lower side  204 B of the substrate  202 . The upper portion  410 A and/or lower portions  410 B provides exit and/or entry points for an optical signal as explained in more detail below. The upper oblique face  408 A redirects signals between an upper portion  410 A of the broad face  406  and the lower oblique face  408 B, and similarly, the lower oblique face  408 B redirects signals between the lower portion  410 B of the broad face  406  and the upper oblique face  408 A. In this way, the optical signal is routed between upper and lower sides  204 A,  204 B of the substrate  202 . 
     As discussed above, the WDM optical core subassembly  200  includes WDM filters  208 A- 208 D. In particular, the first WDM filter  208 A includes a first WDM filter  208 A having a first passband positioned on the upper side  204 A of the substrate  202  towards a first side (also referred to as a left side), a second WDM filter  208 B having a second passband positioned on a lower side  204 B of the substrate  202  towards the left side, a third WDM filter  208 C having a third passband positioned on the upper side  204 A of the substrate  202  towards a second side (also referred to as a right side), and a fourth WDM filter  208 D having a fourth passband positioned on a lower side  204 B of the substrate  202  towards the right side. In this way, the first WDM filter  208 A is vertically aligned (e.g., along a common vertical axis A-A) with the second WDM filter  208 B, and the third WDM filter  208 C is vertically aligned (e.g., along a common vertical axis B-B) with the fourth WDM filter  208 D. In other words, the first WDM filter  208 A is aligned left to right and front to back with the second WDM filter  208 B, and the third WDM filter  208 C is aligned left to right and front to back with the fourth WDM filter  208 D. Further, the first WDM filter  208 A is horizontally aligned (e.g., along a common horizontal axis C-C) with the third WDM filter  208 C (along the upper side  204 A of the substrate  202 ), and the second WDM filter  208 B is horizontally aligned (e.g., along a common horizontal axis D-D) with the fourth WDM filter  208 D (along the lower side  204 B of the substrate  202 ). In other words, the first WDM filter  208 A is aligned front to back and/or upper to lower with the third WDM filter  208 C, and the second WDM filter  208 B is aligned front to back and/or upper to lower with the fourth WDM filter  208 D. Each WDM filter  208 A- 208 D may have a coating on at least one of the faces to form the passbands. Each passband is configured to allow a different wavelength to pass through. In particular, the first passband is configured for a first wavelength (λ 1 ), the second passband is configured for a second wavelength (λ 2 ), the third passband is configured for a third wavelength (λ 3 ), the fourth passband is configured for a fourth wavelength (λ 4 ), etc. 
     Each of the first, second, third, and fourth WDM filters  208 A- 208 D are offset from and generally parallel with the broad face  406  of the trapezoidal-shaped prism  400 , such as to receive an optical signal directly from one of the first, second, third, and/or fourth common ports  216 A- 216 D. The WDM filters  208 A- 208 D are each a rectangular prism with a left portion  412 A (also called a first area) disposed towards one end of the face and a right portion  412 B (also called a second area) disposed towards a second end of the face for interleaving multiple optical paths from multiple common ports as explained in more detail below. Each of the WDM filters  208 A- 208 D is configured and sized to receive at least a first optical signal from one of the common ports  216 A- 216 D at the left portion  412 A and to receive at least a second optical signal from a different one of the common ports  216 A- 216 D at the right portion  412 B. Accordingly, the WDM filters  208 A- 208 D may be twice the width (W 2 ) as the filters shown in  FIGS. 1A-1B . This increases the ease of manufacturing and assembly as the sizes of the WDM filters  208 A- 208 D are larger and also allows a decrease in pitch between lanes of the optical path as explained in more detail below. However, in certain embodiments, each of the WDM filters  208 A- 208 D may be split into two separate WDM filters, as opposed to, for example, one WDM filter with a left and right portions  412 A- 412 B. 
     Although the optical signal router  206  is shown in  FIGS. 4A-4E  as a trapezoidal-shaped prism  400 , other shapes may be used as explained in more detail below. In particular, in certain embodiments, the optical signal router  206  may be generally shaped as a prism (e.g., triangular prism, quadrilateral prism, trapezoidal-shaped prism, pentagonal prism, etc.), pyramid (e.g., frustopyramidal, triangular pyramid, rectangular pyramid, etc.), and/or any other polyhedron (e.g., prism, pyramid, etc.), as long as the optical signal router  206  includes an optical signal entry surface, an optical signal exit surface, a first optical signal redirecting surface, and/or a second optical signal redirecting surface. 
       FIGS. 4B-4E  are views of the optical core subassembly of  FIG. 4A  illustrating optical paths between a plurality of WDM port sets  212 A- 212 D. In particular, the optical core subassembly  200  provides four common ports  216 A- 216 D and sixteen channel ports  216 A- 224 D using four WDM filters  208 A (and four respective passbands). It is noted that the portions of optical paths  414 A- 414 D that are solid are on the upper side  204 A of the substrate  202 , and the portions of the optical paths  414 A- 414 D that are dashed are on the lower side  204 B of the substrate  202 . 
       FIG. 4B  is a top view of the optical core subassembly of  FIG. 4A  illustrating a first optical path between the first set WDM common port  216 A (also referred to as a first WDM common port, first common port, etc.) of the first WDM port set  212 A and the four channel ports  218 A- 224 A. The first set WDM common port  216 A forms a first optical path  414 A with each of the four channel ports  218 A- 224 A. The first optical path  414 A is also illustrated in  FIG. 4A . The first WDM port set  212 A includes the first set WDM common port  216 A positioned on an upper side  204 A of the substrate  202  towards a left side and towards a front side of the trapezoidal-shaped prism  400 . The first WDM port set  212 A further includes the first set first WDM channel port  218 A at an upper side  204 A of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , the first set second WDM channel port  220 A at a lower side  204 B of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , the first set third WDM channel port  222 A at an upper side  204 A of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , and the first set fourth WDM channel port  224 A at a lower side  204 B of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 . The first set WDM common port  216 A is angled (or configured to direct an optical signal at an angle) relative to a center plane E-E of the trapezoidal-shaped prism (and/or substrate  202 ). The channel ports  218 A- 224 A are similarly angled and/or configured as that of the first set WDM common port  216 A. Further, the trapezoidal-shaped prism  400  is positioned between the first set WDM common port  216 A and the channel ports  218 A- 224 A. 
     The WDM optical core subassembly  200  defines a first optical path  414 A including a first common lane  416 A, a lateral path  418 A, and a plurality of channel lanes  420 A- 426 A. The lateral path  418 A extends between an upper side  204 A of the substrate  202  and a lower side  204 B of the substrate  202  (and between an upper portion  410 A of the trapezoidal-shaped prism  400  and a lower portion  410 B of the trapezoidal-shaped prism  400 ) and from a left side to a right side of the substrate  202 . In particular, a first optical signal (wavelengths λ 1 -λ 4 ) extends along the first common lane  416 A of the first optical path  414 A from the first set WDM common port  216 A to the left portion  412 A of the first WDM filter  208 A. A portion of the first optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the first channel lane  420 A to the first set first WDM channel port  218 A. Any remaining portion of the first optical signal (wavelengths λ 2 -λ 4 ) is reflected off the left portion  412 A of the first WDM filter  208 A to the upper oblique face  408 A to the lower oblique face  408 B to the right portion  412 B of the second WDM filter  208 B. A portion of the remaining first optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the second channel lane  422 A to the first set second WDM channel port  220 A. Any remaining portion of the first optical signal (wavelengths λ 3 -λ 4 ) is reflected off the right portion  412 B of second WDM filter  208 B to the lower oblique face  408 B to the upper oblique face  408 A to the left portion  412 A of the third WDM filter  208 C. A portion of the remaining optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the third channel lane  424 A to the first set third WDM channel port  222 A. Any remaining portion of the first optical signal (wavelengths λ 4 ) is reflected off the left portion  412 A of the third WDM filter  208 C to the upper oblique face  408 A to the lower oblique face  408 B to the right portion  412 B of the fourth WDM filter  208 D. A portion of the remaining optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the fourth channel lane  426 A to the first set fourth WDM channel port  224 A. Any remaining portion of the first optical signal is reflected off the right portion  412 B of the fourth WDM filter  208 D. 
       FIG. 4C  is a top view of the optical core subassembly of  FIG. 4A  illustrating a second optical path between a second common port and four channel ports. The second set WDM common port  216 B (also referred to as a second WDM common port, second common port, etc.) forms a second optical path  414 B with each of the four channel ports  218 B- 224 B. The second WDM port set  212 B includes the second set WDM common port  216 B positioned on a lower side  204 B of the substrate  202  towards a left side and towards a front side of the trapezoidal-shaped prism  400 . The second WDM port set  212 B further includes a second set first WDM channel port  218 B at a lower side  204 B of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , a second set second WDM channel port  220 B at an upper side  204 A of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , a second set third WDM channel port  222 B at a lower side  204 B of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , and a second set fourth WDM channel port  224 B at an upper side  204 A of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 . The second set WDM common port  216 B is angled (or configured to direct an optical signal at an angle) relative to a center plane E-E of the trapezoidal-shaped prism (and/or substrate  202 ), the same (or similar) angle as the first set WDM common port  216 A. Accordingly, the first set WDM common port  216 A may be vertically aligned with the second set WDM common port  216 B. The channel ports  218 B- 224 B are similarly angled and/or configured as that of the second set WDM common port  216 B, the first set WDM common port  216 A, and/or the channel ports  218 A- 224 A. The channel ports on the upper side  204 A may be vertically aligned with the channel ports on the lower side  204 B. Further, the trapezoidal-shaped prism  400  is positioned between the second set WDM common port  216 B and the channel ports  218 B- 224 B. 
     Accordingly, the upper side  204 A of the substrate  202  includes (from left to right) the first set first WDM channel port  218 A of the first WDM port set  212 A (and corresponding first channel lane  420 A), the second set second WDM channel port  220 B of the second WDM port set  212 B (and corresponding second channel lane  422 B), the first set third WDM channel port  222 A of the first WDM port set  212 A (and corresponding third channel lane  424 A), and the first set fourth WDM channel port  224 A of the first WDM port set  212 A (and corresponding fourth channel lane  426 B). Similarly, the lower side  204 B of the substrate  202  includes (from left to right) the second set first WDM channel port  218 B of the second WDM port set  212 B (and corresponding first channel lane  420 B), the first set second WDM channel port  220 A of the first WDM port set  212 A (and corresponding second channel lane  422 A), the second set third WDM channel port  222 B of the second WDM port set  212 B (and corresponding third channel lane  424 B), and the first set fourth WDM channel port  224 A of the first WDM port set  212 A (and corresponding fourth channel lane  426 A). Accordingly, the upper side  204 A and lower side  204 B of the substrate include alternating common ports of the first WDM port set  212 A and the second WDM port set  212 B. 
     The WDM optical core subassembly  200  defines a second optical path  414 B including a second common lane  416 B, a lateral path  418 B, and a plurality of channel lanes  420 B- 426 B. The lateral path  418 B extends between an upper side  204 A of the substrate  202  and a lower side  204 B of the substrate  202  (and between an upper portion  410 A of the trapezoidal-shaped prism  400  and a lower portion  410 B of the trapezoidal-shaped prism  400 ) and from a left side to a right side of the substrate  202 . In particular, a second optical signal (wavelengths λ 1 -λ 4 ) extends along the second common lane  416 B of the second optical path  414 B from the second set WDM common port  216 B to the left portion  412 A of the second WDM filter  208 B. A portion of the second optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the first channel lane  420 B to the second set first WDM channel port  218 B. Any remaining portion of the second optical signal (wavelengths λ 1  and λ 3 -λ 4 ) is reflected off the left portion  412 A of the second WDM filter  208 B to the lower oblique face  408 B to the upper oblique face  408 A to the right portion  412 B of the first WDM filter  208 A. A portion of the remaining first optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the second channel lane  422 B to the second set second WDM channel port  220 B. Any remaining portion of the first optical signal (wavelengths λ 3 -λ 4 ) is reflected off the right portion  412 B of first WDM filter  208 A to the upper oblique face  408 A to the lower oblique face  408 B to the left portion  412 A of the fourth WDM filter  208 D. A portion of the remaining optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the third channel lane  424 B to the second set third WDM channel port  222 B. Any remaining portion of the first optical signal (wavelengths λ 3 ) is reflected off the left portion  412 A of the fourth WDM filter  208 D to the lower oblique face  408 B to the upper oblique face  408 A to the right portion  412 B of the third WDM filter  208 C. A portion of the remaining optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the fourth channel lane  426 B to the second set fourth WDM channel port  224 B. Any remaining portion of the first optical signal is reflected off the right portion  412 B of the third WDM filter  208 C. 
       FIG. 4D  is a top view of the optical core subassembly of  FIG. 4A  illustrating a third optical path between a third common port and four channel ports. The third common port  216 C (also referred to as a third WDM common port, third common port, etc.) forms a third optical path  414 C with each of the four channel ports  218 C- 224 C. The third WDM port set  212 C includes the third common port  216 C positioned on an upper side  204 A of the substrate  202  towards a right side and towards a front side of the trapezoidal-shaped prism  400 . The third WDM port set  212 C further includes a third set first channel port  218 C at an upper side  204 A of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , a third set second channel port  220 C at a lower side  204 B of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , a third set third channel port  222 C at an upper side  204 A of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , and a third set fourth channel port  224 C at a lower side  204 B of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 . The third common port  216 C is angled (or configured to direct an optical signal at an angle) relative to a center plane E-E of the trapezoidal-shaped prism (and/or substrate  202 ). The channel ports  218 C- 224 C are similarly angled and/or configured as that of the third common port  216 C (and opposite to the first set WDM common port  216 A, second set WDM common port  216 B, channel ports  218 A- 224 A, and/or channel ports  218 B- 224 B). Further, the trapezoidal-shaped prism  400  is positioned between the third common port  216 C and the channel ports  218 C- 224 C. 
     The WDM optical core subassembly  200  defines a third optical path  414 C including a first common lane  416 C, a lateral path  418 C, and a plurality of channel lanes  420 C- 426 C. The lateral path  418 C extends between an upper side  204 A of the substrate  202  and a lower side  204 B of the substrate  202  (and between an upper portion  410 A of the trapezoidal-shaped prism  400  and a lower portion  410 B of the trapezoidal-shaped prism  400 ) and from a right side to a left side of the substrate  202 . In particular, a third optical signal (wavelengths λ 1 -λ 4 ) extends along the first common lane  416 C of the third optical path  414 C from the third common port  216 C to the right portion  412 B of the third WDM filter  208 C. A portion of the first optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the first channel lane  420 C to the first channel port  218 C. Any remaining portion of the first optical signal (wavelengths λ 1 -λ 2  and λ 4 ) is reflected off the right portion  412 B of the third WDM filter  208 C to the upper oblique face  408 A to the lower oblique face  408 B to the left portion  412 A of the fourth WDM filter  208 D. A portion of the remaining first optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the second channel lane  422 C to the second channel port  220 C. Any remaining portion of the first optical signal (wavelengths λ 1 -λ 2 ) is reflected off the left portion  412 A of second WDM filter  208 B to the lower oblique face  408 B to the upper oblique face  408 A to the right portion  412 B of the first WDM filter  208 A. A portion of the remaining optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the third channel lane  424 C to the third channel port  222 C. Any remaining portion of the first optical signal (wavelengths λ 2 ) is reflected off the right portion  412 B of the first WDM filter  208 A to the upper oblique face  408 A to the lower oblique face  408 B to the left portion  412 A of the second WDM filter  208 B. A portion of the remaining optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the fourth channel lane  426 D to the fourth channel port  224 D. Any remaining portion of the third optical signal is reflected off the left portion  412 A of the second WDM filter  208 B. 
       FIG. 4E  is a top view of the optical core subassembly of  FIG. 4A  illustrating a fourth optical path between a fourth common port and four channel ports. The fourth common port  216 D (also referred to as a fourth WDM common port, fourth common port, etc.) forms a fourth optical path  414 D with each of the four channel ports  218 D- 224 D. The fourth WDM port set  212 D includes the fourth common port  216 D positioned on a lower side  204 B of the substrate  202  towards a right side and towards a front side of the trapezoidal-shaped prism  400 . The fourth WDM port set  212 D further includes a fourth set first channel port  218 D at a lower side  204 B of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , a fourth set second channel port  220 D at an upper side  204 A of the substrate  202  towards the right side of the trapezoidal-shaped prism  400 , a fourth set third channel port  222 D at a lower side  204 B of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 , and a fourth set fourth channel port  224 D at an upper side  204 A of the substrate  202  towards the left side of the trapezoidal-shaped prism  400 . The fourth common port  216 D is angled (or configured to direct an optical signal at an angle) relative to a center plane E-E of the trapezoidal-shaped prism (and/or substrate  202 ), the same (or similar) angle as the third common port  216 C. Accordingly, the fourth common port  216 D may be vertically aligned with the third common port  216 C. The channel ports  218 D- 224 D are similarly angled and/or configured as that of the fourth common port  216 D, the third common port  216 C, and/or the channel ports  218 C- 224 C. The channel ports on the upper side  204 A may be vertically aligned with the channel ports on the lower side  204 B. Further, the trapezoidal-shaped prism  400  is positioned between the fourth common port  216 D and the channel ports  218 D- 224 D. 
     Accordingly, the upper side  204 A of the substrate  202  includes (from right to left) the first channel port  218 C of the third WDM port set  212 C (and corresponding first channel lane  420 C), the second channel port  220 D of the fourth WDM port set  212 D (and corresponding second channel lane  422 D), the third channel port  222 C of the third WDM port set  212 C (and corresponding third channel lane  424 C), the fourth channel port  224 D of the fourth WDM port set  212 D (and corresponding fourth channel lane  426 D). Similarly, the lower side the lower side  204 B of the substrate  202  includes (from right to left) the first channel port  218 D of the fourth WDM port set  212 D (and corresponding first channel lane  420 D), the second channel port  220 C of the third WDM port set  212 C (and corresponding second channel lane  422 C), the third channel port  222 D of the fourth WDM port set  212 D (and corresponding third channel lane  424 D), the fourth channel port  224 C of the third WDM port set  212 C (and corresponding fourth channel lane  426 C). Accordingly, the upper side  204 A and lower side  204 B of the substrate including alternating common ports of the third WDM port set  212 C and the fourth WDM port set  212 D. 
     The WDM optical core subassembly  200  defines a fourth optical path  414 D including a fourth common lane  416 D, a lateral path  418 D, and a plurality of channel lanes  420 D- 426 D. The lateral path  418 D extends between an upper side  204 A of the substrate  202  and a lower side  204 B of the substrate  202  (and between an upper portion  410 A of the trapezoidal-shaped prism  400  and a lower portion  410 B of the trapezoidal-shaped prism  400 ) and from a right side to a left side of the substrate  202 . In particular, a fourth optical signal (wavelengths λ 1 -λ 4 ) extends along the fourth common lane  416 D of the fourth optical path  414 D from the fourth common port  216 D to the right portion  412 B of the fourth WDM filter  208 D. A portion of the second optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the first channel lane  420 D to the first channel port  218 D. Any remaining portion of the second optical signal (wavelengths λ 1 -λ 3 ) is reflected off the right portion  412 B of the fourth WDM filter  208 D to the lower oblique face  408 B to the upper oblique face  408 A to the left portion  412 A of the third WDM filter  208 C. A portion of the remaining first optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the second channel lane  422 D to the second channel port  220 D. Any remaining portion of the fourth optical signal (wavelengths λ 1 -λ 2 ) is reflected off the left portion  412 A of third WDM filter  208 C to the upper oblique face  408 A to the lower oblique face  408 B to the right portion  412 B of the second WDM filter  208 B. A portion of the remaining optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the third channel lane  424 D to the third channel port  222 D. Any remaining portion of the fourth optical signal is reflected off the right portion  412 B of the second WDM filter  208 B to the lower oblique face  408 B to the upper oblique face  408 A to the left portion  412 A of the first WDM filter  208 A. A portion of the remaining optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the fourth channel lane  426 D to the fourth channel port  224 D. Any remaining portion of the first optical signal is reflected off the left portion  412 A of the first WDM filter  208 A. 
     Although, the first, second, third, and fourth optical paths  414 A- 414 D are illustrated separately, the first, second, third, and fourth optical signals can be transmitted consecutively or simultaneously. In this way, the lateral paths  418 A- 418 D of the first, second, third, and/or fourth optical paths  414 A- 414 D may overlap with one another. Further, in some embodiments, the first, second, third, and/or fourth optical paths  414 A- 414 D are configured to not interact with each other. Further, the first WDM port set  212 A may be vertically even or offset from the third WDM port set  212 C (e.g., a portion of the first WDM port set  212 A is positioned between the upper side  204 A of the substrate  202  and a portion of the third WDM port set  212 C), and similarly, the second WDM port set  212 B may be vertically even or offset from the fourth WDM port set  212 D (e.g., the second WDM port set  212 B is positioned between the lower side  204 B of the substrate  202  and the fourth WDM port set  212 D). The lanes of the optical paths  414 A- 414 D are configured to operate, for example, up to 25 Gbps (e.g., with NRZ (nonreturn-to-zero) modulation), up to 50 Gbps (e.g., with PAM4 (pulse amplitude modulation 4)). These could provide solutions of an optical transmission rate of 200-400 Gbps, or more. Further, the WDM optical core subassembly  200  can enable up to 14.4 Tbps aggregate bandwidth in a single switch slot. 
     The WDM optical core subassembly  200  is bi-directional and can transmit and receive multiplexed signals. The double width of each of the WDM filters  208 A- 208 D facilitates minimizing pitch distance (P) between adjacent channel lanes, if desired. In particular, the WDM optical core subassembly  200  avoids the necessity of cutting the WDM filters  208 A into smaller pieces, which thereby avoids manufacturing difficulties. Further, the larger filter size can relax WDM coating layer surface tension stress, which in turn leads to flatter coating surface curvature, which reduces alignment error during manufacturing. The wider WDM filters  208 A- 208 D discussed in  FIGS. 2A-2E  are easier to manufacture and provide smaller pitches between lanes of the optical paths. For example, if the pitch requirement is 250 üm, a filter width of 750 üm or more could be used, which is easily manufacturable. 
       FIGS. 5A-5E  are views of another exemplary embodiment of an optical core subassembly  500  similar to the optical core subassembly  200  of  FIGS. 2A and 4A-4E .  FIG. 5A  is a back perspective view of the optical core subassembly  500 . The optical core subassembly  500  includes an optical signal router  206  and WDM filters  208 A- 208 D. The optical core subassembly  500  may further comprise a substrate  202  and one or more WDM port sets  212 A- 212 D (not shown). The optical core subassembly  500  is similar to that of  FIGS. 4A-4E  except where otherwise noted. 
     In particular, the optical signal router  206  comprises a pentagonal-shaped prism  502  (e.g., horizontally positioned relative to a substrate) for routing optical signals. The pentagonal-shaped prism  502  includes a first base  504 A (also referred to as a left base, etc.), a second base  504 B (also referred to as a right base, etc.) opposite the first base  504 A. The first base  504 A and second base  504 B are each pentagonal-shaped. The pentagonal-shaped prism  502  further including a plurality of surfaces extending between the first base  504 A and the second base  504 B. In particular, the pentagonal-shaped prism  502  further includes a narrow face  508  (also referred to as a front face), a broad face  506  (also referred to as a back face) opposite the narrow face  508 , an upper oblique face  510 A extending upwardly and backwardly from an upper edge of the narrow face  508 , and a lower oblique face  510 B extending downwardly and backwardly from a lower edge of the narrow face  508  opposite the upper oblique face  510 A. The pentagonal-shaped prism  502  further including an upper perpendicular face  512 A extending from an upper edge of the broad face  506  to the upper oblique face  510 A and a lower perpendicular face  512 B extending from a lower edge of the broad face  506  to the lower oblique face  510 B. The narrow face  508  acts as a chamfer and minimizes stress points, reducing damage (e.g., chipping) to the pentagonal-shaped prism  502 . Thus, the narrow face  508  may be omitted. 
     The WDM filters  208 A- 208 D are positioned the same as in the optical core subassembly  200  of  FIGS. 2A-2E  except that the WDM filters  208 A- 208 D are mounted to or otherwise contact the broad face  506  of the pentagonal-shaped prism. When mounted, the broad face  506  and WDM filters  208 A define a border frame  514 . In particular, the border frame  514  includes a left portion  516 A, a right portion  516 B, a top portion  518 A, and a bottom portion  518 B. The top and bottom portions  518 A,  518 B provide clearance for mounting the WDM filters  208 A- 208 D to the broad face  506  of the pentagonal-shaped prism  502 . Accordingly, the top and bottom portions  518 A,  518 B may be reduced or omitted. The left and right portions  516 A,  516 B also provide clearance for mounting the WDM filters  208 A- 208 D to the broad face  506  of the pentagonal-shaped prism  502 . However, the left and right portions  516 A,  516 B also provide a point of entry and/or a point of exit for an optical signal from one of the common ports  216 A- 216 D. 
       FIGS. 5B-5E  are views of the optical core subassembly of  FIG. 5A  illustrating optical paths between a plurality of WDM port sets  212 A- 212 D. In particular, the optical core subassembly  500  provides four common ports  216 A- 216 D and sixteen channel ports  216 A- 224 D using four WDM filters  208 A (and four respective passbands). The signal routing and optical paths  414 A- 414 D are the same as in  FIGS. 4B-4E  unless otherwise noted. 
     The first set WDM common port  216 A of the first WDM port set  212 A is positioned approximately horizontally adjacent to the channel ports towards a rear of the pentagonal-shaped prism  502  and to a left thereof. The second set WDM common port  216 B of the second WDM port set  212 B is positioned approximately horizontally adjacent to the channel ports towards a rear of the pentagonal-shaped prism  502  and to a left thereof. The third common port  216 C of the third WDM port set  212 C is positioned approximately horizontally adjacent to the channel ports towards a rear of the pentagonal-shaped prism  502  and to a right thereof. The fourth common port  216 D of the fourth WDM port set  212 D is positioned approximately horizontally adjacent to the channel ports towards a rear of the pentagonal-shaped prism  502  and to a right thereof. Placing the common ports  216 A- 216 D horizontally adjacent to the channel ports  218 A- 224 D decreases the depth (D 1 ) of the WDM optical core subassembly  500 . 
       FIG. 5B  is a top view of the optical core subassembly  500  of  FIG. 5A  illustrating a first optical path between the first set WDM common port  216 A and the four channel ports  218 A- 224 A. The first set WDM common port  216 A forms a first optical path  414 A with each of the four channel ports  218 A- 224 A. The first WDM port set  212 A includes the first set WDM common port  216 A positioned on an upper side  204 A of the broad face  406  towards a left side thereof. The first WDM port set  212 A further includes a first set first WDM channel port  218 A at a lower side of the broad face  406  towards the left side of the pentagonal-shaped prism  502 , a first set second WDM channel port  220 A at an upper side of the broad face  406  towards the left side of the pentagonal-shaped prism  502 , a first set third WDM channel port  222 A at a lower side of the broad face  406  towards the right side of the pentagonal-shaped prism  502 , and a first set fourth WDM channel port  224 A at an upper side of the broad face  406  towards the right side of the trapezoidal-shaped prism  502 . The first set WDM common port  216 A is angled (or configured to direct an optical signal at an angle) relative to a center plane F-F of the pentagonal-shaped prism (and/or substrate  202 ). The channel ports  218 A- 224 A are angled opposite to the first set WDM common port  216 A. 
     The WDM optical core subassembly  500  defines a first optical path  414 A including a first common lane  416 A, a lateral path  418 A, and a plurality of channel lanes  420 A- 426 A. The lateral path  418 A extends between an upper portion  410 A and a lower portion  410 B of the broad face  506  and from a left side to a right side of the broad face  506 . In particular, a first optical signal (wavelengths λ 1 -λ 4 ) extends along the first common lane  416 A of the first optical path  414 A from the first set WDM common port  216 A to the left portion  516 A of the frame  514  of the broad face  506  to the upper oblique face  510 A to the lower oblique face  510 B to the left portion  412 A of the second WDM filter  208 B. A portion of the first optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the first channel lane  420 A to the first set first WDM channel port  218 A. Any remaining portion of the first optical signal (wavelengths λ 1  and λ 3 -λ 4 ) is reflected off the left portion  412 A of the second WDM filter  208 B to the lower oblique face  510 B to the upper oblique face  510 A to the right portion  412 B of the first WDM filter  208 A. A portion of the remaining first optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the second channel lane  422 A to the first set second WDM channel port  220 A. Any remaining portion of the first optical signal (wavelengths λ 3 -λ 4 ) is reflected off the right portion  412 B of first WDM filter  208 A to the upper oblique face  510 A to the lower oblique face  510 B to the left portion  412 A of the fourth WDM filter  208 D. A portion of the remaining optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the third channel lane  424 A to the first set third WDM channel port  222 A. Any remaining portion of the first optical signal (wavelengths λ 3 ) is reflected off the left portion  412 A of the fourth WDM filter  208 D to the lower oblique face  510 B to the upper oblique face  510 A to the right portion  412 B of the third WDM filter  208 C. A portion of the remaining optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the fourth channel lane  426 A to the first set fourth WDM channel port  224 A. Any remaining portion of the first optical signal is reflected off the right portion  412 B of the third WDM filter  208 C. 
       FIG. 5C  is a top view of the optical core subassembly of  FIG. 5A  illustrating a second optical path between a second common port and four channel ports. The second set WDM common port  216 B forms a second optical path  414 B with each of the four channel ports  218 B- 224 B. The second WDM port set  212 B includes the second set WDM common port  216 B positioned on a lower side  410 B of the broad face  406  towards a left side thereof. The second WDM port set  212 B further includes a second set first WDM channel port  218 B at an upper side  204 B of the substrate  202  towards the left side of the broad face  406 , a second set second WDM channel port  220 B at a lower side  204 A of the substrate  202  towards the left side of the broad face  406 , a first set third WDM channel port  222 A at an upper side  204 B of the substrate  202  towards the right side of the broad face  406 , and a second set fourth WDM channel port  224 B at a lower side  204 A of the substrate  202  towards the right side of the broad face  406 . The second set WDM common port  216 B is angled (or configured to direct an optical signal at an angle) relative to a center plane F-F of the trapezoidal-shaped prism (and/or substrate  202 ), the same (or similar) angle as the first set WDM common port  216 A. Accordingly, the first set WDM common port  216 A may be vertically aligned with the second set WDM common port  216 B. The channel ports  218 B- 224 B are oppositely angled as that of the second set WDM common port  216 B and/or the first set WDM common port  216 A. Further, the channel ports  218 B- 224 B are similarly angled and/or configured as the channel ports  218 A- 224 A. The channel ports on the upper side may be vertically aligned with the channel ports on the lower side. 
     Accordingly, the upper side of the broad face  406  includes (from left to right) the second set first WDM channel port  218 B of the second WDM port set  212 B (and corresponding first channel lane  420 B), the first set second WDM channel port  220 A of the first WDM port set  212 A (and corresponding second channel lane  422 A), the second set third WDM channel port  222 B of the second WDM port set  212 B (and corresponding third channel lane  424 B), the first set fourth WDM channel port  224 A of the first WDM port set  212 A (and corresponding fourth channel lane  426 A). Similarly, the lower side the lower side  204 B of the broad face  506  includes (from left to right) the first set first WDM channel port  218 A of the first WDM port set  212 A (and corresponding first channel lane  420 A), the second set second WDM channel port  220 B of the second WDM port set  212 B (and corresponding second channel lane  422 B), the first set third WDM channel port  222 A of the first WDM port set  212 A (and corresponding third channel lane  424 A), the second set fourth WDM channel port  224 B of the second WDM port set  212 B (and corresponding fourth channel lane  426 B). Accordingly, the upper side  204 A and lower side  204 B of the substrate including alternating common ports of the first WDM port set  212 A and the second WDM port set  212 B. 
     The WDM optical core subassembly  500  defines a second optical path  414 B including a second common lane  416 B, a lateral path  418 B, and a plurality of channel lanes  420 B- 426 B. The lateral path  418 B extends between an upper portion  410 A and a lower portion  410 B of the broad face  506  and from a left side to a right side of the broad face  506 . In particular, a second optical signal (wavelengths λ 1 -λ 4 ) extends along the second common lane  416 B of the second optical path  414 B from the second set WDM common port  216 B to the left portion  516 A of the frame  514  of the broad face  506  to the lower oblique face  510 B to the upper oblique face  510 A to the left portion  412 A of the first WDM filter  208 A. A portion of the second optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the first channel lane  420 B to the second set first WDM channel port  218 B. Any remaining portion of the second optical signal (wavelengths λ 2 -λ 4 ) is reflected off the left portion  412 A of the first WDM filter  208 A to the upper oblique face  510 A to the lower oblique face  510 B to the right portion  412 B of the second WDM filter  208 B. A portion of the remaining first optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the second channel lane  422 B to the second set second WDM channel port  220 B. Any remaining portion of the second optical signal (wavelengths λ 3 -λ 4 ) is reflected off the right portion  412 B of second WDM filter  208 B to the lower oblique face  510 B to the upper oblique face  510 A to the left portion  412 A of the third WDM filter  208 C. A portion of the remaining optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the third channel lane  424 B to the second set third WDM channel port  222 B. Any remaining portion of the second optical signal (wavelengths λ 4 ) is reflected off the left portion  412 A of the third WDM filter  208 C to the upper oblique face  510 A to the lower oblique face  510 B to the right portion  412 B of the fourth WDM filter  208 D. A portion of the remaining optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the fourth channel lane  426 B to the second set fourth WDM channel port  224 B. Any remaining portion of the first optical signal is reflected off the right portion  412 B of the fourth WDM filter  208 D. 
       FIG. 5D  is a top view of the optical core subassembly of  FIG. 5A  illustrating a third optical path between a third common port and four channel ports. The third common port  216 C forms a third optical path  414 C with each of the four channel ports  218 C- 224 C. The third WDM port set  212 C includes the third common port  216 C positioned on an upper side  204 A of the broad face  506  towards a right side thereof. The third WDM port set  212 C further includes a first channel port  218 C at a lower side  204 A of the substrate  202  towards the right side of the broad face  506 , a second channel port  220 C at an upper side of the broad face  506  towards the right side thereof, a first set third WDM channel port  222 A at a lower side of the broad face  506  towards the left side thereof, and a first set fourth WDM channel port  224 A at an upper side of the broad face  506  towards the left side thereof. The third common port  216 C is angled (or configured to direct an optical signal at an angle) relative to a center plane F-F of the pentagonal-shaped prism  502  (and/or substrate  202 ). The channel ports  218 C- 224 C are oppositely angled as that of the third common port  216 C (and similar to the first set WDM common port  216 A, second set WDM common port  216 B, channel ports  218 A- 224 A, and/or channel ports  218 B- 224 B). 
     The WDM optical core subassembly  500  defines a third optical path  414 C including a first common lane  416 C, a lateral path  418 C, and a plurality of channel lanes  420 C- 426 C. The lateral path  418 C extends between an upper portion  410 A and a lower portion  410 B of the broad face  506  and from a left side to a right side of the broad face  506 . In particular, a third optical signal (wavelengths λ 1 -λ 4 ) extends along the first common lane  416 C of the third optical path  414 C from the third common port  216 C to the right portion  516 B of the frame  514  of the broad face  506  to the upper oblique face  510 A to the lower oblique face  10 B to the right portion  412 B of the fourth WDM filter  208 D. A portion of the first optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the first channel lane  420 C to the first channel port  218 C. Any remaining portion of the first optical signal (wavelengths λ 1 -λ 3 ) is reflected off the right portion  412 B of the fourth WDM filter  208 D to the lower oblique face  510 B to the upper oblique face  510 A to the left portion  412 A of the third WDM filter  208 C. A portion of the remaining first optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the second channel lane  422 C to the second channel port  220 C. Any remaining portion of the third optical signal (wavelengths λ 1 -λ 2 ) is reflected off the left portion  412 A of third WDM filter  208 C to the upper oblique face  510 A to the lower oblique face  510 B to the right portion  412 B of the second WDM filter  208 B. A portion of the remaining optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the third channel lane  424 C to the third channel port  222 C. Any remaining portion of the third optical signal (wavelengths λ 1 ) is reflected off the right portion  412 B of the second WDM filter  208 B to the lower oblique face  510 B to the upper oblique face  510 A to the left portion  412 A of the first WDM filter  208 A. A portion of the remaining optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the fourth channel lane  426 D to the fourth channel port  224 D. Any remaining portion of the third optical signal is reflected off the left portion  412 A of the first WDM filter  208 A. 
       FIG. 5E  is a top view of the optical core subassembly of  FIG. 5A  illustrating a fourth optical path between a fourth common port and four channel ports. The fourth common port  216 D forms a fourth optical path  414 D with each of the four channel ports  218 D- 224 D. The fourth WDM port set  212 D includes the fourth common port  216 D positioned on a lower side  204 B of the broad face  506  towards a right side thereof. The fourth WDM port set  212 D further includes a first channel port  218 D at an upper side of the broad face  506  towards the right side thereof, a second set second WDM channel port  220 B at a lower side of the broad face  506  towards the right side thereof, a third channel port  222 D at an upper side of the broad face  506  towards the left side thereof, and a fourth channel port  224 D at a lower side of the broad face  506  towards the left side thereof. The fourth common port  216 D is angled (or configured to direct an optical signal at an angle) relative to a center plane F-F of the pentagonal-shaped prism  502  (and/or substrate), the same (or similar) angle as the third common port  216 C. Accordingly, the fourth common port  216 D may be vertically aligned with the third common port  216 C. The channel ports  218 D- 224 D are oppositely angled as that of the fourth common port  216 D and/or the third common port  216 C. Further, the channel ports  218 D- 224 D are similarly angled and/or configured as the channel ports  218 C- 224 C. The channel ports on the upper side may be vertically aligned with the channel ports on the lower side. 
     Accordingly, the upper side of the broad face  506  includes (from right to left) the first channel port  218 D of the fourth WDM port set  212 D (and corresponding first channel lane  420 D), the second channel port  220 C of the third WDM port set  212 C (and corresponding second channel lane  422 C), the third channel port  222 D of the fourth WDM port set  212 D (and corresponding third channel lane  424 D), the third channel port  224 C of the third WDM port set  212 C (and corresponding fourth channel lane  426 C). Similarly, the lower side of the substrate includes (from right to left) the first channel port  218 C of the third WDM port set  212 C (and corresponding first channel lane  420 C), the second channel port  220 D of the fourth WDM port set  212 D (and corresponding second channel lane  422 D), the third channel port  222 C of the third WDM port set  212 C (and corresponding third channel lane  424 C), the fourth channel port  224 D of the fourth WDM port set  212 D (and corresponding fourth channel lane  426 D). Accordingly, the upper side and lower side of the substrate include alternating common ports of the third WDM port set  212 C and the fourth WDM port set  212 D. 
     The WDM optical core subassembly  200  defines a fourth optical path  414 D including a fourth common lane  416 D, a lateral path  418 D, and a plurality of channel lanes  420 D- 426 D. The lateral path  418 D extends between an upper portion  410 A and a lower portion  410 B of the broad face  506  and from a left side to a right side of the broad face  506 . In particular, a fourth optical signal (wavelengths λ 1 -λ 4 ) extends along the fourth common lane  416 D of the fourth optical path  414 D from the fourth common port  216 D to the right portion  516 B of the frame  514  of the broad face  506  to the lower oblique face  510 B to the upper oblique face  510 A to the right portion  412 B of the third WDM filter  208 C. A portion of the fourth optical signal (wavelengths λ 3 ) may pass through the third passband of the third WDM filter  208 C to the first channel lane  420 D to the first channel port  218 D. Any remaining portion of the second optical signal (wavelengths λ 1 -λ 2  and λ 4 ) is reflected off the right portion  412 B of the third WDM filter  208 C to the upper oblique face  510 A to the lower oblique face  510 B to the left portion  412 A of the fourth WDM filter  208 D. A portion of the remaining fourth optical signal (wavelengths λ 4 ) may pass through the fourth passband of the fourth WDM filter  208 D to the second channel lane  422 D to the second channel port  220 D. Any remaining portion of the fourth optical signal (wavelengths λ 1 -λ 2 ) is reflected off the left portion  412 A of fourth WDM filter  208 D to the lower oblique face  510 B to the upper oblique face  510 A to the right portion  412 B of the first WDM filter  208 A. A portion of the remaining optical signal (wavelengths λ 1 ) may pass through the first passband of the first WDM filter  208 A to the third channel lane  424 D to the third channel port  222 D. Any remaining portion of the fourth optical signal (wavelengths λ 2 ) is reflected off the right portion  412 B of the first WDM filter  208 A to the upper oblique face  510 A to the lower oblique face  510 B to the left portion  412 A of the second WDM filter  208 B. A portion of the remaining optical signal (wavelengths λ 2 ) may pass through the second passband of the second WDM filter  208 B to the fourth channel lane  426 D to the fourth channel port  224 D. Any remaining portion of the first optical signal is reflected off the left portion  412 A of the second WDM filter  208 B. 
     Although, the first, second, third, and fourth optical paths  414 A- 414 D are illustrated separately, the first, second, third, and fourth optical signals can be transmitted consecutively or simultaneously. In this way, the lateral paths  418 A- 418 D of the first, second, third, and fourth optical paths  414 A- 414 D may overlap with one another. Further, the first WDM port set  212 A may be vertically even or offset from the third WDM port set  212 C (e.g., the first WDM port set  212 A is positioned between the upper side  204 A of the substrate  202  and the third WDM port set  212 C), and similarly the second WDM port set  212 B may be vertically even or offset from the fourth WDM port set  212 D (e.g., the second WDM port set  212 B is positioned between the lower side  204 B of the substrate  202  and the fourth WDM port set  212 D). 
       FIGS. 6A-6B  are views of another exemplary embodiment of the WDM optical assembly of  FIG. 2B  and illustrating a first optical path between a first common collimator and four channel collimators. A WDM optical assembly  600  provides four WDM port sets  212 A- 212 D embodied as four WDM collimator sets  214 A- 214 D which includes four common ports  216 A- 216 D embodied as four common collimators  226 A- 226 D and sixteen channel ports  218 A- 224 D embodied as sixteen channel collimators  228 A- 234 D using four WDM filters  208 A- 208 D (and four respective passbands). In particular, the WDM optical assembly  600  includes a first WDM collimator set  214 A (including a first set WDM common collimator  226 A (also referred to as a first WDM common collimator, first common collimator, etc.), first set first WDM channel collimator  228 A, first set second WDM channel collimator  230 A, first set third channel WDM collimator  232 A, and first set fourth WDM channel collimator  234 A), a second WDM collimator set  214 B (including a second set WDM common collimator  226 B (also referred to as a second WDM common collimator, second common collimator, etc.), second set first WDM channel collimator  228 B, second set second WDM channel collimator  230 B, second set third WDM channel collimator  232 B, and second set fourth WDM channel collimator  234 B), a third WDM collimator set  214 C (including a third set WDM common collimator  226 C (also referred to as a third WDM common collimator, third common collimator, etc.), third set first WDM channel collimator  228 C, third set second WDM channel collimator  230 C, third set third WDM channel collimator  232 C, and third set fourth WDM channel collimator  234 C), and a fourth WDM collimator set  214 D (including a fourth set WDM common collimator  226 D (also referred to as a fourth WDM common collimator, fourth common collimator, etc.), fourth set first WDM channel collimator  228 D, fourth set second WDM channel collimator  230 D, fourth set third WDM channel collimator  232 D, and fourth set fourth WDM channel collimator  234 D). The collimators of the first, second, third, and fourth sets of collimators  214 A,  214 B,  214 C,  214 D form a first array  602 A on an upper side  204 A of the substrate  202  towards a left side thereof, a second array  602 B on a lower side  204 B of the substrate  202  towards a left side thereof, a third array  602 C on the upper side  204 A of the substrate  202  towards a right side thereof, and a fourth array  602 D on the lower side  204 B of the substrate  202  towards a right side thereof. The first array  602 A and the second array  602 B include alternating channel collimators from the third WDM collimator set  214 C and the fourth WDM collimator set  214 D, and the third array  602 C and the fourth array  602 D include alternating channel collimators from the first WDM collimator set  214 A and the second WDM collimator set  214 B. In particular, the setup is similar to that discussed in  FIGS. 4A-5E . 
     The first array  602 A and third array  602 C are positioned on the upper side  204 A of the substrate  202 . In the WDM optical assembly  600 , the first array  602 A and the third array  602 C must be positioned at a specific angle to be in line with their respective first, second, third, and fourth optical paths  414 A- 414 D (second through fourth optical paths  414 A- 414 D are shown in  FIGS. 4A-4E ). Further, if the first array  602 A and the third array  602 C are vertically aligned with one another (e.g., no relative vertical offset), then there is a minimum horizontal distance the first array  602 A and third array  602 C can be to one another (e.g., until one of the collimators of the first array  602 A contacts one of the collimators of the third array  602 C). Accordingly, there is a minimum distance the first array  602 A and the third array  602 C must be from the WDM filters  208 A- 208 D and/or the optical signal router  206  (embodied as trapezoidal-shaped prism  400 ) in order to maintain the appropriate angle to receive the optical signal. 
     Similarly, the second array  602 B and fourth array  602 D are positioned on the lower side  204 B of the substrate  202 . In the WDM optical assembly  600 , the second array  602 B and the fourth array  602 D must be positioned at a specific angle to be in line with their respective first, second, third, and fourth optical paths  414 A- 414 D. Further, if the second array  602 B and the fourth array  602 D are vertically aligned with one another (e.g., no relative vertical offset), then there is a minimum horizontal distance the second array  602 B and fourth array  602 D can be to one another (e.g., until one of the collimators of the second array  602 B contacts one of the collimators of the fourth array  602 D). Accordingly, there is a minimum distance the second array  602 B and the fourth array  602 D must be from the WDM filters  208 A- 208 D and/or the optical signal router  206  (in order to maintain the appropriate angle to receive the optical signal). 
       FIGS. 7A-8D  are views of exemplary embodiments of the WDM optical assembly including a channel port router to decrease the depth of the WDM optical assembly. It is noted that for illustrative purposes, only the collimators in direct contact with the first optical path  414 A receive that portion of the first optical path  414 A. Some portions of the first optical path  414 A are shortened between the figures to indicate direction, but the shortened portion of the optical path  414 A is not received by the collimator in line with the shortened portion (because it is on the opposite side of the substrate  202 ). 
     In particular,  FIGS. 7A-7E  illustrate a WDM optical assembly  700  with a channel port router  702 . In particular, the channel port router  702  includes an upper set  704 A of pentagonal-shaped prisms  706  positioned on an upper side  204 A of the substrate  202  and a lower set  704 B of pentagonal-shaped prisms  706  positioned on a lower side  204 B of the substrate  202 . 
     Referring specifically to  FIG. 7B , each pentagonal-shaped prism  706  includes a first base  708 A (also referred to as a distal base, etc.), and a second base  708 B (also referred to as a medial base, etc.) opposite thereto. The first base  708 A and second base  708 B are each pentagonal-shaped (and vertically oriented). The pentagonal-shaped prism  706  further includes a plurality of faces  710 - 714 B (also referred to as surfaces) extending between the first base  708 A and the second base  708 B. Specifically, each pentagonal-shaped prism  706  includes a front face  710  (e.g., anti-reflective (AR) coated) positioned to face a front of the WDM optical assembly  700 , a first oblique face  712 A (e.g., AR coated) and a second oblique face  712 B (e.g., AR coated) positioned opposite the front face  710 , a first perpendicular face  714 A positioned between the front face  710  and the first oblique face  712 A, and a second perpendicular face  714 B positioned between the front face  710  and the second oblique face  712 B. The pentagonal-shaped prism  706  is designed so that the angle of incident is greater than Brewster angle, such that total internal reflection occurs. 
     The front face  710  of each pentagonal-shaped prism  706  provides an optical signal entry surface and/or an optical signal exit surface. The first and second oblique faces  712 A,  712 B provides an optical signal entry surface, an optical signal exit surface, a first optical signal redirecting surface, and/or a second optical signal redirecting surface. For example, an optical signal which enters the front face  710  is reflected by the second oblique face  712 B (e.g., by total internal reflection) and exits the first oblique face  712 A, and similarly an optical signal may enter the first oblique face  712 A, is reflected by the second oblique face  712 B and exits through the front face  710 . 
     Referring again to  FIGS. 7A-7E , the pentagonal-shaped prism  706  redirects the first, second, third, and fourth channel lanes of the first, second, third, and fourth optical paths  414 A,  414 B,  414 C,  414 D (shown in  FIGS. 4A-4E ) to alter the angle of entry into the channel collimators of the first, second, third, and fourth sets of collimators  214 A- 214 D (shown in  FIGS. 4A-4E ). For example,  FIGS. 7D and 7E  illustrate the first optical path  414 A of the first WDM collimator set  214 A (and omit the second, third, and fourth optical paths  414 B- 414 D for purposes of illustrative clarity only). The pentagonal-shaped prism  706  minimizes the minimum depth (D 2 ) required for the WDM optical assembly  700  (e.g., minimizes the distance between the channel collimators and the optical signal router  206  and/or WDM filters  208 A- 208 D). 
       FIGS. 8A-8E  are views of another exemplary embodiment of the WDM optical assembly including a channel port router to decrease the depth (D 3 ) of the WDM optical assembly. In particular,  FIGS. 8A-8E  illustrate a WDM optical assembly  800  with a channel port router  802 . The channel port router  802  includes an upper octagonal-shaped prism  804 A and a lower octagonal-shaped prism  804 B. Each of the upper and lower octagonal-shaped prisms  804 A,  804 B includes a first base  806 A (also referred to as a left base, etc.) and a second base  806 B (also referred to as a right base, etc.) opposite the first base  806 A. The first base  806 A and second base  806 B are each octagonal shaped and horizontally oriented. The octagonal-shaped prism  804 A,  804 B further includes a plurality of faces  808 - 818  (also referred to as surfaces) extending between the first base  806 A and the second base  806 B. Each of the octagonal-shaped prism  804 A,  804 B includes a medial horizontal face  808  and a distal horizontal face  810  opposite thereto. Further, each of the octagonal-shaped prisms  804 A,  804 B includes a medial front face  812  (e.g., AR coated) perpendicular to the medial horizontal face  808  and distal horizontal face  810 , a medial back face  814  (e.g., high reflective (HR) coated) oblique to the medial horizontal face  808  and distal horizontal face  810 , a distal front face  816  (e.g., HR coated) oblique to the medial horizontal face and/or distal horizontal face  810 , a distal back face  818  (e.g., AR coated) perpendicular to the medial horizontal face  808  and/or distal horizontal face  810 . 
     In this way, the medial front face  812  and distal back face  818  are perpendicular to provide an exit and/or entry of the optical signal into and out of the octagonal-shaped prism  804 A,  804 B. The medial back face  814  and distal front face  816  are oblique to provide internal reflection and routing of the optical signal through the octagonal-shaped prism  804 A,  804 B. For example, the optical signal enters the medial front face  812 , is reflected off the medial back face  814 , and then reflected off the distal front face  816 , and then exits through the distal back face  818 . 
     Accordingly, for example, the start of the first channel lane  420 A of the first optical path  414 A is horizontally offset from the end of the first channel lane  420 A (e.g., such that the end of the first channel lane  420 A is further from a center of the substrate  202  than the start of the first channel lane  420 A). This is also applicable for the second, third, and fourth channel lanes  422 A- 426 A, and for each of the second, third, and fourth optical paths  414 B- 414 D (shown in  FIGS. 4A-4E  and omitted for purposes of illustrative clarity only). Offsetting the channel lanes  420 A- 426 A minimizes the minimum depth required for the WDM optical assembly  800  (e.g., minimizes the distance between the channel collimators and the optical signal router  206  and/or WDM filters  208 A- 208 D). 
       FIGS. 9A-9H  are views of another exemplary embodiment of a WDM optical assembly  900 . In particular, the WDM optical assembly  900  includes a first WDM port set  212 A and a second WDM port set  212 B. The first WDM port set  212 A includes a first set WDM common port  216 A on the upper side  204 A of the substrate  202 , and the second WDM port set  212 B includes a second set WDM common port  216 B on the lower side  204 B of the substrate  202 . Further, the first WDM port set  212 A includes channel ports  218 A- 224 A on the lower side  204 B of the substrate  202 , and the second WDM port set  212 B includes channel ports  218 B- 224 B on the lower side  204 B of the substrate  202 . 
     The WDM optical assembly  900  includes WDM filters  908 A- 908 D on the upper side  204 A of the substrate  202 . The WDM filters  908 A- 908 D are half as wide as the WDM filters  208 A- 208 D of  FIGS. 2A-2B and 4A-8D . Further, unlike the WDM optical assemblies of  FIGS. 2A-2B and 4A-8D , the WDM filters  908 A- 908 D are all positioned on the same side of the substrate  202 . Further, the WDM optical assembly  900  includes a mirror  902  (e.g., a plurality of mirrors) on the upper side  204 A of the substrate  202  positioned towards a back off the WDM optical assembly  900  such that the WDM filters  908 A- 908 D are positioned between the mirror  902  and the optical signal router  206  (embodied as a trapezoidal-shaped prism  400 ). Further, the first and second set WDM common ports  216 A,  216 B are positioned at a back of the WDM optical assembly  900  such that the mirror  902  is positioned between the trapezoidal-shaped prism  400  and the first and second set WDM common ports  216 A,  216 B. 
     Accordingly, the lateral paths  418 A,  418 B of the first and second optical paths  414 A,  414 B are formed between the mirror and the WDM filters  908 A,  908 B. The channel lanes  420 A- 426 B extend from the WDM filters  908 A- 908 D to the upper oblique face  408 A of the trapezoidal-shaped prism  400  to the lower oblique face  408 B of the trapezoidal-shaped prism  400  to the channel ports  218 A- 224 B. In this way, for example, a signal from the first set WDM common port  216 A is demultiplexed on the upper side  204 A of the substrate  202  before contacting the optical signal router  206 . 
     Further, the WDM optical assembly  900  includes a common port router  903 , the common port router  903  including a first quadrilateral prism  904 A (also referred to as a left quadrilateral prism) and a second quadrilateral prism  904 B (also referred to as a right quadrilateral prism). Each of the quadrilateral prisms  904 A,  904 B including a first base  906 A and a second base  906 B opposite the first base. Each quadrilateral prism  904 A,  904 B includes a medial surface  910 A and a distal surface  910 B opposite to the medial surface  910 A. The medial surfaces  910 A of the first and second quadrilateral prisms  904 A,  904 B proximate the mirror  902 . Each of the quadrilateral prisms  904 A,  904 B including a perpendicular front face  912  (e.g., perpendicular to the medial and distal surfaces  910 A,  910 B), and an oblique back face  914  (e.g., oblique to the medial and distal surfaces  910 A,  910 B). Accordingly, the first and second set WDM common ports  216 A,  216 B can be aligned perpendicular to the broad face  406  of the trapezoidal-shaped prism  400 , and the left and right quadrilateral prisms  904 A,  904 B redirect the optical signal to provide an angle (e.g., to form lateral paths  418 A,  418 B). For example, an optical signal from the first set WDM common port  216 A enters the oblique back face  914  and exits the perpendicular front face  912  to the first WDM filter  908 A. 
     Further, the WDM optical assembly  900  includes a channel port router  916 , the common port router  916  including a left quadrilateral prism  918 A and a right quadrilateral prism  918 B. Each of the quadrilateral prisms  918 A,  918 B including a first base  920 A and a second base  920 B opposite the first base. Each quadrilateral prism  918 A,  918 B includes a medial surface  922 A and a distal surface  922 B opposite to the medial surface  922 A. The medial surfaces  922 A,  922 B of the first and second quadrilateral prisms  918 A,  918 B are proximate each other. Each of the quadrilateral prisms  918 A,  918 B includes a perpendicular front face  924  (e.g., perpendicular to the medial and distal surfaces  922 A,  922 B), and an oblique back face  926  (e.g., oblique to the medial and distal surfaces  922 A,  922 B). Accordingly, the channel ports  218 A- 224 B can be aligned perpendicular to the broad face  406  of the trapezoidal-shaped prism  400 , and the left and right quadrilateral prisms  918 A,  918 B redirect the optical signal to provide an angle. For example, an optical signal redirected from the lower oblique face  408 B of the trapezoidal-shaped prism  400  enters the perpendicular front face  924  and exits the oblique back face  926  to one of the channel ports  218 A- 224 B. 
     Of course, the common port router  903  and the channel port router  916  could be omitted and the corresponding ports angled non-perpendicularly to the broad face  406  of the trapezoidal-shaped prism  400 . 
       FIGS. 10A-10B  are views of the WDM device of  FIG. 2B . As discussed above, the WDM optical assembly  210  includes the WDM optical core subassembly  200  and first and second WDM collimator set  214 A,  214 B. Further, the WDM optical assembly  210  includes an optical signal router  1000 , the optical signal router including an upper trapezoidal-shaped prism  1001 A and a lower vertical trapezoidal-shaped prism  1001 B. The upper trapezoidal-shaped prism  1001 A includes a first base  1002 A (also referred to as a medial base) and a second base  1002 B (also referred to as a distal base) opposite the first base  1002 A. Further, the trapezoidal-shaped prism  1001 A,  1001 B includes a plurality of faces  1004 - 1008 B. In particular, each trapezoidal-shaped prism  1001 A,  1001 B includes a narrow face  1004 , and a broad face  1006  opposite the narrow face  1004 . Further, the trapezoidal-shaped prism  1001 A,  1001 B includes a first oblique face  1008 A and second oblique face  1008 B opposite the first oblique face  1008 A. Accordingly, for example, an optical signal from the first set WDM common collimator  226 A enters the first oblique face  1008 A to the second oblique face  1008 B to the trapezoidal-shaped prism  400 . Thus, the trapezoidal-shaped prisms  1001 A,  1001 B bend the optical path such that the first set WDM common port  216 A can be angularly aligned with the channel ports  228 A- 234 B, which decreases the width (W 3 ) of the WDM optical assembly  210 . However, the vertical trapezoidal-shaped prisms  1001 A,  1001 B could be omitted and the first and second set WDM common collimators  226 A,  226 B oppositely angled relative to the other collimators (e.g., but vertically aligned with each other). 
       FIG. 11  is a perspective view of a steel-tube collimator  1100  for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B . The collimator narrows a beam of particles or waves. In other words, the collimator causes the directions of motion to become more aligned in a specific direction. The steel-tube collimator  1100  includes a steel-tube body  1102 , with a curved lens  1104  at one end of the steel-tube body, and a fiber optic pigtail  1106  at an opposite end of the steel-tube body. 
       FIGS. 12A-12B  are perspective views of a square tube collimator for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B . The square tube collimator  1200  includes a glass tube  1202  (e.g., cylindrical) with a central bore  1204 . As used herein, the term “cylindrical” is used in its most general sense and can be defined as a three-dimensional object formed by taking a two-dimensional object and projecting it in a direction perpendicular to its surface. Thus, a cylinder, as the term is used herein, is not limited to having a circular cross-section shape but can have any cross-sectional shape, such as the square cross-sectional shape described below by way of example. 
     The square tube collimator further includes optical elements, such as a collimating lens  1206 , ferrule  1208 , etc., which can be secured to the glass tube  1202  using a securing mechanism (e.g., an adhesive). The collimating lens  1206  has a front surface  1210 A and a back surface  1210 B opposite thereto. In the example shown, the front surface  1210 A is convex while the back surface  1210 B can be an angled, e.g., in the x-z plane as shown. In an example, the front surface  1210 A of collimating lens  1206  can reside outside of the central bore  1204 , i.e., the front-end portion of the collimating lens  1206  can extend slightly past the front end of the glass tube  1202 . In an example, the collimating lens  1206  can be formed as a gradient-index (GRIN) element that has a planar front surface  1210 A. In an example, the collimating lens  1206  can consist of a single lens element while in another example it can consist of multiple lens elements. In the discussion below, the collimating lens  1206  is shown as a single lens element for ease of illustration and discussion. 
     The optical fiber support member is the form of a ferrule  1208 . The ferrule  1208 . The ferrule  1208  includes a central bore  1212  that runs between a front end and a back end along a ferrule central axis AF, which in an example is co-axial with the tube central axis AT of the glass tube  1202  and the optical axis OA as defined by the collimating lens  1206 . The central bore  1212  can include a flared portion  1214  at the back end of the ferrule  1208 . 
     An optical fiber  1216  has a coated portion  1218  and an end portion  1220  is bare glass (e.g., is stripped of the coated portion) and is thus referred to as the “bare glass portion.” The bare glass portion  1220  includes a polished end face  1222  that defines a proximal end of the optical fiber. The bare glass portion  1220  of the optical fiber  1216  extends into the central bore  1212  of the ferrule  1208  at the back end of the ferrule. A securing element  1224  can be disposed around the optical fiber  1216  at the back end of the ferrule  1208  to secure the optical fiber to the ferrule. The front end of the ferrule  1208  is angled in the x-z plane and is axially spaced apart from the angled back end of the collimating lens to define a gap  1226  that has a corresponding axial gap distance DG. 
     The ferrule  1208 , optical fiber  1216  and securing element  1224  constitute a fiber optic pigtail  1228 , which can be said to reside at least partially within bore  1204  adjacent the back end of the glass tube  1202 . Thus, in an example, the square tube collimator  1200  includes only the glass tube  1202 , the collimating lens  1206  and the fiber optic pigtail  1228 . The glass tube  1202  serves in one capacity as a small lens barrel that supports and protects the collimating lens  1206  and fiber optic pigtail  1228 , particularly the bare glass portion  1220  and its polished end face  1222 . The glass tube  1202  also serves in another capacity as a mounting member that allows for the square tube collimator  1200  to be mounted to a support substrate. In this capacity, at least one flat surface  1230  serves as a precision mounting surface. 
     In an example, the glass tube  1202 , the collimating lens  1206  and the ferrule  1208  are all made of a glass material, and further in an example, are all made of the same glass material. Making the glass tube  1202 , the collimating lens  1206  and the ferrule  1208  out of a glass material has the benefit that these components will have very close if not identical coefficients of thermal expansion (CTE). This feature is particular advantageous in environments that can experience large swings in temperature. 
     In an example, the optical elements used in micro-optical systems are sized to be slightly smaller than the diameter of the bore  1204  (e.g., by a few microns or tens of microns) so that the optical elements can be inserted into the bore  1204  and be movable within the bore  1204  to a select location. In an example, the select location is an axial position where optical element resides for the micro-optical system to have optimum or substantially optimum optical performance. Here, substantially optimum performance means performance that may not be optimum but that is within a performance or specification for the micro-optical system. 
     In another example, the optical elements have a clearance with respect to the bore  1204  in the range of a few microns (e.g., 2 microns or 3 microns) to tens of microns (e.g., 20 microns up to 50 microns). A relatively small value for the clearance allows for the optical elements  110  to be well-aligned with the central bore axis AB, e.g., to within a few microns (e.g., from 2 microns to 5 microns). 
     The optical elements and the support/positioning elements can be inserted into and moved within bore  1204  to their select locations using micro-positioning devices. The optical elements and the support/positioning elements can be secured within the bore  1204  using a number of securing techniques. One example securing technique uses a securing feature that is an adhesive (e.g., a curable epoxy). Another securing technique uses a securing feature that involves a glass soldering to create one or more glass solder points. Another securing technique uses glass welding to create a securing feature in the form of one or more glass welding points. A combination of these securing features can also be employed. 
     Thus, one or more optical elements can be secured within the bore  1204  using a securing feature and can also be supported and/or positioned using one or more support/positioning elements. The non-adhesive securing techniques described below allow for the micro-optical systems disclosed herein to remain free of adhesives so that, for example, micro-optical systems can consist of glass only. 
       FIG. 13A  is a perspective view of a compact collimator for use with the WDM optical core assemblies and/or WDM device of  FIGS. 2A-10B . The collimator  1300  includes a lens  1302  (e.g., a glass or silica collimating lens), a fiber optic pigtail  1304  and a groove (e.g., a generally V-shaped groove) formed in a base  1306 . The lens  1302  and the fiber optic pigtail  1304  are disposed in the groove. The lens  1302  is configured to receive a light signal provided to the WDM multiplexer/demultiplexer from an external optical transmission system or provide a light signal multiplexed or demultiplexed by the WDM to an external optical transmission system. The lens  1302 , for example, may be configured to receive a light signal from a fiber optic element for multiplexing or demultiplexing and/or to provide a multiplexed or demultiplexed light signal to an external fiber optic element. The fiber optic pigtail  1304  is optically coupled to the lens  1302  and is configured to provide a light signal to the lens  1302  from the external fiber optic element and/or to receive the light signal from the lens  1302  for transmission to the external fiber optic element. 
     In various embodiments, the lens  1302  and the fiber optic pigtail  1304  may or may not contact each other. The lens  1302  and the fiber optic pigtail  1304  may be securable to the groove independent of each other to allow for precise adjustment of a pointing angle between an optical beam from the collimator  1300  and a side and/or bottom surface of the groove. In addition, the lens  1302  and fiber optic pigtail  1304  may have the same outer diameter. 
     The base  1306  of the collimator  1300  has a generally flat bottom surface  1308  for mounting on a substrate of a WDM multiplexer/demultiplexer or other optical system. The base  1306  further includes a width that is less than a width of the lens  1302  and a width of the fiber optic pigtail  1304 . 
       FIG. 13B  is a side view of the compact collimator of  FIG. 13A . A pointing angle between an optical beam from a collimator  1300  and the side and bottom surface of the groove can be eliminated (or at least reduced) by controlling the relative position between a lens  1302  and the fiber optic pigtail  1304  of the collimator  1300 . By fine tuning the position of fiber optic pigtail  1304  to make an outgoing beam come across a focal point of the lens  1302 , a collimated zero pointing angled beam with negligible off axis offset can be achieved. In one embodiment, for example, the tuning can be monitored by near field and far field beam position comparison (e.g., using a beam scanner). The zero pointing angle collimating components are easier to attach to the substrate with little inclination and more reliable bonding is possible due to the uniform epoxy or bonding agent. It is noted that  13 B is a schematic illustration used to illustrate concepts of the description and that the ends of the glass lens and the fiber optic pigtail  1304  may be oriented at other angles, including perpendicular, to the body of the glass lens and the fiber optic pigtail, respectively. 
     The structures of the collimator  1300  allow for easier modularization and remove redundant degrees of freedom versus designs in which a collimator is coupled and attached to the substrate via external wedges or supports. Thus, the collimator  1300  may reduce the complexity and further increase the assembly efficiency and process reliability of the overall multiplexer/demultiplexer design. 
       FIGS. 14A-14B  are views of an array  1400  of the collimators  1300  of  FIGS. 13A-13B . The collimators  1300  are arranged side-by-side on a surface of a substrate  1402 , the substrate  1402  including a plurality of grooves  1404  (discussed above). The grooves  1404  could be v-grooves or any other type of groove. A spacing between the base  1306  of the side-by-side collimators  1300  is greater than a spacing between the lenses  1302  and fiber optic pigtails  1304  of the side-by-side collimators  1300 . 
       FIG. 15  is a perspective view of another exemplary embodiment of a fiber array unit (FAU)  1500  and multi-lens array (MLA)  1502  for use with the WDM optical core assemblies and/or WDM devices of  FIGS. 2A-10B . More specifically, the FAU  1500  includes a plurality of fibers  1504  and the MLA  1502  includes a plurality of lenses  1506 . The FAU  1500  and MLA  1502  can be used with any of the embodiments discussed above. 
       FIG. 16  is a flowchart illustrating an exemplary process that can be employed to manufacture a WDM optical core subassembly of  FIGS. 2A-10B . Step  1600  includes positioning a first WDM filter  208 A having a first passband relative to an optical signal router  206 . Step  1602  includes positioning a second WDM filter  208 B having a second passband relative to the optical signal router  206 . 
     Step  1604  includes positioning a first set WDM common port  216 A relative to the optical signal router  206 . The first set WDM common port  216 A is configured for optical communication of a first multiplexed signal. Step  1606  includes positioning a first set first WDM channel port  218 A relative to the optical signal router  206 . The first set first WDM channel port  218 A is configured for optical communication of a first demultiplexed signal. The first multiplexed signal includes the first demultiplexed signal. Step  1608  includes forming a first optical path  414 A including the optical signal router  206 , the first WDM filter  208 A, the second WDM filter  208 B, the first set WDM common port  216 A, and/or the first set first WDM channel port  218 A. 
     Step  1610  includes positioning a second set WDM common port  216 B relative to the optical signal router  206 . The second set WDM common port  216 B is configured for optical communication of a second multiplexed signal. Step  1612  includes positioning a second set first WDM channel port  218 B relative to the optical signal router  206 . The second set first WDM channel port  218 B is configured for optical communication of a second demultiplexed signal. The second multiplexed signal includes the second demultiplexed signal. Step  1614  includes forming a second optical path  414 B including the optical signal router  206 , the first WDM filter  208 A, the second WDM filter  208 B, the second set WDM common port  216 B, and/or the second set first WDM channel port  218 B. 
     Step  1616  includes positioning a first set second channel port  220 A relative to the optical signal router  206 . The first set second channel port  220 A is configured for optical communication of a third demultiplexed signal. The first multiplexed signal further includes the third demultiplexed signal. Step  1618  includes forming a third optical path  414 C comprising the optical signal router  206 , the first WDM filter  208 A, the second WDM filter  208 B, the first set WDM common port  216 A, and/or the first set second channel port  220 A. 
     Step  1620  includes positioning a second set second channel port  220 B relative to the optical signal router  206 . The second set second channel port  220 B is configured for optical communication of a fourth demultiplexed signal. The second multiplexed signal further includes the fourth demultiplexed signal. Step  1622  includes forming a fourth optical path  414 D comprising the optical signal router  206 , the first WDM filter  208 A, the second WDM filter  208 B, the second set WDM common port  216 B, and/or a second set second channel port  220 B. 
     Many modifications and other embodiments of the embodiments set forth herein will come to mind to one skilled in the art to which the embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the description and claims are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. It is intended that the embodiments cover the modifications and variations of the embodiments provided they come within the scope of the appended claims and their equivalents. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.