Abstract:
New methods of manufacture are disclosed for producing side-polished fiber-optic apparatuses, for use both singly and in compact arrays. These new methods involve process steps, many of which operate on many apparatus units simultaneously, with little additional manual labor over what is required to produce one unit at a time. High level assemblies of these fiber-optic apparatuses are also disclosed as compact arrays that not only save space but allow for easy interconnection. Examples of apparatuses that can be made with the disclosed integrated side-polished fiber-optic technology include, but aren&#39;t limited to, couplers, multiplexers, taps, splitters, joiners, filters, modulators and switches. By interconnecting elements within compact integrated arrays of these apparatuses, complicated photonic circuits can be readily constructed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Division of prior application Ser. No. 09/837,325, filed 18 Apr. 2001. A co-pending application of that prior Application, entitled “Structures and Methods for Aligning Fibers”, having application Ser. No. 09/825,821, filed 4 Apr. 2001, and since issued as U.S. Pat. No. 6,516,131, is incorporated herein. 

   FEDERALLY SPONSORED RESEARCH 
   Not Applicable 
   SEQUENCE LISTING OR PROGRAM 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   This invention generally pertains to methods for adding process integration to the manufacture of fiber-optic apparatuses implemented with side-polished fiber optics. This invention also pertains to integrated apparatuses made from these methods of manufacture. 
   There is no prior art method or apparatus published, or on the market, for fully utilizing the advantages of integrated processes with silicon to manufacture side-polished fiber-optic apparatuses and systems, other than the photomasking of multiple features such as grooves, or the deposition of coatings. What is known in the prior art deals with individually placing fibers in grooves, one-at-a-time. Once placed they may all be polished in one step. This prior art is limited to the manufacture of side-polished fibers to implement two-port photonic functions. This known art is taught in the U.S. Pat. No. 5,781,675 “Method for preparing fiber-optic polarizer” and U.S. Pat. No. 5,809,188 “Tunable optical filter or reflector”, both by Tseng. In those patents, Tseng teaches the use of a set of parallel and variable-depth V-grooves etched in a common silicon crystal substrate to simultaneously achieve both a) precise control of remaining side-wall thickness left on each fiber held within each of the V-grooves, b) arcuate paths for the fibers which enable the side-polished regions to be of a controlled length, and c) simultaneous deposition of one or more films on the set of side-polished regions. Not taught in the above patents are multi-function apparatuses or methods for manufacturing multiple apparatuses on a common fiber without fuse splicing or physical connectors. Also not disclosed are a) methods or apparatuses for fabricating multiple units simultaneously, other than the substrates themselves or 2-port polarizers or filters; b) methods or apparatuses wherein some multiples of individual apparatuses are formed with at least one fiber in common; or c) any methods or apparatuses for fiber-to-fiber alignment when coupling side-polished areas to one another between fibers in respectively different substrates. 
   Earlier art teaches side-polished fiber optics made by retaining the fiber within a groove cut into the surface of a non-crystalline material such as glass or quartz. This art can be found in such U.S. patents as U.S. Pat. No. 4,493,528 “Fiber-optic directional coupler”, U.S. Pat. No. 4,536,058 “Method of manufacturing a fiber-optic directional coupler”, U.S. Pat. No. 4,556,279 “Passive fiber-optic multiplexer”, U.S. Pat. No. 4,564,262 “Fiber-optic directional coupler”, U.S. Pat. No. 4,601,541 “Fiber-optic directional coupler”, U.S. Pat. No. 6,011,881 “Fiber-optic tunable filter”, all by Shaw. This art also teaches the requirement of one side-polished fiber along side of a second side-polished fiber, but fails to disclose any means of mechanical self-alignment. 
   Earlier art also includes apparatuses and methods of aligning optical components using constant-depth V-grooves in the surfaces of silicon substrates. Three examples include U.S. Pat. No. 5,633,968 “Face-lock interconnection means for optical fibers and other optical components and manufacturing methods of the same” by Sheem, U.S. Pat. No. 4,475,790 “Fiber-optic coupler” by Little, and U.S. Pat. No. 4,802,727 “Positioning optical components and waveguides” by Stanley. Another U.S. patent, U.S. Pat. No. 4,688,882 “Optical contact evanescent wave fiber-optic coupler” by Failes, not only references some of the earliest work of constructing substrate-supported, side-polished, fiber-optic apparatuses, but also describes some of the limitations involved. This patent by Failes teaches a method of achieving a fused coupling between side-coupled fibers that doesn&#39;t require the index-matching coupling fluid of previous works. Failes did not offer any approaches to precisely and rigidly support the fibers through intimate contact with respective hard substrates. 
   Another relevant prior art is that of U.S. Pat. No. 5,187,760 “Wavelength selective coupler for high power optical communications” by Huber. This patent references little of the above prior art, and is evidently what is called a “non-enabling” patent because it does not provide the reader with information on how to practically implement the structures described and claimed. It describes the use of gratings with which to couple light within a wavelength band between a first fiber and a second fiber. In fact it also describes doing this at more than a single location along the length of the second fiber, wherein the multiple first fibers have respective gratings with different wavelength bands. What is needed is a practicable way in which to implement such structures and apparatuses successfully. 
   Additional prior art on positioning of fiber optics on substrates is found in the technology of Microelectronic Mechanical Systems (MEMS). One reference to such technology is that of “MEMS Packaging for Micro Mirror Switches”, by L. S. Huang, S. S. Lee, E. Motamedi, M. C. Wu, and C. J. Kim, Proc. 48th Electronic Components &amp; Technology Conference, Seattle, Wash., May 1998, pp. 592–597. 
   None of the above art, with the exception of a co-pending application entitled “Structures and Methods for Aligning Fibers”, by Tullis, now issued as U.S. Pat. No. 6,516,131, teaches methods or apparatuses for facilitating the placement of an array of fibers into an array of grooves of width comparable to the diameter of the fiber. 
   Practicable methods and apparatuses are needed to achieve simultaneous assembly of fibers into precision grooves in supporting substrates. 
   The current invention goes beyond one-at-a-time fabrication and introduces process integration methods by which to greatly reduce the cost of manufacturing side-polished fiber-optic apparatuses. Furthermore, the current invention makes possible the integration of compact arrays of side-polished apparatuses that can be used to implement high levels of function integration. And not all of the multiple apparatuses manufactured on a common substrate need be of the same type. 
   BRIEF SUMMARY OF THE INVENTION 
   Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods and apparatuses and combinations particularly pointed out in the appended claims. 
   The objects of the invention are primarily twofold. One object is to provide new methods for low-cost manufacture of side-polished fiber optics, for use both singly and in compact arrays. These new methods involve process steps, many of which operate on many apparatus units simultaneously, with little additional manual labor over what is required to produce one unit at a time. The other primary object is to create high level assemblies of these fiber-optic apparatuses in compact arrays that not only save space but also allow for easy interconnection. Examples of apparatuses that can be made with the disclosed integrated side-polished fiber-optic technology include optical pass-throughs, attenuators, polarizers, couplers, multiplexers, taps, splitters, joiners, filters, modulators and switches. By interconnecting elements within compact integrated arrays of these apparatuses, complicated photonic circuits can be readily constructed, examples of which include a many-to-one multiplexer, a one-to-many demultiplexer and cross-point switch arrays. The reader will readily appreciate the novel methods and structures used to realize manufacturable fiber-optic apparatuses and circuits for performing needed all-fiber photonic functions. 
   These and other objects of the invention are provided by a novel use of combining integrated manufacturing methods used in the semiconductor electronics field with silicon-based side-polished fiber-optic technology. Whole silicon wafers (or wafers of other suitable cubic crystal materials such as Ga—As or Lithium Niobate) are patterned and etched to construct V-grooves at many sites simultaneously in a single masking and etching process level. Then rows of these sites are diced and separated leaving multiple sites within each row or silicon strip. Then parallel fibers are installed and bonded into the V-grooves within a strip, and the side-polishing step is performed on all the fibers within a row or strip in a single polishing operation. Following the polishing step, additional steps can be performed on the side-polished areas to create a range of 2-port apparatuses from the group including an optical pass-through, an attenuator, a polarizer, a filter, a modulator, and a switch. These strips of 2-port apparatuses can then be diced into separate smaller strips, individual fiber units, or left intact as complete arrays. These 2-port strips or individual units can be combined in pairs to form strips or individual units of 4-port apparatuses. And the strips of 2 or 4-port apparatuses can be stacked into 2-dimensional arrays. Within a strip or stack of strips, the individual 2-port and/or 4-port apparatuses can be connected in series and/or parallel to create compact optical circuits. 
   By using fiber-core gratings and/or surface gratings in regions of the side-polished areas and coiling a fiber around to loop through one adjacent V-groove per cycle along a strip, compact multi-channel optical add-drop multiplexers (OADMs) are easily constructed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG. 1  shows how varying the widths of face-to-face grooves, and alignment with a sliding, even slightly rotatable, fiber key, can facilitate the tuning of coupling efficiency in a 4-port fiber optic made with side-polished fibers. 
       FIG. 2  shows steps along a process for fabricating a freestanding 4-port coupler. Various contiguous steps of this process also form, with some slight modifications, alternative processes. These alternative processes can be used to fabricate the following: i) a 4-port coupler with a single substrate; ii) a 4-port coupler sandwiched between two substrates; iii) a 4-port coupler sandwiched between two substrates with one of these substrates serving as a small protective cover; iv) a free-standing half-coupler; and v) a half-coupler within a single substrate. 
       FIG. 3  shows three views of a substrate having variable width and depth V-grooves for holding fibers to be side-polished. Also shown are constant-width V-grooves, between the variable width and depth V-grooves. These constant-width V-grooves are for reducing the planar surface area of the substrate and for providing pathways for air or other gas to enter to facilitate parting of the two substrates as needed. 
       FIG. 4  depicts a method by which to produce strips of substrate-bound fibers, each fiber having substantial lead-length at either one or both ends. 
       FIG. 5  shows a method and means by which to align and place an array of fibers within an array of grooves within a common substrate formed as a strip, to form a strip of half-couplers. 
       FIG. 6  shows a method and means by which to form a strip of 4-port couplers. 
       FIG. 7  shows a method and means by which, using substrates with fiber-alignment grooves, to form a free-standing 4-port coupler, and having the option to reuse the substrates. 
       FIG. 8  shows a method and means by which to form a multi-channel optical add-drop multiplexer from both a first strip of half-couplers and a second strip of half-couplers, wherein the second strip has a common fiber wrapped in recirculating loops through the strip. Either one or both fibers at each coupling region between two side-polished areas would have a core-based or surface-based, wavelength-selective grating. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Having summarized various aspects of the present invention, reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims. 
   Reference is now made to  FIG. 1 , which consists of two parts,  FIG. 1A  and  FIG. 1B .  FIG. 1  shows art presented and claimed in U.S. Pat. No. 6,516,131, by Tullis, titled “Structures and Methods for Aligning Fibers”.  FIG. 1  shows how varying the widths of face-to-face grooves, as well as alignment with a sliding fiber key, can facilitate the tuning of coupling efficiency between two fibers within a 4-port apparatus. This apparatus can be any of the group including couplers, add-drop multiplexers, taps, splitters, joiners, filters, modulators and switches. This tuning is accomplished by adjusting the interaction length between two evanescently coupled fibers. Although only a single 4-port apparatus is shown, one can easily envision multiple 4-port apparatuses constructed side-by-side within the same two substrates. And additional alignment grooves and their keying fibers may also be included. 
     FIG. 1A  shows a tunable 4-port fiber-optic apparatus  1 , such as a coupler or add-drop multiplexer. This 4-port apparatus  1  is comprised of two half-couplers  2  and  3  comprised in turn of respective side-polished fibers  4  and  5  installed within respective varying-width V-grooves  6  and  7  etched into 100 crystal surfaces  8  and  9  respectively (shown face-to-face) of respective substrates  10  and  11 . The two substrates can be slid over one another in the direction parallel to the long axes (not shown) of the two side-polished areas  12  and  13 . The two side-polished areas  12  and  13  are shown at a position where they overlap one another. The side-polished areas  12  and  13  of the fibers  4  and  5  have an elliptical shape with long axes parallel to the groove axes (not shown). The arrows  14  and  15  indicate the direction of motion desired. The apparatus  1  is additionally comprised of a third fiber  16 . Fiber  16  is in a bi-directionally tapered channel  17  constructed of two additional varying-width V-grooves  18  and  19  etched into the surfaces  8  and  9 , parallel to grooves  6  and  7  but offset from them. Fiber  16  serves as an alignment key within this channel  17 , but allows for the motion described with which to tune the coupling ratio and efficiency of the 4-port assembly. By eliminating any linear portion to the channel  17 , the two half-couplers  2  and  3  may be allowed some rotation which is easy to control with the substrates being of a significant scale larger than the side-polished areas, but remain well aligned in the direction of offset just described. Yet another advantage of the bi-directionally tapered channels  17  and that formed by grooves  6  and  7 , is that the fibers  16 ,  4  and  5  will experience less chance to be bent and strained entering or leaving the channel  17  than were it of constant cross-section. The taper at the ends of these channels can be accentuated to help achieve additional avoidance of strain on the fibers  16 ,  4  and  5  from otherwise being bent about a sharp edge. It is important in high-bandwidth fiber-optic applications, such as in modern data- and telecommunications networks, to avoid straining fibers. This is because strain induces birefringence in the fiber and this causes polarization mode-dispersion that can result in high bit-error-rates. 
     FIG. 1B  shows an end-view of the apparatus illustrated in  FIG. 1A  with all similar parts identified by the same numbers, except the view is as though the fibers  16 ,  4  and  5  were terminated at the midpoints of the channels. In addition, the cores  20  and  21  to fibers  4  and  5  are depicted as shaded disks or spots. Note how in this view, one can see the interface between the two side-polished areas  12  and  13  as the region of contact between them. And one can perceive how the side-polish has allowed the cores  20  and  21  of the two fibers  4  and  5  to lie closer to one another to cause better evanescent coupling of light waves between the two cores  20  and  21 . 
     FIG. 2  consists of a sequence of nine parts,  FIG. 2A  through  FIG. 2I . What are shown are steps along a process. Various contiguous steps depict portions of the process. Some of these process portions also comprise methods of the current invention.  FIGS. 2A through 2B  depicts a first portion of the process.  FIGS. 2C through 2F  depicts a second portion of the process.  FIGS. 2G and 2H  depict a third portion of the process, and  FIG. 2I  depicts the last portion of the process. The complete sequence  FIGS. 2A through 2I  also comprises a method of the invention. 
   The first portion of the process includes those steps illustrated in  FIG. 2A  through  FIG. 2C . This first portion of the process is analogous to certain basic steps disclosed in the U.S. Pat. No. 15,809,188 “Tunable optical filter or reflector” and U.S. Pat. No. 25,781,675 “Method for preparing fiber-optic polarizer”, both by Tseng. 
   In this first portion of the process, the first step, as represented in  FIG. 2A , is the marshalling of a fiber  30  together with a substrate  31 , wherein the substrate  30  contains an etched groove  32  having an arcuate depth profile along its length across one of its surfaces  33 . 
     FIG. 2B  then shows that the fiber  30  is placed within the groove  32  in the substrate  31 , wherein the depth of the groove at its shallowest point positions the fiber  30  such that a portion of the side-wall  34  remains above the surface  33 . To accomplish this placement of the fiber  30  within the groove  32 , intermediate steps (not shown) may use methods and apparatuses as are disclosed in U.S. Pat. No. 6,516,131, by Tullis, titled “Structures and Methods for Aligning Fibers”. In the current invention, however, dissolvable or meltable bonding materials (used as tacking materials) or other suitable bonding materials  35  and  36  are placed under and over the fiber  30  as depicted with shading in regions  37 ,  38 , and  39 . These tacking materials  35  and  36  are used to hold the fiber  30  in place for the subsequent polishing step whose results are illustrated in  FIG. 2C . The materials  35  and  36  may be different from one another, or they may be the same. 
   In  FIG. 2C , the sidewall portion  34  of the fiber  30  (shown in  FIG. 2B ) is polished away and is therefore not shown, leaving the same fiber now as a side-polished fiber  42 . The exposed sidewall  41  of the side-polished fiber  42  is now shown instead, and the identifying number of the fiber has been changed accordingly from  30  to  42  in this and the subsequent figures. All other identifiable elements of  FIG. 2C  are the same as in  FIG. 2B . 
   Thus the steps of figures  FIGS. 2A through 2C  accomplish the making of what we will call here a first half-coupler  40 , or substrate-supported half-coupler, as shown in  FIG. 2C . One aspect of the current invention, over the previously disclosed art found within the above cited U.S. patents by Tseng, is that the bonding material  35  and  36  used here need not be wicked into place from the ends of the groove  32 . Also, for subsequent method steps to be described below, the material  35  and  36  can be chosen to be dissolvable, meltable, or otherwise removable, with a minimum of disturbance to the side-polished fiber  42  within the associated groove  32 . If at this point (shown in  FIG. 2C ) the bonding material was to be removed (not shown), it would allow removal (not shown) of the side-polished fiber  42  from the substrate  31  to create what we will call here a free-standing half-coupler (not shown). A free-standing half-coupler is one that is free of any substrate  31 . 
   In the second portion of the process, figures  FIGS. 2D through 2F  show the making of a bond-substituted half-coupler. In the bond-substituted half-coupler, the bonding material  36  (see  FIG. 2B ) is first removed. Then the bonding material  35  (see  FIG. 2B ) is replaced by intermediate bonding material  46  (see  FIG. 2E ) such that there will be little or no bonding material in the region  34  of side-polish  41  (See also  FIGS. 2D ,  2 B, and  2 C). 
     FIG. 2D  shows that after the removal of material  36  (see  FIG. 2B ) from the region  34 , a holding block  43  is used to press firmly against the sidewall  41  of the side-polished fiber  42  and the substrate surface  33 . With the side-polished fiber  42  being held firmly within the groove  32 , at least within the region  34  of the sidewall  41 , the bonding material  35  (see  FIG. 2B ) is removed with a minimum of disturbance to the side-polished fiber  42  in the groove  32 . 
     FIG. 2E  shows the next step of bonding the end portions  44  and  45  with replacement bonding material  46 . This replacement bonding material  46  should be of a type that can be easily removed later with a minimum of disturbance to the fiber  42 . Before the bonding material hardens, all of the surface  33  must be wiped clean. Thus in  FIG. 2E , with the exception of the holding block  43 , we see depicted a finished bond-substituted half-coupler  47 . 
     FIG. 2F  shows two such bond-substituted half-couplers  47  and  48  placed face to face but not yet brought together into intimate contact with one another. 
   In the third portion of the process, figures  FIGS. 2G and 2H  show the bonding of two side-polished fibers together, with as little bonding together of the substrates as possible. 
   In  FIG. 2G , the two bond-substituted half-couplers  47  and  48  of  FIG. 2F  are shown again. A small amount of permanent bonding material is placed on the side-polished surface  41  of the fiber  42  of a first bond-substituted half-coupler  47 . 
   In  FIG. 2H , the side-polished surface  51  of the fiber  54  in the second bond-substituted half-coupler  48  is aligned opposite to and facing the side-polished surface  41  of the fiber  42  in the first bond-substituted half-coupler  47 . The two bond-substituted half-couplers  47  and  48  are brought together, maintaining the described alignment, to spread the permanent bonding material  49  (see  FIG. 2G ) out into a thin film  50  between the two said side-polished surfaces  41  and  51 . The amount of permanent bonding material ( 49  in  FIG. 2G and 50  in  FIG. 2H ) used for this process step should be chosen to minimize or preferably prevent it from spreading over the substrate surfaces  52  and  33  of the bond-substituted half-couplers  47  and  48 . Also, a thin film of release agent (not shown) may be applied to the substrate surfaces  33  and  52  prior to applying the permanent bonding material  49  (see  FIG. 2G ). One technique with which to help minimize or eliminate this unwanted spreading will be described in reference to  FIG. 2I  below and to  FIG. 3  below and provides recesses to prevent the spreading of excess permanent bonding material. 
   Within the step depicted by  FIG. 2H , the permanent bonding material ( 49  in  FIG. 2G and 50  in  FIG. 2H ) may be chosen to be a UV-curable cement, in which case it may be cured by directing UV light  53  into one or more of the fiber ends. (“Light” is defined within this specification and the claims to follow to include invisible electromagnetic radiation.) For example this light  53  may be directed axially into the fiber core (not shown) through the end-face  55  of the fiber  54 . UV light may also be directed into the cladding (not shown) of the fiber  54  as depicted by beams  56  and  57 . Because fibers used for low-loss transmission of near infra-red light, are poor transmitters of UV light, an alternative means of delivering the UV light to cure the UV-curable material  50  is by way of an alternative path. Such a path to the bonding site between the two side-polished areas  41  and  51  can be provided (not illustrated here) with one or two pre-etched extra grooves in the surfaces  33  and/or  52  of the substrates  47  and  48 , running obliquely or approximately perpendicular to the fibers  42  and  54 . These extra grooves may be used as an open path for UV-light or to hold a short fiber or quartz fiber by which to deliver UV-light. 
   The last portion of the process is depicted by  FIG. 2I .  FIG. 2I  shows the substrates  31  and  58  parted, leaving a freestanding, bonded 4-port coupler  59 . What is not shown is that prior to parting the two substrates  31  and  58 , the replacement bonding material holding the end portions of the fibers  42  and  54  into place in their respective substrates  31  and  58  is first loosened by a solvent or by heating. As a freestanding 4-port coupler  59 , its two fibers  42  and  54  are now affixed together but free of the substrates  31  and  58 . Note that the substrates  31  and  58  may now be reused to make yet another such apparatus. This potential reuse of the silicon substrates can significantly lower the cost of producing 4-port couplers. 
   It should be noted that although the above process is described with respect to the formation of a 4-port coupler, other 4-port (or 3-port) fiber-optic apparatuses can be formed with additional steps to make any of the group including couplers, add-drop multiplexers, taps, splitters, joiners, filters, modulators or switches. For example, the core of the fibers used, in the region of side-polish, can be fiber Bragg gratings, as known in the art. Or one or more films can be deposited on one or more side-polished areas, wherein such one or more films could contain Bragg gratings. Or one or more films deposited or sandwiched between the side-polished areas of two fibers could be an electro-active polymer complete with embedded electrodes for connecting to external drive circuitry. 
     FIG. 3  shows one technique of this invention by which to better enable the easy parting (see  FIG. 2H ) of the two substrates  31  and  58  from the freestanding coupler  58  described in the previous paragraph. This technique is the use of extra grooves to minimize the surface area of the substrate areas  33  and  52  (see  FIG. 3H ) in contact with one another. These extra grooves provide paths for air to enter the space between the two surfaces as they are drawn apart. They also provide a means by which to insert a pointed object with which to help force the substrate surfaces apart or to force air between these surfaces.  FIG. 3  shows examples of such extra grooves. 
   In  FIG. 3 , a substrate  70  is shown in a plan view  71 , a side-view  72 , and an end-view  73 . Two arcuate grooves  74  and  75  are shown, and three straight grooves  76 , 77 , and  78  are shown, in an alternating sequence within surface  81 . All the grooves  75  through  78  are parallel to one another. Preferably, the widths and depths of the straight grooves  76 ,  77 , and  78  are equal to or larger than the widths of the arcuate grooves  74  and  75  where the arcuate grooves  74  and  75  reach the ends  79  and  80  of the substrate  70 . The surface area left un-etched  81  between these grooves should be minimized in order to facilitate the parting of substrates ( 31  and  58  in  FIG. 2I ) placed with these faces ( 31  and  52  in  FIG. 2I ;  81  on the substrate illustrated in  FIG. 3 ) touching one another. The substrate  70  illustrated would be able to accept two fibers, one in each arcuate groove. A linear array of more numerous arcuate grooves can be etched into a common substrate, with one or more extra grooves (illustrated as straight grooves in  FIG. 3 ) interleaved between them, but only two arcuate grooves and three extra grooves are illustrated in  FIG. 3  for drawing simplicity. As was discussed above, the purpose of the extra grooves is at least two-fold. One such purpose is to act as a barrier against spreading of permanent bonding material when fabricating a freestanding coupler. Another such purpose is to provide air access channels when parting two such surfaces that have been put face-to-face against one another. 
   The method portions described by  FIG. 2  ( FIG. 2A  through  FIG. 2I ) were described in four sequential portions, each comprised of one or more illustrated steps. All together they describe a method for manufacturing a freestanding 4-port coupler. However, subsets of these illustrated steps, some with minor modifications, describe processes themselves that can produce alternative product results. For example, eliminating  2 D through  2 F, and in  2 G placing sufficient material on both the side-polished areas and the substrate surfaces (without using any release agents on these surfaces, to bond both the side-polished areas and the rest of the substrates, produces a 4-port coupler with substrates intact. In this case all bonding may be of a permanent nature and of the same type. Also, in this case, the process would not include the separating of the two substrates illustrated in  FIG. 2I . 
     FIG. 2A  through  FIG. 2C  describes the construction of a half-coupler  40  supported by a substrate  31 . Again the bonding materials used may be of a permanent nature and all of the same type. 
   It is easy for one skilled in the art to see that  FIGS. 2A through 2C , followed by a  FIG. 2D  without the use of the holding block  43 , can produce a freestanding half-coupler as just the fiber  42  with its side-polished area  41 . 
   A 4-port coupler supported by only one substrate can be produce by first producing a substrate supported half-coupler, as described two paragraphs above this paragraph, and then also producing a freestanding half-coupler, as described one paragraph above this paragraph. Although more difficult, the freestanding half-coupler could then be positioned and bonded to the substrate-supported half-coupler with their side-polished areas made to substantially contact one another. 
     FIG. 2A  through  FIG. 2H , followed by the removal of only the substrate  58  would also produce a 4-port coupler supported by a single substrate. Again, in this case the bonding material used in the substrate  31  could be of the permanent type such that steps  FIGS. 2D through 2F  could be bypassed for that particular half-coupler component  31 . 
     FIG. 2A  through  FIG. 2C , performed twice with permanent bonding material, would produce two half-couplers with supporting substrates that could be physically positioned face-to-face to produce a 4-port coupler wherein the two face-to-face substrates could be slid over one another for tuning purposes. This tuning is discussed in  FIG. 1 . 
   In the case of face-to-face substrates, one substrate may be made very small compared to the other, wherein the smaller serves as a protective cover in the final product. 
     FIG. 4  shows a process diagram  90  that illustrates how to efficiently mass-produce substrate-terminated fibers or side-polished 2-port half-couplers, while using the same methods as described above for each individual fiber or half-coupler with reference to  FIG. 2 . The substrate-terminated fibers may also be side-polished, or not. A silicon wafer  91  provides substrates (e.g.  92 ) arranged as rows in dicable strips (e.g.  93 ). Each strip can be used to construct an array of substrate-terminated fibers  96  or of half-couplers  101 . An array of substrate-terminated fibers  96  is comprised of an array of fibers  95  and a substrate strip  94 . The substrate-terminated fibers  96  may be side-polished or not. If the array of substrate-terminated fibers  96  is to be side-polished, they can all be side-polished at once in a single polishing step as a complete strip. An array of half-couplers  101  is comprised of an array of fibers  100  and a substrate strip  99 . The array of side-polished fibers  101  can all be side-polished at once in a single polishing step as a complete strip. Once the strips (linear arrays) of substrate-terminated fibers  96  or of half-couplers  101  is completed, they may optionally be diced into individual units ( 97 ,  98 , or  102 ) or left intact as an array. Note that substrate-terminated fibers  96  may be made such as to align the fiber end inside of the boundary of the substrate  97  or aligned with a substrate edge  98 . 
     FIG. 5  shows a means  110 , adapted from U.S. Pat. No. 6,516,131, by Tullis, titled “Structures and Methods for Aligning Fibers”, by which to align and place an array of fibers  111  into an array of substrate grooves  112  within a substrate strip  113 . Referring back to  FIG. 4 , this shows a means by which the arrays of fibers  95  or  100  may be efficiently batch processed to place them into their respective arrays of substrate grooves found within their respective substrate strips  94  and  99 . In  FIG. 5 , two of the fibers of the fiber array  111  are labeled as pair  114 . A corresponding pair of substrate grooves  115  of the array of grooves  112  is also shown. 
     FIG. 5  shows that the array of fibers  111  is initially held in a first common plane (not labeled) by a pair of blocks  117  with its own array of block grooves of constant pitch equal to the pitch of substrate grooves. One pair of block grooves is labeled  118 . 
     FIG. 5  also shows that the array of substrate grooves  112  all lie in a second common plane (not shown) at the surface  116  of the substrate  113 . This planar array of fibers  111  (first common plane) is first held at an angle to the planar array of substrate grooves  112  (second common plane). The array of fibers  111  is then brought into contact with an edge  120  of the substrate  113 , an edge  120  running perpendicular to the length of the substrate grooves  112 . The array of fibers  111  is then drawn along this edge until they drop into the ends of the grooves in the array of substrate grooves  112 , one fiber to each groove. The array of fibers  111  (within the first common plane) are then rotated in the directions  121  and  122  toward the common plane of the substrate grooves  112  (within the second common plane). The substrate grooves  112  are arcuate in shape, being wider and deeper at the ends then in between and being formed by  111  Miller planes from a  100  surface of a cubic crystal such as silicon. 
   Still referring to  FIG. 5 , as each individual fiber of the array of fibers  111  is guided by the sloped sides and curvatures of the respective individual arcuate grooves in the array of substrate grooves  112 , a tool  123 , such as comprised of a block  124  and a somewhat compliant edge  125 , can be brought downward in the direction indicated by the arrow  126  to press the array of fibers  111  home into their respective places within the array of substrate grooves  112 . As an alternative, the somewhat compliant edge  125  can be brought down against the array of fibers  111  first at the edge  120  of the substrate and then slid toward the midpoint of the grooves as the plane of fibers  111  is rotated toward the plane of the grooves, all along maintaining a slight force against the surface  116  of the substrate. 
   Although not shown in  FIG. 5 , it can easily be envisioned that two or more of the fibers (e.g.  114 ) may be actually uncut segments of a single fiber which is continuous and looped around the substrate  113  to occupy multiple block grooves (e.g.  118 ) and multiple grooves (e.g.  115 ) of the substrate  113 . 
     FIG. 6  shows the batch manufacture  150  of a strip of 4-port fiber-optic couplers  151  from two strips of 2-port half-couplers  152  and  153 . The strips of 2-port half-couplers  152  and  153  can be batch manufactured by the method depicted and described above with reference to  FIG. 4 , including the steps illustrated and described with reference to  FIG. 5 . Note that the substrates for the two strips of half-couplers  152  and  153  come from two rows or strips  154  and  155  batch-fabricated from a common wafer  156  that is diced into strips. The more detailed steps are those described above with reference to  FIG. 2 . 
     FIG. 7  shows an alternative to batch processing in strips. Here, individual die are taken from a batch-processed wafer and used with the methods described above with reference to  FIG. 2 . What is shown is a wafer process  160  beginning with die  161  being taken as individual grooved substrates from a batch processed wafer  162 . Next these die  161  are combined with fibers  163  to produce individual half-couplers  164 . In turn, these half-couplers  164  can be combined in pairs to form individual substrate-supported 4-port couplers  164 . Optionally thereafter, the substrate-supported 4-port couplers  165  can be processed to remove a freestanding 4-port coupler  167  from the substrates  166 . The substrates  166  can then be reused, keeping the material cost in the 4-port couplers  167  to a minimum. 
     FIG. 8  shows the manufacture  170  of a multi-channel optical add-drop multiplexer  171  (OADM). Many other apparatuses, such as a one-to-many power splitter, can be created using a similar structure. This add-drop multiplexer  171  is made from a first strip of half-couplers  172  and a second strip of half-couplers  173 . The fiber  174  used in this second strip is a single fiber and runs in loops to pass once through each of the individual grooves of the substrate strip  175 . Preferably, the loops formed by the fiber  174 , together with the plane of the substrate  175 , all lie close to a common plane for compactness. The detailed steps of fabrication can be taken from those described and illustrated with reference to  FIG. 2  above. What is formed can be a many-to-one combiner or multiplexer or a one-to-many splitter or demultiplexer. If a demultiplexer is intended, one skilled in the art will know to include a grating within the fiber at the region of the side-polish and/or between the two side-polished areas of the two fibers comprising the 4-port apparatus. With the addition of a film or slice of an electro-optically or thermally active material (for example a suitable polymer or crystal), sandwiched within the interface between the two side-polished areas of the fibers, switching arrays can be formed in a similar manner to the above. By stacking multiple units of the OADM strip structure described, compact assemblies can be achieved from which to implement optical functions having many channels or cross-points. 
   Although the invention is described with respect to preferred embodiments, modifications thereto will be apparent to those skilled in the art. Examples may include the addition of one or more fiber-core Bragg gratings near to the side-polished area(s), or within an interface between two side-polished areas, converting what would each otherwise be a coupler to an optical add-drop multiplexer OADM. Another example would be the addition of a film, thin slice, or deposited layer (such as of an electro-optically active material or thermally active material) within the interface between side-polished areas, converting what would otherwise be a passive apparatus into an active apparatus such as a modulator or optical switch, even a wavelength selective modulator or optical switch. One skilled in the art of cross-point array switches can see how the disclosed apparatuses can be coupled to create optical switch arrays. And one skilled in the art of variable attenuators can see how the disclosed apparatuses can be used as variable attenuators by having an electro-active or thermally active film or slice of material in the interface between side-polished areas. Therefore, the scope of the invention is to be determined by reference to the claims that follow.