Abstract:
A dust cap assembly comprising a sleeve and a sealant that seals a fiber optic ferrule from contaminants and, upon removal, provides remedial cleaning of any foreign matter present on the ferrule when the dust cap assembly was initially installed. Further, the sealant has advantageous mechanical and optical properties such that the interaction of the sealant, the sleeve and the fiber optic ferrule defines a convex shape. The dust cap assembly may therefore function as a terminator that reduces back reflection during testing.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. Nos. 61/182,379 and 61/182,361 both filed on May 29, 2009, the entire contents of both which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to dust cap assemblies for fiber optic ferules used in fiber optic connectors. Specifically, the dust cap assembly seals the fiber optic ferrule from contaminants during its incumbency and, upon removal, provides remedial cleaning of any foreign matter present on the ferrule when the dust cap assembly was initially installed. Additionally, the dust cap assembly functions as a terminator that reduces back reflection for testing the integrity of an optical cable assembly or as enabling a non-contact continuity test for fiber optic patch cables. 
     2. Technical Background 
     The capacity to send information over a wire revolutionized communication. Copper wire was the standard for more than 150 years, with ease of use and interconnection, but as bandwidth demand increased, it was necessary to seek alternative mediums. Optical fiber, developed and perfected over the past three decades, has made its presence felt, providing secure, high capacity signal transmission; in the past used primarily for long distance signal transmission due to its tremendous efficiency and security, but unable to easily leverage these attributes in more localized arenas. With developments in the joining of truncated fibers, suddenly optical fiber was becoming as versatile as copper. Optical fiber could be cut and easily rejoined via splicing, either by laser, electric arc or mechanical splicing, and by other mechanical processes. Of the mechanical processes developed, the ability to mate and de-mate an optical fiber to another optical fiber completed the versatility picture. Fiber optic ferrules and fiber optic connectors provided easy junction points in the field that tremendously increased the ease of use of optical fibers. Polishing optical fibers within appropriate ferrules is necessary to efficiently join two fibers end to end in such a way as to preserve the integrity of the optical signal with as little signal loss (attenuation) as possible. 
     To create a typical fiber optic cable assembly a fiber optic cable is terminated, a fiber optic connector is assembled at an end of the cable and the ferrule end face polished. The exactitude of the polished face of a fiber optic ferrule is such that any minute amounts of debris on that end face can block or decrease signal transmission or even damage the end face. Polished ferrule end faces can represent the end result of hours of manufacturing providing a polished ferrule end face to mate to another polished ferrule end face and thereby transfer signals from one fiber into another. Protecting the polished end faces of fiber optic ferrules is extremely important: protection from residual dust from the connector housing; protection from airborn contaminants in the manufacturing facility; protection from the effects of water, oils and chemicals; protection from the effects of temperature cycling, just to name a few. Dust caps as known in the art provide a shield from the physical contact of the delicate ferrule end faces with the outside environment, but do not inherently prevent ingress of moisture, remediate existing contaminants, and can actually deposit contaminants onto the very ferrule end faces they are designed to protect. Thus, there is an unresolved need for dust cap assemblies that will literally seal the optical ferrule end face, insuring the integrity of the factory polished ferrule, one that is inexpensive, easy to install and remove, and that prevents contamination by water, oil, dust, particulates, damage due to handling, etc. 
     SUMMARY 
     The disclosure refers generally to a dust cap assembly for a fiber optic connector and methods for making the same. Specifically, the dust cap assembly physically engages and seals a polished fiber optic ferrule, thereby preserving the cleanliness of the fiber optic ferrule end face. The dust cap assembly comprises at least two components: a sleeve and a sealant. The sleeve has a through bore that physically engages the fiber optic ferrule by a frictional fit. A distal end of the sleeve may include an encapsulating feature that provides a suitable application point for the sealant. The distal end is proximal to the fiber optic ferrule end face, thereby allowing application of the sealant to the encapsulating feature of the sleeve and the fiber optic ferrule end face at the same time. 
     In one embodiment, the sealant comprises a curable liquid polymer, wherein the curable liquid polymer is easily applied and generally conforms to the geometry present on the distal end of the sleeve and the fiber optic ferrule end face. The sealant transitions from liquid to solid upon curing, encapsulating the fiber optic ferrule end face and protecting it from contaminants such as water, oils, dust, particulates, etc., thereby ensuring the integrity of the polished fiber optic ferrule end face. 
     In the event that contaminants are present prior to the application of the sealant, the sealant will adhere to such contaminants and lock them in the polymer upon curing. The contaminants, locked in the cured sealant, will come away with the dust cap assembly when the craft removes it from the fiber optic ferrule, leaving a fiber optic ferrule end face surface that may be cleaner than before the dust cap assembly was installed. 
     A further advantage of the present disclosure is the interaction of the dust cap assembly and optical testing equipment used by the craft. In one embodiment, the index of refraction of the cured sealant allows the dust cap assembly to act as a terminator so that the craft can remotely test the optical integrity of an optical system after the system has been installed. If the dust cap assembly is installed on each end of a cable, as in a fiber optic jumper, the encapsulating convex shape of the index matching sealant serves as a lens, allowing light to enter from an external light source sufficient to travel the length of the cable and exit the opposite dust cap assembly and be detected by a photodetector. This helps the craft to quickly determine continuity within the jumper without having to remove the dust cap assembly or optically connect the jumper cable to either the external light source or the testing apparatus. Removing the dust cap and plugging the ferrule into testing equipment runs the risk of damaging or contaminating the polished fiber optic ferrule end face. 
     The present disclosure provides assurance to the end user that the factory installed, polished fiber optic ferrules remain pristine and in excellent condition for and until their intended use—transmission of optical signals from one optical fiber into another optical fiber. 
     It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the disclosure are illustrated by the accompanying drawings, in which: 
         FIGS. 1A and 1B  show two views of an embodiment of the sleeve of a dust cap assembly; 
         FIGS. 2A and 2B  show two views of another embodiment of a sleeve having a shoulder; 
         FIG. 3A  shows a sectional view of a fiber optic connector with the sleeve installed and  FIG. 3B  shows a sectional view of the same fiber optic connector and sleeve with the sealant in place; 
         FIG. 4A  shows a sectional view of a fiber optic connector with another sleeve installed and  FIG. 4B  shows a sectional view of the same fiber optic connector connector and sleeve with the sealant in place; 
         FIG. 5A  shows a sectional view of a fiber optic connector with another sleeve installed and  FIG. 5B  shows a sectional view of the same fiber optic connector and sleeve with the sealant in place; 
         FIG. 6A  shows a sectional view of a fiber optic connector with another sleeve installed and  FIG. 6B  shows a sectional view of the same fiber optic connector and sleeve with the sealant in place; 
         FIG. 7  shows a multi-fiber fiber optic ferrule assembly with the dust cap assembly installed; 
         FIG. 8  depicts a first method of sealing a fiber optic ferrule end face using a dispensing head to deposit the sealant and then curing the same; 
         FIG. 9  is a second method of sealing a fiber optic ferrule end face by dipping the sleeve and polished end face into the sealant and then curing the same; 
         FIG. 10A  shows an artistic rendering of a “clean” polished end face before application of the dust cap assembly and  FIG. 10B  shows an artistic rendering of the polished end face of  FIG. 10A  after the dust cap assembly was removed; 
         FIG. 11A  shows an artistic rendering of a “dirty” polished end face before application of the dust cap assembly and  FIG. 11B  shows an artistic rendering of the polished end face of  FIG. 10B  after the dust cap assembly was removed 
         FIG. 12  schematically shows a jumper cable assembly with the dust cap assembly on each end during continuity testing; 
         FIG. 13  schematically shows a jumper cable assembly with a first connector optically connected to a test apparatus and a second connector having a dust cap assembly during testing for backreflection; and 
         FIG. 14  shows a fiber optic cable assembly with a trunk cable and tether, the tether having a dust cap assembly acting as a terminator. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts. 
     The disclosure generally relates to a dust cap assembly and methods of making the same. The dust cap assembly comprises at least two components for sealing a polished end face of a fiber optic ferrule of a fiber optic ferrule assembly. Sealing a polished end face of a fiber optic ferrule is advantageous to inhibit encroachment of contaminants on the polished end face from the time the polished end face is polished to the time the fiber optic connector assembly is deployed in the field. Simply stated, the disclosure is directed to a dust cap assembly for sealing a fiber optic connector assembly having at least one fiber optic ferrule assembly including a fiber optic ferrule having at least one optical fiber therein. The sleeve has a proximal end and a distal end with a through bore therebetween and is disposed on the at least one fiber optic ferrule, and a sealant at least partially disposed on the sleeve for sealing a portion of the polished end face of the fiber optic ferrule. 
       FIGS. 1A and 1B  show two different views of a sleeve  10  of the dust cap assembly of the disclosure. In this embodiment, the sleeve  10  is generally straight and has a proximal end  14  and a distal end  16 . The proximal end  14  and distal end  16  have a through bore  12  therebetween, creating a generally hollow component. An encapsulating feature  18  proximal to the distal end  16  is in communication with the through bore  12 , wherein the encapsulating feature  18  enables the sealing of the polished end face of a fiber optic ferrule.  FIGS. 2A and 2B  show two different views of a second embodiment of a sleeve  20 . Sleeve  20  includes a shoulder  22  for easing the removal of the same from the fiber optic ferrule assembly (e.g., the assembly includes a portion of the fiber optic ferrule and the end of the optical fiber). Sleeve  20  also has distal end  16  and proximal end  14  with a through bore  12  therebetween. Encapsulating feature  18  is proximal to distal end  16  and in communication with through bore  12 . 
       FIGS. 3A-B  through  FIGS. 6A-B  show two different sectional views of respective dust cap assemblies  30  disposed on a fiber optic connector  32  (hereinafter “connector”).  FIGS. 3A ,  4 A,  5 A and  6 A show connector  32  having a ferrule  28  with a single fiber  26  and respective embodiments of sleeve  20 . Ferrules include, but are not limited to, LC, SC and MT, utilizing APC, UPC, pencil tips or flat configurations, made of steel, ceramic, polymer or any other suitable ferrule material. Each ferrule  28  has an exposed polished end face  27 , the polished end face  27  having polished fiber face  27 A protruding slightly, but the fiber face  27 A may be flush or recessed. For purposes of this disclosure polished end face  27  and polished end face  27 A are proximal to each other and any further mention of polished end face  27  is meant to include by inference polished fiber face  27 A. However, the concepts of the present application may be used on ferrule assemblies that are not polished, where protection is desired.  FIG. 3A  shows sleeve  20  having an encapsulating feature  18  shaped as a chamfer  24  that extends from the through bore  12  to distal end  16 . In a similar fashion,  FIGS. 4A ,  5 A and  6 A show respective embodiments of dust cap assembly  30 , each having sleeve  20  with different configurations of encapsulating feature  18 . In  FIG. 4A  encapsulating feature  18  is shaped as a radius  40 . In  FIG. 5A , encapsulating feature  18  is shaped as a step  42  and in  FIG. 6A  encapsulating feature  18  is shaped as a lip  44 . Of course, other suitable geometries are possible as the encapsulating feature. Each of respective  FIGS. 3B ,  4 B,  5 B and  6 B show sealant  34  generally covering respective portions of the through bore  12  and encapsulating feature  18 . Sealant  34  is advantageous for sealing the polished end face  27  and is in direct contact with polished end face  27  as well as portions of encapsulating feature  18 . 
       FIG. 7  shows a multi-fiber ferrule assembly  50  having a dust cap assembly employing the concepts disclosed herein. In other words, the dust cap assembly includes a sleeve  48  and sealant  34  for sealing a plurality of polished fiber faces and a portion of polished end face  37  of the multi-fiber ferrule  46 . Multi-fiber ferrule sleeve  48  is generally rectangular, having proximal end  14  and distal end  16  that generally surrounds the end of multi-fiber ferrule assembly  50  as shown. Specifically, sleeve  48  surrounds a portion of multi-fiber ferrule polished end face  37  of multi-fiber ferrule  46 . Multi-fiber ferrule sleeve  48  has a through bore  49  and encapsulating feature  24  shaped as a chamfer, but other geometries are possible. Sealant  34  is in direct contact with chamfer  24  and multi-fiber ferrule polished end face  37 , thereby sealing and protecting the multi-fiber ferrule polished end face  37 . Multi-fiber ferrule assemblies  50  may include guide pins  47  disposed therein for mating with a complementary ferrule assembly. As shown, guide pins  47  are received and protected from encroachment of sealant  34  by guide pin cavities  49 A and  49 B formed in sleeve  48 . The multi-fiber ferrule sleeve  48  shown in  FIG. 7  may have other variations similar to sleeves  10  and  20  of  FIGS. 1-6  such as alternative encapsulating features for receiving the sealant  34  for sealing multi-fiber ferrule polished end face  37 . Other embodiments of the multi-fiber sleeve may have other geometries such as including one or more protrusions for fitting into the guide pin bores of the ferrule if it does not include guide pins. 
     Sleeves  10 ,  20  and  48  of the disclosure may use any suitable material and the bores frictionally engage their respective ferrules, slightly deforming to tightly slide along a medial portion of the respective ferrule. This prevents sealant  34  from wicking down the medial portion of the ferrule, keeping sealant  34  on polished end face  27 . By way of example, the sleeve may be a polymer such as a thermoplastic like polycarbonate and a polyacrylate, though other suitable thermoplastics may be used. 
     Sealant  34  may be any suitable material having the desired properties for sealing and/or optical transmission. In one embodiment, sealant  34  is a curable liquid polymer. The curable liquid polymer starts as a liquid having a viscosity range of generally less than 1000 poise at 23 degrees Celsius, with a preferred range of about 250 poise to about 850 poise at 23 degrees Celsius. This range provides advantageous physical characteristics, e.g., ease of handling, tackiness, and surface tension qualities. For instance, sealant  34  of  FIGS. 3-7  shows a generally convex shape  38  distal from the sealed polished end face  27 , enabled by the surface tension of sealant  34  while in liquid state; however, other shapes for the sealant such as generally flat are possible. Upon curing, sealant  34  retains its geometry and hardens, enabling sealant  34  to fully integrate with respective sleeves  10 ,  20  or  48 . Encapsulating feature  18  is configured in such a way that when dust cap assembly  30  is removed sealant  34  releases sealed polished end face  27 , revealing polished end face  27 . The sealant  34  viscosity range allows sealant  34  to flow sufficiently to fully cover polished end face  27  and encapsulating feature  18 . 
     The curable liquid polymer may be a heat curable liquid polymer, an ultraviolet light curable liquid polymer or a chemically reactive liquid polymer. One preferred embodiment of sealant  34  is an ultraviolet light curable liquid polymer for providing the speed and ease of processing. By way of example, one suitable ultraviolet light curable liquid polymer is a UV acrylate that consists essentially of an aliphatic urethane diacrylate, a difunctional acrylate oligomer, and a photoinitiator. The range of ratios of each ingredient are:
         100 parts aliphatic urethane diacrylate;   0-40 parts difunctional acrylate oligomer; and   2-6 parts photoinitiator,
 
with a preferred ratio being 100 parts aliphatic urethane diacrylate, 10 parts difunctional acrylate oligomer and 3 parts photoinitiator. This ratio of ingredients provides appropriate sealing, viscosity and optical qualities, enabling sealing, cleaning and testing advantages for dust cap assembly  30 .
       

     Additionally, sealant  34  is preferably a hydrophobic polymer, resisting water absorption that can contaminate sealed polished end faces  27 . Water ingress can leave deposits on polished end face  27 , degrading transmission quality of mated fiber optic connectors. Keeping water and oils away from polished end face  27  effectively insures that contaminants are also prevented from contacting polished end face  27 . 
       FIGS. 8 and 9  illustrate two different methods for making the dust cap assemblies disclosed herein. Generally speaking, the methods of sealing a fiber optic ferrule end face includes the steps of: providing a fiber optic connector assembly having at least one fiber optic ferrule assembly therein that includes at least one fiber optic ferrule and at least one optical fiber therein, wherein the fiber optic ferrule has a polished end face thereon; providing a sleeve having a proximal end and a distal end with a through bore therebetween; placing the sleeve onto the fiber optic ferrule via the through bore, whereby the polished end face is proximal to the distal end of the sleeve; and depositing a sealant onto the sleeve to cover a portion of the polished end face of the fiber optic ferrule and a portion of the distal end of the sleeve for sealing the fiber optic ferrule end face. 
     Sleeve  10  is placed onto the ferrule and frictionally engages a medial portion of a ferrule within a fiber optic connector assembly  51 . The sleeve  10  is slid onto the ferrule a suitable distance so that the distal end  16  is proximal to polished end face  27 . Encapsulating feature  18  exposes polished end face  27 , thereby providing a suitable catchment area for the sealant  34  (see  FIGS. 3-7 ). In other words, the distal end  16  may extend beyond the polished end face or be substantially flush with the polished end face  27 . Additionally, polished end face  27  may extend slightly beyond distal end  16 , but polished end face  27  should be proximal to distal end  16 . Sealant  34  is applied by any suitable application means in sufficient quantity to cover both the polished end face  27  and at least a portion of the distal end  16 . If there is an encapsulating feature  18  associated with the distal end  16 , the sealant  34  should cover the polished end face  27  and the encapsulating feature  18 . 
       FIG. 8  specifically illustrates a method of sealing a fiber optic ferrule end face where a plurality of fiber optic ferrule end faces of respective fiber optic connector assemblies  51  are sealed. As shown, fiber optic connector assemblies  51  having sleeves  10  installed are secured to a common connector holder  52  at regular intervals. Thereafter, dispensing head  60  with a plurality of nozzles matching the regular intervals is brought adjacent to the distal end  16  of the respective sleeves. A controlled amount of sealant  34  within dispensing head  60  is deposited out by mechanical, pneumatic, and/or electrical means onto the respective distal ends  16 , covering a portion of distal ends  16  and polished end faces  27  of respective fiber optic connector assemblies  51 . Then, connector holder  52  is moved to a curing station as represented by the arrow. In this embodiment, an ultraviolet light curable polymer sealant is used and an ultraviolet light source  54  for curing the same. A suitable dose and exposure time is selected for ultraviolet light  55 , thereby providing the desired cure as shown. 
       FIG. 9  illustrates another explanatory method of sealing a fiber optic ferrule end face where a plurality of fiber optic ferrule end faces of respective fiber optic connector assemblies  51  are sealed. Like the other method, the plurality of fiber optic connector assemblies  51  having respective sleeves  10  are secured to connector holder  52 . The plurality of fiber optic connector assemblies  51  are inverted and the distal ends  16  of sleeves  10  are brought into contact with the surface of sealant  34 , allowing a small quantity of sealant  34  contained within a suitable container to adhere to the distal end  16  and polished end face  27 . The viscose properties of the sealant  34  will promote even coating on the surfaces. Thereafter, connector holder  52  is reverted until the dust cap assembles  30  point vertically upwards and then moved into proximity of an ultraviolet light source, or other curing means as appropriate. Thereafter, the dust cap assemblies  30  are exposed to a suitable amount of ultraviolet light  55  for curing the sealant. Although the methods discussed disclosed making a plurality of dust cap assemblies at once, the concepts are applicable to making individual dust cap assemblies. 
     Referring to  FIGS. 10A-B  and  11 A-B, one can see the results of sealing polished end face  27  of a ferrule assembly through artistic renderings of actual test samples.  FIG. 10A  shows an artistic rendering of actual clean, newly polished end face  27  and polished fiber face  26 .  FIG. 10B  shows an artistic rendering of actual polished end face  27  of  FIG. 10A  after dust cap assembly  30  was installed and removed. As shown, the polished end faces  27  in both illustrations are clean. In other words, the end face was clean at the time of manufacture and sealing, and retained its clean state when the dust cap assembly was removed. 
       FIG. 11A  shows an artistic rendering of actual polished end face that is contaminated at the time of manufacture such as by dust and the like. Dust cap assembly  30  was installed and  FIG. 11B  shows artistic rendering of the results after dust cap assembly  30  was removed. The same polished end face  27  of  FIG. 11A  is very clean in  FIG. 11B  after removing the dust cap assembly. Simply stated, dust cap assembly  30 , utilizing sealant  34 , is able to remedially clean polished end faces  27 . This is advantageous due to the environmental conditions within a processing facility; dust, pollen, particulate matter, moisture, oils, lint, etc., are usually floating in the air and can stick to polished end face  27 . Dust cap assembly  30  protects polished end face  27  while residing on the ferrule, and further, upon removal, cleans any incidental contaminants present on polished end face  27  at the time of the installation of dust cap assembly  30 . 
     Additionally, the dust cap assembly  30  can provide other functionality. For instance, sealant  34  such as disclosed herein can have advantageous post-cure optical properties. The pre-cure viscosity range allows the sealant to create a convex shape  38  about the sealed polished end face  27 . By way of example, the convex shape  38  may have a tangential contact angle of greater than about 5 degrees and less than about 90 degrees, preferably about 10 degrees. Additionally, the formulation of the sealant may provide a post-cure index of refraction (RI) within the range of between about 1.45 to about 1.48 at 23 degrees Celsius and at a wavelength of 589 nm, most preferably between about 1.460 and about 1.466 at 23 degrees Celsius. At 1310 nm wavelength RI of the cured sealant at 23 degrees Celsius should be about 1.45. This range of RI closely matches most commercial optical fiber and allows the optical signal to travel into the sealant. This RI range also helps the dust cap assembly to withstand very high power levels, as high as 23 dBm for testing as discussed below. 
     Simply stated, the convex shape  38  of the sealant coupled with the preferred RI of the cured sealant  34 , allows light to enter the dust cap assembly with great efficiency since there is no gap between the sealant  34  and polished end face  27  and then escape from the sealant. Illustratively,  FIG. 12  shows a jumper cable assembly  85  with dust cap assemblies  30  installed on both ends. An external light source  80  is proximal to a first dust cap assembly  30  and a photoreceptor  81  is proximal to a second dust cap assembly  30 . Emitted light  57  from the external light source  80  (represented by the arrows) enters the first dust cap assembly  30  and travels along the jumper cable assembly  85  and then exits the second dust cap assembly  30  where it is detected by photoreceptor  81 . This enables a continuity test for jumper cable assembly  85 . Photoreceptor  81  is useful to determine the amount of actual light transmitted, regardless of wavelength. If external light source  80  is a visible light source the photoreceptor  81  may be simply the human eye (not shown). The continuity test advantageously does not require removal of dust cap assemblies  30 , thereby maintaining a pristine end face until the dust cap assemblies are removed for installation of the jumper cable assembly  85 . 
     Other improvements in testing are possible with assemblies using the dust cap assemblies disclosed herein.  FIGS. 13 and 14  use the geometric and optical qualities of dust cap assembly  30  for improving a reflectance test. The reflectance test is useful since it can reveal a lot of useful information to the craft such as the integrity of a cable assembly. An unterminated distal connector (e.g., not connected to another connector, other device, or other means to inhibit backreflection) without the dust cap assembly disclosed herein can be a source of a large backreflection spike. This large spike in reflected signal is detrimental to the quality of light emitting devices such as VCSELs that rely on amplified internal reflections to boost their signal. Backreflected light entering such a light emitting device can cause noise or utterly disrupt the signal. 
     In the past discrete terminators needed to be installed as conventional dust caps did not have the inherent utility of a terminator. Placing an index matching gel, or index matching block was one way to terminate a cable assembly. Mandrel wrapping the cable multiple times to a radius beyond the minimum bend radius of the particular optical fiber was another, causing the light signal to reflect out of the cladding wall instead of being reflected from the end. However, this mandrel wrapping method is not effective with new bend-insensitive optical fibers that direct light along their specialized core almost regardless of bend radius. Thus, another type of terminator is necessary in such cases. Dust cap assembly  30  provides a ready made terminator along with the functionality of sealing, protecting and cleaning the polished end face  27 . 
     Terminating the distal fiber optic connector assembly  71  eliminates the spike in backreflection, causing the light from the light source or test apparatus  83  to pass out of the dust cap assembly  30  as shown in  FIG. 13 . Specifically, the convex shape  38  of the sealant prevents most light from reflecting back into the optical fiber, and by consequence, back to the light source or test apparatus  83 .  FIG. 13  shows a first fiber optic connector assembly  70  of jumper cable assembly  85  optically connected to test apparatus  83 . A second fiber optic connector assembly  71  is not optically connected to any device, but has dust cap assembly  30  installed. Test apparatus  83 , such as an OTDR or the like, sends a pulse of light into jumper cable assembly and takes minute amounts of backreflection and determines the integrity of the fiber optic cable assembly. The dust cap assembly  30  serves as a terminator to prevent the large spike in backreflection commonly associated with light passing from a polished fiber face into air. The amount of backreflection allowed by the dust cap assembly  30  is not more than −50 dB, and in most cases as little as −60 dB.  FIG. 14  shows a cable assembly having a fiber optic trunk cable  90  and a cable access point  91  with a fiber optic tether cable  86  issuing from the cable access point  91 . The distal end of the fiber optic tether cable  86  has fiber optic connector assembly  71 , with dust cap assembly  30  installed. Light from a remote upstream source such as a central office (not shown) or the like can be sent from the fiber optic trunk cable  90 , into the fiber optic tether cable  86  and to the fiber optic connector assembly  71 , to pass out of the dust cap assembly  30 , again greatly reducing the backreflection spike commonly found at the polished fiber face/air interface. 
     The foregoing is a description of various embodiments of the disclosure that are given here by way of example only. Although a dust cap assembly for sealing a fiber optic ferrule according to the disclosure has been described with reference to preferred embodiments and examples thereof, other embodiments and examples may perform similar functions and/or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the appended claims.