Patent Publication Number: US-10768378-B2

Title: Fiber alignment device, ferrule device and method of manufacturing the ferrule device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Stage of PCT/IB2015/054955, filed Jul. 1, 2015, which claims the benefit of Chinese Patent Application No. 201410309266.4 filed on Jul. 1, 2014 in the State Intellectual Property Office of China the disclosures of which are incorporated herein by reference in their entireties. To the extent appropriate a claim of priority is made to each of the above disclosed applications. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a ferrule assembly, a fiber alignment device, a ferrule device and a method of manufacturing the ferrule device. 
     Description of the Related Art 
       FIG. 1 a    is an illustrative view of a single-fiber ferrule assembly (ferrule device)  10  of a fiber optic connector in the prior art; and  FIG. 1 b    is a cross section view of the single-fiber ferrule assembly  10  shown in  FIG. 1   a.    
     As shown in  FIG. 1 a    and  FIG. 1 b   , in the prior art, during manufacturing the single-fiber optic connector, the ferrule assembly  10  comprising a ferrule  12  and a rear seat  11  connected to a rear end of the ferrule  12  is usually used. The rear seat  11  may be a plastic member formed on the rear end of the ferrule  12  by molding, or may be a metal member fixed on the rear end of the ferrule  12  by crimping. 
     As shown in  FIG. 1 a    and  FIG. 1 b   , a hollow chamber  14 , for receiving an adhesive, is formed in the rear seat  11 . An axial front port of the hollow chamber  14  is coaxial and communicated with a fiber bore  15  in the ferrule  12 . During manufacturing the fiber optic connector, an enough adhesive is firstly injected into the hollow chamber  14  through an axial rear port (adhesive injection port)  13  by means of an adhesive injection needle (not shown), then a bared and cleaned fiber of the optical cable is inserted through the hollow chamber  14  and the fiber bore  15 , fully filled with adhesive, of the ferrule assembly  10 , then the adhesive is cured to fix the fiber in the fiber bore  15  of the ferrule assembly  10 , then the ferrule assembly  10  is processed by a series of procedures, such as, grinding, polishing, testing, assembling, etc., and finally, a fiber optic ferrule device (finished ferrule assembly) is obtained. 
     In the prior art, a manufacturing error is unavoidable during manufacturing the ferrule assembly. Furthermore, a personal error may be occurred in size for easily fitting/assembling the ferrule assembly, for example, in order to easily insert the fiber through the fiber bore of the ferrule, the diameter of the fiber bore of the ferrule is formed to be larger than the outer diameter of the fiber, causing a size deviation between the outer diameter of the fiber and the inner diameter of the fiber bore of the ferrule. Thereby, it is likely to occur various errors in the ferrule assembly, for example, a center axis of the fiber is offset from a center axis of the fiber bore of ferrule due to a large gap between the fiber and the fiber bore of the ferrule, a center position of the fiber bore is offset from an ideal center position of the fiber bore determined with reference to an indexing feature, for example, an outer cylinder of a single-fiber ferrule or a guide hole of a multi-fiber ferrule. As a result, an actual center axis of the fiber in the fiber bore of the ferrule may be offset from an ideal center axis of the fiber determined with reference to the indexing feature of the ferrule due to these errors. The above factors may cause an irregular lateral shift of the center axis of the fiber, increase the insertion loss of mating a pair of fiber optic connectors and decrease the optical transmission performance of the fiber optic connectors. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to overcome or alleviate at least one aspect of the above mentioned disadvantages. 
     In order to compensate defects occurred in manufacturing a fiber optic connector in the prior art, the inventor of the present application filed a Chinese application No. CN201310203120.7 (hereafter referred as D1) and a Chinese application No. CN201310203217.8 (hereafter referred as D2) on May 28, 2013 and a Chinese application No. CN201310226442.3 (hereafter referred as D3) and a Chinese application No. CN201310226188.7 (hereafter referred as D4) on Jun. 7, 2013. In these Chinese applications, there are proposed solutions to produce a fiber optic connector with high precision, low insertion loss and low cost by a low precision ferrule, of which a diameter of a fiber bore is far larger than that of a fiber, and an error of the center of the fiber bore with respect to an ideal center is very large. The whole disclosures of these Chinese applications are incorporated herein by reference. 
     Based on the Chinese applications D1˜D4, the present invention discloses an improved fiber alignment device capable of positioning a fiber in a low precision ferrule with high precision and adjusting an eccentricity orientation of the fiber to a predetermined orientation. Thereby, during mating a pair of fiber optic connectors having the ferrules, it may simply locate the eccentricity orientations of the pair of fiber optic connectors in the same fiber core adjusting region, reducing the insertion loss between the pair of fiber optic connectors after randomly mating the pair of fiber optic connectors. 
     According to an object of the present invention, there is provided a fiber alignment device capable of positioning a fiber in a low precision ferrule in high precision and adjusting an eccentricity orientation of the fiber to a predetermined orientation. 
     According to an aspect of the present invention, there is provided a fiber alignment device for calibrating position accuracy of a fiber in a fiber bore of a ferrule assembly, comprising: a fixation block; an alignment element having a first end portion fixed in the fixation block and a second end portion formed with a protrudent platform, an alignment groove being formed in the alignment element and extending to an end of the protrudent platform in a central axis of the alignment element; an alignment sleeve having a first end portion fitted on the second end portion of the alignment element and a second end portion opposite to the first end portion; and a spring element having a first end entering into the alignment sleeve and pressed against the alignment groove in the protrudent platform downward in a direction perpendicular to the central axis of the alignment element. The fiber protrudes from the front end of the ferrule assembly, and the front end of the ferrule assembly is inserted into the alignment sleeve from the second end portion of the alignment sleeve until a predetermined length of the fiber protruding from the front end of the ferrule assembly enters into the alignment groove of the alignment element. When the front end of the ferrule assembly is inserted into the alignment sleeve and when the fiber is inserted into the alignment groove of the alignment element, the position accuracy of the fiber in the fiber bore of the ferrule assembly is calibrated to reach position accuracy of the fiber in the alignment groove of the alignment element. The first end of the spring element is configured to be pressed against the fiber inserted into the alignment groove, so that an eccentricity orientation of a center of the fiber with respect to a center of the alignment element is adjusted to a predetermined orientation and held in the predetermined orientation. 
     According to an exemplary embodiment of the present invention, the eccentricity orientation of the center of the fiber with respect to the center of the alignment element is adjusted to be just below the center of the alignment element. 
     According to another exemplary embodiment of the present invention, after the eccentricity orientation of the center of the fiber with respect to the center of the alignment element is adjusted to be just below the center of the alignment element, the fiber is fixed in the though hole of the ferrule assembly by an adhesive. 
     According to another exemplary embodiment of the present invention, an eccentricity orientation mark is formed on an outer surface of the ferrule assembly to identify the eccentricity orientation of the center of the fiber with respect to the center of the alignment element; or an existing feature on the ferrule assembly is used as an eccentricity orientation mark to identify the eccentricity orientation of the center of the fiber with respect to the center of the alignment element. 
     According to another exemplary embodiment of the present invention, the eccentricity orientation mark is located on a ferrule or a rear seat of the ferrule assembly. 
     According to another exemplary embodiment of the present invention, an injection hole, for injecting the adhesive into the ferrule assembly, formed in an external profile surface of the ferrule assembly is used as the eccentricity orientation mark. 
     According to another exemplary embodiment of the present invention, the spring element is configured to be a cantilever spring piece, and the second end of the spring element is connected to the fixation block by a screw; and a press force exerted on the fiber by the first end of the spring element is adjusted by controlling a distance of screwing the screw into a threaded hole in the fixation block, so as to adapt to different diameters of fibers. 
     According to another exemplary embodiment of the present invention, a positioning slot is formed in the spring element, and a protruding positioning key is formed on the fixation block; the positioning key is fitted in the positioning slot to position the spring element, so as to keep the position of the spring element in a direction perpendicular to the central axis of the alignment element and the press force unchanged. 
     According to another exemplary embodiment of the present invention, the spring element comprises a first sheet portion substantially parallel to the central axis of the alignment element and a second sheet portion substantially perpendicular to and intersected to the first sheet portion; and the positioning slot is formed in both the first sheet portion and the second sheet portion. 
     According to another exemplary embodiment of the present invention, a notch is formed in the alignment sleeve, and the first end of the spring element enters into the alignment sleeve through the notch. 
     According to an aspect of the present invention, there is provided a method for manufacturing a fiber optic ferrule device, comprising steps of: 
     providing a ferrule assembly; 
     inserting a fiber into a fiber bore of the ferrule assembly until the fiber protrudes a predetermined distance from a front end of the ferrule assembly; 
     injecting an adhesive into the ferrule assembly; 
     sucking the adhesive from the front end of the ferrule assembly, so that the adhesive flows to a front end surface of the ferrule assembly through a gap between the fiber and the fiber bore until a predetermined sized adhesive bump is formed on the front end surface of the ferrule assembly; 
     providing the fiber alignment device as mentioned in the above embodiments; 
     inserting the front end of the ferrule assembly into the alignment sleeve of the fiber alignment device until a predetermined length of the fiber, protruding from the front end of the ferrule assembly, enters into the alignment groove of the alignment element; and 
     curing the adhesive to fix the fiber in the fiber bore of the ferrule assembly. 
     According to another exemplary embodiment of the present invention, the method further comprises a step of: after the predetermined length of the fiber is inserted into the alignment groove of the alignment element, forming an eccentricity orientation mark on an outer surface of the ferrule assembly or using an existing feature on the ferrule assembly as an eccentricity orientation mark to identify the eccentricity orientation of the center of the fiber with respect to the center of the alignment element. 
     According to another exemplary embodiment of the present invention, the eccentricity orientation mark is located on a ferrule or a rear seat of the ferrule assembly. 
     According to another exemplary embodiment of the present invention, an injection hole, for injecting the adhesive into the ferrule assembly, formed in an external profile surface of the ferrule assembly is used as the eccentricity orientation mark. 
     According to another exemplary embodiment of the present invention, the adhesive is sucked from the front end of the ferrule assembly by a vacuum suction device. 
     According to another exemplary embodiment of the present invention, the vacuum suction device comprises: a vacuum generator; and a vacuum suction nozzle adapted to be hermetically sucked on the front end of the ferrule assembly and connected to a vacuum suction port of the vacuum generator through a connection pipe. 
     According to another exemplary embodiment of the present invention, the vacuum suction device further comprises: a pressure regulating valve connected to an inlet port of the vacuum generator, so as to adjust an inlet pressure of the vacuum generator. 
     According to another exemplary embodiment of the present invention, the vacuum suction device further comprises: a pressure sensor provided on the connection pipe between the vacuum suction nozzle and the vacuum suction port of the vacuum generator, so as to sense a negative pressure value in the connection pipe. 
     According to another exemplary embodiment of the present invention, the step of sucking the adhesive from the front end of the ferrule assembly comprises: determining whether the vacuum suction nozzle is hermetically sucked on the front end of the ferrule assembly based on the negative pressure value sensed by the pressure sensor. 
     According to another exemplary embodiment of the present invention, the vacuum suction device further comprises: a vacuum filter provided in the connection pipe between the vacuum suction nozzle and the vacuum suction port of the vacuum generator. 
     According to another exemplary embodiment of the present invention, the size of the adhesive bump formed on the front end surface of the ferrule assembly is identified by a visual recognition device. 
     According to another exemplary embodiment of the present invention, the method further comprises: controlling the vacuum generator to generate a failure pressure to release the vacuum suction nozzle from the ferrule assembly once the size of the adhesive bump formed on the front end surface of the ferrule assembly and identified by the visual recognition device reaches the predetermined size. 
     According to another exemplary embodiment of the present invention, the ferrule assembly, comprises: a ferrule formed with a fiber bore for receiving an optical fiber therein; and a rear seat connected to a rear end of the ferrule, wherein the rear seat is formed with a hollow chamber passing through the rear seat in a longitudinal direction and communicates with the fiber bore of the ferrule, wherein an injection hole for injecting the adhesive into the ferrule assembly is formed in an external profile surface of the ferrule assembly, and directly communicated with the fiber bore of the ferrule or the hollow chamber of the rear seat, and wherein the adhesive is injected into the fiber bore of the ferrule or the hollow chamber of the rear seat through the injection hole. 
     According to another exemplary embodiment of the present invention, the injection hole is formed in an external profile surface of the ferrule and directly communicated with the fiber bore of the ferrule. 
     According to another exemplary embodiment of the present invention, the injection hole has an outer opening outside the ferrule and an inner opening inside the ferrule; and the inner opening of the injection hole is configured to be smaller than the outer opening of the injection hole, so as to prevent an adhesive injection needle inserted through the outer opening of the injection hole from entering into the fiber bore of the ferrule. 
     According to another exemplary embodiment of the present invention, the injection hole has a dimension reducing from outside toward inside of the ferrule in a stepped manner or a tapered manner. 
     According to another exemplary embodiment of the present invention, the injection hole is formed in an external profile surface of the rear seat and directly communicated with the hollow chamber of the rear seat. 
     According to another exemplary embodiment of the present invention, the injection hole has an outer opening outside the rear seat and an inner opening inside the rear seat; and the inner opening of the injection hole is configured to be smaller than the outer opening of the injection hole, so as to limit a distance of an adhesive injection needle, inserted through the outer opening of the injection hole, entering into the hollow chamber of the rear seat. 
     According to another exemplary embodiment of the present invention, the injection hole has a dimension reducing from outside toward inside of the rear seat in a stepped manner or a tapered manner. 
     According to another exemplary embodiment of the present invention, the injection hole is formed at a joint location of the ferrule and the rear seat and directly communicated with the fiber bore at the rear end of the ferrule. 
     According to another exemplary embodiment of the present invention, an engagement protrusion is formed inside the rear seat and engaged into a recess in the external profile surface of the ferrule at the rear end of the ferrule. 
     According to another exemplary embodiment of the present invention, the injection hole is positioned behind the engagement protrusion; or the injection hole is positioned in the engagement protrusion and passes through the engagement protrusion. 
     According to another exemplary embodiment of the present invention, one or more injection hole is formed in the external profile surface of the ferrule assembly. 
     According to another exemplary embodiment of the present invention, the injection hole is positioned at any location of the external profile surface of the ferrule assembly. 
     According to another exemplary embodiment of the present invention, an angle of the injection hole with respect to the fiber bore is set to be any angle larger than zero. 
     According to another exemplary embodiment of the present invention, the injection hole has a circular, an oval or a rectangular cross section. 
     According to another exemplary embodiment of the present invention, the fiber bore at the rear end of the ferrule is formed in a horn shaped opening gradually expanded toward the hollow chamber of the rear seat and communicated with the hollow chamber; and the injection hole has an inner opening adjacent to or at the horn shaped opening. 
     According to another exemplary embodiment of the present invention, the ferrule assembly comprises a single-mode single-fiber ferrule assembly, a single-mode multi-fiber ferrule assembly, a multi-mode single-fiber ferrule assembly, or a multi-mode multi-fiber ferrule assembly. 
     According to another aspect of the present invention, there is provided a fiber optic ferrule device comprising: a ferrule assembly; and a fiber fixed in a fiber bore of the ferrule assembly, wherein the fiber optic ferrule device is manufactured by the above method. 
     With the fiber alignment device disclosed in the above exemplary embodiments of the present invention, the position accuracy of the fiber inserted into a fiber bore of a low ferrule assembly may be calibrated, producing a fiber optic connector with high precision and low insertion loss by the low precision ferrule. Generally, a gap between the fiber bore of the low precision ferrule and the inserted fiber may be far larger than a gap between a fiber bore of a high precision ferrule and the inserted fiber. The gap is filled with the adhesive, and the inserted fiber is fixed in the fiber bore by curing the adhesive. In the above exemplary embodiments of the present invention, the end of the fiber protruding from the front end surface of the ferrule is guided into the individual fiber alignment device with high precision, and the position accuracy of the fiber in the fiber bore of the low ferrule assembly is calibrated to reach the position accuracy of the fiber in the high precision fiber alignment device. Also, the center of the fiber is adjustable to regularly shift toward a preset side with respect to an ideal center, for example, by a displacement in an order of submicron or nanometre, and the calibrated and adjusted fiber is fixed in the fiber bore of the low precision ferrule. In this way, the position accuracy of the fiber in the fiber bore of the low ferrule assembly is calibrated to reach the position accuracy of the fiber in the fiber bore of the high precision ferrule, and a fiber optic connector with high precision and low insertion loss may be produced by the low precision ferrule. Furthermore, in the above exemplary embodiments of the present invention, the eccentricity orientation of the fiber is pre-adjusted to the predetermined orientation. Thereby, during mating a pair of fiber optic connectors, it may simply locate the eccentricity orientations of the pair of fiber optic connectors in the same fiber core adjusting region, reducing the insertion loss between the pair of fiber optic connectors after randomly mating the pair of fiber optic connectors. 
     Furthermore, the fiber optic connector produced by the low precision ferrule by means of the fiber alignment device according to the embodiments of the present invention has good controllability and predictability of the position accuracy of the fiber, good repeatability of the precision from a fiber optic connector to another fiber optic connector. Furthermore, since the eccentricity orientation of the fiber is pre-adjusted to the predetermined orientation, eliminating a process for adjusting the eccentricity orientation of the center of the fiber, (that is, the fiber alignment device according to the embodiments of the present invention achieves the fiber position calibration and the fiber core adjustment of the fiber optic connector, and the process for adjusting the eccentricity orientation of the center of the fiber is not necessary in subsequent processes). In this way, it greatly improves the optical performance and the random mating property (low insertion loss and low random mating loss) of the fiber optic connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1 a    is an illustrative view of a single-fiber ferrule assembly of a fiber optic connector in the prior art; 
         FIG. 1 b    is a cross section view of the single-fiber ferrule assembly shown in  FIG. 1   a;    
         FIG. 2 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a first exemplary embodiment of the present invention; 
         FIG. 2 b    is a cross section view of the ferrule assembly shown in  FIG. 2   a;    
         FIG. 3 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a second exemplary embodiment of the present invention; 
         FIG. 3 b    is a cross section view of the ferrule assembly shown in  FIG. 3   a;    
         FIG. 4 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a third exemplary embodiment of the present invention; 
         FIG. 4 b    is a cross section view of the ferrule assembly shown in  FIG. 4   a;    
         FIG. 5 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a fourth exemplary embodiment of the present invention; 
         FIG. 5 b    is a cross section view of the ferrule assembly shown in  FIG. 5   a;    
         FIG. 6 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a fifth exemplary embodiment of the present invention; 
         FIG. 6 b    is a cross section view of the ferrule assembly shown in  FIG. 6   a;    
         FIG. 7 a    is an illustrative view of a ferrule assembly of a fiber optic connector according to a sixth exemplary embodiment of the present invention; 
         FIG. 7 b    is a cross section view of the ferrule assembly shown in  FIG. 7   a;    
         FIG. 8  is an illustrative view of sucking an adhesive filled in a ferrule assembly from a front end of the ferrule assembly by means of a vacuum suction module according to an exemplary embodiment of the present invention; 
         FIG. 9 a    is a cross section view of inserting a fiber into the ferrule assembly before filling the adhesive into the ferrule assembly according to an exemplary embodiment of the present invention; 
         FIG. 9 b    is a cross section view of injecting the adhesive into the ferrule assembly after inserting the fiber into the ferrule assembly according to an exemplary embodiment of the present invention; 
         FIG. 9 c    is a cross section view of the ferrule assembly and the vacuum suction module of  FIG. 8 , showing the adhesive filled in the ferrule assembly is sucked from the front end of the ferrule assembly by the vacuum suction module; 
         FIG. 9 d    is an enlarged cross section view of a adhesive bump formed on the front end of the ferrule assembly after the adhesive is sucked onto the front end of the ferrule assembly; 
         FIG. 10  is an illustrative enlarged view of the front end of the ferrule assembly captured by a camera; 
         FIG. 11  is an illustrative block view of the vacuum suction module according to an exemplary embodiment of the present invention; 
         FIG. 12  is an illustrative exploded view of an apparatus for manufacturing the ferrule assembly according to an exemplary embodiment of the present invention; 
         FIG. 13 a    is an illustrative exploded view of a ferrule clamping module shown in  FIG. 12 ; 
         FIG. 13 b    is an illustrative assembled view of the ferrule clamping module shown in  FIG. 12 ; 
         FIG. 14  is an illustrative view of a fiber/cable clamping module shown in  FIG. 12 ; 
         FIG. 15 a    is an illustrative view of assembling the fiber/cable clamping module and the ferrule clamping module of  FIG. 12 , in which a press plate of the fiber/cable clamping module is opened, a press block of the ferrule clamping module is detached from a bottom seat of the press block, and the ferrule is positioned in a positioning slot of the ferrule clamping module; 
         FIG. 15 b    shows the fiber/cable clamping module and the ferrule clamping module of  FIG. 15 a   , in which the press block of the ferrule clamping module is assembled to the bottom seat, and the ferrule is clamped and fixed between the bottom seat and the press block; 
         FIG. 15 c    shows the fiber/cable clamping module and the ferrule clamping module of  FIG. 15 b   , in which the press plate of the fiber/cable clamping module is closed on a base seat, the fiber of the optical cable is inserted into the ferrule, and the optical cable is clamped and fixed between the base seat and the press plate; 
         FIG. 16 a    is an illustrative view of a fiber/cable clamping module according to another exemplary embodiment, in which a press plate of the fiber/cable clamping module is detached from the base seat; 
         FIG. 16 b    shows the fiber/cable clamping module of  FIG. 16 a   , in which a press plate of the fiber/cable clamping module is assembled to the base seat; 
         FIG. 17 a    is an illustrative view of a fiber/cable clamping module according to yet another exemplary embodiment, in which a press plate of the fiber/cable clamping module is detached from the base seat; 
         FIG. 17 b    shows the fiber/cable clamping module of  FIG. 17 a   , in which the press plate of the fiber/cable clamping module is assembled to the base seat; 
         FIG. 18 a    shows the vacuum suction module, the fiber/cable clamping module and the ferrule clamping module of  FIG. 12 , in which the vacuum suction module is separated from the ferrule clamping module; 
         FIG. 18 b    shows the vacuum suction module, the fiber/cable clamping module and the ferrule clamping module of  FIG. 18 a   , in which the vacuum suction module is engaged to the ferrule clamping module, and a vacuum suction nozzle is sucked to the front end of the respective ferrule assembly clamped by the ferrule clamping module; 
         FIG. 19 a    shows a fiber alignment module, the fiber/cable clamping module and the ferrule clamping module of  FIG. 12 , in which the fiber alignment module is separated from the ferrule clamping module; 
         FIG. 19 b    shows the fiber alignment module, the fiber/cable clamping module and the ferrule clamping module of  FIG. 19 a   , in which the fiber alignment module is engaged to the ferrule clamping module, and the front end of the respective ferrule assembly clamped by the ferrule clamping module is inserted into the respective alignment sleeve of the fiber alignment module; 
         FIG. 20 a    is an illustrative local structure view of the fiber alignment module of  FIGS. 19 a    and  19   b;    
         FIG. 20 b    is a local cross section view of the fiber alignment module; 
         FIG. 21 a    is an illustrative view of inserting the front end of the ferrule assembly into the fiber alignment module of  FIG. 20 b   , in which the fiber protruding from the front end of the ferrule assembly is not inserted into an alignment groove of an alignment element; 
         FIG. 21 b    is an illustrative view of inserting the front end of the ferrule assembly into the fiber alignment module of  FIG. 20 b   , in which the fiber protruding from the front end of the ferrule assembly is inserted into an alignment groove of an alignment element and pressed in the alignment groove by a spring element; 
         FIG. 22  is an principle view of adjusting an eccentricity orientation of the fiber by means of the fiber alignment module of  FIG. 21 b   ; and 
         FIG. 23  is an illustrative view of inserting the ferrule assembly into a housing of a fiber optic connector in a correct orientation. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     Exemplary embodiments of the present disclosure will be described hereinafter in detail with reference to the attached drawings, wherein the like reference numerals refer to the like elements. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art. 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     According to a general concept of the present invention, there is provided a ferrule assembly, comprising: a ferrule formed with a fiber bore for receiving an optical fiber; and a rear seat connected to a rear end of the ferrule. The rear seat is formed with a hollow chamber passing through the rear seat in a longitudinal direction and being in communication with the fiber bore of the ferrule. An injection hole for injecting an adhesive into the ferrule assembly is formed in an external profile surface of the ferrule assembly, which is perpendicular to the longitudinal direction of the ferrule assembly, and the injection hole directly is communicated with the fiber bore of the ferrule or the hollow chamber of the rear seat. 
       FIG. 2 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a first exemplary embodiment of the present invention;  FIG. 2 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 2   a.    
     As shown in  FIG. 2 a    and  FIG. 2 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 2 a  and 2 b   , an adhesive injection hole  101  is formed in an external profile surface (outer peripheral surface) of the ferrule  120 , which is perpendicular to the longitudinal direction of the ferrule assembly, and directly in communication with the fiber bore  121  of the ferrule  120 . 
     Referring to  FIG. 2 a    and  FIG. 2 b    again, in the illustrated embodiment, the adhesive injection hole  101  has an outer opening at an outside of the ferrule  120  and an inner opening at an inside of the ferrule  120 . The inner opening of the injection hole  101  is configured to be smaller than the outer opening of the injection hole  101 , so as to prevent an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  101  from entering into the fiber bore  121  of the ferrule  120 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  101  has a dimension reducing from the outside toward the inside of the ferrule  120  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 2 a  and 2 b   , only a single adhesive injection hole  101  is formed in the ferrule  120 . But the present invention is not limited to this, two or more adhesive injection holes  101  may be formed in the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 2 a  and 2 b   , an angle between the injection hole  101  and the fiber bore  121  is substantially equal to 90 degrees, that is, the injection hole  101  is substantially perpendicular to the fiber bore  121 . But the present invention is not limited to this, the angle between the injection hole  101  and the fiber bore  121  may be set to be any angle larger than 0 degree. 
     In the illustrated embodiment shown in  FIGS. 2 a  and 2 b   , the injection hole  101  has rectangular cross section. But the present invention is not limited to this, the cross section of the injection hole may have a circular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 3 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a second exemplary embodiment of the present invention;  FIG. 3 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 3   a.    
     As shown in  FIG. 3 a    and  FIG. 3 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 3 a  and 3 b   , an adhesive injection hole  102  is formed in an external profile surface (outer peripheral surface) of the rear seat  110  and directly in communication with the hollow chamber  114  of the rear seat  110 . 
     Referring to  FIGS. 3 a  and 3 b    again, the fiber bore  121  at the rear end of the ferrule  120  is formed in a horn shaped opening gradually expanded toward the hollow chamber  114  of the rear seat  110  and communicated with the hollow chamber  114 . The injection hole  102  has an inner opening adjacent to the horn shaped opening. 
     Referring to  FIGS. 3 a  and 3 b    again, in the illustrated embodiment, the injection hole  102  has an outer opening at an outside of the rear seat  110  and an inner opening at an inside of the rear seat  110 . The inner opening of the injection hole  102  is configured to be smaller than the outer opening of the injection hole  102 , so as to limit a distance of an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  102  entering into the hollow chamber  114  of the rear seat  110 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  102  has a dimension reducing from the outside toward the inside of the rear seat  110  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 3 a  and 3 b   , only a single adhesive injection hole  102  is formed in the rear seat  110 . But the present invention is not limited to this, two or more adhesive injection holes  102  may be formed in the rear seat  110 . 
     In the illustrated embodiment shown in  FIGS. 3 a  and 3 b   , an angle between the injection hole  102  and the fiber bore  121  is substantially equal to 90 degrees, that is, the injection hole  102  is substantially perpendicular to the fiber bore  121 . But the present invention is not limited to this, the angle between the injection hole  102  and the fiber bore  121  may be set to be any angle larger than 0 degree. 
     In the illustrated embodiment shown in  FIGS. 3 a  and 3 b   , the injection hole  102  has a circular cross section. But the present invention is not limited to this, the cross section of the injection hole may have a rectangular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 4 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a third exemplary embodiment of the present invention;  FIG. 4 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 4   a.    
     As shown in  FIG. 4 a    and  FIG. 4 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 4 a  and 4 b   , an adhesive injection hole  103  is formed in an external profile surface (outer peripheral surface) of the rear seat  110  and directly in communication with the hollow chamber  114  of the rear seat  110 . 
     Referring to  FIGS. 4 a  and 4 b    again, the injection hole  103  is relative large and has an elongated slot shape extending in the longitudinal direction. In this way, the injection hole  103  may receive more adhesive therein, and may prevent the adhesive from overflowing out of the injection hole  103  when the adhesive does not flow into the fiber bore  121  of the ferrule assembly in time. 
     Referring to  FIGS. 4 a  and 4 b    again, in the illustrated embodiment, the injection hole  103  has an outer opening at an outside of the rear seat  110  and an inner opening at an inside of the rear seat  110 . The inner opening of the injection hole  103  is configured to be smaller than the outer opening of the injection hole  103 , so as to limit a distance of an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  103  entering into the hollow chamber  114  of the rear seat  110 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  103  has a dimension reducing from the outside toward the inside of the rear seat  110  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 4 a  and 4 b   , only a single adhesive injection hole  103  is formed in the rear seat  110 . But the present invention is not limited to this, two or more adhesive injection holes  103  may be formed in the rear seat  110 . 
     In the illustrated embodiment shown in  FIGS. 4 a  and 4 b   , an angle between the injection hole  103  and the fiber bore  121  is substantially equal to 90 degrees, that is, the injection hole  103  is substantially perpendicular to the fiber bore  121 . But the present invention is not limited to this, the angle between the injection hole  103  and the fiber bore  121  may be set to be any angle larger than 0 degree. 
     In the illustrated embodiment shown in  FIGS. 4 a  and 4 b   , the injection hole  103  has an elongated slot shaped cross section. But the present invention is not limited to this, the cross section of the injection hole may have a rectangular shape, a circular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 5 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a fourth exemplary embodiment of the present invention;  FIG. 5 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 5   a.    
     As shown in  FIG. 5 a    and  FIG. 5 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 5 a  and 5 b   , an adhesive injection hole  104  is formed in an external profile surface (outer peripheral surface) of the rear seat  110  and directly in communication with the hollow chamber  114  of the rear seat  110 . 
     Referring to  FIGS. 5 a  and 5 b    again, the fiber bore  121  at the rear end of the ferrule  120  is formed in a horn shaped opening gradually expanded toward the hollow chamber  114  of the rear seat  110  and communicated with the hollow chamber  114 . The injection hole  104  has an inner opening adjacent to the horn shaped opening. 
     Referring to  FIGS. 5 a  and 5 b    again, in the illustrated embodiment, the injection hole  104  has an outer opening at an outside of the rear seat  110  and an inner opening at an inside of. The inner opening of the injection hole  104  is configured to be smaller than the outer opening of the injection hole  104 , so as to limit a distance of an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  104  entering into the hollow chamber  114  of the rear seat  110 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  104  has a dimension reducing from the outside toward the inside of the rear seat  110  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 5 a  and 5 b   , only a single adhesive injection hole  104  is formed in the rear seat  110 . But the present invention is not limited to this, two or more adhesive injection holes  104  may be formed in the rear seat  110 . 
     In the illustrated embodiment shown in  FIGS. 5 a  and 5 b   , an angle between the injection hole  104  and the fiber bore  121  is substantially equal to 45 degrees. But the present invention is not limited to this, the angle between the injection hole  104  and the fiber bore  121  may be set to be any angle larger than 0 degree. In the illustrated embodiment, by reducing the angle between the injection hole  104  and the fiber bore  121 , and the inner opening of the injection hole  104  is closer to the horn shaped opening at the rear end of the ferrule  120 . In this way, the injection hole  104  may receive more adhesive than, for example, the injection hole  102  shown in  FIGS. 3 a    and  3   b.    
     In the illustrated embodiment shown in  FIGS. 5 a  and 5 b   , the injection hole  104  has a circular cross section. But the present invention is not limited to this, the cross section of the injection hole may have a rectangular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 6 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a fifth exemplary embodiment of the present invention;  FIG. 6 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 6   a.    
     As shown in  FIG. 6 a    and  FIG. 6 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 6 a  and 6 b   , an adhesive injection hole  105  is formed at a joint location  112  of the ferrule  120  and the rear seat  110  and directly communicated with the fiber bore  121  at the rear end of the ferrule  120 . 
     Referring to  FIGS. 6 a  and 6 b    again, an engagement protrusion  115  is formed inside the rear seat  110  and engaged into a recess in the external profile surface of the ferrule  120  at the rear end of the ferrule  120 , so as to enhance the joining strength between the rear seat  110  and the ferrule  120 . 
     Referring to  FIGS. 6 a  and 6 b    again, in the illustrated embodiment, the injection hole  105  is formed in the engagement protrusion  115  and passes through the engagement protrusion  115 . 
     Referring to  FIGS. 6 a  and 6 b    again, the fiber bore  121  at the rear end of the ferrule  120  is formed in a horn shaped opening gradually expanded toward the hollow chamber  114  of the rear seat  110  and communicated with the hollow chamber  114 . The injection hole  105  has an inner opening adjacent to the horn shaped opening. 
     Referring to  FIGS. 6 a  and 6 b    again, in the illustrated embodiment, the injection hole  105  has an outer opening at an outside of the rear seat  110  and an inner opening at an inside of. The inner opening of the injection hole  105  is configured to be smaller than the outer opening of the injection hole  105 , so as to limit a distance of an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  105  entering into the fiber bore  121  of the ferrule  120 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  105  has a dimension reducing from the outside toward the inside of the ferrule  120  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 6 a  and 6 b   , only a single adhesive injection hole  105  is formed at the joint location  112  of the ferrule  120  and the rear seat  110 . But the present invention is not limited to this, two or more adhesive injection holes  105  may be formed. 
     In the illustrated embodiment shown in  FIGS. 6 a  and 6 b   , an angle between the injection hole  105  and the fiber bore  121  is substantially equal to 90 degrees, that is, the injection hole  105  is substantially perpendicular to the fiber bore  121 . But the present invention is not limited to this, the angle between the injection hole  105  and the fiber bore  121  may be set to be any angle larger than 0 degree. 
     In the illustrated embodiment shown in  FIGS. 6 a  and 6 b   , the injection hole  105  has a rectangular cross section. But the present invention is not limited to this, the cross section of the injection hole may have a circular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 7 a    is an illustrative view of a ferrule assembly  100  of a fiber optic connector according to a sixth exemplary embodiment of the present invention;  FIG. 7 b    is a cross section view of the ferrule assembly  100  shown in  FIG. 7   a.    
     As shown in  FIG. 7 a    and  FIG. 7 b   , the ferrule assembly  100  mainly comprises a ferrule  120  and a rear seat  110 . The ferrule  120  has a fiber bore  121  for receiving a fiber  210  therein. The rear seat  110  is connected to a rear end of the ferrule  120 . The rear seat  110  is formed with a hollow chamber  114  passing through the rear seat  110  in a longitudinal direction of the rear seat  110 . The hollow chamber  114  runs through the rear seat  110  and is in communication with the fiber bore  121  of the ferrule  120 . 
     In the illustrated embodiment shown in  FIGS. 7 a  and 7 b   , an adhesive injection hole  106  is formed at a joint location  112  of the ferrule  120  and the rear seat  110  and directly communicated with the fiber bore  121  at the rear end of the ferrule  120 . 
     Referring to  FIGS. 7 a  and 7 b    again, an engagement protrusion  115  is formed inside the rear seat  110  and engaged into a recess in the external profile surface of the ferrule  120  at the rear end of the ferrule  120 , so as to enhance the joining strength between the rear seat  110  and the ferrule  120 . 
     Referring to  FIGS. 7 a  and 7 b    again, in the illustrated embodiment, the injection hole  105  is positioned behind the engagement protrusion  115  and does not overlap with engagement protrusion  115 . As a result, the injection hole  106  does not run through the engagement protrusion  115 . 
     Referring to  FIGS. 7 a  and 7 b    again, the fiber bore  121  at the rear end of the ferrule  120  is formed in a horn shaped opening gradually expanded toward the hollow chamber  114  of the rear seat  110  and is communicated with the hollow chamber  114 . The injection hole  106  has an inner opening substantially located at the horn shaped opening. 
     Referring to  FIGS. 7 a  and 7 b    again, in the illustrated embodiment, the injection hole  106  has an outer opening at an outside of the ferrule assembly  100  and an inner opening at an inside of the ferrule assembly  100 . The inner opening of the injection hole  106  is configured to be smaller than the outer opening of the injection hole  106 , so as to limit a distance of an adhesive injection needle (not shown) inserted through the outer opening of the injection hole  106  entering into the fiber bore  121  of the ferrule  120 . In this way, it may protect the fiber (see  FIG. 9 a   ) inserted into the ferrule assembly  100  from being touched and damaged by the adhesive injection needle. 
     In an exemplary embodiment of the present invention, the adhesive injection hole  106  has a dimension reducing from the outside toward the inside of the ferrule  120  in a stepped manner or a tapered manner. 
     In the illustrated embodiment shown in  FIGS. 7 a  and 7 b   , only a single adhesive injection hole  106  is formed at the joint location  112  of the ferrule  120  and the rear seat  110 . But the present invention is not limited to this, two or more adhesive injection holes  106  may be formed. 
     In the illustrated embodiment shown in  FIGS. 7 a  and 7 b   , an angle between the injection hole  106  and the fiber bore  121  is substantially equal to 90 degrees, that is, the injection hole  106  is substantially perpendicular to the fiber bore  121 . But the present invention is not limited to this, the angle between the injection hole  106  and the fiber bore  121  may be set to be any angle larger than 0 degree. 
     In the illustrated embodiment shown in  FIGS. 7 a  and 7 b   , the injection hole  106  has a rectangular cross section. But the present invention is not limited to this, the cross section of the injection hole may have a circular shape, an oval shape, a polygonal shape or any other suitable shape. 
       FIG. 9 a    is a cross section view of inserting a fiber into the ferrule assembly before filling the adhesive into the ferrule assembly according to an exemplary embodiment of the present invention;  FIG. 9 b    is a cross section view of injecting the adhesive into the ferrule assembly after inserting the fiber into the ferrule assembly according to an exemplary embodiment of the present invention. 
     In an exemplary embodiment of the present invention, as shown in  FIG. 9 a   , the fiber  210  is firstly inserted into the fiber bore  121  of the ferrule assembly  100  without adhesive (the ferrule shown in  FIGS. 4 a  and 4 b   ), then, as shown in  FIG. 9 b   , the adhesive  116  is injected into the ferrule assembly  100  into which the fiber  210  has been inserted, and the fiber  210  is fixed in the fiber bore  121  by the adhesive  116 . As a result, a fiber optic ferrule device is formed. 
     According to another general concept of the present invention, there is provided a method for manufacturing a fiber optic ferrule device, comprising steps of: providing a ferrule assembly; inserting a fiber into a fiber bore of the ferrule assembly until the fiber protrudes a predetermined distance from a front end surface of the ferrule assembly; filling an adhesive into the ferrule assembly; and sucking the adhesive from the front end of the ferrule assembly, so that the adhesive flows to the front end surface of the ferrule assembly through a gap between the fiber and the fiber bore until a predetermined size of adhesive bump is formed on the front end surface of the ferrule assembly. 
     Hereafter, it will describe a method of manufacturing a ferrule device according to an exemplary embodiment with reference to  FIGS. 4 a , 4 b   ,  8 - 10 , the method mainly comprises steps of: 
     S 100 : providing a ferrule assembly  100  (for example, the ferrule assembly  100  shown in  FIGS. 4 a  and 4 b    or  FIGS. 2 a -3 b , 5 a -7 b   ) in which the adhesive is not filled yet; 
     S 110 : as shown in  FIG. 9 a   , inserting a fiber  210  into the ferrule assembly  100  without adhesive until the fiber  210  protrudes a predetermined distance from a front end surface of the ferrule assembly  100 ; 
     S 120 : as shown in  FIG. 9 b   , filling an adhesive  116  into the ferrule assembly  100  through an adhesive injection hole  103  formed in an external profile surface of the ferrule assembly  100  after the fiber  210  is inserted into the ferrule assembly  100 ; and 
     S 130 : as shown in  FIGS. 8 and 9   c , sucking the adhesive  116  from the front end of the ferrule assembly  100  by means of a vacuum suction device (to be described later) with vacuum suction nozzles  3200 , so that the adhesive  116  flows to the front end surface of the ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined sized adhesive bump  116   a  is formed on the front end surface of the ferrule assembly  100 , as shown in  FIG. 9   d.    
       FIG. 10  is an illustrative enlarged view of the front end of the ferrule assembly captured by a camera. 
     As shown in  FIG. 10 , in an exemplary embodiment of the present invention, the size of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  is identified by a visual recognition device. For instance, firstly, capturing an image of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  by a camera, and processing and identifying the captured image, so as to identify the size and/or shape of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100 . 
     In above embodiments of the present invention, after the adhesive is fully filled in the gap between the fiber  210  and the fiber bore  121  of the ferrule assembly  100 , the fiber  210  protruding from the front end surface of the ferrule assembly  100  is clean because the fiber  210  is inserted into the fiber bore  121  before filling the adhesive. As a result, there is no adhesive adhered on the fiber  210  protruding from the front end surface of the ferrule assembly  100 , ensuring the optical property of the fiber  210 . 
       FIG. 11  is an illustrative block view of the vacuum suction module according to an exemplary embodiment of the present invention. 
     As shown in  FIGS. 9 c    and  11 , in the illustrated embodiment, the vacuum suction device  3000  mainly comprises a vacuum generator and a vacuum suction nozzle  3200 . The vacuum suction nozzle  3200  is adapted to be hermetically sucked on the front end of the ferrule assembly  100  and connected to a vacuum suction port of the vacuum generator through a connection pipe  3300 . 
     Referring to  FIGS. 9 c    and  11  again, in the illustrated embodiment, the vacuum suction device  3000  further comprises a pressure regulating valve connected to an inlet port of the vacuum generator, so as to adjust an inlet pressure of the vacuum generator. 
     Referring to  FIG. 9 c    and again, in the illustrated embodiment, the vacuum suction device  3000  further comprises a pressure sensor provided on the connection pipe  3300  between the vacuum suction nozzle  3200  and the vacuum suction port of the vacuum generator, so as to sense a negative pressure value in the connection pipe  3300 . In this way, it is possible to determine whether the vacuum suction nozzle  3200  is hermetically sucked on the front end of the ferrule assembly  100  based on the negative pressure value sensed by the pressure sensor. If the vacuum suction nozzle  3200  is not hermetically sucked on the front end of the ferrule assembly  100 , air leakage is present, and the negative pressure value sensed by the pressure sensor cannot reach a predetermined value. Thereby, on one hand, if the negative pressure value sensed by the pressure sensor is less than the predetermined value, it may directly determine that air leakage is present. On the other hand, if the negative pressure value sensed by the pressure sensor is equal to or higher than the predetermined value, it may directly determine that air leakage is not present. 
     Referring to  FIG. 11  again, in the illustrated embodiment, the vacuum suction device  3000  further comprises a vacuum filter provided in the connection pipe  3300  between the vacuum suction nozzle  3200  and the vacuum suction port of the vacuum generator. The vacuum filter is used to filter impurities from the air, so as to protect the vacuum generator from the impurities. 
     As shown in  FIGS. 10 and 11 , in an exemplary embodiment of the present invention, a controller (not shown) is provided to control the vacuum generator to generate a failure pressure to release the vacuum suction nozzle  3200  from the ferrule assembly  100  once the size and/or shape of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  and identified by the visual recognition device reaches the predetermined size and/or shape. After the vacuum suction nozzle  3200  is released from the ferrule assembly  100 , a position of the fiber  210  in the fiber bore  121  of the ferrule assembly  100  may be calibrated, and an eccentricity orientation of the center of the fiber  210  with respect to an indexing feature of the ferrule assembly  100  (for example, an outer circumferential surface of a single-fiber ferrule or an alignment hole of a multi-fiber ferrule) may be adjusted to a predetermined orientation, and this will be described in detail later. After the position and the eccentricity orientation of the fiber  210  are calibrated and adjusted, the adhesive  116  may be cured to fix the fiber  210  in the fiber bore  121  of the ferrule assembly  100 . After the fiber  210  is fixed in the fiber bore  121  of the ferrule assembly  100 , the front end surface of the ferrule assembly  100  may be ground and polished. As a result, a ferrule assembly is manufactured. 
     According to another general concept of the present invention, there is provided a fiber optic alignment device for calibrating position accuracy of a fiber in a fiber bore of a ferrule assembly. The fiber optic alignment device comprises: a fixation block; an alignment element having a first end portion fixed in the fixation block and a second end portion formed with a protrudent platform, wherein an alignment groove is formed in the alignment element and extends to the end of the protrudent platform in a central axis of the alignment element; an alignment sleeve having a first end portion fitted on the second end portion of the alignment element and a second end portion opposite to the first end portion; and a spring element having a first end extending into the alignment sleeve and being pressed against the alignment groove in the protrudent platform in a direction perpendicular to the central axis of the alignment element. The fiber protrudes from the front end of the ferrule assembly, and the front end of the ferrule assembly is inserted into the alignment sleeve from the second end portion of the alignment sleeve until a predetermined length of the fiber protruding from the front end of the ferrule assembly enters into the alignment groove of the alignment element. When the front end of the ferrule assembly is inserted into the alignment sleeve and when the fiber is inserted into the alignment groove of the alignment element, the position accuracy of the fiber in the fiber bore of the ferrule assembly is calibrated to reach position accuracy of the fiber in the alignment groove of the alignment element. The first end of the spring element is configured to be pressed against the fiber inserted into the alignment groove, so that an eccentricity orientation of a center of the fiber with respect to a center of the alignment element is adjusted to a predetermined orientation and held in the predetermined orientation. 
       FIG. 20 a    is an illustrative local structure view of the fiber alignment device (or referred as the fiber alignment module);  FIG. 20 b    is a local cross section view of the fiber alignment device. 
     As shown in  FIGS. 20 a  and 20 b   , in the illustrated embodiment, the fiber alignment device mainly comprises a fixation block  4500 , an alignment element  4400 , an alignment sleeve  4300  and a spring element  4200 . 
     Referring to  FIGS. 20 a  and 20 b   , the alignment element  4400  has a first end portion fixed in the fixation block  4500  and a second end portion formed with a protrudent platform  4420 . An alignment groove  4410  is formed in the alignment element  4400  and extends to the end of the protrudent platform  4420  in a central axis of the alignment element  4400 . 
     The alignment sleeve  4300  has a first end portion fitted on the second end portion of the alignment element  4400  and a second end portion opposite to the first end portion. 
     The spring element  4200  has a first end  4231  entering into the alignment sleeve  4300  and pressed against the alignment groove  4410  in the protrudent platform  4420  in a direction perpendicular to the central axis of the alignment element  4400  (see  FIG. 22 ). 
       FIG. 21 a    is an illustrative view of inserting the front end of the ferrule assembly  100  into the fiber alignment module of  FIG. 20 b   , in which the fiber  210  protruding from the front end of the ferrule assembly  100  is not inserted into the alignment groove  4410  of the alignment element  4400 ;  FIG. 21 b    is an illustrative view of inserting the front end of the ferrule assembly  100  into the fiber alignment module of  FIG. 20 b   , in which the fiber  210  protruding from the front end of the ferrule assembly  100  is inserted into the alignment groove  4410  of the alignment element  4400  and pressed in the alignment groove  4410  by the spring element  4200 . 
     As shown in  FIGS. 21 a  and 21 b   , the fiber  210  protrudes from the front end of the ferrule assembly  100 , and the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  from the second end portion of the alignment sleeve  4300  until a predetermined length of the fiber  210  protruding from the front end of the ferrule assembly  100  enters into the alignment groove  4410  of the alignment element  4400 . Once the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  and the fiber  210  is inserted into the alignment groove  4410  of the alignment element  4400 , the position accuracy of the fiber  210  in the fiber bore  121  of the ferrule assembly  100  is calibrated to reach position accuracy of the fiber  210  in the alignment groove  4410  of the alignment element  4400 . Please be noted that, in this embodiment, the geometric center of the alignment groove  4410  is accurately positioned at an ideal center determined with reference to an inner circumferential surface of the alignment sleeve  4300 , therefore, it ensures the calibrated center of the fiber  210  is accurately positioned at an ideal center determined with reference to an outer circumferential surface of the ferrule assembly  100 . Herein, the term ‘accurately positioned’ means that an error between the actual center and the ideal center of the fiber is less than a predetermined value, for example, less than 0.0005 mm or even more less. 
       FIG. 22  is a principle view of adjusting an eccentricity orientation of the fiber by means of the fiber alignment module of  FIG. 21   b.    
     As shown in  FIGS. 21 b    and  22 , when the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  and when the fiber  210  is inserted into the alignment groove  4410  of the alignment element  4400 , the first end  4231  of the spring element  4200  is pressed against the fiber  210  inserted into the alignment groove  4410 , so that an eccentricity orientation of a center O′ of the fiber  210  with respect to a center O of the alignment element  4400  is adjusted to a predetermined orientation and held in the predetermined orientation. 
     As shown in  FIGS. 21 b    and  22 , the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  is adjusted to be just below the center O of the alignment element  4400 . 
     In an exemplary embodiment of the present invention, after the center O′ of the fiber  210  is adjusted to be just below the center O of the alignment element  4400 , an eccentricity orientation mark is formed on an outer surface of the ferrule assembly  100  to identify the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400 . In an alternative embodiment, after the center O′ of the fiber  210  is adjusted to be just below the center O of the alignment element  4400 , an existing feature on the ferrule assembly  100  may be used as an eccentricity orientation mark to identify the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400 . In an exemplary embodiment of the present invention, the eccentricity orientation mark may be any mark, such as, notching mark, printing mark or any other visible mark, located on the ferrule  120  or the rear seat  110  of the ferrule assembly  100 . 
     In another exemplary embodiment, as shown in  FIG. 23 , the injection hole  103  formed in the rear seat  110  may be served as the eccentricity orientation mark. In this way, it is no necessary to individually form an eccentricity orientation mark on the ferrule assembly  100 . Referring to  FIG. 23  again, in the illustrated embodiment, when the injection hole  103  is used as the eccentricity orientation mark, it is possible to determine the correct orientation, for example, an orientation when the injection hole  103  is positioned vertically upward, of the ferrule assembly  100  with respect to a housing  300  of a fiber optic connector based on the injection hole  103 . In the illustrated embodiment of  FIG. 23 , after the ferrule assembly  100  with the optical cable  200  is inserted into the connector housing  300  based on the correct orientation, other members, such as, a spring  400 , a spring seat  500 , etc., of the connector may be subsequently mounted in the connector housing  300 , and the fiber optic connector is assembled. Please be noted that the present invention is not limited to this, the spring  400 , the spring seat  500  and the ferrule assembly  100  may be pre-assembled together to form an integral member, and then they, as the integral member, may be mounted in the connector housing  300  at one time. 
     In an exemplary embodiment of the present invention, after the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  is adjusted to be just below the center O of the alignment element  4400 , the fiber  210  is fixed in the though hole  121  of the ferrule assembly  100  by the cured adhesive  116 . In this way, the position calibration and the eccentricity orientation adjustment of the fiber  210  are finished. 
     Referring to  FIGS. 20 a   - 22  again, in the illustrated embodiment, the spring element  4200  is configured to be a cantilever spring piece, and the second end  4210  of the spring element  4200  is connected to the fixation block  4500  by a screw  4211 . A press force F exerted on the fiber  210  by the first end  4231  of the spring element  4200  is adjusted to adapt to different diameters of fibers by controlling a distance of screwing the screw  4211  into a threaded hole  4111  in the fixation block  4500 . 
     Although it is not shown, in another embodiment of the present invention, the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  may be controlled by the adjusting the press force F. For example, it is possible to adjust the center O′ of the fiber  210  to a position just above the center O of the alignment element  4400  or just overlapping with the center O of the alignment element  4400  by adjusting the press force F. 
     In an exemplary embodiment of the present invention, as shown in  FIGS. 20-22 , a positioning slot  4221  is formed in the spring element  4200 , and a protruding positioning key  4121  is formed on the fixation block  4500 . The positioning key  4121  is fitted in the positioning slot  4221  to hold the position of the spring element  4200 , so as to keep the position of the spring element  4200  in a direction perpendicular to the central axis of the alignment element  4400  and the press force F (a direction perpendicular to the positioning slot  4221  shown in  FIG. 20 a   ) unchanged. 
     Referring to  FIG. 20 a    again, in the illustrated embodiment, the spring element  4200  comprises a first sheet portion  4230  substantially parallel to the central axis of the alignment element  4400  and a second sheet portion  4220  substantially perpendicular to and integrally connected to the first sheet like portion  4230 . The positioning slot  4221  is formed in both the first sheet portion  4230  and the second sheet portion  4220 . In this embodiment, the positioning slot  4221  is formed to include two portions substantially perpendicular to and communicated with each other, improving the positioning reliability and precision of the positioning slot  4221 . 
     Referring to  FIG. 20 a    again, in the illustrated embodiment, a notch  4330  is formed in the alignment sleeve  4300 , and the first end  4231  of the spring element  4200  enters into the alignment sleeve  4300  through the notch  4330 . 
     According to another general concept of the present invention, there is provided a method for manufacturing a fiber optic ferrule device, comprising steps of: providing a ferrule assembly; inserting a fiber into a fiber bore of the ferrule assembly until the fiber protrudes a predetermined distance from a front end of the ferrule assembly; injecting an adhesive into the ferrule assembly; sucking the adhesive from the front end of the ferrule assembly, so that the adhesive flows to the front end surface of the ferrule assembly through a gap between the fiber and the fiber bore until a predetermined sized adhesive bump is formed on the front end surface of the ferrule assembly; providing the fiber optic alignment device as mentioned in the above embodiments; inserting the front end of the ferrule assembly into the alignment sleeve of the fiber optic alignment device until a predetermined length of the fiber, protruding from the front end of the ferrule assembly, enters into the alignment groove of the alignment element; and curing the adhesive to fix the fiber in the fiber bore of the ferrule assembly. 
     Hereafter, it will describe a method of manufacturing a fiber optic ferrule device with reference to  FIGS. 4 a , 4 b   ,  8 - 10  according to an exemplary embodiment of the present invention, and the method mainly comprises following steps of: 
     S 200 : providing a ferrule assembly  100  (for example, the ferrule assembly  100  shown in  FIGS. 4 a  and 4 b    or  FIGS. 2 a -3 b , 5 a -7 b   ) in which the adhesive is not filled yet; 
     S 210 : as shown in  FIG. 9 a   , inserting a fiber  210  into the ferrule assembly  100  without the adhesive until the fiber  210  protrudes a predetermined distance from a front end surface of the ferrule assembly  100 ; 
     S 220 : as shown in  FIG. 9 b   , filling the adhesive  116  into the ferrule assembly  100  through an adhesive injection hole  103  formed in an external profile surface of the ferrule assembly  100  after the fiber  210  is inserted into the ferrule assembly  100 ; 
     S 230 : as shown in  FIGS. 8 and 9   c , sucking the adhesive  116  from the front end of the ferrule assembly  100  by means of a vacuum suction device with vacuum suction nozzles  3200 , so that the adhesive  116  flows to the front end surface of the ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined sized adhesive bump  116   a  is formed on the front end surface of the ferrule assembly  100 , as shown in  FIG. 9   d;    
     S 240 : providing a fiber optic alignment device, for example, the fiber optic alignment device shown in  FIGS. 20 a   - 21   b;    
     S 250 : inserting the front end of the ferrule assembly  100  into the alignment sleeve  4300  of the fiber optic alignment device until a predetermined length of the fiber  210 , protruding from the front end of the ferrule assembly  100 , enters into the alignment groove  4410  of the alignment element  4400 ; and 
     S 260 : curing the adhesive  116  to fix the fiber  210  in the fiber bore  121  of the ferrule assembly  100 . 
     According to another exemplary embodiment of the present invention, there is provided a fiber optic ferrule device comprising a ferrule assembly  100  and a fiber  210  fixed in a fiber bore  121  of the ferrule assembly  100 , and the fiber optic ferrule device is manufactured by the above method. 
     According to still another general concept of the present invention, there is provided an apparatus for manufacturing a fiber optic ferrule device, wherein the fiber optic ferrule device comprises a ferrule assembly and an optical cable, a fiber bared from an end of the optical cable is inserted into a fiber bore of the ferrule assembly and protrudes from a front end of the ferrule assembly. The apparatus comprising: a ferrule clamping module configured to clamp and position a plurality of ferrule assemblies; a fiber/cable clamping module adapted to be engaged to a rear side of the ferrule clamping module, and configured to clamp and position a section of the respective optical cable behind the ferrule clamping module; a vacuum suction module adapted to be engaged to a front side of the ferrule clamping module, and configured to suck an adhesive filled in the respective ferrule assembly from the front end of the ferrule assembly, so that the adhesive flows to a front end surface of the ferrule assembly through a gap between the fiber and the fiber bore until a predetermined size of adhesive bump is formed on the front end surface of the ferrule assembly; and a fiber alignment module adapted to be engaged to the front side of the ferrule clamping module, and configured to calibrate position accuracy of the respective fiber inserted into the fiber bore of the respective ferrule assembly and adjust an eccentricity orientation of the center of the respective fiber to a predetermined orientation. The adhesive is injected into the ferrule assembly after the fiber is inserted into the fiber bore of the ferrule assembly. When the predetermined size of adhesive bump is formed on the front end surface of the ferrule assembly, the vacuum suction module is removed from the ferrule clamping module, and the fiber alignment module is engaged to the ferrule clamping module. 
       FIG. 12  is an illustrative exploded view of an apparatus for manufacturing a ferrule assembly  100  according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 12 , in the illustrated embodiment, the apparatus for manufacturing the fiber optic ferrule device mainly comprises a fiber/cable clamping module  1000 , a ferrule clamping module  2000 , a vacuum suction module  3000  and a fiber alignment module  4000 . 
       FIG. 13 a    is an illustrative exploded view of a ferrule clamping module  2000  shown in  FIG. 12 ;  FIG. 13 b    is an illustrative assembled view of the ferrule clamping module  2000  shown in  FIG. 12 . 
     As shown in  FIGS. 12 and 13 , the ferrule clamping module  2000  is configured to clamp and position a plurality of ferrule assemblies  100 . 
     In an exemplary embodiment of the present invention, as shown in  FIGS. 12, 13   a  and  13   b , the ferrule clamping module  2000  mainly comprises a bottom seat  2100  and a press block  2200 . A row of positioning slots  2130  are formed on the bottom seat  2100  to position the plurality of ferrule assemblies  100 , and front alignment pins  2110  and rear alignment pins  2120  are provided at front and rear sides of both ends of bottom seat  2100 , respectively. The press block  2200  is adapted to be mounted on the bottom seat  2100 . As shown in  FIG. 13 b   , when the press block  2200  is assembled on the bottom seat  2100 , the ferrule assemblies  100  positioned in the positioning slots  2130  is clamped and held between the bottom seat  2100  and the press block  2200 . 
     As shown in  FIGS. 12, 13   a  and  13   b , in the illustrated embodiment, recesses  2140 , matched with both end portions  2240  of the press block  2200 , are formed in the bottom seat  2100 . The end portions  2240  of the press block  2200  are fitted in the recesses  2140  of the bottom seat  2100 . 
     As shown in  FIGS. 13 a  and 13 b   , in an embodiment, an injection hole  103 , for injecting the adhesive  116  into the respective ferrule assembly  100 , is formed in an external profile surface of the ferrule assembly  100  and communicated with the fiber bore  121  of the ferrule assembly  100 . The injection hole  103  is positioned upward as the ferrule assembly  100  is clamped and positioned by the ferrule clamping module  2000 . A plurality of notches  2230 , corresponding to injection holes  103  of the ferrule assemblies  100 , respectively, are formed in the press block  2200 . The adhesive  116  is injected into the ferrule assembly  100  by an adhesive injection needle (not shown) inserted into the injection hole  103  through the notch  2230  (see  FIG. 9 b   ). 
       FIG. 14  is an illustrative view of a fiber/cable clamping module  1000  shown in  FIG. 12 . 
     As shown in  FIGS. 12 and 14 , in an embodiment of the present invention, the fiber/cable clamping module  1000  is adapted to be engaged to a rear side of the ferrule clamping module  2000 , and configured to clamp and position a section of the respective optical cable  200  behind the ferrule clamping module  2000  (see  FIG. 15 c   ). 
     In the illustrated embodiment, as shown in  FIGS. 12 and 14 , the fiber/cable clamping module  1000  mainly comprises a base seat  1100  and a press plate  1200 . Alignment holes  1120 , for matching with the rear alignment pins  2120  of the ferrule clamping module  2000 , are formed in both ends of the base seat  1100 , respectively. The press plate  1200  is adapted to be mounted on the base seat  1100 . When the press plate  1200  is assembled on the base seat  1100 , the optical cable  200  inserted into the ferrule assembly  100  is clamped and held between the base seat  1100  and the press plate  1200  (see  FIG. 15 c   ). 
     As shown in  FIGS. 12, 14 and 15   a - 15   c , in an embodiment of the present invention, a first elastic soft pad  1130  is provided on a top surface of the base seat  1100 , and a second elastic soft pad  1230  is provided on a bottom surface of the press plate  1200 . The optical cable  200  is clamped and held between the first elastic soft pad  1130  and the second elastic soft pad  1230 . In this way, it may protect the fiber of the optical cable  200  from being crushed. 
     As shown in  FIG. 14 , in the illustrated embodiment, a first end of the press plate  1200  is rotatably connected to the base seat  1100 , and a second end of the press plate  1200  is mounted on the base seat  1100  in a pin-hole matching manner. For example, referring to  FIG. 14 , a positioning pin  1240  is provided on the second end of the press plate  1200 , and a positioning hole  1140  for matching with the positioning pin  1240  is formed in the base seat  1100 . The second end of the press plate  1200  is mounted on the base seat  1100  by fitting the positioning pin  1240  into the positioning hole  1140 . 
     Hereafter, it will describe operations of fixing the ferrule assembly  100  on the ferrule clamping module  2000  and fixing the optical cable  200  that has been inserted into the ferrule assembly  100  on the fiber/cable clamping module  1000  with reference to  FIGS. 14, 15   a ,  15   b  and  15   c.    
     Firstly, as shown in  FIGS. 14 and 15   a , inserting the rear alignment pin  2120  of the ferrule clamping module  2000  into the alignment hole  1120  of the fiber/cable clamping module  1000 , and engaging the fiber/cable clamping module  1000  to the ferrule clamping module  2000 . At this time, the press plate  1200  of the fiber/cable clamping module  1000  is opened, the press block  2200  of the ferrule clamping module  2000  is detached from the bottom seat  2100 , and the ferrule assembly  100  is positioned in the positioning slots  2130  of the ferrule clamping module  2000 . 
     Then, as shown in  FIG. 15 b   , assembling the press block  2200  of the ferrule clamping module  2000  on the bottom seat  2100 , so as to clamp and hold the ferrule assembly  100  between the bottom seat  2100  and the press block  2200 . 
     Finally, as shown in  FIG. 15 c   , laying down the press plate  1200  of the fiber/cable clamping module  1000  on the base seat  1100 , so as to clamp and hold the optical cable  200 , that has been inserted into the ferrule assembly  100 , between the base seat  1100  and the press plate  1200 . 
     In this way, the ferrule assembly  100  is held on the ferrule clamping module  2000 , and the optical cable  200 , that has been inserted into the ferrule assembly  100 , is held on the fiber/cable clamping module  1000 . 
     In the illustrated embodiment, the ferrule clamping module  2000  has twelve ferrule positioning slots  2130 , and twelve ferrule assemblies  100  may be positioned at one time, or, in other words, twelve ferrule assemblies (fiber optic ferrule device)  100  may be manufactured at one time. But the present invention is not limited to this, the ferrule clamping module  2000  may have more or less ferrule positioning slots  2130 , for example, the ferrule clamping module  2000  may have twenty or more ferrule positioning slots  2130 . 
       FIG. 16 a    is an illustrative view of a fiber/cable clamping module  1000 ′ according to another exemplary embodiment, in which a press plate  1200 ′ of the fiber/cable clamping module  1000 ′ is detached from the base seat  1100 ′;  FIG. 16 b    shows the fiber/cable clamping module  1000 ′ of  FIG. 16 a   , in which the press plate  1200 ′ of the fiber/cable clamping module  1000 ′ is assembled to the base seat  1100 ′. 
     As shown in  FIGS. 16 a  and 16 b   , in an exemplary embodiment of the present invention, the press plate  1200 ′ is adapted to be mounted on the base seat  1100 ′ in a pin-hole matching manner. 
     In the illustrated embodiment, as shown in  FIGS. 16 a  and 16 b   , a positioning pin  1240 ′ is provided on each end of the press plate  1200 ′, and a positioning hole  1140 ′ for matching with the positioning pin  1240 ′ is formed in each end of the base seat  1100 ′. The press plate  1200 ′ is mounted on the base seat  1100 ′ by fitting the positioning pin  1240 ′ into the positioning hole  1140 ′. 
       FIG. 17 a    is an illustrative view of a fiber/cable clamping module  1000 ″ according to yet another exemplary embodiment, in which a press plate  1200 ″ of the fiber/cable clamping module  1000 ″ is detached from the base seat  1100 ″;  FIG. 17 b    shows the fiber/cable clamping module  1000 ″ of  FIG. 17 a   , in which the press plate  1200 ″ of the fiber/cable clamping module  1000 ″ is assembled to the base seat  1100 ″. 
     As shown in  FIGS. 17 a  and 17 b   , in an exemplary embodiment of the present invention, the press plate  1200 ″ is adapted to be mounted on the base seat  1100 ″ in a plugging manner. 
     In the illustrated embodiment, as shown in  FIGS. 17 a  and 17 b   , a tapered positioning portion  1280 ″ is formed on each end of the press plate  1200 ″, and a tapered positioning slot  1180 ″ for matching with the tapered positioning portion  1280 ″ is formed in the base seat  1100 ″. The press plate  1200 ″ is mounted on the base seat  1100 ″ by plugging the tapered positioning portion  1280 ″ into the tapered positioning slot  1180 ″. 
       FIG. 18 a    shows the vacuum suction module  3000 , the fiber/cable clamping module  1000  and the ferrule clamping module  2000  of  FIG. 12 , in which the vacuum suction module  3000  is separated from the ferrule clamping module  2000 ;  FIG. 18 b    shows the vacuum suction module  3000 , the fiber/cable clamping module  1000  and the ferrule clamping module  2000  of  FIG. 18 a   , in which the vacuum suction module  3000  is engaged to the ferrule clamping module  2000 , and a vacuum suction nozzle  3200  is sucked to the front end of the respective ferrule assembly  100  clamped by the ferrule clamping module  2000 . 
     As shown in  FIGS. 18 a  and 18 b   , in the illustrated embodiment, the vacuum suction module  3000  is adapted to be engaged to a front side of the ferrule clamping module  2000 , and configured to suck an adhesive  116  filled in the respective ferrule assembly  100  from the front end of the ferrule assembly  100 , so that the adhesive  116  flows to a front end surface of the ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined size of adhesive bump  116   a  is formed on the front end surface of the ferrule assembly  100 . 
     In an embodiment of the present invention, as shown in  FIGS. 18 a  and 18 b   , the vacuum suction module  3000  mainly comprises a fixation frame  3100 , a row of vacuum suction nozzles  3200  mounted on the fixation frame  3100  and a vacuum generator connected to the vacuum suction nozzles  3200  (see  FIG. 11 ). 
     As described above, as shown in  FIGS. 8 and 11 , the vacuum suction nozzle  3200  is connected to the vacuum suction port of the vacuum generator through a connection pipe  3300 . 
     In an embodiment of the present invention, alignment holes  3110 , for matching with the front alignment pins  2110  of the ferrule clamping module  2000 , are formed on both ends of the fixation frame  3100 , respectively. The row of vacuum suction nozzles  3200  are fixed on the fixation frame  3100 , and each of the vacuum suction nozzles  3200  is adapted to be hermetically sucked on the front end of the respective ferrule assembly  100 . 
     As shown in  FIGS. 18 a  and 18 b   , the ferrule clamping module  2000  may be accurately engaged to the vacuum suction module  3000  simply by inserting the front alignment pin  2110  of the ferrule clamping module  2000  into the alignment hole  3110  of the vacuum suction module  3000 . After the ferrule clamping module  2000  is engaged to the vacuum suction module  3000 , the vacuum suction nozzles  3200  of the vacuum suction module  3000  are aligned to the front ends of the respective ferrule assemblies  100  fixed on the ferrule clamping module  2000 , so as to be sucked on the front end of the respective ferrule assemblies  100 . 
     As shown in  FIGS. 18 a  and 18 b   , in an embodiment of the present invention, a space control member  3120  is provided on a rear side of each end of the fixation frame  3100 , so as to control a space between the fixation frame  3100  and the ferrule clamping module  2000  and limit a length of the ferrule assembly  100  sucked into the vacuum suction nozzle  3200 . In this way, it may prevent the ferrule assembly  100  from being excessively sucked into the vacuum suction nozzle  3200 . If the ferrule assembly  100  is excessively sucked into the vacuum suction nozzle  3200 , the fiber  210  protruding from the front end of the ferrule assembly  100  may be damaged, or even the front end surface of the ferrule assembly  100  is ruined. 
     In an embodiment of the present invention, as described above, as shown in  FIGS. 8 and 9   c , the vacuum suction module  3000  is configured to suck the adhesive  116  filled in the respective ferrule assembly  100  from the front end of the ferrule assembly  100 , so that the adhesive  116  flows to the front end surface of the ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined size of adhesive bump  116   a  is formed on the front end surface of the ferrule assembly  100 , as shown in  FIG. 9   d.    
     As described above, as shown in  FIG. 10 , in an exemplary embodiment of the present invention, the size of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  is identified by a visual recognition device (not shown). For instance, the visual recognition device is configured to capture an image of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  by a camera, and process and identify the captured image, so as to determine the size and/or shape of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100 . 
     In above embodiments of the present invention, after the adhesive is fully filled in the gap between the fiber  210  and the fiber bore  121  of the ferrule assembly  100 , the fiber  210  protruding from the front end surface of the ferrule assembly  100  is clean because the fiber  210  is inserted into the fiber bore  121  before filling the adhesive. As a result, there is no adhesive adhered on the fiber  210  protruding from the front end surface of the ferrule assembly  100 , ensuring the optical property of the fiber  210 . 
     As described above, as shown in  FIG. 11 , the vacuum suction device  3000  further comprises a pressure regulating valve connected to an inlet port of the vacuum generator, so as to adjust an inlet pressure of the vacuum generator. 
     As described above, referring to  FIGS. 9 c    and  11  again, the vacuum suction device  3000  further comprises a pressure sensor provided on the connection pipe  3300  between the vacuum suction nozzle  3200  and the vacuum suction port of the vacuum generator, to sense a negative pressure value in the connection pipe  3300 . In this way, it is possible to determine whether the vacuum suction nozzle  3200  is hermetically sucked on the front end of the ferrule assembly  100  based on the negative pressure value sensed by the pressure sensor. If the vacuum suction nozzle  3200  is not hermetically sucked on the front end of the ferrule assembly  100 , air leakage is present, and the negative pressure value sensed by the pressure sensor cannot reach a predetermined value. Thereby, on one hand, if the negative pressure value sensed by the pressure sensor is less than the predetermined value, it may directly determine that air leakage is present. On the other hand, if the negative pressure value sensed by the pressure sensor is equal to or higher than the predetermined value, it may directly determine that air leakage is not present. 
     As described above, referring to  FIGS. 9 c    and  11  again, in the illustrated embodiment, the vacuum suction device  3000  further comprises a vacuum filter provided in the connection pipe  3300  between the vacuum suction nozzle  3200  and the vacuum suction port of the vacuum generator. The vacuum filter is used to filter impurities from the air, so as to protect the vacuum generator from the impurities. 
     As described above, referring to  FIGS. 10 and 11 , in an exemplary embodiment of the present invention, a controller (not shown) is provided to control the vacuum generator to generate a failure pressure, so that the vacuum suction nozzle  3200  is released from the ferrule assembly  100  once the size and/or shape of the adhesive bump  116   a  formed on the front end surface of the ferrule assembly  100  identified by the visual recognition device reaches the predetermined size and/or shape. 
       FIG. 19 a    shows a fiber alignment module  4000 , the fiber/cable clamping module  1000  and the ferrule clamping module  2000  of  FIG. 12 , in which the fiber alignment module  4000  is separated from the ferrule clamping module  2000 ;  FIG. 19 b    shows the fiber alignment module  4000 , the fiber/cable clamping module  1000  and the ferrule clamping module  2000  of  FIG. 19 a   , in which the fiber alignment module  4000  is engaged to the ferrule clamping module  2000 , and the front end of the respective ferrule assembly  100  clamped by the ferrule clamping module  2000  is inserted into the respective alignment sleeve  4300  of the fiber alignment module  4000 . 
     As shown in  FIGS. 19 a  and 19 b   , in an embodiment of the present invention, the fiber alignment module  4000  is adapted to be engaged to the front side of the ferrule clamping module  2000 , and configured to calibrate position accuracy of the respective fiber  210  inserted into the fiber bore  121  of the respective ferrule assembly  100  and adjust an eccentricity orientation of the center O′ of the respective fiber  210  to a predetermined orientation. 
     As shown in  FIGS. 19 a  and 19 b   , in the illustrated embodiment, the fiber alignment module  4000  mainly comprises a seat body  4100  and a row of fiber alignment mechanisms (to be described later) mounted on the seat body  4100 . The row of fiber alignment mechanisms corresponds to the row of ferrule assemblies  100  clamped on the ferrule clamping module  2000 , so as to calibrate the position of the fiber  210  in the ferrule assembly  100  and adjust the eccentricity orientation of the fiber  210 . 
     In an embodiment of the present invention, alignment holes  4110 , for matching with the front alignment pins  2110  of the ferrule clamping module  2000 , are formed in both ends of a seat body  4100 . In this way, the fiber alignment module  4000  may be accurately and easily engaged to the ferrule clamping module  2000  simply by inserting the front alignment pin  2110  of the ferrule clamping module  2000  into the alignment hole  4110  of the fiber alignment module  4000 . After the fiber alignment module  4000  is engaged to the ferrule clamping module  2000 , the row of fiber alignment mechanisms are aligned to the row of ferrule assemblies  100  clamped on the ferrule clamping module  2000  one by one. 
     As described above,  FIGS. 20 a  and 21 b    show the fiber alignment mechanism of the fiber alignment module  4000 . 
     As shown in  FIGS. 20 a -21 b   , each of the fiber alignment mechanisms mainly comprises a fixation block  4500 , a row of alignment elements  4400 , a row of alignment sleeves  4300  and a row of spring elements  4200 . 
     Referring to  FIGS. 19 a , 20 a  and 20 b   , the fixation block  4500  is mounted on the seat body  4100 . Each of the alignment elements  4400  has a first end portion fixed in the fixation block  4500  and a second end portion formed with a protrudent platform  4420 . An alignment groove  4410  extending to the end of the protrudent platform  4420  in a central axis of the alignment element  4400  is formed in each of alignment elements  4400 . 
     The alignment sleeves  4300  are held in the seat body  4100 , and each of the alignment sleeves  4300  has a first end portion fitted on the second end portion of the alignment element  4400  and a second end portion opposite to the first end portion. Each of the row of spring elements  4200  has a first end  4231  extending into the respective alignment sleeve  4300  and being pressed against the alignment groove  4410  in the protrudent platform  4420  in a direction perpendicular to the central axis of the alignment element  4400  (see  FIG. 22 ). 
     As shown in  FIGS. 21 a  and 21 b   , the fiber  210  protrudes from the front end of the ferrule assembly  100 , and the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  from the second end of the alignment sleeve  4300  until a predetermined length of the fiber  210  protruding from the front end of the ferrule assembly  100  enters into the alignment groove  4410  of the alignment element  4400 . In this way, when the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  and when the fiber  210  is inserted into the alignment groove  4410  of the alignment element  4400 , the position accuracy of the fiber  210  in the fiber bore  121  of the ferrule assembly  100  is calibrated to reach position accuracy of the fiber  210  in the alignment groove  4410  of the alignment element  4400 . Please be noted that, in this embodiment, the geometric center of the alignment groove  4410  is accurately positioned at an ideal center determined with reference to an inner circumferential surface of the alignment sleeve  4300 , therefore, it ensures the calibrated center of the fiber  210  is accurately positioned at an ideal center determined with reference to an outer circumferential surface of the ferrule assembly  100 . Herein, the term ‘accurately positioned’ means that an error between the actual center and the ideal center of the fiber is less than a predetermined value, for example, less than 0.0005 mm or even more less. 
       FIG. 22  is a principle view of adjusting an eccentricity orientation of the fiber by means of the fiber alignment module of  FIG. 21   b.    
     As shown in  FIGS. 21 b    and  22 , when the front end of the ferrule assembly  100  is inserted into the alignment sleeve  4300  and when the fiber  210  is inserted into the alignment groove  4410  of the alignment element  4400 , the first end  4231  of the spring element  4200  is pressed against the fiber  210  inserted into the alignment groove  4410 , so that an eccentricity orientation of a center O′ of the fiber  210  with respect to a center O of the alignment element  4400  is adjusted to a predetermined orientation and held in the predetermined orientation. 
     As shown in  FIGS. 21 b    and  22 , the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  is adjusted to be just below the center O of the alignment element  4400 . 
     In an exemplary embodiment of the present invention, after the center O′ of the fiber  210  is adjusted to be just below the center O of the alignment element  4400 , an eccentricity orientation mark is formed on an outer surface of the ferrule assembly  100  to identify the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400 . In an alternative embodiment, after the center O′ of the fiber  210  is adjusted to be just below the center O of the alignment element  4400 , an existing feature on the ferrule assembly  100  may be used as an eccentricity orientation mark to identify the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400 . In an exemplary embodiment of the present invention, the eccentricity orientation mark may be any mark, such as, notching mark, printing mark or any other visible mark, located on the ferrule  120  or the rear seat  110  of the ferrule assembly  100 . 
     In another exemplary embodiment, as shown in  FIG. 23 , the injection hole  103  formed in the rear seat  110  may be served as the eccentricity orientation mark. In this way, it is unnecessary to individually form an eccentricity orientation mark on the ferrule assembly  100 . Referring to  FIG. 23  again, in the illustrated embodiment, when the injection hole  103  is used as the eccentricity orientation mark, it is possible to determine the correct orientation, for example, an orientation when the injection hole  103  is positioned vertically upward, of the ferrule assembly  100  with respect to a housing  300  of a fiber optic connector based on the injection hole  103 . In the illustrated embodiment of  FIG. 23 , after the ferrule assembly  100  with the optical cable  200  is inserted into the connector housing  300  based on the correct orientation, other members, such as, a spring  400 , a spring seat  500 , etc., of the connector may be subsequently mounted in the connector housing  300 , and the fiber optic connector is assembled. Please be noted that the present invention is not limited to this, the spring  400 , the spring seat  500  and the ferrule assembly  100  may be pre-assembled together to form an integral member, and then they, as the integral member, may be mounted in the connector housing  300  at one time. 
     In an exemplary embodiment of the present invention, after the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  is adjusted to be just below the center O of the alignment element  4400 , the fiber  210  is fixed in the though hole  121  of the ferrule assembly  100  by the cured adhesive  116 . In this way, the position calibration and the eccentricity orientation adjustment of the fiber  210  are finished. 
     Referring to  FIGS. 20 a   - 22  again, in the illustrated embodiment, the spring element  4200  is configured to be a cantilever spring piece, and the second end  4210  of the spring element  4200  is connected to the fixation block  4500  by a screw  4211 . A press force F exerted on the fiber  210  by the first end  4231  of the spring element  4200  is adjusted to adapt to different diameters of fibers by controlling a distance of screwing the screw  4211  into a threaded hole  4111  in the fixation block  4500 . 
     Although it is not shown, in another embodiment of the present invention, the eccentricity orientation of the center O′ of the fiber  210  with respect to the center O of the alignment element  4400  may be controlled by the adjusting the press force F. For example, it is possible to adjust the center O′ of the fiber  210  to a position just above the center O of the alignment element  4400  or just overlapping with the center O of the alignment element  4400  by adjusting the press force F. 
     In an exemplary embodiment of the present invention, as shown in  FIGS. 20-22 , a positioning slot  4221  is formed in the spring element  4200 , and a protruding positioning key  4121  is formed on the fixation block  4500 . The positioning key  4121  is fitted in the positioning slot  4221  to hold the position of the spring element  4200 , so as to keep the position of the spring element  4200  in a direction perpendicular to the central axis of the alignment element  4400  and the press force F (a direction perpendicular to the positioning slot  4221  shown in  FIG. 20 a   ) unchanged. 
     Referring to  FIG. 20 a    again, in the illustrated embodiment, the spring element  4200  comprises a first sheet portion  4230  substantially parallel to the central axis of the alignment element  4400  and a second sheet portion  4220  substantially perpendicular to and integrally connected to the first sheet like portion  4230 . The positioning slot  4221  is formed in both the first sheet portion  4230  and the second sheet portion  4220 . In this embodiment, the positioning slot  4221  is formed to include two portions substantially perpendicular to and communicated with each other, improving the positioning reliability and precision of the positioning slot  4221 . 
     Referring to  FIG. 20 a    again, in the illustrated embodiment, a notch  4330  is formed in the alignment sleeve  4300 , and the first end  4231  of the spring element  4200  enters into the alignment sleeve  4300  through the notch  4330 . 
     According to another general concept of the present invention, there is provided a method for manufacturing a fiber optic ferrule device, comprising steps of: providing a plurality of ferrule assemblies and a plurality of optical cables, each of optical cables having a section of bared fiber at an end thereof; inserting the fibers into fiber bores of the respective ferrule assemblies until each of the fibers protrudes a predetermined distance from a front end surface of the respective ferrule assembly; providing the apparatus as mentioned in the above embodiments; engaging the ferrule clamping module and the fiber/cable clamping module together; clamping and fixing the ferrule assemblies provided with the fibers on the ferrule clamping module; clamping and fixing a section of each of optical cables behind the ferrule clamping module on the fiber/cable clamping module; injecting an adhesive into the fiber bores of the respective ferrule assemblies; engaging the vacuum suction module to the ferrule clamping module, and fitting vacuum suction nozzles of the vacuum suction module on the front ends of the respective ferrule assemblies to suck the adhesive, so that the adhesive flows to the front end surface of the respective ferrule assembly through a gap between the fiber and the fiber bore until a predetermined size of adhesive bump is formed on the front end surface of the respective ferrule assembly; removing the vacuum suction module from the ferrule clamping module; engaging the fiber alignment module to the ferrule clamping module, so that the front end of each of the ferrule assemblies is inserted into the respective alignment sleeve until a predetermined length of the fiber protruding from the front end of the ferrule assembly enters into the alignment groove of the alignment element; and curing the adhesive to fix the fibers in the fiber bores of the respective ferrule assemblies. 
     Hereafter, it will describe a method of manufacturing a fiber optic ferrule device with reference to  FIGS. 4 a , 4 b   ,  8 - 21  according to an exemplary embodiment of the present invention, and the method mainly comprises following steps of: 
     S 300 : providing a plurality of ferrule assemblies  100  (for example, the ferrule assembly  100  shown in  FIGS. 4 a  and 4 b    or  FIGS. 2 a -3 b , 5 a -7 b   ) and a plurality of optical cables  200 , each of optical cables  200  having a section of bared fiber  210  at an end thereof, and each of the ferrule assemblies  100  is not filled with adhesive; 
     S 301 : as shown in  FIG. 9 a   , inserting the fibers  210  into fiber bores  121  of the respective ferrule assemblies  100  until each of the fibers  210  protrudes a predetermined distance from a front end surface of the respective ferrule assembly  100 ; 
     S 302 : as shown in  FIG. 12 , providing the apparatus for manufacturing the fiber optic ferrule device set forth in the above embodiments; 
     S 303 : as shown in  FIG. 14 , engaging the ferrule clamping module  2000  and the fiber/cable clamping module  1000  together; 
     S 304 : as shown in  FIGS. 15 a  and 15 b   , clamping and holding the ferrule assemblies  100  provided with the fibers  210  on the ferrule clamping module  2000 ; 
     S 305 : as shown in  FIG. 15 c   , clamping and holding a section of each of optical cables  200  behind the ferrule clamping module  2000  on the fiber/cable clamping module  1000 ; 
     S 306 : as shown in  FIG. 9 b   , injecting an adhesive  116  into the fiber bores  121  of the respective ferrule assemblies  100 ; 
     S 307 : as shown in  FIGS. 8, 9   c ,  18   a  and  18   b , engaging the vacuum suction module  3000  to the ferrule clamping module  2000 , and fitting vacuum suction nozzles  3200  of the vacuum suction module  3000  on the front ends of the respective ferrule assemblies  100  to suck the adhesive  116 , so that the adhesive  116  flows to the front end surface of the respective ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined size of adhesive bump  116   a  is formed on the front end surface of the respective ferrule assembly  100 , as shown in  FIG. 9   d;    
     S 308 : removing the vacuum suction module  3000  from the ferrule clamping module  2000 ; 
     S 309 : as shown in  FIGS. 19 a , 19 b   ,  20 - 21 , engaging the fiber alignment module  4000  to the ferrule clamping module  2000 , so that the front end of each of the ferrule assemblies  100  is inserted into the respective alignment sleeve  4300  until a predetermined length of the fiber  210  protruding from the front end of the ferrule assembly  100  enters into the alignment groove  4410  of the alignment element  4400 ; and 
     S 310 : curing the adhesive  116  to fix the fibers  210  in the fiber bores  121  of the respective ferrule assemblies  100 . 
     Please be noted that the present invention is not limited to this, the step S 306  may be performed after inserting the plurality of fibers  210  into the fiber bores  121  of the plurality of ferrule assemblies  100  and before engaging the vacuum suction module  3000  to the ferrule clamping module  2000 . That is, it may not be necessary to perform the step S 306  after clamping and fixing the plurality of optical cables  200  on the fiber/cable clamping module  1000 . For example, in another embodiment of the present invention, the method of manufacturing a fiber optic ferrule device may comprise following steps of: 
     S 400 : providing a plurality of ferrule assemblies  100  (for example, the ferrule assembly  100  shown in  FIGS. 4 a  and 4 b    or  FIGS. 2 a -3 b , 5 a -7 b   ) and a plurality of optical cables  200 , each of optical cables  200  having a section of bared fiber  210  at an end thereof, and each of the ferrule assemblies  100  is not filled with the adhesive; 
     S 401 : as shown in  FIG. 9 a   , inserting the fibers  210  into fiber bores  121  of the respective ferrule assemblies  100  until each of the fibers  210  protrudes a predetermined distance from a front end surface of the respective ferrule assembly  100 ; 
     S 402 : as shown in  FIG. 12 , providing the above described apparatus for manufacturing the fiber optic ferrule device; 
     S 403 : as shown in  FIG. 14 , engaging the ferrule clamping module  2000  and the fiber/cable clamping module  1000  together; 
     S 404 : as shown in  FIGS. 15 a  and 15 b   , clamping and holding the ferrule assemblies  100  provided with the fibers  210  on the ferrule clamping module  2000 ; 
     S 405 : as shown in  FIG. 9 b   , injecting an adhesive  116  into the fiber bores  121  of the respective ferrule assemblies  100 ; 
     S 406 : as shown in  FIG. 15 c   , clamping and fixing a section of each of optical cables  200  behind the ferrule clamping module  2000  on the fiber/cable clamping module  1000 ; 
     S 407 : as shown in  FIGS. 8, 9   c ,  18   a  and  18   b , engaging the vacuum suction module  3000  with the ferrule clamping module  2000 , and fitting vacuum suction nozzles  3200  of the vacuum suction module  3000  on the front ends of the respective ferrule assemblies  100  to suck the adhesive  116 , so that the adhesive  116  flows to the front end surface of the respective ferrule assembly  100  through a gap between the fiber  210  and the fiber bore  121  until a predetermined size of adhesive bump  116   a  is formed on the front end surface of the respective ferrule assembly  100 , as shown in  FIG. 9   d;    
     S 408 : removing the vacuum suction module  3000  from the ferrule clamping module  2000 ; 
     S 409 : as shown in  FIGS. 19 a , 19 b , 20 a -21 b   , engaging the fiber alignment module  4000  with the ferrule clamping module  2000 , so that the front end of each of the ferrule assemblies  100  is inserted into the respective alignment sleeve  4300  until a predetermined length of the fiber  210  protruding from the front end of the ferrule assembly  100  enters into the alignment groove  4410  of the alignment element  4400 ; and 
     S 410 : curing the adhesive  116  to fix the fibers  210  in the fiber bores  121  of the respective ferrule assemblies  100 . 
     In the illustrated embodiments, although only a single-mode single-fiber ferrule assembly is shown and described, the present invention is not limited to this. The above embodiments of the present invention are also adapted to a single-mode multi-fiber ferrule assembly, a multi-mode single-fiber ferrule assembly, a multi-mode multi-fiber ferrule assembly or other type of ferrule device. With the solutions of the present invention, a fiber optic connector with high precision and low insertion loss may be produced by a low precision ferrule (a fiber bore of the low precision ferrule has a diameter far larger than that of a fiber bore of a high precision ferrule, and an eccentricity of the center of the fiber bore of the low precision ferrule with respect to a positioning reference is far larger than that of the center of the fiber bore of the high precision ferrule with respect to a positioning reference). 
     Please be noted that the finished ferrule assembly is also referred as the fiber optic ferrule device or the ferrule device herein, in order to differentiate the finished ferrule assembly from the unfinished ferrule assembly. 
     It should be appreciated for those skilled in this art that the above embodiments are intended to be illustrated, and not restrictive. For example, many modifications may be made to the above embodiments by those skilled in this art, and various features described in different embodiments may be freely combined with each other without conflicting in configuration or principle. 
     Although several exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 
     As used herein, an element recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.