Optical connector ferrule for supporting an optical fiber tape conductor, optical connector, method for assembling an optical connector and optical fiber inserting jig

An optical connector ferrule for supporting an optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers, comprising: a plurality of fiber inserting holes which are arranged at a plurality of steps and into which the optical fibers are inserted; a guide portion for guiding insertion of optical fibers, formed so as to have an end communicating with a fiber inserting end of each of the fiber inserting holes, the guide portion extending along an axial direction of the fiber inserting holes; and a contact portion formed to be a predetermined distance spaced from an opening end opposed to the fiber inserting end of each of the fiber inserting holes along the axial direction of the fiber inserting holes, the contact portion being brought in contact with an exposed fiber side end of a tape member of the optical fiber tape conductor when each of the optical fibers of the optical fiber tape conductor is inserted into each of the fiber inserting holes.

FIELD OF THE INVENTION

The present invention relates to an optical connector ferrule, an optical connector, an optical connector assembling method and an inserting jig for inserting an optical fiber tape into the ferrule, which are used at a junction between optical fibers in opto-electronic communication or at a junction of an optical module of an optical semiconductors or the like.

RELATED ART

With a developing information network including an optical fiber network, transmission capacity is rapidly increasing. Accordingly, demands for high density are growing in an optical connector ferrule used in a junction between optical fibers or a junction of an optical module of an optical semiconductor or the like.

In order to realize the high density, a multi-core optical connector ferrule is being pursued so as to allow batch connection of a plurality of optical fibers while maintaining an appearance shape and size of a conventional ferrule.

Particularly, in these days, a one-step multi-core (1 step×n cores) ferrule which has one step of multi-core fiber insertion holes (pin holes) for supporting a plurality of optical fibers is being replaced with a multi-step multi-core (m steps×n cores) ferrule which has realized higher density.

FIG. 1-9shows one example of an optical connector ferrule50which has multi-core (n filaments) fiber inserting holes provided at multi-step (m steps) (m steps×n cores connector ferrule). More specifically, the optical connector ferrule50shown inFIG. 1-9is a 60-core ferrule having n-core (=12) fiber inserting holes51aligned along the horizontal direction in the figure provided at m-step (=5) along the vertical direction in the figure.

This optical connector ferrule50fixedly supports ends of exposed optical fibers (here, bare fibers) of multi-core optical fiber tape conductors53corresponding to the above-mentioned multi-core fiber inserting holes by the use of the multi-core fiber inserting holes so as to facilitate connection to an optical connector, an optical module or the like of a connecting counterpart.

The outer diameter of an optical fiber and the inner diameter of a fiber inserting hole of the ferrule are both extremely small. To improve workability of inserting each optical fiber to a corresponding fiber inserting hole, the ferrule includes a guide groove for guiding insertion of each optical fiber into the corresponding inserting hole.

FIG. 1-10is a vertical sectional view of the ferrule50shown inFIG. 1-9, taken along the line in the step direction which passes through the centers of the vertically aligned fiber insertion holes51. As shown inFIG. 1-10, a guide groove52at each step of the multi-core optical connector ferrule50have an end extending axially longer than that of a one-step higher guide groove52.

In assembling an optical connector with use of such a multi-core optical connector ferrule50, a plurality of (5) multi-core optical fiber tape conductors53a1to53a5corresponding in number to the steps are prepared. Then, a tape portion of a first-step multi-core optical fiber tape conductor53a1among the prepared multi-core optical fiber tape conductors53a1to53a5is peeled off so as to have exposed optical fibers (bare fibers)54a1, which are inserted into undermost (first-step) fiber inserting holes51a1.

Then, the optical fibers54a1are inserted into the fiber inserting holes51a1in such a manner that exposed fiber side ends (peeled tape ends)53b1in the multi-core optical fiber tape conductor53a1make contact with the guide grooves52of the fiber inserting holes51a1(refer to FIG.1-11).

Next, optical fibers54a2to54a5of the respective multi-core optical fiber tape conductors53a2to53a5are inserted into the respective fiber inserting holes51a2to51a5of second and later steps (second to fifth steps) sequentially from the lower step.

At this time, the optical fibers54a2to54a5of the second to fifth steps are inserted into the respective fiber inserting holes51a2to51a5in such a manner that positions of exposed fiber side ends (tape peeled ends)53b2to53b5of the multi-core optical fiber tape conductors53a2to53a5along the axial direction of the fiber inserting holes are aligned with a position of the exposed fiber side end53b1of the first step along the axial direction of fiber inserting holes (refer to FIG.1-11).

In this way, while the optical fibers54a1to54a5of the respective multi-core optical fiber tape conductors53a1to53a5are inserted in the respective fiber inserting holes51a1to51a5, a fiber fixing member such as an adhesive agent is injected from a window55into the ferrule to fix the optical fibers54a1to54a5, thereby assembling an optical connector.

For the case of an optical connector ferrule50with n-core fiber inserting holes arranged at multiple steps (m steps×n cores optical connector ferrule), a hole pitch between vertically adjacent fiber inserting holes of51a1to51a5(vertical pitch between the centers of vertically adjacent holes) is typically 0.25 mm (“vertical” or “vertically” here means “in the direction of steps”). On the other hand, the vertical thickness of each of the multi-core optical fiber tape conductors53a1to53a5is typically 0.3 mm.

Accordingly, between vertical positions of the axes of the fiber inserting holes51a2to51a5of second and later steps and vertical positions of the centers of the corresponding multi-core optical fiber tape conductors53a2to53a5, there may occur a misalignment which corresponds to the difference between the vertical pitch between the fiber inserting holes and the thickness of the multi-core optical fiber tape conductors.

Here, the misalignment between the vertical position of the undermost-step (first-step) fiber inserting holes51a1and the vertical position of the corresponding multi-core optical fiber tape conductor53a1depends on the inner configuration of the ferrule. When this misalignment is α, a misalignment Gk between the vertical position of the axis of the fiber inserting holes51akof kthstep from the bottom step {1≦k≦m (=5)} and the vertically center position of the multi-core optical fiber tape conductor53akis given by the following equation (1-1) using a difference 0.05 mm between the vertical pitch of fiber inserting holes and the thickness of each multi-core optical fiber tape conductor.
Gk=0.05(k−1)+α  EQUATION 1-1

Seen from the equation (1-1), the larger the step number k is, the larger the aforementioned misalignment Gk becomes. Therefore, when the optical fibers54a1to54a5of the multi-core optical fiber tape conductors53a1to53a5are inserted into the respective fiber inserting holes51a1to51a5while the misalignment Gk is left between the vertical positions of the axes the fiber inserting holes in the second and later steps and the vertically center position of the respective multi-core optical fiber tape conductors of the respective steps, there occurs a bend particularly in each of the optical fibers54a2to54a5corresponding to the second and later steps, which is seen inFIG. 1-11. Accordingly, the optical fibers54a2to54a5in the corresponding second and later steps are fixed bending.

The bends of the optical fibers (bare fibers) might cause an increase in connection loss from the viewpoint of the optical characteristics. Further, from the viewpoint of intensity, if a bending portion becomes deformed due to shrinking and swelling in the ferrule caused by temperature change, moisture taking or the like, this might induce a break in bare fibers.

Such a multi-core optical connector ferrule is manufactured principally by molding with plastic resin in view of mass production, cost and the like. Besides, when an optical connector is assembled using the aforementioned multi-core optical connector ferrule, multi-core optical fiber tape conductors corresponding in number to the steps are prepared. Tape members of the prepared multi-core optical fiber tape conductors are peeled off to expose optical fibers (i.e. bare fibers) which are inserted into the respective fiber inserting holes, and a fiber fixing member such as an adhesive agent is injected from a window to the inside of the ferrule, to fix the optical fibers, thereby assembling an optical connector.

In order to further increase density of the above-described multi-step multi-core ferrule, it is necessary to lower a horizontal pitch between horizontally adjacent optical fibers and a vertical pitch between vertically adjacent optical fibers. In particular, demands for a smaller vertical pitch between vertically adjacent optical fibers than the thickness of the fiber tape conductor are growing so as to obtain high density.

For example, the thickness of a fiber tape is typically 0.3 mm and the pitch between vertically adjacent optical fibers is set at 0.25 mm. with this configuration, if a misalignment between the axis of the first-step fiber inserting holes51a1and the center of an exposed fiber (bare fiber) side end (peeled tape end) of an optical fiber tape conductor which is to be inserted into the first-step inserting holes is 0, there occurs, between the axis of the fiber inserting holes of each of second and later steps and the center of an exposed fiber side end of the corresponding optical fiber tape conductor, a vertical misalignment, which corresponds to a difference between the vertical pitch of the fiber inserting holes and the thickness of the fiber tape conductor.

Thus, when the bare fibers of the multi-core optical fiber tape conductors are inserted into the respective fiber inserting holes in the situation where a vertical misalignment is left between the axis of the fiber inserting holes of each of second and later steps and the center of the exposed fiber side end of the corresponding optical fiber tape conductor, there occurs a bend particularly in each of the optical fibers corresponding to 2 or more steps. In other words, bare fibers of the optical fiber tape conductors corresponding to the second or later steps are fixed while they are bending.

The bends of the bare fibers of the optical fiber tape conductors are found between fiber inserting ends of the fiber inserting holes and the bare fibers side ends of the optical fiber tape conductors. Particularly, when the steps are increased in number, occurrence of bends becomes more remarkable.

Conventionally, there has been used an optical connector called MT (Mechanical Transferable) connector in connecting of optical fibers. The MT connector is configured by inserting an optical fiber ribbon (hereinafter referred to as “optical fiber tape”) B of plural fiber elements arranged in parallel into a ferrule C to fix the optical fiber tape therein, as shown inFIG. 3-7. Specifically, as shown inFIG. 3-8A, coating of an end of the optical fiber tape B is peeled off to expose optical fibers A of appropriate length, and a boot D is put around the coating portion next to the bare fibers A. Then, the optical fiber tape B is manually inserted into the ferrule C through a slot E of the ferrule C, and the optical fibers A are inserted along the bottom surface of optical fiber alignment grooves F ahead of the slot E.

Then, as shown inFIG. 3-8B, the optical fibers A are allowed to pass through optical fiber holes G communicating from the optical fiber grooves F so that tip ends of the optical fibers A are protruding form a contact side face H of the ferrule C. Then, the adhesive agent is injected through an adhesive agent injecting hole J of the ferrule C to fix the optical fiber tape B and the ferrule C. Later, the optical fibers A protruding form the contact side face H of the ferrule C are polished off so that the tip ends of the optical fibers A and the contact side face H of the ferrule C are substantially flush, as shown inFIGS. 3-8Cand3-8D.

At present, there has been developed various jigs for allowing the aforementioned optical fibers A to pass through the optical fiber holes G. An example is shown inFIGS. 3-9Aand3-9B. This jig is formed by providing a ferrule inserting portion P protruding from a side face N of a base member L which has a guide groove M for guiding a optical fiber tape B onto a upper surface K. The side face N of the base material L is provided with a guide pin Q in such a manner that the guide pin Q is protruding from the face N. This guide pin Q is inserted into a guide pin hole R (shown inFIG. 3-7) of the ferrule C to be set in the ferrule inserting portion P so as to position the ferrule C. The ferrule inserting portion P is axially supported by a fixing pin S so as to turn in the directions indicated by an arrow shown inFIG. 3-9A.

Inserting of the optical fibers A into the optical fiber inserting holes G of the ferrule C by means of jigs shown inFIGS. 3-9Aand3-9B is carried out in the following manner. First, the ferrule C is set at ferrule inserting portion P as shown inFIG. 3-9B. Then, also shown inFIG. 3-9B, optical fiber tape B is set in the guide groove M and slid to the ferrule inserting portion P side along the guide groove M so as to insert the optical fibers A from the slot E into the ferrule C. More specifically, the optical fibers A are inserted in the vicinity of the optical fiber alignment grooves F. Then, the ferrule inserting portion P is turned as shown inFIG. 3-10to put the optical fibers onto the optical fiber alignment grooves F. Once the optical fiber A is put on the optical fiber groove F, the optical fiber tape is inserted further into the ferrule C along the guide groove M to as to allow the optical fibers A pass through the optical fiber G ahead of the optical fiber groove F.

The jigs shown inFIGS. 3-9Aand3-9B have problems mentioned below:

(1) When coating of an optical fiber tape B is removed to expose optical fibers A, the exposed optical fibers A are widened as shown inFIG. 3-11and it is sometimes difficult to keep the optical fibers aligned. If the optical fibers A are not aligned, they are not allowed to be placed in fiber alignment grooves F of a ferrule C shown inFIG. 3-7and the like, which makes it difficult to insert the optical fibers A into fiber inserting holes G.

(2) In the case of a multi-core ferrule which has fiber inserting holes formed at plural steps, optical fibers are sequentially inserted into the undermost-step fiber inserting holes to the uppermost-step fiber inserting holes. For this reason, when optical fibers are inserted into fiber inserting holes of the second or later step, a previously inserted optical fiber tape is left in guide groove M shown inFIG. 3-9B, and another optical fiber tape has to be superposed on the previous one. However, conventionally, there was only a jig for multi-core ferrule which has fiber inserting holes formed at a step. As shown inFIG. 3-12, the jig has a guide groove M of depth smaller than the thickness of the optical fiber tape B, and when two or more optical fiber tapes B are superposed, the second and later optical fiber tapes can not be positioned. In addition, as shown inFIGS. 3-13Aand3-13B, distortion or deformation of coating per se of the optical fiber tape B sometimes makes it difficult to superpose another optical fiber tape B on the previously inserted optical fiber tape B. In any event, a previously inserted optical fiber tape prevents inserting operation of a next optical fiber tape, which makes working efficiency significantly worse.

(3) According to a jig as shown inFIGS. 3-9Aand3-9B, a ferrule C is positioned by inserting guide pins Q provided protruding from a side face N of a base member L into guide pin holes R of the ferrule C. Therefore, in order to remove the ferrule C from a ferrule inserting portion P after inserting operation, the ferrule has to be moved in the axial direction of the guide pins to be removed from the guide pins. However, since the axial direction of the guide pins is in parallel with the inserting direction of the optical fibers, the ferrule which is moved in the axial direction of the guide pins might have the inserted optical fibers detached from the ferrule.

The present invention was carried out in view of the foregoing. An object of the present invention is to provide an optical connector ferrule, an optical connector and an optical connector assembling method which enable bends of optical fibers (base fibers) to be reduced so as not to influence on the optical characteristics and intensity of the optical fibers, thereby preventing deterioration of the optical characteristics and intensity of the whole ferrule and the whole optical connector due to the aforementioned bends of the optical fibers.

SUMMARY OF THE INVENTION

An embodiment of an optical connector ferrule of the present invention is an optical connector ferrule for supporting an optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers, comprising:

a plurality of fiber inserting holes which are arranged at a plurality of steps and into which said optical fibers are inserted;

a guide groove for guiding insertion of optical fibers, formed so as to have an end communicating with a fiber inserting end of each of said fiber inserting holes, said guide groove extending along an axial direction of said fiber inserting holes; and

a contact portion formed to be a predetermined distance spaced from an opening end opposed to the fiber inserting end of each of said fiber inserting holes along the axial direction of said fiber inserting holes, said contact portion being brought in contact with an exposed fiber side end of a tape member of said optical fiber tape conductor when each of said optical fibers of said optical fiber tape conductor is inserted into each of said fiber inserting holes.

Another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule in which a predetermined distance from the opening end of each of said fiber inserting holes to said contact portion along the axial direction of said fiber inserting holes is determined in such a manner that when each of said optical fibers of said optical fiber tape conductor is inserted into a corresponding one of said fiber inserting holes at the respective steps, each curvature radius of r1to rm (where m is an integer of at least 2, corresponding to the number of the steps) of bends of the optical fibers at the respective steps becomes at least a predetermined value.

Yet another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule comprising:

a plurality of fiber inserting holes which are arranged at a plurality of steps and into which optical fibers are inserted; and

a guide portion for guiding insertion of optical fibers, formed so as to communicate with a fiber inserting end of each of said fiber inserting holes, said guide portion extending along an axial direction of said fiber inserting holes,

in which a length of said guide portion along the axial direction of said fiber inserting holes is set in a range of 0.3 mm to 0.7 mm.

Still another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule comprising a first side face having an opening face which includes opening ends of said plurality of fiber inserting holes; and a second side face provided communicating with a vertical edge of said first side face along and extending along the axial direction of said fiber inserting holes, said second side face having a window through which is injected a fiber fixing member for fixing the optical fibers inserted into said fiber inserting holes, respectively,

in which a length from said first side face to a window formed portion in said second side face along a direction of inserting said optical fibers is set at 2.0 mm or longer.

Still yet another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule in which said optical fibers are optical fibers corresponding in number to said fiber inserting holes, being exposed by peeling off a tape member of an end of an optical fiber tape conductor coated with a tape member,

said optical connector ferrule comprising a slot, formed opposed to said first side face, for inserting a plurality of optical fiber tape conductors corresponding to said fiber inserting holes at the respective steps, and

a position of said slot is determined in such a manner that when the optical fibers of each of said optical fiber tape conductors are inserted individually into the fiber inserting holes at a desired step of the plurality of steps via said slot, a vertical misalignment between a central axis of each of said fiber inserting holes and a center of an exposed fiber side end of a corresponding one of said optical fiber tape conductors becomes 0.

Another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule for supporting an optical fiber tape conductor provided with a plurality of optical fibers coated with a tape member, said optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers, comprising:

a plurality of fiber inserting holes which are arranged at a plurality of steps and into which said optical fibers are inserted;

a guide portion for guiding insertion of optical fibers, formed so as to communicate with a fiber inserting end of each of said fiber inserting holes, said guide portion extending along an axial direction of said fiber inserting holes,

in which a vertical misalignment between a central axis of said fiber inserting holes at each step into which when the optical fibers of said optical fiber tape conductor are inserted and a center of an exposed fiber side end in the tape member of said optical fiber tape conductor is indicated by G1to Gn (where n is an integer of at least 2, corresponding to the number of the steps), and a distance between a connecting end of the guide portion corresponding to said each of fiber inserting holes and the exposed fiber side end in the tape member of the optical fiber tape conductor is indicated by D1to Dn, the misalignment of G1to Gn and the distance of D1to Dn are used to express each curvature radius of r1to rn of bends of the optical fiber tape conductors of the respective steps, and a length of said guide portion along the axial direction of said fiber inserting holes is determined such that the curvature radius of r1to rn becomes at least a predetermined value.

Yet another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule in which in addition to a requirement of the curvature radii r1to rn of the bends, the length of said guide portion along the axial direction of said fiber inserting holes is determined in such a manner that a misalignment of either step in misalignments of G1to Gn is set at 0.

Still another embodiment of the optical connector ferrule of the present invention is an optical connector ferrule having a first side face having an opening face which includes opening ends of said plurality of fiber inserting holes; and a second side face provided communicating with a vertical edge of said first side face and extending along the axial direction of said fiber inserting holes, said second side face having a window through which is injected a fiber fixing member for fixing the optical fibers inserted in said fiber inserting holes,

in which the length of said guide portion along the axial direction of said fiber inserting holes is determined in such a manner that the curvature radius of r1to rn of the bends is set at 30 mm or longer, a length from said first side face to a window formed portion in said second side face along a direction of inserting said optical fibers is set at 2.0 mm or longer.

An embodiment of an optical connector of the present invention is an optical connector comprising: an optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers; and a ferrule for supporting said optical fiber tape conductor, said ferrule comprising:

a plurality of fiber inserting holes which are arranged at a plurality of steps and into which said optical fibers are inserted;

a guide portion for guiding insertion of optical fibers, formed so as to have an end communicating with a fiber inserting end of each of said fiber inserting holes, said guide portion extending along an axial direction of said fiber inserting holes; and

a contact portion formed to be a predetermined distance spaced from an opening end opposed to the fiber inserting end of each of said fiber inserting holes along the axial direction of said fiber inserting holes, said contact portion being brought in contact with an exposed fiber side end of a tape member of said optical fiber tape conductor when each of said optical fibers of said optical fiber tape conductor is inserted into a corresponding one of said fiber inserting holes.

Another embodiment of an optical connector of the present invention is an optical connector comprising: a ferrule; and an optical fiber tape conductor provided with a plurality of optical fibers coated with a tape member, said optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers,

said ferrule comprising:a plurality of fiber inserting holes which are arranged at a plurality of steps and into which said optical fibers are inserted;a guide portion for guiding insertion of optical fibers, formed so as to communicate with a fiber inserting end of each of said fiber inserting holes, said guide portion extending along an axial direction of said fiber inserting holes;a first side face having an opening face which includes opening ends of said plurality of fiber inserting holes;a second side face provided communicating with a vertical edge of said first side face and extending along the axial direction of said fiber inserting holes, said second side face having a window through which is injected a fiber fixing member for fixing the optical fibers inserted in said fiber inserting holes; anda slot provided at a side face opposed to said first side face, and

said optical fiber tape conductor of which the optical fibers and a tape member are inserted into said ferrule through said slot, each of the optical fibers being supported by being inserted into a corresponding one of said fiber inserting holes via said guide portion,

a length of said guide portion along the axial direction of said fiber inserting holes being set in a range of 0.3 mm to 0.7 mm,

a length from said first side face to a window formed portion in said second side face along a direction of inserting said optical fibers is set at 2.0 mm or longer, and

a distance between an exposed fiber side end face of the tape member of said optical fiber tape conductor inserted in said ferrule and an opening end face of said slot is set at 0.5 mm or longer.

An embodiment of an optical connector assembling method of the present invention is an optical connector assembling method for assembling an optical connector with the use of an optical fiber tape conductor having an end of which a coating is peeled off to expose optical fibers, comprising the steps of:

preparing a ferrule which has: a plurality of fiber inserting holes which are arranged at a plurality of steps and into which said optical fibers are inserted; a guide portion for guiding insertion of optical fibers, formed so as to have an end communicating with a fiber inserting end of each of said fiber inserting holes, said guide portion extending along an axial direction of said fiber inserting holes; and a contact portion formed to be a predetermined distance spaced from an opening end opposed to the fiber inserting end of each of said fiber inserting holes along the axial direction of said fiber inserting holes; and

inserting each of said optical fibers of said optical fiber tape conductor inserted into a corresponding one of said fiber inserting holes so that an exposed fiber side end of a tape member of said optical fiber tape conductor is brought in contact with said contact portion.

An embodiment of an optical fiber inserting jig of the present invention is an optical fiber inserting jig comprising a ferrule set stage for setting a ferrule and a fiber set stage for setting an optical fiber tape conductor, said optical fiber tape conductor, which has an edge of which a coating is peeled off to expose optical fibers, being set on said fiber set stage and slid toward said ferrule set stage, thereby allowing the optical fibers to be inserted into fiber inserting holes of the ferrule set on said ferrule set stage, wherein

a fiber alignment portion for aligning the optical fibers is provided on said ferrule set stage, said fiber set stage or between said ferrule set stage and said fiber set stage, said fiber alignment portion having more than two fiber inserting grooves divided by a plurality of dividing plates and allowing the optical fibers to be aligned by inserting the optical fiber into the respective fiber inserting grooves.

Another embodiment of the optical fiber inserting jig of the present invention is an optical fiber inserting jig in which said fiber set stage is slidable along a direction perpendicular to an axial direction of the optical fiber tape conductor set on said fiber set stage, an optical fiber tape conductor is allowed to be set on said fiber set stage once a previously-inserted optical fiber tape conductor is taken away under said fiber set stage.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1-1is a schematic perspective view illustrating a configuration of an optical connector ferrule (hereinafter referred to simply as a “ferrule”)1for assembling an optical connector according to an embodiment of the present invention and a configuration of a plurality of optical fiber tape conductors (five optical fiber tape conductors2a1to2a5in this embodiment) which are inserted into the ferrule to be fixedly supported. The ferrule of the present invention is made of thermal plastic resin (for example, PPS (polyphenylene sulfide) resin) or thermosetting resin (for example, epoxy resin).

Further,FIG. 1-2is a vertical sectional view of the ferrule1shown inFIG. 1-1taken along the line passing through the centers of vertically aligned fiber inserting holes3or the line II—II in the followingFIG. 1-3.

As shown inFIGS. 1-1and1-2, the ferrule1has the shape of a square and is integrally formed by molding with a material of plastic resin, for example.

More specifically, the ferrule1has a plurality of fiber inserting holes3(“a plurality of”: “12 cores” in the present embodiment) along the longitudinal direction of the ferrule1. The plurality of fiber inserting holes3are arranged at plural steps along the vertical direction of the ferrule (plural: first to fifth steps in the present embodiment). Besides, the plurality of fiber inserting holes3at each step are spaced with a predetermined pitch along the horizontal direction of the ferrule1. The fiber inserting holes3are vertically spaced with a predetermined pitch.

Now in the present embodiment, 12-core fiber inserting holes3at the first step are indicated by3N1, and likewise, 12-core fiber inserting holes3in the second to fifth steps are indicated by3N2to3N5, respectively.

Optical fiber tape conductors2a1to2a5have, as shown inFIG. 1-1, a plurality of (12-core) optical fibers corresponding to the plurality of (12-core) fiber inserting holes3at the respective steps and tape members2c1to2c5for covering the plurality of optical fibers.

The optical fiber tape conductor2a1corresponding to the first step has an end of which a coating is peeled off to expose 12-core optical fibers (bare fibers)2b1. Likewise, the fiber tape conductors2a2to2a5corresponding to the second to fifth steps have ends where 12-core optical fibers2b2to2b5are exposed.

A diameter of each of the fiber inserting holes3N1to3N5is approximately the same as the diameter of each of the optical fibers2b1to2b5so as to enable the optical fibers2b1to2b5to be inserted into the respective fiber inserting holes.

Further, the ferrule1includes a first housing5having an opening face with opening ends of the plurality of fiber inserting holes3arranged at the plural steps, said opening face being a contact side face5ato another optical device such as an optical connector, an optical module or the like. Further, the ferrule1includes a second housing6which extending from the first housing5along the axial direction of the fiber inserting holes.

The first housing5includes a upper surface7which extends from an upper edge of the contact side face5ato the second housing6along the axial direction of the fiber inserting holes, and this upper surface7has a window8formed for injecting an optical fiber fixing member (for example, adhesive agent) after inserting optical fibers of the optical fiber tape conductors2into the fiber inserting holes3at the respective steps.

And, the ferrule1includes guide grooves10N1to10N5for guiding insertion of the optical fibers, which are formed with the ends in contact with lower edges of the fiber inserting holes3N1to3N5of the respective steps and extend coaxially along the axial direction of the fiber inserting holes.

The first to fifth-step fiber inserting holes3N1to3N5extend up to the optical fiber inserting side of guide grooves of one-step upper fiber inserting holes, and the first to fifth guide grooves10N1to10N5and the fiber inserting holes3N1to3N5as a whole are stepped to become longer in a lower step than in a upper step, as seen from the section view inFIG. 1-2. Accordingly, the optical fiber inserting side end faces of the fiber inserting holes3N1to3N5at the respective steps are positioned farther from the contact side face5ain a lower step than in a upper step.

FIG. 1-3is a cross sectional view of the ferrule1shown inFIG. 1-2taken along upper edges of the guide grooves10N3corresponding to the third-step fiber inserting holes3N3and seen from the line III—III inFIG. 1-2.

As shown inFIGS. 1-2and1-3, the second housing6includes a slot12, provided at a face opposed to the contact side face5aof the first housing5, for inserting the optical fiber tape conductors2and a flange13formed around the slot12formed portion.

The second housing6has a contact portion15formed a predetermined distance D away from the contact side face5aalong the axial direction of the fiber inserting holes, as shown inFIGS. 1-2and1-3.

As shown inFIG. 1-3, the contact portion15is formed as protrusive portions15aand15bstepped up inwardly from faced slot inner edges6aand6bin the second housing6, respectively.

The distance D10between the protrusive portions15aand15bis set shorter than the horizontal width W10of each of exposed fiber side ends2d1to2d5in the tape members2c1to2c5of the optical fiber tape conductors2a1to2a5.

The distance D10between the protrusive portions15aand15bis set longer than the horizontal width W11between the optical fibers2b1and2b5of the optical fiber tape conductors2a1to2a5(hereinafter referred to as “optical fiber width”) so as not to prevent insertion of the optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5.

The contact portion15is formed at a position in contact with the exposed fiber side ends (end faces)2d1to2d5in the tape members2c1to2c5of the optical fiber tape conductors2a1to2a5when the optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5are inserted into the fiber inserting holes3N1to3N5of the respective step.

Further, the ferrule1includes a receiving portion16formed between the fiber inserting holes3N1to3N5including the stepped guide grooves10N1to10N5and the slot8, for receiving the optical fibers2bato2b5inserted into the fiber inserting holes3N1to3N5.

Furthermore, the ferrule1has two guide pin holes17a1and17a2, arranged at both sides of and in parallel with the fiber inserting holes3, for inserting positioning guide pins.

In thus formed ferrule1, the fiber tape conductor2a1corresponding to the first step is inserted into the receiving portion16through the slot12.

The optical fibers2b1of the optical fiber tape conductor2a1are inserted into the corresponding first-step fiber inserting holes3N1along the guide grooves10N1.

Then, the optical fibers2b1of the optical fiber tape conductor2a1are inserted into the corresponding fiber inserting holes3N1and supported by the fiber inserting holes3N1in such a way that where the exposed fiber side end2d1of the tape member2c1is in contact with the contact portion15.

In inserting of the optical fibers2b1into the fiber inserting holes3N1, since the distance D10between the protrusive portions15aand15bof the contact portion15is shorter than the horizontal width W10of each of the exposed fiber side ends (end faces)2d1to2d5, the exposed fiber side ends2d1in the tape member2c1of the optical fiber tape conductor2a1is fixed in contact with the contact portion15.

Then, the second to fifth-step optical fiber tape conductors2a2to2a5are inserted into the receiving portion16in ascending order from the second step, and the optical fibers2b2to2b5of the optical fiber tape conductors2a2to2a5are inserted into the fiber inserting holes3N2to3N5of the corresponding second to fifth steps along the guide grooves10N2to10N5.

As is the case with the first step, the optical fibers2b2to2b5of the optical fiber tape conductors2a2to2a5are inserted into the corresponding fiber inserting holes3N2to3N5in such a way the exposed fiber side ends2d2to2d5of the tape members2c2to2c5are in contact with the contact portion15, and the optical fibers are supported by the fiber inserting holes3N2to3N5. Then, the exposed fiber side ends2d2to2d5of the tape members2c2to2c5of the optical fiber tape conductors2a2to2a5are fixed in contact with the contact portion15.

FIG. 1-4is a vertical sectional view of the ferrule1and optical fiber tape conductors2a1to2a5in which first to fifth-step optical fibers2b1to2b5of the optical fiber tapes conductors2a1to2a5are inserted into the first to fifth-step fiber inserting holes3N1to3N5of the ferrule1, which view being taken along the line passing through the centers of vertically aligned fiber inserting holes3N1to3N5, corresponding toFIG. 1-2.

FIG. 1-5is a cross sectional view of the ferrule into which optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5are inserted, as shown inFIG. 1-4, which view being taken along upper edges of the guide grooves10N3corresponding to the third-step fiber inserting holes3N3and seen from the line V—V.

As shown inFIGS. 1-4and1-5, the optical fibers2a1to2a5of the optical fiber tape conductors2a1to2a5are inserted into the corresponding fiber inserting holes3N1to3N5in such a way that the exposed fiber side ends2d2to2d5of the tape members2c1to2c5are in contact with the contact portion15, and supported by the fiber inserting holes3N1to3N5.

While the optical fibers2b1to2b5are inserted into the corresponding fiber inserting holes3N1to3N5, an adhesive agent is injected in the ferrule1via the window8to fix the optical fibers2b1to2b5, thereby producing an optical connector C.

Next, operations based on the configurations of the ferrule1and connector C according to the present embodiment will be described below.

FIG. 1-6is a view illustrating bends in optical fibers54a2and54a3while optical fibers54a1to54a3of multi-core optical fiber tape conductors53a1to53a3are inserted into the conventional first to third-step fiber inserting holes51a1to51a3.

Specifically, a bend of the optical fiber54akat the kthstep (k is an integer of 1 or more) can be expressed by a curvature radius r of the optical fiber54ak. Then, the curvature radius r of the optical fibers54akcan be expressed by using as parameters a distance Dk′ between an exposed fiber side end53bkof a kth-step optical fiber tape conductor53akand guide grooves52of a corresponding fiber inserting holes51ak, and a misalignment Gk′ between the vertical position of the axis of the fiber inserting holes51akand the vertical center of the multi-core optical fiber tape conductor53ak.

Next, a method for obtaining an approximate curvature radius of a bend will be described below.

As shown inFIG. 1-7, the trace of an optical fiber of which both ends (fixed points a) are misaligned (misalignment corresponding to the above-mentioned misalignment Gk: G) is made approximate to a sine curve in which one of the fixed points is an origin point of the x-y coordinate system. In other words, the trace of the optical fiber shown inFIG. 1-7can be made approximate to a curve of cos function (y=cos x), in which one of the fixed points is an origin point, being inverted with a wavelength of 2D when the distance between the fixed points is D (corresponding to the above-mentioned distance Dk′).

That is to say,y=-cos⁡(π⁢⁢xD)EQUATION⁢⁢1⁢-⁢2

When a starting point of the equation 1-2 is matched to one fixed point, the equation 1-2 can be modified as follows:y=1-cos⁡(π⁢⁢xD)EQUATION⁢⁢1⁢-⁢3

As shown inFIG. 1-7, since the amplitude corresponds to G, the trace of the optical fiber is finally given by the following equation:y=G2⁢(1-cos⁡(π⁢⁢xD))EQUATION⁢⁢1⁢-⁢4

A curvature radius r at a point X of the trace which can be expressed by the X-Y coordinate system, is given by the following equation:r={1+(ⅆy/ⅆx)2}32ⅆ2⁢yⅆx2EQUATION⁢⁢1⁢-⁢5

The curvature radius is minimized at both ends of the curve (in other words, a bend is maximized). Then, the equation 1-4 is twice differentiated, the result is substitute into the equation 1-5, and further, x=0 is substituted to calculate the equation 1-5, from which the following equation 1-6 is derived.r=2⁢D2G⁢⁢π2EQUATION⁢⁢1⁢-⁢6

More specifically, since the bend of the optical fiber becomes larger in inverse proportion to the curvature radius r, as seen from the equation 1-6, the longer the distance D is, the larger the curvature radius r becomes, thereby reducing the bend.

On the other hand, in the conventional ferrule50, as shown inFIG. 1-6, optical fibers54a1of the first-step optical fiber tape conductor53a1are inserted into the corresponding fiber inserting holes51a1in such a way that an exposed fiber side end53b1is brought into contact with the guide grooves52of the corresponding fiber inserting holes51a1, and the second to fifth-step optical fibers54a2to54a5are inserted into the corresponding fiber inserting holes51a2to51a5in such a way that the positions of the exposed fiber side ends53b2to53b5along the axial direction of the fiber inserting holes are identical to the position of the exposed fiber side end53b1along the axial direction of the fiber inserting holes.

For this reason, a distance Dk′ between an exposed fiber side end53bkof the kth-step optical fiber tape conductor53ak(k is at least 2, i.e., k≧2) and guide grooves of fiber inserting holes51akcan be expressed as in the equation 1-7, where L denotes a length of each of the guide grooves52at the kthstep along the axial direction of the fiber inserting holes.
Dk′=L×(k−1)  EQUATION 1-7

More specifically, the distance Dk′ is extremely shorter since the distance depends on the length L of the guide groove52at the kthstep along the axial direction of the fiber inserting holes, which may causes a large bend (distortion).

Accordingly, in an optical connector C which is assembled by inserting optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5into corresponding fiber inserting holes with the use of the conventional ferrule50and fixed the optical fibers therein, the optical fibers at the second step or later are susceptible to large bends (distortions). However, in the configuration of the present embodiment, as shown inFIGS. 1-4,1-5,1-8and the like, a contact portion15is formed spaced by a predetermined distance Dk (D1to D5) from one ends E1to E5of the guide grooves10N1to10N5opposed to the fiber inserting holes along the axial direction of the fiber inserting holes3N1to3N5of the respective steps. For this reason, when the optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5are inserted into the respective fiber inserting holes3N1to3N5, the exposed fiber side ends (end faces)2d1to2d5of tape members2c1to2c5of the optical fiber tape conductors2a1to2a5are fixed in contact with the contact portion15.

Or, in the configuration of the present embodiment, the distance Dk between the exposed fiber side end2dkof the kth-step optical fiber tape conductors2akand ends Ek of the guide grooves10Nk of the corresponding fiber inserting holes3Nk can be expressed by an arrangement position of the contact portion15along the axial direction of the fiber inserting holes, in other words, a distance Dk (D1to D5) from the contact portion15to the ends Ek of the guide grooves10Nk along the axial direction of the fiber inserting holes3Nk.

Accordingly, by lengthening enough the distance Dk between the exposed fiber side end2dkof the optical fiber tape conductor2akof the kthstep and the ends Ek of the guide grooves10Nk along the axial direction of the fiber inserting holes3Nk, corresponding to the distance of the contact portion15, to enlarge the curvature radii r of the optical fibers2b1to2b5of the respective steps, it is possible to minimize bends (distortions) created in the optical fibers2b1to2b5.

In general, bends created in the optical fibers2b1to2b5are known such as have little effects on the optical characteristics and intensity of the optical fibers when the curvature radius r is equal to or more than 30 mm.

Therefore, in the present embodiment, the distance Dk between the exposed fiber side end2dkof the optical fiber tape conductor2akof the kthstep and the ends Ek of the guide grooves10Nk of the fiber inserting holes3Nk is determined so as to have curvature radius r of at least 30 mm.

For instance, in the present embodiment, a misalignment Gk of kth-step optical fibers (1≦k≦5) is expressed by the equation 1-1 {Gk=0.05(k−1)+α} using a difference 0.05 between a vertical fiber pitch and a thickness of a tape member. When a length L of each guide groove of10N1to10N5along the axial direction of the fiber inserting holes is 0.3 mm (L=0.3 mm), the above-mentioned equation (1-6) is used to determine a distance Dk which satisfies r≧30 mm, of which results are shown in Table 1-1.

In the ferrule1of the present embodiment, if a distance from a contact side face5ato the end E5of a fifth-step guide groove10N5along the axial direction of the fiber inserting holes is 2.0 mm, a distance from the contact side face5ato the end E4of a fourth-step guide groove10N4along the axial direction of the fiber inserting holes is 2.3 mm, a distance from the contact side face5ato the end E3of a third-step guide groove10N3along the axial direction of the fiber inserting holes is 2.6 mm, a distance from the contact side face5ato the end E2of a second-step guide groove10N2along the axial direction of the fiber inserting holes is 2.9 mm, and a distance from the contact side face5ato the end E1of a first-step guide groove10N1along the axial direction of the fiber inserting holes is 3.2 mm.

Accordingly, distances Ds1to Ds5between the ferrule side face5aof the first to fifth steps and the exposed fiber side ends2d1to2d5of the optical fiber tape conductors2a1to2a5of the first to fifth steps and the other end Ek of the guide groove10Nk of the fiber inserting hole3Nk are determined as shown in the following table 1-2.

In other words, when the distances Ds1to Ds5from the ferrule side face5ato the exposed fiber side ends2d1to2d5of the first to fifth step fiber tape conductors2a1to2a5are set as shown in the table 1-2 (Ds1=3.20 mm to Ds5=7.44 mm), respectively, it is possible to have the curvature radii of the bends of the optical fibers2b1to2b5more than 30 mm.

However, it is difficult to set the distances Ds1to Ds5from the ferrule side face5ato the exposed fiber side ends2d1to2d5of the first to fifth-step fiber tape conductors2a1to2a5at different values in steps.

Then, in the present embodiment, the longest distance Ds5(of the fifth step) among the distances Ds1to Ds5from the ferrule side face5ato the exposed fiber side ends2d1to2d5of the first to fifth-step fiber tape conductors2a1to2a5is set as a common value for the distances Ds1to Ds5from the ferrule side face5ato the exposed fiber side ends2d1to2d5of the first to fifth-step fiber tape conductors2a1to2a5.

In other words, the distance D from the contact side face5ato the contact portion15along the axial direction of the fiber insertion holes is set at Ds5=7.44 (mm).

As a result, in the present embodiment, since the exposed fiber side ends2d1to2d5in the tape members2c1to2c5of the first to fifth-step fiber tape conductors2a1to2a5are fixed in contact with the contact portion15, the exposed fiber side ends2d1to2d5can be fixed at a position such that the curvature radius r of each of the respective optical fibers2b1to2b5is at least 30 mm.

Accordingly, bends of the optical fibers2b1to2b5can be minimized so as not to affect optical characteristics and intensity of the optical fibers2b1to2b5.

Therefore, it is possible to prevent the optical characteristics and intensity from being degraded by bends of the optical fibers2b1to2b5caused by molding distortion, distortion due to change in temperature or moisture taking or the like, thereby keeping high reliability of a whole ferrule1and a whole optical connector C.

The distance (D=7.44 mm) between the contact side face5aand the contact portion15along the axial direction of the fiber inserting holes has been referred to as an example here, and it is needless to say that the present invention is not limited to this value as it is.

Further in the present embodiment, a reliable tolerance of the curvature radii of the bends created on the optical fibers2b1to2b5is set at least 30 mm and the distance D between the contact side face5aand the contact portion15along the axial direction of the fiber inserting holes is set so as to have the curvature radii r of 30 mm or larger. However, these are not for limiting the present invention.

In other words, even when the above-mentioned curvature radii r of below 30 mm is tolerated for such a reason that the reliability is sacrificed to some degree so as to miniaturize a ferrule itself, the distance D between the contact side face5aand the contact portion15along the axial direction of the fiber inserting holes has only to be determined so as to satisfy such a requirement of the curvature radius r.

Furthermore, in the present embodiment, description has been made on a 60-core ferrule having 12-core fiber inserting holes arranged at first to fifth steps and an optical connector using this 60-core ferrule. However, these are for limiting the present invention. The present invention can apply to a ferrule having multi-core fiber inserting holes arranged at plural steps and an optical connector using this ferrule.

FIG. 2-1is a schematic perspective view illustrating a configuration of an optical connector ferrule (hereinafter referred to simply as a “ferrule”)1for assembling an optical connector C according to an embodiment of the present invention and a configuration of a plurality of optical fiber tapes (five optical fiber tape conductors2a1to2a5in this embodiment) which are inserted into the ferrule to be fixedly supported.

Further,FIG. 2-2is a vertical sectional view of the ferrule1shown inFIG. 2-1taken along the line passing through the centers of vertically aligned fiber inserting holes3or the line II—II.

As shown inFIGS. 2-1and2-2, the ferrule1has the shape of a square and is integrally formed by molding with a material of plastic resin, for example.

Hereinafter in this embodiment, plural fiber inserting holes3are also indicated by3N1for first-step fiber inserting holes and in the same way,3N2to3N5for second to fifth-step fiber inserting holes.

The ferrule1has a first side face5including openings of a plurality of fiber inserting holes3arranged at plural steps, this first side face being a contact side face to another optical device such as an optical connector, optical module or the like. The ferrule1has a second side face6(upper surface shown inFIG. 2-1) provided in contact with an upper edge end of the first side face5and extending along the axial direction of the fiber holes, the second side face having a window7for injecting an optical fiber fixing member (for example, an adhesive agent) into the ferrule while optical fibers of each fiber tape2are inserted into corresponding fiber inserting holes3.

Further, the ferrule1has a slot8formed at a face opposed to the first side face5for receiving the optical fiber tape2and a flange portion9formed at the outer edge of the slot8.

The optical fiber tape conductors2a1to2a5, as shown inFIG. 2-1, each includes a plurality of (12-core) optical fibers corresponding to the plural (12-core) fiber inserting holes and a corresponding tape member (2c1to2c5) for covering the optical fibers. The tape members2c1to2c5which are located at one end of the optical fiber tape conductors2a1to2a5are peeled off to expose the optical fibers2b1to2b5(bare fibers).

Each of the fiber inserting holes3N1to3N5has a hole diameter approximately identical to the diameter of each of the optical fibers2b1to2b5so as to insert the optical fibers2b1to2b5into the corresponding fiber inserting holes3N1to3N5.

The first to fifth-step optical fibers2b1to2b5of the optical fiber tapes conductors2a1to2a5are inserted into the first to fifth-step fiber inserting holes3N1to3N5of the thus composed ferrule1through the slot8and a receiving potion11. In inserting, the optical fibers2b1to2b5are supported by the aforementioned fiber inserting holes3N1to3N5.

While the optical fibers2b1to2b5are supported by the aforementioned fiber inserting holes3N1to3N5, an adhesive agent is injected into the ferrule via the window7to fix the optical fibers2b1to2b5, thereby completing an optical connector C.

FIG. 2-3is a vertical sectional view of the ferrule1and optical fiber tape conductors2a1to2a5, in assembling the aforementioned optical connector C, of which first to fifth-step optical fibers2b1to2b5of the optical fiber tapes conductors2a1to2a5are inserted into the first to fifth-step fiber inserting holes3N1to3N5of the ferrule1, said view being taken along the line passing through the centers of vertically aligned fiber inserting holes3or the line II—II.

Also in the present embodiment, as shown inFIG. 2-3, the thickness w1of each of the tape member2c1to2c5is in the order of 0.3 mm, for example, which is larger than 0.25 mm, space w2between two vertically aligned fiber inserting holes3. For this reason, when optical fibers2b1to2b5of the optical fiber tape conductors2a1to2a5are inserted into the respective fiber inserting holes3N1to3N5in such a manner that the vertical misalignment between the central axis of a first-step fiber inserting hole3N1and the center of the exposed fiber side end of the tape member2c1corresponding to an optical fibers2b1inserted in the fiber inserting holes3N1becomes 0, there might occur bends in the optical fibers2b2to2b5inserted into the second to fifth step fiber inserting holes3N2to3N5, as shown inFIG. 2-3.

However, in the present embodiment, an approximate curvature radius r of each of bends of the optical fibers2b2to2b5inserted in the respective fiber inserting holes3N2to3N5is obtained, and each of the lengths L1to L5of the guide grooves10N1to10N5along the axis of the fiber inserting holes is determined in such a way that the curvature radius r of the bend becomes 30 mm or larger.

Now, a determining method of the lengths L1to L5of the guide grooves10N1to10N5along the axis of the fiber inserting holes will be described below.

The curvature radii r of the bends of optical fibers are obtained by using an approximate equation of the curvature radius r derived from the above-mentioned equations 1-2 to 1-6.

For example, as shown inFIG. 2-4, the curvature radius r5of bends in the optical fibers2b5inserted into the fifth-step fiber inserting holes3N5corresponds to the above-mentioned curvature radius. Further, the distance D5between the fiber inserting side ends of the fifth-step fiber inserting holes3N5and exposed fiber side end face of the tape members2c5of the corresponding optical fibers2b5corresponds to the aforementioned distance D. Furthermore, the vertical misaligmnent G5between the central axis of a fifth-step fiber inserting hole3N5and the center of the exposed fiber side end face of the tape member2c5of the corresponding optical fiber2b5corresponds to the aforementioned misalignment G.

Accordingly, the curvature radius r5of bends in the optical fibers2b5inserted into the fifth-step fiber inserting holes3N5can be expressed with the obtained distance D5, the misalignment G5and the equation 2-5.

Likewise, distances between the optical fiber inserting side end faces of the first to fourth-step fiber inserting holes3N1to3N4and exposed fiber side ends of the tape members2c1to2c4of the corresponding optical fibers2b1to2b4can be indicated by D1to D4. And, the misalignments between the central axes of first to fourth-step fiber inserting holes3N1to3N4and the centers of the exposed fiber side end faces of the tape members2c1to2c5of the corresponding optical fibers2b1to2b4can be given by G1to G4. Accordingly, the curvature radii r1to r4of bends which occurred in the optical fibers2b1to2b4inserted into the first to fourth-step fiber inserting holes3N1to3N4can be expressed with the obtained distances D1to D4, the misalignments G1to G4and the equation 1-6.

InFIG. 2-3, the vertical misalignment between the central axes of first-step fiber inserting holes3N1and the center of the exposed fiber side end face of the tape member2c1corresponding to optical fibers2b1inserted in the fiber inserting hole3N1sis 0. Therefore, the misalignment Gk of the fibers at the step k (2≦k≦5) from the bottom step can be expressed by a difference d between a vertical fiber pitch and the thickness of a tape member. For example, in the present embodiment, since the vertical fiber pitch is 0.25 mm and the thickness of the tape member is 0.30 mm, the above-mentioned difference is given as d=0.05, and the misalignment Gk can be expressed by the following equation 2-6.
Gk=d(k−1)=0.05(k−1)  EQUATION 2-6

Next, other conditions of the curvature radius r of a bend will be described below.

In general, the whole length of a ferrule is 8 mm. And, in order to assure tolerance against the bends of the whole optical connector after completion of inserting of the fiber tape conductors2a1to2a5, the tape members2c1to2c5have to be positioned at least in the ferrule1. Therefore, when the distance (tape-peeled end distance) between exposed fiber side end faces of the tape members2c1to2c5and the opening end of the slot8is indicated by S, S is preferably at least 0.5 mm.

Seen from the above-mentioned equation 2-6, the longer the distances D1to D5are, the larger the curvature radii r1to r5become, which are convenient for the bends. However, in view of the tolerance against the bends of the whole optical connector, there are upper limits of the distances D1to D5based on the distances S.

In addition, in order to suppress degradation of optical characteristics due to shrinking of a molded form in molding a ferrule, shrinking and swelling of an optical connector per se caused by temperature change, moisture taking after the optical fiber tape conductors2a1to2a5are inserted therein or the like, the distance T (hereinafter referred to as a “window distance”) from the first side face5(contact side face) to the window7along the axis of the fiber inserting holes is preferably at least 0.2 mm.

The lengths L1to L5of the respective guide grooves10N1to10N5along the axis of the fiber inserting holes are required to be at least 0.3 mm in view of workability of inserting optical fibers.

The above-described requirements are summarized below:

(2) Window distance of the window7: T≧2.0 mm

(3) Peeled tape side distance of the tape members2c1to2c5in the ferrule: S≧0.5 mm;

(4) Length of the respective guide grooves: L1to L5≧0.3 mm.

Changing the following parameters (A) and (B), values of the following parameters (A) and (B) are determined so as to satisfy all the requirements.

(A) Lengths of the respective guide grooves L1to L5

(B) Step k of the first to fifth steps, of which misalignment Gk is set at 0

The ferrule1inFIG. 2-3mentioned above is configured with the parameter (B): k=1 or the first-step misalignment: G1=0. On the other hand, the ferrule1A inFIG. 2-5is configured with the parameter (B): k=2 or the second-step misalignment: G2=0.

The ferrule1B inFIG. 2-6is configured with the parameter (B): k=3 or the third-step misalignment: G3=0.

The configuration of the ferrule1A shown inFIG. 2-5is different from that of the ferrule1in the position of the slot8. Specifically, as shown inFIGS. 2-7Aand2-7B, the vertical position of the slot8aof the ferrule1A is 0.05 mm shifted down towards the first step compared with the position of the slot8of the ferrule1shown inFIG. 2-3in which the first-step misalignment is 0.

The above-mentioned 0.05 mm corresponds to a difference between the vertical fiber pitch and the thickness of a tape member. In other words, since the first-step misalignment G1is set at 0 in the ferrule1shown inFIG. 2-3, the vertical position of the slot8is also set appropriately so as to satisfy the misalignment: G1=0. Besides, there is found misalignments: Gk=d(k−1)=0.05(k−1) in the kthstep (2≦k≦5).

In order to have the second-step misalignment: G2=0 in the ferrule1A shown inFIG. 2-5, the optical fiber tape conductors2a1to2a5for the ferrule1shown inFIG. 2-3have to be shifted towards the first step side or the third step side by 0.05 mm which is the second-step misalignment: G2=0.05(2−1)=0.05 mm found in the ferrule1.

If the optical fiber tape conductors2a1to2a5are shifted to the third step side, the third or later-step misalignments will be further increased, which is considered not appropriate. Accordingly, the vertical direction of the slot8ain the ferrule1A shown inFIG. 2-5is 0.05 mm shifted to the first step as compared to the vertical position of the slot8in the ferrule1shown inFIG. 2-3.

Likewise, the vertical position of the slot8bin the ferrule1B shown inFIG. 2-6is shifted to the first step by 0.10 mm (corresponding to the third-step misalignment G3), compared to the vertical position of the slot8in the ferrule1shown inFIG. 2-3.

Here, in the configuration of the ferrule1shown inFIG. 2-3(the first-step misalignment: G1=0), misalignments G0to G5, distances D1to D5, window distance T, peeled tape side distance S, distances (bend starting distances) U from the first side face5to the bend starting positions of the optical fibers2b1to2b5and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at least 0.8 mm are shown in the table 2-1.

In addition, in the configuration of the ferrule1A shown inFIG. 2-5(the second-step misalignment: G2=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, distances (bend starting distances) U from the first side face5to the bend starting positions of the optical fibers2b1to2b5and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at least 0.8 mm are shown in the table 2-2.

Seen from the tables2-1an2-2, it is impossible to satisfy the curvature radii r1to r5≧30 mm for all the steps in both of the ferrule1and ferrule1A. Here, considering that the curvature radii: r1to r5≧30 mm can not be satisfied in the ferrule1nor ferrule1A, it is obvious that the curvature radii: r1to r5≧30 mm can not be satisfied also in the ferrule1B. Therefore, a table of the ferrule1B is omitted.

Next, in the configuration of the ferrule1shown inFIG. 2-3(the first-step misalignment: G1=0), misaligmnents G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at 0.7 mm are shown in the table 2-3.

Then, in the configuration of the ferrule1A shown inFIG. 2-5(the second-step misalignment: G2=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at 0.7 mm are shown in the table 2-4.

Seen from the table 2-3, if in the ferrule1where the first-step misalignment G1is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.7 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Further, seen from the table 2-4, in the ferrule1A where the second-step misalignment G2is 0, the curvature radii: r1to r5≧30 mm can not be satisfied for any of the steps. Furthermore, since, as shown inFIG. 2-4, the first-step curvature radius r1is much smaller than 30 mm, it is clear that the curvature radii: r1to r5≧30 mm can not be satisfied for the ferrule1B. Therefore, a table of the ferrule1B is omitted.

Next, in the configuration of the ferrule1shown inFIG. 2-3(the first-step misalignment: G1=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at 0.5 mm are shown in the table 2-5.

Further, in the configuration of the ferrule1A shown inFIG. 2-5(the second-step misalignment: G2=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at 0.5 mm are shown in the table 2-6.

Furthermore, in the configuration of the ferrule1B shown inFIG. 2-6(the third-step misalignment: G3=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at 0.5 mm are shown in the table 2-7.

Seen from the table 2-5, if in the ferrule1where the first-step misalignment G1is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.5 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Seen from the table 2-6, if also in the ferrule1A where the second-step misalignment G2is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.5 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Particularly, when the lengths L1to L5of the respective guide grooves10N1to10N5in the ferrule1A are set at 0.5 mm, the peeled tape side distance S, in other words, distances between the exposed-fiber-side end faces of the taper members2c1to2c5and the opening end of the slot8acan be set longer than the minimum value of 0.5 mm, thereby obtaining more preferable results.

In addition, when the lengths L1to L5of the respective guide grooves10N1to10N5are set shorter than 0.5 mm, it is possible, in producing a ferrule1with the use of a die, to assure enough lengths to hold molding pins for forming fiber inserting holes3thereby preferably improving molding accuracy of the fiber inserting holes3in the ferrule1.

Further, seen from the table 2-7, in the ferrule1B where the third-step misalignment G3is 0, the curvature radii: r1to r5≧30 mm can not be satisfied for all the steps.

Next, in the configuration of the ferrule1shown inFIG. 2-3(the first-step misalignment: G1=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at a minimum of 0.3 mm are shown in the table 2-8.

Further, in the configuration of the ferrule1A shown inFIG. 2-5(the second-step misalignment: G2=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at a minimum of 0.3 mm are shown in the table 2-9.

Furthermore, in the configuration of the ferrule1B shown inFIG. 2-6(the third-step misalignment: G3=0), misalignments G1to G5, distances D1to D5, window distance T, peeled tape side distance S, bend starting distances U and curvature radii r1to r5, obtained for the respective first to fifth steps when the lengths L1to L5of the parameter (A) are set at a minimum of 0.3 mm are shown in the table 2-10.

Seen from the table 2-8, if in the ferrule1where the first-step misalignment G1is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.3 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Seen from the table 2-9, if in the ferrule1A where the second-step misalignment G2is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.3 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Particularly, when the lengths L1to L5of the respective guide grooves10N1to10N5in the ferrule1A are set at 0.3 mm, the curvature radii r1to r5can be set larger than those for the other cases (accordingly, the ill effects of bends can be reduced). Further, the peeled tape side distance S, in other words, distances between the exposed-fiber-side end faces of the taper members2c1to2c5and the opening end of the slot8acan be set at a value twice longer than the minimum value of 0.5 mm, thereby obtaining more preferable results.

Seen from the table 2-10, if also in the ferrule1B where the third-step misalignment G3is 0, the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.3 mm, the curvature radii: r1to r5≧30 mm can be satisfied for all the steps and the other requirements can be also satisfied.

Further, since the first-step curvature radius r1is approximately 30 mm shown in the table 2-10, it is clear that the first-step curvature radius r1can be set smaller in a ferrule in which the fourth or later-step misalignment G4, G5is 0. Therefore, tables of ferrules of which the fourth or later-step misalignment G4, G5is 0 are omitted.

As described above, according to the present embodiment, if the lengths L1to L5of the respective guide grooves10N1to10N5of the ferrule1are set in a range of 0.3 mm to 0.7 mm (more than 0.3 mm and less than 0.7 mm), it is possible to produce a ferrule1which satisfies all the above-mentioned requirements (1) to (4).

Particularly, it is preferable that the ferrule1A, after having the optical fiber tape conductors2a1to2a5inserted therein, is configured such that the slot8ais positioned in such a manner that a misalignment between the central axes of the second-step fiber inserting holes3N2and the center of an exposed fiber side end face of the tape member2c2of the corresponding optical fibers2b2is set at 0 and the lengths L1to L5of the respective guide grooves10N1to10N5are set at 0.3 mm (refer to FIG.2-8), thereby assuring a longer peeled tape side distance from the slot to the inside of the ferrule as well as a larger curvature radius of the bends.

Here, in the above-mentioned embodiment, it has been described that bends of the optical fibers2b1to2b5become maximum at the optical fiber inserting side end portion of the fiber inserting holes3N1to3N5. However, these are for simplification of the calculations but not for limiting the present invention. For example, a ferrule1D as shown inFIG. 2-9is provided with guide holes30N1to30N5which extend coaxially in communication with the fiber inserting holes3N1to3N5, instead of the guide grooves10N1to10N5.

Each of these guide holes30N1to30N5has a diameter longer than that of each of the fiber inserting holes3N1to3N5. Therefore, in a thus configured ferrule ID, bends of the optical fibers2b1to2b5are likely to be reduced.

Also in the configuration shown inFIG. 2-9, the same effects can be obtained if the lengths of the guide holes30N1to30N5along the axes thereof are set in a range of 0.3 mm to 0.7 mm as described in the present embodiment.

Further, in the present embodiment, the guide grooves10N1to10N5are formed to be coaxially in communication with the lower edges of the fiber inserting holes3of the respective steps, or each to have a cross section of approximately semicircular shape. However, this is not for limiting the present invention.

In other words, the guide grooves10N1to10N5may have any configuration only if they are allowed to guide insertion of optical fibers into the fiber inserting holes3along the axial direction of the respective fiber inserting holes.

In the present embodiment, description has been made as to a 60-core ferrule which has 12-core fiber inserting holes aligned at each of the first to fifth steps and an optical connector which utilizes such a 60-core ferrule. However, these are not for limiting the present invention. The present invention may be applicable to any ferrule that has a plurality of fiber inserting holes arranged at plural steps and any connector which utilizes such a ferrule.

Next, an optical fiber inserting jig will now be described with reference to the drawings.

Description is made below about an example of the embodiment of an optical fiber inserting jig according to the present invention. This optical fiber inserting jig includes a base member1made of resin, which has a ferrule set stage2on which a ferrule C inFIG. 3-7can be set and a fiber set stage3on which an optical fiber tape B shown in the same figure can be set. When the optical fiber tape B of which coating if peeled off at the end to have optical fibers A exposed is set on the fiber set stage3and slid toward the ferrule set stage2, the optical fibers A are inserted into respective fiber inserting holes G (inFIG. 3-7) of the ferrule set on the ferrule set stage2.

As shown inFIG. 3-1, the above-mentioned fiber set stage3is integrally formed with a sliding member11which slides to the direction of the arrow a-b inFIG. 3-1in a stage setting space10formed by providing a recess in the upper surface of the base member1. Specifically, two parallel support axes12are allowed to pass through the sliding member11, and both ends of each of the support axes12are fixed onto opposed inner walls of the stage setting space10to support the sliding member11so that the sliding member11can slide in the direction of the arrow as well as the fiber set stage3. Further, there is provided a control pin14between the support axes12and in parallel with the support axes12, and an end of the control pin is allowed to pass through a side wall15of the stage setting space10to the outside of the base member1. Then, this protruding end is provided with a knob16on. When the knob16is pushed to the axial direction of the control pin14, the sliding member11is guided by the support axes12to slide to the direction of the arrow a, and the fiber set stage3is moved to the same direction. Meanwhile, when the knob16is pulled to the axial direction of the control pin14, the sliding member11is guided by the support axes12to slide to the direction of the arrow b, and the fiber set stage3is moved to the same direction.

As shown inFIG. 3-1, the above-mentioned fiber set stage3has a guide groove20formed running the length of the fiber set stage3, which groove20is little wider than the optical fiber tape B, and the optical fiber tape B can be set in the groove20. The sliding member11has a holding portion21which can hold the optical fiber tape B set in the guide groove20by covering the optical fiber tape B. More specifically, a fitting axis23is bridged between two protruding brackets22which are provided each at an end of the sliding member11so as to be longitudinally opposed to each other. The holding portion21is mounted on the fitting axis23so as to be turnable along the direction of the arrow c-d. Therefore, the holding portion21is turned to the direction d in the figure before the optical fiber tape B is set in the guide groove20on the fiber set stage3, and when the holding portion21is turned to the direction c the optical fiber tape B is held between the guide groove20and the holding portion21. The holding portion21is allowed to slide to the axial direction of the fitting axis23, and can hold any longitudinal position of the optical fiber tape B set in the guide groove21.

As shown inFIG. 3-1, the ferrule set stage2is formed to be a resin block which has three side walls30provided on the upper surface in such a manner that the ferrule C can be fit (set) in the side walls30. The front one of the side walls30has a gap31formed so as to prevent interference with the optical fiber protruding from the contact side face H of the ferrule shown inFIG. 3-8B. And, the other side walls30has gaps32formed so as to prevent interference with the collar S of the ferrule C.

As shown inFIG. 3-1, the ferrule set stage2is provided at a longitudinal end of the base member1so as to be turnable along the arrow e-f in the figure. Specifically, a fixing pin (not shown) is allowed to pass through the back end of the ferrule set stage2in parallel with the alignment direction of the fiber alignment grooves F (inFIG. 3-7) of the ferrule C set in the stage2, and both ends of the fixing pin are fixed to the base member1in such a manner that the stage2is turnable around the fixing pin in the direction of the arrow e-f.

As shown inFIG. 3-1, a fiber alignment portion40is provided at the backside of the above-mentioned ferrule set stage2(the fiber set stage3side). This fiber alignment portion40has a plurality of dividing plates41spaced, in which at least 2 fiber inserting grooves42are formed at a given pitch so that the optical fibers A are aligned by being inserted into the inserting grooves42which is shown inFIG. 3-2. The plurality of dividing plates41are spaced at a pitch larger than a diameter of each of the optical fibers A to be inserted into the fiber inserting grooves42and the pitch between the centers of the adjacent optical fiber inserting grooves42is the same as the alignment pitch of the optical fibers A. If the alignment pitch of the dividing plates41(=the width of each of the optical fiber inserting grooves42) is too large, alignment of the optical fibers A will be degradated. Therefore, the alignment pitch of the dividing plates42is preferably between or equal to 0.130 and 0.145 mm.

As shown inFIG. 3-3, each of the dividing plate41of the aforementioned fiber alignment portion40tapers down from its roots to the upper edges44of the dividing plate41. Therefore, a slot43of the optical fiber inserting groove42becomes wider to the outside, which facilitates insertion of an optical fiber A into the groove42.

As shown inFIG. 3-2, guide pin grooves50are provided one at each side of the above-mentioned fiber alignment portion40so as to receive guide pins U protruding from the side face T of the ferrule C set on the ferrule set stage2(the side face T is opposite to the contact side face H). The ferrule C can be positioned by inserting the guide pins U into the guide pin grooves50. Besides, when the guide pins U of the ferrule C are inserted in the guide pin grooves50, the side face T of the ferrule C is got in contact with the fiber alignment portion40tightly with no space formed between them. Therefore, it is not necessary to prepare an exposed optical fiber A of the optical fiber tape B longer than necessary, and it becomes easy to insert the optical fiber A into the optical fiber inserting groove42. Furthermore, inserting into the fiber inserting hole G of the ferrule C becomes facilitated. More specifically, if the guide pins50are not provided, the guide pins U protruding from the ferrule side face T are interfered with the fiber alignment portion A, which causes a space corresponding to the protrusive length of the guide pins U between the ferrule side face T and the fiber alignment portion40. Accordingly, in order to assure a given insertion length, it is required to make the exposed optical fiber A longer. However, when the exposed optical fiber A is longer, the width of the optical fibers A shown inFIG. 3-11becomes significantly increased, which makes it extremely difficult to insert them into the optical fiber inserting grooves42.

(Example of How to Use 3-1

Inserting of an optical fiber tape shown inFIG. 3-7into a ferrule shown in the same figure with the use of an optical fiber inserting jig of the present invention having the structure as above is carried out in the following manner.

(1) After the holding portion21shown inFIG. 3-1is turned in the direction of the arrow d, an optical fiber tape B is set in a guide groove20on the fiber set stage3. This is followed by the holding portion21which is turned in the direction of the arrow c to fix the optical fiber tape on the stage3. Here, coating of an end of the optical fiber tape B is removed off in advance to make the optical fibers A exposed by a given length.

(2) A ferrule C is set downward on the ferrule set stage3shown inFIG. 3-1. Then, the guide pins U protruding from the side face T of the ferrule C are inserted into the guide pins50inFIG. 3-2to position the ferrule C, and the ferrule side face T and the fiber alignment portion40abut on each other with no space formed therebetween. Here, either of the optical fiber tape B and the ferrule C may be set first.

(3) The fiber tape B is slid to the fiber alignment portion40shown inFIG. 3-1along the guide groove20to insert the optical fibers A into the optical fiber inserting grooves42of the fiber alignment portion40. Specifically, while ends of the optical fibers A are lifted above, the optical fiber tape B is slid to the fiber alignment portion40to move the optical fibers A above the optical fiber inserting grooves42(FIG.3-3). Then, optical fibers A are inserted through the slots43of the optical fiber inserting grooves42shown inFIG. 3-3into the grooves42. Thereby, the optical fibers A are aligned at a predetermined pitch (this pitch is given by the pitch of the optical fibers A before being widened if the optical fibers A are widened by removing coatings of the optical fibers A).

(4) The optical fiber tape B is slid to the ferrule set stage2along the guide groove30and the optical fibers A are inserted from the slot E of the ferrule C into the ferrule C further onto the respective fiber alignment grooves F (FIG.3-7). At this time, the optical fibers A are aligned at the predetermined pitch by the fiber alignment portion40, which enables the optical fibers A to be put on the fiber alignment grooves F easily and for a short time.

(5) The optical fiber tape B is slid along the guide groove20further to the ferrule set stage2. Then, the optical fibers A on the fiber alignment grooves F are guided by the fiber alignment grooves F to pass through the fiber inserting holes G provided in communication with the fiber alignment grooves F.

(6) The optical fiber tape B and the ferrule C are raised upward to be removed from the respective stages2and3.

Example of How to Use 3-2

Insertion of an optical fiber tape into a multi-core ferrule which has fiber inserting holes formed at 2 or more steps.

(1) The steps (1) to (5) of the above-mentioned example of how to use 3-1 are performed to insert optical fibers to the first-step fiber inserting holes of the ferrule.

(2) The holding portion21which holds the already inserted optical fiber tape B is turned in the direction of the arrow d to release the holding.

(3) As shown inFIG. 3-5A, the optical fiber tape B is raised little up to be isolated from the guide groove20.

(4) The knob16shown inFIG. 3-1is pulled in the direction of the arrow b to move the fiber set stage3in the same direction as shown inFIG. 3-5B.

(5) After isolating the optical fiber tape B from the groove20, the knob shown inFIG. 3-1is pushed in the direction of the arrow a to replace the fiber set stage3as it was. Then, as shown inFIG. 3-5C, the previously inserted optical fiber tape B is moved downwardly under the fiber set stage3. Here, the central axis of the guide groove20of the fiber set stage3and the central axis of the ferrule set stage2are positioned to be identical to each other when the sliding member11shown inFIG. 3-1is slid in the direction of the arrow a to abut to the inside of the side wall13of the stage setting space1. In addition, since the bottom surface of the fiber set stage3is tapered, the fiber set stage3is moved in the direction of the arrow a inFIG. 3-1, the optical fiber tape B is smoothly moved along the tapered bottom surface under the stage3.

(6) The steps (1) to (5) of the above-described example of how to use 3-1 are repeated optical fibers of a new optical fiber tape into fiber inserting holes of the second step from the bottom of the ferrule.

(7) Subsequently, the steps of (1) to (5) are repeated to insert optical fibers into fiber inserting holes of each step. After that, the optical fiber tape B and the ferrule are raised up to remove them from the respective stages3and2.

For the optical fiber inserting jig shown in the above-mentioned embodiment 3-1, the ferrule C can be positioned by inserting the guide pins U which are protruding from the ferrule C set on the ferrule set stage2into the guide pin grooves50. However, as shown inFIG. 3-6A, there are provided on the ferrule set stage2two positioning portions60equally spaced by the horizontal width of the ferrule C on the ferrule set stage2and opposed to each other so that the ferrule C may be positioned by interposing the ferrule C between the positioning portions60. Here, the horizontal width of the ferrule C is formed with high accuracy and an error thereof is kept below 10 μm.

Therefore, the ferrule C even positioned with reference to its shape of the ferrule C as described above can assure an excellent accuracy.

The guide groove20on the fiber set stage2shown inFIG. 3-1may be formed to be deeper so as to receive two or more superposed optical fiber tapes as shown inFIG. 3-6B. With the thus formed guide groove20, a plurality of optical fiber tapes are inserted into multi-core ferrule by superposing another optical fiber tape B on the optical fiber tape previously inserted in the ferrule. In this case, the fiber set stage3is not required to slide.

As described above, according to an optical connector ferrule, an optical connector and an optical connector assembling method of the present invention, there is provided a contact portion formed spaced by a predetermined distance from opening ends opposed to fiber inserting ends of the fiber inserting holes along the axial direction of the fiber inserting holes, the contact portion being brought into contact with exposed fiber side ends of tape members of the optical fiber tape conductors when the optical fibers of the optical fiber tape conductors are inserted in the respective fiber inserting holes, thereby allowing the predetermined distance of the contact portion to be determined a value far from effects of bends of the optical fibers (the curvature radii are 30 mm or longer).

Therefore, the bends of the optical fibers can be reduced to be a minimum so as to have little effects on the optical characteristics and intensity of the optical fibers. As a result of this reduction, degradation of the optical characteristics and intensity due to bends of the optical fibers can be prevented thereby assuring high reliability of the whole ferrule and the whole optical connector.

In addition, according to an optical connector ferrule and an optical connector of the present invention, each of guide portions formed so as to communicate with fiber inserting ends of corresponding fiber inserting holes arranged at plural steps has a length along the axial direction of the fiber inserting holes of between or equal to 0.3 mm and 0.7 mm. Consequently, the curvature radii of bends of the optical fibers can be determined such that the bends have little effect on the optical characteristics and intensity of the optical fibers (the curvature radii are 30 mm or longer).

Accordingly, degradation of the optical characteristics and intensity caused by bends of the optical fibers due to molding distortion, deformation by change in temperature or moisture taking or the like are suppressed thereby preventing degradation of the optical characteristics and intensity of the whole ferrule and the whole optical connector

Furthermore, an optical fiber inserting jig according to the present invention includes a fiber alignment portion which has at least two optical fiber inserting groove divided by a plurality of dividing plates so as to align optical fibers by inserting the optical fibers to the respective inserting grooves. Therefore, the optical fibers can be aligned before being inserted into the ferrule, thereby assuring easy and short-time completion of insertion into the fiber inserting holes.

According to the optical fiber inserting jig of the present invention, the optical fiber inserting groove has a width between or equal to 0.130 mm and 0.145 mm. Accordingly, it is possible to obtain accurate alignment without any interference caused by inserting the optical fibers into or removing from the optical fiber inserting groove.

The optical fiber inserting jig of the present invention is provided with guide pin grooves at the both sides of the fiber alignment portion for receiving guide pins protruding from the side face of the ferrule set on the ferrule set stage. Therefore, it is not necessary to expose an optical fiber of the optical fiber tape more than necessary and there do not occur various problems caused by the optical fibers exposed longer than necessary. The problems caused by the optical fibers exposed longer than necessary are described above. Inserting of the guide pins into the guide pin grooves also enables the ferrule to be positioned. Further, when the ferrule set on the ferrule set stage is raised upward, the guide pins are removed from the guide pin grooves to reset the positioning of the ferrule, which makes it possible to replace the ferrule from the stage. Accordingly, in removing the ferrule from the stage, the ferrule needs not be moved in the inserting direction of the optical fibers, preventing the possibility of the optical fibers to be pulled out.

According to the optical fiber inserting jig of the present invention, the width of a guide pin groove is set at between or equal to 0.700 mm to 0.720 mm. This assures enough positioning accuracy without any problems caused by the guide pins inserting into or removing from the guide pin grooves.

According to the optical fiber inserting jig of the present invention, the fiber set stage can be slid in the direction perpendicular to the axial direction of the optical fiber tape set on the fiber set stage, and therefore, the optical fiber tape already inserted into the ferrule can be removed under the stage before another optical fiber tape is set on the fiber set stage. Accordingly, when a plurality of optical fiber tapes are inserted into the ferrule, a previously inserted optical fiber tape can be kept out of the way so as to smooth operation of another optical fiber tape next to be inserted, thereby improving workability.

According to the optical fiber inserting jig of the present invention, a ferrule set stage is turnable around the alignment direction of the fiber inserting holes of the ferrule set on the ferrule set stage. Therefore, it is easy to align optical fibers with a fiber alignment portion or fiber alignment grooves of the ferrule.