Back post for optical fiber connector

A back post for an optical fiber connector according to the present disclosure is made from a main material mixed with an additive material. The main material is selected from the group consisting of poly ether ether ketone (PEEK), polyimide (PI), polyether imide (PEI) and polyether sulfone (PES) and the additive material is carbon fiber or glass fiber, wherein the content of the main material in the back post is from 50% to 95% by weight.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan Patent Application Serial Number 102109154 filed Mar. 15, 2013, the full disclosure of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to a back post for an optical fiber connector; and more particularly, to a plastic back post for an optical fiber connector.

2. Description of the Related Art

Fiber optics has revolutionized communication throughout the world. With the increased used of fiber optics it has become increasingly important to be able to connect and disconnect fiber optic cables from various sources. Two fiber optic cables can be optically coupled so that they are in communication with each other by using connectors and an adapter, thereby putting each fiber optic cable in communication with the other. The connectors are placed on the end of each cable and then plugged into the adapter. The adapter has two openings each one designed to receive a connector.

Referring toFIGS. 1aand1b, a conventional LC type optical fiber connector100has a generally rectangular shape with a square cross section. The connector100includes a rectangular hollow housing110comprised of a top side-wall111, a bottom side-wall112, a right side-wall113and a left side-wall114, wherein the right side-wall113is positioned opposite to the left side-wall114and connects with the bottom side-wall112and the top side-wall111. A latch120is molded into the top side-wall111and includes a living hinge125which allows the tab126to be moved up and down in a direction perpendicular to the central axis150-150of the connector100. The latch120includes a pair of protrusions121that are positioned on opposing sides of the tab126. In addition, a ferrule140protrudes from a circular opening116on the front end of the housing110. A spring188is located within the housing110to allow the ferrule140to move back and forth through the opening116. A pair of protrusions160is positioned on the right side-wall113and left side-wall114, respectively. A rectangular opening118is formed on each of the right side-wall113and left side-wall114. A boot170extends from the rear end of the housing110.

In addition, the connector100further includes a ferrule holder130, a back post182, a crimping ring184and a shrink tube186, wherein the ferrule holder130and back post182are located inside the housing110. The ferrule140has one end mounted on the ferrule holder130. The spring188is arranged between the ferrule holder130and the back post182. The spring188pushes the ferrule holder130forward such that the front end of the ferrule holder130is brought into contact with an annular protrusion117on inner walls of the housing110. The ferrule140is pushed through the annular protrusion117and protrudes from the opening116of the housing110.

In general, the back post182is made of metal and processed by lathe or CNC lathe. Since the shape of the back post182is complex, the process cost thereof is therefore much high. The reason the back post182is made of metal is that Kevlar fiber is commonly used as a strength member in fiber optic cable. The aluminum crimping ring184is used to crimp the Kevlar fiber on the back post182to prevent the fiber optic cable from detaching from the connector100under a pull force. If the back post182is not hard enough, the crimping ring184will deform the back post182and therefore fails to crimp the Kevlar fiber. In view of the above, the conventional back post182is made with metal.

Accordingly, there exists a need to provide a solution to solve the aforesaid problems.

SUMMARY

The present disclosure provides a back post for an optical fiber connector.

In one embodiment, the back post according to the present disclosure is made from a main material mixed with an additive material. The main material is selected from the group consisting of poly ether ether ketone (PEEK), polyimide (PI), polyether imide (PEI) and polyether sulfone (PES) and the additive material is carbon fiber or glass fiber, wherein the content of the main material in the back post is from 50% to 95% by weight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present disclosure provides a material composition of a back post for an optical fiber connector. For example, the back post may be the hollow back post182of the optical fiber connector100shown inFIGS. 1aand1b. The back post of the present disclosure is made from a main material mixed with an additive material. The main material may be a thermoplastic polymer, such as poly ether ether ketone (PEEK), polyimide (PI), polyether imide (PEI) or polyether sulfone (PES), and the additive material may be carbon fiber or glass fiber, wherein the content of the main material in the back post is from 50% to 95% by weight. Preferably, the content of the main material in the back post is 70% by weight.

In order to test the performance of the back post of the present disclosure, a sample is made from PEEK material mixed with carbon fiber or glass fiber. The testing is performed according to the ASTM D638 standard test method to show the stress-strain diagram of the sample. As shown inFIG. 2, a sample210has an initial length L0and a cross-sectional area A. Under the ASTM D638 standard test method, the initial length L0is 115 mm. Pull forces F are exerted on two ends of the sample210. After pulling, the length of the sample210has changed to L. Therefore, the stress-strain relations for the sample210are defined as follows.
strain(ε)=(L−L0)/L0Formula 1
stress(σ)=F/AFormula 2

The stress-strain behaviors of the samples210are illustrated inFIG. 3. The curve A indicates that the sample210by weight has 50% PEEK material and 50% carbon fiber. The curve B indicates that the sample210by weight has 70% PEEK material and 30% carbon fiber. The curve C indicates that the sample210by weight has 80% PEEK material and 20% carbon fiber. The curve D indicates that the sample210by weight has 95% PEEK material and 5% carbon fiber.

Afterward, the samples210of the present disclosure together with fiber optic cables are used to manufacture the optical fiber connectors100to perform tensile tests. According to the IEC 61753-1 and IEC 61300-2-4 standards, the tensile tests are performed in a room-temperature environment and in subjection to 21-time thermal cycles ofFIG. 4, respectively to test how large the tensile force will cause the connectors100break down. In the tensile tests of the present disclosure, the separation of the back posts182, the detachment of the crimping rings184or the deformation of the latches120on the housings110of the connectors100are all failed.

Test One: Back Posts Made from 70% PEEK Material Mixed with 30% Carbon Fiber

Referring toFIG. 5, it illustrates the numbers of failed connectors with the back posts182in the Test one under the tensile tests with and without subjection to the 21-time thermal cycles ofFIG. 4, respectively. As shown inFIG. 5, without subjection to the 21-time thermal cycles, the connectors with 3 mm diameter fiber optic cables will be all failed when the connectors are subjected to 13.5 to 15.5 kg tensile force, and the connectors with 2 mm diameter fiber optic cables will be all failed when the connectors are subjected to 10 to 14.5 kg tensile force. In subjection to the 21-time thermal cycles, the connectors with 3 mm diameter fiber optic cables will be all failed when the connectors are subjected to 10.5 to 17.5 kg tensile force, and the connectors with 2 mm diameter fiber optic cables will be all failed when the connectors are subjected to 9 to 13 kg tensile force.

Referring toFIG. 6, it illustrates which parts detach from the failed connectors ofFIG. 5. As shown inFIG. 6, without subjection to the 21-time thermal cycles, the latches120detach from a large portion of the failed connectors with 3 mm diameter fiber optic cables and the crimping rings184detach from all of the failed connectors with 2 mm diameter fiber optic cables. In subjection to the 21-time thermal cycles the crimping rings184detach from all of the failed connectors with 2 or 3 mm diameter fiber optic cables.

Test Two: Back Posts Made from 70% PEEK Material Mixed with 30% Glass Fiber

Referring toFIG. 7, it illustrates the numbers of failed connectors with the back posts182in the Test two under the tensile tests with and without subjection to the 21-time thermal cycles ofFIG. 4, respectively. As shown inFIG. 7, without subjection to the 21-time thermal cycles, the connectors with 3 mm diameter fiber optic cables will be all failed when the connectors are subjected to 10 to 13.5 kg tensile force, and the connectors with 2 mm diameter fiber optic cables will be all failed when the connectors are subjected to 9 to 10.5 kg tensile force. In subjection to the 21-time thermal cycles, the connectors with 3 mm diameter fiber optic cables will be all failed when the connectors are subjected to 6 to 9.5 kg tensile force, and the connectors with 2 mm diameter fiber optic cables will be all failed when the connectors are subjected to 6.5 to 10 kg tensile force.

Referring toFIG. 8, it illustrates which parts detach from the failed connectors ofFIG. 7. As shown inFIG. 6, without subjection to the 21-time thermal cycles, the crimping rings184detach from a large portion of the failed connectors with 3 mm diameter fiber optic cables and the crimping rings184detach from all of the failed connectors with 2 mm diameter fiber optic cables. In subjection to the 21-time thermal cycles the crimping rings184detach from all of the failed connectors with 2 or 3 mm diameter fiber optic cables.

In view of the above test results, the back posts made from 70% PEEK material mixed with 30% carbon fiber or glass fiber are in compliance with the IEC standards and therefore may replace ones made of metal.

We change the weight percentage of the PEEK material in the back posts and perform the same tensile tests. It is verified that the back posts made from 50% to 95% PEEK material mixed with carbon fiber or glass fiber are also in compliance with the IEC standards and therefore may replace ones made of metal.

In addition, we replace the PEEK material with PI, PEI or PES materials and perform the same tensile tests. It is also verified that the back posts made from 50% to 95% PI, PEI or PES materials mixed with carbon fiber or glass fiber are in compliance with the IEC standards and therefore may replace ones made of metal.

It is found that the back posts of the present disclosure made from PEEK, PI, PEI or PES materials mixed with carbon fiber or glass fiber have glass transition temperature (Tg) of 130 to 400° C., and heat deflection temperature (HDT) of 150 to 370° C. under the ASTM D638 standard with a test stress of 1.82 MPa (18.6 kgf/cm2) and a test height of 3.2 mm.

In view of the above, the back posts of the present disclosure are hard enough and may be used together with crimping rings to crimp the Kevlar fiber. Since the back posts of the present disclosure are made mainly from thermoplastic polymer, the back posts may be formed by mold. Accordingly, the production cost of the back posts of the present disclosure is relatively low in comparison with the conventional back posts made with metal.