Housing for optical connector and optical connector

An optical connector is provided to reliably hold a ferrule assembly in a housing to enable it stable optical connection. The optical connector is able to accomplish stable connection without any concern of displacement of an optical connecting end portion of the ferrule, even if the optical connector is subjected to repeated connecting and disconnecting operations. In the optical connector, a ferrule assemble having a polygonal prism-shaped flange is accommodated and held so as to elastically reciprocate in a housing of a cavity which has a polygonal engaging portion to receive and engage the flange of the ferrule assemble. A protrusion is formed at an end part of each engaging wall in the direction of inserting the ferrule assemble to rise toward an insertion opening for the ferrule assemble, and each protruding portion of the protrusion is provided to have each different rising height thereof.

TECHNICAL FIELD

The present invention relates to a housing for an optical connector which holds a ferrule assembly to be used for transmitting and receiving optical signals, and an optical connector for equipping the ferrule assembly to the housing.

BACKGROUND

Conventionally, a ferrule which is used as a connecting end of an optical fiber for transmitting and receiving optical signals in optical communication is usually obtained by forming ceramics consisting primarily of zirconia into a predetermined shape by injection molding or the like, and then baking thereof. The ferrule is provided a through-hole for inserting an optical fiber and is used as a ferrule assembly to hold and fix the optical fiber in the through-hole. The ferrule assembly is widely used in optical connectors that are used to connect optical fibers together and to establish a communication path, or in a semiconductor laser module that is constituted by a semiconductor laser, the optical fiber and the like.

The optical connector is widely used to transmit the optical signals emitted from the semiconductor module or the like to another optical component through the optical fiber, or used as relay members connected between the optical fibers to transmit the optical signals to the optical component placed at a far distant location. The optical connector in this type is a preferred connection configuration that opposite ferrule ends each other are accurately and closely contacted therebetween and axis lines of the ferrules (specifically, axis lines of cores of the ferrules) are aligned each other to efficiently transmit light from one optical fiber to the other optical fiber. For the optical connectors, stability of assembling thereof at an on-site of connection and protection of connecting portion are required, and further, in order to minimize connection loss when the optical connectors are mutually connected, it is desirable to accurately align the cores of the optical fibers, and manufacturing error is required to be eliminated as much as possible. It is specified that the axis lines of the fiber cores must be aligned within a range of connection error of μm order when the optical fibers are connected together, so that not only a high degree of accuracy is required for shapes and dimensions of components constituting the optical connector which becomes the connection ends, but also the utmost attention must be paid to assembling the optical connector.

A communication path is established by inserting the optical connector described above into an opening of a jack socket disposed on a panel such as a wall. When the optical connector is inserted into the opening of the jack socket, a latch formed integrally with a housing of the optical connector is interlocked in the opening of the jack socket and held in order not to fall easily. In addition, there are many situations to be used the optical connectors which are oppositely connected in an adapter housing to extend the optical fiber.

An example of the optical connector having the above-described configuration is disclosed, for example, in the Japanese Patent No. 3996335 of Patent Document 1. In a conventional optical connector50shown inFIGS. 8 and 9, a housing51which has a rectangular outer shape and is cylindrically formed a main body, and a cavity52is formed in the housing. A latch53is integrally provided on the housing51, and the housing51is held by interlocking, engaging the latch in the opening of the jack socket fitted to a panel or the like. A ferrule assembly54which has a ferrule55to establish a communication path is accommodated in the cavity52. A compression coil spring56is fitted around the ferrule assembly54, and the ferrule assembly is retained in the cavity so as to be elastically advanced or retracted by an elastic resilient force of the compression coil spring56, and is resiliently connected to another opposite ferrule (not shown), and a communication path is established. In the drawings, numeral61denotes a dust cap for protecting the ferrule from dust, dirt, and stains.

As specifically shown inFIG. 9, the ferrule assembly54has the ferrule55and a holder57which holds it, and the holder57has a guide sleeve57ato guide the compression coil spring56, and a flange57bformed to a hexagonal column shape to be urged by the compression coil spring56. A truncated cone shaped guide portion57cwhich is continued to the flange57bis formed in the front portion where the ferrule is fitted.

And, the ferrule assembly54is accommodated in the housing51in a state that the guide sleeve57ais supported by an insertion58, and an optical connection end of the ferrule55is projected toward an opening51bof one end of the housing51. At this time, the holder57of the ferrule assembly54is fitted into a recess51aand a recess51dwhich have shapes which have corresponding to the holder57, and as shown inFIG. 8, an opening51cof the other end is closed by a sealing member so that the projection position of the ferrule55is established. By the sealing by the sealing member60, therefore, a front end of a trigger lever60aprojected from the sealing member60is positioned above the latch53of the housing51. By pressing the trigger lever60adownward, the latch53opposite thereto descends resistively against an elastic force, so that an interlock of the optical connector50inserted into an opening of a jack socket or the like is released and is able to be pulled out therefrom.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

A ferrule and an optical connector are precisely manufactured to achieve accurate optical connection. And as shown inFIG. 9, a recess51dwhich has a hexagonal shape which is provided so as to correspond to the shape of the flange57bis provided in the cavity52, and the ferrule assembly54is normally urged by the compression coil spring56to add an appropriate pressing force to the connection end. Therefore, the flange57bis accurately and closely engaged with the recess51dby the pressing force of the compression coil spring56, and the ferrule assembly54is mounted in the cavity52of the housing51, then an appropriate communication path to an end of the other side to be connected is established to perform high-quality signal transmission.

However, when the ferrule assembly54is accommodated in the cavity52through the manufacturing process to assemble the optical connector, there may be a case that, as shown inFIG. 10, the flange57bwhich has a hexagonal column shape is not closely engaged with the recess51dand the flange is fixed by the urging force of the compression coil spring56. Also, when the optical connector is repeatedly inserted into and pulled out from a jack socket, or repeatedly connected to and removed from an adapter for relay, there may be a case that the ferrule assembly54is fixed in the incomplete state shown inFIG. 10. When an optical connection operation is carried out by using the optical connector in which the ferrule assembly54is held in such an incomplete state, it is impossible to carry out accurate transmission of optical signals, and long working hours may be required to conduct operation without knowing the cause of the connection failure. Moreover, even though precision work is performed on components of the optical connector, actually subtle and serious eccentricity may occur in the optical connection. Therefore, after assembling the optical connector, it is adjusted that the engagement between the flange57band the recess51dis released once, and the ferrule assembly54is rotated, then the flange57band the recess51dare engaged with each other again at a position that an condition of an optimum optical connection is obtained. However, also in such case, there is a risk that the flange57bis incompletely engaged with the recess51d.

In view of the above conventional problems, the present invention provides a housing for an optical connector and an optical connector which are possessed a reliability of assemblage thereof, and are easy repeatedly to attach and remove the optical connector, and have high connection reliability as the optical connector.

Means for Solving the Problems

The subject matter of the present invention is defined by:

(1) a housing for an optical connector, comprising a cavity to accommodate and hold a ferrule assembly having a polygonal prism-shape flange and to hold the ferrule assembly to be capable of elastically advancing and retracting thereof, the housing characterized by comprising,

a polygonal engaging portion provided in the cavity to insert and engage the flange of the ferrule assembly, and

a protrusion provided at an end side of each engaging wall which forms the engaging portion in a direction of inserting the ferrule assembly therein to rise in a direction of an opening for inserting the ferrule assembly, wherein each protruding portion of the protrusion is provided to have different rising height each other;

(2) the housing for an optical connector according to the above recited item (1), wherein the each protruding portion rises in a state of a curved surface;

(3) the housing for an optical connector according to the above recited item (1), wherein the each protruding portion rises to form a curved surface having the same curvature radius;

(4) the housing for an optical connector according to the above recited item (1) or (2), wherein the height of the protruding portion which is adjacent to one another is lowered consecutively; and

(5) an optical connector characterized in that a ferrule assembly is held in a housing by fitting and engaging a flange of the ferrule assembly with the engaging portion of the housing for the optical connector according to any of the above recited items (1) to (4).

Effects of the Invention

According to the optical connector of the present invention, the ferrule assembly is rotatively moved around the axis thereof and the flange is always reliably and closely engaged with the recess which has a shape corresponding to the shape of the flange so that the ferrule assembly is smoothly accommodated in the cavity in a manufacturing process for assembling the connector, and further the ferrule assembly is held by a stable urging force of the spring, therefore, the reliability is increased at the time of assembling the connector, and there is no risk of decreasing accuracy of connection even when the connector is repeatedly fitted and removed.

DESCRIPTION OF PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment for working the present invention will be described with reference to the drawings.

FIG. 1is an exploded perspective view of an optical connector according to the present invention,FIG. 2is a vertical cross-sectional view of a housing of the optical connector according to the invention,FIG. 3is a view as shown from the direction of arrow A inFIG. 2,FIG. 4is a schematic development view explaining a shape of a recess, by spreading thereof, of the housing of the invention,FIGS. 5A and 5Bare respectively a side view and a vertical cross-sectional view of a ferrule assembly,FIG. 6is a partial vertical cross-sectional view showing a relationship between the housing and the ferrule assembly, andFIG. 7is a schematic view of a pressing test apparatus.

As shown inFIG. 1, an optical connector1of the invention is comprised of a housing2which is a main body of equipment, a ferrule assembly3accommodated in the housing2, an insertion4that guides the ferrule assembly3, and a sealing member5. The housing2and the sealing member5are made of a based material of a polyphenylsulfone (PPSU). A cavity13is formed inside the housing2(FIG. 2). On the housing2, a latch6is integrally formed with the housing as cantilevered manner to project from the housing by providing a base anchor at a connection end side thereof. A dust cap8is removably mounted to an opening7where an optical connection end of the ferrule is located.

As shown inFIGS. 5A and 5B, a main body of the ferrule assembly3is comprised of a ferrule9and a holder10that firmly holds the ferrule9. The ferrule9is formed from ceramics or zirconia by a known method such as injection molding. On the other hand, the holder10is made of stainless steel or brass. The ferrule9has a through-hole9afor inserting an optical fiber in the axis direction thereof and is held to the holder10by means of press fitting or adhesive bonding. In the invention, the ferrule9is available to use any of a single mode ferrule and a multi mode ferrule. The ferrule9is formed into a cylindrical shape, and for example, may have an external diameter D of φ1.25 mm, a length L of 6.4 mm, and an internal diameter d of φ0.125 mm.

The holder10is provided with a guide sleeve10cwhich is integrally formed on the rear end of a flange10aof a hexagonal column shape to guide a compression coil spring, and a guide portion10bof a shape of a frustum of a cone is integrally formed on the front end of the flange10a. On the flange10aof a hexagonal column shape in the holder10, the distance between wall surfaces facing each other is specified as 2.54 mm. A flexible tube11is inserted and fitted to the guide sleeve10cof the holder10, and a compression coil spring12is mounted and fitted around the outer circumference of the tube11. The ferrule assembly3is held in an elastically advanceable and retractable manner by the compression coil spring12in the cavity13. The cylindrical insertion4is inserted from the rear end of the tube11and presses an end of the compression coil spring12, and the sealing member5and the housing2are engaged with each other in the longitudinal direction, so that the ferrule assembly3is accommodated in the cavity13, the end of the insertion4is projected from an end of the sealing member5, and the optical connector is assembled in the same way as the conventional optical connector shown inFIG. 8. By this assembling, the ferrule assembly3is elastically accommodated in the cavity as shown inFIG. 6. By the engagement of the housing2and the sealing member5, a front end of a trigger lever5aof the sealing member5is positioned above the latch6of the housing2.

The cylindrical cavity13is formed in the housing2, and a recess14which has a shape corresponding to the shape of the holder10is formed between the cavity13and the opening7in which a forward end of the optically connected ferrule9is situated. Specifically, the recess14is provided with a fitting portion14b, a shape of which is corresponded to the truncated cone shape of guide portion10b, and the flange10aof the hexagonal shape, and a hexagonal shaped engaging portion14awhich are adjacent to each other. Protrusion14c(comprised of a plurality of protruding portions14c1to14c6) is formed at each side edge of a plurality of wall portions14a1to14a6of the engaging portion14ain the direction of inserting the ferrule assemble (i.e., from each side part or edge of the of the wall portions14a1to14a6toward the cavity13). It is preferred that the plurality of the protruding portions14c1to14c6is formed to rise in a shape of curved surface. The boundary portions between the protrusion14cand the wall portions of the engaging portion14a, are smoothly connected, therefore, the ferrule assembly3can be easily and reliably inserted into and held in the housing2. It is preferred that the shape of the curved surface of the each protruding portions are formed to have the same curvature radius R, and the radius R is preferred to be about 0.45 mm to 0.85 mm. As shown inFIGS. 3 and 4, each rising height L of the protruding portions14c1to14c6is preferred to be 0.24 mm to 0.51 mm to have the respectively varied and different heights thereof. As schematically shown inFIG. 4, it is preferred that rising heights L1to L6of the adjacent protruding portions are formed such that the heights are successively lowered. For example, a rising height L1of the protruding portion14c1is set to 0.45 mm, and a rising height L2of the adjacent protruding portion14c2is set to 0.42 mm, and in the same way, from L3to L6, the respective rising height thereof is successively lowered by 0.03 mm by changing a protruding amount. As a result, since the rising height L1of the highest protruding portion14c1is 0.45 mm and the rising height L6of the lowest protruding portion14c6is 0.30 mm, and the difference becomes 0.15 mm. In this way, by successive variation of the rising heights of the protruding portion adjacent to one another, the flange10aof the ferrule assembly3is smoothly guided to the protrusion14c, and the ferrule assembly3is rotated around the axis thereof and easily held in the recess14.

As shown inFIG. 6, optical connection can be achieved by inserting the holder10into the recess14so that the flange10aof the holder10is reliably engaged with the engaging portion14a. However, if an insignificant eccentricity occurs, the engagement of the flange10aand the engaging portion14ais released, and the ferrule assembly3is rotated, and the flange10aand the engaging portion14aare engaged together again in a position where an optimal optical connection can be achieved.

In the example described above, a case in which the flange10aof the holder10has a hexagonal column shape is described. However, the shape of the flange10amay be a square prism-shape or other polygonal prism-shapes. It is understood that the shape of the flange is not limited to the shape described in the embodiment since the shape of the flange may be appropriately determined.

In addition, the curvature radius and the rising height of the protrusion of the invention can be properly changed in design by those skilled in the art, and are not limited to the values described above. Although an example is described in which the rising heights of the protruding portions adjacent to one another is changed in a stepwise manner, it is possible to form the protruding portions into a continuously spiral shape as a whole, in which the height is gradually lowered, by smoothly lowering the rising heights of the protruding portions.

Example

Three optical connectors (samples 1 to 3) of the present invention which have protruding portions formed so that the rising heights are lowered from 0.45 mm to 0.30 mm to be respectively and lowered 0.03 mm in order, and three conventional optical connectors (samples 4 to 6) which do not have protrusion are prepared. Then, the ferrule9is repeatedly pressed by a pressing test apparatus shown inFIG. 7, and whether or not the ferrule9returns to a correct position is tested.

The pressing test apparatus is entirely controlled by a controller (CPU)21, and reciprocative movement is repetitively is given to the ferrule9by reciprocating a plunger20aof a cylinder apparatus20being straight to the ferrule9. When the ferrule9is pressed by the plunger20a, the ferrule assembly3is evacuated in the opening7against the force of the compression coil spring described above. This evacuation operation becomes an adjustment operation of the eccentric position described above. The reciprocal movements of the ferrule9are detected by sensors26aand26b, and the movements are captured by a video camera25and displayed on a monitor24. An output signal from the sensor26is measured by a counter23and the result is stored in a memory22. In spite of evacuation of the ferule9after the projecting movement of the plunger20a, if the ferrule9does not project to the original position by the elastic force of the compression coil spring, the sensor counts one error, i.e. 1 of the error.

The reciprocal movement of the plunger is performed 50 times for each sample by using the above-described measurement apparatus, and the number of errors was measured. The result is shown in table 1. As seen from the result in table 1, for the conventional optical connectors, the error occurs 9 times in the sample 4, 5 times in sample 5, and 7 times in the sample 6. On the other hand, for the optical connectors of the present invention, it is demonstrated that the error hardly occurs in any of the samples 1 to 3, and only one time error occurred in the sample 3. A large difference in stability when the ferrule assembly is contained into the housing is observed between the optical connector obtained by using the housing of the invention which includes protrusion in the cavity and the optical connector obtained by using a conventional housing which does not include protrusion.