Optical jack

Abstract: To realize an optical jack (501), whereby it is easy to clean the ferrule (503) and the alignment sleeve (504) and further easy to replace the alignment sleeve (504) with a new one, the optical jack (501) comprising (a) a jack body (502), (b) a rear or first housing (521) fitted to said connector housing; (c) a front or second housing (522) removably engaged with said rear housing (521); (d) an alignment sleeve (504) fixedly fitted into said front housing (522); (e) a ferrule (503) connected to an end of an optical fiber and fitted into said alignment sleeve (504) so that a front end thereof extends frontward from the engagement position.

Description: The present invention relates to an optical connector jack used for a plug-jack optical connector for removably connecting an optical fiber. Prior to the description of the optical connector, a reference will be made to a prior-art optical connector with reference to the attached drawing. The prior-art optical connector is classified into a plug-adapter-plug (PAP) optical connector and a plug-jack (PJ) optical connector. The PAP optical connector is composed of two optical connector plugs for supporting two ferrules, respectively to each of which an optical fiber end is connected, and an optical adapter engaged with these plugs so as to support two alignment sleeves to each of which the ferrule is inserted. Further, the PJ optical connector is composed of an optical connector plug for supporting the ferrule to which an end of the optical fiber is connected, and an optical connector jack engaged with the optical connector plug and supporting the ferrule to which an optical fiber end is connected and the alignment sleeve into which the ferrule is inserted. In various optical devices, however, the P-J optical connectors are widely used. Fig. 1 shows a prior-art P-J optical connector applied to a plug-in optical connector disclosed in U.S. Patent No. 4,895,425. This optical connector includes a package connector 506 attached to a package board 508 and a back panel connector 507 attached to a back panel 509. That is, an optical connector plug 505 is attached to the back panel connector 507. The connector plug 505 supports a ferrule 503A to which an optical fiber end is connected. An optical connector jack 501 is attached to the package connector 506. The optical connector jack 501 is constructed so as to be engaged with the optical connector plug 505. Within a jack body 502 of the optical connector jack 501, an alignment sleeve 504, a ferrule 503 and a housing 521 for supporting these elements 503 and 504 are housed. The ferrule 503 is inserted into the alignment sleeve 504 and an optical fiber end is connected to the ferrule 503. Therefore, the two optical fibers are connected by locating the optical connector jack 501 and the optical connector plug 505, inserting the ferrule 503A within the optical connector plug 505 into the alignment sleeve 504 within the optical connector jack 501, opposing two ferrule end surfaces 531 coaxially, and pushing these two ferrules against each other by a spring 528. Here, since not only the ferrule 503 but also the ferrule 503A are inserted into the alignment sleeve 504, the ferrule end surface can be located roughly at the center of the alignment sleeve 504. In other words, the end surface 531 of the ferrule 503 is located inside the alignment sleeve 504, that is, deep within the optical connector jack 501. In the above-mentioned optical fiber connection by the optical connector, when dust or wear chip attached onto the inner surface of the ferrule end surface 531 and the alignment sleeve 504, the connection characteristics of the optical fibers are deteriorated due to an increase in connection loss or return loss. Therefore, it is necessary to periodically clean the ferrule end surface 531 and the alignment sleeve 504. In the prior-art optical connector jack, however, since the ferrule end surface 531 and the alignment sleeve 504 are located deep within the jack from the structural standpoint, it has been difficult to clean the ferrule end surface 531 located deep within the alignment sleeve 504 by inserting a cleaning element (e.g. a cotton swab) into a narrow alignment sleeve 504. With the development of optical communications technology, since the optical connectors are reduced in size more and more for higher arrangement density, it is indispensable to reduce the length and the diameter of the ferrules 503 and 503A and the alignment sleeve 504. In the prior-art optical connector jack, however, when the inner diameter of the alignment sleeve 504 is further reduced, it is impossible to insert a cotton swab into the sleeve 504, so that it is impossible to clean the ferrule end surface 531 and the alignment sleeve inner surface. Further, in the optical connector, whenever the connectors are connected to or disconnected from each other, wear chip is produced due to friction between the ferrule 503 or 503A and the alignment sleeve 504. In case the wear chip sticks onto the ferrule end surface 531, since the connection loss or the reflection thereof increase, the connection characteristics deteriorate. To reduce the wear chip, recently excellent abrasion resistant ceramics such as Zirconia ceramics are used as the material for the alignment sleeve. In this case, however, since the alignment sleeve made of ceramics is brittle and therefore easily broken when a torsional stress beyond a predetermined value is applied to the alignment sleeve by mistake, the alignment sleeve must be easily replaced with a new one. In the prior-art optical connector jack, however, since the alignment sleeve 504 cannot be easily removed out of the optical connector jack, in case the alignment sleeve 504 is broken, it has been difficult or impossible to remove the alignment sleeve 504 from the end surface 511 side for replacement. As described above, in the prior-art P-J optical connector, since the alignment sleeve is supported within the optical connector jack, there exist problems in that it is difficult to clean the ferrule end surface and the alignment sleeve inner surface and further difficult to replace the broken alignment sleeve with a new one. The above-mentioned problems with difficulty in ferrule cleaning and alignment sleeve replacement are serious because the optical connectors are miniaturized at higher arrangement density by reducing the diameters of the ferrule and the alignment sleeve or by making the alignment sleeve of ceramics. An optical connector jack having the features of the preamble of claim 1 is known from EP-A-0 223 608. It is the object of the present invention is to provide an improved optical connector jack providing for easy replacing and save cleaning of the ferrule and the alignment sleeve and further easy replacing the alignment sleeve with a new one. This object is achieved with an optical connector jack having the features of claim 1. In the connector jack according to the present invention, the front and rear housings can be removed easily by loosening the thread or releasing them against frictional force. Since the front housing is removed, the alignment sleeve in the front housing is easily removed from the jack for replacement with a new one. further, after removal of the front housing, since the ferrule end surface projects from the rear housing, the ferrule end surface can be cleaned easily. Fig. 1 is a cross-sectional view showing a prior art plug-jack optical connector; Figs. 2 to 7 are views for assistance in explaining the present invention; Fig. 2(a) is a cross-sectional view showing a first embodiment of the optical connector jack according to the present invention; Fig. 2(b) is a cross-sectional view showing the front housing removed from the rear housing of the optical connector jack; Fig. 2(c) is a cross-sectional view showing the rear housing of the optical connector jack according to the present invention; Fig. 3(a) is a partially broken cross-sectional view showing a second embodiment of the optical connector jack according to the present invention; Fig. 3(b) is a cross-sectional view showing the front housing; Fig. 4 is a cross-sectional view showing a modification of the front housing; Fig. 5(a) is a partially broken cross-sectional view showing the entire construction of an optical connector jack; Fig. 5(b) is a cross-sectional view showing a pair of optical connector jack and the optical connector; Fig. 6(a) is a cross-sectional view showing an optical connector jack; Fig. 6(b) is a side view showing the same optical connector jack shown in Fig. 6(a); Fig. 7 is a similar cross-sectional view showing the optical connector jack shown in Fig. 6(a) from which the front housing is removed; An embodiment of the present invention will be described hereinbelow with reference to the attached drawings. Figs. 2 (a), (b) and (c) show an embodiment of the present invention. An optical connector jack 501 includes a jack body 502 within which a rear housing 521 and a front housing 522 are separately provided. The rear housing 521 and the front housing 522 are both formed into cylindrical shape. The rear housing 521 is formed with a female threaded portion 525 on a front inner circumference thereof as engage means. The front housing 522 is formed with a male threaded portion 523 on a rear outer circumference thereof as engage means. Therefore, when the female threaded portions 525 are engaged with the male threaded portion 523, the front housing 522 and the rear housing 521 are both engaged with each other. Further, when unscrewed, the engagement between the two can be released. An alignment sleeve 504 is loosely supported within the front housing 522. To prevent removal of the alignment sleeve 504 in the rearward direction, the front housing 522 is formed with a shoulder portion 524 with a smaller inner diameter at the rear side thereof. The rear housing 521 is formed with a shoulder portion with a smaller inner diameter at the rear side thereof to support the ferrule 503 therewithin. A ferrule 503 is inserted into the front housing 522 and the alignment sleeve 504. An end of an optical fiber 530 is connected to the ferrule 503. Further, the end surface 531 of the ferrule 503 is located frontward from the engagement position between the front housing 522 and the rear housing 521. In other words a housing is engageably or disengageably divided into the front housing 522 and the rear housing 521 at a position rearward from the ferrule end portion 531. Further, a spring 528 is provided on the rear side of the ferrule 503 to push the ferrule end surface 531 against another ferrule end surface of an optical connector plug (not shown) within the alignment sleeve 504. In the optical connector jack of the present invention, the structure is such that the front housing 522 can be easily removed from the rear housing 521 by loosening the engagement between the female threaded portion 525 and the male threaded portion 523 as shown in Figs. 2(b) and (c). Further, when the female threaded portion 525 and the male threaded portion 523 are fastened each other, the rear housing 521 and the front housing 522 can be securely engaged with each other. Therefore, when the front housing 522 is removed from the rear housing 521 of the optical connector jack 501, since the alignment sleeve 504 is loosely supported within the front housing 522, it is possible to easily remove the alignment sleeve 504 from the front housing 522 for replacement with a new one. Further, when the front housing 522 is removed from the rear housing 521, since the end surface 531 of the ferrule 503 projects from the rear housing 521, it is possible to easily clean the ferrule 503 by use of a cotton swab, for instance without inserting the cotton swab into 35 the alignment sleeve 504 with a small inner diameter. A second embodiment of the present invention will be described in detail with reference to Figs. 3(a) and (b). In this embodiment, a frictional force is utilized as engage means between the rear housing 521 and the front housing 522. That is, the front housing 522 has an outer friction engage portion 526 at the rear outer circumferential surface thereof, and the rear housing 521 has an inner-friction engage portion 527 (whose inner diameter is a little smaller than that of the outer frictional engage portion 526) at the front inner circumferential surface thereof. Therefore, the two friction engage portions 526 and 527 are fitted to each other for frictional connection. The construction other than the above is the same as in the first embodiment. Therefore, when the front housing 522 is removed from the rear housing 521 against the frictional force between the two friction engagement portions 526 and 527, the alignment sleeve 504 supported within the front housing 522 can be easily replaced with a new one, and further the end surface 531 of the ferrule 503 projecting from the rear housing 521 can be easily cleaned by a cotton swab, for instance. Further, in the above first and second embodiments, the shoulder portion 524 of the front housing 522 is formed integral with the front housing 522. Without being limited thereto, however, it is also possible to provide another ring 528 within the front housing 522 in place of the shoulder portion 524, as shown in Fig. 43. In this case, the ring 528 is friction fitted into the front housing 522 by determining the outer diameter thereof to be a little larger than the inner diameter of the front housing 522. Since the ring 528 also can be removed, it is possible to more easily replace the alignment sleeve 504 with a new one. Figs. 5 (a), (b) and (c), Fig. 6 and Fig. 7 show a connector arrangement that is outside the scope of claim 1. This embodiment relates to a plug-in optical connector by which a plurality of optical fibers can be connector or disconnected simultaneously. As shown in Figs. 5 (a), (b) and (c), this plug-in optical connector is composed of a package connector 506 attached to a package board 508 and a back panel connector 507 attached to the back panel 509. A plurality of optical connector jacks 501 are attached to the package connector 506, and a plurality of optical connector plugs 505 coupled with the jacks 501 are attached to the back panel connector 507. As shown in Figs. 6(a) and 6(b), the optical connector jack 501 is composed of the jack body 502, the rear housing 521, and the front housing 522. The rear housing 521 is attached to the front portion of the jack body 502. The front housing 522 is friction fitted to the front portion of the rear housing 521 so as to be engaged with and disengaged from each other. Within the cylindrical front housing 522, the alignment sleeve 504 is supported. Within the rear housing 521, the ferrule 503 is supported. The ferrule 503 is inserted into the alignment sleeve 504. The ferrule end surface 531 is located frontward from the engagement position between the rear housing 521 and the front housing 522. A small-diameter portion 524 is formed at the rear inner circumference of the front housing 522 to prevent the alignment sleeve 504 from being removed. The spring 528 is provided within the rear housing 521 to urge the ferrule 503 frontward. Therefore, when the package connector 506 and the back panel connector 507 are connected by locating the optical connector jacks 501 and the optical connector plugs 505 as shown in Fig. 5(b),the ferrule 503A can be inserted into the alignment sleeve 504, so that the optical fibers can be coupled. Further, as shown in Fig. 7, when the front housing 522 is removed from the rear housing 521 against the frictional force, the alignment sleeve 504 supported within the front housing 522 can be easily replaced with a new one, and further the end surface 531 of the ferrule 503 projecting from the rear housing 521 can be easily cleaned by use of a cotton swab, for instance. Further, although the front and rear housings can be engaged or disengaged by means of threaded portions or friction surface portions. Without being limited thereto, it is possible to adapt other means for securely engage and easily disengage these two housings with and from each other. As described above, in the optical connector jack according to the present invention, since the housing is divided into the front and rear housings, when the front housing is removed from the rear housing, the alignment sleeve can be replaced with a new one. In this case, since the ferrule end surface projects from the rear housing, the ferrule end surface can be easily cleaned. Therefore, in case the alignment sleeve is broken, the broken alignment sleeve can be replaced; and if the optical connector jack is deteriorated in the connection loss, the connection loss can be restored by cleaning the ferrule end surface. In particular, when the diameters of the ferrule and the alignment sleeve are reduced, it is possible to facilitate maintenance of the optical connector jack. Therefore, when the characteristics of the optical connector jacks are deteriorated, it is possible to restore the jack connection characteristics by cleaning the ferrules or by replacing the alignment sleeves, without replacing the overall package board.

Claims: Optical jack connected with an optical plug in a plug-jack type optical connector, comprising: a jack body (502) having a front and a rear end; a housing (521,522) fitted within said jack body; a ferrule alignment sleeve (504) fixedly fitted into said housing from said front end of said jack body; and a ferrule (503) connected to an end of an optical fiber and fitted into said alignment sleeve from the rear end, wherein a front end of said ferrule extends frontward to a point substantially centrally located along a length of and within said alignment sleeve, characterized in that the housing is completely located within said jack body and comprises a rear housing (521) and a front housing (522) that can be inserted into and removably engaged with an inner portion of said rear housing from said front end of said jack body; the alignment sleeve (504) is completely maintained within said front housing; whereby said ferrule (503) is exposed to the inner portion of the rear housing for access when said front housing with said alignment sleeve are both removed together from said rear housing toward said front end of said jack body. The optical jack of claim 1, wherein said front and rear housing are removably engaged with each other via screw thread. The optical jack of claim 1, wherein said front and rear housing are removably engaged with each other via friction. The optical jack of claim 1, wherein said front housing is formed with a smaller diameter portion (524) forming an inner shoulder for fixedly locating said alignment sleeve therewithin.

Inventors: ANDO YASUHIRO, IWANO SHIN ICHI, KAZUNORI KANAYAMA, NAGASE RYO, SUGITA ETSUJI, ANDO, YASUHIRO, IWANO, SHIN'ICHI, KAZUNORI, KANAYAMA, NAGASE, RYO, SUGITA, ETSUJI
Applicants: NIPPON TELEGRAPH & TELEPHONE, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Application year: 1990
Main classification: G02B6
IPC codes: H01R13, G02B6