Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2003-01-08
2004-08-24
Lee, Michael G. (Department: 2876)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06779928
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese application serial no. 2002-001321, filed on Jan. 8, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a method for polishing end face of ferrule with optical fiber to a spherical convex surface that is capable of physical contact (PC) connection to suppress reflection light, a method for assembling optical connector, and an optical fiber terminating kit.
2. Description of Related Art
Recently, as the demand for information communication increases, the preparation for optical fiber networks goes ahead. To build an optical fiber network, for a place where the optical fiber does not need to be detachable, a fusion connection where the optical fiber is fused to connect by a splice device or adhesion connection is performed. In contrast, a detachable optical connector is used on a portion that is presumed to allow for the exchange of the communication machine due to property division or maintenance.
The aforementioned optical connector is usually adhered on an end portion of an optical fiber with a predetermined length in the factory. As an optical connector with cable sold in the market, it is used for building the optical fiber network.
Furthermore, when laying the optical fiber cable with undetermined length, or when changing the length of the optical fiber, or when the wiring work of the optical fiber cable as the layout in the building is changed or in process, for a portion that is presumed to allow for the exchange of the communication device due to property division or maintenance, it is necessary to attach an optical connector to the end portion of the optical fiber cable and then to terminate the optical fiber cable in the field. In such a situation, a portable and simple optical connector assembling kit is required to be carried to the field.
Recently, as the demand for communication of information increases greatly, even though the optical fiber cable is terminated in the field, a high quality in optical connector connection is requested. The end face of the optical connector attached to the end portion of the optical fiber cable has to be finished in the field to a spherical convex surface centered on the end face of the core of the optical fiber so as to be capable of PC connection. Moreover, in order to achieve such a PC connection that scarcely induces the returning light due to the reflection from the connection end faces, i.e., that is improved in performance relevant to return loss, and that is able to obtain a sufficiently small connection loss even for the single mode optical fiber having a core diameter equal to or less than 10 &mgr;m, the specification of the spherical convex surface of the optical connector after the PC polishing is rigorously regulated.
Conventionally, in order to satisfy such rigorously regulated specification of the spherical convex surface of the optical connector, a polishing device specially designed for PC polishing has been used. Because such a specially designed polishing device requires a power source, it is difficult to use for assembling the optical connector in the field. In addition, a battery-type portable simple polishing device is proposed. However, not only has the battery to be frequently exchanged, but also the maintenance for the polishing device constructed by many accurate parts is almost impossible in the field. Because the polishing device has to be taken back for maintenance, it is not convenient. Furthermore, in the case that a polishing device specially designed for the PC polishing is carried to the field, even though for a comparatively small-size polishing device, the preparation of the power source and a sufficient working space are required, so that there is a problem that the space capable of polishing is limited.
Additionally, because the hardness of a ferrule made of zirconia ceramic, which is generally used for an optical connector assembled in the factory, is high, it needs too much time to finish the end face in the field from a planar face to a spherical convex surface centered on the end face of the core of the optical fiber that is capable of PC connection. Therefore, when using the ferrule made of zirconia ceramic, the end face of the ferrule is processed in advance to a preliminary spherical convex surface, a so-called pre-doom. However, the ferrule made of zirconia ceramic where a special process is performed thereon is high in cost. In addition, since the hardness of the optical fiber of quartz system, etc. is lower than the hardness of zirconia ceramic, when employing the conventional plane polishing method, the end face of the optical fiber wears earlier than the end face of the ferrule to be drawn in the ferrule. As a result, a polishing method using a specially designed polishing device with special specification is required, and therefore, there is a problem that the entire cost increases.
For safety, when electricity is forbidden, to grind manually for a long time is necessary. Furthermore, since it is possible for only a skilled worker to finish the end face of the optical fiber to a required spherical convex surface so as to be capable of PC connection within a predetermined connection loss. Thus, in any case, there is a problem that the assembling cost for the optical connector is obviously increased.
SUMMARY OF THE INVENTION
According to the foregoing description, an object of this invention is to provide a method for polishing ferrule with optical fiber, a method for assembling optical connector, and an optical fiber terminating kit, which can be possible to polish an end face of a ferrule with optical fiber to a highly accurate spherical convex surface capable of PC connection, in the field where the connection with the optical connector is required.
According to the object(s) mentioned above, the present invention provides a method for polishing end face of ferrule with optical fiber, in which an optical fiber is inserted in an inner hole of a ferrule, comprising the steps of holding the ferrule with optical fiber to a ferrule holder, the ferrule holder having a predetermined mass and substantially vertically holding the ferrule with optical fiber to be self-supported with the end face of the ferrule with optical fiber as a supporting point, the ferrule being made of a material with 0.5~2 times the wearing speed characteristic in comparison with a quartz glass, making the ferrule holder to be self-supported on a polishing table having a polishing plate which has an elastic module equivalent to 70~95 degrees of rubber hardness in a state of adhering a polishing sheet thereon, in a manner such that the end face of the ferrule with optical fiber is in contact with the polishing sheet, and manually moving the ferrule holder on the polishing table by a predetermined distance in the horizontal direction to slide the end face of the ferrule with optical fiber on the polishing sheet, thereby polishing the end face of the ferrule with optical fiber to a spherical convex surface centered on the optical fiber.
The conventional ferrule made of zirconia ceramic has only one-fifth wearing speed of quartz glass, and therefore is not suitable for the present invention. A ferrule made of a material, such as borosilicate glass, crystallized glass, plastic, ceramic and metal, etc. that has 0.5~2 times of the wearing speed characteristic as compared with the quartz glass, is suitable for use for the polishing method of the present invention. In particular, as for the reduction of working time for assembling in the field, a glass ferrule, which is transparent to the ultraviolet ray and the like with a high sensitivity to an optical curing adhesive, is preferred. In addition, as compared with the quartz glass, the ferrule composed of crystallized glass of lithia-alumina-silicate that has 0.5~1.1 times of wearing speed characteristic is suitable in view of high reliability in attachment and detachment.
The ferrule holder preferably comprises a chucking means for s
Takeuchi Hirokazu
Tanaka Azusa
Wada Masanori
J.C. Patents
Le Uyen-Chau N.
Lee Michael G.
Nippon Electric Glass Co. Ltd.
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