Optical waveguides – Accessories
Reexamination Certificate
2002-05-20
2004-03-02
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Accessories
C385S147000
Reexamination Certificate
active
06701055
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a method for cutting a plastic optical fiber adapted for optical communication, which fiber has on its outer periphery a coating including a cladding layer.
Cutting of ends of plastic optical fibers for optical communication in order to mount the plastic optical fibers to optical signal connector plugs has been performed, for example, by pressing a sharp cutter to a plastic optical fiber, thereby shearing it with the pressing force (see Japanese Utility Model Registration No. 2573619). Such forcible cutting, however, causes an inconvenience that chips and/or cracks may occur in a cut plane of the plastic optical fiber, to degrade an accuracy of work in the subsequent step of forming an end face of the plastic optical fiber. To cope with such an inconvenience, an improved method has been disclosed, for example, in Japanese Patent Laid-open No. Hei 7-294748, wherein a plastic optical fiber is cut in a state that temperatures of both a cutter and the plastic optical fiber are raised by heating, thereby preventing occurrence of chips and/or cracks in a cut plane of the plastic optical fiber. Such a method, however, presents another problem that the raised temperature may give rise to deformation of a portion, other than an end face, of the plastic optical fiber, degradation of optical characteristics of the interior of the plastic optical fiber, and the like.
In most of plastic optical fibers (POFs), thermoplastic polymethyl methacrylate (PMMA) is used as a material of a core of the POF, and a fluorine based resin is used as a material of a cladding layer formed on an outer peripheral portion of the core. In addition, at present, a plurality of kinds of plastic optical fibers, each of which is of a multi-mode type, are being commercially available.
In the case of connecting a plastic optical cable led from one equipment to another equipment by mounting a POF of the cable to a connector plug and inserting the connector plug in a receptacle provided on another equipment, it is required that no change in optical transmission characteristics may occur even if the cable be replaced with a new cable.
FIG. 1A
is a typical sectional view showing a connector plug inserted in a receptacle. As shown in this figure, an end portion, inserted in a center hole of a connector plug
11
, of a POF
1
is formed in a spherical plane R having a specific radius, and a distance “a” between the end portion of the POF
1
and a light receiving element
11
c
in equipment is set to a specific length.
The structure shown in
FIG. 1A
is designed such that a positional relationship between the receptacle
11
b
and the connector plug
11
can be kept constant even if the connector plug
11
is replaced with a new connector plug. As a result, the replacement of the connector plug
11
with a new connector plug does not exert any effect on transmission characteristics of the POF
1
insofar as a position of the spherical plane R of the end of the POF
1
to the connector plug
11
is kept constant.
The formation of an end face of the POF
1
as shown in
FIG. 1B
is performed by making use of thermoplasticity of the POF
1
. More specifically, a forming die
11
d
having at its one end a concave plane of a specific radius is heated and is pressed to an end face of the POF
1
mounted to the connector plug
11
. The end face of the POF
1
is softened by heat of the forming die
11
d,
with a result that the concave plane of the forming die
11
d
is transferred to the end face of the POF
1
as a convex plane R.
A volume of the softened resin is regarded not to be changed after the forming work. Accordingly, to keep constant the distance “a” shown in
FIG. 1A
, the POF
1
must be mounted to the connector plug
11
such that a position of the end face to the connector plug
11
before formation of the convex plane R of the POF
1
is kept constant. For this reason, there has been adopted a method of mounting the POF
1
to the connector plug
11
with a sufficient excess portion projecting from the connector plug
11
, and cutting the POF
1
at a specific position associated with the connector plug
11
, thereby keeping constant the position of the convex plane R formed in the subsequent step.
Cutting of POFs has been often performed by using sharp cutting tools such as a commercially available cutter or razor. In this case, however, as shown in
FIG. 1C
, chips of a resin forming the POF main body and/or cracks may occur in a cut plane perpendicular to the axial line of the POF. Such chips and/or cracks may remain in an end face to be formed in the subsequent step as shown in
FIG. 1B
, to cause failures that change transmission characteristics, such as deficiency of a convex plane or cracking.
If a POF is cut with a previously heated cutter, as shown in
FIG. 1D
, a cladding layer and the like may extend longer in the form of whiskers, and such whiskers may adhere on a cut plane, to be rolled in a convex plane at the time of forming an end face of the POF, to degrade transmission characteristics of the POF.
By the way, a method of cutting a plastic material by using a cutter blade mounted to an ultrasonic vibration exciter has been known, for example, from Japanese Patent Laid-open No. Sho 58-175630, wherein the plastic material is cut by concentrating ultrasonic vibration at a portion to be cut of the plastic material via the cutter blade and imparting a force to the cutter blade being in contact with the plastic material.
To realize cutting of a POF with desirable optical transmission characteristics thereof kept, an attempt has been made to cut POFs by making use of such a high-frequency mechanical vibration cutting method or ultrasonic vibration cutting method. Even in the case of adopting this method, however, there may occur an inconvenience. Since a cladding layer and the like are provided on an outer peripheral surface of a core of a POF, when a cutter blade and the optical fiber are excessively heated (such heating occurs even by using a high-frequency mechanical vibration exciter), the cladding layer and the like may often extend longer in the form of whiskers and such whiskers may adhere on a cut plane, to be entrained in an end face of the POF at the time of forming the end face, thereby degrading transmission characteristics of the POF. Further, according to the related art high-frequency mechanical vibration cutting method, it is difficult to optimize working conditions required for obtaining a uniform finish cut plane, for example, a condition of determining the length of a cutoff piece of a POF.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an apparatus for cutting a plastic optical fiber, which are capable of reducing a load applied the plastic optical fiber upon cutting, thereby reducing degradation of transmission characteristics of the plastic optical fiber after cutting.
To achieve the above object, according to a first aspect of the present invention, there is provided a cutting apparatus for cutting a plastic optical fiber, including cutting means for cutting a plastic optical fiber, and positioning means for positioning the cutting means to at least a first position at which the plastic optical fiber is to be subjected to rough cutting, and to at least a second position at which the plastic optical fiber is to be subjected to finish cutting.
The cutting apparatus preferably includes vibration means for giving high-frequency mechanical vibration to a portion, being in contact with the plastic optical fiber, of the cutting means, and allowing the cutting means to heat and cut the contact portion of the plastic optical fiber.
To achieve the above object, according to a second aspect of the present invention, there is provided a cutting method of cutting a plastic optical fiber by using cutting means, including the steps of positioning the cutting means to a first position at which the plastic optical fiber is to be subjected to rough cutting, cutting the plastic opt
Maioli Jay H.
Palmer Phan T. H.
Sony Corporation
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