Optical fiber connector

Details Optical fiber connector Optical fiber connector

2000-01-18

2001-11-06

Healy, Brian (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Structure surrounding optical fiber-to-fiber connection

C385S035000, C385S055000, C385S033000

Reexamination Certificate

active

06312163

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a connection structure for optical fibers, specifically to an optical fiber connector that makes an optical connection between two optical fibers without using a lens member.
2. Description of the Related Art
In connecting optical fibers, the most important technical task is to achieve a low transmission loss.
FIG. 14
illustrates a first conventional optical fiber connector
50
that has implemented a structure with a low transmission loss. As illustrated, the first conventional optical fiber connector
50
includes a cylindrical enclosure
53
, and a biconvex lens
54
contained in this enclosure
53
, in which one end of a first optical fiber
51
is installed in one end of the enclosure
53
, and one end of a second optical fiber
52
is installed in the other end of the enclosure
53
. Incident light from the one end face (not illustrated) of the first optical fiber
51
transmits through the first optical fiber to exit the other end face
51
a
, and, after passing through the lens
54
, the light converges on the end face
52
a
of the optical fiber
52
.
FIG. 15
illustrates a second conventional optical fiber connector
60
, which includes a first cylindrical connecting part
65
with a flange
65
a
and a second cylindrical connecting part
66
with a flange
66
a
, and a first lens
63
contained in the first connecting part
65
and a second lens
64
contained in the second connecting part
66
.
First and second disk-shaped fixing parts
67
,
68
provided with protrusions
67
a
,
68
a
having small holes in the centers thereof are mounted onto the ends of the opposite sides to the flanges
65
a
,
66
a
of the first and second connecting parts
65
,
66
. One end of each of the first optical fiber
61
and the second optical fiber
62
are guided in the center holes of the fixing parts
67
,
68
.
First and second lenses
63
,
64
are fixed inside the first and second connecting parts
65
,
66
, respectively, so that the optical axes coincide with each other; and thereafter, the first and second connecting parts
65
,
66
are attached so that the flanges
65
a
,
66
a
are engaged with each other. The first and second fixing parts
67
,
68
are fastened to the first and second connecting parts
65
,
66
with screws, etc. The first and second optical fibers
61
,
62
are stripped of the sheathing parts from the front ends thereof, and these ends
61
a
,
62
a
each are engaged in the center holes of the fixing parts
67
,
68
.
In the optical fiber connector
60
thus configured, in order to form the focuses on the end faces of the ends
61
a
,
62
a
of the first and second optical fibers
61
,
62
, for example, a light beam emitted from the end face of the end
61
a
of the first optical fiber
61
falls on the first lens
63
, and goes out as a parallel beam from the first lens
63
, and the parallel beam falls on the second lens
64
. Then, the outgoing light from the second lens
64
falls on the end face of the end
62
a
of the second optical fiber
62
.
However, in such optical fiber connectors
50
,
60
, a high positioning accuracy in the connection of the two optical fibers is required in order to transmit a stable light beam through the optical fibers. Further, in order to enhance the efficiency of optical connection through the optical elements such as the lenses and achieve a lower transmission loss than that obtained by directly connecting the optical fibers, it is necessary to fix the lenses
54
,
63
,
64
inside the enclosures
53
,
65
,
66
, align the focal positions of the lenses
54
,
63
,
64
, and adjust the positioning. Accordingly, it takes a large amount of time for the positioning adjustment.
SUMMARY OF THE INVENTION
The present invention has been made in view of these problems, and it is an object of the invention to provide an optical fiber connector that achieves a low transmission loss and a high efficiency of optical connection without requiring a lens member.
As a first means to solve at least one of the foregoing problems, the optical fiber connector of the invention includes two optical fibers facing to each other, in which one optical fiber of the two on the light emitting side has a spherical front part. In the optical fiber connector thus configured, provided that the core diameter of the optical fiber having the spherical front part is given by E1, the numerical aperture thereof by NA1, the refractive index by n1, the radius of curvature of the spherical front part by r, the core diameter of the optical fiber on the other light receiving side by E2, the distance between the two optical fibers by L, the focal length f of the optical fiber on the light emitting side is expressed by f=r/(n1−1), and provided that the beam diameter on the end face of the optical fiber on the light receiving side is given by Es, the beam diameter Es=2·L·tan(sin
−1
·NA1) is deduced, and the connection efficiency &eegr; of the two optical fibers satisfies the following inequality :
E2/(E1+Es)<&eegr;<(E2/(Es+(L/f−1)·E1))
2
≦1.0,
in the focal length f≦L; or
E2/(E1+Es)<&eegr;<(E2/(Es+(1−L/f)·E1))
2
≦1.0,
in the focal length f>L.
As a second means, the optical fiber having the spherical face is formed with at least a second radius of curvaturers, which becomes smaller than the radius of curvature r, as the radius approaches the periphery of the core from the center thereof.


REFERENCES:
patent: 4119362 (1978-10-01), Holzman
patent: 4925267 (1990-05-01), Plummer
patent: 5185836 (1993-02-01), Baker
patent: 5661832 (1997-08-01), Yonemura

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