Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
1998-07-31
2001-08-28
Schuberg, Darren (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S070000
Reexamination Certificate
active
06280099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber wavelength filter employed for selecting an optical wavelength in an optical fiber communication or an optical measurement system, and a manufacturing method for the same.
2. Description of the Related Art
The U.S. Pat. No. 5,706,379 has disclosed an optical fiber wavelength filter that employs a multilayer dielectric film filter formed on a glass substrate;
FIG. 4
is a cross-sectional view showing the optical fiber wavelength filter.
Optical fibers
21
and
22
are inserted into ceramic ferrules
23
and
24
and bonded therein to prepare a pair of ground ferrules with optical fibers. Then, a glass substrate filter
25
composed of a glass substrate and a multilayer dielectric film formed on the surface thereof is placed between the foregoing pair of ferrules
23
and
24
with optical fibers, and the optical axes of the ceramic ferrules
23
and
24
are aligned using an aligning sleeve
26
before securing them with an adhesive agent.
This prior art has been posing a problem in that the use of the glass substrate filter
25
, in which thickness t is normally a few hundred &mgr;m (≧300 &mgr;m), causes transmitted light to be refracted by the glass substrate or mode field diffusion to take place. The optical axis of the refracted light is inevitably displaced from the central axis of the ferrules.
The mechanical central axes of the ceramic ferrules with optical fibers are aligned by the inside diameter of the aligning sleeve and the misalignment of the optical axis of the transmitted light caused by the refraction can hardly be corrected. The results of the experiments carried out by the inventor have revealed that, when thickness t of the glass substrate filter is 300 &mgr;m, the measured value of the insertion loss is approximately 7 dB mainly due to the dislocated optical axis, or when the thickness is 500 &mgr;m, the insertion loss is approximately 9 dB. This means that it is difficult to control the insertion loss in this wavelength filter. In addition, a thermosetting adhesive agent is usually used in manufacturing the optical fiber wavelength filters employing the aforesaid aligning sleeves; this type of adhesive agent typically requires at least a few tens of minutes to completely harden.
The U.S. Pat. No. 5,234,772 has disclosed a dielectric multilayer film filter and a manufacturing method for the same. The optical fiber wavelength filter employs a filter composed of a dielectric multilayer film formed on a fluorinated polyimide thin film (hereinafter referred to as “thin-film filter”). The filter produced according to this process has an extremely thin wavelength filter owing to the use of the fluorinated polyimide thin film; hence, this filter is free from the deterioration in the optical properties resulting from the use of the thick glass substrate filter mentioned above.
FIG. 5
is a top plan view of an optical fiber wavelength filter employing the conventional thin-film filter; and
FIG. 6
is a longitudinal sectional view of a wavelength filter employing the conventional thin-film filter.
Optical fibers
35
and
36
(the two optical fibers are not cut at the beginning) are secured to a substrate
30
by an adhesive agent. Then, the optical fibers are cut and a groove
31
is formed across, then a thin-film filter
32
is inserted in the groove
31
and secured therein by an adhesive agent. The U.S. patent has also disclosed an example wherein a zirconia ferrule is used in place of the substrate
30
, optical fibers being attached and bonded thereto, and the zirconia ferrule or a stainless flange is provided with a groove wherein the thin-film filter is disposed.
It is necessary to provide the substrate
30
, the substrate with optical fibers, the zirconia ferrule, or the like with the groove wherein the thin-film filter is disposed; it is not easy, however, to precisely form the groove having a width of about a few tens of &mgr;m. The variations in the machining dimension of the groove width directly affect the properties of the wavelength filter and lead to the variations in the optical properties such as insertion loss of the wavelength filter. Furthermore, the end surfaces of the optical fibers that are cut apart at the time of making the groove for holding the thin-film filter cannot be ground, so that the irregular reflection of light may take place on the connection end surfaces with consequent deterioration in optical properties.
Thus, the conventional optical fiber wavelength filters have many problems in the manufacturing process or optical properties.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made with a view toward solving the problems described above, and it is an object thereof to provide an optical fiber wavelength filter which is superior to the conventional ones described above in optical properties.
Another object of the present invention is to provide a manufacturing method for the optical fiber wavelength filter.
In order to achieve the above objects, there is provided an optical fiber wavelength filter comprising a pair of ferrules aligned each with other on a V-grooved support member, each having a distal end surface slanted at an angle predetermined with respect to the optical axis thereof, each one of which is composed of a material transparent to a light ray containing a particular wavelength component, a pair of optical fibers and the supported by said ferrules, wherein said and the distal end surfaces are grounded together with the end surfaces of said ferrules and polished at said predetermined angle, a thin dielectric multilayer film filter disposed between the polished distal end surfaces of said ferrules, and an adhesive agent put on the surfaces of said pair of ferrules and said thin dielectric multilayer film filter which is cured by irradiating said pair of ferrules and said dielectric multilayer film filter at the same time with a light ray containing said particular wavelength component while both said pair of ferrules and said dielectric multilayer film filter are kept mounted on said V-grooved support member, and is solidified thereat.
Said light ray containing said particular wavelength component is an ultraviolet ray, said adhesive agent is an ultraviolet-curing resin adhesive agent, and said pair of ferrules are glass ferrules which are kept mounted on said V-grooved support member while said adhesive agent is being cured.
Said thin multilayer film filter has a thickness of approximately 10 to 40 &mgr;m including the substrate for forming said dielectric multilayer film, and the exterior of said multilayer film filter lies within the joint surface of said ferrules when it is bonded.
The distal ends of said ferrules are slant ground surfaces of 6 degrees or more.
There is also provided a manufacturing method for an optical fiber wavelength filter, comprising the steps of preparing a pair of ferrules aligned with each other on a V-grooved support member, each having a distal end surface slanted at an angle predetermined with respect to the optical axis thereof, each of which is composed of a material transparent to a light ray containing a particular wavelength component, bonding and securing optical fibers to said ferrules and grinding and polishing the distal end surfaces thereof at said predetermined angle, providing a thin multilayer film filter and an adhesive agent to be cured and hardened by a light ray containing said particular wavelength component, between the distal end surfaces of said ferrules, and performing optical axis alignment for said pair of ferrules on an optical axis aligning support member which supports said ferrules and permits the adjustment of relative positions among said pair of ferrules and said thin multilayer film filter, and irradiating said adhesive agent between the distal and surfaces of said pair of ferrules with a light ray containing said particular wavelength component from outside upon completion of said optical axis alignment until said pair of
Kelemen Gabor J.
Schuberg Darren
Seikoh Giken Co. Ltd.
Venable
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