Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1997-07-24
2002-06-18
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S047000
Reexamination Certificate
active
06406196
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical device connected to an optical fiber transmission line, capable of receiving or transmitting/receiving a light signal, and a method for producing the same.
BACKGROUND ART
Wavelength division multiplexing (WDM) enables a transmission capacity of an optical transmission system to be increased. It also realizes bidirectional transmission and simultaneous transmission of different kinds of signals. Thus, the WDM is capable of flexibly meeting service requirements in an optical transmission system, and is applicable to various optical transmission systems such as a relay-transmission system, a subscriber system, and a local area transmission system.
In recent years, in particular, optical subscriber systems which transmit multi-channel video information and data from a central station to households through optical fibers have been proposed and studied. These systems require a plurality of photodetectors for simultaneously receiving different kinds of light signals which are multiplexed in wavelength at subscribers' household terminals and light-emitting devices for sending requests and data from households to the central station. For example, a device used for this purpose is disclosed in a reference (I. Ikushima et al., “High-performance compact optical WDM transceiver module for passive double star subscriber systems”, Journal of Lightwave Technology, vol. 13, No. Mar. 3, 1995).
FIG. 30
shows a conventional example of a light-receiving optical device which is applicable to bidirectional signal transmission. This device is disclosed in Japanese Laid-Open Patent Publication No. 6-331837.
As shown in
FIG. 30
, in this device, a first optical fiber
2012
and a second optical fiber
2014
are coupled in series with a gap (about several &mgr;m) therebetween. One end of the first optical fiber
2012
is cut obliquely with respect to an optical axis and provided with a semi-transparent and semi-reflective surface
2011
which reflects a part of a light signal and passes the remaining part. Similarly, one end of the second optical fiber
2014
is cut obliquely with respect to an optical axis and provided with a semi-transparent and semi-reflective surface
2013
which reflects a part of a light signal and passes the remaining part.
The first and second optical fibers
2012
and
2014
are arranged in such a manner that the semi-transparent and semi-reflective surface
2013
of the second optical fiber faces the semi-transparent and semi-reflective surface
2011
of the first optical fiber
2012
and the respective optical axes are linearly aligned.
A light signal propagating from the right side of the drawing is reflected by the semi-transparent and semi-reflective surface
2011
of the first optical fiber
2012
and output from the optical fiber
2012
. A first photodiode
2015
is placed along a path of the light signal and receives the light signal to generate an electric signal.
A light signal propagating from the left side of the drawing is reflected by the semi-transparent and semi-reflective surface
2013
of the second optical fiber
2014
and output from the optical fiber
2014
. A second photodiode
2016
is placed along a path of the light signal and receives the light signal to generate an electric signal.
In the conventional optical device, a semi-transparent and semi-reflective surface is directly formed on the diagonally-cut facet of each optical fiber. Because of this, (1) a special cutting is required to be conducted with respect to the facet of an optical fiber so as to make it smooth or grinding the facet of an optical fiber after diagonally cutting it is required. Furthermore, (2) in order to form a semi-transparent and semi-reflective surface on the facet of an optical fiber, it is required to form a thin film on the facet of the optical fiber. The step of inserting an optical fiber into a thin film deposition apparatus such as a vacuum deposition apparatus and depositing a thin film on the facet of the optical fiber decreases production through-put.
In addition, the ends of two different optical fibers are separately cut diagonally with respect to optical axes, and then, arranged in such a manner that the respective optical axes are aligned. Therefore, (3) it is required to adjust the optical axes with high precision; and (4) the light propagation loss between two optical fibers is likely to increase due to the shift of the optical axes and the transmission loss is varied depending upon devices. Furthermore, (5) there is a difference in refractive index between the optical fibers and the air under the condition that the optical axes of two optical fibers are aligned, even with an optical fiber gap of about several &mgr;m. Therefore, signal light is refracted in the gap, and the transmission loss is likely to greatly increase.
The present invention has been achieved in view of the above-mentioned problems, and its objective is to provide a compact, integrated, and light-weight optical device with improved productivity at low cost.
Another objective of the present invention is to provide a bidirectional optical device connected to an optical fiber transmission line, receiving and transmitting a light signal, and a method for producing the same.
DISCLOSURE OF THE INVENTION
An optical device of the present invention includes: a substrate; at least one first groove formed on the substrate; an optical fiber provided in the first groove; and at least one second groove diagonally traversing the optical fiber. The device further includes an optical member which is inserted in the second groove and has a surface reflecting or diffracting at least a part of light propagating through the optical fiber.
In a preferred embodiment, a material having a refractive index n
r
which is almost equal to a refractive index n
f
of a core portion of the optical fiber is embedded at least between the optical member and the optical fiber in the second groove.
In a preferred embodiment, there is a relationship: 0.9≦(n
r
f
)≦1.1 between the refractive index n
r
and the refractive index n
f
.
In a preferred embodiment, the material having the refractive index n
r
is made of resin.
In a preferred embodiment, the material having the refractive index n
r
is made of UV-curable resin.
In an embodiment, minute unevenness is present on an inner wall of the second groove.
In an embodiment, the optical member selectively reflects light having a wavelength in a selected range.
In an embodiment, the optical member selectively passes light having a wavelength in a selected range.
In a preferred embodiment, the optical member includes a base made of a material having a refractive index n
b
and a dielectric multi-layer film formed on the base, and there is a relationship: 0.9≦(n
b
f
)≦1.1 between the refractive index n
b
and the refractive index n
f
.
In an embodiment, the surface of the optical member has a diffraction grating.
In an embodiment, the substrate is made of a material which is transparent to signal light propagating through the optical fiber.
In an embodiment, the substrate is made of glass.
In an embodiment, the substrate is made of ceramic.
In an embodiment, the substrate is made of a semiconductor.
In a preferred embodiment, a normal to the surface of the optical member is not parallel to an optical axis of the optical fiber.
In a preferred embodiment, the second groove is tilted with respect to an upper surface of the substrate.
In an embodiment, at least one optical element which receives light reflected or diffracted by the optical member is provided on the substrate.
In an embodiment, at least one second optical element which receives light passed through the optical member is further provided on the substrate.
In an embodiment, the substrate has an upper surface and a bottom surface, and the device further includes: a first photodetector which is provided on the bottom surface of the substrate and receives light reflected or diffracted by the optical member; and a second photodetector which is pr
Mitsuda Masahiro
Ohya Jun
Tohmon Genji
Uno Tomoaki
Bovernick Rodney
Kang Juliana K.
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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