Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-07-02
2001-08-28
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C385S036000, C385S031000, C385S124000
Reexamination Certificate
active
06282006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method utilized in optical communications using an optical transmission medium.
2. Description of the Related Art
Optical communications utilizing optical fibers have been carried out for increasing data transmission speed between computers, between a computer and its peripherals or between other digital devices. For such optical communications utilizing optical fibers, the two-fiber bidirectional communications scheme is generally used wherein two optical fibers are used. However, an apparatus for implementing the two-fiber bidirectional communications scheme is required to have a large configuration and the cost of the apparatus is high since two optical fibers are required and a device size of means for emitting signal light and so on is large.
Therefore, the single-fiber bidirectional communications scheme has been developed wherein a single optical fiber is used. An optical transmitter-receiver will now be described as an example of an optical communications apparatus used for the single-fiber bidirectional communications. The optical transmitter-receiver is coupled to a tip of an optical fiber and transmits and receives signal light.
FIG. 1
shows an example of the optical transmitter-receiver used for the single-fiber bidirectional communications.
FIG. 1
is a side view of the main part of the optical transmitter-receiver. The transmitter-receiver comprises: a semiconductor substrate
101
formed of silicon semiconductor or gallium arsenide (GaAs) semiconductor and in an upper surface of which a photodiode
102
as a light receiving means is formed; a prism
103
joined to the surface of the substrate
101
; a semiconductor device
104
in the shape of rectangular solid joined to the surface of the substrate
101
; a laser diode
105
as a light emitting means joined to the top of the semiconductor device
104
; and a lens
107
for allowing first signal light L
1
emitted from the laser diode
105
to be sent to another optical transmitter-receiver to enter an end face of an optical fiber
106
as a communications line and for condensing second signal light L
2
sent from the other transmitter-receiver through the optical fiber
106
and emitted from the end face of the optical fiber
106
and introducing second signal light L
2
to the photodiode
102
.
On the substrate
101
the prism
103
is placed on the photodiode
102
. The semiconductor device
104
is placed on a side of the prism
103
. The laser diode
105
is arranged such that first signal light L
1
is emitted towards the prism
103
. The prism
103
has a slope forming an angle of 45 degrees with the upper surface of substrate
101
, for example, on a side thereof facing the laser diode
105
. A half mirror
103
a
is formed on the slope. For the optical fiber
106
, a large-diameter plastic fiber may be used.
In the optical transmitter-receiver with such a configuration, the laser diode
105
is driven by a drive circuit not shown and first signal light L
1
is emitted from the laser diode
105
. First signal light L
1
enter the half mirror
103
a
of the prism
103
with a numerical aperture (NA) of 0.1, for example, where nearly 50 percent of quantity of light, for example, is reflected to enter the lens
107
. First signal light L
1
is condensed by the lens
107
and enters the optical fiber
106
with a numerical aperture of 0.1, for example. An numerical aperture of first signal light L
1
emitted from the laser diode
105
depends on the laser diode
105
.
On the other hand, second signal light L
2
sent from the other optical transmitter-receiver through the optical fiber
106
is emitted from the optical fiber
106
with a numerical aperture of 0.3, for example. Second signal light L
2
is condensed by the lens
107
so that the numerical aperture is 0.3 and enters the half mirror
103
a
of the prism
103
. Nearly 50 percent of quantity of light passes through to enter the photodiode
102
. The light is then transformed to an electric signal. An numerical aperture of second signal light L
2
emitted from the optical fiber
106
depends on the optical fiber
106
.
In the optical transmitter-receiver shown in
FIG. 1
as an example of optical communications apparatus, however, nearly 50 percent of quantity of light is lost in each of first signal light L
1
and second signal light L
2
. Therefore an optical coupling efficiency and a light receiving efficiency are reduced. In the related art techniques as described so far, it is difficult to improve both light coupling efficiency of a light emitting means such as a laser diode to an optical fiber and light receiving efficiency of a light receiving means such as a photodiode for receiving signal light.
Another problem in the related art techniques is difficulty in removing stray light components, that is, signal light generated by a light emitting means reflecting off an end face of an optical fiber and entering a light receiving means. Such stray light components affect optical communications.
Furthermore, an optical system including an image-formation lens is placed between light emitting and receiving means and an optical fiber in related art techniques. Consequently the number of parts included in the apparatus increases and the configuration of the apparatus is complicated and large in size.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an optical communications apparatus and an optical communications method for achieving a simple and small-sized configuration and improving optical coupling efficiency of a light emitting means to an optical transmission medium and so on to achieve satisfactory optical communications.
An optical communications apparatus of the invention comprises a light emitting means for emitting signal light for optical communications incident off a center axis of an end face of an optical transmission medium. The light emitting means may provide direct optical coupling to the optical transmission medium without an optical system.
In another optical communications apparatus of the invention, one edge of a light receiving means is placed between an incident point of signal light from a light emitting means on an end face of an optical transmission medium and a center axis of the end face.
According to a method of optical communications of the invention, a light emitting means emits signal light incident off a center axis of an end face of an optical transmission medium.
According to the optical communications apparatus of the invention, the light emitting means emits signal light for optical communications incident off the center axis of the end face of the optical transmission medium.
In the other optical communications apparatus of the invention, one edge of the light receiving means is placed between the incident point of signal light from the light emitting means on the end face of the optical transmission medium and the center axis of the end face.
The method of optical communications of the invention allows the light emitting means to emit signal light incident off the center axis of the end face of the optical transmission medium.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
REFERENCES:
patent: 3968564 (1976-07-01), Springthorpe
patent: 4216486 (1980-08-01), Geddes
patent: 4712096 (1987-12-01), Cholin et al.
patent: 5737108 (1998-04-01), Bunch et al.
Matsumoto Shuichi
Tamada Hitoshi
Yamaguchi Takashi
Nguyen Chau Minh
Pascal Leslie
Sonnenschein Nath & Rosenthal
Sony Corporation
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