Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-12-04
2002-02-26
Rosenberger, Richard A. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
Reexamination Certificate
active
06351584
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmitter-receiver for single-core two-way optical communication and an optically sending/receiving method.
2. Description of the Related Art
The need for a system for transmitting a signal by optical communication more and more has increased as information communication is varied. If a signal is transmitted by optical communication, a single-core two-way telecommunication line system using one optical fiber and a two-core two-way telecommunication line system using two optical fibers are normally used.
For the single-core two-way optical communication system, an optical transmitter-receiver shown in
FIG. 1
is used.
The conventional type optical transmitter-receiver shown in
FIG. 1
is required to split an optical path for sending and an optical path for receiving so as to realize single-core two-way optical communication. The optical path for sending means an optical path in which beams outgoing from a laser beam generating source
1002
are reflected by the reflecting surface
1004
a
of a beam splitter
1004
and are incident upon the end
1011
a
of an optical fiber
1011
through a focusing lens
1003
.
The optical path for receiving means an optical path in which outgoing beams from the optical fiber
1011
are focused with the focusing lens
1003
and are incident on a photodiode
1005
through the reflecting surface
1004
a
of the beam splitter
1004
. That is, the beam splitter
1004
is used for splitting the optical path for sending and the optical path for receiving.
As described above, in sending, beams from the laser beam generating source
1002
are reflected by the reflecting surface
1004
a
of the beam splitter
1004
. However, in case beams are reflected, beams equivalent to some percent of the above beams are directly incident upon the beam splitter
1004
through the reflecting surface
1004
a
as stray light
1008
a.
Stray light
1008
a
incident upon the beam splitter
1004
as described above is also incident upon the photodiode
1005
. That is, the photodiode
1005
receives not only light for receiving normally outgoing from the optical fiber
1011
but stray light
1008
a
as crosstalk. When stray light
1008
a
is incident upon the photodiode
1005
, the signal-to-noise ratio (S/N) of the photodiode
1005
is deteriorated and the transmission distance of the optical fiber
1011
is reduced.
There is also an example of another conventional type that a polarizing beam splitter in accordance with the oscillation and the polarization of the laser beam generating source
1002
is used in place of the beam splitter
1004
, however, as a laser beam is also not complete linear polarized light in this case, stray light
1008
a
cannot be completely prevented from being generated in sending.
As outgoing beams from the optical fiber
1011
are also reflected by the reflecting surface (the mirror finished surface)
1004
a
of the beam splitter
1004
when the photodiode
1005
receives the above outgoing beams, beams equivalent to some percent of beams for receiving do not reach the photodiode
1005
and are wasted. Received beams reflected by the reflecting surface
1004
a
of the beam splitter
1004
are incident upon the laser beam generating source
1002
and may instabilize characteristics for oscillating the laser beam generating source
1002
.
The present invention is made to solve the above problems and the object is to provide an optical transmitter-receiver and an optically sending/receiving method wherein crosstalk can be prevented from being generated in the case of optical sending/receiving using a single-core two-way optical communication interface circuit and optically sending/receiving efficiency can be enhanced.
SUMMARY OF THE INVENTION
The above object of the present invention is achieved by an optical transmitter-receiver based upon an optical transmitter-receiver connected to an optical fiber used for a single-core two-way optical communication channel for sending a first optical signal to be sent to the end of the optical fiber and for receiving a second optical signal sent via the optical fiber and characterized by being provided with beams generating means for emitting a first optical signal, light receiving means for receiving a second optical signal outgoing from the end of the optical fiber and an optical system for making a first optical signal from the beams generating means incident upon the incident end of the optical fiber in a direction different from a direction in which a second optical signal is outgoing from the end of the optical fiber.
The present invention relates to the optical transmitter-receiver connected to an optical fiber used for a single-core two-way optical communication channel for making a first optical signal to be sent incident upon the end of the optical fiber and receiving a second optical signal sent via the optical fiber. The beams generating means of the optical transmitter-receiver emits a first optical signal. The light receiving means receives a second optical signal outgoing from the end of the optical fiber. The optical system makes a first optical signal from the beams generating means incident upon the incident end of the optical fiber in a direction different from a direction in which a second optical signal is outgoing from the end of the optical fiber.
Hereby, as the optical system makes a first optical signal from the beams generating means incident upon the end of the optical fiber in a direction different from a direction in which a second optical signal is outgoing from the end of the optical fiber, the optical path of a first optical signal and the optical path of a second optical signal can be approximately completely made independent. Hereby, as a part of a first optical signal is never received together with a second optical signal by the light receiving means, optical crosstalk (stray light) can be removed from the light receiving means.
In the present invention, after a focusing member focuses a first optical means from the beams generating means, a direction converting element converts the optical path of the focused first optical signal to a direction different from a direction in which a second optical signal is outgoing from the end of the optical fiber and can make the first signal incident upon the end of the optical fiber desirably by providing the focusing member and the direction converting element to the optical system. Hereby, the first optical signal from the beams generating means can be made efficiently incident upon the end of he optical fiber.
In the present invention, desirably if the direction converting element of the optical system is provided with a reflecting film with simple structure for converting the optical path of a first optical signal to a direction different from a direction in which a second optical signal is outgoing from the end of the optical fiber, a first optical signal can be made securely and efficiently incident upon the end of the optical fiber.
In the present invention, desirably if the reflecting film is a total reflection film, a first optical signal can be made incident upon the end of the optical fiber without the loss of the luminous energy of the first optical signal.
In the present invention, if a package for housing the beams generating means, the optical system and the light receiving means is provided and is attached to the end of the optical fiber with the end of the optical fiber directed to the light receiving means so that the package can be detached, the optical fiber can be readily attached/detached to/from the optical transmitter-receiver.
In the present invention, desirably if light shielding means is arranged in the package to prevent beams from the beams generating means from leaking out of the package, beams from the beams generating means can be prevented from leaking out of the package even if the optical fiber comes off the package.
In the present invention, desirably if the light receiving means is arranged outside
Horie Kazuyoshi
Ookubo Kenichi
Shino Kuninori
Toriumi Yoichi
Yoshida Hideki
Nguyen Tu T.
Rosenberger Richard A.
Sonnenschein Nath & Rosenthal
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