Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-11-21
2001-02-13
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06188495
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field of an optical transmission-reception apparatus used in a single-core bi-directional optical communication circuit using an optical fiber and more particularly, to an optical transmission-reception apparatus for use in an optical communication circuit using a plastic optical fiber in a domestic communication network.
2. Description of the Prior Art
There has been proposed an optical communication circuit connected to an optical transmission-reception apparatus. The optical transmission-reception apparatus constituting such an optical communication circuit is used for connection between various apparatuses such as a computer, a digital video apparatus, and an audio apparatus.
FIG. 1
shows a conventional optical transmission-reception apparatus including a socket
104
to be connected to a plug
103
holding a first plastic optical fiber
101
for transmission and a second plastic optical fiber
102
for reception. In this optical transmission-reception apparatus, the socket
104
has a built-in light-emitting element
105
for emitting a first optical signal
106
which has been modulated according to a signal to be transmitted and a built-in light-receiving element
108
for receiving a second optical signal
107
which has been modulated according to a transmitted signal. The light-emitting element
105
and the light-receiving element
108
are divided from each other by a shielding wall
109
to prevent leaking of the first optical signal
106
and the second optical signal
107
into the light-receiving element
108
and the light-emitting element
105
, respectively.
In a state when the plug
103
is connected to the socket
104
, the first optical signal
106
emitted from the light-emitting element
105
is introduced into an end face of the first plastic optical fiber
101
. Moreover, in the state when the plug
103
is connected to the socket
104
, the second optical signal
107
emitted from an end face of the plastic optical fiber
102
is received by the light-receiving element
108
.
In an optical communication circuit constituted by using the aforementioned transmission-reception apparatus, two plastic optical fibers are used: one for transmission and the other for reception. Consequently, the plug and the socket have a considerable size, which is not preferable for an optical communication circuit to be used as a domestic communication network. That is, the optical communication circuit to be used as a domestic communication network should be simplified as a single-core bi-directional optical communication circuit.
In an optical transmission-reception apparatus constituting a single-core bi-directional optical communication circuit, it is necessary to coaxially overlap the first optical signal which is a transmission signal and the second optical signal which is a reception signal. As means for coaxially overlapping two beams having opposite advancing directions, there can be considered use of a so-called half mirror (semitransparent film). That is, one of the first and the second optical signals has an optical path passing through the half mirror and the other of the optical signals has an optical path reflected by the half mirror. Thus, the first optical signal and the second optical signal are coaxially overlapped.
However, in this half mirror, the total of the transmittance and the reflectance does not exceed 100% and each of the transmittance and the reflectance is equal to or less than 50%. That is, when overlapping the first optical signal and the second optical signal by using a half mirror, the optical signal passing through this half mirror and the optical signal reflected by this half mirror have a loss of about 50%, respectively.
If the first optical signal which is a transmission signal is decreased in light quantity and introduced into the plastic optical fiber, the transmission distance available is reduced and it is impossible to assure a sufficient performance and reliability of the optical communication circuit.
In order to compensate the loss of light quantity because of the half mirror, it can be considered to increase the light quantity emitted by the light-emitting element. However, in a laser diode used as the light-emitting element, the light quantity emitted has a trade-off relationship with the service life and reliability of the element. If the light quantity emitted is increased, then the service life of the element is reduced and its reliability is lowered.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical transmission-reception apparatus constituting a single-core bi-directional optical communication circuit in which the efficiency of introduction of a transmission optical signal to an optical fiber is improved to enable to realize a sufficient performance and reliability of the optical communication circuit without increasing the light quantity emitted from a light-emitting element which outputs the transmission optical signal.
The optical transmission-reception apparatus according to the present invention includes: an optical transmission medium connection block to which an optical transmission medium is connected for transmitting to a second end face; a first optical signal inputted from a first end face; light-emitting means for emitting the first optical signal which is in a linearly polarized state; a beam splitting film is provided on an optical path starting at the light-emitting element and reaching the first end face of the optical transmission medium, so as to split a second optical signal emitted from the first end face of the optical transmission medium, from an optical path reaching the light-emitting element; and light-receiving means for receiving the second optical signal via the beam splitting film.
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patent: 5283680 (1994-02-01), Okugawa et al.
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patent: 5479540 (1995-12-01), Boudrean et al.
patent: 5566265 (1996-10-01), Spaeth et al.
patent: 5844682 (1998-12-01), Kiyomoto et al.
patent: 5852507 (1998-12-01), Hall
Inoue Tatsuo
Toriumi Yoichi
Limbach & Limbach L.L.P.
Pascal Leslie
Phan Hanh
Smith, Esq. Andrew V.
Sony Corporation
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