Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
1999-12-22
2002-09-03
Healy, Brian (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S053000, C385S070000, C385S077000, C385S058000, C385S062000, C385S081000
Reexamination Certificate
active
06443628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical fiber connecting apparatus for interconnecting optical fibers in series, an electronic equipment, a network system and an optical fiber connecting method. More particularly, it relates to an optical fiber connecting method, an electronic equipment, a network system and an optical fiber connecting method which can be used with advantage for interconnecting optical fibers in constructing an optical fiber network.
2. Description of the Prior Art
There is an optical fiber network by so-called light communication in which e.g., digital signals are transmitted using an optical fiber. In e.g., an optical fiber network, it is possible to interconnect e.g., household electrical products or information equipments with one another.
Heretofore, an optical fiber is formed of glass. With the advent of the plastic optical fiber (POF), it has become possible to construct an optical fiber inexpensively in homes of offices. The inexpensive structure or the optical fiber network leads to creation of new businesses in the field of utilization of advanced household electrical appliances.
In transmitting signals using an optical fiber, there are known two methods, namely a bi-core type bidirectional optical communication employing two optical fibers, and a bidirectional optical communication employing a sole optical fiber.
In the bi-core type bidirectional optical communication, one of the optical fibers is used for transmission, with the outer being used for reception. On the other hand, the uni-core type bidirectional optical communication uses a sole optical fiber to effect signal transmission/reception, so that the optical fiber cost in constructing the network is one-half that for the bi-core system. Also, with the bi-core system, the two fibers are intended for separate purposes, that is for transmission and for reception, thus leading to directive coupling between the light transmission/reception apparatus and the optical fibers.
The optical fiber is connected to an optical fiber connecting portion provided in the optical transmission/reception apparatus. The optical fiber connection portion of the optical transmission/reception apparatus of the bi-core system is divided into a transmitting side connecting portion for transmitting optical signals and a reception side connecting portion receiving optical signals. Thus, in transmitting/receiving optical signals, the optical signal flowing direction through each optical fiber is necessarily unidirectional. That is, in the optical fiber network, performing optical communication between the first and second optical transmission/reception devices the transmitting side connecting portion of the first optical transmission/reception device needs to be connected by an optical fiber to the receiving side connecting portion of the second optical transmission/reception device. Similarly, the receiving side connecting portion of the first optical transmission/reception device needs to be connected by an optical fiber to the transmitting side connecting portion of the second optical transmission/reception device. If the bi-core system is used, the optical fibers need to be connected in association with respective connecting portions.
On the other hand, the uni-core type bidirectional optical communication is superior in system construction since it does not suffer the aforementioned problem of directivity to assure facilitated connection of the first and second optical transmission/reception devices to the optical fiber connecting portions.
The uni-core bidirectional optical communication recently is stirring up notice in that the amount of the optical fibers used can be decreased and connection to optical fibers is facilitated.
Meanwhile, the uni-core type bidirectional optical communication suffers from the problem of so-called cross-talk.
The cross-talk means the problem that optical signals from a sending party become mixed into optical signals from the optical signal transmission/reception device connected to the sending device over an optical fiber. Among the factors contributing to the cross-talk is a mechanism in which the light transmitted by the sending party is reflected by the remote end of the optical fiber connected to the other optical fiber to prove the remote-end-reflected light which then falls on the light receiving section of the sending device. The reflection at the remote end of the optical fiber, termed Fresnel reflection, is brought about by the properties of light that it is reflected by an interface between two mediums of different refractive indices.
In general, the optical fibers suffers losses, such that, if optical signals are transmitted over an optical fiber, the optical signals are decreased in amplitude. That is, loss in light volume is produced by optical fiber transmission. Therefore, if the optical fiber is of an increased length, the light reflected on the remote end is of a reduced light quantity, due to optical fiber loss, when it returns to the light receiving portion of the own device, thus the effect of the optical crosstalk being reduced. However, if the optical fiber is of an decreased length loss in the light volume by optical fiber transmission is only small, thus increasing the effect of cross-talk by the reflected light from the light receiving portion.
In particular, if a first light transmission/reception device
201
is interconnected to a second light transmission/reception device
202
over a short optical fiber
203
and a long optical fiber
204
, coupled together, remote end reflection poses a serious problem. In the structure shown in
FIG. 1
, the optical fibers
203
,
204
are coupled to each other by a connector
205
. By using the connector
205
, made up of a first connecting member
206
and a second connecting member
207
, detachably connected to each other, the first connecting member
206
, provided in the vicinity of an end face of the optical fiber
203
, and the second connecting member
207
, provided in the vicinity of an end face of the optical fiber
204
, are connected to each other to connect the end face of the optical fiber
203
to the end face of the optical fiber
204
.
Referring to
FIG. 2
, the amplitude attenuation in the optical signals transmitted over the optical fibers
203
,
204
interconnected by the connecting portion
208
is explained.
Referring to
FIG. 2A
, light S transmitted from the first light transmission/reception device
201
is reflected by the connecting portion
208
on the end face of the optical fiber so as to fall as remote end reflected light FX on the first light transmission/reception device
201
. For example, the remote end reflected light Fx falls with an amplitude BFX on the first light transmission/reception device
201
.
On the other hand, in
FIG. 2B
, the first light transmission/reception device
201
receives light D of an amplitude BD sent over optical fibers
203
,
204
from the second light transmission/reception device
202
.
It is noted that arrows A in
FIGS. 2A and 2B
indicate the direction in which occurs the loss in the optical fiber.
If, for example, the amplitude BFX of the remote-end-reflected light FX is close to the amplitude BD of the received light D, the first light transmission/reception device
201
cannot distinguish the remote-end-reflected light FX from the received light D sent from the second light transmission/reception device
202
, thus producing the aforementioned problem of cross-talk.
As a matter of course, the amplitude of the optical signals and the remote-end-reflected light depends on the length of the optical fiber, the number of optical fibers to be interconnected, and on the light emission intensity of the optical transmission/reception apparatus. This poses a serious problem for the light transmission/reception apparatus of the uni-core bidirectional system in an optical fiber network constructed by optical fibers of variable lengths.
As a pertinent technique of prohibiting Fresnel reflection on the conne
Horie Kazuyoshi
Ookubo Kenichi
Shino Kuninori
Frommer William S.
Frommer & Lawrence & Haug LLP
Healy Brian
Shallenburger Joe H.
Sony Corporation
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