Optical waveguides – With optical coupler
Reexamination Certificate
2001-01-30
2002-08-13
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
C385S016000, C385S024000
Reexamination Certificate
active
06434286
ABSTRACT:
This application claims a priority based on Japanese Patent Application No. 2000-157922 filed on May 29, 2000, the entire contents of which are incorporated herein by reference for all purposes.
BACKGROUND OF THE INVENTION
The present invention relates to an optical signal switching apparatus, and particularly to an optical signal switching apparatus having an optical protection function.
First, structures for realizing an optical protection function, i.e., the optical 1+1 switching structure and the optical 1:1 switching structure will be described (See Japanese Unexamined Patent Laid-Open No. 6-244796 and Tong-Ho Wu, “Fiber Network Service Survivability”, Artech House (1992), pp. 88-93).
FIG. 5
is a block diagram showing the conventional optical 1+1 switching structure. The optical 1+1 switching structure includes an optical transmitter
1001
, an optical coupler (splitter)
1002
, a working optical fiber
1003
, a protection optical fiber
1004
, an optical switch
1005
, and an optical receiver
1006
. On the transmitting side, an optical signal outputted from the optical transmitter
1001
is split by the optical coupler (splitter)
1002
, and outputted to the working and protection optical fibers
1003
and
1004
. On the receiving side, either of the working and protection optical fibers
1003
and
1004
is selected by the optical switch
1005
, and the optical signal is received by the optical receiver
1006
.
FIG. 6
shows a block diagram showing the conventional optical 1:1 switching structure. The optical 1:1 switching structure includes a working optical transmitter
1011
, a protection optical transmitter
1021
, an optical switch
1012
, a working optical fiber
1013
, a protection optical fiber
1014
, an optical switch
1015
, a working optical receiver
1016
, and a protection optical receiver
1026
. On the working transmitting side, an optical signal (data) outputted from the working optical transmitter
1011
is switched by the optical switch
1012
, and usually outputted to the working optical fiber
1013
. On the working receiving side, the working optical fiber
1013
is selected by the optical switch
1015
, and the optical signal is received by the working optical receiver
1016
. On the other hand, also in the protection system, an optical signal (extra data) outputted from the protection optical transmitter
1021
is switched by the optical switch
1012
, and usually outputted to the protection optical fiber
1014
. The protection optical fiber
1014
is selected by the optical switch
1015
, and the optical signal is received by the protection optical receiver
1026
.
Further, in the case of trouble with the working optical fiber
1013
, the optical switches
1012
and
1015
are switched so that data outputted from the working optical transmitter
1011
is received by the working optical receiver
1016
through the protection optical fiber
1014
. In any case, the optical receivers
1006
,
1016
and
1026
receive an optical signal and convert it to an electric signal.
In the above-described techniques, when the optical 1+1 switching structure is changed (expanded) to the optical 1:1 switching structure, it is necessary to replace the optical coupler (splitter) with the optical switch. Further, these switching structures tend to generate rapid fluctuation of optical power, at the time of switching optical signals (changeover of the optical switches). In particular, when an optical amplifier is connected in a subsequent stage to an optical switch, there may arise (a) excessive optical output (optical surge), or (b) effects (disturbances) on optical signals of other wavelengths at the time of general amplification of multiple wavelengths.
SUMMARY OF THE INVENTION
In consideration of the above problems, the present invention provides an optical signal switching apparatus whose hardware can be commonly used for the 1+1 switching structure (splitting on the sending side and switching on the receiving side) and the 1:1 switching structure (switching on the sending side and switching on the receiving side). Further, the present invention provides an optical signal switching apparatus that has sending-side and receiving side switches having the same structure, and thus is suitable for unifying and integrating sending and receiving components. Further, conventionally, an optical coupler should be replaced with an optical switch, and accordingly in-service transformation is difficult. On the other hand, according to the present invention, in-service transformation from the 1+1 switching structure to the 1:1 switching structure and in-service transformation from the 1:1 switching structure to the 1+1 switching structure are possible.
Further, according to the present invention, the control circuits are provided, and accordingly, it is possible to suppress rapid optical power fluctuation accompanying optical signal switching. In particular, the present invention can suppress (a) cause of excessive optical output (generation of optical surge), (b) effect (disturbance) on optical signals of other wavelengths at the time of general amplification of multiple wavelengths, etc. in an optical amplifier.
Further, conventionally, when generation of optical signal interruption (LOS) or the like is detected at the time of switching from working system to protection system, malfunction can occur. However, according to the present invention, switching can be performed without generating optical signal interruption.
In the present invention, in particular, a variable (coupling ratio) optical coupler is applied to a switch of an optical signal switching apparatus. At the time of the 1+1 switching structure, the sending side is made to have a splitting structure (coupling ratio=50%:50%) and the receiving side is made to have a switching structure (coupling ratio=100%:0%, or 0%:100%). At the time of the 1:1 switching structure, the sending side is made to have a switching structure (coupling ratio=100%:0%, or 0%:100%) and the receiving side is made to have a switching structure (coupling ratio=100%:0%, or 0%:100%).
Further, the present invention can realize an optical signal switching function without rapid optical power fluctuation, by combining a variable (coupling ratio) optical coupler with a control circuit that gradually (continuously) controls the coupling ratio of the coupler.
REFERENCES:
patent: 5760936 (1998-06-01), Shirai
patent: 5995689 (1999-11-01), Kuroshima
patent: 6144786 (2000-11-01), Chethik
patent: 6324318 (2001-11-01), Suzuki
patent: 6-244796 (1994-09-01), None
patent: 2000-019471 (2000-01-01), None
“Fiber Network Service Survivability”, Artech House (1992), pp. 88-93.
Hayashi Yukio
Kakizaki Sunao
Kuwano Shinichi
Tsushima Hideaki
Doan Jennifer
Lee John D.
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