Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-02-23
2003-05-27
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06570685
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmission apparatus, and particularly to an optical ring system using a wavelength-division multiplexing technology and the structure of a node for optical communication used in the optical ring system.
2. Description of Related Art
A prior art of an optical transmission apparatus having a ring structure in which a plurality of nodes are connected in the form of a ring is described with reference to
FIGS. 1 and 2
. The prior art is described in detail in a paper entitled “Highly Reliable and Economical WDM Ring with Optical Self-Healing and 1:N Wavelength Protection” by Uehara et al., printed in the Conference Publication (published in 1997) of the 11th International Conference on Integrated Optics and Optical Fiber Communications, 23rd European Conference on Optical Communications.
FIG. 1
shows the configuration of an optical transmission apparatus according to a first prior art. An optical transmission apparatus shown in
FIG. 1
has been implemented by combination of a wavelength-multiplexed optical transmission technology and a 4-fiber-ring transmission apparatus.
FIG. 1
shows an example of an optical ring system using m nodes. Each of the nodes included in the system multiplexes optical signals having wavelengths of &lgr;1 to &lgr;n and transmits them as a wavelength-division-multiplexed optical signal.
The optical transmission apparatus shown in
FIG. 1
is composed of optical add/drop multiplexing nodes
301
-
1
to
301
-m, transmission path optical fibers
302
-
1
to
302
-
4
(
302
-
1
: counterclockwise working system,
302
-
2
: clockwise working system,
302
-
3
: counterclockwise protection system, and
302
-
4
: clockwise protection system), an optical preamplifier
351
, a wavelength demultiplexer
352
, a wavelength multiplexer
353
, an optical booster amplifier
354
, an optical preamplifier
355
, a wavelength demultiplexer
356
, a wavelength multiplexer
357
, an optical booster amplifier
358
, an optical preamplifier
359
, a wavelength demultiplexer
360
, a wavelength multiplexer
361
, an optical booster amplifier
362
, an optical preamplifier
363
, a wavelength demultiplexer
364
, a wavelength multiplexer
365
, an optical booster amplifier
366
, an add/drop multiplexers (ADM)
367
-
1
to
367
-n, and transponders (TRPD)
371
to
378
each regeneratively repeating by converting a received optical signal into an electrical signal and converting again it into an optical signal.
In
FIG. 1
, the m nodes are connected with one another in the form of a ring by a total of four transmission path optical fibers two of which connect bi-directionally the working system and the other two of which connect bi-directionally the protection system. Each of the nodes sends out an optical signal obtained by multiplexing n wavelengths of &lgr;1 to &lgr;n in wavelength division to each of the four optical fiber transmission paths. And each of the nodes receives an optical signal obtained by multiplexing n wavelengths of &lgr;1 to &lgr;n in wavelength division from each of the four optical fiber transmission paths.
Next, operation in each of the nodes of an optical transmission apparatus of a former ring structure having the above-mentioned structure is described in the following.
An optical signal received from a transmission path optical fiber of the counterclockwise working system is amplified by the optical preamplifier
351
and is demultiplexed by the wavelength demultiplexer
352
into n wavelength components of &lgr;1 to &lgr;n. Hereupon, the n optical signals of &lgr;1 to &lgr;n obtained by wavelength-demultiplexing are respectively inputted into the add/drop multiplexers (ADM)
367
-
1
to
367
-n. That is to say, an optical signal of &lgr;1 is inputted into the ADM
367
-
1
, an optical signal of &lgr;2 is inputted into the ADM
367
-
2
, and an optical signal of &lgr;n is inputted into the ADM
367
-n. And n optical signals of &lgr;1 to &lgr;n in wavelength are outputted from the ADM's
367
-
1
to
367
-n. Through the transponders
371
to
378
, an optical signal of &lgr;1 in wavelength is outputted from the ADM
367
-
1
, an optical signal of &lgr;2 in wavelength is outputted from the ADM
367
-
2
, and an optical signal of &lgr;n in wavelength is outputted from the ADM
367
-n. The n optical signals of &lgr;1 to &lgr;n in wavelength outputted from the ADM's
367
-
1
to
367
-n are multiplexed in wavelength division by the wavelength multiplexer
353
. Optical output of the wavelength multiplexer
353
is amplified by the optical booster amplifier
354
and then is sent out to the optical fiber transmission path of the counterclockwise working system. Also with regard to optical signals transmitted and received through the other transmission paths, namely, the clockwise working system
302
-
2
, counterclockwise protection system
302
-
3
and clockwise protection system
302
-
4
, the multiplexing and demultiplexing operations of wavelengths of &lgr;1 to &lgr;n are performed in the same way as the above-mentioned operation. In
FIG. 1
, the optical preamplifier
355
, the wavelength demultiplexer
356
, the wavelength multiplexer
357
and the optical booster amplifier
358
are applied to the clockwise working system, the optical preamplifier
359
, the wavelength demultiplexer
360
, the wavelength multiplexer
361
and the optical booster amplifier
362
are applied to the counterclockwise protection system, and the optical preamplifier
363
, the wavelength demultiplexer
364
, the wavelength multiplexer
365
and the optical booster amplifier
366
are applied to the clockwise protection system.
Operation in the ADM
367
-
1
is as follows.
Each of the four optical signals of &lgr;1 in wavelength inputted by the wavelength demultiplexers
352
,
356
,
360
and
364
is processed by an optical/electrical (O/E) conversion, an overhead signal termination and a time-division demultiplexing process in a high-speed signal reception interface part (HSRx), and then is inputted into a cross-connecting part (TSA) as an electrical data signal. And the electrical data signals are each inputted from the cross-connecting part (TSA) into the high-speed signal transmission interface part (HSTx), and are each processed by a time-division multiplexing process, an overhead signal insertion and an electrical/optical (E/O) conversion, and then an optical signal of &lgr;1 in wavelength is outputted to the wavelength multiplexers
353
,
357
,
361
and
365
. A cross-connecting part (TSI) has a function of selectively connecting four pairs of electrical data signals inputted from the high-speed signal reception interface part (HSRx) and four pairs of electrical data signals to be outputted to the high-speed signal transmission interface part (HSTx) according to a state of breakage of a transmission path and the like in the ring network, and a function of disconnecting or connecting a part or the whole of an inputted electrical data signal from or with a low-speed signal interface part (LS) and inserting a signal from the low-speed signal interface part (LS) into an output signal.
This optical ring system, in case that a transmission path breaks down, changes over an optical signal being transmitted in the working system transmission path to a transmission path of the protection system by changing over the path in the cross connection part (TSI) by an electrical switch and thereby recovers the transmission path from the breakdown. That is to say, in case that break of an optical transmission path of the working system has occurred, the switch of the cross-connecting part (TSI) in each ADM operates to change over an optical signal transmission path from the working system to the protection system.
Communication through the protection system optical transmission path performed by the first prior art is called Standby-Line-Access, and makes possible two kinds of communication using the working system and the protection system in case that no failure oc
Asahi Koji
Fujita Sadao
Chan Jason
Tran Dzung
Whitham Curtis & Christofferson, P.C.
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