Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-03-04
2001-11-06
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06313933
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a bidirectional wavelength division multiplex transmission apparatus using a wavelength division multiplex optical amplifier.
FIG. 7
shows the first example of the conventional bidirectional transmission apparatus using the bidirectional wavelength division multiplex optical amplifier. As shown in
FIG. 7
, this apparatus uses WDM (Wavelength Division Multiplex) couplers
21
to
23
as optical branching/inserting means for signal light beams to be transmitted bidirectionally. Reference numeral
2
denotes an optical multiplexer; and
3
, a wavelength division multiplex transmission optical amplifier.
FIG. 8
shows the second example of the apparatus using the bidirectional wavelength division multiplex optical amplifier. As shown in
FIG. 8
, this apparatus uses optical circulators
31
and
32
to make only the optical transmission lines bidirectional. The apparatus amplifies branched wavelength division multiplex signals by using wavelength division multiplex transmission amplifiers
41
and
42
separately used for reverse and forward links.
In the apparatus as the first example using the WDM couplers, the respective wavelengths must be spaced apart from each other by at least about 10 nm, as indicated by the wavelength transmission range characteristics in FIG.
9
. For this reason, the number of wavelengths which can be multiplexed is limited, and optical transmission lines for transmitting optical signals cannot be effectively used.
The apparatus as the second example, which makes only the optical transmission lines bidirectional, requires two optical amplifiers. This increases the cost of the apparatus and degrades maintainability.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a bidirectional wavelength division multiplex transmission apparatus which effectively uses optical transmission lines.
It is another object of the present invention to provide a bidirectional wavelength division multiplex transmission apparatus which prevents an increase in apparatus cost and degradation in maintainability.
In order to achieve the above objects, according to the present invention, there is provided a bidirectional wavelength division multiplex transmission apparatus comprising first optical branching/inserting means, connected to a first optical transmission line through which reverse and forward wavelength division multiplex optical signals having different wavelengths are transmitted, for branching/inserting the optical signals, second optical branching/inserting means, connected to a second optical transmission line through which reverse and forward wavelength division multiplex optical signals having different wavelengths are transmitted, for branching/inserting the optical signals, multiplexing means for performing wavelength division multiplexing of the optical signals output from the first and second branching/inserting means, an optical amplifier for amplifying the wavelength division multiplex optical signal output from said multiplexing means, and demultiplexing means for demultiplexing the wavelength division multiplex optical signal amplified by the optical amplifier on the basis of the wavelengths, and outputting the demultiplexed optical signal to one of the first and second optical transmission lines which corresponds to a propagating direction, the demultiplexing means being constituted by an optical demultiplexer for demultiplexing the optical signal from the optical amplifier into two optical signals, and optical filters for allowing optical signals, of the demultiplexed optical signals, which have specific wavelengths to pass therethrough, and outputting the signals to one of the first and second optical branching/inserting means which corresponds to the propagating direction.
REFERENCES:
patent: 5652675 (1997-07-01), Shibuya
patent: 5689594 (1997-11-01), Mao
patent: 5748350 (1998-05-01), Pan et al.
patent: 5812306 (1998-09-01), Mizrahi
patent: 5978131 (1999-11-01), Lauzon et al.
patent: 6-342952 (1994-12-01), None
patent: 7-212316 (1995-08-01), None
patent: 8-163028 (1996-06-01), None
Japanese Office Action, dated May 16, 2000, with English Language translation of Japanese Examiner's comments.
Chan Jason
Leung Christina Y
McGuireWoods LLP
NEC Corporation
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