Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2000-11-06
2003-05-27
Kim, Ellen E. (Department: 2874)
Optical waveguides
With optical coupler
Plural
C359S199200, C359S199200
Reexamination Certificate
active
06571032
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to terminal equipment for an optical communication system. More specifically, the present invention relates to optical transmitters multiplexing and optical receivers demultiplexing signals having substantially equal dispersion.
U.S. Pat. No. 5,224,183, entitled “Multiple Wavelength Division Multiplexing Signal Compensation System and Method Using Same” and issued on Jun. 29, 1993, discloses a wavelength-division multiplexing (WDM) system.
FIG. 1
illustrates a wavelength-division multiplexing system disclosed in U.S. Pat. No. 5,224,183. As
FIG. 1
illustrates, each wavelength has an associated laser coupled to a dispersion-compensation fiber, which in turn is coupled to a common wavelength division multiplexer. For example, lasers
12
,
14
and
16
are coupled to dispersion-compensation fibers
18
,
20
and
22
, respectively, which are coupled to wavelength division multiplexer
24
. In this example, the wavelength of laser
12
is 1540 nm; the wavelength of laser
14
is 1550 nm; the wavelength of laser
16
is 1560 nm. Wavelength division multiplexer
24
is coupled to a an additional dispersion-compensating fiber
26
and transmission fiber
28
.
This known system individually compensates the dispersion associated with each wavelength before the optical signals are multiplexed by the wavelength division multiplexer (and after the optical signals are demultiplexed by the wavelength division demultiplexer (not shown in FIG.
1
)). This is performed for each wavelength by a separate and unique dispersion-compensation fiber associated with that wavelength: dispersion compensation fiber
12
has a dispersion of −20 ps
m at its wavelength (1540 nm), dispersion-compensation fiber
14
has a dispersion of −200 ps
m at its wavelength (1550 nm), and dispersion-compensation fiber
16
has a dispersion of −360 ps
m at its wavelength (1550 nm). These dispersion-compensation fibers compensate individually for each particular wavelength to produce a unique residual dispersion associated with each wavelength. Each wavelength is subsequently compensated by the dispersion-compensation fiber
26
and transmission fiber
28
. By eliminating the residual dispersion associated with each wavelength at the wavelength-division multiplexer
24
, the dispersion of all of the wavelengths at the end of the transmission fiber
28
can be controlled to a desired amount, such as for example, approximately zero dispersion for approximately all of the wavelengths.
Such a WDM system, however, suffers several shortcomings. First, each wavelength requires a separate and unique dispersion-compensating fiber disposed, for example, between the respective laser and the wavelength-division multiplexer of the optical transmitter. Similarly, each wavelength requires a separate and unique dispersion-compensation fiber disposed, for example, between the wavelength-division multiplexer and the respective detector (not shown in FIG.
1
). As WDM systems having more and more information channels are designed, adding more and more dispersion-compensation fibers associated with each wavelength make the WDM system more complex and expensive.
Second, polarization of the optical signals received by the wavelength-division multiplexer cannot be maintained due to the unique dispersion-compensation fibers required by each wavelength. Consequently, although desirable for the optical signals associated with each wavelength to have an associated polarization that is orthogonal to adjacent wavelengths, such an arrangement is not possible where the polarization cannot be maintained.
SUMMARY
An apparatus for communicating data through information channels each being associated with its own wavelength comprises modulators and an optical multiplexer. Each modulator is associated with its own wavelength. The optical multiplexer is operationally coupled to the modulators. The optical multiplexer receives multiple input optical signals each of which is received from its own modulator. Each input optical signal has its own dispersion substantially equal to a dispersion of each remaining input optical signals.
REFERENCES:
patent: 5224183 (1993-06-01), Dugan
patent: 5392147 (1995-02-01), Kaede et al.
patent: 5546210 (1996-08-01), Chraplyvy et al.
patent: 5559920 (1996-09-01), Chraplyvy et al.
patent: 5841557 (1998-11-01), Otsuka et al.
patent: 6021235 (2000-02-01), Yamamoto et al.
patent: 6275314 (2001-08-01), Ishikawa et al.
patent: 6456755 (2002-09-01), Sonoda
Kerfoot, III Franklin W.
Pilipetskii Alexei N.
Kim Ellen E.
Tyco Telecommunications (US) Inc.
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