Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2000-02-22
2004-01-27
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Plural
C385S047000, C385S039000, C385S031000
Reexamination Certificate
active
06684004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmission system employing an optical wavelength division demultiplexing system and, more particularly, the present invention relates to an optical demultiplexer device which performs demultiplexing using a reduced number of dispersion compensators.
2. Description of the Related Art
Recently, the number of multiplexed wavelengths in an optical wavelength division multiplexing system has increased, from thirty-two (32) wavelengths, to sixty-four (64) wavelengths, to one-hundred twenty-eight (128) wavelengths. Furthermore, transmission signal speeds have increased from 2.5 Gb/s, to 5 Gb/s, to 100 Gb/s, and capacity has increased.
As transmission signal speeds of wavelength division multiplexing systems increase, the penalty rate increases for the self-phase modulation caused by the group velocity dispersion (GVD) of the optical fiber that is the transmission path. Accordingly, the transmission line necessitates measures to decrease the penalty rate for GVD.
FIG. 12
is a dispersion map showing a relationship between a transmission line and a central wavelength. As shown in
FIG. 12
, the fiber or optical device having the dispersion value of the transmission path and the opposite dispersion value is inserted into the transmission path, and at a prescribed interval in the transmission path the dispersion value becomes zero. However, because the dispersion characteristics of the transmission path are dependent upon wavelength, when the wavelength division multiplexing system is used, as shown in
FIG. 11
, even if the dispersion value of the central wavelength is set at zero, the dispersion cannot be set for all the wavelengths.
In order to compensate for the dependence of dispersion value on wavelength, the dispersion is compensated for each wavelength at a reception station.
FIG. 10
is a block diagram of a conventional demultiplexer device for performing dispersion compensation at a reception station for a transmission of 4,000 kilometers.
As shown in
FIG. 10
, the demultiplexer system for dispersion compensation includes optical amplifiers
1
-
1
through
1
-
7
, dispersion compensators (dispersion compensation fibers)
2
-
1
through
2
-
6
, a wavelength demultiplexer unit coupler
3
, optical filters
4
-
1
through
4
-
5
, and optical receivers
5
-
1
through
5
-
5
. Light having respective wavelengths &lgr;
1
through &lgr;
5
is wavelength division multiplexed at an interval of 1 nm. After amplification by the optical amplifier
1
-
1
, the light having a central wavelength of &lgr;
3
is compensated so that it has a dispersion value of zero (0).
After the light from the dispersion compensator
2
-
6
is amplified by the optical amplifier
1
-
2
, it is separated by the wavelength demultiplexer unit coupler
3
into wavelengths &lgr;
1
through &lgr;
5
and input into optical filters
4
-
1
through
4
-
5
, respectively, which correspond to each wavelength. The outputs from optical filters
4
-
1
through
4
-
5
are amplified by the optical amplifiers
1
-
3
through
1
-
7
, respectively, and input into dispersion compensators
2
-
1
through
2
-
5
.
Dispersion compensator
2
-
1
applies dispersion of +800 ps. Dispersion compensator
2
-
2
applies dispersion of +400 ps. Dispersion compensator
2
-
3
applies dispersion of 0 ps. Dispersion compensator
2
-
4
applies dispersion of −400 ps. Dispersion compensator
2
-
5
applies dispersion of −800 ps. The outputs of dispersion compensators
2
-
1
through
2
-
5
are photoelectrically converted by optical receivers
5
-
1
through
5
-
5
, respectively.
In the above-described manner, by compensating with different dispersion values using dispersion compensators
2
-
1
through
2
-
5
, dispersion conversion is performed such that all dispersion volumes between the wavelengths are zero (0).
However, as shown in
FIG. 10
, when a dispersion compensator corresponding to each wavelength is provided, expensive dispersion compensators require the value equivalent to the compensation value.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a demultiplexer device for demultiplex system which reduces the use of expensive dispersion compensators by half while performing demultiplexing.
It is another object of the present invention to provide a demultiplexing device for demultiplex system which performs demultiplexing without the use of wavelength demultiplexing couplers.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with an optical demultiplexer device for an optical wavelength demultiplexer system, comprising an optical circulator, a dispersion compensator, and an optical filter. A particular wavelength of light is divided by the optical filter, round tripped through the dispersion compensator and output from the optical circulator. A wavelength of light different from the particular wavelength of light passes through the dispersion compensator and optical filter and is output from the optical filter.
Objects and advantages of the present invention are achieved with an optical demultiplexer device, comprising a first optical demultiplexer circuit, including a first optical circulator having a first port, a second port and a third port, wherein multiplexed light is input into the first port, and the light input to the first port is output from the second port, and light input into the second port is output from the third port; a dispersion compensator having an input unit and an output unit, the dispersion compensator being coupled to the second port of the first optical circulator at one of the input or output unit; a first filter coupled to another of the input or output unit to reflect light having a specified wavelength and to transmit light having a wavelength other than the specified wavelength; a second optical circulator having a first port, a second port and a third port, wherein the light transmitted by the first optical filter is input to the first port; and a second optical filter coupled to the second port of the second optical circulator to reflect light having the specified wavelength.
The optical demultiplexer device may further comprise a second optical demultiplexer circuit, including a first optical circulator having a first port, a second port and a third port, wherein multiplexed light is input into the first port, and the light input to the first port is output from the second port, and light input into the second port is output from the third port; a dispersion compensator having an input unit and an output unit, the dispersion compensator being coupled to the second port of the first optical circulator at one of the input or output unit; a first optical filter coupled to another of the input or output unit to reflect light having a specified wavelength and to transmit light having a wavelength other than the specified wavelength; a second optical circulator having a first port, a second port and a third port, wherein the light transmitted by the first optical filter is input to the first port; and a second filter coupled to the second port of the second optical circulator to reflect light having at least one specified wavelength.
In accordance with the present invention, multiplexed light that is branched into a plurality of wavelengths is input into the first port of the first optical circulator of the first optical demultiplexer circuit, and is input into the first port of the first optical circulator of the second optical demultiplexer circuit.
In accordance with embodiments of the present invention, the third port of the first optical circulator of the first demultiplexer circuit is coupled to the first port of the first optical circulator of the second optical demultiplexer circuit.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with demultiplexer device comprising a first unit, including a first optical c
Bovernick Rodney
Fujitsu Ltd.
Pak Sung
Staas & Halsey , LLP
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