Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-11-15
2004-10-26
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C385S014000
Reexamination Certificate
active
06810177
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims benefit of Japanese Patent Application No. 2000-348871 filed on Nov. 16, 2000, the contents of which are incorporated by the reference.
The present invention relates to array waveguide grating, optical transmitter and optical communication system with a monitoring function for monitoring signal.
In a DWDM (Dense Wavelength Division Multiplexing) system, for example, alive monitoring and level equalization of signal are required. Accordingly, in such a system couplers or like tapping devices are heretofore provided before or after an AWG (arrayed waveguide grating) to branch signal and monitor the branched signal so as to meet the requirements.
FIG. 25
shows a summary of a prior art synthesizer using a taping device. Signals
101
1
to
101
N
of individual wavelengths are inputted to an arrayed waveguide grating
102
, and outputted as resultant wavelength multiplexed signal
103
therefrom. On the input side of the arrayed waveguide grating
102
, tapping devices
104
1
to
104
N
are provided in correspondence to the individual wavelengths for branching the signal to obtain monitoring signals
105
1
to
105
N
.
In the system using the above synthesizer or array waveguide grating, since the tapping devices
104
1
to
104
N
are used for branching signal, it is necessary to prepare such components as couplers and optical fibers for connecting the couplers in number corresponding to the number of monitoring channels. Therefore, with increase of the channel number the number of components necessary for the monitoring is increased, thus leading to size increase of the arrayed waveguide grating as a whole. In addition, the increase of the number of components leads to device cost increase.
Accordingly, Japanese Patent Laid-Open No. 9-49937 proposes an arrayed waveguide grating, in which N input waveguides for wavelength monitoring are provided in addition to N input waveguides for signal inputting, and also output waveguides for wavelength monitoring are provided each for each side of the N output waveguides.
FIG. 26
shows the construction of this arrayed waveguide grating. As shown, on a substrate
111
are formed N input waveguides
112
for signals, N input waveguides
113
for wavelength monitoring signals, a waveguide array
114
of M waveguides having progressively increasing length with a predetermined waveguide length difference &Dgr;L, N output waveguides
115
, output waveguides
116
and
117
for wavelength monitoring each provided on each side of the output waveguides
115
, an input side slab-waveguide inter-connecting the two pairs input waveguides
112
and
113
and the waveguide array
114
, and an output side slab-waveguide
119
inter-connecting the waveguide array
114
and the three pairs of output waveguides
115
to
117
.
In the proposed array waveguide grating, the N input waveguides
112
connected to the slab-waveguide
118
and the N output waveguides
115
connected to the output side slab-waveguide
119
are used for the signals, while the N input waveguides
113
connected to the input side slab-waveguide
116
and the output waveguides
116
and
117
for wavelength monitoring connected to the output side slab-waveguides
119
are used for the waveguide monitoring. This waveguide grating, therefore, has a drawback that monitoring with the actual signals is impossible.
SUMMARY OF THE INVENTION
An object of the present invention, therefore, is to provide arrayed waveguide grating, optical transmission system and optical communication system, which permits using actual signals to be multiplexed for monitoring these signals and suppressing system size and cost increase as much as possible.
According to a first aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; and a monitor signal port disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for monitoring the multiplexed signal.
In this invention, while outputting the 0-th order diffraction beams obtained from the signals inputted to the slab-waveguide of the arrayed waveguide grating from the output port, the monitor signal port is provided at the focus position of higher order diffraction beams other than the 0-th order, for instance, the 1-st order diffraction beams, for monitoring the wavelength multiplexed signal by using this port.
According to a second aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; and a higher order diffraction beam reflecting means disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for reflecting the higher order diffraction beams to the side of the plurality of input ports.
In this invention, while outputting the 0-th order diffraction beams obtained from the signals inputted to the slab-waveguide of the arrayed waveguide grating, a higher order diffraction beam reflecting means is disposed at the focus position of higher order diffraction beams other than the 0-th order, for instance, the 1-st order diffraction beams, for returning the wavelength multiplexed signal to the side of the input ports. Thus, it is possible to monitor the signals of the different wavelengths obtained as a result of demultiplexing of the signal passed in the reverse direction through the arrayed waveguide grating on the input side thereof.
According to a third aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; a higher order diffraction beam reflecting means disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for reflecting the higher order diffraction beams to the side of the plurality of input ports; and one or more monitor signal ports disposed at a position or positions other than the plurality of input ports for taking out a signal or signals reflected from the higher order diffraction beam reflecting means.
In this invention, while outputting the 0-th order diffraction beams of the signals inputted to the slab-waveguide of the arrayed waveguide grating, a higher order diffraction beam reflecting means is disposed at the focus position of higher order diffraction beams other than the 0-th order, for instance the 1-st order diffraction beams, for returning the wavelength multiplexed signal to the side of the input ports. On the input side, one or more monitor signal ports are disposed, and thus a monitor signal or monitor signals can be obtained from the monitor signal port or ports.
According to a fourth aspect of the present invention, there is provided an optical transmission system comprising: an output side slab-waveguide including, a plurality of signal sources each provided for each individual wavelength, an input waveguide for inputting signals of different wavelen
Barth Vincent P
Font Frank G.
McGinn & Gibb PLLC
NEC Corporation
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