Remote Node Device, Optical Network Unit and System and Communication Method thereof
Field of the invention
The present disclosure relates to a passive optical network, and more
particularly to a remote node device, optical network unit and system and
communication method thereof for mutual communication between
optical network units in a passive optical network.
Background of the invention
A Passive optical network (PON) has been proposed as a very
promising solution to a broadband optical access network. A variety of
PON solutions have been proposed in recent years, such as TDM-PON,
WDM-PON, OCDM/OFDM-PON and so on. Particularly, the TDM-PON
technology based EPON and 10GPON have been standardized and are
currently being deployed in many countries, and these solutions can offer
a data transmission rate up to lOGbits/s, but there are rapidly developing
Internet services and constantly increasing bandwidth demands, and it is
desirable from the perspective of a long term to define a next-generation
PON (NGPON) access system capable of being compatible with the
current PON system while offering a bandwidth far above lOGbits/s.
While the OCDM/OFDM-PON is still in its infancy, the WDM-PON is
a relatively mature alternative solution capable of a data rate above
40Gbits/s. In the WDM-PON, each ONU is allocated with a dedicated
wavelength, and the WDM-PON has numerous advantages of a high
capacity, compatibility with the legacy PON, etc. With a number of
stacked wavelengths, the total capacity per feeder fiber can easily exceed
40Gbits/s and even reach lOOGbits/s.
However, besides the need to satisfy a bandwidth demand for a
downstream/upstream signal between an Optical Line Terminal (OLT) and
each Optical Network Unit (ONU) in WDM-PON, intercommunication
between different ONUs has become essential because a user can thereby
share data with another ONU at a very high speed and a low delay. In an
example of such an application scenario, universities and enterprises need
to communicate a high amount of data between their different campuses
or branches or different base stations need to cooperatively operate with
each other. However in conventional WDM-PON architecture, direct
intercommunication is not possible between the different optical network
units, because only upstream and downstream transmission links between
the optical line terminal and each optical network unit are available, thus
greatly limiting the flexibility and efficiency of the network.
In order to enable communication between the different optical
network units, there are conventional solutions as illustrated in Fig. 1(a)
and Fig. 1(b). In Fig.l (a), the different optical network units are
fiber-connected, and this enables direct communication between the
different optical network units, but a large amount of wiring means will
induce both a high wiring cost and troublesome network maintenance.
Moreover, there is another solution as illustrated in Fig. 1(b) where
different optical network units communicate with each other over a
communication link of the optical network units to the optical line
terminal via a remote node, but such communication has to undergo two
conversions of optical to electronic to optical (0-E-O), and moreover,
there is generally a large distance, typically tens of kilometers, between
the optical network units and the optical line terminal, so both such a
transmission distance and the optical to electronic to optical conversion
process will necessarily incur an extra delay in communication between
the optical network units, and will also add to an effort of processing at
the optical line terminal and increase the complexity of the system.
Summary of the invention
In view of the prior art and the technical problem thereof identified as
above, it will be very beneficial if it is possible to provide a method of
mutual communication between optical network units at a low cost and a
corresponding device and system thereof.
According to a first aspect of the invention, there is proposed a remote
node device for mutual communication between optical network units in a
passive optical network, wherein the passive optical network includes an
optical line terminal, the remote node device and the optical network units,
and the remote node device includes:
an NxN-arrayed waveguide grating configured to receive upstream
optical signal of one of the optical network units and to output it as a first
optical signal, wherein the first optical signal includes a first part in a first
band for communication between the optical network unit and the optical
line terminal and/or a second part in a second band for mutual
communication between the optical network units, and the first band is
different from the second band;
a 1x2 wavelength division multiplexer configured to separate per band
the first optical signal into the first part and to transmit the first part to the
optical line terminal, and/or into the second part and to output the second
part as a second optical signal; and
a lx(N-l) power distributor configured to transmit the second optical
signal to (N-l) terminals of the NxN-arrayed waveguide grating other
than a terminal from which the first optical signal is outputted and a
terminal for connection with the optical network unit and to transmit the
second optical signal to the corresponding optical network unit through
the NxN-arrayed waveguide grating.
According to a second aspect of the invention, there is proposed an
optical network unit for mutual communication between the optical
network units in a passive optical network, the optical network unit
including:
a wavelength division multiplexer, with an input terminal and first and
second output terminals, configured to separate optical signals received
from the input terminal, including a first optical signal in a first band and
a second optical signal in a second band, into the first optical signal
outputted from the first output terminal and the second optical signal
outputted from the second output terminal;
an optical distributor, with an input terminal connected with the first
output terminal, configured to separate the first optical signal into a third
optical signal and a fourth optical signal including the same information
as the third optical signal;
a first receiver connected with the optical distributor, configured to
receive the third optical signal from the optical distributor and to receive
the downstream data in the third optical signal;
a modulation device connected with the optical distributor, configured
to reflect and modulate the fourth optical signal to transmit the upstream
data in the first band;
a transmitter configured to transmit the optical signal in the second
band for mutual communication between the optical network units
through the wavelength division multiplexer; and
a second receiver configured to receive the second optical signal from
the wavelength division multiplexer and to receive the downstream data in
the second optical signal,
wherein the first band is different from the second band.
In an embodiment, the modulation device is a transmitting modulator
configured to reflect and modulate the fourth optical signal to transmit the
upstream data in the first band.
In an embodiment, the optical network unit is a base station in a
wireless communication network.
According to a third aspect of the invention, there is opposed an
optical network transmission system for mutual communication between
optical network units in a passive optical network, the system including
the remote node device according to the first aspect, a plurality of optical
network units according to the second aspect, and an optical line terminal
connected with the remote node device.
In an embodiment, each of the optical network units for mutual
communication between the optical network units has a unique
wavelength in the first band and a unique wavelength in the second band.
In an embodiment, each of the optical network units for mutual
communication between the optical network units has a unique
wavelength in the first band and a unique wavelength in the second band
with a spacing of 100GHz between the two unique wavelengths.
With the inventive solution, mutual communication between optical
network units can be enabled through a remote node device alone simply
by structurally modifying the remote node device and the optical network
units without modifying a conventional optical line terminal, and in the
meantime, an optical signal for communication will not undergo an
optical to electronic to optical conversion process, that is, communication
between the different optical communication units can be performed
without a communication link between the optical network units and the
optical line terminal through the remote node, thereby avoiding a delay
resulting from a transmission distance of tens of kilometers; and moreover,
the signal will be optically present throughout the communication process
without optical to electronic conversion and subsequent electronic to
optical conversion. These two aspects can act together to greatly lower the
delay in communication.
According to a fourth aspect of the invention, there is provided a
method for mutual communication between optical network units in a
passive optical network, the method including:
a. an NxN-arrayed waveguide grating in a remote node device
receiving an optical signal including a first part in a first band and a
second part in a second band from one or more of at most N optical
network units connected with the NxN-arrayed waveguide grating, and
transmitting the optical signal to a wavelength division multiplexer in the
remote node device;
b. the wavelength division multiplexer separating the optical signal
into the first part and the second part, and transmitting the first part to an
optical line terminal connected with the remote node device and the
second part to a power distributor in the remote node device;
c. the power distributor equally dividing the second part into (N-1)
parts with the same content and transmitting the (N-1) parts respectively
to the NxN-arrayed waveguide grating; and
d. the NxN-arrayed waveguide grating distributing the second part to
the corresponding optical network units,
wherein the first band is different from the second band.
Brief description of drawings
Other features, objects and advantages of the invention will become
more apparent upon review of the following detailed description of
non-limiting embodiments taken with reference to the drawings in which:
Fig. 1(a) and Fig. 1(b) illustrate schematic diagrams of mutual
communication between optical network units in the prior art;
Fig. illustrates a schematic diagram of an inventive idea between
optical network units;
Fig.3 illustrates a schematic structural diagram of a particular remote
node device and optical network unit following the idea illustrated in
Fig.2;
Fig.4 illustrates a schematic diagram of a distribution of a first band
'C and a second band 'L' according to the invention;
Fig.5 illustrates a list of wavelengths used by respective optical
network units;
Fig.6 illustrates a schematic diagram of a configuration of an
NxN-arrayed waveguide grating according to the invention;
Fig.7 illustrates a schematic diagram of an embodiment of an optical
network unit ONU1 broadcasting a signal to other optical network units;
and
Fig.8 illustrates a schematic diagram of wavelength combinations at
respective locations in Fig. 3.
Identical or similar devices (modules) or steps will be denoted by
identical or similar reference numerals throughout the drawings.
Detailed description of embodiments
The following particular description of preferred embodiments will be
given with reference to the drawings constituting a part of the invention.
The drawings exemplarily illustrate particular embodiments in which the
invention can be practiced. The exemplary embodiments are not intended
to exhaust all the embodiments of the invention. As can be appreciated,
other embodiments can be possible or structural or logical modifications
can be made without departing from the scope of the invention. Thus the
following detailed description is not intended to be limiting, and the scope
of the invention will be defined as in the appended claims.
Fig. 1(a) and Fig. 1(b) illustrate schematic diagrams of mutual
communication between optical network units in the prior art, and these
two figures have been described in the Background of the invention
section, so a repeated description thereof will be omitted here.
In order to overcome the drawbacks of the conventional solution, i.e.,
those illustrated in Fig. 1(a) and Fig. 1(b), the invention proposes a solution
as illustrated in Fig. . Fig. illustrates a schematic diagram of an
inventive idea between optical network units. In this figure, the
communication between an optical network unit and another optical
network unit requires no optical signal to be transmitted to an optical line
terminal and then transmitted back from the optical line terminal; and no
extra fiber will necessarily be further deployed between the different
optical network units. Instead, the optical network units can communicate
over an existing line between them and a remote node device, and
moreover, an optical signal will be returned to the corresponding optical
network unit after being transmitted to the remote node device without
being transmitted to the optical line terminal, thereby avoiding optical to
electronic to optical conversions of the optical signal and thus greatly
lowering transmission delay of the signal.
In order to put the inventive idea illustrated in Fig. into practice, the
invention proposes a corresponding solution to an improved remote node
device and optical network unit in hardware. Fig.3 illustrates a schematic
structural diagram of a particular remote node device and optical network
unit following the idea illustrated in Fig. . As can be apparent from the
figure, there is a remote node device 320 for mutual communication
between optical network units in a passive optical network according to
the invention, where the passive optical network includes an optical line
terminal, the remote node device and the optical network units, and the
remote node device includes: an NxN-arrayed waveguide grating 321
configured to receive upstream optical signal of one of the optical
network units and to output it as a first optical signal, where the first
optical signal includes a first part in a first band for communication
between the optical network unit and the optical line terminal and/or a
second part in a second band for mutual communication between the
optical network units, and the first band is different from the second band;
a 1x2 wavelength division multiplexer 322 configured to separate per
band the first optical signal into the first part and to transmit the first part
to the optical line terminal, and/or into the second part and to output the
second part as a second optical signal; and a lx(N-l) power distributor
323 configured to transmit the second optical signal to (N-l) terminals of
the NxN-arrayed waveguide grating other than a terminal from which the
first optical signal is outputted and a terminal for connection with the
optical network unit and to transmit the second optical signal to the
corresponding optical network unit through the NxN-arrayed waveguide
grating.
Moreover as illustrated, an optical network unit for mutual
communication between the optical network units in a passive optical
network according to the invention includes:
A wavelength division multiplexer 341, with an input terminal and
first and second output terminals, configured to separate optical signals
received from the input terminal, including a first optical signal in a first
band and a second optical signal in a second band, into the first optical
signal outputted from the first output terminal and the second optical
signal outputted from the second output terminal;
An optical distributor 342, with an input terminal connected with the
first output terminal, configured to separate the first optical signal into a
third optical signal and a fourth optical signal including the same
information as the third optical signal;
A first receiver 343, connected with the optical distributor, configured
to receive the third optical signal from the optical distributor and to
receive the downstream data in the third optical network unit;
A modulation device 344, connected with the optical distributor,
configured to reflect and modulate the fourth optical signal to transmit the
upstream data in the first band;
A transmitter 346 configured to transmit the optical signal in the
second band for mutual communication between the optical network units
through the wavelength division multiplexer; and
A second receiver 345 configured to receive the second optical signal
from the wavelength division multiplexer and to receive the downstream
data in the second optical signal, where the first band is different from the
second band.
Particularly the optical network unit can be a base station in a wireless
communication network, and those base stations configured according to
the invention can communicate with each other to thereby cooperatively
operate.
Specifically in the transmission process, the optical signal in the first
band for communication between the optical network unit and the optical
line terminal from the optical signal in the second band for mutual
communication between the optical network units are configured with the
different bands, so as to distinguish them from each other. Fig.4 illustrates
a schematic diagram of a distribution of the first band 'C and the second
band 'L' according to the invention, whereby this can have the two signals
distinguished from each other and is also a criterion of optical splitting by
the wavelength division multiplexers 341 and 321. As illustrated in Fig.4,
these two bands L and C are non-overlapping bands. In a single band,
there are also different wavelengths for the different optical network units,
and each of the optical network units for mutual communication between
the optical network units has a unique wavelength in the first band 'C and
a unique wavelength in the second band 'L' with a spacing of 100GHz
between the two unique wavelengths. Fig.5 illustrates a list of
wavelengths used by the respective optical network units. As illustrated in
Fig.5, each optical network unit has the same upstream and downstream
wavelengths for communication between the optical network unit and the
corresponding optical line terminal and also the same upstream and
downstream wavelengths for mutual communication between the optical
network units.
Fig.6 illustrates a schematic diagram of a configuration of an
NxN-arrayed waveguide grating according to the invention. The
NxN-arrayed waveguide grating in a remote node device according to the
invention is configured for achieving a communication between one of
optical network units and other optical network units in a broadcasting
way. Particularly, the NxN-arrayed waveguide grating is a cyclic
NxN-arrayed waveguide grating, where "cyclic" means that an optical
signal transmitted from an optical network unit can be transmitted to any
other optical network unit than the optical network unit transmitting the
optical signal through being broadcasted thereto after being transmitted to
a power distributor through a wavelength division multiplexer.
Fig.7 illustrates a schematic diagram of an embodiment of an optical
network unit ONUl broadcasting a signal to other optical network units.
Taking the optical network unit ONUl broadcasting a signal to other
optical network units as an example for a description, the optical network
unit 1 transmits optical signals including l ΐ and l ΐ -int to a Wavelength
Division Multiplexer (WDM) through an NxN-arrayed waveguide grating,
and the wavelength division multiplexer outputs the optical signal at the
wavelength l ΐ and transmits the optical signal at the wavelength l ΐ -int to
an I2-IN input terminal of the NxN-arrayed waveguide grating through a
power distributor lx(N-l) SC. With the array illustrated in Fig.6, the
optical signal will be transmitted to all the other optical network units
than the optical network unit ONUl, thereby enabling the optical network
unit 1 to pass the signal to other optical network units through
broadcasting the signal thereto.
Those skilled in the art shall appreciate that the other optical network
units each can also transmit a signal to another optical network unit in the
same way, and this can be done by the different optical network units
concurrently.
Fig.8 illustrates a schematic diagram of wavelength combinations at
respective locations in Fig.3. Firstly, taking the downstream as an
example for a description of the figure, in the downstream, there is an
optical signal at the wavelengths li-lN at (a), and this optical signal will
be firstly transmitted to (b) through the wavelength division multiplexer
3 1 without any change and then to the NxN-arrayed waveguide grating
via an I I terminal, and thereafter optical signal at the respective
wavelengths is transmitted to optical network units corresponding to the
wavelengths. In the upstream, optical signals are generated firstly by
optical network units, and the respectively optical network units transmit
the optical signals at and l _hΐ (where i represents the serial number of
an optical network unit) to output terminals 0 1-ON of the NxN-arrayed
waveguide grating, and then they are assembled and then output to the
wavelength division multiplexer WDM 321 from the I I terminal, and in
the wavelength division multiplexer WDM 321, optical signal at the
respective lengths in the first band will be output from (a), and optical
signal at the respective wavelengths in the second band 'L' will be output
from (d), and then the optical signal will be transmitted to (N-l) input
terminals I2-IN of the NxN-arrayed waveguide grating through the power
distributor lx(N-l) SC. With the array illustrated in Fig.6, the optical
signal will be transmitted to all the other optical network units than the
optical network unit transmitting the optical signal, thereby enabling
mutual communication between the optical network units.
With the inventive solution, mutual communication between optical
network units can be enabled through a remote node device alone simply
by structurally modifying the remote node device and the optical network
units without modifying the conventional optical line terminal, and in the
meantime, an optical signal for communication will not undergo the
optical to electronic to optical conversion process, that is, communication
between the different optical communication units can be performed
without a communication link between the optical network units and the
optical line terminal through the remote node, thereby avoiding delay
resulting from a transmission distance of tens of kilometers; and moreover,
the signal will be optically present throughout the communication process
without optical to electronic conversion and subsequent electronic to
optical conversion. These two aspects can act together to greatly lower a
delay in communication.
Those skilled in the art shall appreciate that the invention apparently
will not be limited to the foregoing exemplary embodiments and can be
embodied in other specific forms without departing from the spirit or
essence of the invention. Accordingly the embodiments shall be construed
anyway to be exemplary and non-limiting. Moreover apparently the term
"comprising" will not preclude another element(s) or step(s), and the term
"a" or "an" will not preclude plural. A plurality of elements stated in an
apparatus claim can alternatively be embodied as a single element. The
terms "first", "second", etc., are intended to designate a name but not to
suggest any specific order.

CLAIMS
1. A remote node device (320) for mutual communication between
optical network units in a passive optical network, wherein the passive optical
network includes an optical line terminal, the remote node device and the
optical network units, and the remote node device comprises:
an NxN-arrayed waveguide grating (321) configured to receive
upstream optical signal of one of the optical network units and to output it as
a first optical signal, wherein the first optical signal includes a first part in a
first band for communication between the optical network unit and the optical
line terminal and/or a second part in a second band for mutual communication
between the optical network units, and the first band is different from the
second band;
a 1x2 wavelength division multiplexer (322) configured to separate per
band the first optical signal into the first part and to transmit the first part to
the optical line terminal, and/or into the second part and to output the second
part as a second optical signal; and
a lx(N-l) power distributor (323) configured to transmit the second
optical signal to (N-1) terminals of the NxN-arrayed waveguide grating other
than a terminal from which the first optical signal is outputted and a terminal
for connection with the optical network unit and to transmit the second
optical signal to the corresponding optical network unit through the
NxN-arrayed waveguide grating.
2. An optical network unit for mutual communication between optical
network units in a passive optical network, the optical network unit
comprising:
a wavelength division multiplexer (341), with an input terminal and
first and second output terminals, configured to separate optical signals
received from the input terminal, including a first optical signal in a first band
and a second optical signal in a second band, into the first optical signal
outputted from the first output terminal and the second optical signal
outputted from the second output terminal;
an optical distributor (342), with an input terminal connected with the
first output terminal, configured to separate the first optical signal into a third
optical signal and a fourth optical signal including the same information as
the third optical signal;
a first receiver (343) connected with the optical distributor, configured
to receive the third optical signal from the optical distributor and to receive
the downstream data in the third optical signal;
a modulation device (344) connected with the optical distributor,
configured to reflect and modulate the fourth optical signal to transmit the
upstream data in the first band;
a transmitter (346) configured to transmit the optical signal in the
second band for mutual communication between the optical network units
through the wavelength division multiplexer; and
a second receiver (345) configured to receive the second optical signal
from the wavelength division multiplexer and to receive the downstream data
in the second optical signal,
wherein the first band is different from the second band.
3. The optical network unit according to claim 2, wherein the
modulation device is a transmitting modulator configured to reflect and
modulate the fourth optical signal to transmit the upstream data in the first
band.
4. The optical network unit according to claim 2, wherein the optical
network unit is a base station in a wireless communication network.
5. An optical network transmission system for mutual communication
between optical network units in a passive optical network, the system
comprising the remote node device according to claim 1, a plurality of optical
network units according to any one of claims 2 to 4, and an optical line
terminal connected with the remote node device.
6. The optical network transmission system according to claim 5,
wherein each of the optical network units for mutual communication between
the optical network units has a unique wavelength in the first band and a
unique wavelength in the second band.
7. The optical network transmission system according to claim 6,
wherein each of the optical network units for mutual communication between
the optical network units has a unique wavelength in the first band and a
unique wavelength in the second band with a spacing of 100GHz between the
two unique wavelengths.
8. A method for mutual communication between optical network units
in a passive optical network, the method comprising:
a. an NxN-arrayed waveguide grating in a remote node device
receiving an optical signal including a first part in a first band and a second
part in a second band from one or more of at most N optical network units
connected with the NxN-arrayed waveguide grating, and transmitting the
optical signal to a wavelength division multiplexer in the remote node device;
b. the wavelength division multiplexer separating the optical signal into
the first part and the second part, and transmitting the first part to an optical
line terminal connected with the remote node device and the second part to a
power distributor in the remote node device;
c. the power distributor equally dividing the second part into (N-1)
parts with the same content and transmitting the (N-1) parts respectively to
the NxN-arrayed waveguide grating; and
d. the NxN-arrayed waveguide grating distributing the second part to
the corresponding optical network units,
wherein the first band is different from the second band.