JP2002217837A - Optical access network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical access network system, in which a single center side device is connected to a plurality of user side devices in a star connection configuration into a large-capacity optical access network system at a low equipment cost. SOLUTION: An optical part, that operates as a wavelength demultiplexer, with respect to an outgoing WDM(wavelength division multiplexed) signal and acts as an optical coupler with respect to incoming signal light of a single wavelength, is used. A WDM system, in which a communication band can be a mass band, is used for the outgoing direction, and a single wavelength is used for the incoming direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical network system for large-capacity data communication using a wavelength multiplexing technique.

[0002]

2. Description of the Related Art FIG. 5 is a schematic block diagram showing a conventional optical access network using a wavelength division multiplexing (WDM) technique. In this configuration, an OLT (Optical Line Terminal) 51 is provided on the center station side, and ONU (Optical Net Terminal) is provided on the user side.
work Unit: optical network unit) 53-1 to 53-n
Are connected in a star shape via a wavelength multiplexer / demultiplexer 52 such as an arrayed waveguide element. OLT51
Are the ONUs 53-1 to 53-n in which a signal from a center node device (telephone exchange, IP router, or the like) is designated.
And ONU 53-1 to 53-
n to collect the signals from n and output them to the node device. ONU53-1 to 53-n are OLT51
It has a function of terminating the signal from the terminal and, if necessary, converting the signal to a format that can be received by the user terminal and relaying the signal, and a function of relaying the signal from the user terminal to the OLT 51 in an appropriate format. ONU
Different wavelengths λ1 to λn are assigned to 53-1 to 53-n, respectively, and the OLT 51 and the ONUs 53-1 to 53-n
Is communicated using the wavelength.

[0003] An optical access network using such a WDM is an STM-PDS (Synchrod) using a single wavelength.
onous Transfer Mode-Passive Double Star: Synchronous Transfer Mode-Passive Double Star
PDS (Asynchronous Transfer Mode-Passive Double)
star: Asynchronous transfer mode-passive optical system
The optical branching means from the OLT to each ONU uses a wavelength demultiplexer that distributes a path for each wavelength, instead of an optical coupler that simply divides the optical power and splits it. For this reason, OLT
And the transmission distance between the ONU and the O
The number of NUs can also be increased. Also, by using the WDM method, the same transmission distance and O
If the number is NU, the communication speed can be increased.

[0004]

In an optical access network using WDM, different wavelengths are used for each ONU. Therefore, an ONU provided with a light source (a variable wavelength light source) capable of selectively generating a plurality of wavelengths is used. Or it is necessary to prepare a plurality of types of ONUs having different generation wavelengths. Further, in order for the upstream signal from each ONU to pass through the wavelength multiplexer / demultiplexer and reach the OLT, it is necessary to stabilize the generated wavelength of each ONU within the pass bandwidth of the wavelength multiplexer / demultiplexer. For these reasons, the equipment cost of the ONU of the system using WDM is higher than that of the system using a single wavelength.

[0005] The present invention solves such a problem and provides an ON
An object is to provide an optical access network system in which the configuration of U is simplified and the equipment cost is low.

[0006]

According to the optical access network system of the present invention, the WDM system capable of increasing the communication bandwidth in the downstream direction is used, and the wavelengths generated by the ONUs are all the same as a single wavelength in the upstream direction. To Simply ONU
If all of the wavelengths generated are the same, a WDM access network different from an ordinary single-wavelength access network has a wavelength multiplexer / demultiplexer on the way, so that an upstream signal from each ONU can be input to the OLT. Can not. Therefore, in the present invention, an optical component configured to function as a wavelength demultiplexer for a downstream WDM signal and to function as an optical coupler for a single upstream signal light is used.

That is, the optical access network system according to the present invention comprises a center device, a plurality of user devices each of which communicates with the center device by an optical signal, and a downlink from the center device. In the optical access network system including an optical circuit for distributing the optical signal to each user-side device and multiplexing the upstream optical signal from each user-side device and sending it to the center-side device, the downstream communication The communication in the upstream direction is performed by the same wavelength in each user device according to the wavelength assigned to each user device, and the optical circuit distributes the downstream optical signal for each wavelength, and the upstream optical signal. Is characterized by including a wavelength multiplexing / demultiplexing device for multiplexing.

As the wavelength multiplexer / demultiplexer, an array waveguide element formed using a quartz waveguide substrate can be used.

[0009]

FIG. 1 is a block diagram showing a first embodiment of the present invention. This optical access network system includes an OLT 1 as a center device,
Each of the ONUs 3-1 to 3-n is provided as a plurality of user-side devices, each of which communicates with the OLT 1 by an optical signal, and an optical circuit 2 that connects these ONUs 3-1 to 3-n is provided. The optical circuit 2 outputs a downstream optical signal from the OLT 1 to the ONU 3
-1 to 3-n, and multiplexes the upstream optical signals from the ONUs 3-1 to 3-n and sends out to the OLT 1. Here, downlink communication is performed by normal WDM, that is, ODM.
Wavelength λ assigned to each of NU3-1 to 3-n
This is performed by 1 to λn. On the other hand, upstream communication is performed by ONU3
-1 to 3-n are performed at the same wavelength λup. Therefore, the optical circuit 2 operates as a wavelength demultiplexer for distributing the downstream optical signal for each wavelength, and operates as an optical multiplexer (optical coupler) for multiplexing the upstream optical signal. I have.

[0010] The OLT 1 receives a signal from a center node device (telephone exchange, IP router, or the like).
A function of distributing and transmitting to U3-1 to 3-n and ONU
And a function of collecting signals from 3-1 to 3-n and outputting the signals to the node device. ONU3-1 to 3-n are O
A function of terminating the signal from the LT 1 and, if necessary, converting the signal into a format that can be received by the user terminal and relaying the signal;
1 has a function of relaying in an appropriate format.

FIG. 2 is a block diagram showing a configuration example of the optical circuit 2. As shown in FIG. Here, an example is shown in which individual components are combined. That is, the optical circuit includes a multiplexing / demultiplexing element 21 for multiplexing / demultiplexing light of wavelengths λ1 to λn and light of wavelength λup;
It comprises an optical coupler 22 having one input (output) port and one output (input) port, and an arrayed waveguide element 23. The array waveguide element 23 has a port Iin
WDMs of wavelengths λ1 to λn input from the ports O1 to On are individually output from ports O1 to On, respectively.
The wavelength of the wavelength λup input to the
To In. With this configuration, a downstream optical signal is input to the port In of the arrayed waveguide element 23 via the wavelength multiplexing / demultiplexing element 21, and is output from the ports O1 to On for each wavelength. On the other hand, the upstream optical signal is input from the ports O1 to On of the arrayed waveguide element 23 and output to the ports I1 to In, respectively.
2 and output through the multiplexing / demultiplexing element 21.

In general, an arrayed waveguide element has a structure in which waveguides having different lengths are arranged in an array, and is configured to output different wavelengths of light input to the same port to different ports, respectively. When light of the same wavelength is input to each port on the output side, there is a characteristic that light is output from separate ports. The optical circuit 2 shown in FIG. 2 utilizes the characteristics.

The multiplexing / demultiplexing device 21, the optical coupler 22, and the arrayed waveguide device 23 can be integrally formed on a single quartz substrate using PLC technology.

FIG. 3 is a block diagram showing another example of the configuration of the optical circuit 2. As shown in FIG. This optical circuit is composed of an multiplexing / demultiplexing element 21 for multiplexing / demultiplexing light of wavelengths λ1 to λn and light of wavelength λup, and an array waveguide in which an optical coupler 22 and an arrayed waveguide element 23 shown in FIG. And a wave path element 24. The array waveguide element 24 is a port I in the array waveguide element 23.
It is created by combining the parts 1 to In into one.
Also in this configuration, the multiplexing / demultiplexing device 21 and the arrayed waveguide device 24 can be integrated using the PLC technology.

FIG. 4 is a block diagram showing a second embodiment of the present invention. This optical access network system includes a center device 41 and a user device 43-1.
To 43-n and an optical circuit 42 for connecting them in a star shape.
And The center-side device 41 includes an ONU 44 of STM-PDS using the wavelength λup and a WDM of wavelengths λ1 to λn.
It comprises a WDM optical transmitter 45 for outputting signal light, and a wavelength demultiplexer 46 for separating and multiplexing the wavelength λup and the wavelengths λ1 to λn. The user-side devices 43-1 to 43-n each include a wavelength demultiplexer 47 that separates and multiplexes the wavelength λup and the wavelengths 1 to λn.
, An ONU 48 of STM-PDS, and an optical receiver 49 for receiving signal light of wavelengths 1 to λn.

The OLT 44 distributes a signal from a node device on the center side (telephone exchange, IP router, or the like) to designated user devices 43-1 to 43-n.
A function for outputting a signal to the optical receiver 49 via the optical transmitter 45 using a wavelength λup for the signal to the ONU 48;
And a function of collecting signals from the nodes and outputting the signals to the node device. The optical transmitter 45 transmits a WDM signal to the user-side devices 43-1 to 43-n according to an instruction from the OLT 45.
It has the function of sending out signals.

The ONU 48 terminates the signal from the OLT 44, converts it to a format that can be received by the user terminal if necessary, and relays the signal. Conversely, the ONU 48 converts the signal from the user terminal into an appropriate format. And a function of relaying to the OLT 44. The wavelength used by the ONU 48 is determined by the
-1 to 43-n have a common wavelength λup. The optical signal receiver 49 receives the WDM signal light having the wavelengths λ1 to λn from the center side and outputs the WDM signal light to the user side terminal in an appropriate signal format.

[0018]

As described above, according to the present invention,
In an access network of the WDM scheme, an ONU that requires more economic efficiency than an OLT can be configured at a low cost without sacrificing performance in the downlink direction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of an optical circuit.

FIG. 3 is a block diagram showing another configuration example of the optical circuit.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional example of an optical access network using the WDM technique.

[Explanation of symbols]

 1, 44, 51 OLT 2, 42 Optical circuit 3-1 to 3-n, 53-1 to 53-n, 48 ONU 21 Multiplexing / demultiplexing element 22 Optical coupler 23, 24 Array waveguide element 41 Center device 43- 1 to 43-n User side device 45 WDM optical transmitter 46, 47 wavelength demultiplexer 49 optical receiver 52 wavelength demultiplexer

Claims (2)

[Claims] 1. A center-side device, a plurality of user-side devices, each of which communicates with the center-side device by an optical signal, and a downstream-side optical signal from the center-side device, And an optical circuit for multiplexing an upstream optical signal from each user-side device and sending the multiplexed optical signal to the center-side device, wherein downlink communication is assigned to each user-side device. The user equipment performs the communication in the upstream direction at the same wavelength according to the assigned wavelength, and the optical circuit distributes the optical signal in the downstream direction for each wavelength, and the optical signal in the upstream direction is multiplexed. An optical access network system comprising a duplexer. 2. The optical access network system according to claim 1, wherein said wavelength multiplexer / demultiplexer includes an arrayed waveguide element formed using a quartz waveguide substrate.