KR20050067873A - Wdm pon system appointed an optical circulator - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission system employing a WDM (Wavelength Division Multiplexing) system, and more particularly to a WDM PON system employing a optical circulator. In the optical transmission system employing the WDM scheme according to the embodiment of the present invention,

A plurality of optical transmitters for generating optical signals of different wavelengths; A plurality of optical receivers for receiving optical signals of the same wavelength as the pair of optical transmitters paired with the optical transmitter and converting the received optical signals into electrical signals; A multiplexer / demultiplexer for multiplexing optical signals having different wavelengths inputted thereto and outputting the optical signals to an optical communication line, demultiplexing the multiplexed optical signals input through the optical communication line, and outputting the demultiplexed optical signals; And a plurality of optical circulators for outputting the optical signal output from the designated optical transmission unit to the multiplexer / demultiplexer and for demultiplexing the optical signal input from the multiplexer / demultiplexer to output the inputted optical signal to the designated optical receiver unit .

Description

(WDM PON SYSTEM APPOINTED AN OPTICAL CIRCULATOR)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission system employing a WDM (Wavelength Division Multiplexing) system, and more particularly to a WDM PON system employing a optical circulator.

Wavelength division multiplexing (WDM) is a method in which a central office (CO) allocates different wavelengths to each subscriber and transmits data at the same time. Each subscriber always transmits / receives data using the allocated wavelength . This scheme not only can transmit a large amount of data to each subscriber, but also has an advantage of excellent communication security and easy performance improvement.

On the other hand, PON (Passive Optical Network) is one of the optical subscriber network establishment method, which allows optical line termination (OLT) to connect multiple optical network units (OLTs) by using passive optical distribution elements in optical cables. The PON is transmitted from CO to a remote node (RN) through a single optical fiber, and is divided into a passive optical distribution element in the RN, and each subscriber is transmitted to the optical fiber. In other words, since the PON is a single optical fiber connected to a local base station (RN) installed in a neighboring area of the subscribers in the CO, and the individual optical fiber is connected from the RN to each subscriber, the optical cable is installed one by one from the CO to the subscriber It is possible to reduce the cable cost relatively.

The WDM PON system described above can be combined into a ring type WDM PON system. Such a ring type WDM PON system is generally used for a fiber switching, a specific channel LD (corresponding to the optical transmitter) or PD (corresponding to the optical receiver) The redundancy structure is adopted to prepare for the failure.

An example of a ring-type WDM PON system employing a redundancy structure is shown in Fig. As shown in FIG. 1, in order to realize general redundancy, the central office (CO) (LD1, LD2, PD1, PD2) with respect to the transmitting / receiving unit (LD1, LD2, PD1, PD2). The optical transmission and reception units LD1 and PD1 for the steady state for each wavelength are connected to one multiplexer / demultiplexer MUX1, and the other optical transmission / reception units LD2 and PD2 for redundancy are connected to another multiplexer / / Demultiplexer (MUX2).

In the above structure, each multiplexer / demultiplexer (MUX1, MUX2) in the central office (CO) multiplexes several different wavelengths generated from the N optical transmitters (LD1, LD2) RN2, ..., RNn, or demultiplexes signals multiplexed and received from the local base station RN and transmits the demultiplexed signals to the optical reception units PD1, PD2.

On the other hand, a 3-dB optical coupler is coupled between each of the pair of optical transmission / reception units LD and PD and the multiplexers / demultiplexers MUX1 and MUX2. The 3-dB optical coupler operates as a kind of splitter that distributes the demultiplexed optical signal from the multiplexer / demultiplexer (MUX1, MUX2) to the optical transmitter (LD) and the optical receiver (PD).

In the ring type WDM PON system as described above, light generated from the LD, which is a light source, is circulated through the ring and transmitted to the 3 dB optical coupler through the multiplexers / demultiplexers (MUX1 and MUX2) of the central base station (CO) The light is also transmitted to the LD, which is the light source of the optocoupler.

As the unwanted light component enters the LD as a light source, the characteristics of the light source are affected. Particularly, when a wavelength equal to the wavelength of emitted light is introduced through the optical coupler, the bandwidth of the light source is widened, so that the data transmission rate of the entire system is lowered or the lifetime of the light source is shortened. . This problem is remarkable in data transmission at a higher speed (1 Gbps or more) than at low speed (155 Mbps). Using a model with an optical isolator in the light source can solve some of the problems described above, but this is not a desirable solution because of the problem of rising system construction costs.

Further, in a central office (CO) of a general ring type WDM PON system, a plurality of light sources (LD) are provided as means for generating different wavelengths. If multiple wavelengths can be used as one light source, the system construction cost can be reduced by reducing the number of light sources (LD), and the driving power of the light source (LD) can be reduced.

Accordingly, it is an object of the present invention to provide a WDM PON system capable of reducing the transmission error rate of a data packet as well as extending the lifetime of a light source by originally blocking light that can enter the light source.

It is still another object of the present invention to provide a WDM PON system which can reduce system construction cost and reduce light source driving power by generating and using multiple wavelengths as one light source.

According to an aspect of the present invention, there is provided an optical transmission system employing a WDM scheme,

A plurality of optical transmitters for generating optical signals of different wavelengths;

A plurality of optical receivers for receiving optical signals of the same wavelength as the pair of optical transmitters paired with the optical transmitter and converting the received optical signals into electrical signals;

A multiplexer / demultiplexer for multiplexing optical signals having different wavelengths inputted thereto and outputting the optical signals to an optical communication line, demultiplexing the multiplexed optical signals input through the optical communication line, and outputting the demultiplexed optical signals;

And a plurality of optical circulators for outputting the optical signal output from the designated optical transmission unit to the multiplexer / demultiplexer and for demultiplexing the optical signal input from the multiplexer / demultiplexer to output the inputted optical signal to the designated optical receiver unit .

Further, in the optical transmission system employing the WDM scheme according to another embodiment of the present invention,

An optical transmitter for generating a broadband optical signal;

A grating device for generating optical signals of different wavelengths from the broadband optical signal;

A plurality of optical receivers for receiving an optical signal and converting the optical signal into an electrical signal;

A multiplexer / demultiplexer for multiplexing optical signals having different wavelengths inputted thereto and outputting the optical signals to an optical communication line, demultiplexing the multiplexed optical signals input through the optical communication line, and outputting the demultiplexed optical signals;

A plurality of optical circulators for receiving optical signals of different wavelengths generated in the grating device and outputting the optical signals to the multiplexer / demultiplexer, demultiplexing the input optical signals and outputting the demultiplexed optical signals to a designated optical receiver; .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

2 is a block diagram of a ring type WDM PON system as an example of an optical transmission system employing an optical circulator 100 according to an embodiment of the present invention. 100 shown in FIG.

2, a ring type WDM PON system according to an embodiment of the present invention includes a central office (CO), a plurality of local base stations 130 connected to the central office (CO) through an optical communication line 120 ).

The central office (CO) includes a plurality of optical transmitters (LDs) for generating optical signals of different wavelengths, and a plurality of optical transmitters (LDs) paired and paired with the optical transmitters And a plurality of light receiving units (PDs) for receiving an optical signal and converting the optical signal into an electrical signal.

The central office (CO) multiplexes optical signals of different wavelengths inputted through the optical circulators 100 to be described later and outputs the multiplexed optical signals to the optical communication line 120. The multiplexed optical signals, which are input through the optical communication line 120, And a multiplexer / demultiplexer (MUX / DEMUX) 110 for demultiplexing the optical signals and outputting the demultiplexed optical signals to optical circulators 100 to be described later.

In addition, the central office (CO) outputs an optical signal output from a designated optical transmission unit (LD) among the plurality of optical transmission units 100 to the multiplexer / demultiplexer 110, multiplexes / demultiplexes the multiplexed / And a plurality of optical circulators 100 for outputting an optical signal demultiplexed and input to the optical receiver PD again.

The optical circulator 100 is an optical device designed so that light incident through the input port can never be returned to the same port. This means that the light from the light source does not flow back into the light source even if it is routed through any path. This optical circulator 100 is shown in Fig. 3, an optical signal input through port 1 is output through port 2, and an optical signal input through port 2 is output through port 3. [ The connection between port 3 and port 1 is not available.

Therefore, if the port 1 is connected to the optical transmitter LD and the port 2 and the port 3 are connected to the multiplexer / demultiplexer 110 and the optical receiver PD, respectively, 2 multiplexed by the multiplexer / demultiplexer 110 and transmitted to the local base stations 130 through the optical communication line 120. The optical signals circulated through the ring-type optical communication line 120 are multiplexed / Demultiplexed by the neutralizer 110, and then inputted to the port 2 of each optical circulator 100, each optical receiver PD receives the optical signal through the port 3. At this time, since the optical signal inputted through the port 2 can not be returned to the port 1 and is output through the port 3 only, there is no phenomenon that the optical signal flows into the light source like the conventional 3 dB coupler.

Therefore, packet transmission error does not occur even at a low speed as well as a high-speed data transmission.

The local base stations 130 are connected to the optical communication line 120 by a signal having a wavelength of a specific band among the optical signals transmitted through the optical communication line 120, And outputs the optical signal transmitted from the subscriber unit side to the optical communication line 120. The optical branching / Since the optical branch / coupler is a known technique in the WDM PON system, detailed description thereof will be omitted.

Each local base station 130 outputs the optical signal dropped through the optical add / drop multiplexer to the optical receiver PD of the subscriber unit, and transmits the optical signal input from the optical transmitter LD of the subscriber unit to the optical branch And outputting it to the optical coupler / coupler. Since the optical circulator 100 also operates with the structure shown in FIG. 3, it is possible to prevent the optical signal from entering the optical transmission unit LD of each subscriber unit in advance.

In the local base station 130 shown in FIG. 2, there are two optical circulators 100, one of which is a redundant optical circulator. The redundancy concept is for system recovery in a ring type WDM PON system, which is also well known, and a detailed description thereof will be omitted.

Meanwhile, the central office (CO) of the WDM PON system includes a plurality of optical transmitters (LDs) as means for generating different wavelengths. If multiple wavelengths can be used as one light source, it is possible to reduce the system construction cost due to the reduction in the number of light sources (LD) and reduce the driving power of the light source (LD). To this end, in the embodiment of the present invention, a grating device capable of generating multiple wavelengths with only one light source has been introduced. This will be described in detail with reference to FIG. 4,

4 is a view for explaining a process of separating a plurality of wavelengths from one light source LD according to an embodiment of the present invention.

Referring to FIG. 4, in order to separate multiple wavelengths from one light source, a light source having a wide bandwidth must be used. That is, a light source that is one optical transmission unit (LD) generates and outputs a wideband optical signal. The broadband optical signal generated by the optical transmission unit LD is incident on the grating device 115 as shown in FIG. The grating device 115 is an optical device that filters and passes only wavelength components having the same interval as the grating period with respect to incident light, and as a result, generates optical signals of different wavelengths from the broadband optical signal .

The optical signals of different wavelengths generated by the grating device 115 are incident on the port 1 of the optical circulators 100 positioned in front of or behind the grating device 115, 3, and can be input to the multiplexer / demultiplexer 120 through the port 2 as shown in FIG.

On the contrary, the optical signals of different wavelengths demultiplexed by the multiplexer / demultiplexer 120 are inputted to the port 3 of each of the optical circulators 100 and are transmitted to the optical receiver (not shown) The received optical signal can be converted into an electrical signal and output.

When a grating device that generates optical signals of different wavelengths from one light source that generates a broadband optical signal and light emitted from the light source is used, optical signals of different wavelengths are generated without using various light sources Therefore, the system construction cost can be reduced as a result, and the power consumption can be saved by driving the light source.

5 is a block diagram of a ring type WDM PON system employing a light circulator according to another embodiment of the present invention. More specifically, the ring type WDM PON system Fig.

Referring to FIG. 5, the ring WDM PON system includes a central base station, a local base station, and an optical coupler.

The central office includes a plurality of optical transmission units (TX: LD) for generating optical signals of different wavelengths, an optical transmission unit (TX) paired with the optical transmission units (TX) (General MC) including a plurality of light receiving units (corresponding to RX: PD) for receiving a signal and converting and outputting the signal into an electric signal, and a light source A multiplexer / demultiplexer 140 for demultiplexing the signals and outputting them to the outside, demultiplexing the multiplexed signals inputted from the outside, and outputting the demultiplexed signals to the converters; and a multiplexer / demultiplexer 140 for multiplexing / And a plurality of optical circulators (100) connected between the input ports and outputting the inputted optical signals to a designated port.

The optical coupler 150 branches the multiplexed signal output from the multiplexer / demultiplexer 140 to different optical communication lines, and multiplexes the optical signal transmitted from any one of the optical communication lines to the multiplexer / And transmits it to the localizer 140. The reason for distributing the output of the central office (CO) to the two paths through the optical coupler 150 is to prevent redundancy of the optical transmission unit (LD) and the optical reception unit (PD) .

On the other hand, the optical communication fiber forms a ring-shaped distribution network through the bidirectional optical branching / combining devices 170, and each bidirectional optical branching / combining device 170 detects the line switching state, The WDM PON system includes local base stations combined with a redundant media converter 160 for transmitting optical signals. The redundant media converter 160 may be connected to the subscriber device via a direct or Ethernet network.

For reference, the bidirectional optical add / drop multiplexer 170 has a signal flow in opposite directions between the first and second optical transmission lines on both sides of the ring, and as shown in FIG. 6, (Com IN Prot), the wavelength of a specific band ) Signal to the master channel of the redundant media converter 160 to be described later, and outputs the same wavelength A first WDM thin film filter for receiving a signal from the master channel and reflecting the signal to the first optical communication line; And the wavelength of the specific band among the signals input from the second optical communication line connected to another input port (Com out Port) ) Signal to a slave channel of a redundant media converter 160 to be described later, and receives a signal of the same wavelength as the dropped signal from the slave channel and reflects the signal to the second optical communication line do.

By this bidirectional optical add / drop multiplexer 170, the RN can transmit the optical signal transmitted from the subscriber unit in a clockwise or counterclockwise direction in a ring-type distribution network.

7, the redundant media converter 160 includes an optical transmitter / receiver unit of a master channel, an optical transmitter / receiver unit of a slave channel and a CPU 186, And PHY chips 185 and 195 serving as interfaces.

The optical circulator 100 shown in FIG. 3 is connected to each of the master channel and the slave channel. The optical circulator 100 may be included in the media converter 160 or may be located externally. It can be assumed that the master channel is connected to a drop port of the bidirectional optical add / drop multiplexer 170 shown in FIG. 6 (an add port in the case of an upward signal), and the slave channel is assumed to be a bidirectional It can be assumed that it is connected to the add port of the optical add / drop multiplexer 170.

According to this assumption, the optical signal transmitted through the drop port and the master channel is input to the PD 183 which is the optical receiver of the master channel by the optical circulator 100, and the optical signal transmitted from the LD 181 The optical signal is transmitted to the central office (CO) through the optical circulator (100) and the drop port of the bidirectional optical add / drop multiplexer (170).

The optical transmitting and receiving unit of the master channel and the optical transmitting and receiving unit of the slave channel each include an LD 181 and 193 as light sources and LD driving units 182 and 194 for driving the same and PDs 183 and 191 and PD driving units 184 and 192 as optical receiving units .

The master / slave optical transceiver unit generates an optical signal and transmits the optical signal to the optical circulator 100 through the optical circulator 100. The master / slave optical transceiver unit converts the optical signal transmitted through the optical circulator 100 into an electrical signal, And outputs it to the subscriber unit through the subscriber units 185 and 195.

The CPU 186 controls the overall operation of the media converter 160. For example, the CPU 186 detects the state of the master and slave optical transceivers and the circuit switching state based on the control program data stored in the internal memory, thereby activating only one of the master and slave optical transceivers .

Lastly, the media converter 160 according to the embodiment of the present invention further includes an interface unit 185, 195 connected to each of the master and slave optical transceivers to perform data interfacing with the subscriber unit. A PHY chip can be used as these interface units 185 and 195. For reference, the interface unit 195 connected to the slave optical transmitter / receiver unit may further include a buffer 187 for buffering data.

For reference, the circuit switching process performed by the CPU 186 is described in detail in a " ring-type WDM PON system with up-and-down equal wavelengths including an incandescent-type media converter " filed by the present applicant, The gist of the present invention may be unnecessarily obscured and a detailed description thereof will be omitted.

In consideration of the central base station C of the ring-type WDM PON system having the same wavelength as the up-and-down directional wavelength converter 160 having the above-described configuration, each media converter (General MC) of the central station C Since the optical circulator 100 is connected between the multiplexer / demultiplexer 140, the demultiplexed optical signal like the conventional 3 dB coupler is not re-introduced into the light source TX.

Also, since the optical transmission / reception unit of the master or the slave is connected to the optical circulator 100 in each local base station, the optical signal inputted through the bidirectional optical add / drop multiplexer 170 is not introduced into the light source LD .

Therefore, even in the ring type WDM PON system of the same wavelength including up and down media converter 160, the probability of occurrence of packet transmission error during low-speed as well as high-speed data transmission is low.

As described above, according to the present invention, light that can be introduced into a light source is originally blocked, thereby extending the lifetime of the light source and lowering the transmission error rate of a data packet.

Furthermore, since the present invention generates and uses a plurality of wavelengths as one light source, the system construction cost can be reduced, and the light source driving power can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a ring type WDM PON system having the same wavelength in up and down direction. FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a ring type WDM PON system employing a light circulator,

3 is a diagram illustrating an example of the port configuration of the optical circulator 100 in FIG.

4 is a view illustrating a process of separating a plurality of wavelengths from one light source according to an embodiment of the present invention.

5 is a block diagram of a ring type WDM PON system employing a light circulator according to another embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration example of the bidirectional optical add / drop multiplexer 170 in FIG.

FIG. 7 is a detailed configuration diagram of a media type media converter 160 for redundancy in FIG. 5; FIG.

Claims (8)

In an optical transmission system employing a wavelength division multiplexing method, A plurality of optical transmitters for generating optical signals of different wavelengths; A plurality of optical receivers for receiving optical signals of the same wavelength as the pair of optical transmitters paired with the optical transmitter and converting the received optical signals into electrical signals; A multiplexer / demultiplexer for multiplexing optical signals having different wavelengths inputted thereto and outputting the optical signals to an optical communication line, demultiplexing the multiplexed optical signals input through the optical communication line, and outputting the demultiplexed optical signals; And a plurality of optical circulators for outputting the optical signals output from the designated optical transmission unit to the multiplexer / demultiplexer and for demultiplexing the optical signals input from the multiplexer / demultiplexer to output the inputted optical signals to the specified optical receiver unit WDM PON system. The system of claim 1, further comprising: local base stations connected to the optical communication line, each local base station comprising: An optical branching / combining unit for dropping only a signal having a wavelength of a specific band among the optical signals transmitted through the optical communication line and outputting the signal to the subscriber unit side and outputting the optical signal transmitted from the subscriber unit side to the optical communication line; And an optical circulator outputting the optical signal dropped through the optical add / drop multiplexer to the optical receiver of the subscriber unit and outputting the optical signal input from the optical transmitter of the subscriber unit to the optical add / drop multiplexer. WDM PON system. The WDM PON system of claim 2, further comprising a light circulator for redundancy between the optical branch / coupler and the subscriber unit. In an optical transmission system employing a wavelength division multiplexing method, An optical transmitter for generating a broadband optical signal; A grating device for generating optical signals of different wavelengths from the broadband optical signal; A plurality of optical receivers for receiving an optical signal and converting the optical signal into an electrical signal; A multiplexer / demultiplexer for multiplexing optical signals having different wavelengths inputted thereto and outputting the optical signals to an optical communication line, demultiplexing the multiplexed optical signals input through the optical communication line, and outputting the demultiplexed optical signals; A plurality of optical circulators for receiving optical signals of different wavelengths generated in the grating device and outputting the optical signals to the multiplexer / demultiplexer, demultiplexing the input optical signals and outputting the demultiplexed optical signals to a designated optical receiver; Wherein the WDM PON system comprises: 5. The apparatus of claim 4, further comprising: local base stations connected to the optical communication line, each local base station comprising: An optical branching / combining unit for dropping only a signal having a wavelength of a specific band among the optical signals transmitted through the optical communication line and outputting the signal to the subscriber unit side and outputting the optical signal transmitted from the subscriber unit side to the optical communication line; And an optical circulator outputting the optical signal dropped through the optical add / drop multiplexer to the optical receiver of the subscriber unit and outputting the optical signal input from the optical transmitter of the subscriber unit to the optical add / drop multiplexer. WDM PON system. The WDM PON system of claim 5, further comprising a light circulator for redundancy between the optical branch / coupler and the subscriber unit. A plurality of optical transmitters for generating optical signals of different wavelengths and a plurality of optical receivers for receiving optical signals of the same wavelength and converting and outputting the optical signals into electrical signals in a pair of optical transmitters paired with the optical transmitters A multiplexer / demultiplexer for multiplexing optical signals of different wavelengths generated in each of the media converters and outputting them to the outside, demultiplexing the multiplexed signals inputted from the outside, and outputting the demultiplexed signals to the converters; And a plurality of optical circulators connected between the media converter and the multiplexer / demultiplexer for outputting optical signals to the designated port; An optical coupler for branching the multiplexed signals output from the multiplexer / demultiplexer to different optical communication lines and transmitting the optical signals transmitted from any one of the optical communication lines to the multiplexer / demultiplexer; The bidirectional optical add / drop multiplexer / demultiplexer / demultiplexer / multiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / demultiplexer / And a local base station to which a media converter is coupled. 8. The apparatus of claim 7, wherein the redundant media converter comprises: First and second optical circulators connected to the master channel and the slave channel, respectively; A master and a slave optical transmitting / receiving unit for generating and transmitting optical signals to any one of the first and second optical circulators, converting an optical signal transmitted through the optical circulator to an electrical signal, and outputting the electrical signals to the subscriber unit; A controller for detecting a state of the master and slave optical transceivers and a circuit switching state to activate only one of the optical transceivers; And an interface unit connected to each of the master and slave optical transmission / reception units and performing data interfacing with the subscriber unit.