KR20010037157A - Bi-directional, subcarrier-multiplexed self-healing ring optical network - Google Patents

Abstract

PURPOSE: A bidirectional self-cure ring type optical communication network of an SCMA(SubCarrier Multiple Access) system, is provided to configure a CBS(Central Base Station) and many ONUs(Optical Network Units) in a ring type using a single optical fiber, and to mount a pair of optical transceivers in the CBS and ONUs. So that an optical fiber can be saved when establishing an initial network and faults can be easily restored. CONSTITUTION: An optical communication network is configured by connecting a CBS(Central Base Station) and many ONUs(Optical Network Units) connected through an optical coupler(250) through a single optical fiber in a ring type. The CBS transmits downward signals to the ONUs by loading the downward signals on mutually different subcarriers, and processes upward signals received from the ONUs. The ONUs transmit upward signals to the CBS by loading the upward signals on inherent subcarriers. And the ONUs receive only signals loaded on the inherent subcarriers among downward signals transmitted from the CBS, and process the received signals. When errors are generated, signals are transmitted in an opposite direction to a transmission direction in a normal operation.

Description

Subcarrier multi-way bidirectional self-healing ring optical network {Bi-directional, subcarrier-multiplexed self-healing ring optical network}

The present invention relates to a subcarrier multiplex optical communication network, and more particularly, to a subcarrier multiplex bidirectional self-healing annular optical network capable of quickly recovering in the event of cutting of an optical fiber and a failure of a light source / optical receiver.

With the arrival of the information age, each subscriber's desire for information is increasing quantitatively and its types are diversifying. As high-speed, high-quality information services are required, and the scale of the subscriber system is expanded, the introduction of optical fiber in the subscriber network has brought economic and future prospects. However, as the evolution from the existing copper network to the fiber network requires a huge investment budget, it is very important to construct an economical network to reduce the investment cost and the efficiency of utilizing the optical subscriber network.

In this regard, passive optical networks, which are low in initial investment for network construction and easy to maintain, have attracted attention as economical optical subscriber networks. Passive optical subscriber networks share the optical fiber among several optical network units (ONUs), thereby saving the optical fiber and having the advantage of not having to provide a terminal device until the subscriber requires a specific service. In addition, since there is no device requiring an external power source between the central base station and the subscriber station, it is easy to maintain and maintain the network after installation. Passive optical subscriber network is expected to be activated further because it enables the construction of economical optical fiber network.

When one central base station is connected to a plurality of optical communication network units (ONU), such as a passive optical subscriber network, there are three main methods of communicating with the ONU.

The first is time division multiple access (TDMA), which divides the time so that a specific ONU and a central base station communicate at a specific time. With this approach, at any given time, the central base station communicates with any of the ONUs. Time division multiplexing has the advantage of relatively simple structure, but it has the disadvantage of not only low network security but also strict TDMA protocol, and it is difficult to evolve the network to improve performance.

The second method is wavelength division multiple access (WDMA), which allocates and transmits a wavelength for each ONU. The central base station shall have a light source of a wavelength corresponding to the number of ONUs, and each ONU shall have a light source of a specific wavelength. This method has the advantage of excellent security and easy performance, but has the disadvantage of requiring a light source allocated to the wavelength of the central base station and ONU.

The third method is subcarrier multiple access (SCMA). In the subcarrier multiplexing method, a user's signal on a subcarrier modulates a light source, and a signal of several users modulated by an optical signal is optically synthesized and transmitted. The receiver filters the signal on a subcarrier by using an RF filter. Will be distinguished. The subcarrier multiplexing method has a disadvantage in that optical beat interference occurs because several light sources are received by a single optical receiver, but does not require a strict TDMA protocol as in the time division multiplexing scheme described above. The advantage is that no light source is required. In addition, when configuring a wired / wireless complex access network using this technology, a wireless base station can be simply configured with only an opto-electric converter and an all-optical converter. Due to these advantages, subcarrier multiplex optical transmission systems for wired / wireless hybrid access networks have recently been in the spotlight.

However, due to the introduction of optical fiber into the subscriber network, the information volume of the subscriber is rapidly increasing, the problem recovery capability of the network is emerging as a new problem. In particular, in the case of a subscriber network in which multiple subscribers share one ONU, such as FTTC (Fiber to the Curb), multiple subscribers will suffer communication failures at the same time if a failure occurs, such as a fiber break or a failure of the ONU. This concern becomes even more realistic given the fact that fiber to the home (FTTH), where fiber optics are delivered to the subscriber's premises, is delaying deployment due to economic and track building issues and the emergence of alternatives such as FTTC. . In addition, the fact that the CATV network, which is currently commercialized, is interrupted by the problem that the service of all subscribers is interrupted when one cable is cut due to the network structure, shows how important the fault recovery capability of the subscriber network is.

Such a problem recovery problem of the network also occurs in a wired / wireless complex access network such as a PCS system currently commercialized. In general, the maximum number of subscribers that can be accommodated by a wireless base station in a wired / wireless hybrid access network varies from system to system but is about 100 to 300. This means that if there is a failure in the wireless base station, 100 to 300 subscribers will suffer from communication loss at the same time. In particular, in the case of a wired / wireless hybrid access network having a hand-off function, the failure of a specific wireless base station affects subscribers connected to neighboring wireless base stations.

Recently, a passive subcarrier multiplex optical transmission system has been proposed for a CDMA wired / wireless hybrid access network [H. Kim and Y. C. Chung, ″ Bi-directional passive optical network for CDMA PCS, ″ Electron. Lett., Vol. 35, no. 4, pp. 315-317, Feb. 1999]. The proposed system not only uses the double star structure but also has the advantage of saving the optical fiber when constructing the network because bidirectional transmission is performed using a single optical fiber. In addition, since the wireless base station can be economically implemented as a light emitting diode (LED), an optical receiver, and a frequency converter, it is possible to solve the economic problem caused by the size of the wireless cell. However, in such a system, many wireless base stations are connected to one optical fiber, and if a network failure occurs, many subscribers suffer from communication failure. For example, when eight wireless base stations are connected to one central base station, about 1,000 subscribers may simultaneously experience communication failure due to the cleavage of the optical fiber.

Accordingly, the present invention has been made to solve the above problems of the prior art, a central base station and a plurality of optical communication network unit is configured in a ring using a single optical fiber, a pair of optical to the central base station and optical communication network unit The purpose of this paper is to provide a subcarrier multi-way bidirectional self-healing annular optical network that can not only save the optical fiber in the initial network construction but also quickly recover from the breakage of the optical fiber and the failure of the light source / optical receiver. .

1 is a block diagram of a bidirectional self-healing annular optical communication network of a subcarrier multiplexing method according to an embodiment of the present invention

2 is an explanatory diagram showing a downlink signal spectrum of a central base station and an optical communication network unit of a subcarrier multiplex bidirectional self-healing annular optical communication network according to an embodiment of the present invention;

Figure 3 is a signal flow after failure recovery of the optical communication network according to an embodiment of the present invention when cutting the optical fiber

4 is a signal flow chart after failure recovery of an optical communication network according to an embodiment of the present invention when a failure of a light source or an optical receiver of an optical communication network unit occurs.

5 is a block diagram of a bidirectional self-healing annular optical communication network of a subcarrier multiple scheme according to another embodiment of the present invention

6 and 7 illustrate a case in which a subcarrier multiplex bidirectional self-healing ring optical communication network is applied to a wired / wireless hybrid access network according to the present invention.

Explanation of symbols on the main parts of the drawings

110, 120: optical transceiver of central base station

130: switch control device of the central base station

140, 150: frequency converter of the central base station

210, 220: Optical transceiver of optical communication network unit and wireless base station

230: switch control device of optical communication network unit

240 filter 250 optical coupler

260, 270: frequency converter of optical communication network unit

CBS: central base station MOD1, 2: modulator

DEM1, 2: demodulator LED: light emitting diode

WDM: Wavelength Division Multiplexer

DFB-LD: Distributed Feedback Laser Diode

SW1 to 3, 5 to 7: Electrical switch SW4: Optical switch

PD: Optical Receiver ONU: Optical Network Unit

RBS: Wireless Base Station

Embodiments of the present invention for achieving the object of the present invention as described above will be described in detail with reference to the accompanying drawings.

Example 1

1 is a block diagram of a bidirectional self-healing annular optical communication network according to an embodiment of the present invention.

As shown in the figure, in the optical communication network of this embodiment, one central base station (CBS) and a plurality of optical communication network units (ONU) are connected through an optical coupler 250 to form an annular structure, and the central base station (CBS) ) Includes a plurality of modulators (MOD1) for modulating information (electrical signals) of information sources on a subcarrier, and two optical transmitters (110, 120) provided with modulated signals of the modulator (MOD1). A plurality of electrical switches (SW1) for selectively supplying the signal, two adders (+) for adding the signals switched by the plurality of electrical switches (SW1) to the optical transmitters (110, 120), respectively, and the optical transmitters Switch control device 130 for controlling the state of the electrical switch (SW1) by determining the presence or absence of the up-signal converted to the electrical signal by (110, 120), and the electric power modulated during normal operation connected to the annular optical communication network Red light Transmits the optical signal to the optical communication network unit (ONU), and converts the optical signal received from the optical communication network unit (ONU) into an electrical signal and a normal operation optical receiver 110, and when connected to the annular optical network when a failure occurs The optical signal receiver 120 for disaster recovery which converts the modulated electrical signal into an optical signal and transmits the optical signal to an optical communication unit (ONU), and converts the optical signal received from the optical communication network unit (ONU) into an electrical signal. An adder (+) for adding the received signals output from the 110 and 120 to the plurality of demodulators DEM1, and a demodulator for demodulating the electrical signals transmitted from the adder (+) into a decodable signal (DEM1) It consists of.

The optical communication network unit ONU includes a modulator MOD2 for modulating information (electrical signals) of an information source on a subcarrier, and two optical transmitters 210 and 220 provided with modulated signals of the modulator MOD2. Electrical switch (SW2) to selectively supply and converts the electrical signal modulated in the normal operation to an optical signal to transfer to the central base station (CBS), and converts the optical signal received from the central base station (CBS) into an electrical signal The optical transceiver 210 for normal operation and a failure recovery that converts the modulated electrical signal into an optical signal when a failure occurs and transmits the optical signal to the central base station (CBS), and converts the optical signal received from the central base station (CBS) into an electrical signal. The optical transmitter 220, the electrical switch (SW3) for selectively outputting the received signal output from the optical transmitters (210, 220) to the filter 240, and the received signal output from the electrical switch (SW3) Phil A filter 240 for ringing, a demodulator DEM2 for demodulating the filtered signal into a decodable signal, and the presence or absence of a downlink signal converted into an electrical signal by the optical transceivers 210 and 220 determine the electrical switch ( A switch control device 230 for controlling the state of SW2, 3 and an optical coupler 250 for connecting the optical transmitters 210 and 220 to the optical fiber network.

In addition, the optical transceivers 110 and 120 of the central base station (CBS) are a 1.5 μm distributed feedback laser diode (LFD-LD) for converting a modulated electrical signal into an optical signal and an optical receiver for converting a received optical signal into an electrical signal. (PD) and a wavelength division multiplexer (WDM) for multiplexing the transmitted and received signals.

The optical transceivers 210 and 220 of the optical communication network unit (ONU) include a 1.3 μm light emitting diode (LED) for converting a modulated electrical signal into an optical signal and an optical receiver PD for converting a received optical signal into an electrical signal. And a wavelength division multiplexer (WDM) for multiplexing the transmitted and received signals.

The operation of the present embodiment having the above configuration will be described.

In this embodiment, in the optical communication network, a central base station (CBS) and a plurality of optical communication network units (ONU) are annularly connected using a single optical fiber. The central base station (CBS) uses subcarrier multiplexing to communicate with multiple optical communication network units (ONUs).

Accordingly, the central base station (CBS) carries signals on a frequency allocated to each optical communication network unit (ONU) and transmits them in a downlink line, and the optical communication network unit (ONU) corresponds to its own signal among the downlink signals transmitted from the central base station (CBS). The frequency signal to be filtered is received by the filter 240. 2 shows the downlink signal spectrum of the central base station and the optical network unit.

In addition, the central base station (CBS) and the optical communication network unit (ONU) are provided with two optical transceivers, respectively, for cutting the optical fiber and healing in the event of failure of the optical transceiver. One is a normal-acting optical transmitter and receiver 110 and 120 for normal operation, and the other is a recovery optical receiver and a receiver for failure recovery in case of failure of the optical fiber and the failure of the optical transmitter.

In the case of normal operation, the operation principle of up / down transmission will be described.

Looking at the operation principle from the downlink transmission from the central base station (CBS) to the optical communication network unit (ONU), during the normal operation, the central base station (CBS) transmits the downlink signal by using the optical transmitter 110 for normal operation.

That is, the downlink signal carried on the subcarrier by the modulator MOD1 is switched to the optical transceiver 110 for normal operation by the control of the electrical switch SW1 of the switch controller 130 and then the 1.5 μm DFB distribution feedback laser diode (DFB). -LD) is converted into an optical signal.

The downlink signal converted to the optical signal is transmitted along the downlink path clockwise through a wavelength division multiplexer (WDM), and then some signals are transmitted by the 2 ?? 2 optical coupler 250 of the optical network unit (ONU). Is received and processed by the optical communication network unit, and the remaining signals are transmitted to the next optical communication network unit.

The received downlink signal is converted into an electrical signal at the optical receiver PD through a wavelength division multiplexer WDM of the optical receiver 210 for normal operation.

During normal operation, since the electrical switch SW3 is connected to the optical transceiver 210 for normal operation by the control of the switch controller 230, the downlink signal converted into the electrical signal in the optical transmitter 210 for normal operation is electrically The switch SW3 is switched to the filter 240 so that only a signal corresponding to its own natural frequency is selected and then demodulated in the demodulator DEM2.

The uplink transmission from the optical network unit (ONU) to the central base station (CBS) is also similar to the downlink transmission. During normal operation, the electrical switch SW2 is connected to the optical transmitter 210 for normal operation under the control of the switch controller 230. Therefore, the uplink signal carried on the subcarrier by the modulator MOD2 of the optical communication network unit ONU is applied to the optical transceiver 210 for normal operation via the electrical switch SW2.

The electrical signal applied to the optical transmitter 210 for normal operation is converted into an optical signal in a 1.3-㎛ light emitting diode (LED) and transmitted in a counterclockwise direction of the optical path through the wavelength division multiplexer (WDM) and the optical coupler 250. Is received at the central base station (CBS).

In the case of uplink transmission, since the signal of several light sources enters one opto-electric converter, that is, the optical receiver PD, optical bit interference noise occurs. Optical bit interference noise is interference noise generated when several light sources of different wavelengths are incident on one optical receiver PD and are generated at a frequency position corresponding to a wavelength difference between light sources. Such optical bit interference noise can be greatly reduced by using a light source such as a wavelength-selected distributed feedback laser diode (DFB-LD) or a light emitting diode having a very wide line width. H. Kim, JM Cheong, C.- H. Lee, and Y. C. Chung, ″ Passive optical network for microcellular CDMA personal communication service, ″ IEEE Photon. Technol. Lett., Vol. 10, no. 11, pp. 1641-1643, Nov. 1998].

In particular, when a wavelength-selected distributed feedback laser diode is used as a light source for uplink transmission, if the wavelength difference between each light source is maintained over a predetermined interval (~ 0.2 nm), the signal quality due to optical bit interference noise in a signal band of about 2 GHz or less Deterioration is not observed. However, wavelength-selected distributed feedback laser diodes are expensive devices compared to other all-optical converters (fabric ferot lasers, light emitting diodes, etc.).

Therefore, when manufacturing a communication network unit using such a light source, not only can not be economically implemented, but the wavelength limitation condition of the distributed feedback laser diode has a disadvantage in that the initial installation and maintenance of the optical network unit is difficult.

On the contrary, since the light emitting diode has a wide line width and optical bit interference noise is generated over a very wide frequency range, the amount of interference noise generated in the signal band is relatively small and wavelength control is not required.

Therefore, as a light source of the optical network unit (ONU) of the present embodiment, a 1.3 μm light emitting diode was used to reduce optical beat interference (see R. D. Feldman, K.-Y. Liou, G. Raybon, and R. F. Austin, ″ Reduction of optical beat interference in a subcarrier multiple access passive optical network through the use of an amplified light-emitting diode, ″].

FIG. 3 illustrates how the optical communication network recovers when the optical fiber is cut, and shows the signal flow after failure recovery of the optical communication network when the optical fiber between ONU # 1 and ONU # 2 is cut.

Since the optical communication network of this embodiment transmits in both directions using a single optical fiber, the central base station (CBS) and the optical communication network unit (ONU) detect whether or not the optical fiber is cut by detecting the presence of an electrical signal received from the optical transceivers 210 and 220. You can judge.

For example, when the optical fiber between ONU # 1 and ONU # 2 is disconnected during normal operation, the central base station (CBS) cannot detect the uplink signal sent from ONU # 2, 3, 4, and ONU. # 2, 3, and 4 also cannot detect the downlink signal sent from the central base station (CBS). On the other hand, since there is nothing wrong with the optical fiber between the central base station (CBS) and ONU # 1, no change is detected in ONU # 1.

Therefore, when the optical fiber break occurs as shown in FIG. 3, since the uplink signals transmitted from the ONUs # 2, 3, and 4 are not detected by the optical transceiver 110 for normal operation of the central base station (CBS), the switch control of the central base station (CBS) is performed. The device 130 uses the signal member to operate the electrical switch SW1 to instruct the signals of the ONUs # 2, 3, and 4 to be transmitted and received through the optical transceiver 120 for disaster recovery.

In addition, in the case of ONU # 2, 3, 4, since the downlink signal of the central base station (CBS) is not detected in the normally operating optical transmitter, the switch controller 230 operates the electrical switches (SW2, 3) for failure recovery by using the same. The optical transmitter 220 transmits an uplink signal and receives a downlink signal.

Therefore, after failure recovery, the downlink signal of ONU # 1 is transmitted in the clockwise direction through the optical transmitter 110 for normal operation, and the uplink signal is transmitted in the counterclockwise direction. On the other hand, the down signals of the ONU # 2, 3, 4 are transmitted in the counterclockwise direction through the optical transmitter 120 for failure recovery, and the uplink signals are transmitted in the clockwise direction.

4 is a diagram illustrating how the optical communication network of the present embodiment recovers when a failure occurs in the optical transceiver of the optical communication network unit (ONU), and shows a case in which the normally operating optical transceiver 210 of the ONU # 2 has failed.

If the optical transceiver 210 of ONU # 2 fails during normal operation, the central base station (CBS) cannot detect the uplink signal sent from ONU # 2, and ONU # 2 receives the downlink signal from the central base station (CBS). It becomes undetectable. When such a failure occurs, the switch controller 130 of the central base station (CBS) operates the switch SW1 to transmit the downlink signal of the ONU # 2 in the counterclockwise direction through the optical transceiver 120 for failure recovery. In addition, the switch control unit 230 of the ONU # 2 also operates the switches SW2 and 3 to receive the downlink signal through the optical receiver 220 for fault recovery, and transmit the uplink signal in the clockwise direction.

Therefore, after failure recovery, the downlink signals of ONU # 1, 3, 4 are transmitted in the clockwise direction through the optical transceiver 110 for normal operation of the central base station (CBS), and the downlink signal of ONU # 2 is used for the error recovery optical transceiver ( 220 is transmitted in the counterclockwise direction. In the case of the ONU # 1, 3, and 4, the uplink signal is transmitted in the counterclockwise direction through the optical receiver 210 for normal operation, and the ONU # 2 is transmitted in the clockwise direction through the optical transmitter 220 for fault recovery.

Example 2

5 is a block diagram of a bi-directional multi-way self-healing annular optical communication network according to another embodiment of the present invention.

As shown in the figure, the configuration of the central base station 100 in the optical communication network of this embodiment is the same as that of the first embodiment, and the modulator (MOD2) that the optical communication network unit (ONU) carries information (electrical signal) of the information source on a subcarrier and modulates it. A light emitting diode (LED) converts a modulated electrical signal into an optical signal, an optical receiver (PD) converting an input optical signal into an electrical signal, and a wavelength division multiplexer (WDM) multiplexing an input / output signal. The optical transceiver 210, the optical switch SW4 for determining the up and down signals transmitted and received through the optical fiber network, the switch controller 230 for controlling the optical switch SW4, and the optical fiber network and the optical fiber. It consists of the optical coupler 250 which connects a communication network unit ONU.

In the present embodiment, the optical switch SW4 is used instead of the electrical switch in the optical communication network unit ONU, and only one optical transmitter is used. Accordingly, the self-healing annular optical communication network of the present embodiment can recover from itself in case of disconnection of the optical fiber, but the failure of the optical transceiver 210 of the optical communication network unit ONU cannot be automatically recovered.

However, since only a pair of optical transmitters and receivers are used for the optical communication network unit (ONU), there is an advantage that it can be economically implemented than the optical communication network of the above-described embodiment.

The operation of the optical communication network of this embodiment will be described below.

In the case of normal operation, the operation principle from the downlink transmission from the central base station (CBS) to the optical communication network unit (ONU) will be described. During the normal operation, the central base station (CBS) transmits the downlink signal by using the optical transceiver 110 for normal operation. . The downlink signal converted into the optical signal is transmitted along the optical path in a clockwise direction through a wavelength division multiplexer (WDM), and then some signals are transmitted by the optical coupler 250 of the optical network unit (ONU). It is received by the unit and the remaining signals are sent to the next optical network unit.

The downlink signal arriving at the optical communication network unit converts an electrical signal from the optical receiver PD through the wavelength division multiplexer WDM of the optical receiver 210 via the optical switch SW4. During normal operation, the optical switch SW4 is connected to receive only a downward signal transmitted in a clockwise direction by the control of the switch controller 230.

In addition, the uplink signal from the optical network unit (ONU) to the central base station (CBS) is converted into an electrical signal by the light emitting diode (LED), and then the wavelength division multiplexer (WDM), the optical switch (SW4) and the optical coupler 250 Is transmitted to the central base station (CBS) in the counterclockwise direction.

However, when the cleavage of the optical fiber occurs, the downlink signal transmitted from the central base station (CBS) is not detected in the optical communication network unit (ONU), so that the switch control device 230 of the optical communication network unit (ONU) receives electricity from the optical receiver PD. The absence of a signal is sensed and the connection state of the optical switch SW4 is switched using the signal.

In addition, the central base station (CBS) also recognizes the cleavage of the optical fiber by detecting the absence of an uplink signal transmitted from a specific optical communication network unit (ONU) using the optical transceivers 110 and 120, and uses the signal to switch the electrical switch (SW1). By changing the state of the) to transmit the downlink signal to the optical transmitter 120 for failure recovery. Therefore, the signal flow after the failover is as shown in FIG.

Example 3

FIG. 6 illustrates a case in which the self-healing annular optical communication network of Embodiment 1 is applied to a wired / wireless hybrid access network as a subcarrier multiplex bidirectional self-healing annular optical network according to another embodiment of the present invention. In the case of a wired / wireless hybrid access network, a radio base station (RBS) plays the role of an optical communication network unit in the first and second embodiments.

In this embodiment, one central base station (CBS) and a plurality of wireless base stations (RBS) are connected through a plurality of branch elements to form an annular structure, and the central base station (CBS) is a plurality of modulators for modulating a signal to be transmitted. (MOD), a plurality of transmitter side frequency converters (140) for converting a signal modulated by the modulator (MOD) into a frequency corresponding to a corresponding radio base station (RBS), and a frequency modulated signal by an optical transceiver A plurality of electrical switches (SW5) for selectively supplying to the 110, 120, and two adders (+) to add the signals switched by the plurality of electrical switches (SW5) to the optical transmitter (110, 120) And a switch control device 130 for determining the presence or absence of an uplink signal converted into an electrical signal by the optical transmitters 110 and 120 and controlling the state of the electrical switch SW5, and being connected to an annular optical communication network for normal operation. Stools during The optical signal is converted into an optical signal and transmitted to a radio base station (RBS), and the optical receiver 110 for normal operation for converting the optical signal received from the radio base station (RBS) into an electrical signal, and is connected to the annular optical communication network In the event of a failure, the modulated electrical signal is converted into an optical signal and transmitted to a radio base station (RBS), and an optical signal receiver 120 for failure recovery for converting an optical signal received from the radio base station (RBS) into an electrical signal, and the optical transmitter and receiver An adder (+) for adding the received signals converted into electrical signals at 110 and 120 and outputting them to the frequency converter 150, a plurality of receiving side frequency converters 150 for converting frequencies of the received signals, and the frequency converters ( And a plurality of demodulators DEM1 that demodulate the output of 150 into a decodable signal.

The radio base station RBS converts the frequency of the signal received through the antenna 1 ANT1, and transmits the output signal of the transmitting side frequency converter 260 to the optical transmitters 210 and 220. And an electrical switch (SW6) for selectively supplying the optical signal to the central base station (CBS) by converting the electrical signal received during normal operation into an optical signal, and converts the optical signal received from the central base station (CBS) into an electrical signal. The optical transceiver 210 for normal operation to convert, and converts the electrical signal input at the time of failure occurs to the optical signal to the central base station (CBS), and converts the optical signal received from the central base station (CBS) into an electrical signal Receiving side frequency converter to selectively recover the signal output from the optical transmitter and receiver 220, the optical coupler 250 for connecting the optical transceivers 210 and 220 to the optical fiber network, and the optical transceivers 210 and 220 260 road switch Switch control device 230 for controlling the state of the electrical switch (SW6, 7) by determining whether the electrical switch (SW7) and the down-signal converted to the electrical signal by the optical transceiver (210, 220) It consists of a receiving side frequency converter 270 for frequency converting the input signal and outputs through the antenna 2 (ANT2).

In addition, the optical transceivers 110 and 120 of the central base station (CBS) have the same configuration as in the first and second embodiments. That is, a 1.5 μm distributed feedback laser diode (DFB-LD) converts a modulated electrical signal into an optical signal, an optical receiver PD converting a received optical signal into an electrical signal, and a wavelength division multiplexing multiplexing a transmitted / received signal. It consists of a firearm (WDM).

The optical transceivers 210 and 220 of the radio base station RBS are the same as the optical transmitters of the optical communication network unit ONU of the first embodiment. That is, a 1.3 μm light emitting diode (LED) converting an input electrical signal into an optical signal, an optical receiver (PD) converting a received optical signal into an electrical signal, and a wavelength division multiplexer (WDM) multiplexing a transmitted / received signal. It is composed.

The optical communication network for the wired / wireless hybrid access network of the present embodiment having such a configuration is similar to the optical communication network of Embodiment 1 so that one central base station (CBS) can distinguish a plurality of wireless base stations (RBS). Each carrier uses a different frequency to communicate in subcarrier multiplexing.

To this end, frequency converters are installed in the central base station (CBS) and the radio base station (RBS), respectively. This is because the carrier frequency used in the wireless communication and the carrier frequency used in the optical communication network of the present invention do not need to be the same.

As such, when the frequency converters 140, 150, 260, and 270 are installed in the central base station (CBS) and the radio base station (RBS), the configuration of the central base station and the wireless base station becomes more complicated than those in the first and second embodiments described above. By assigning different frequencies for each base station (RBS), it is possible to distinguish the wireless base station (RBS) from the central base station (CBS). In addition, there is an advantage that the frequency requirements of the optical device and the electric device can be alleviated by using a frequency lower than the radio aerial frequency.

When the self-healing annular optical communication network of the present invention is applied to a wired / wireless hybrid access network, a frequency converter is required for the central base station and the wireless base station as described above, and the recovery procedure in the event of a failure is the same as described above.

Example 4

FIG. 7 illustrates a case in which the self-healing annular optical communication network of Embodiment 2 is applied to a wired / wireless hybrid access network as a subcarrier multiplex bidirectional self-healing annular optical communication network according to another embodiment of the present invention. In the present embodiment, in the wired / wireless hybrid access network, a radio base station (RBS) plays the role of the optical communication network unit in the first and second embodiments.

In this embodiment, one central base station (CBS) and a plurality of wireless base stations (RBS) are connected through a plurality of branch elements to form an annular structure, and the central base station (CBS) has the same configuration as that of the third embodiment.

The radio base station RBS converts the frequency of the signal received through the antenna 1 ANT1 and the output signal of the transmitting frequency converter 260 into an optical signal. Optical transceiver 210 for transmitting to the central base station (CBS), converting the optical signal received from the central base station (CBS) into an electrical signal, and the direction of progress of the up and down signals transmitted and received through the optical fiber network (clockwise or An optical switch SW4 for determining the counterclockwise direction, and a switch controller 230 for controlling the state of the optical switch SW4 by determining the presence or absence of a downlink signal converted into an electrical signal by the optical transmitter 210. And a receiving frequency converter 270 for frequency converting the electrical signal output from the optical transceiver 210 and outputting the same through the antenna 2 ANT2.

In the present embodiment having such a configuration, as in the third embodiment, since the first embodiment is applied to a wired / wireless hybrid access network, a frequency converter is required at the central base station and the wireless base station, and the recovery procedure in the event of a failure is the same as described above.

In another embodiment of the present invention, the optical transceivers 110 and 120 of the central base station (CBS) of the above-described embodiments may be configured with a 1.3-㎛ DFB laser, an optical receiver, and an optical coupler.

In another embodiment of the present invention, the optical transceivers 110 and 120 of the central base station (CBS) of the above-described embodiments may be configured with a 1.3-㎛ DFB laser, an optical receiver, and an optical coupler.

In another embodiment of the present invention, the optical transceivers 210 and 220 of the above-described embodiments of the optical communication network unit (ONU) or the wireless base station (RBS) may be configured as wavelength-selected DFB lasers, optical receivers, and wavelength division multiplexers. have.

As described above, the subcarrier multiplex self-healing annular optical communication network of the present invention has an effect of greatly improving the reliability of the network because it can be quickly recovered when the fiber is cut and the light source / optical receiver fails. In addition, since the optical communication network of the present invention is configured using a single optical fiber, not only the optical fiber is saved, but also a low-cost light emitting diode is used as the light source of the optical communication network unit, thereby greatly reducing the initial network construction cost.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (11)

An optical communication network is configured by annularly connecting a plurality of optical communication network units (ONU) connected through one central base station (CBS) and an optical coupler 250 to a single optical fiber, The central base station (CBS) transmits downlink signals on different subcarriers to a plurality of optical communication network units (ONU), and processes the uplink signals received by the plurality of optical communication network units (ONU), The plurality of optical communication network units (ONU) loads an uplink signal on a unique subcarrier and transmits the signal to the central base station (CBS), and receives and processes only a signal on its own subcarrier among downlink signals transmitted from the central base station (CBS). While In the event of a failure, the subcarrier multiplex bidirectional self-healing annular optical network characterized in that the reliability is improved by transmitting a signal in a direction different from the transmission direction (normal direction) during normal operation. The method of claim 1, The central base station (CBS) includes a plurality of modulators (MOD1) for modulating information (electrical signals) of information sources on subcarriers; A plurality of electrical switches (SW1) for selectively supplying two optical transmitters (110, 120) provided with the modulated signal of the modulator (MOD1); Two adders (+) for adding the signals switched by the plurality of electrical switches (SW1) to the optical transmitters (110, 120); A switch control device (130) for controlling the state of the electrical switch (SW1) by determining the presence or absence of an uplink signal converted into an electrical signal by two optical transmitters (110, 120); For normal operation, connected to the annular optical network, during operation, converts the modulated electrical signal into an optical signal and transmits it to the optical network unit (ONU), and converts the optical signal received from the optical network unit (ONU) into an electrical signal. An optical transmitter and receiver 110; Connected to the annular optical network, when a failure occurs, converts the modulated electrical signal into an optical signal and transmits it to the optical network unit (ONU), and recovers the error to convert the optical signal received from the optical network unit (ONU) into an electrical signal An optical transmitter and receiver 120; An adder (+) for adding the received signals output from the optical transmitters (110, 120) to a plurality of demodulators (DEM1); And a demodulator (DEM1) for demodulating the electrical signal transmitted from the adder (+) into readable information. The optical communication network unit (ONU) includes a modulator (MOD2) for carrying information on an information source (electric signal) on a carrier wave and modulating it; An electrical switch (SW2) for selectively supplying two optical transmitters (210, 220) provided with the modulated signal of the modulator (MOD2); In normal operation, the optical transceiver for normal operation converts the modulated electrical signal into an optical signal and transmits the optical signal to the central base station (CBS), and converts the optical signal received from the central base station (CBS) into an electrical signal; A failure recovery optical transmitter 220 converting the modulated electrical signal into an optical signal and transmitting the optical signal to a central base station CBS, and converting the optical signal received from the central base station CBS into an electrical signal; An electrical switch (SW3) for selectively supplying the received signal output from the optical transmitters (210, 210) to the filter (240); A filter 240 for filtering an electrical signal output from the electrical switch SW3; A demodulator (DEM2) for demodulating the filtered signal into decodable information; Switch control device 230 for controlling the state of the electrical switch (SW2, 3) by determining the presence or absence of the downlink signal converted into an electrical signal by the optical transceiver (210, 220) and the optical fiber network unit (ONU) Subcarrier multi-way bidirectional self-healing annular optical communication network, characterized in that it comprises an optical coupler (250) for connecting. The method of claim 1, The central base station (CBS) includes a plurality of modulators (MOD1) for modulating information (electrical signals) of information sources on subcarriers; A plurality of electrical switches (SW1) for selectively supplying two optical transmitters (110, 120) provided with the modulated signal of the modulator (MOD1); Two adders (+) for adding the signals switched by the plurality of electrical switches (SW1) to the optical transmitters (110, 120); A switch control device (130) for controlling the state of the electrical switch (SW1) by determining the presence or absence of an uplink signal converted into an electrical signal by two optical transmitters (110, 120); For normal operation, connected to the annular optical network, during operation, converts the modulated electrical signal into an optical signal and transmits it to the optical network unit (ONU), and converts the optical signal received from the optical network unit (ONU) into an electrical signal. An optical transmitter and receiver 110; Connected to the annular optical network, when a failure occurs, converts the modulated electrical signal into an optical signal and transmits the optical signal to the optical network unit (ONU), and recovers the fault to convert the optical signal received from the optical network unit (ONU) into an electrical signal An optical transmitter and receiver 120; An adder (+) for adding the received signals output from the optical transmitters (110, 120) to a plurality of demodulators (DEM1); And a demodulator (DEM1) for demodulating the electrical signal transmitted from the adder (+) into readable information. The optical communication network unit (ONU) includes a modulator (MOD2) which modulates information (electrical signals) of an information source on a subcarrier; An optical transceiver 210 for converting the modulated electrical signal into an optical signal and transmitting the optical signal to a central base station (CBS), and converting the optical signal received from the central base station (CBS) into an electrical signal; An optical switch (SW4) for determining a traveling direction (clockwise or counterclockwise) of the uplink signal and the downlink signal transmitted and received through the optical fiber network; A filter 240 for filtering an electrical signal output from the optical transceiver 210; A demodulator (DEM2) for demodulating the filtered signal into decodable information; A switch control device (230) for controlling the state of the optical switch (SW4) by determining the presence or absence of a downlink signal converted into an electrical signal by the optical transmitter (210); And an optical coupler (250) connecting the optical fiber network and the optical communication network unit (ONU). An optical communication network is configured by annularly connecting a plurality of wireless base stations (RBS) connected through one central base station (CBS) and an optical coupler 250 to a single optical fiber, The central base station (CBS) converts downlink signals to different frequencies and transmits them, and processes uplink signals received from a plurality of radio base stations (RBS), The plurality of radio base stations (RBS) converts an uplink signal to a natural frequency and transmits the signal, and receives and processes only a signal corresponding to its own frequency among downlink signals transmitted from the central base station (CBS), In the event of a failure, a subcarrier multi-way bidirectional self-healing annular optical communication network for a wired / wireless hybrid access network, characterized in that reliability is improved by transmitting a signal in a direction different from the transmission direction in normal operation (counter direction). The method of claim 4, wherein The central base station (CBS) includes a plurality of modulators (MOD1) for carrying and modulating information of an information source on a carrier frequency; A transmitter side frequency converter (140) for converting a signal modulated by the modulator (MOD1) to a frequency corresponding to a corresponding radio base station (RBS); A plurality of electrical switches SW5 for selectively supplying a frequency modulated signal to the optical transmitters 110 and 120; Two adders (+) for adding the signals switched by the plurality of electrical switches (SW5) to the optical transmitters (110, 120); A switch control device (130) for controlling the state of the electrical switch (SW5) by determining the presence or absence of an uplink signal converted into an electrical signal by the optical transmitter (110, 120); An optical transceiver for normal operation connected to an annular optical network to convert an electrical signal modulated during normal operation into an optical signal for transmission to a radio base station (RBS), and converts an optical signal received from the radio base station (RBS) into an electrical signal ( 110); Error recovery optical transmitter 120 connected to an annular optical network to convert an electrical signal modulated in the event of a failure to an optical signal to a radio base station (RBS), and converts the optical signal received from the radio base station (RBS) into an electrical signal (120) )Wow; A plurality of receiving side frequency converters 150 for converting frequencies of the received signals converted into electrical signals; And a plurality of demodulators DEM1 demodulating the output of the frequency converter 150, The radio base station (RBS) includes a transmitting frequency converter (260) for converting a frequency of a signal received through the antenna 1 (ANT1); A switch (SW6) for selectively supplying the output signal of the transmitting frequency converter (260) to the optical transmitter (210, 220); An optical transmitter 210 for normal operation, which converts an electrical signal received during normal operation into an optical signal and transmits the optical signal to a central base station CBS, and converts the optical signal received from the central base station CBS into an electrical signal; An error recovery optical transmitter 220 for converting an electrical signal into an optical signal and transmitting the electrical signal to a central base station CBS, and converting an optical signal received from the central base station CBS into an electrical signal; An optical coupler 250 for connecting the optical transmitters 210 and 220 to the optical fiber network; A switch (SW7) for selectively switching the signal output from the optical transceiver (210, 220) to a receiving side frequency converter (260); A switch control device (230) for controlling the state of the electrical switches (SW6, 7) by determining the presence or absence of a downlink signal converted into an electrical signal by the optical transceiver (210, 220); And a receiving side frequency converter 270 for frequency converting the electrical signal output from the optical transmitters 210 and 220 and outputting the same through antenna 2 ANT2. Subcarrier multi-way bidirectional self-healing annular optical network. The method of claim 4, wherein The central base station (CBS) includes a plurality of modulators (MOD1) for carrying and modulating information of an information source on a carrier frequency; A transmitter side frequency converter (140) for converting a signal modulated by the modulator (MOD1) to a frequency corresponding to a corresponding radio base station (RBS); A plurality of electrical switches SW5 for selectively supplying a frequency modulated signal to the optical transmitters 110 and 120; Two adders (+) for adding the signals switched by the plurality of electrical switches (SW5) to the optical transmitters (110, 120); A switch control device (130) for controlling the state of the electrical switch (SW5) by determining the presence or absence of an uplink signal converted into an electrical signal by the optical transmitter (110, 120); An optical transceiver for normal operation connected to an annular optical network to convert an electrical signal modulated during normal operation into an optical signal for transmission to a radio base station (RBS), and converts an optical signal received from the radio base station (RBS) into an electrical signal ( 110); Error recovery optical transmitter 120 connected to an annular optical network to convert an electrical signal modulated in the event of a failure to an optical signal to a radio base station (RBS), and converts the optical signal received from the radio base station (RBS) into an electrical signal (120) )Wow; A plurality of receiving side frequency converters 150 for converting frequencies of the received signals converted into electrical signals; And a plurality of demodulators DEM1 demodulating the output of the frequency converter 150, The radio base station (RBS) includes a transmitting frequency converter (260) for converting a frequency of a signal received through the antenna 1 (ANT1); An optical transceiver 210 for converting an output signal of the transmitting frequency converter 260 into an optical signal and transmitting the optical signal to a central base station (CBS), and converting an optical signal received from the central base station (CBS) into an electrical signal; An optical switch (SW4) for determining a traveling direction (clockwise or counterclockwise) of the uplink signal and the downlink signal transmitted and received through the optical fiber network; A switch control device (230) for controlling the state of the optical switch (SW4) by determining the presence or absence of a downlink signal converted into an electrical signal by the optical transmitter (210); And a receiving side frequency converter 270 which frequency-converts the electrical signal output from the optical transceiver 210 and outputs the same through the antenna 2 ANT2. Multi-way bidirectional self-healing annular optical network. The method according to any one of claims 2, 3, 5, and 6, A 1.55-μm DFB laser diode converting an electrical signal to be transmitted by the optical transmitters and receivers 110 and 120 of the central base station (CBS); An optical carrier for converting a received optical signal into an electrical signal, and a wavelength division multiplexer. The method according to any one of claims 2, 3, 5, and 6, And a 1.3-μm DFB laser for converting the electrical signal to be transmitted by the optical transmitters 110 and 120 of the central base station (CBS), the optical receiver for converting the received optical signal into an electrical signal, and an optical coupler. A subcarrier multi-way bidirectional self-healing annular optical network. The method according to any one of claims 2, 3, 5, and 6, 1.3-μm Fabry-Perot laser to convert the electrical signal to be transmitted by the optical transmitters 110 and 120 of the central base station (CBS) to an optical signal, an optical receiver to convert the received optical signal into an electrical signal, and an optical coupler Subcarrier multi-way bidirectional self-healing annular optical network, characterized in that configured. The method according to any one of claims 2, 3, 5, and 6, 1.3 μm light emitting diodes (LEDs) for converting the electrical signals to be transmitted by the optical transceivers 210 and 220 of the optical communication network unit ONU or the radio base station RBS, and converting the received optical signals into electrical signals. A subcarrier multiplex bidirectional self-healing annular optical network comprising an optical receiver and a wavelength division multiplexer The method according to any one of claims 2, 3, 5, and 6, A wavelength-selected DFB laser for converting an electrical signal to be transmitted by the optical transceivers 210 and 220 of the optical communication network unit ONU or a radio base station RBS, an optical receiver for converting the received optical signal into an electrical signal; And a subcarrier multiplex bidirectional self-healing annular optical communication network, comprising: a wavelength division multiplexer.