KR20040013405A - Wavelength division multiplexing-passive optical network using same wavelength as upstream and downstream chanel - Google Patents

Abstract

PURPOSE: A WDM(Wavelength Division Multiplexing) PON(Passive Optical Network) system whose upper and lower channels have the same wavelength is provided to transceive data with the same wavelength by channel, and to use a low-priced Fabry-Perot laser diode as a light source of a central office and an ONU(Optical Network Unit), thereby efficiently implementing the PON system. CONSTITUTION: If a central office(10) multiplexes optical signals having different wavelengths and transmits the optical signals to a remote node(20), the remote node(20) demultiplexes the multiplexed optical signals, and outputs the demultiplexed optical signals to each ONU(30). Each ONU(30) receives the optical signals, respectively. If the ONUs(30) transmit optical signals having different wavelengths to the remote node(20), the remote node(20) multiplexes the optical signals, and transmits the multiplexed optical signals to the central office(10). The central office(10) demultiplexes the transmitted optical signals, and receives the optical signals having the different wavelengths.

Description

WAVELENGTH DIVISION MULTIPLEXING-PASSIVE OPTICAL NETWORK USING SAME WAVELENGTH AS UPSTREAM AND DOWNSTREAM CHANEL}

The present invention relates to a wavelength division multiplexing passive optical subscriber network system, and more particularly, to a wavelength division multiplexing passive optical subscriber network system having up-down channels having the same wavelength.

In order to provide subscribers with the rapidly increasing broadband multimedia services and high-speed high-capacity Internet services, optical subscriber network-based networks are indispensable. In order to provide such broadband services to subscribers, optical fibers are directly connected to subscriber access devices. There is a growing interest in connecting optical subscriber networks.

Recently, passive optical subscriber network (PON) using passive optical devices has been actively researched for efficient and economical optical subscriber network construction. Passive optical subscriber network is a central base station (CO) provider of services. The office and the optical network units (ONUs), which are consumers, consist of only passive optical elements. In general, a single optical fiber (Trunk) is used from a central base station to a local base station (RN) installed in an adjacent area of subscribers. It is configured to minimize the length of the optical fiber by connecting it to the fiber and connecting the local base station to each subscriber access device by a separate fiber.

This passive optical subscriber network (PON) has the advantages of minimizing the length of the optical fiber and sharing passive optical devices with subscribers, thus reducing the initial investment cost and making it easy to maintain, maintain and manage the optical network. Among them, the Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) not only provides a large amount of information to each subscriber, but also provides excellent security and easy performance. It is attracting attention as the next generation subscriber network for the information age.

FIG. 1 is a block diagram of a conventional wavelength division multiplexing passive optical subscriber network system. As shown in FIG. 1, a conventional wavelength division multiplexing passive optical subscriber network generally includes a subscriber access device (i. Different wavelengths λ ₁ to λ _N are allocated to 300 to transmit data simultaneously through one optical communication line, and each subscriber access device 300 uses the assigned wavelengths λ _{N +1 to} λ _2N . It is configured to transmit data at all times.

However, since the wavelength division multiplexing passive optical subscriber network must assign different wavelengths to each subscriber, it must have light sources that provide different wavelengths, thereby providing a centralized method to minimize interference with adjacent wavelengths (channels). There is a problem in that an expensive light source such as a distributed feedback laser diode (DFB LD) having a very narrow spectrum width is used for the base station 100 and the subscriber access device 300.

In addition, since the conventional wavelength division multiplexing passive optical subscriber network uses a light source having a very narrow spectral width, additional devices such as temperature stabilization and current stabilization are required for stabilizing oscillation wavelengths, and they are different from each other as up and down channels. Since the wavelength is used, a multiplexer and a demultiplexer must be separately installed for each wavelength for bidirectional transmission, which causes a problem in that the system configuration is expensive.

In order to solve this problem, the following research papers are known that economically construct a wavelength division multiplexing passive optical subscriber network using low-cost optical devices already commercialized.

The research paper ("A low cost WDM source with an ASE injected Fabry-Perot semiconductor laser", IEEE Photonics Technology Letter, Vol. 12, no.11, pp.1067-1069, 2000), is a light source for central base stations and subscriber access devices. Amplified spontaneous emission (ASE) and low-cost Fabry-Perot Laser Diode (FP LD) are respectively used, and the natural emission light output from the central base station is Distributing the Fabry-Perot laser diode by injecting it into the ferret laser diode and fixing the output wavelength of the Fabry-Perot laser diode to the same wavelength as the natural emission light (hereinafter referred to as 'Injection Locking'). A method of economically implementing an optical subscriber network system by allowing oscillation in a single mode such as a feedback laser diode is disclosed. However, this system implementation method has a limitation in that a separate light source for generating natural emission light is provided at the central base station.

In addition, the research paper ("Upstream traffic transmitter using injection-locked Fabry-Perot as modulator for WDM access networks", Electronics Letters, Vol. 38, No. 1, pp.43-44, 2002) also includes The distributed feedback laser diode and the Fabry-Perot laser diode are used as light sources, and the optical signal output from the distributed feedback laser diode of the central base station is received by the subscriber access device, partly used for signal detection, and partly used for injection locking. By doing so, a method of economically implementing an optical subscriber network system is disclosed. However, such a system implementation method also has a limitation in that an expensive distributed feedback laser diode is used as a light source of the central base station.

The present invention has been made to solve the above problems, and an object of the present invention is to transmit and receive data in the same wavelength up and down for each channel, and at the same time as a light source of a central base station and a subscriber access device as a light source The present invention provides a wavelength division multiplex passive optical subscriber network system that can be implemented at low cost.

1 is a block diagram of a conventional wavelength division multiplexing passive optical subscriber network system.

2 is a block diagram of a wavelength division multiplexing passive optical subscriber network system according to the present invention.

3 is a block diagram of a wavelength division multiplexing passive optical subscriber network system according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10 ... Central Office 11 ... First Transmitter

12 ... First Receiver 13 ... First Optical Splitter

14 ... 1st Multi / Demultiplexer (MUX / DEMUX)

20.Local Node

21 ... 2nd Multi / Demultiplexer (MUX / DEMUX)

30.Optical Network Unit

31 ... second transmitter 32 ... second receiver

33.2nd optical splitter

In order to achieve the above object, the wavelength division multiplexing passive optical subscriber network system according to the present invention is a wavelength division multiplexing passive optical subscriber network system in which a central base station, a local base station, and a plurality of subscriber access devices are connected by optical fibers. The central base station generates optical signals of different specific wavelengths and transmits them to a local base station or receives an optical signal having the same wavelength as the optical signal from a local base station, and the local base station demultiplexes the optical signals transmitted from the central base station. Each of the optical signals transmitted from the subscriber access device or multiplexed to the central base station by multiplexing the optical signal transmitted from the subscriber access device, the subscriber access device receives the optical signal transmitted from the local base station and the optical signal of the same wavelength as the received optical signal To transmit to the local base station The.

Hereinafter, the configuration and operation of the wavelength division multiplexing passive optical subscriber network system according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a configuration diagram of a wavelength division multiplexing passive optical subscriber network system according to the present invention, and includes a central base station 10, a local base station 20, and a subscriber access device 30. 30 is connected to the central base station 10 through several optical links.

As shown in FIG. 2, in the wavelength division multiplexing passive optical subscriber network system according to the present invention, the central base station 10 multiplexes the optical signals λ ₁ ,..., Λ _N at different wavelengths. When transmitting to the base station 20, the local base station 20 demultiplexes the multiplexed optical signals (λ ₁ λ ₂ ... λ _N ) transmitted from the central base station 10 to demultiplexed optical signals of different wavelengths. (λ ₁ ,..., λ _N ) are respectively output to the subscriber access device 30, and the subscriber access device 30 is provided with optical signals λ ₁ ,..., of different wavelengths transmitted from the local base station 20. λ _N ) is configured to receive each. On the contrary, when the subscriber access device 30 transmits optical signals λ ₁ ,..., Λ _N of different specific wavelengths to the local base station 20, the local base station 20 transmits the data from the subscriber access device 30. the optical signals (λ _1, ..., λ _N), to multiplex and transmit to the central station 10, the central base station 10 in the optical signal transmitted from the local base station _{(20) (λ 1 λ 2} ... λ N ) Can be demultiplexed to receive optical signals λ ₁ ,..., Λ _N of different specific wavelengths.

The central base station 10 is identical to the plurality of first transmitters 11 outputting optical signals λ ₁ ,..., Λ _N of different wavelengths, and the optical signals output from the first transmitter 11. A plurality of first receivers 12 for receiving optical signals λ ₁ ,..., Λ _{N of} wavelengths, and the first transmitter 11 and the first receiver 12 for the optical signals transmitted from the local base station 20. Multiplexes the first optical splitter 13 and the optical signals λ ₁ ,..., Λ _N inputted from the plurality of first transmitters 11 and outputs the multiplexed optical signals. ) and the optical signal input from (including the first multi / demultiplexer 14 for demultiplexing and outputting a _{λ 1 λ 2 ... λ N)} .

The local base station 20 receives the multiplexed optical signals λ ₁ λ ₂ ... Λ _N transmitted from the central base station 10 and demultiplexes them to demultiplexed optical signals λ ₁ , respectively. ..., Λ _N ) are respectively transmitted to the plurality of subscriber access devices 30, and the optical signals λ ₁ ,..., Λ _N transmitted from each subscriber access device 30 are multiplexed to provide multiplexed optical signals ( and a second multi / demultiplexer 21 for transmitting λ ₁ λ ₂ ... λ _N ) to the central base station 10.

The subscriber access device 30 includes a plurality of second transmitters 31 and a local base station 20 that transmit optical signals λ ₁ ,..., Λ _N having the same wavelength as those transmitted from the central base station 10. ) A plurality of second receivers 32 for receiving optical signals λ ₁ ,..., Λ _N , and optical signals λ ₁ , ..., λ _N transmitted from the local base station 20. And a plurality of second optical splitters 33 for separating the second transmitter 31 and the second receiver 32.

In the present invention, a low-cost Fabry-Perot laser diode is used as a light source instead of an expensive distributed feedback laser diode which requires strict wavelength stability to implement a low cost system. Hereinafter, the first transmitter 11 of the central base station 10 is used. And a case where a Fabry-Perot laser diode is used as a light source of the second transmitter 31 of the subscriber access device 30, the operation of the wavelength division multiplexing passive optical subscriber network system according to the present invention will be described.

First, in the case of a downlink signal from the central base station 10 to the subscriber access device 30, a narrow band incoherence is generated from the central base station 10 to the Fabry-Perot laser diode which is a light source of the first transmitter 11. When the light (for example, λ ₁ ) is injected from the outside, the Fabry-Perot laser diode has a main oscillation and the other modes are suppressed because the wavelength of the injected light is the one of several oscillation modes. The output wavelength of the ferret laser diode is fixed at the same wavelength as the injected light (this phenomenon is referred to as 'injection locking' hereinafter), so that the first transmitters 11 of the central base station 10 are oscillated According to the mode, an optical signal (for example, λ ₁ ) having a specific wavelength different from each other is generated and transmitted to the first optical splitter 13. The optical signals λ ₁ ,..., Λ _N generated by the first transmitter 11 are input to the first multi / demultiplexer 14 through the first optical splitter 13 and the first multi / demultiplexer 14 The multiplexer 14 multiplexes the optical signals λ ₁ ,..., Λ _N and transmits the multiplexed optical signals λ ₁ λ ₂ ..., _N to the local base station 20.

When the multiplexed optical signals λ ₁ λ ₂ ... Λ _N are input to the local base station 20, the second multi / demultiplexer 21 of the local base station 20 receives the multiplexed optical signals λ ₁ λ _2. ... λ _N ) is demultiplexed to transmit optical signals (for example, λ ₁ ) having different specific wavelengths to each subscriber access device 30.

When the optical signals of different specific wavelengths (for example, λ ₁ ) are respectively input to the subscriber access device 30, the second optical splitter 33 receives the optical signals of different specific wavelengths transmitted from the local base station 20. (For example, λ ₁ ) is separated into the second transmitter 31 and the second receiver 32, the second receiver 32 is an optical signal of different specific wavelengths transmitted from the second optical splitter 33 For example, λ ₁ ) is received. Meanwhile, when an optical signal (for example, λ ₁ ) is injected into the second transmitter 31 through the second optical splitter 33, the Fabry-Perot laser diode, which is a light source of the second transmitter 31, is injected. Since injection locking is caused by light, the output wavelength of the Fabry-Perot laser diode is fixed at the same wavelength as the injected optical signal, that is, at the same wavelength as the optical signal transmitted from the central base station 10 (for example, λ ₁ ). . Accordingly, the second transmitter 31 of the subscriber access device 30 can transmit an optical signal (for example, λ ₁ ) having the same wavelength as that of the optical signal transmitted from the central base station 10.

On the other hand, the uplink signal from the subscriber access device 30 to the central base station 10 is the reverse of the above-described method. That is, the output wavelength of the Fabry-Perot laser diode which is the light source of the second transmitters 31 in the subscriber access device 30 is fixed to the same wavelength (for example, λ ₁ ) as the optical signal transmitted from the central base station 10. As such, the second transmitter 31 generates optical signals (for example, λ ₁ ) having different specific wavelengths, and transmits them to the local base station 20 through the second optical splitter 33.

The second multi / demultiplexer 21 of the local base station 20 multiplexes the optical signals λ ₁ ,..., Λ _N transmitted from the subscriber access device 30 and multiplexes the optical signals λ ₁ λ _2. Λ _N ) is transmitted to the central base station 10.

The first multi / demultiplexer 14, the optical signal of the multiplexed optical signal by demultiplexing the (λ _1, λ ₂ ... λ _N) of different specific wavelength transmitted from the local base station 20 of the center base station 10 ( For example, when λ ₁ is transmitted to the first optical splitter 13, the first optical splitter 13 separates the optical signal into a first transmitter 11 and a first receiver 12, and the first receiver. Reference numeral 12 receives an optical signal (for example, λ ₁ ) of different specific wavelengths transmitted from the first optical splitter 13. Meanwhile, when an optical signal (for example, λ ₁ ) is injected into the first transmitter 11 through the first optical splitter 13, the Fabry-Perot laser diode, which is a light source of the first transmitter 11, is injected. Since the injection lock is performed by the optical signal, the output wavelength of the Fabry-Perot laser diode is the same wavelength as the injected optical signal, that is, the same wavelength as the optical signal transmitted from the subscriber connection device 30 (for example, λ ₁ ). It is fixed.

Accordingly, the uplink and downlink may use the same transmit / receive wavelengths λ ₁ to λ _{N for} each channel, and thus, different wavelengths of different wavelengths may be applied to the central base station 10 and the local base station 20 for up-and-down transmission. There is no need to separately install a multi / demultiplexer (e.g., λ ₁ to λ _N multi / demultiplexer downward, and λ _{N + 1} to λ _2N multi / demultiplexer upward) to multi / demultiplex the optical signal.

In addition, in the conventional passive optical subscriber network system, as shown in FIG. 1, a separate wavelength division filter (WDM filter) 130 is used to separate the optical signal from the central base station 100 and the subscriber access device 300 in some cases. 330 is required, but the present invention uses inexpensive optical splitters 13 and 33 instead of filters, so that the wavelength division multiplexing passive optical subscriber network system can be constructed at low cost.

Meanwhile, in the present embodiment, a 1 × 2 optical splitter is used as the first optical splitter 13 and the second optical splitter 33. In this case, 1 × 2 outputs the optical power of the input optical signal in half. Due to the structural characteristics of the optical splitter, losses occur in terms of optical power. For example, in the case of the downlink signal, since the first optical splitter 13 divides the optical power of the optical signal output from the first transmitter 11 in half and outputs it to the first multi / demultiplexer 14, the 3dB The optical loss is generated, and the second optical splitter 33 divides the optical power of the optical signal output from the local base station 20 in half and outputs it to the second transmitter 31 and the second receiver 32, respectively. Due to the 3dB optical loss is generated, the overall 6dB loss in terms of optical power. However, in the case of the wavelength division multiplexing optical subscriber network system, since the distance between the central base station 10 and the subscriber access device 30 is generally within several km to several tens of kilometers, the optical power loss of about 6 dB is not a big problem. .

In this embodiment, when the optical signal of the same wavelength is used as the transmission / reception signal, when near-end crosstalk occurs when the transmission signal is reflected from the connection portion between the optical fiber and the optical splitter and the connection portion between the optical fiber and the multi / demultiplexer, the reflected transmission signal is normal. The problem of processing into a received signal may occur, but the problem of near-end crosstalk can be eliminated by a method commonly used to prevent reflection of an optical signal in an optical fiber. For example, a method of adjusting the angle of a reflected transmission signal by using an Angled Polished Connector (APC) type connector formed by tilting an end of a connector at a predetermined angle, or by slicing a junction where reflection of a transmission signal may occur ( Slicing) to prevent the reflection of the optical signal can be used.

3 is a diagram illustrating a configuration of a wavelength division multiplexing passive optical subscriber network system according to an embodiment of the present invention, wherein a bidirectional optical amplifier (Bidirectional Optical Amplifier) between the central base station 10 and the subscriber access device 30 ( 40) to increase the output of the multiplexed up and down channels, thereby increasing the transmission distance or transmission speed of the up and down channels.

As shown in FIG. 3, the inserted bidirectional optical amplifier (for example, EDFA) 40 amplifies the input up and down optical signals. At this time, in the bidirectional optical amplifier 40, the natural emission light, which is broadband noise, ASE) is generated. In the conventional wavelength division multiplexing passive optical subscriber network system, natural emission light is treated as noise, but in the wavelength division multiplexing passive optical subscriber network system according to the present invention, the optical signal passing through the bidirectional optical amplifier 40 is the first multi / Since it is routed for each wavelength while passing through the demultiplexer 14 or the second multi / demultiplexer 21, the natural emission light included in the optical signal is also used for injection locking of the Fabry-Perot laser diode. For this reason, conventional optical amplifiers require additional equipment such as an isolator to improve noise characteristics. However, in the present invention, since natural emission light is used for injection locking, the optical signals of up and down optical signals can be simply added without additional devices. You can increase the output.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Therefore, according to the present invention, since the data can be transmitted and received with the same wavelength up and down for each channel, the wavelength division multiplexing method compared with the conventional passive optical subscriber network that requires a separate multiplexer and a demultiplexer because the wavelength of the upstream and downstream signals are different from each other. It is effective to implement a passive optical subscriber network system efficiently and economically.

In addition, according to the present invention, by using a low-cost Fabry-Perot laser diode as a light source for the central base station and the subscriber access device, the system construction cost can be further reduced compared to a conventional optical subscriber network using an expensive laser diode as a light source. It can be effective.

Claims (9)

In the wavelength division multiplex passive optical subscriber network system consisting of a central base station, a local base station and a plurality of subscriber access devices connected by optical fibers, The central base station generates an optical signal of a specific wavelength different from each other and transmits to the local base station or receives an optical signal of the same wavelength as the optical signal from the local base station, The local base station demultiplexes the optical signal transmitted from the central base station to each subscriber accessing device or multiplexes the optical signal transmitted from the subscriber accessing device to the central base station, And the subscriber access device receives the optical signal transmitted from the local base station and transmits an optical signal having the same wavelength as the received optical signal to the local base station. The method of claim 1, wherein the central base station, A plurality of first transmitters for outputting optical signals having different specific wavelengths; A plurality of first receivers for receiving an optical signal having the same wavelength as that of the optical signal output from the first transmitter; A plurality of first optical splitters for separating the optical signal transmitted from the local base station into the first transmitter and the second receiver; And And a first multi / demultiplexer for multiplexing and outputting an optical signal output from the first transmitter and demultiplexing and outputting an optical signal transmitted from the local base station. . 3. The wavelength division multiplex passive optical subscriber network system according to claim 2, wherein the first transmitter is injection locked by an optical signal separated through the first optical splitter. 3. The wavelength division multiplex passive optical subscriber network system according to claim 2, wherein the first transmitter outputs an optical signal having the same wavelength as that of the optical signal transmitted from the subscriber access device. The method of claim 1, wherein the local base station, And a second multi / demultiplexer for demultiplexing the optical signals transmitted from the central base station and transmitting the demultiplexed optical signals to the plurality of subscriber access devices, and multiplexing the optical signals transmitted from the subscriber access devices to the central base station. A wavelength division multiplexing passive optical subscriber network system characterized by the above-mentioned. The method of claim 1, wherein the subscriber access device, A plurality of second transmitters generating and transmitting an optical signal having the same wavelength as that of the optical signal output from the central base station; A plurality of second receivers for receiving an optical signal transmitted from the local base station; And And a plurality of second optical splitters for separating the optical signal transmitted from the local base station into the second transmitter and the second receiver. 7. The wavelength division multiplex passive optical subscriber network system according to claim 6, wherein the second transmitter is injection locked by an optical signal separated through the second optical splitter. 7. The wavelength division multiplex passive optical subscriber network system according to claim 6, wherein the second transmitter outputs an optical signal having the same wavelength as that of the optical signal transmitted from the central base station. 2. The wavelength division multiplex passive optical subscriber network system according to claim 1, further comprising a bidirectional optical amplifier.