KR20040107534A - Optical signal transmitting system - Google Patents

Abstract

PURPOSE: A system for transmitting optical signals is provided to construct an optical transmission system more simply and inexpensively by using an optical tansmit-receive module as a common port in an OLT(Optical Line Terminal) and installing a single optical cable for the transmission lines between the OLT and plural ONUs(Optical Network Units). CONSTITUTION: A system for transmitting optical signals comprises an OLT(100), an optical splitter(200), plural ONUs(300,400), and plural service subscribers(520,540). The OLT(100) combines various kinds of signals into a single signal and transmits the combined signal through a single optical cable. The optical splitter(200), of which one side is connected to the OLT(100) through the optical cable and the other side is connected with the ONUs(300,400), broadcasts the combined optical signal, transmitted through the optical cable from the OLT(100), to each of the ONUs(300,400). Each of the ONUs(300,400) classifies the transmitted optical signal according to signal kinds, combines the classified signals according to the service subscription of service subscribers, and selectively transmits the classified and combined optical signals to associated subscribers.

Description

Optical signal transmission system {OPTICAL SIGNAL TRANSMITTING SYSTEM}

The present invention relates to an optical signal transmission system, and more particularly, to establish an optical signal transmission path between an optical line terminal (OLT) of a fiber to the home (FTTH) and a plurality of optical network units (ONUs). An optical signal transmission system.

With the development of broadcasting and communication technology, there is a demand for a transmission system capable of providing a better transmission quality and transmission speed in transmitting an optical signal from a service provider to a subscriber. One of them is FTTH (Fiber To The Home). FTTH is a transmission system in which a transmission medium connected from a service provider (or head end) of a network to a subscriber is connected with an optical cable instead of a coaxial cable.

In a transmission system using an optical signal, a transmission system of a service provider is called an optical line terminal (OLT), and a transmission system of a service subscriber side that receives a service provided from the OLT and transmits the signal to an end subscriber after receiving a signal from the optical network unit (ONU) ). Such a transmission system generally has a structure in which a plurality of ONUs are connected to one OLT. The ONU provides services at the request of subscribers. Such a transmission system is called an active optical network.

Here, ONU, which is a transmission system of a service subscriber, is an end device of an optical communication network that provides a service interface to end users. The ONU accommodates Fiber To The Curb (FTTC), Fiber To The Building (FTTB), Fiber To The Floor (FTTF), FiberTo The Home (FTTH), and Fiber To The Office (FTTO). Accordingly, ONU implements high service accessibility to subscribers. ONU is connected to the subscriber and the cable for transmitting the analog signal transmitted from the subscriber and the OLT is connected to the optical facilities for transmitting and receiving optical signals to perform the function. Accordingly, the ONU performs photoelectric conversion for converting the optical signal transmitted from the OLT into an electrical signal and transmitting the signal to the subscriber, and all-optical conversion for converting the electrical signal transmitted from the subscriber into the optical signal and transmitting the optical signal to the OLT.

1 is a block diagram illustrating an example of a conventional optical signal transmission system. As shown, a method of serving broadcast and communication to subscribers connected to the optical access node 8 is a hybrid fiber coaxial (HFC) network, each of which uses a different optical fiber for data and analog broadcast signals for digital broadcasting. Transmission is common. That is, in the illustrated optical signal transmission system, the data signal is (dense) wavelength division multiplexed (Dense Wavelength Division Multiplex, hereinafter referred to as DWDM) and transmitted through one optical fiber, and the analog broadcast signal is transmitted through another optical fiber. .

Optical coaxial mixed networks, on the other hand, are communication networks in which optical fiber cables and coaxial cables are used in different parts of the network to transmit broadband content such as video, data, and voice. In general, for local cable television companies, fiber optic cables are used to service nodes that are in close proximity to users in the enterprise or home from cable headends. Coaxial cables are also used to enter individual businesses or homes from nodes where fiber optic cables are used.

Hereinafter, the Dense Wavelength Division Multiplex (DWDM) will be described. First, Wavelength Division Multiplexing (WDM) will be described before describing the DWDM. WDM refers to equipment that creates a virtual line by creating a separate frequency band in addition to the existing frequency in the optical fiber, and makes the same effect as installing a new cable network while using the existing network as it is.

Dense Wavelength Division Multiplexer (DWDM) refers to a device that divides and concentrates large-scale traffic such as 155M, 622M, 2.5G, 10G, and Gigabit data by wavelength using an existing transmission path. In other words, DWDM enables the transmission of multiple wavelengths over a single fiber. More precisely, broadcast data, Internet data, SONET data, and ATM data can all be transmitted simultaneously in the optical fiber.

As shown, a conventional optical signal transmission system optically transmits data signals for analog broadcasting and analog broadcasting signals from OLT to ONU using two different optical fibers. Therefore, there is a problem in that a transmission line of two different optical fibers is required in order to provide a subscriber with a conventional optical signal transmission system for digital broadcasting and analog broadcasting. Accordingly, when the conventional optical signal transmission system is constructed, there is a problem in that the cost of the system construction is high. In particular, when a plurality of ONUs are connected to one OLT, it becomes expensive to construct an optical transmission system.

Hereinafter, a process of transmitting a data signal for digital broadcasting will be briefly described with reference to the accompanying drawings. The MUX 2 synthesizes data signals output from a plurality of DWDM Txs (32 in the figure). The EDFA (Erbium Doped Fiber Amplifier) 3 optically amplifies the data signal synthesized in the MUX 2. The optical amplification principle of the EDFA 3 is to amplify a weak optical signal directly by doping a special material called erbium into the optical fiber and pumping it with a laser.

The amplified data signal is transmitted to the ONU, and the EDFA 4 of the ONU performs the same function as the EDFA 3 of the OLT. The MUX 5 classifies and outputs the data signal optically amplified by the EDFA 4 for each DWDM Tx.

The optical combiner 6 combines the data signal outputted from the MUX 5 with the optical signal transmitted from the OLT and the analog broadcast signal AB outputted from the analog broadcast Tx transmitted through another optical fiber, respectively. Output to (8).

2 is a system configuration diagram proposed to solve the problem of the optical signal transmission system of FIG. As shown, the optical signal transmission system consists of an OLT 10, an ONU 20, 30, and a service subscriber 25, 35.

The OLT 10 combines different types of data into one signal and transmits the same to each ONU 20 and 30. More specifically, the OLT 10 includes a multiplexer (MUX) 18 for synthesizing the digital broadcast 12, the analog broadcast 14, and the Internet data 16 and transmitting them through one transmission line. . Accordingly, the OLT 10 and one ONU 20 may transmit a signal obtained by synthesizing the digital broadcast 12, the analog broadcast 14, and the Internet data 16 through one transmission line (optical cable). At this time, the optical transmission module (not shown) provided in the OLT 10 to be connected to the ONU to transmit a signal should be provided as many as the number of ONU connected.

The ONUs 20 and 30 classify the optical signals transmitted from the OLT 10 according to the types of signals and transmit them to the service subscribers 25 and 35. The service subscribers 25 and 35 receive the service.

On the other hand, the multiplexer (MUX) 18 of the OLT 10 and the multiplexers (MUX) 22 and 32 of the ONUs 20 and 30 are a CWDM (Coarse Wavelength Division Multiplexer) method to which a CWDM (Coarse Wavelength Division Multiplexing) scheme is applied. MUX is applied.

When the optical signal transmission system is constructed in this manner, a plurality of types of signals may be transmitted between one OLT 10 and one ONU 20 through one optical cable. However, in order to connect a plurality of ONUs to the OLT 10, the ONUs must be connected to the OLTs, respectively, so that the system configuration is complicated and the number of ONUs requires transmission lines of optical cables. In addition, when the distance between the OLT 10 and the ONU (20,30) is several tens of kilometers away, there is a problem in that the cost burden due to the optical cable required to connect the OLT 10 and the ONU (20,30), respectively. In addition, the OLT 10 and the ONU 20 and 30 are connected to the optical cable, respectively, and there is a problem in that a large cost is required to install the connected optical cable.

An object of the present invention for solving the above problems, when configuring a system for optical transmission of data communication and analog broadcast signal for digital broadcasting from OLT to ONU, optical signal transmission system that can be built at a lower cost To provide.

Another object of the present invention is to provide an optical signal transmission system capable of constructing a system for transmitting optical signals between an OLT and an ONU with a simpler configuration.

1 is a block diagram showing an example of a conventional optical signal transmission system;

2 is a system configuration proposed to solve the problem of the optical signal transmission system of FIG.

3 shows a preferred embodiment of an optical signal transmission system according to the invention, and

4 is a diagram illustrating a signal transmission and reception technique between the OLT 100 and the plurality of ONUs 300,..., 400 of FIG. 3.

Explanation of symbols on the main parts of the drawings

100: OLT 180: photosynthesis

200: Optical distributor 300,400: ONU

320,420: Optical classifier 340,440: Optical transmitter

520,540: service subscriber

The object as described above, OLT having a photosynthesis for synthesizing heterogeneous optical signal into a single signal and transmitting to the optical cable through one transmission module; An optical splitter having one side connected to the OLT and an optical cable and transmitting the synthesized optical signal transmitted through the optical cable to a plurality of optical cables connected to the other side, respectively; And an optical classifier which is connected to the plurality of optical cables connected to the other side of the optical splitter, respectively, and classifies the synthesized optical signal transmitted from the optical splitter according to the type of the signal. It is achieved by an optical signal transmission system including a plurality of ONUs each having an optical transmission unit which is synthesized according to whether or not and transmitted to a service subscriber.

Preferably, the optical signal transmission between the OLT and the plurality of ONU is applied to the E-PON or ATM-PON transmission scheme. In addition, when the OLT transmits an optical signal to a plurality of ONUs, the MAC technique is applied when transmitting an optical signal by a broadcasting method, and when the OLT transmits an optical signal to an OLT.

Preferably, the plurality of ONUs transmits optical signals for transmission at a predetermined time to an optical splitter, and the optical splitter sequentially transmits optical signals transmitted from the plurality of ONUs to OLTs sequentially for each time slot according to the received order. Do. In addition, the wavelength of the optical signal used in the top-down transmission is 1550nm, the wavelength of the optical signal used in the bottom-up transmission is 1310nm.

According to the present invention, by using one optical transmission module at the OLT stage as a common port and laying a transmission line of several tens of kilometers between the OLT and the plurality of ONUs with one optical cable, the system structure is simpler and lower cost. A signal transmission system can be constructed. In addition, when transmitting an optical signal to the OLT through one optical cable, by using the MAC scheme to sequentially transmit the optical signal transmitted from each ONU for each time slot, to ensure the quality of service (QoS) for data during the bottom-up transmission can do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements in the figures are represented by the same numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

3 is a view showing a preferred embodiment of the optical signal transmission system according to the present invention.

As shown, the optical signal transmission system has an OLT 100, an optical splitter 200, a plurality of ONUs 300, 400, and a plurality of service subscribers 520, 540.

The OLT 100 combines different types of signals into one signal and transmits the same to one optical transmission line. In the present embodiment, examples of different types of signals will be described as digital broadcasting 120, analog broadcasting 140, and internet data 160. FIG. The photosynthesis unit 180 provided in the OLT 100 synthesizes the digital broadcast 120, the analog broadcast 140, and the Internet data 160 into one optical signal. The synthesized optical signal is transmitted to an optical cable which is a transmission line through one optical transmission / reception module (not shown). In addition, when the OLT 100 transmits the synthesized optical signal through one optical cable, the OLT 100 transmits the synthesized optical signal by a broadcasting method.

The optical splitter 200 has one side connected to the OLT 100 and 1: 1 via an optical cable, and the other side is connected to the plurality of ONUs 300,..., 400. In the figure, there are N ONUs 300,..., 400 connected to the optical splitter 200. Accordingly, the optical splitter 200 transmits the synthesized optical signal transmitted from the OLT 100 through the optical cable to the respective ONUs 300,..., 400 by the same broadcasting method. At this time, the distance between the OLT 100 and the optical splitter 200 generally reaches tens of Km. That is, between the OLT 100 and the optical splitter 200 are connected 1: 1 by an optical cable of several tens of Km.

The plurality of ONUs 300,..., 400 correspond to the optical classifiers 320,..., 420, and the light transmitting units 340,..., 440, respectively. Since each ONU 300,..., 400 performs the same function, one ONU 300 will be described as an example. Accordingly, the ONU 300 classifies the optical signals transmitted from the optical splitter 200 according to the type of the signal and synthesizes the classified signals according to whether the service subscriber 520 is subscribed to the service subscriber 520. send. That is, the optical classifier 320 of the ONU 300 classifies the synthesized optical signal transmitted from the optical splitter 200 into digital broadcasting 120, analog broadcasting 140, and internet data 160 according to the type of signal. do. The optical transmitter 340 synthesizes each optical signal classified by the optical classifier 320 according to whether the user subscribes to the service and selectively transmits the optical signal to the service subscriber 520. The N-th ONU 400 also performs the same function as the first ONU 300 and synthesizes the optical signal according to whether to subscribe to the service and selectively transmits it to the service subscriber 540.

Therefore, by using one optical transmitting / receiving module at the OLT 100 end as a common port, and installing several tens of kilometers of transmission line between the OLT 100 and the plurality of ONUs (300, ..., 400) with one optical cable In addition, the optical signal transmission system can be constructed at a simpler and lower cost.

Meanwhile, a transmission technology of an Ethernet Passive Optical Network (E-PON) or an Asynchronous Transfer Mode Passive Optical Network (ATM-PON) is applied between the OLT 100 and the plurality of ONUs 300,..., 400 according to the present invention. do.

4 is a diagram illustrating a signal transmission and reception technique between the OLT 100 and the plurality of ONUs 300,..., 400 of FIG. 3.

As shown, the optical signal has different wavelengths for uplink transmission (upstream) and downlink transmission (downstream). That is, the downlink transmission transmitted from the OLT 100 to the ONU (300, ..., 400) has a wavelength of 1550 nm, and the uplink transmission is transmitted from the ONU (300, ..., 400) to the OLT 100. It has a wavelength of 1310 nm.

In addition, during downlink transmission, the optical signal transmitted from the OLT 100 is transmitted to the plurality of ONUs 300,..., 400 by broadcasting through the optical splitter 200. In the case of uplink transmission, since each ONU (300, ..., 400) must transmit to the OLT 100 using one optical cable using the same wavelength band, the OLT (100) is adopted by adopting a MAC (Media Access Control) technique. And transmission of the optical signal between the ONU (300, ..., 400). That is, each ONU (300, ..., 400) to set the uplink transmission time to transmit the optical signal only at the set time. Accordingly, the light transmitted to the OLT 100 through the optical splitter 200 It can be seen that the signal is transmitted for each time slot as shown.

Therefore, when transmitting the optical signal to the OLT 100 through one optical cable, by sequentially transmitting the optical signal transmitted from each ONU (300, ..., 400) for each time slot, QoS for the data in the bottom-up transmission (Quality of Service) can be secured.

According to the present invention, by using one optical transmission module at the OLT stage as a common port and laying a transmission line of several tens of kilometers between the OLT and the plurality of ONUs with one optical cable, the system structure is simpler and lower cost. A signal transmission system can be constructed.

In addition, when transmitting an optical signal to the OLT through one optical cable, by using the MAC scheme to sequentially transmit the optical signal transmitted from each ONU for each time slot, to ensure the quality of service (QoS) for data during the bottom-up transmission can do.

In the above, specific preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention attached to the claims. will be.

Claims (6)

In the optical signal transmission system, An OLT having an optical synthesizer for synthesizing heterogeneous optical signals into one signal and transmitting the optical signals through one transmission / reception module; An optical splitter having one side connected to the OLT and the optical cable and transmitting the synthesized optical signal transmitted through the optical cable to a plurality of optical cables connected to the other side, respectively; And An optical classifier which is connected to a plurality of optical cables connected to the other side of the optical splitter, respectively, and classifies the synthesized optical signal transmitted from the optical splitter according to the type of signal, and services the classified signal from the optical splitter. And a plurality of ONUs each having an optical transmission unit for synthesizing according to whether a subscriber subscribes to the service subscriber. The method of claim 1, The optical signal transmission system of any one of the E-PON and ATM-PON transmission scheme is applied to the optical signal transmission between the OLT and the plurality of ONU. The method of claim 2, When the OLT transmits an optical signal to the plurality of ONUs in the downlink transmission, the optical signal is transmitted by a broadcasting method, and the MAC technique is applied in the bottom-up transmission of transmitting the optical signal to the OLT in the plurality of ONUs. Optical signal transmission system, characterized in that. The method of claim 3, wherein The plurality of ONUs respectively transmits an optical signal for transmitting at a set time to the optical splitter, and the optical splitter sequentially transmits the optical signals transmitted from the plurality of ONUs to the OLT in time slots according to the received order. Optical signal transmission system, characterized in that. The method of claim 3, wherein The wavelength of the optical signal used in the top-down transmission is 1550nm and the wavelength of the optical signal used in the bottom-up transmission is 1310nm. The method of claim 1, The heterogeneous optical signal includes a digital broadcast, an analog broadcast, and internet data.