KR100431238B1 - Optical Communication System using Add/Drop Type Optic Module - Google Patents

Abstract

The present invention installs a wavelength pass add / drop optical module in an optical path connected between an existing transmitting station or a base station and a receiving station or a repeater, thereby adding and dropping an optical fiber that can broaden a communication range without adding an optical fiber and a repeater. The present invention relates to an optical communication system using a module, and more particularly, to an optical communication system that provides a high quality communication service by connecting a base station and a master unit to provide a mobile communication service in a shaded / square area where radio waves cannot reach and to extend a communication range. It includes a slave unit located between the base station and the master unit to communicate the communication wavelength of the base station and the master unit to each other, and independently communicate with each other without control of the base station and the master unit. Therefore, according to the present invention, by installing a slave unit in the optical path connected to the base unit and the master unit of the repeater, the existing base station and the master unit can communicate without distortion or loss of signal, and can communicate with each other between the slave units. It works.

Description

Optical Communication System using Add / Drop Type Optic Module

The present invention relates to an optical communication system using an add / drop optical module, and more particularly, to install a wavelength pass add / drop optical module in an optical path connected between an existing transmitting station or base station and a receiving station or repeater. The present invention relates to an optical communication system using an add / drop optical module that can extend a communication range without adding an optical fiber and a repeater.

Recently, with the development of mobile communication services, general consumers are not demanding areas as well as mountain wallpaper and remote islands that mobile communication service could not reach, as well as underground spaces and apartment complexes, which remain as radio blind spots due to poor radio environment in urban areas. I want a higher quality service. However, in order to meet these demands, constructing and operating a base station at a high cost in a low-traffic area deteriorates the management account of the mobile operator and wastes national resources due to the inefficiency of the investment. Accordingly, there is a demand for a method that can secure coverage and improve call quality as a concept different from existing mobile communication systems. Advanced countries are actively reviewing relay systems using CATV networks, and considering the topographical characteristics of Korea, where more than 80% of the land is mountainous and hilly, the line-of-sight between base stations and relay stations The use of microwave or laser relay systems that need to be secured is very limited.

1 is a schematic configuration diagram of a conventional optical communication system, in which a conventional optical communication system 100 includes a base station 110 and a repeater 120, and the repeater 120 is again a master unit 125. ) And slave units 125a to 125d. In addition, although only one master unit 125 is shown in FIG. 1, three master units 125 may be connected to each base station 110, and four slave units 125a to 125d may be connected to each master unit 125. Can be.

The base station 110 serves as a bridge connecting the switching center (not shown) and the mobile terminal, a wired network connecting the base station 110 and the switching station, a wireless network connecting the mobile terminal and the base station 110 and the like. It consists of antenna, transmitter, receiver, and power supply for wireless connection, and is in charge of matching function so that they can be interconnected.

The master unit 125 of the repeater 120 is connected to the base station 110, and the slave units 125a to 125d are linked to the master unit 125 by an optical cable. Here, the optical communication from the base station 110 to the master unit 125 uses a wavelength of 1310 nm, and the optical communication from the master unit 125 to the base station 110 uses a wavelength of 1550 nm. Since the optical communication system 100 transmits and receives radio waves by using an optical cable, it is possible to implement excellent call quality that can communicate with minimal radio wave loss. Considering that the service range of the base station 110 is within about 1.5 km in the downtown area and about 5 km in the suburban area, the optical communication system 100 may have a maximum of 12 slave units in a base station 110 in a radius of 20 km. It can be installed in a short time, so it can serve a wide range of areas.

In such an optical communication system 100, by realizing a high-tech information communication network, a signal from one place in a subscriber network such as CATV or FITL (Fiber In To Loop) is distributed to several places or vice versa. A multiplexing device that combines this is necessary. Such a multiplexing device is not as simple as in the case of conventional communication cables and can be realized by a special device, that is, an optical coupler. In a very simple case, an optical coupler is commercially available, which can be from 1 x 2 (that is, splitting a signal into two channels) to 32 x 32 (that is, receiving 32 channels and then splitting them back into 32 channels). In the early days of optical communication, a complicated communication network configuration in which an optical fiber and an optical cable channel was expanded without using an optical coupler became a simple communication network by using an optical coupler. There are various types of couplers according to the information communication network configuration, such as a star coupler, a directional coupler and a tree coupler.

In addition, a wavelength division multiplexing device (WDM), which is used as one of a special coupler and divides the wavelength of light (signal), is used. For example, WDM separates 1310nm wavelength from 1550nm wavelength and inputs two different signals with different wavelengths, transmits them through one channel or fiber optic cable, and receives the integrated signal and separates them into two signals. Play a role. The mechanism of the WDM function is a grating method using the principle that the refraction and reflection change according to the wavelength, and a dichroic coating method using the principle that the specific wavelength passes through the filter but reflects other wavelengths. There is this.

However, such a conventional optical communication system has various problems. First, in the conventional optical communication system, since the network is constructed in a 1: 1, 1: 2, 1: 3 manner according to the installation and expandability of the master unit and the slave unit, the repeater demand has already reached the saturation state, and the slave unit is added. If you want to build it is inconvenient to establish a separate optical cable. In addition, the cost for the expansion of the optical cable is added to increase the cost burden of the carrier. Second, since the slave units are controlled by the master unit without being controlled by the base station, communication between the slave units is not free. Of course, communication between the slave units is also possible, but to realize this, additional equipment must be implemented in the slave unit. Third, the multiplexing method using the optical coupler is difficult to vary the wavelength and has a disadvantage of large and small losses during transmission depending on the branching ratio. It is difficult to adapt to a fluid environment because a fixed specific wavelength is used to distribute or combine desired wavelengths using an optocoupler.

Accordingly, the present invention has been made to solve the conventional problems as described above, the object of the present invention is a wavelength pass add / drop type 4 wavelength in an optical communication system using a conventional 1: 1 method 1310nm, 1550nm WDM The present invention provides an optical communication system using an add / drop optical module for providing a low cost optical communication service without installing an additional optical cable by installing a slave unit composed of an optical module.

1 is a schematic configuration diagram of a conventional optical communication system,

2 is a schematic configuration diagram of an optical communication system according to the present invention;

3 is an exemplary signal flow diagram illustrating an internal configuration and a wavelength flow of a slave unit of FIG. 2.

♣ Explanation of symbols for the main parts of the drawing ♣

210: base station 220: master unit

230: first slave unit 240: second slave unit

250: optical cable

In order to achieve the above object, the present invention provides a mobile communication service in a shaded / square area where radio waves do not reach, and an optical communication system for providing a high quality communication service by connecting a base station and a master unit to widen the communication range. And a slave unit positioned between the master unit and the base station and the master unit to communicate with each other, and independently communicating with each other without control of the base station and the master unit.

In addition, the slave unit is characterized in that two or more, and the communication wavelength between the base station and the master unit and the communication wavelength between the slave unit is characterized in that a specific wavelength from 1300nm to 1700nm is selected and used.

According to the present invention, the slave unit is connected between the base station and the master unit so that the slave units can communicate with each other, and the slave unit is installed on the existing optical line without the additional optical line. Therefore, the communication range can be widened and stable communication reliability can be realized. That is, the existing base station and the master unit is to communicate as it is, and the slave unit can communicate with each other independently. In addition, wavelength blocking to prevent interference of adjacent wavelengths is controlled so that the isolation ratio is approximately 60 dB using a fiber type or microlens type filter in each line. In some cases, the isolation ratio can be changed freely in the range of 25 to 60 dB.

Hereinafter, exemplary embodiments of an optical communication system using an add / drop optical module according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a schematic configuration diagram of an optical communication system 200 according to the present invention. The optical communication system 200 includes a base station 210, a master unit 220, and slave units 230 and 240, respectively. The component of is connected with the optical cable 250. Here, although only two slave units 230 and 240 are shown, it is obvious to those skilled in the art that a plurality of slave units 230 and 240 may be connected according to the application environment of the present invention.

The base station 210 serves as a bridge connecting the switching center (not shown) and the mobile terminal, and includes a wired network connecting the base station 210 and the switching station, a wireless network connecting the mobile terminal and the base station 210, and the like. It consists of antenna, transmitter, receiver, and power supply for wireless connection, and is in charge of matching function so that they can be interconnected. Since the components of the base station 210 are known to those skilled in the art, the detailed description is not provided herein.

The repeater minimizes transmission disturbances that occur when receiving the reception band signal and the shadow / square area (for example, buildings, department stores, malls, underground parking lots, subways, tunnels, etc.) where the coverage of the base station 210 cannot be secured smoothly. As a means for covering the above, it is to amplify the bidirectional signal to provide high quality service of a general base station level in a shadow area. The repeater is composed of a master unit 220 and slave units 230 and 240, the master unit 220 of the repeater is connected to the base station 210, a slave unit between the base station 210 and the master unit 220 230 and 240 are linked by optical cables. Repeaters may be used to cover shadows / squares in service areas or to extend coverage.

The base station 210 and the master unit 220 communicates using the existing method as it is. That is, the wavelength used when communicating from the base station 210 to the master unit 220 is λ ₁ (eg, 1310 nm), and the wavelength used when communicating from the master unit 220 to the base station 210 is λ ₄ ( 1550 nm). The wavelengths used between the slave units 230 and 240 are λ ₂ and λ ₃ (eg, 1310 and 1510 nm), but the transmission wavelength may be set differently in some cases (eg, wavelengths of 1510 and 1530 nm). That is, the wavelength that can be used for communication between the slave units 230 and 240 may be freely selected and used within the range of 1300 to 1700 nm. The slave unit 230 is directly connected to the base station 210 and the optical cable 250, and the other slave unit 240 is connected to the slave unit 230 and the master unit 220 with the optical cable 250.

3 is an exemplary signal flow diagram illustrating an internal configuration and a wavelength flow of the slave unit 300 of FIG. 2, wherein the slave unit 300 includes three WDMs 310, 330, and 340 and one circulator ( 320).

The first WDM 310 is an optical fiber type or microlens filter wavelength division multiplexer and performs a function of dividing / mixing a specific wavelength. That is, the WDM performs a function of adding a signal to be transmitted from each node or dropping a signal to be received. The optical communication method using WDM allocates light of different wavelengths to up and down signals and transmits them through the same optical fiber, which is almost similar to the frequency division multiplexing method of an electrical signal. In this method, by installing a wavelength multiplexing circuit at both ends of the optical cable and separating and extracting the up and down signals due to the difference in wavelength, communication can be carried out so that there is little leakage and mixing on the opposite side even if the optical cable is reflected in the middle. For example, a 1310 nm wavelength is separated from a 1550 nm wavelength, two separate signals are inputted at different wavelengths and transmitted through one channel, or an optical cable, and the integrated signal is received and then two wavelength divided multiplexers are used. Separate by signal. In addition, one optical cable can simultaneously send signals in opposite directions using a bidirectional coupler.

To implement optical communication using WDM smoothly, high gain and flat optical amplifiers, lasers that maintain accurate wavelengths, multiplexers and demultiplexers that combine or separate multiple wavelengths, and optical filters with low crosstalk are required. Modulation techniques for long distance transmission and distributed compensation techniques to further speed up a single channel are required.

Amplifying the weak signal without photoelectric conversion and restoring it to the original signal form is an indispensable element in high-speed optical communication. An erbium doped fiber amplifier (EDFA) is mainly used. Important variables for EDFA are gain flatness and output. If there is a gain difference depending on the wavelength, if the multi-stage amplification is performed, the power difference between the channels increases, and the signal of the other channel is weak because the amplifier output is saturated by the large signal. Therefore, it is desirable to select and communicate with a channel to be multiplexed by selecting a place where the gain of the amplifier is flat.

In addition, in order to maintain a constant wavelength spacing of each channel, there must be a laser diode (LD) operating at a desired wavelength, and a technique for continuously monitoring the wavelength of each LD and controlling it to not change is required. For this purpose, it is preferable to use LD (for example, Multiquantumwell DFB LD) which can select a wavelength of 40 channels or more at 0.8 nm intervals, and to determine the intensity of transmitted light by using an interferometer that transmits only for a wavelength of a predetermined interval. The current wavelength position of the method is adopted and used.

The method of implementing an arrayed waveguide grating (AWG) as a power line communication (PLC) circuit is a method of multiplexing optically combining wavelengths of multiple channels, each of which is modulated at a transmitter, or demultiplexing, which separates multiple transmitted channels by wavelength. As the number of channels increases, it is cheaper than other methods, and it is widely used in that it can be mass-produced once a specification is set. Therefore, it is very useful when branching / combining at an intermediate node or when the number of channels to be branched / combined increases. On the other hand, when the number of branching / coupling is small, a method using a fiber grating (Fiber Grating) manufactured to reflect only a specific wavelength is preferable. In addition, although optical loss was the main factor limiting the transmission distance in the optical communication around 1310 nm, as the EDFA is applied, chirp and dispersion of the LD are emerging as important factors for limiting the transmission distance. The chirp is a phenomenon in which the wavelength changes instantaneously with the change of the input current when LD is directly modulated, which causes the wavelength to become wider and the pulse is distorted according to transmission. In order to accomplish this, long-distance transmission uses a method of externally modulating a light source emitted from the LD without directly modulating the LD. A Mach-Zehnder interferometer mainly using LiNbO ₃ is used to realize such a modulation scheme.

The circulator 320 is connected to the first WDM 310 and performs a function of separating and demultiplexing bidirectional signals or merging remultiplexed bidirectional signals. The circulator 320 is an irreversible passive element composed of three or more ports. For example, when composed of three ports, the light component having a circulation structure such that the light input to the first port is output only to the second port and the light input to the second port is output only to the third port. The circulator 320 is applied to an optical fiber amplifier or bidirectional communication applied to a wavelength division multiplexing system.

The second WDM 330 is connected to the first WDM 310 and an external specific wavelength, and functions to multiplex or demultiplex the wavelength branched from the first WDM 310 and the external wavelength. Here, the second WDM 330 divides a desired wavelength in a communication line of a specific wavelength by using a spacing Spacing Fiber Biconical Tapered (FBT) type or a bandpass filter WDM. Other functions are the same as the first WDM 310.

The third WDM 340 is connected to the circulator 320 and the second WDM 330 and performs a function of splitting / mixing a specific wavelength. Here, the third WDM 340 uses an optical fiber type or microlens filter WDM, and only the connection relationship is different, and other functions are the same as the first WDM 310.

Hereinafter, an operation relationship of the optical communication system using the add / drop optical module according to the present invention will be described in more detail with reference to the accompanying drawings.

First, before describing the operation of the present invention, an optical communication system is constructed in which two slave units are connected between a base station and a master unit. Here, it is assumed that a slave unit installed close to a base station among two slave units is a first slave unit and a slave unit installed close to a master unit is a second slave unit. In addition, the wavelength transmitted from the base station to the master unit is λ _1, the wavelength transmitted from the master unit to the base station is λ ₄ , the wavelength transmitted from the first slave unit to the second slave unit is λ ₂ , and the first slave unit is transmitted from the first slave unit. Assume that the wavelength transmitted to the slave unit is λ ₃ .

The communication from the base station to the master unit uses λ ₁ , and the wavelength λ ₁ transmitted from the base station is branched by the first WDM and applied to the circulator. Wavelength that has passed through the circulator (λ ₁₎ is the wavelength (λ ₁₎ is applied to the second is applied to the slave unit, second slave unit via the second 3 WDM is sent to the master unit via the same procedure as the first slave unit do. The communication from the master unit to the base station uses λ ₄ , and the wavelength λ ₄ transmitted from the master unit passes through the third and second WDMs of the second slave and the third and second WDMs of the first slave. After passing the pass is transmitted to the base station.

In addition, the communication from the first slave unit to the second slave unit uses λ ₂ , and λ ₂ uses a second WDM among the wavelengths transmitted by the first WDM among the wavelengths transmitted from the base station to the first slave unit. It is used by dividing at regular intervals (for example, 40nm). Here, it is preferable that the second WDM uses a space FBT type or band filter WDM. The wavelength λ ₂ divided by the second WDM is applied to the second slave unit via the third WDM. In the second slave unit communicating with the first slave unit is the second use of the wavelength (λ ₃₎ which is applied via a circulator of the slave, and the second wavelength (λ ₃₎ which is applied via a circulator of the slave is the second It is applied to the third WDM of the first slave unit through the first WDM of the slave unit and transmitted to the circulator of the first slave unit.

The above description is only for explaining one embodiment, and the present invention is not limited to the above-described embodiment and can be variously changed within the scope of the appended claims. For example, the shape and structure of each component specifically shown in the embodiment of the present invention may be modified.

As described above, according to the optical communication system using the add / drop optical module according to the present invention, the slave unit is installed in the optical path connected to the master unit of the base station and the repeater. It can communicate without loss and can communicate with each other between slave units.

In addition, by installing a wavelength pass add / drop optical module in an optical path connected between an existing transmitting station or base station and a receiving station or repeater, the communication range can be expanded at a low price without the addition of the optical path and repeater. .

Claims (5)

In the optical communication system that provides a high quality communication service by connecting the base station and the master unit to provide a mobile communication service in the shaded / square area that the radio waves do not reach, and to extend the communication range, Located between the base station and the master unit includes a plurality of slave units capable of mutually communicating the communication wavelength of the base station and the master unit, and independently communicate with each other without control of the base station and the master unit, The communication wavelength between the base station and the master unit and the communication wavelength between the slave units are selected and used from 1300 nm to 1700 nm, Wavelength blocking to prevent interference of adjacent wavelengths in the communication between the base station and the master unit and the communication between the slave units may control the isolation ratio by using a fiber type or microlens type filter in each line. , The isolation ratio is an optical communication system using an add / drop optical module, characterized in that adopted in the range of 25 ~ 60dB. delete delete delete delete