RU2781917C1 - Apparatus and method for wayside communication - Google Patents

Abstract

FIELD: communication.

SUBSTANCE: invention relates to the field of automation, communications, and can be used in railway transport to ensure wayside communication. To realise the technical result, the apparatus includes two terminal stations A and B, 1+n wayside access nodes, and a fibre-optic communication line. Each terminal station comprises a control unit of the station duty officer, an Ethernet switch, and a station access apparatus containing a switching station and 1+n SFP modules for transmission at the wavelength thereof and a CWDM multiplexer/demultiplexer. Each wayside access node comprises two SFP modules, an electricity source, and a monophone apparatus. In the method, the monophone apparatus and the wayside access node are pre-activated; then an electric digital signal is generated on the control unit of the station duty officer A.

EFFECT: higher operating efficiency of wayside communication, increased transmission speed.

5 cl, 2 dwg

Description

The invention relates to the field of automation, communications and can be used in railway transport for the organization of haul communication and communication with the place of emergency recovery work, as well as for the organization of communication along transport routes, including pipelines.

Prior Art

Known patent of the Russian Federation for the invention No. 2719318, IPC H04V 10/25, "METHOD OF INFORMATION TRANSMISSION VIA FIBER-OPTIC COMMUNICATION LINES WITH DISTRIBUTED ACCESS NODES".

The technical result consists in reducing the losses of the FOCL energy budget, which ensures a significant reduction in the required number of optical fibers for connecting the end stations of the FOCL section with distributed access nodes and reducing the volume of FOCL station equipment. For this, optical switches are introduced, connected to the power supply outputs of the access nodes and performing the transmission of linear signals bypassing the access nodes when the power is turned off or connecting the linear signals of two directions of communication to the first and second ports of the access nodes when the power is on.

The disadvantage of this method is the use of SFP modules with a combined receiver/transmitter, which greatly reduces the ability to control power levels and sensitivity, because with a decrease in sensitivity (to protect against overexposure from the neighboring SFP module), the transmitter power will simultaneously decrease and the cost of the equipment will increase; involves the use of two wavelengths, which complicates the commissioning of the system.

Closest to the claimed invention is the patent of the Russian Federation for the invention No. 2713776 B61L 27/00, H04M 3/56 "SYSTEM OF DISTRIBUTION COMMUNICATION".

The station communication system contains station access devices installed at stations that limit the stage, intercom call devices, stage access devices interacting over a digital network using a primary digital channel in the E1 format, a fiber-optic communication line made on the basis of passive optical networks, in order to provide communication between access devices of the stage with access devices of the station, splitters are included in the optical fiber of the fiber-optic communication line, each station access device is made in the form of a primary multiplexer. The invention solves the problem of reducing the energy consumption of the power supply devices for access to distilleries.

The disadvantages of the proposed system are: the use of passive splitters, which leads to a rapid attenuation of the signal when taken to the side; the use of E1 multiplexing technology (time multiplexing), which does not allow data to be transmitted at a rate higher than 2 Mbps.

Disclosure of invention

The technical objective of this invention is

Improving the efficiency of loop communication at distances between terminal stations of more than 20 km.

Increasing the data transfer rate to enable the use of modern technologies.

Improving the consumption efficiency of optical fibers.

The set technical problem is solved due to the fact that the device for the organization of the spanning communication includes two terminal stations A and B, 1+n access nodes of the spanning and a fiber-optic communication line, which can be either two-fiber or single-fiber. Each terminal station contains a station attendant console unit and an L3 Ethernet switch and a station access device, which contains an L3 Ethernet switch, a switching station and 1+n SFP modules located in the L3 Ethernet switch, each of which transmits at its own length waves and CWDM multiplexer/demultiplexer. Each access node contains a pair of L3 Ethernet switches, two SFP modules, a power supply, an intercom and additional equipment. The hop communication device additionally contains 1+n OADM units (wave division multiplexing device), the number of which is always equal to the number of hop access nodes.

The method of operation of the device using a two-fiber fiber-optic communication line consists in the fact that the intercom and the access node are preliminarily activated. After that, an electrical digital signal is generated on the station A attendant console unit, which passes through the Ethernet switch L3 of the end station A, the Ethernet switch L3 as part of the station A access device, the switching station, where the signal is processed and a reverse electrical digital signal is generated, then this signal is transmitted back to the Ethernet switch L3 as part of the access device of station A and converted into an optical digital signal. Then this signal at a certain wavelength is transmitted to the CWDM - optical multiplexer / demultiplexer through the SFP module corresponding to the access node of the distillation to which the intercom is connected to which the call must be made. Then the multiplexer / demultiplexer combines the signal at this wavelength with signals at other wavelengths from other SFP modules into a common optical signal and transmits it to the optical fiber, which is used to transmit from terminal station A to the access node of the stage. After the transmitted signal at a certain wavelength in the common optical signal reaches the OADM block operating at the same wavelength, it is filtered in this OADM block from the common optical signal and transmitted to the SFP module directed towards end station A. Next this signal is fed to the L3 Ethernet switch of the access node, where the signal is converted into electrical digital and transmitted to the intercom and additional equipment if it is active. Then, by means of this intercom, a response electrical digital signal is generated and transmitted to the Ethernet switch L3 as part of the same access node of the distillation. There it is converted into an optical digital signal and through the SFP module directed towards the end station A, it gets to the corresponding OADM unit, through which it is added to the optical fiber, and it is transmitted from the intercom to the end station A. then this optical digital signal as part of a common optical signal is fed to the terminal station A multiplexer/demultiplexer, in which the common optical signal is divided into separate digital optical signals at different wavelengths, and the transmitted signal from the intercom at a certain length is fed to the corresponding SFP- module, the same one from which the signal was sent from terminal station A to the ferry access node. Then this signal is fed to the Ethernet switch L3 as part of the access device of the station end station A, where it is converted into an electrical digital signal. Next, an electrical digital signal is transmitted through the L3 Ethernet switch of terminal station A to the station attendant's console unit. Communication with the end station B occurs identically through the second SFP module of the access node of the stage. The rest of the signals in a common stream pass through the OADM blocks to their OADM block.

The method of operation of the device using a single-fiber fiber-optic communication line consists in the fact that the intercom and the access node are activated through the battery of the intercom. An electric digital signal is generated at the control panel unit of station A, which passes through the L3 Ethernet switch of terminal station A and is fed to the L3 Ethernet switch as part of the station A access device. Then the signal is transmitted to the exchange station of the station A access device, where the signal is processed and generating a reverse electrical digital signal. Then it is transmitted back to the Ethernet switch L3 as part of the access device of station A and converted into an optical digital signal. After that, this signal at a certain wavelength is transmitted to the CWDM through the SFP module corresponding to the access node of the stage, to which the intercom is connected, to which the call must be made. Then, by means of a multiplexer / demultiplexer, the signal at this wavelength is combined with signals at other wavelengths from other SFP modules into a common optical signal and transmitted to the optical fiber, which is used to receive / transmit the signal. After a signal at a certain wavelength as part of the common optical signal reaches the OADM block operating on the same pair of wavelengths used to organize communication between the station access device A and a specific access device, the stage, it is filtered in this OADM block from the common optical signal and transmitted to the SFP module directed towards the end station A. Then this signal is fed to the L3 Ethernet switch, where the signal is converted to electrical digital and transmitted to the intercom and additional equipment, if it is active. Then, by means of this intercom, a response electrical digital signal is generated and transmitted to the L3 Ethernet switch as part of the same access node, where it is converted into an optical digital signal and through the SFP module directed towards terminal station A is fed to the corresponding OADM unit, through which it is added to the optical fiber, and it is transmitted from the intercom to the end station A. Then this optical digital signal as part of the common optical signal is fed to the multiplexer / demultiplexer of the end station A, in which the common optical the signal is separated into separate digital optical signals at different wavelengths. The transmitted signal from the intercom at a certain length is fed to the corresponding SFP module, the same one from which the signal was sent from the terminal station A to the access node. Then this signal is fed to the Ethernet switch L3 as part of the access device of the station end station A, where it is converted into an electrical digital signal. Next, an electrical digital signal is transmitted through the L3 Ethernet switch of terminal station A to the station attendant's console unit. Communication with the end station B occurs identically through the second SFP module of the access node of the stage. The rest of the signals in a common stream pass through the OADM blocks to their OADM block.

Implementation of the invention

The proposed hop communication system based on CWDM (sparse wavelength division multiplexing) is a technology that allows simultaneous transmission of several information signals over a single optical fiber. The principle of this method is that each information stream is transmitted over one optical fiber at different wavelengths (at different carrier frequencies). The wavelengths used in CWDM 14 and 20 range from 1270 nm to 1610 nm in 20 nm steps. With the help of optical multiplexers, the streams are combined into one group optical signal, which is injected into the optical fiber. On the receiving side, the reverse operation is performed - demultiplexing, using optical demultiplexers.

The operation of the device for organizing hop communication 1 is based on the technology of spectral multiplexing of CWDM 14 and 20 optical channels and allows you to install up to 18 hop access nodes per pair of optical fibers as part of the main/local cable when using a two-fiber fiber-optic communication line with access organization in two directions.

The operation of the hop communication device 1 is based on the technology of spectral division multiplexing of CWDM 14 and 20 optical channels and allows you to install up to 9 hop access nodes per one pair of optical fibers as part of the trunk/local cable when using a single-fiber fiber-optic communication line and organizing access in two directions.

The proposed method and device provides data transmission in duplex mode for organizing a stage telephone connection, communication with a guarded railway crossing, communication with a place of emergency and restoration work, MTS, video surveillance, etc.

The device for distillation communication 1 provides the possibility of telephone conversations by connecting a universal distillation telephone TUP.ST01 or an analog handset TA.ST01.

Device 1 is designed for use on sections of railways of all categories.

SFP modules 15, 21, 22 and 27 (SFP transceivers) proposed for use in this system are compact optical transceivers that comply with the industry standard SFP.

Modifications of SFP modules 15, 21, 22 and 27 provide data transmission both over a copper UTP cable and over one or two single-mode or multi-mode optical fibers. SFP modules 15, 21, 22, and 27 can be used to operate at standard wavelengths from 850 to 1610 nm in networks with WDM, CWDM 14 and 20, or DWDM 14 and 20 WDM systems.

Optical CWDM 14 and 20 SFP modules 15, 21, 22 and 27 are designed to form and receive signals at wavelengths of the CWDM range (from 1270 to 1610 nm with a step of 20 nm). For the formation of duplex data transmission channels in the CWDM system, 14 and 20 modules are used in pairs.

The transmitters of the modules are equipped with lasers of various types depending on the speed of the transmitted signal.

A demultiplexer is a hardware device designed to switch a signal from one information input to one of the information outputs. Thus, a demultiplexer is functionally the opposite of a multiplexer.

A multiplexer is a device that has several signal inputs and one output. The multiplexer allows you to transmit a signal from one of the inputs to a common output, combining signals from different inputs on it

Optical budget - the predicted sum of optical signal losses on all FOCL components.

CWDM 14 and 20 (Coarse Wavelength Division Multiplexing) - multiplexing with sparse spectral division. In other words, this is a technology that allows you to simultaneously transmit several information channels over one optical fiber at different carrier frequencies. The CWDM 14 and 20 wavelength grid is in the range from 1270 nm to 1610 nm in 20 nm steps. The principle of operation of CWDM 14 and 20 is simple. Each transceiver module generates a signal at a specific frequency. Before getting into the optical fiber, the signal from the modules is combined by a multiplexer and transmitted to the fiber. At the receiving end, the signal is split by a demultiplexer. In order for the optical network from the bus topology to be converted to the star topology, the demultiplexer must not only receive the signal at a given length, but also further pass the signal without changing it. OADM 6 and 7 are used for this.

OADM 6 and 7 (Optical Add Drop Multiplexor) is an optical input-output multiplexer of CWDM 14 and 20 systems that extracts a signal at a given wavelength from an optical line, and passes all other radiation unchanged.

In Fig.1. A diagram of a device for organizing a loop connection using a two-fiber fiber-optic communication line is presented.

In Fig.2. A diagram of a device for organizing a loop connection using a single-fiber fiber-optic communication line is presented.

The device for the organization of the spanning communication 1 includes two terminal stations A and B 2 and 3, 1+n access nodes of the spanning 4, 5 and a fiber-optic communication line - two-fiber or single-fiber. Each terminal station 2 and 3 contains a station attendant console unit 10 and 16 and an Ethernet switch L3 11 and 17 and a station access device 8 and 9, which contains an Ethernet switch L3 13 and 19, a switching station 12 and 18 and 1+n SFP modules 15 and 21 located in the Ethernet switch L3 13 and 19, each of which transmits at its own wavelength and CWDM multiplexer / demultiplexer 14 and 20. Each access node, spanning 4 and 5 contains a pair of Ethernet switches L3 23 and 28 , two SFP modules 22 and 27, a power supply 26 and 31, an intercom 25 and 30, and additional equipment 24 and 29. The device for organizing hop communication 1 additionally contains 1 + n OADM blocks 6 and 7 (length division multiplexing device wave), the number of which is always equal to the number of access nodes distillation 4 and 5 (see figure 1).

The method of operation of the device using a two-fiber fiber-optic communication line consists in the fact that the intercom 25 and the distillation access node 4 are pre-activated. L3 11 of terminal station A 2, Ethernet switch L3 13 as part of the station access device A 8, switching station 12, where the signal is processed and a reverse electrical digital signal is generated, then this signal is transmitted back to the Ethernet switch L3 13 as part of the station access device And 8 and convert an optical digital signal in it. Then this signal at a certain wavelength is transmitted to the CWDM - optical multiplexer/demultiplexer 14 through the SFP1 module 15, corresponding to the access node 4, to which the intercom 25 is connected, to which the call must be made. Then the multiplexer/demultiplexer 14 combines the signal at this wavelength with signals at other wavelengths from other SFP modules 15 into a common optical signal and transmits it to the optical fiber, which is transmitted from the terminal station A 2 to the access node of the stage 4. After Once the transmitted signal at a certain wavelength in the common optical signal reaches the OADM 6 operating at the same wavelength, it is filtered in this OADM 6 block from the common optical signal and transmitted to the SFP1 module 22 directed towards end station A 2. Next, this signal is fed to the Ethernet switch L3 23 of the access node of the distillation 4, where the signal is converted into electrical digital and transmitted to the intercom 25 and additional equipment 24 if it is active. Then, through this intercom 25, a response electrical digital signal is generated and transmitted to the Ethernet switch L3 23 as part of the same access node of the stage 4. There it is converted into an optical digital signal and through the SFP1 module 22 directed towards the end station A 2 is fed to the corresponding OADM 6 block, through which it is added to the optical fiber, and it is transmitted from the intercom 25 to the end station A 2. Then this optical digital signal as part of a common optical signal is fed to the multiplexer / demultiplexer 14 of the end station A 2, in which the common optical signal is divided into separate digital optical signals at different wavelengths, and the transmitted signal from the intercom 25 at a certain length is fed to the corresponding SFP1 module 15, the same from which the signal was sent from terminal station A 2 to the access node 4. Then this signal is sent to Ethernet switch L3 13 as part of the access device of the station end station A 8, where it is converted into an electrical digital signal. Further, the electrical digital signal is transmitted through the Ethernet switch L3 11 of the end station A 2 to the control unit of the station attendant 10. Communication with the end station B occurs identically through the second SFP1 module 22 of the access node of the stage 4. its block OADM (see Fig. 1).

The method of operation of the device 1 using a single-fiber fiber-optic communication line consists in the fact that the intercom 25 and the distillation access node 1 4 are activated beforehand through the battery 26 of the intercom 25. On the control unit of the attendant 10 at station A 2, an electric digital a signal that passes through the Ethernet switch L3 11 of the end station A 2 and is fed to the Ethernet switch L3 13 as part of the access device of the station A 8. Then the signal is transmitted to the switching station 12 of the access device of the station A 8, where the signal is processed and a reverse electrical digital signal. Then it is transmitted back to the Ethernet switch L3 13 as part of the station access device A 8 and converted into an optical digital signal. After that, this signal at a certain wavelength is transmitted to the CWDM 14 through the SFP1 module 32, corresponding to the access node of the stage, to which the intercom 25 is connected, to which the call must be made. Then, by means of the multiplexer/demultiplexer 14, the signal at this wavelength is combined with signals at other wavelengths from other SFP(2-9) modules 32 into a common optical signal and transmitted to the optical fiber, which is used to receive/transmit the signal. After the signal at a certain wavelength as part of the common optical signal reaches the OADM 6 block operating on the same pair of wavelengths used to establish communication between the access device and the station A 8, it is filtered in this OADM 6 block from the common optical signal and transmitted to the SFP10 module 34, directed towards the end station A 2. then this signal is fed to the Ethernet switch L3 23, where the signal is converted into electrical digital and transmitted to the intercom 25 and additional equipment 24, if it is active. Then, using this intercom 25, a response electrical digital signal is generated and transmitted to the Ethernet switch L3 23 as part of the same access node of the stage 4, where it is converted into an optical digital signal and through the SFP10 module 34 directed towards the end station A 2 is fed to the corresponding OADM 6 block, through which it is added to the optical fiber, and it is transmitted from the intercom 25 to the end station A 2. Then this optical digital signal as part of a common optical signal is fed to the multiplexer / demultiplexer 14 of terminal station A 2, in which the common optical signal is divided into separate digital optical signals at different wavelengths. The transmitted signal from the intercom 25 at a certain length is fed to the corresponding SFP1 module 32, the same one from which the signal was sent from the terminal station A 2 to the access node 4. Then this signal is fed to the Ethernet switch L3 13 as part of the device access station 8 end station A 2, where it is converted into an electrical digital signal. Next, the electrical digital signal is transmitted through the Ethernet switch L3 11 of the terminal station A 2 to the control unit of the station attendant 10. Communication with the terminal station B 3 occurs identically through the second SFP10 module 34 of the access node of the stage 4. The rest of the signals pass through the blocks in a common stream OADM to its OADM block.

Differences of the single-fiber version:

Due to the fact that a single-fiber fiber-optic communication line is used, it is necessary to use signals of different wavelengths for receiving and transmitting from / to the terminal station to / from the corresponding access node, therefore, you can install no more than 9 access nodes on one fiber .

Wavelengths for reception and transmission are used in pairs (any). For example, on access node 1 will use SFP modules transmitting at a wavelength of 1470. At the end stations, SFP modules with a different wavelength, for example, 1350, will receive this signal from these SFP modules and transmit it back. a different pair of waves will be used, for example, 1610 for the ferry access node and 1510 for the station.

Due to the need to use different wavelengths for receiving and transmitting, wavelengths are used in pairs. So, to organize communication from terminal stations A and B with access node 1, a pair of waves λ1 and λ2 is used. SFP modules operating at wavelength λ1 are installed at the stations, and SFP modules operating at wavelength λ2 are installed in access device stage 1. To organize communication with access device stage 2, another pair of waves, λ3 and λ4, will be used, which differs from already used wavelengths.

The advantages of the proposed solution are:

economy of optical fibers - the spectral multiplexing system allows transmitting up to 9 duplex channels with a capacity of up to 1.25 Gbit / s per channel on one fiber;

independence from power supply - power is needed only for active equipment;

no crash problems, reboots, etc.;

no need to organize permanent access to the locations of the system elements - there are OADM modules designed for placement in optical boxes;

reducing the level of influence of the "human factor" - the absence of active components that require configuration, management, etc.;

a significant reduction in the cost of ownership - a decrease in the level of operating costs;

relatively low cost and the possibility of refusing equipment of the aggregation level;

the maximum operating range is 80 kilometers or more;

transparency for all data transfer protocols;

availability of various types of equipment for mounting in various conditions: in a rack, in a sleeve, on a wall;

In the mode of organization of hop communication, the proposed system provides the ability to establish connections from several linear access points and conduct collective negotiations.

All the above descriptions of the functioning of the device confirm the fulfillment of the technical task of this invention, namely, increasing the efficiency of the loop communication at distances between terminal stations of more than 20 km, increasing the data transfer rate to enable the use of modern technologies, increasing the efficiency of consumption of optical fibers.

Industrial Applicability

All of the above speaks of the industrial applicability of a device for organizing a line connection and a method for organizing a line connection.

List of positions.

1. Device for organizing a line connection

2. End station A

3. Terminal B

4. Distillation access node 1

5. Distillation access node 2

6. OADM block

7. OADM block

8. Station access device A

9. Station access device B

10. Station attendant console block

11. Ethernet switch L3

12. Switching station

13. Ethernet switch L3

14. CWDM optical multiplexer/demultiplexer

15. SFP access device module of station A (for two-fiber scheme)

16. Station attendant console block

17. Ethernet switch L3

18. Switching station

19. Ethernet switch L3

20. CWDM optical multiplexer/demultiplexer

21. SFP module of station access device B (for two-fiber)

22. SFP module of the access node of the stage 1 (for a two-fiber scheme)

23. Ethernet Switch L3

24. Additional equipment

25. Intercom

26. Battery

27. SFP module of the access node of the stage 2 (for a two-fiber scheme)

28. Ethernet Switch L3

29. Additional equipment

30. Intercom

31. Battery

32. SFP (1-8) modules of station access devices A and B (for a single-fiber scheme)

33. SFP (18) station access device module B (for single-fiber scheme)

34. SFP (10-17) hop access node modules (for single-fiber scheme)

Claims (5)

1. An end-to-end communication device containing two terminal stations A and B, connected to each other and to 1 + n access nodes through a fiber-optic communication line, each end station contains a station attendant console unit connected through a switch and a multiplexer with station access device, and each stage access node contains a switch, a power supply, an intercom, characterized in that the switch of each terminal station is made in the form of an Ethernet switch connected to a data transmission network for operational and technical purposes, and each access device is station implemented as a switching station and an optical sparse wavelength division multiplexer/demultiplexer (CWDM) connected to 1+n SFP modules of an Ethernet switch, with each SFP module configured to transmit at its own wavelength for communication with each hop , while at each distillation node additional The OADM block has been introduced, made in the form of a multiplexing device (CWDM), connected to a fiber-optic communication line, in each access node, the spanning switch is made in the form of an Ethernet switch connected to the intercom, while the Ethernet switch contains a pair of SFP modules connected to the OADM and configured to communicate with end stations A and B. 2. The device according to p. 1, characterized in that the fiber-optic communication line is made in the form of a two-fiber. 3. The device according to claim 1, characterized in that the fiber-optic communication line is made in the form of a single-fiber, and the value of 1 + n access nodes of the distillation is less than or equal to 9. 4. The method of hop communication, including two end stations A and B, connected to each other and with 1 + n hop access nodes via a fiber-optic communication line, implemented according to claim 1, which consists in pre-activating the intercom and calling device and distillation access node, by supplying power to it from the intercom, after that, an electrical digital signal is generated on the control unit of the station A duty officer, which passes through the Ethernet switch to the switching station of the station A access device, where the signal is processed and a reverse electrical signal is generated a digital signal that is converted into an optical digital signal, and at a certain wavelength is transmitted to an optical multiplexer / demultiplexer (CWDM) through an SFP module corresponding to the access node of the distillation to which the activated intercom is connected, then through the multiplexer / demultiplexer ( CWDM) combine the signal to this wavelength with signals at other wavelengths from other SFP modules into a common optical signal and transmit it over a fiber optic communication line, after the transmitted optical signal at a certain wavelength as part of the common optical signal reaches the OADM block operating on that the same wavelength, it is filtered and transmitted to the SFP module directed towards end station A, then this signal is fed to the Ethernet switch, where it is converted into electrical digital and transmitted to the intercom, a response is generated on the intercom. electric digital signal and transmit it to the Ethernet switch as part of the same access node, where it is converted into an optical digital signal and fed through the SFP module directed towards end station A to the corresponding OADM unit, through which it is added to the fiber - an optical communication line through which the signal is transmitted to the terminal station A, where this optical digital signal as part of a common optical signal is fed to the terminal station A multiplexer/demultiplexer, in which the common optical signal is divided into separate digital optical signals at different wavelengths, and the transmitted signal from the intercom at a certain length is fed to the corresponding SFP- module, then this signal is converted into an electrical digital signal and transmitted through the Ethernet switch of terminal station A to the control panel unit of the station attendant, while communication with terminal station B occurs identically through the second SFP module of the access node of the stage. 5. The method of hopping communication, including two terminal stations A and B, connected to each other and with 1+n hopping access nodes via a fiber-optic communication line, implemented according to claim 1, which consists in pre-activating the intercom and calling device and a distillation access node, by supplying power to it from the intercom, an electrical digital signal is generated on the control unit of the station A attendant, which is transmitted through the Ethernet switch and the station A access device to the switching station of the station A access device, where the signal is processed and a return electrical digital signal is generated, then this signal is converted into an optical digital signal in the access device of station A, after which it is transmitted at a certain wavelength to the CWDM optical multiplexer / demultiplexer via the SFP module corresponding to the access node, to which the intercom is connected device to which make a call, by means of a multiplexer / demultiplexer, they combine the signal at a given wavelength with signals at other wavelengths from other SFP modules into a common optical signal and transmit it to the fiber optic communication line used to receive / transmit the signal, the transmitted optical signal at a certain wavelength at the input of the wave division multiplexing device operating on the same pair of wavelengths is filtered in the OADM block from the common optical signal and transmitted to the SFP module directed towards the end station A, then this signal is converted into electrical digital and transmitted to intercom, where a response electrical digital signal is generated, converted into an optical digital signal, and through the SFP module directed towards terminal station A, it is fed to the corresponding OADM unit, through which it is added to the fiber optic communication line, through which transmit from the intercom to terminal station A, then this optical digital signal as part of a common optical signal is fed to the multiplexer / demultiplexer of terminal station A, in which the common optical signal is divided into separate digital optical signals at different wavelengths, and the transmitted signal from the intercom at a certain length is fed to the corresponding SFP module, the same one from which the signal was sent from the terminal station A to the access node, then this signal is converted into an electrical digital signal and through the Ethernet switch of the terminal station A is fed to the control unit of the station attendant, communication with the terminal station B occurs identically through the second SFP module of the access node of the stage.

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