JP2023046243A - Optical add/drop multiplexer branching unit, communication system, and signal transmission method - Google Patents

Abstract

To provide a communication system, an optical add/drop multiplexer branching unit, and a signal transmission method that reduce the number of fiber pairs of a branching circuit terminal station and guarantee traffic signals to be received by a target terminal station only.SOLUTION: A communication system comprises an optical add/drop multiplexer branching unit 4 for supporting a backbone circuit and a branching circuit so that the circuits use the same number of fiber pairs, the optical add/drop multiplexer branching unit processing traffic signals that are output from respective terminal stations and carried in different subbands. A target traffic signal and non-target traffic signals in a multiplexed signal after processing are carried in different subbands. The respective non-target traffic signals are carried in the same subband. Thereby, crosstalk of the same frequency is formed in the subband and terminal stations receiving the multiplexed signal after processing are inhibited from acquiring traffic information from the respective non-target traffic signals, which guarantees safety of traffic information transmission between the respective terminal stations.SELECTED DRAWING: Figure 6

Description

TECHNICAL FIELD The present application relates to the field of submarine communication technology, and more particularly to an optical add/drop multiplexing/branching unit, a communication system, and a signal transmission method.

Signal transmission lines in submarine optical fiber communication systems include backbone lines and branch lines, where backbone line means the signal transmission line between two trunk line terminal stations located on the ground, and branch line Refers to a signal transmission path between a located trunk line terminal station and a branch line terminal station, and as shown in FIG. It is necessary to separate or multiplex signals output from each terminal station in an optical add/drop multiplexer branching unit (OADM BU). A signal transmission path between terminal A and terminal B is a backbone line, terminal C is a branch line terminal, and signal transmission between OADM BU and terminal C A path is a branch line.

FIG. 2 is a schematic diagram of signal transmission from terminal station A to terminal station B. The transmission signal to each terminal station is
Express (pass-through) signals, which can be divided into four types, each carrying communication traffic from backbone line terminator to backbone line terminator, shown schematically in rectangles filled with horizontal lines, as shown in FIG. , a drop signal carrying communication traffic from the backbone line to the branch line shown schematically by the rectangles filled with diagonal lines from upper right to lower left, the branch line to the backbone shown schematically by the rectangles filled with diagonal grids An Add signal carrying communication traffic up to the line, and a Loading signal schematically shown by a black rectangle. The Loading signal is a loading signal transmitted from the backbone line and the branch line terminal station. A loading signal is a signal for balancing power, does not carry traffic, and may be noise light or continuous light. The carrier wavelengths of the Drop signal and the Add signal are usually the same.

As shown in FIG. 2, the signal output from terminal A enters the OADM BU through the input interface and is split into two by a splitter, one of which is a branch line. , the drop signal is completely received and restored by the terminal station C, and the download signal is blocked by one band block filter (BBF), and the remaining pass-through signal and branch Add signal are multiplexed by a coupler, output from the output interface, and transmitted to the terminal station B. When a repeater is applied to the branch line, a loading signal is input together with the add signal in order to balance the input power of the repeater. , BPF) and passed through the band-pass filter is combined with the pass-through signal and output.

As shown in Figure 2, for one fiber pair in the backbone line, two corresponding fiber pairs need to be placed in the branch lines, one fiber pair from end station A through the OADM BU. Complete signal download (Drop) and signal upload (Add) to end station C, and another fiber pair to complete signal download (Drop) and signal upload (Add) from end station B to end station C via OADM BU Add). That is, for the fiber pairs of the backbone line required to simultaneously support two-way communication between terminal A, terminal B, and terminal C, correspondingly double the number of fiber pairs of the backbone line. A fiber pair must be placed in the branch line. Doubling the number of fiber pairs in the branch line, on the one hand, increases the cost significantly, and on the other hand, the number of fiber pairs required in the branch line is less than the fiber that can be accommodated in conventional submarine cables and underwater optical repeaters. Since the maximum number of pairs (eg, up to 16 fiber pairs can be supported in conventional submarine cable systems) may be exceeded, the branch lines have no accompanying underwater products.

In addition, the OADM BU shown in FIG. 2 also has an information transmission security problem. As shown in FIG. 2, the pass-through signal carrying communication information between terminal A and terminal B is downloaded to terminal C together with the download signal. Since communication information with the terminal station B can be intercepted, protection against wiretapping cannot be achieved.

FIG. 3 is a schematic diagram of signal transmission supporting two-way communication between end stations A and B and C simultaneously using only one fiber pair for the branch line. The traffic bandwidth is such that it carries the communication traffic between end office A and end office C, the communication traffic between end office A and end office B, and the communication traffic between end office B and end office C. , are divided into three subbands a, B, and c, respectively. The optical signals a _E , B _E , and c _E output from the terminal station B enter the OADM BU node, then filter B (for blocking sub-band B) and filter A (for blocking sub-band a). to block traffic subbands _aE and _BE, respectively, and to isolate subband _cE , which is transmitted to terminal C. However, after entering the OADM BU node, the signals a _W , B _W , and c _W output from the terminal A have their sub-band c _W cut off by the filter C, and are transmitted to the terminal C. _W and the subband _BW where the target terminal station is the terminal station B are left, and after being multiplexed with the subband _cE by one multiplexer A, enter the downstream (Drop) optical fiber A of the branch line, It is possible to realize the transmission of the traffic of two trunk line terminals to the branch line terminal through one optical fiber. The transmission process from station C to station A and station B in the reverse direction is as follows. The optical signals a _S , B _S , and c _S output by the upstream (Add) optical fiber B of the branch line pass through the filter B, the sub-band B _S is cut off, and the sub-band a is transmitted to the terminal station B. _S and subbands c _S to be sent to terminal A are separated and combined by combiner B to filter C and D (to block subband a and subband c) in the optical fiber of the backbone line from terminal A. ) and then transmitted together to terminal _B and terminal A, where the signal transmitted to terminal A passes through filter B again. As a result, subband _BW is cut off, subbands _aS and _cS are separated, and are combined with subband _BE from terminal station B by multiplexer C and then transmitted to terminal station A together. , thereby realizing that the branch line completes the signal transmission from the branch line terminal station to the two trunk line terminal stations through one optical fiber.

In submarine cable communication systems, optical repeaters operate in a constant excitation current mode, usually in an extremely saturated operating state, so that the output power remains constant even if the input power fluctuates within a given range. , which exhibits some self-healing capability, which can come at the cost of non-linear transmission as the number of channels/wavelengths input to the repeater is reduced, as the output power of the remaining wavelengths increases. There was a problem. In the signal transmission process as shown in FIG. 3, in order to balance the single-wave output power of the repeater, the non-target station traffic sub-bands are combined with the useful traffic sub-bands into one complete Bandwidth traffic signals are constructed and sent together to the target end station, specifically, backbone line traffic (traffic carried by the _BW sub-band) along with drop line traffic (a _W and c _E ). The branch line end office can receive the backbone line signal for transmission to the end office. Even if it is possible to separate the signal to be received by placing a filter device at the branch line terminal, the difficulty of replacing the terminal equipment is low, so there is a risk that the signal transmitted on the backbone line will be tapped. still exists. Similarly, since the trunk line terminal receives not only backbone line traffic (B _W or B _E ) but also branch line traffic (a _S and c _S ), the branch signal is also sent to the trunk line terminal. There is a risk of being intercepted.

Compared to using the same traffic wavelength for forward transmission (uplink) and reverse transmission (downlink) between two bidirectional communication terminals, the trunk line Different wavelengths/subbands can carry upstream and downstream traffic signals used for communication between an end station and a drop line end station. As a schematic diagram of the transmission process of signals between terminals as shown in FIG. _A and Y _B ) are used to carry only the communication traffic between station A and station B, and carry only part of it, the rest of the communication traffic being carried on subband X or Z (X _A from west to east, Z _B from east to west). At the same time, subbands _ZA and _ZC are also used to carry upstream traffic signals between stations A and C and downstream traffic signals between stations B and C, respectively. , subbands X _C and X _B are used to carry downstream traffic signals between stations A and C and upstream traffic signals between stations B and C, respectively. The spectral widths of sub-band X and sub-band Z need to be set to be the same, but the starting point positions of the wavelengths are different. Sub-band _YC is a loading signal transmitted from station C, used to balance the power of the branch lines, and carries no traffic.

After adopting the above arrangement for sub-band traffic, the traffic signals transmitted from terminal A and terminal B to terminal C are loaded into different sub-bands, respectively. After being wavelength multiplexed with band _YC , it can be transmitted on the same optical fiber on the branch line. Also, after downloading (e.g., Z _A ) a branch traffic signal transmitted from terminal A to terminal C, the subband (Z _C ) carrying the branch traffic signal is sent from terminal C to Since it is used again to carry the added signal to be transmitted to terminal B, the newly carried signal will also collide in wavelength with the through signal (e.g., X _A +Y _A ) transmitted on the backbone line. There is no In this way, by using the number of fiber pairs in the branch line that matches the number of fiber pairs in the backbone line, two-way communication with terminal station A and terminal station B is realized simultaneously with terminal station C, and , traffic signals are not sent to non-target terminals, which can ensure the security of information transmission.

However, in the signal transmission system as shown in FIG. 4, the uplink traffic and downlink traffic of the same terminal station are loaded in different subbands, which increases the complexity of system configuration and network management. In scenes where multiple connections exist, system configuration and network management become more complicated.

The present application provides an optical add/drop multiplexing branch, a communication system and a signal transmission method to reduce the number of fiber pairs in a branch line terminal, so that the traffic signal output from the terminal is reduced to the target terminal. can be guaranteed to be received only by

In a first aspect, a communication system according to an embodiment of the present application includes a plurality of terminal stations including two trunk line terminal stations and at least one branch line terminal station,
traffic signals are transmitted between the two trunk line terminals and between the at least one branch line terminal and the two trunk line terminals;
a multiplexed signal output from each terminal station of the plurality of terminal stations is processed by a corresponding optical add/drop multiplexing/branching unit to obtain a processed multiplexed signal to be transmitted to the other terminal station;
the multiplexed signal output from each terminal includes a plurality of traffic signals carried in different subbands;
The optical add/drop multiplexing/branching unit includes a plurality of demultiplexers, a plurality of filters, and a plurality of multiplexers, and the plurality of demultiplexers, the plurality of filters, and the plurality of multiplexers each of said processed combined signals obtained by being processed by a device includes a targeted traffic signal and at least two non-targeted traffic signals, said targeted traffic signal and said at least two non-targeted traffic signals being different sub-signals; carried in a band, the at least two non-targeted traffic signals carried in the same subband, the directions of transmission of the at least two non-targeted traffic signals being opposite;
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.

In one implementation, the combined signal output from each terminal station further includes a loading signal for balancing the optical power of the plurality of traffic signals in the combined signal.

In one implementation, the sum of the optical power spectral densities of said at least two non-targeted traffic signals equals the optical power spectral density of said targeted traffic signal.

In one implementation, the optical powers of said at least two non-targeted traffic signals are equal.

In one implementation, at least one of said sub-bands includes an idle sub-band for carrying an extra signal corresponding to a first target sub-band, said excess signal being of said first target sub-band. A traffic signal that exceeds the bandwidth.

In one implementation, the idle subband and the first target subband are adjacent or spaced apart from each other.

In one implementation, when said at least one branch line terminal communicates with only one said trunk line terminal, said sub-band is a sub-band between said at least one branch line terminal and one said trunk line terminal. divided based on traffic signals transmitted between and traffic signals transmitted between said two trunk end stations;
A traffic signal transmitted between said at least one branch line terminal station and one said trunk line terminal station and a traffic signal transmitted between two said trunk line terminal stations are carried in different said subbands. be done.

In one implementation, the plurality of filters employ reconfigurable wavelength blockers.

In one implementation, the plurality of filters employs band-stop filters with the same or different parameters, or the plurality of filters employs a combination of band-stop and band-pass filters, each The parameters of the filters may be the same or different.

In a second aspect, a communication system according to an embodiment of the present application includes a plurality of terminal stations including two trunk line terminal stations and at least one branch line terminal station,
traffic signals are transmitted between the two trunk line terminals and between the at least one branch line terminal and two trunk line terminals;
A multiplexed signal output from each terminal station of a plurality of terminal stations is processed by a corresponding optical add/drop multiplexing/branching unit, and a processed multiplexed signal transmitted to the other terminal station is acquired,
the multiplexed signal output from each terminal includes multiple traffic signals carried in different subbands,
The optical add/drop multiplexing/branching unit includes a plurality of wavelength selective switches for demultiplexing and filtering the combined signal, and a plurality of multiplexers. Each of the resulting combined signals processed by the waver includes a targeted traffic signal and at least two non-targeted traffic signals, the targeted traffic signal and the at least two non-targeted traffic signals in different subbands. carried, the at least two non-targeted traffic signals carried on the same subband, the directions of transmission of the at least two non-targeted traffic signals being opposite;
The target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal match among the combined signals after processing,
A non-target traffic signal means a traffic signal among the processed multiplexed signals for which the corresponding target terminal station does not match the terminal station that receives the processed multiplexed signal.

In a third aspect, an optical add/drop multiplexing/branching unit according to an embodiment of the present application includes multiple demultiplexers, multiple filters, and multiple multiplexers,
the plurality of duplexers are connected to signal output interfaces of corresponding terminal stations;
the plurality of multiplexers are connected to signal input interfaces of corresponding terminal stations;
The processed combined signal obtained by processing the multiplexed signal input to the optical add/drop multiplexing/branching unit by the plurality of demultiplexers, the plurality of filters, and the plurality of multiplexers, a targeted traffic signal and at least two non-targeted traffic signals, wherein the targeted traffic signal and the at least two non-targeted traffic signals are carried on different subbands, and the at least two non-targeted traffic signals are carried on the same subband. carried, the directions of transmission of the at least two non-targeted traffic signals are opposite;
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal for which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.

In a fourth aspect, an optical add/drop multiplexing/branching unit according to an embodiment of the present application includes a plurality of wavelength selective switches and a plurality of multiplexers,
input terminals of a plurality of wavelength selective switches are connected to signal output interfaces of corresponding terminal stations;
output terminals of the plurality of wavelength selective switches are respectively connected to input terminals of the plurality of multiplexers,
The output terminals of the multiplexers are connected to the signal input interfaces of the corresponding terminals,
The wavelength selective switch is used to demultiplex and filter the multiplexed signal,
A multiplexed signal obtained by processing a multiplexed signal input to an optical add/drop multiplexing/branching unit by a plurality of wavelength selective switches and a plurality of multiplexers is a target traffic signal and at least two non-multiplexers. comprising a targeted traffic signal, the targeted traffic signal and the at least two non-targeted traffic signals carried on different subbands, the at least two non-targeted traffic signals carried on the same subband, and the at least two non-targeted traffic signals the direction of transmission is opposite,
The target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal match among the combined signals after processing,
A non-target traffic signal means a traffic signal for which a corresponding target terminal station and a terminal station receiving the processed combined signal do not match among the processed combined signal.

In a fifth aspect, the signal transmission method applied to the communication system in the first aspect or the second aspect according to the embodiment of the present application comprises:
dividing a total bandwidth by the terminal into a specified number of subbands;
a step of the terminal station carrying a traffic signal and a loading signal to be output in different subbands to obtain a combined signal;
the optical add/drop multiplexing/branching unit processing the multiplexed signal to obtain a processed multiplexed signal;
the optical add/drop multiplexing/branching unit transmitting the processed multiplexed signal to each of the terminal stations opposite to the terminal station.

As can be seen from the above, the present application provides a communication system, an optical add/drop multiplexing branch and a signal transmission method, in order to support using the same number of fiber pairs for the backbone line and the branch line, an optical Traffic signals carried in different subbands output from each end office can be processed by the add/drop multiplexing branch. Also, the targeted traffic signal and the non-targeted traffic signals in the processed combined signal obtained by the processing of the optical add/drop multiplexing/branching unit are carried in different subbands, and each non-targeted traffic signal is carried in the same subband. band, thereby creating same-frequency crosstalk in the subbands, and the end stations receiving the processed combined signals cannot obtain traffic information from their respective non-targeted traffic signals. , to ensure the security of traffic information transmission between terminals.

Hereinafter, in order to explain the technical structure of the present application more clearly, the drawings necessary for describing the embodiments will be briefly introduced. You can also get other drawings by
1 is a schematic structural diagram of an existing submarine optical fiber communication system according to the present application; FIG. 1 is a schematic diagram of signal transmission from an existing terminal station A to a terminal station B according to the present application; FIG. 1 is a schematic diagram of signal transmission simultaneously supporting two-way communication between end office A and end office B with end office C using only one fiber pair in an existing branch line according to the present application; FIG. FIG. 2 is a schematic diagram of signal transmission in which existing terminal station A and terminal station B perform two-way communication with terminal station C according to the present application; 1 is a schematic structural diagram of a communication system according to an embodiment of the present application; FIG. 1 is a schematic diagram of signal transmission in a communication system according to an embodiment of the present application; FIG. FIG. 4 is a schematic structural diagram of an initial sub-band according to an embodiment of the present application; FIG. 4 is a schematic structural diagram after reconstruction of sub-bands according to an embodiment of the present application; FIG. 4 is a schematic structural diagram after reconstruction of sub-bands according to an embodiment of the present application; 1 is a schematic diagram of signal transmission in a communication system according to an embodiment of the present application; FIG. 1 is a schematic diagram of signal transmission in a communication system according to an embodiment of the present application; FIG. 1 is a schematic diagram of signal transmission in a communication system according to an embodiment of the present application; FIG.

The following clearly and completely describes the technical structure according to the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. is only part of Any other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

FIG. 5 is a schematic structural diagram of a communication system according to an embodiment of the present application, which may be applied to submarine optical fiber communication, or may be applied to other communication scenes, but is not listed here. . As shown in FIG. 5, the communication system includes a first backbone terminal station 1,
It includes a second backbone terminal station 2, N branch line terminal stations 3, and M cascaded optical add/drop multiplexing branches 4, where N=M. A signal transmission path between the first trunk line terminal station 1 and the second trunk line terminal station 2 is a backbone line, and M optical add/drop multiplexing/branching units 4 and N optical add/drop multiplexing branches 4 and N The signal transmission path between the branch line terminal station 3 is a branch line, and the signals output from the first trunk line terminal station 1, the second trunk line terminal station 2, and the N branch line terminal stations 3 are transmitted. Each of them passes through the corresponding optical add/drop multiplexing/branching units in the M optical add/drop multiplexing/branching units 4 connected in cascade, acquires the processed signal, and transmits it to the target terminal station.

Signals transmitted between terminal stations in FIG. 5 will be described using FIG. 6 as an example. As shown in FIG. station 2, branch line terminal station 3 (which can be any one of the N branch line terminal stations in FIG. 5), and optical add/drop multiplexing/branching section 4 (M (can be any one of the optical add/drop multiplexing/branching units), and in this embodiment, the traffic signal between each terminal station is limited to have a corresponding relationship with the signal transmission direction. However, the signal transmission direction can be explained by the output of the signal from one terminal to the other terminal, as shown in FIG. A traffic signal output from the first trunk line terminal station 1 to the second trunk line terminal station 2 is a first traffic signal A1 (hereinafter referred to as A1). The traffic signal output to the branch line terminal station 3 is a second traffic signal A2 (hereinafter referred to as A2), which is output from the second trunk line terminal station 2 to the first trunk line terminal station 1. The traffic signal is the third traffic signal B1 (hereinafter referred to as B1), and the traffic signal output from the second trunk line terminal station 2 to the branch line terminal station 3 is the fourth traffic signal B2. (hereinafter referred to as B2), the traffic signal output from the branch line terminal 3 to the first trunk line terminal 1 is the fifth traffic signal C1 (hereinafter referred to as C1), and the branch line terminal The traffic signal output from the second trunk terminal station 2 is a sixth traffic signal C2 (hereinafter referred to as C2).
(Example 1)

In this embodiment, in a submarine optical fiber communication system as shown in FIG. 6, a branch line terminal station 3 performs signal transmission with a first trunk line terminal station 1 and a second trunk line terminal station 2, respectively.

Before each terminal outputs the traffic signal, it must first load the traffic signal into the corresponding frequency band. (first sub-band, second sub-band, third sub-band). Illustratively, a first subband is used to carry signals (A2 and C1) transmitted between a first trunk line terminal 1 and a branch line terminal 3; A sub-band is used to carry the signals (A1 and B1) transmitted between the first trunk terminal 1 and the second trunk terminal 2, and the third sub-band is used for the second trunk terminal. It is used to carry the signals (B2 and C2) transmitted between the trunk line terminal 2 and the branch line terminal 3 of 2. That is, each subband carries traffic signals between two stations that are mutually targeted stations. Based on the carrying relationship between the subbands and the traffic signals, the first multiplexed signal output from the first trunk line terminal station 1 is composed of A2 carried in the first subband and A2 carried in the second subband. a second trunk end station comprising A1 carried in a band and a first loading signal L1 (hereinafter referred to as L1) carried in a third sub-band and for balancing optical power; A second combined signal output from 2 is a second loading signal L2 (hereinafter referred to as L2) carried in the first subband and for balancing the optical power, and a second subband and B2 carried in the third subband, and the third multiplexed signal output from the branch line terminal station 3 includes C1 carried in the first subband and B2 carried in the third subband. , a third loading signal L3 (hereinafter referred to as L3) carried in the second subband and for balancing the optical power, and C2 carried in the third subband. As shown in FIG. 6, the first multiplexed signal, the second multiplexed signal and the third multiplexed signal are processed by the optical add/drop multiplexing/branching unit 4 and sent to the first trunk line terminal station 1. , a fifth combined signal transmitted to the second trunk line terminal station 2, and a sixth combined signal transmitted to the branch line terminal station 3 are obtained. Each of the fourth combined signal, the fifth combined signal, and the sixth combined signal consists of a target traffic signal and at least two non-target traffic signals, and the target traffic signal is the target terminal station and the The non-targeted traffic signal means a traffic signal that is consistent with the receiving terminal, and the non-targeted traffic signal is a traffic signal that is not consistent with the target terminal and the receiving terminal. Here, the filter in the optical add/drop multiplexing/branching unit 4 cuts off only the sub-band carrying the loading signal in the first multiplexed signal, the second multiplexed signal and the third multiplexed signal. i.e., only loading signals can be filtered and each traffic signal can be completely withheld, thereby withholding the complete targeted traffic signal and laying the groundwork for crosstalk processing between subsequent non-targeted traffic signals. Specifically, the conditions that the targeted traffic signal and the at least two non-targeted traffic signals must satisfy are as follows. That is, the targeted traffic signal and the at least two non-targeted traffic signals are carried on different subbands, and the at least two non-targeted traffic signals are all carried on the same subband. In this way, crosstalk of the same frequency occurs between at least two non-target traffic signals located in the same subband, forming a scrambled signal in which traffic information is difficult to recover.

This not only ensures that the number of fiber pairs in the branch line terminal station 3 matches the number of fiber pairs in the trunk line terminal station, but also completes the transmission of traffic signals without increasing the number of fiber pairs. can be done. Also, in the multiplexed signal received by each end station, the non-targeted traffic signals crosstalk with each other to form a scrambled signal, which allows each end station to identify the traffic information carried in the non-targeted traffic signal. can be obtained, only the traffic information carried in the target traffic signal can be obtained, thereby ensuring the transmission security of the traffic signal, and the non-target terminal (transmitted traffic signal It is possible to prevent the monitoring of each station for stations that are not the target station of the target station.

As an example, the subbands are divided according to traffic semaphores transmitted between terminal stations (there are many traffic semaphores between trunk line terminal stations and few traffic semaphores between trunk line terminal stations and branch line terminal stations). Alternatively, a wide subband is allocated to traffic signals transmitted between backbone end stations, and a narrow subband is allocated to traffic signals transmitted between backbone end stations and branch line end stations. The total bandwidth corresponds to frequency bands 0-15, where a first sub-band corresponds to frequency bands 0-3, a second sub-band corresponds to frequency bands 3-12, and a third sub-band corresponds to frequency bands 0-3. Assume that the bands correspond to frequency bands 12-15 and that the wavelength ranges of the three subbands are different.

As shown in FIG. 6, the optical add/drop multiplexing/branching unit 4 includes a first splitter 411, a first filter 412, a second filter 413, and a first multiplexer. 414, a second demultiplexer 421, a third filter 422, a fourth filter 423, a second multiplexer 424, a third demultiplexer 431, and a fifth filter 432 , a sixth filter 433 and a third combiner 434 .

The first demultiplexer 411, the second demultiplexer 421 and the third demultiplexer 431 divide the first multiplexed signal, the second multiplexed signal and the third combined signal, respectively, according to a constant optical power ratio. wave signals and the spectral ratio is independent of wavelength. Each demultiplexer divides one input multiplexed signal into a plurality of branched signals, outputs the branched signals, and transmits each branched signal to a different routing path of the optical add/drop multiplexing branch unit 4. It has at least one input port and at least two output ports.

The first filter 412, the second filter 413, the third filter 422, the fourth filter 423, the fifth filter 432, and the sixth filter 433 may be fixed filters or reconfigurable. It may be a filter, for example a Reconfigurable Wavelength Blocker (WB), each filter blocking a specified sub-band and light of traffic signals carried on a specified sub-band. power can be attenuated. Each filter setting ensures that the sum of the optical power spectral densities of at least two non-targeted traffic signals in the combined signal formed by the combiner is equal to the sum of the optical power spectral densities of each target The condition must be met so that it is equal to the optical power spectral density of the traffic signal.

In some embodiments, when at least two non-targeted traffic signals crosstalk, the quality of the crosstalk is affected by the optical power of each non-targeted traffic signal, i.e., the optical power of each non-targeted traffic signal The closer the , the higher the quality of the crosstalk and the higher the transmission safety of the non-targeted traffic signals, so that the attenuation of the non-targeted traffic signals in the same combined signal by the filter in order to improve the quality of the crosstalk. The subsequent optical powers can be made equal, for example, the same combined signal includes two non-targeted traffic signals, and the filter attenuates the optical power of each non-targeted traffic signal to half of its original power. (ie, 3 dB) such that the post-attenuation optical powers of the two non-targeted traffic signals are equal and the quality of crosstalk on the same subband is highest.

The first multiplexer 414, the second multiplexer 424, and the third multiplexer 434 can integrate the branched signals after filtering, and the multiplexer has wavelength independence. have. In general, a combiner has at least two input ports and at least one output port, and in this embodiment each combiner includes two input ports and one output port, and two input ports. receive two branched signals via and transmit one integrated multiplexed signal to a corresponding terminal station via an output port.

FIG. 6 (In FIG. 6, a rectangle inside a variant consisting of a dashed curve and a solid straight line indicates the total bandwidth, each small rectangle in the rectangle indicates a sub-band, and the width of each small rectangle indicates the bandwidth of the sub-band. , and the height of each small rectangle indicates the optical power spectral density of the traffic signal carried by the subband). The process of branching and transmission will be described, specifically as follows.

[Regarding the first trunk line terminal station 1]
The output interface 11 of the first trunk line terminal station 1 and the first branching filter 411 form a signal transmission line via an optical fiber, and the first branching filter 411 is connected to the first trunk line terminal station. 1 (A2 carried in the first subband + A1 carried in the second subband + L1 carried in the third subband) output from 1. The first demultiplexer 411 has a spectral ratio (in this embodiment, all the demultiplexers have a spectral ratio of 1:1, and in other embodiments, other spectral ratio may be employed) to divide the first combined signal into two signals of equal power (a first branched signal and a second branched signal), the first branched signal and the second branched signal contains the same signal as the first combined signal, but with a different optical power. Here, the first branch signal is transmitted to the second trunk line terminal station 2 and the second branch signal is transmitted to the branch line terminal station 3 .

The first branch signal passes through a first filter 412 that completely blocks the third subband and optically separates the traffic signal carried on the first subband. set to attenuate the power to half the original (in this example, the filters both attenuate the optical power to half the original, i.e. after the attenuation of non-targeted traffic signals for which each optical power needs to be attenuated). are equal, in other embodiments other attenuation methods may be employed as desired), i.e., filtering L1 and passing A1 and A2, where: The optical power in A2 is attenuated by half (the first branch signal after filtering is A2 with the optical power carried in the first subband attenuated by half and the optical power carried in the second subband is attenuated by half). (including A1 and A1). The first branch signal processed by the first filter 412 is subsequently transmitted to the second trunk line terminal station 2 .

The second branch signal passes through a second filter 413, which completely blocks the third subband and lightens the traffic signal carried in the second subband. It is set to attenuate the power to half the original, i.e. filter L1 and pass through A1 and A2, where the optical power of A1 is attenuated by half (the second branch signal after filtering is , A2 carried in the first subband and A1 with the optical power carried in the second subband attenuated by half). The second branch signal processed by the second filter 413 is subsequently transmitted to the branch line terminal station 3 .

[Regarding the second trunk line terminal station 2]
The output interface 21 of the second trunk line terminal station 2 and the second branching filter 421 form a signal transmission path via an optical fiber, and the second branching filter 421 is connected to the second trunk line terminal station. 2 (L2 carried in the first subband + B1 carried in the second subband + B2 carried in the third subband) output from 2. The second demultiplexer 421 divides the second combined signal into two signals (third branched signal and fourth branched signal) having the same power according to the spectral ratio, and divides the third branched signal and the fourth , contains the same signal as the second multiplexed signal, but with a different optical power. Here, the third branch signal is transmitted to the first trunk line terminal station 1 and the fourth branch signal is transmitted to the branch line terminal station 3 .

The third branch signal is passed through a third filter 422 which completely blocks the first subband and lightens the traffic signal carried on the third subband. It is set to attenuate the power to half the original, i.e. filter L2 and pass through B1 and B2, where the optical power of B1 is attenuated by half (the third branch signal after filtering is , B1 carried in the second subband and B2 with half the optical power carried in the third subband). The third branch signal processed by the third filter 422 is subsequently transmitted to the first trunk line terminal station 1 .

The fourth branch signal is passed through a fourth filter 423 which completely blocks the first subband and lightens the traffic signal carried in the second subband. It is set to attenuate the power to half the original, i.e. filter L2 and pass through B1 and B2, where the optical power of B1 is attenuated by half (the fourth branch signal after filtering is , B1 with the optical power carried in the second subband attenuated by half, and B2 carried in the third subband). The fourth branch signal processed by the fourth filter 423 is subsequently transmitted to the branch line terminal station 3 .

[Regarding the branch line terminal station 3]
The output interface 31 of the branch line terminal station 3 and the third demultiplexer 431 form a signal transmission line via an optical fiber. 3 combined signals (C1 carried in the first subband + L3 carried in the second subband + C2 carried in the third subband) are received. The third demultiplexer 431 divides the third combined signal into two signals having the same power (a fifth branched signal and a sixth branched signal) according to the spectral ratio. , contains the same signal as the third multiplexed signal, but with a different optical power. Here, the fifth branched signal is transmitted to the first trunk line terminal station 1 and the sixth branched signal is transmitted to the second trunk line terminal station 2 .

The fifth branch signal passes through a fifth filter 432, which is set to completely block the second subband and attenuate the optical power of C2 to half its original. ie filtering L3 and passing through C1 and C2, where the optical power of C2 is attenuated by half (the fifth branch signal after filtering is carried in the first subband C1 and C2 with the optical power carried in the third subband attenuated by half). The fifth branch signal processed by the fifth filter 432 is subsequently transmitted to the first trunk line terminal station 1 .

The sixth branch signal passes through a sixth filter 433, which is set to completely block the second subband and attenuate the optical power of C1 to half its original. ie filtering L3 and passing through C1 and C2, where the optical power of C1 is attenuated by half (the 6th branch signal after filtering is carried in the 1st subband C1 with optical power attenuated by half and C2 carried in the third subband). The sixth branch signal processed by the sixth filter 433 is subsequently transmitted to the second trunk line terminal station 2 .

Embodiments of the first filter 412 and the second filter 413 will be exemplified below. In embodiments herein, the first filter 412 and the second filter 413 may be band-stop filters or a combination of band-stop and band-pass filters. For example, the first filter 412 may be implemented with two band-stop filters of different model numbers, one of which completely blocks (suppresses) the third sub-band and the other sub-band. It is used to pass all the bands (first sub-band and second sub-band). The other band-stop filter is used to attenuate the optical power of the traffic signal carried in the first sub-band to half its original power and to pass all the second sub-band. Further for example, the second filter 413 may be embodied with one band-stop filter and one band-pass filter, where the band-pass filter filters out only the first sub-band and the second sub-band. It is set to pass and block subbands with other wavelengths (third subband). A band-stop filter other than the band-pass filter is used to attenuate the optical power of the traffic signal carried in the first sub-band to half its original power and pass all the second sub-band.

In addition, the implementation forms of the first filter 412 and the second filter 413 can be referred to each other, and the implementation form of each filter can be selected based on the above contents, and the description thereof will be omitted here. The model number of each filter can be the same or different, and can be designed according to actual needs.

Based on the above process, the process of multiplexing the multiplexed signal received by each terminal station in the optical add/drop multiplexing/branching unit 4 will be described. Specifically, the process is as follows.

[Regarding the first trunk line terminal station 1]
The first combiner 414 outputs the filtered third branch signal (B1 carried in the second subband and B2 with the optical power carried in the third subband attenuated by half). and the filtered fifth branch signal (C1 carried in the first subband and C2 with half the optical power carried in the third subband), and receiving the filtered fifth branch signal The 3 branched signals and the filtered 5th branched signal are integrated into a 4th combined signal. A fourth combined signal includes C1 carried in the first subband, B1 carried in the second subband, and B2 and C2 carried in the third subband. include. When combining B2 and C2, the two traffic signals are both carried by the third sub-band, so that the frequency bands completely overlap, thus forming co-frequency crosstalk when combining. Thereby, the data code stream carried in the third sub-band is completely perturbed to form a scrambled signal, which cannot be recovered.

The first multiplexer 414 and the input interface 12 of the first trunk line terminal station 1 form a signal transmission path through an optical fiber, and the fourth multiplexed signal is transmitted through the signal transmission path. As a result, the first trunk line terminal 1 receives B1 transmitted from the second trunk line terminal 2 and C1 transmitted from the branch line terminal 3. B2 scheduled to be transmitted to the branch line terminal 3 of the second trunk line terminal 2 and C2 scheduled to be transmitted to the second trunk line terminal 2 of the branch line terminal 3 Since crosstalk of the same frequency occurs at the time of multiplexing, a scrambled traffic signal is formed. Thereby, the safety of the communication traffic between the second trunk line terminal station 2 and the branch line terminal station 3 can be guaranteed.

[Regarding the second trunk line terminal station 2]
The second combiner 424 outputs the filtered first branch signal (A2 with the optical power carried in the first subband attenuated by half and A1 carried in the second subband). and the filtered sixth branch signal (C1 with the optical power carried in the first subband attenuated by half and C2 carried in the third subband), and The 1 branched signal and the filtered 6th branched signal are integrated into a 5th combined signal. A fifth combined signal includes A2 and C1 carried in the first subband, A1 carried in the second subband, and C2 carried in the third subband. include. When combining A2 and C1, the two traffic signals are both carried by the first subband, so that the frequency bands completely overlap, thus forming co-frequency crosstalk when combining. Thereby the data code stream carried in the first sub-band is completely disturbed and such a scrambled signal cannot be recovered.

The second multiplexer 424 and the input interface 22 of the second trunk line terminal station 2 form a signal transmission path via an optical fiber, and the fifth multiplexed signal is transmitted via the signal transmission path to the 2, whereby the second trunk line terminal 2 receives A1 transmitted from the first trunk line terminal 1 and C2 transmitted from the branch line terminal 3. A2 to be transmitted to the branch line terminal 3 of the first trunk line terminal 1 and C1 to be transmitted to the first trunk line terminal 1 of the branch line terminal 3 Since crosstalk of the same frequency occurs at the time of multiplexing, a scrambled traffic signal is formed. Thus, the safety of communication traffic between the first trunk line terminal station 1 and the branch line terminal station 3 can be guaranteed.

[Regarding the branch line terminal station 3]
A third combiner 434 outputs the filtered second branch signal (A2 carried in the first subband and A1 with the optical power carried in the second subband attenuated by half). and a filtered fourth branch signal (B1 in which the optical power carried in the second subband is attenuated by half and B2 carried in the third subband); 2 branched signals and the filtered fourth branched signal are integrated into a sixth combined signal. A sixth combined signal includes A2 carried in the first subband, A1 and B1 carried in the second subband, and B2 carried in the third subband. include. When combining A2 and B1, the two traffic signals are both carried by the first subband, so that the frequency bands completely overlap, thus forming co-frequency crosstalk when combining. Thereby the data code stream carried in the second sub-band is completely disturbed and such a scrambled signal cannot be recovered.

The third multiplexer 434 and the input interface 32 of the branch line terminal station 3 form a signal transmission line through an optical fiber, and the sixth combined signal is transmitted through the signal transmission line to the branch line terminal station. 3, whereby the branch line terminal 3 can receive A2 transmitted from the first trunk line terminal 1 and B2 transmitted from the second trunk line terminal 2, and , A1 scheduled to be transmitted to the second trunk line terminal 2 of the first trunk line terminal 1 and B1 scheduled to be transmitted to the first trunk line terminal 1 of the second trunk line terminal 2 Since crosstalk of the same frequency occurs when multiplexing the two, a scrambled traffic signal is formed. The safety of communication traffic between the first trunk line terminal station 1 and the second trunk line terminal station 2 can be guaranteed.

According to the above technical configuration, the terminal acquires the traffic information in the non-target traffic signal by crosstalking the non-target traffic signal in the combined signal received by each terminal on the same subband. can be avoided, thereby ensuring the transmission safety of traffic signals between terminals.
(Example 2)

In Example 1, it is divided into subbands only according to preset conditions (eg, historical traffic semaphores), and such roughly divided subbands may be referred to as initial subbands. However, since the traffic semaphore between terminal stations changes dynamically during actual use, it is difficult to adapt to dynamic changes in the traffic semaphore if the initial subband is always used for signal transmission. Become. The initial subbands, in use, are generally divided into two parts: occupied bandwidth (actually used to transmit signals) and idle subbands (not yet used to transmit signals). In order to adapt to dynamic changes in the traffic semaphores of each end station, i.e., if the semaphore carried on one initial subband exceeds the corresponding bandwidth, the other initial subbands idle Subbands may be used to transmit excess signals corresponding to exceeding the bandwidth. The idle subbands can then be subdivided by respective filters, whereby filters in this example specifically mean reconstructable filters such as WB. Define an idle subband as a fourth subband for carrying extra signals corresponding to the first subband, the second subband or the third subband, where the fourth subband may be adjacent to the initial subband corresponding to the extra signal or may be spaced from each other from the initial subband corresponding to the extra signal.

Illustratively, the total bandwidth corresponds to frequency bands 0-15, such as the initial sub-bands shown in FIG. 7, where the first sub-band corresponds to frequency bands 0-3, the second Assuming that the sub-bands correspond to frequency bands 3-12 and the third sub-band corresponds to frequency bands 12-15, in actual use, the first trunk line terminal station 1 and the branch line terminal station 3 signals transmitted between completely occupy the first sub-band, and signals transmitted between the first trunk terminal 1 and the second trunk terminal 2 occupy the second sub-band. Although the band is completely occupied, the signals transmitted between the second backbone terminal 2 and the branch line terminal 3 occupy only part of the bandwidth of the third sub-band, e.g. As shown in FIG. 7, only 12-13 bandwidths are occupied, so 13-15 in the third subband become idle subbands. When the number of semaphores transmitted between the first trunk line terminal station 1 and the branch line terminal station 3 increases, the idle subband can be used to transmit the increased signal. As shown, the idle subband is reconfigured as a fourth subband, the fourth subband and the first subband are spaced apart from each other, and the fourth subband is the first backbone. It is used to carry signals transmitted between the line terminal 1 and the branch line terminal 3 . Alternatively, when the number of semaphores transmitted between the first trunk line terminal station 1 and the second trunk line terminal station 2 increases, the idle subband can be used to transmit the increased signal. 8, the subband division method is to reset the idle subband as the fourth subband, the fourth subband and the second subband are spaced apart from each other, and the The fourth subband is used to carry signals transmitted between the first trunk terminal 1 and the second trunk terminal 2 .

In some embodiments, the third subband occupies only bandwidths 13-15, such that 12-13 in the third subband are idle subbands. In this case, when the number of semaphores transmitted between the first trunk line terminal station 1 and the branch line terminal station 3 increases, the increased signal can be transmitted using the idle subband. The idle subband is reconfigured as a fourth subband, the fourth subband and the first subband are spaced apart from each other, and the fourth subband is the first subband, as shown in FIG. It is used to carry signals transmitted between the trunk line terminal station 1 and the branch line terminal station 3. Alternatively, when the number of semaphores transmitted between the first trunk line terminal station 1 and the second trunk line terminal station 2 increases, the idle subband can be used to transmit the increased signal. In this case, referring to FIG. 9, the subband division method is to reset the idle subband as the fourth subband, the fourth subband and the second subband are adjacent, and the fourth subband is The subbands are used to carry signals transmitted between the first trunk terminal 1 and the second trunk terminal 2 .

For the case where the fourth sub-band is adjacent to the sub-band corresponding to the redundant signal, the process of transmitting signals between terminals after re-dividing the sub-bands can refer directly to Embodiment 1. , not repeated here.

For the case where the fourth subband is positioned interphase with the subband corresponding to the redundant signal, the fourth subband is between the first trunk terminal 1 and the second trunk terminal 2. The fourth sub-band and the second sub-band are used to carry a signal to be transmitted, and the fourth sub-band and the second sub-band are spaced apart from each other. The traffic signals A1 and B1 carried on the fourth subband are denoted by A1-1 and B1-1, the extra traffic signals carried on the fourth subband are denoted by A1-2 and B1-2, and the traffic signals carried on the remaining subbands are denoted by A1-2 and B1-2. Please refer to Example 1 for the traffic signal. In this case, FIG. 10 can be referred to for the signal transmission process between terminals, and Embodiment 1 can be referred to for the demultiplexing, filtering and multiplexing processes of traffic signals in each subband. , not repeated here.
(Example 3)

According to the optical add/drop multiplexing/branching unit 4 according to the first embodiment, the optical add/drop multiplexing/branching unit 4 has the branch line terminal station 3 which is connected to the first trunk line terminal station 1 and the second trunk line terminal station 1. It is possible to implement signal transmission with only one trunk terminal of the terminals 2 . In this case, each filter can reconstruct the initial sub-bands (first sub-band, second sub-band and third sub-band) in Example 1, thereby reducing the need to carry the signal. Integrate subbands that are not connected (there is no signal transmission relationship between terminals) with adjacent subbands to obtain two reconstructed subbands, and use the reconstructed subbands to generate corresponding signals. It carries and carries out signal transmission. By this, filter in this embodiment specifically means a reconfigurable filter such as WB.

As an example, signal transmission between the first trunk line terminal station 1 and the branch line terminal station 3 is interrupted, and signal transmission between the second trunk line terminal station 2 and the branch line terminal station 3 is interrupted. , where the subband reconstruction can combine the first and second subbands, retain the third subband, and the combined first The subband and the second subband can be a fifth subband. In some embodiments, the original bandwidth of the third subband may be maintained, or the bandwidths of the fifth and third subbands may be readjusted according to actual needs. good too. In this case, the third sub-band is still used to carry signals between the second trunk terminal 2 and the branch terminal 3, but the fifth sub-band is used for the first trunk terminal. It is used to carry signals between the line terminal 1 and the second trunk line terminal 2, in this case the signal between the first trunk line terminal 1 and the branch line terminal 3. There are no subbands to do. In some embodiments, a third subband may be used to carry signals between the first trunk terminal 1 and the second trunk terminal 2, and a fifth subband. may be used to carry signals between the second trunk line terminal 2 and the branch line terminal 3 . A third subband is used to carry signals between the second trunk terminal 2 and the branch line terminal 3, and a fifth subband is used to carry signals between the first trunk terminal 1 and the second trunk terminal 1. 11 for the signal transmission process between each terminal station, where in each sub-band The demultiplexing, filtering and multiplexing processes of the traffic signal can all refer to Embodiment 1 and will not be repeated here.

When the branch line terminal station 3 needs to transmit signals again between the first trunk line terminal station 1 and the second trunk line terminal station 2, respectively, based on the reconstructed subbands in this embodiment , may reconstruct the current subband again, divide any one of the current subbands, and part of the subbands after division carry the traffic signal currently carried by the subband to be divided. and the remaining subbands are used to carry newly added traffic signals (traffic signals corresponding to trunk line terminals that have again established signaling relationships with branch line terminals). , the demultiplexing, filtering and combining processes of the traffic signal in the reconstructed subbands can all refer to Embodiment 1 and will not be repeated here.

According to the above technical configuration, traffic signals communicated between two trunk line terminal stations and between two trunk line terminal stations and branch line terminal stations are loaded into different subbands and transmitted. , the problem of wavelength collision is avoided, and the corresponding sub-band signals can be transmitted together in one optical fiber, so that the backbone section and the branch section can use the same number of fiber pairs; It can support communication between two trunk end stations and branch line end stations, reducing the complexity and cost of the submarine cable system.

Also, in the process of combining each traffic signal, the non-targeted traffic signals of each terminal are carried in the same subband, and each non-targeted traffic signal is from a different terminal. Crosstalk can be formed between the non-targeted traffic signals to form irreversible scrambled signals, ensuring that the traffic information carried in the non-targeted traffic signals is not acquired by the end stations; It can guarantee the transmission safety of traffic information between stations. Since this scrambling method does not require additional devices such as a demultiplexer/multiplexer and a combiner, system transmission performance is not degraded due to changes in insertion loss in intermediate stages of OADM/ROADM.

In addition, the subband reconstruction method can adjust the connectivity (blocking or connecting) between each terminal station without redesigning the network physical layer. to flexibly distribute the communication bandwidth between each terminal station according to changes in traffic conditions, by simply changing the subband setting of the WB by issuing It can support communication with terminal stations, thereby effectively avoiding the situation of insufficient bandwidth and wavelength idle at the same time, improving the bandwidth utilization rate of the system, and the initial construction of the network. The demands on the traffic prediction accuracy of stages can be lowered.
(Example 4)

In this embodiment, in a submarine optical fiber communication system as shown in FIG. 12, a branch line terminal station 3 performs signal transmission with a first trunk line terminal station 1 and a second trunk line terminal station 2, respectively. Before each terminal can output a traffic signal, it must first load the traffic signal into the corresponding frequency band. The specific loading process (subband division, subband reconstruction) can directly refer to Example 1, Example 2 or Example 3, and will not be repeated here.

As shown in FIG. 12, the optical add/drop multiplexing/branching unit 4 in this embodiment includes a first wavelength selectable switch (WSS) 415, a first multiplexer 414, and a second A wavelength selective switch 425 , a second multiplexer 424 , a third wavelength selective switch 435 and a third multiplexer 434 are included. Each wavelength selective switch WSS can be a 1×N (N≧2) wavelength selective switch and has a plurality of output ports, where N means the number of output ports.

First, the first wavelength selective switch 415, the second wavelength selective switch 425, and the third wavelength selective switch 435 generate the first combined signal, the second combined signal, and the third combined signal according to a fixed ratio. The signals can be distributed individually and the spectral ratio is independent of wavelength. Each wavelength selective switch WSS divides one input multiplexed signal into a plurality of branched signals, outputs the branched signals, and transmits each branched signal to a different routing path in the optical add/drop multiplexing branch unit 4. , has at least one input port and at least two output ports.

In turn, the first wavelength selective switch 415, the second wavelength selective switch 425 and the third wavelength selective switch 435 can also be dynamically reconfigured and used as reconfigurable wavelength blockers. be able to. Each wavelength selective switch WSS is capable of blocking a designated subband and attenuating the optical power of traffic signals carried on the designated subband. The setting of each wavelength selective switch WSS is such that the sum of the optical power spectral densities of at least two non-targeted traffic signals in the combined signal formed by the combiner is , to be equal to the optical power spectral density of each target traffic signal.

The process of integrating the filtered branch signals by the first combiner 414, the second combiner 424 and the third combiner 434 can directly refer to Embodiment 1 and will not be repeated here. .

As can be seen from the above content, each wavelength selective switch WSS can realize demultiplexing and filtering, and can be used in place of demultiplexers and filters in the output path of demultiplexers. Specifically, it is as follows.

[Regarding the first trunk line terminal station 1]
The output interface 11 of the first trunk line terminal station 1 and the first wavelength selective switch 415 form a signal transmission line via an optical fiber, and the first wavelength selective switch 415 is connected to the first trunk line terminal station. 1 (A2 carried in the first subband + A1 carried in the second subband + L1 carried in the third subband) output from 1. The first wavelength selective switch 415 has a spectral ratio (in this embodiment, the splitter has a spectral ratio of 1:1 as an example, and other embodiments adopt other spectral ratios as necessary). may be used), the first multiplexed signal is divided into two signals having equal power (a first branched signal and a second branched signal), and the first branched signal and the second branched signal are divided into a second 1 contains the same signal as the multiplexed signal, but the optical power is different. Here, the first branch signal is transmitted to the second trunk line terminal station 2 and the second branch signal is transmitted to the branch line terminal station 3 .

The first wavelength selective switch 415 is further used to filter the first branch signal, the first wavelength selective switch 415 completely blocking the third subband upon reconstruction, and , are set to attenuate the optical power of traffic signals carried on the first subband to half the original (in this example, the filters both attenuate the optical power to half the original, i.e., each For example, the post-attenuation optical power of non-targeted traffic signals that need to be attenuated is equal; other embodiments may adopt other attenuation methods as needed), i.e., L1 and pass through A1 and A2, where the optical power of A2 is attenuated by half (the first branch signal after filtering has half the optical power carried in the first subband and A1 carried in the second subband). The first branch signal processed by the first wavelength selective switch 415 is continuously transmitted to the second trunk line terminal station 2 via the first output port 4151 .

The first wavelength selective switch 415 is further used to filter the second branch signal, the first wavelength selective switch 415 completely blocking the third subband upon reconstruction, and , is set to attenuate the optical power of the traffic signal carried in the second subband to half of the original, i.e. filter L1 and pass through A1 and A2, where the optical power of A1 is attenuated by half (the second branch signal after filtering is A2 carried in the first subband and A1 with the optical power carried in the second subband attenuated by half; including). The second branch signal processed by the first wavelength selective switch 415 is continuously transmitted to the branch line terminal station 3 via the second output port 4152 .

That is, the first wavelength selective switch 415 can be used instead of the first demultiplexer 411 , the first filter 412 and the second filter 413 .

[Regarding the second trunk line terminal station 2]
The output interface 21 of the second trunk line terminal station 2 and the second wavelength selective switch 425 form a signal transmission line via an optical fiber, and the second wavelength selective switch 425 is connected to the second trunk line terminal station. 2 (L2 carried in the first subband + B1 carried in the second subband + B2 carried in the third subband) output from 2. The second wavelength selective switch 425 splits the second combined signal into two signals having the same power (third branched signal and fourth branched signal) according to the spectral ratio. The branched signal contains the same signal as the second combined signal, but with a different optical power. Here, the third branch signal is transmitted to the first trunk line terminal station 1 and the fourth branch signal is transmitted to the branch line terminal station 3 .

A second wavelength selective switch 425 is further used to filter the third branch signal, the second wavelength selective switch 425 completely blocking the first subband upon reconstruction, and , is set to attenuate the optical power of traffic signals carried in the third subband to half of the original, i.e., filter L2 and pass B1 and B2, where the optical power of B2 is is attenuated by half (the third branch signal after filtering is B1 carried in the second subband and B2 with the optical power carried in the third subband attenuated by half ,including). The third branched signal processed by the second wavelength selective switch 425 is continuously transmitted to the first trunk line terminal station 1 via the third output port 4251 .

A second wavelength selective switch 425 is further used to filter the fourth branch signal, the second wavelength selective switch 425 completely blocking the first subband upon reconstruction, and , is set to attenuate the optical power of traffic signals carried in the second subband to half of the original, i.e., filter L2 and pass B1 and B2, where the optical power of B1 is is attenuated by half (the fourth branch signal after filtering is B1 with the optical power carried in the second subband attenuated by half, and B2 carried in the second subband. ,including). The fourth branch signal processed by the second wavelength selective switch 425 is subsequently transmitted to the branch line terminal station 3 via the fourth output port 4252 .

That is, the second wavelength selective switch 425 can be used instead of the second demultiplexer 421 , the third filter 422 and the fourth filter 423 .

[Regarding the branch line terminal station 3]
The output interface 31 of the branch line terminal station 3 and the third wavelength selective switch 435 form a signal transmission line via an optical fiber. 3 combined signals (C1 carried in the first subband + L3 carried in the second subband + C2 carried in the third subband) are received. The third wavelength selective switch 435 splits the third combined signal into two signals having the same power (a fifth branched signal and a sixth branched signal) according to the spectral ratio, and splits the fifth branched signal and the sixth branched signal. , contains the same signal as the third multiplexed signal, but with a different optical power. Here, the fifth branched signal is transmitted to the first trunk line terminal station 1 and the sixth branched signal is transmitted to the second trunk line terminal station 2 .

A third wavelength selective switch 435 is further used to filter the fifth branch signal, the third wavelength selective switch 435 completely blocking the second subband upon reconstruction, and , is set to attenuate the optical power of C2 to half the original, i.e., filter L3 and pass through C1 and C2, where the optical power of C2 is attenuated by half (the second after filtering). The five branch signals include C1 carried in the first subband and C2 with half the optical power carried in the third subband). The fifth branch signal processed by the third wavelength selective switch 435 is continuously transmitted to the first backbone terminal station 1 via the fifth output port 4351 .

A third wavelength selective switch 435 is further used to filter the sixth branch signal, the third wavelength selective switch 435 completely blocking the second subband upon reconstruction, and It is set to attenuate the optical power of C1 to half the original, i.e. filter L3 and pass through C1 and C2, where the optical power of C1 is attenuated by half (6th The branched signal of (1) comprises C1 with half the optical power carried in the first subband and C2 carried in the third subband). The sixth branched signal processed by the third wavelength selective switch 435 is continuously transmitted to the second trunk line terminal station 2 via the sixth output port 4352 .

That is, the third wavelength selective switch 435 can be used instead of the third demultiplexer 431 , the fifth filter 432 and the sixth filter 433 .

The process of multiplexing the multiplexed signal received by each terminal station in the optical add/drop multiplexing/branching unit 4 can directly refer to the first embodiment, and will not be repeated here.

It should be noted that the wavelength selective switch WSS is suitable for performing the subband division process in the second and third embodiments because it can realize dynamic reconfiguration.

According to the above technical configuration, this embodiment adopts the wavelength selective switch WSS instead of the demultiplexer and the filter, and the wavelength selective switch WSS has a higher degree of integration and is easy to install and remote control. .

The above specific embodiments describe the purpose, technical configuration and beneficial effects of the present invention in more detail. It should be understood that the above are only specific embodiments of the present invention, and the present invention Any modification, equivalent substitution, improvement, etc. made on the basis of the technical structure of the present invention should be included in the protection scope of the present invention. is.

Claims (13)

a plurality of terminal stations including two trunk line terminal stations and at least one branch line terminal station;
a traffic signal is transmitted between the two trunk line terminals and between the at least one branch line terminal and the two trunk line terminals;
a multiplexed signal output from each terminal station of the plurality of terminal stations is processed by a corresponding optical add/drop multiplexing/branching unit to obtain a processed multiplexed signal to be transmitted to the other terminal station;
the multiplexed signal output from each terminal includes a plurality of traffic signals carried in different subbands;
The optical add/drop multiplexing/branching unit includes a plurality of demultiplexers, a plurality of filters, and a plurality of multiplexers, and the plurality of demultiplexers, the plurality of filters, and the plurality of multiplexers each of the processed combined signals obtained by processing by the device includes a target traffic signal and at least two non-target traffic signals, wherein the target traffic signal and the at least two non-target traffic signals are different carried on subbands, the at least two non-targeted traffic signals carried on the same subband, the directions of transmission of the at least two non-targeted traffic signals being opposite;
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.
A communication system characterized by: The combined signal output from each terminal station further includes a loading signal for balancing the optical power of the plurality of traffic signals in the combined signal,
The communication system according to claim 1, characterized by: the sum of the optical power spectral densities of the at least two non-targeted traffic signals equals the optical power spectral density of the targeted traffic signal;
The communication system according to claim 1, characterized by: the optical powers of the at least two non-targeted traffic signals are equal;
The communication system according to claim 1, characterized by: at least one of said subbands includes an idle subband for carrying excess signal corresponding to a first target subband, said excess signal exceeding the bandwidth of said first target subband means traffic signal,
The communication system according to claim 1, characterized by: the idle subband and the first target subband are adjacent or spaced apart from each other;
6. The communication system according to claim 5, characterized by: When said at least one branch line terminal communicates with only one said trunk line terminal, said sub-band is transmitted between said at least one branch line terminal and one said trunk line terminal. divided based on a traffic signal and a traffic signal transmitted between two said trunk end stations;
A traffic signal transmitted between said at least one branch line terminal station and one said trunk line terminal station and a traffic signal transmitted between two said trunk line terminal stations are carried in different said subbands. to be
The communication system according to claim 1, characterized by: wherein the plurality of filters employ reconfigurable wavelength blockers;
8. The communication system according to claim 7, characterized by: The plurality of filters employs band-stop filters with the same or different parameters, or the plurality of filters employs a combination of band-stop filters and band-pass filters, and the parameters of each filter are: the same or different,
The communication system according to claim 1, characterized by: a plurality of terminal stations including two trunk line terminal stations and at least one branch line terminal station;
traffic signals are transmitted between the two trunk line terminals and between the at least one branch line terminal and the two trunk line terminals;
a multiplexed signal output from each terminal station of the plurality of terminal stations is processed by a corresponding optical add/drop multiplexing/branching unit to obtain a processed multiplexed signal to be transmitted to the other terminal station;
the multiplexed signal output from each terminal includes a plurality of traffic signals carried in different subbands;
The optical add/drop multiplexing/branching unit includes a plurality of wavelength selective switches for demultiplexing and filtering the combined signal, and a plurality of multiplexers. each of said processed combined signals obtained by being processed by a plurality of combiners includes a targeted traffic signal and at least two non-targeted traffic signals, said targeted traffic signal and said at least two non-targeted traffic signals; is carried on different subbands, said at least two non-targeted traffic signals being carried on the same subband, and the directions of transmission of said at least two non-targeted traffic signals being opposite;
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.
A communication system characterized by: including multiple demultiplexers, multiple filters, and multiple multiplexers,
the plurality of duplexers are connected to signal output interfaces of corresponding terminal stations;
the plurality of multiplexers are connected to signal input interfaces of corresponding terminal stations;
The processed combined signal obtained by processing the multiplexed signal input to the optical add/drop multiplexing/branching unit by the plurality of demultiplexers, the plurality of filters, and the plurality of multiplexers is a target a traffic signal and at least two non-targeted traffic signals, wherein the targeted traffic signal and the at least two non-targeted traffic signals are carried on different subbands, and the at least two non-targeted traffic signals are carried on the same subband. and the directions of transmission of the at least two non-targeted traffic signals are opposite;
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.
An optical add/drop multiplexing/branching unit characterized by: including a plurality of wavelength selective switches and a plurality of multiplexers,
input terminals of the plurality of wavelength selective switches are connected to signal output interfaces of corresponding terminal stations;
output terminals of the plurality of wavelength selective switches are respectively connected to input terminals of the plurality of multiplexers;
the output terminals of the plurality of multiplexers are connected to signal input interfaces of corresponding terminal stations;
The wavelength selective switch is used to demultiplex and filter the multiplexed signal,
The multiplexed signal obtained by processing the multiplexed signal input to the optical add/drop multiplexing/branching unit by the plurality of wavelength selective switches and the plurality of multiplexers includes a target traffic signal and at least two two non-targeted traffic signals, wherein the target traffic signal and the at least two non-targeted traffic signals are carried on different subbands, the at least two non-targeted traffic signals are carried on the same subband, the at least two The direction of transmission of the two non-targeted traffic signals is opposite,
The target traffic signal means a traffic signal in which a corresponding target terminal station and a terminal station that receives the processed combined signal match, among the processed combined signal,
The non-target traffic signal means a traffic signal in which the corresponding target terminal station and the terminal station receiving the processed combined signal do not match among the processed combined signal.
An optical add/drop multiplexing/branching unit characterized by: A signal transmission method applied to the communication system according to any one of claims 1 to 10,
dividing a total bandwidth by the terminal into a specified number of subbands;
a step of the terminal station carrying a traffic signal and a loading signal to be output in different subbands to obtain a combined signal;
the optical add/drop multiplexing/branching unit processing the multiplexed signal to obtain a processed multiplexed signal;
and a step in which the optical add/drop multiplexing/branching unit transmits the processed multiplexed signal to each of the terminal stations opposite to the terminal station.
A signal transmission method characterized by:

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