Terminals and Optical Networks

Abstract

A terminal according to the present invention comprises: a housing; an input port whereby an optical signal is introduced into the interior of the housing; a wavelength demultiplexer that receives input of the optical signal introduced from the input port and splits the optical signal into a predetermined wavelength band and other wavelength bands; a distribution port that distributes the optical signal in the predetermined wavelength band split by the wavelength demultiplexer to an external terminal; and an output port whereby the optical signal in other wavelength bands than the predetermined wavelength band split by the wavelength demultiplexer is removed to the exterior of the housing. The number of wavelength demultiplexers is equal to the number of a plurality of optical fibers, a plurality of the wavelength demultiplexers are provided, and each wavelength demultiplexer among the plurality of wavelength demultiplexers is connected with a respective optical fiber among the plurality of optical fibers.

Description

[Technical Field]

[0001] The present invention relates to a terminal and an optical network. This application claims priority from Japanese Patent Application No. 2022-095815, filed on June 14, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Various optical network installation methods have been proposed to build wide-area communication networks. For example, Patent Document 1 discloses an optical network including multiple terminals (terminals 110) and multiple distribution cables (distribution cables 150A-150H) that relay the terminals (see FIG. 1 of Patent Document 1). Each terminal has a first port (112) connected to a subscriber terminal (subscriber 109) and a second port (114) connected to the next terminal. Each cable includes 12 connection optical fibers (see FIG. 2 of Patent Document 1). The 12 optical fibers are assigned to 12 positions P1 to P12, one by one, by a connector (connector 156).

[0003] In each terminal, the optical fiber allocated to position P1 (first optical fiber 152) is connected to the first port. As a result, the optical signal transmitted by the optical fiber allocated to position P1 is transmitted to the subscriber terminal. On the other hand, the optical fiber allocated to positions P2 to P12 (remaining optical fiber 154) is connected to the second port. As a result, each optical signal transmitted by the optical fiber allocated to positions P2 to P12 is forwarded to the next terminal. At this time, the optical fibers allocated to positions P2 to P12 are reallocated to positions P1' to P11', respectively, and then connected to the next terminal. As a result, in the next terminal, the optical fiber allocated to position P1' is connected to the first port, and the optical fibers allocated to positions P2' to P11' are connected to the second port. With this configuration, a daisy-chain optical network can be realized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 9,348,096 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the optical network disclosed in Patent Document 1, the actual number of optical fibers in the optical cable connecting the terminals decreases toward the downstream side. In other words, the effective density of optical fibers in the optical cable decreases.

[0006] The present invention has been made in consideration of the above circumstances, and has as its object to provide a terminal and an optical network that are capable of maintaining the effective density of optical fibers. [Means for solving the problem]

[0007] In order to solve the above problems, a terminal according to a first aspect of the present invention is a terminal for inputting and outputting optical signals from a plurality of optical fibers in an optical cable, and includes a housing, an input port for introducing the optical signals into the housing, a plurality of wavelength demultiplexers to which the optical signals introduced from the input port are input and which demultiplex the optical signals into a predetermined wavelength band and other wavelength bands, a distribution port for distributing the optical signals of the predetermined wavelength bands demultiplexed by the wavelength demultiplexers to an external terminal, and an output port for extracting the optical signals of the other wavelength bands demultiplexed by the wavelength demultiplexers to the outside of the housing. The number of the plurality of wavelength demultiplexers is equal to the number of the plurality of optical fibers, and one of the plurality of wavelength demultiplexers is connected to one of the plurality of optical fibers.

[0008] Furthermore, in a terminal of aspect 2 of the present invention, when an optical fiber that transmits an optical signal from the input port to the wavelength demultiplexer is an input fiber in the terminal of aspect 1, and an optical fiber that transmits an optical signal from the wavelength demultiplexer to the output port is an output optical fiber, the input optical fiber and the output optical fiber are connected one-to-one via the wavelength demultiplexer, and the positions of the connected input optical fiber and output optical fiber at the input port and the positions at the output port may be different from each other.

[0009] A terminal according to a third aspect of the present invention may be the terminal according to the first or second aspect, wherein only one wavelength band is set in the wavelength demultiplexer.

[0010] Furthermore, a terminal according to a fourth aspect of the present invention may be the terminal according to the first or second aspect, wherein the wavelength demultiplexer is set with a plurality of wavelength bands.

[0011] Furthermore, a terminal of aspect 5 of the present invention may be a terminal of any one of aspects 1 to 4, which includes a plurality of wavelength demultiplexers, and the wavelength bands set for the plurality of wavelength demultiplexers may be the same as each other.

[0012] Furthermore, a terminal of aspect 6 of the present invention may be a terminal of any one of aspects 1 to 4, which includes a plurality of wavelength demultiplexers, and the wavelength bands set for the plurality of wavelength demultiplexers may be different from each other.

[0013] Moreover, the optical network according to the seventh aspect of the present invention has a plurality of terminals according to any one of the first to sixth aspects.

[0014] Furthermore, an optical network of aspect 8 of the present invention is an optical network having a plurality of terminals of aspect 6, wherein the terminals include a first terminal and a second terminal, the plurality of wavelength demultiplexers of the first terminal and the plurality of wavelength demultiplexers of the second terminal are connected one-to-one, and the wavelength demultiplexers of the connected first terminal and the wavelength demultiplexers of the connected second terminal have different wavelength bands set. [Effects of the Invention]

[0015] According to the above aspects of the present invention, it is possible to provide a terminal and an optical network that are capable of maintaining the effective density of optical fibers. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating an optical network according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a terminal according to the first embodiment. [Figure 3A] 2 is a diagram showing one end of a connecting optical cable according to the first embodiment. FIG. [Figure 3B] FIG. 2 is a diagram illustrating an input port according to the first embodiment. [Figure 4A] FIG. 2 is a diagram illustrating one end of a supply optical cable according to the first embodiment. [Figure 4B] FIG. 2 is a diagram showing a distribution port according to the first embodiment. [Figure 5] FIG. 1 is a wiring diagram showing an optical network according to a first embodiment. [Figure 6] FIG. 10 is a wiring diagram showing an optical network according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (First embodiment) Hereinafter, a terminal 1 according to the first embodiment and an optical network NW1 using the terminal 1 will be described with reference to the drawings.

[0018] As shown in FIG. 1, the optical network NW1 according to this embodiment includes a first terminal 1A, a second terminal 1B, a third terminal 1C, and a fourth terminal 1D. In this embodiment, the terminals 1A to 1D are connected in a daisy chain fashion by a connecting optical cable C2. That is, the terminals 1A and 1B, the terminals 1B and 1C, and the terminals 1C and 1D are each connected by the connecting optical cable C2. Each of the terminals 1A to 1D is fixed to, for example, a utility pole. Hereinafter, when the terminals 1A to 1D are not particularly distinguished from one another, they may be simply referred to as "terminal 1." The terminals 1A to 1D are also referred to as "network terminals."

[0019] The terminal 1A according to this embodiment is connected to the central office 100 via a closure 110 buried underground. More specifically, the terminal 1A and the closure 110 are connected by a connection optical cable C2, and the closure 110 and the central office 100 are connected by a distribution optical cable C1. Each of the terminals 1A to 1D is connected to a plurality of subscriber terminals 120 by optical fibers provided in a supply optical cable C3. Each of the terminals 1A to 1D has the role of distributing optical signals transmitted from the central office 100 to each of the subscriber terminals 120. Hereinafter, the direction from the terminal 1A toward the terminal 1D may be referred to as the "downstream side," and the direction from the terminal 1D toward the terminal 1A may be referred to as the "upstream side."

[0020] Next, the mechanical configuration of each of the terminals 1A to 1D will be described. The mechanical configuration of the terminals 1A to 1D is basically the same.

[0021] As shown in Fig. 2, the terminal 1 according to this embodiment includes a housing 10. The housing 10 has an input port 12, an output port 14, and four distribution ports 13. As shown in Fig. 1, one end of a connection optical cable C2 is connected to the input port 12. One end of a connection optical cable C2 different from the connection optical cable C2 connected to the input port 12 is connected to the output port 14. One end of a supply optical cable C3 is connected to each distribution port 13.

[0022] As shown in FIG. 3A, each connection optical cable C2 has four connection optical fibers 60. The term "connection optical fiber 60" is a general term for optical fibers connecting terminals 1 to each other or connecting a closure 110 to a terminal 1. The connection optical fibers 60 can also be considered optical fibers included in the connection optical cable C2. The connection optical fibers 60 are disposed outside the housing 10. In this embodiment, the end of the connection optical cable C2 is connectorized. In other words, a (multi-fiber) connector 60a is provided at the end of the connection optical cable C2. The connector 60a has a ferrule 60b having a connection end face 60c and a cylindrical plug portion 60d. The connection end face 60c has four fiber holes 60h and a pair of guide holes 60g. Each connection optical fiber 60 is inserted through the fiber hole 60h so that its tip is positioned at the connection end face 60c and is held by the ferrule 60b. The ferrule 60b is positioned radially inside the plug portion 60d. The plug portion 60d has a key groove 60e recessed radially inward from the outer circumferential surface of the plug portion 60d. In this embodiment, for ease of understanding, the number of connecting optical fibers 60 included in one connector 60a is described as four, but the number may be more than four, such as 12 or 24. A ferrule 60b having the same number of fiber holes 60h as the number of connecting optical fibers 60 is used.

[0023] As shown in FIG. 3B, the input port 12 has four input optical fibers 20. The "input optical fiber 20" is a general term for optical fibers that transmit optical signals input to the terminal 1 to a wavelength demultiplexer 50 (described later). The input optical fibers 20 are arranged inside the housing 10. The input port 12 is provided with a receptacle 12a into which a connector 60a is inserted. The receptacle 12a has an insertion hole 12d into which a plug portion 60d is inserted and a ferrule 12b arranged inside the insertion hole 12d. The ferrule 12b has a connection end face 12c from which four fiber holes 12h open. The ferrule 12b also has a pair of guide pins 12g extending from the connection end face 12c. Each input optical fiber 20 is inserted into the fiber hole 12h so that its tip is positioned at the connection end face 12c and is held by the ferrule 12b. A key 12e is formed inside the insertion hole 12d. The shapes of the insertion hole 12d, the key 12e, and the guide pin 12g correspond to the shapes of the plug portion 60d, the key groove 60e, and the guide hole 60g, respectively.

[0024] As shown in FIG. 2, the input port 12 according to this embodiment is fitted with a cap 12f capable of closing the receptacle 12a. The user removes the cap 12f and inserts the connector 60a into the receptacle 12a so that the key 12e and the key groove 60e are engaged and the guide pin 12g is inserted into the guide hole 60g (see also FIGS. 3A and 3B). This allows the connection optical cable C2 to be connected to the input port 12. More specifically, by abutting the connection end face 60c of the ferrule 60b against the connection end face 12c of the ferrule 12b, the multiple connection optical fibers 60 and the multiple input optical fibers 20 can be connected one-to-one.

[0025] As shown in FIG. 3A, in this embodiment, the four connection optical fibers 60 are referred to as a first connection optical fiber 61, a second connection optical fiber 62, a third connection optical fiber 63, and a fourth connection optical fiber 64. That is, the four connection optical fibers 60 are respectively assigned numbers (ordinal numbers) 1 to 4 (first to fourth). In this embodiment, the number of each connection optical fiber 60 corresponds to the position of the connection optical fiber 60 in the ferrule 60b. More specifically, the number of each connection optical fiber 60 corresponds to which fiber hole 60h the connection optical fiber 60 is inserted through. For example, in the example of FIG. 3A, the first connection optical fiber 60 from the left is numbered "1," and the second connection optical fiber 60 from the left is numbered "2." Note that the correspondence (order) between the fiber holes 60h and the numbers is not limited to the example shown in the figure. The correspondence between the positions of the fiber holes 60h and the numbers may be the same for all connection optical cables C2 included in the optical network NW1. Alternatively, the correspondence between the positions and numbers of the fiber holes 60h may be common only in some of the connecting optical cables C2.

[0026] As shown in FIG. 3B, the input optical fibers 20 are also numbered 1 to 4, similar to the connection optical fibers 60. Specifically, the input optical fiber 20 connected to the first connection optical fiber 61 is referred to as the first input optical fiber 21. Similarly, the input optical fibers 20 connected to the second connection optical fiber 62 to the fourth connection optical fiber 64 are referred to as the second input optical fiber 22 to the fourth input optical fiber 24, respectively. As described above, the connection optical fiber 60 and the input optical fiber 20 are connected by abutting the connection end face 60c of the ferrule 60b with the connection end face 12c of the ferrule 12b. Therefore, the number of each input optical fiber 20 corresponds to the position of the input optical fiber 20 in the input port 12 (ferrule 12b), i.e., the position where the input optical fiber 20 is inserted into the multiple fiber holes 12h. For example, in the example of FIG. 3B, the first input optical fiber 20 from the right is numbered "1," and the second input optical fiber 20 from the right is numbered "2."

[0027] Although not shown in the figure, the output port 14 has a similar configuration to the input port 12. That is, the output port 14 has four output optical fibers 40, and the output port 14 is provided with a receptacle 14a into which a connector 60a is inserted. The "output optical fiber 40" is a general term for an optical fiber that transmits an optical signal demultiplexed by a wavelength demultiplexer 50 (described later) to a connection optical fiber 60. The output optical fiber 40 is disposed inside the housing 10. A user can connect the connection optical cable C2 to the output port 14 by removing the cap 14f and inserting the connector 60a into the receptacle 14a, thereby connecting the multiple connection optical fibers 60 to the multiple output optical fibers 40 one-to-one. The output optical fibers 40 are also numbered 1 to 4, similar to the input optical fibers 20. Specifically, the output optical fibers 40 connected to the first connection optical fiber 61 to the fourth connection optical fiber 64 are referred to as the first output optical fiber 41 to the fourth output optical fiber 44, respectively. Similar to the numbering of each input optical fiber 20 , the numbering of each output optical fiber 40 corresponds to the position of that output optical fiber 40 at the output port 14 .

[0028] As shown in FIG. 4A, each supply optical cable C3 has one supply optical fiber 70. The "supply optical fiber 70" is a general term for an optical fiber that transmits an optical signal received from a distribution optical fiber 30 (described later) to a subscriber terminal 120. The supply optical fiber 70 is disposed outside the housing 10. In this embodiment, one end of the supply optical cable C3 is connectorized. In other words, a (single-core) connector 70a is provided at one end of the supply optical cable C3. The connector 70a has a ferrule 70b having a connection end face 70c and a cylindrical plug portion 70d. One fiber hole 70h is opened in the connection end face 70c. The supply optical fiber 70 is inserted through the fiber hole 70h so that its tip is positioned at the connection end face 70c and is held by the ferrule 70b. The ferrule 70b is positioned radially inside the plug portion 70d. The plug portion 70d is formed with a key groove 70e recessed radially inward from the outer circumferential surface of the plug portion 70d.

[0029] As shown in FIG. 4B , each distribution port 13 has one distribution optical fiber 30. The “distribution optical fiber 30” is a general term for an optical fiber that transmits an optical signal extracted by a wavelength demultiplexer 50 (described later) to a supply optical fiber 70. The distribution optical fiber 30 is disposed within the housing 10. The distribution port 13 is provided with a receptacle 13a into which a connector 70a is inserted. The receptacle 13a has an insertion hole 13d into which a plug portion 70d is inserted and a ferrule 13b disposed inside the insertion hole 13d. The ferrule 13b has a connection end face 13c from which one fiber hole 13h opens. The distribution optical fiber 30 is inserted into the fiber hole 13h so that its tip is positioned at the connection end face 13c and is held by the ferrule 13b. A key 13e is formed inside the insertion hole 13d. The shapes of the insertion hole 13d and the key 13e correspond to the shapes of the plug portion 70d and the key groove 70e, respectively.

[0030] 2 and inserting the connector 70a into the receptacle 13a so that the key 13e and the key groove 70e fit together, the user can connect the supply optical cable C3 to the distribution port 13. More specifically, the supply optical fiber 70 and the connection optical fiber 60 can be connected by abutting the connection end face 70c of the ferrule 70b against the connection end face 13c of the ferrule 13b.

[0031] Next, the internal wiring of the terminals 1A to 1D and the connection between the terminals 1A to 1D using the connecting optical cable C2 will be described.

[0032] As shown in Fig. 5, terminal 1A is equipped with four wavelength demultiplexers 50A. Similarly, terminal 1B is equipped with four wavelength demultiplexers 50B, terminal 1C is equipped with four wavelength demultiplexers 50C, and terminal 1D is equipped with four wavelength demultiplexers 50D. Although detailed illustration is omitted, wavelength demultiplexers 50A to 50D are housed in housings 10 of terminals 1A to 1D, respectively. Hereinafter, when there is no need to particularly distinguish between wavelength demultiplexers 50A to 50D, they may be simply referred to as "wavelength demultiplexers 50."

[0033] In each terminal 1, the input optical fibers 21-24 are connected one-to-one to the connecting optical fibers 61-64 and the four wavelength demultiplexers 50. In other words, the number of wavelength demultiplexers 50 is equal to the number of connecting optical fibers 61-64 that input optical signals to the terminal 1, and the wavelength demultiplexers 50 correspond one-to-one to the connecting optical fibers 61-64. In addition, the output optical fibers 41-44 are connected one-to-one to the connecting optical fibers 61-64 and the four wavelength demultiplexers 50. As a result, for example, the output optical fibers 41-44 of terminal 1A are connected to the input optical fibers 21-24 of terminal 1B via the connecting optical fibers 61-64, respectively. Terminals 1B-1D are connected in a similar manner.

[0034] 5, the number of wavelength demultiplexers 50 is the same as the number of distribution ports 13, and the wavelength demultiplexers 50 and the distribution ports 13 are connected one-to-one by distribution optical fibers 30. In other words, in the example shown in Fig. 5, one wavelength demultiplexer 50 is connected to one input optical fiber 20, one distribution optical fiber 30, and one output optical fiber 40.

[0035] The wavelength demultiplexer 50 demultiplexes an optical signal input from the input optical fiber 20 into a distribution optical fiber 30 and an output optical fiber 40 according to the wavelength of the optical signal. More specifically, each wavelength demultiplexer 50 according to this embodiment is set with a certain wavelength band B. The wavelength demultiplexer 50 extracts optical signals belonging to wavelength band B from the input optical signals and outputs them to the distribution optical fiber 30. The wavelength demultiplexer 50 also outputs all optical signals from the input optical signals that do not belong to wavelength band B to the output optical fiber 40. In other words, the wavelength demultiplexer 50 outputs all optical signals from the input optical signals that were not output to the distribution optical fiber 30 to the output optical fiber 40. The wavelength demultiplexer 50 is also referred to as a WDM (Wavelength Division Multiplexing) module. The optical signals output to the distribution optical fiber 30 are transmitted to the subscriber terminal 120 via the supply optical cable C3 (supply optical fiber 70) (see also FIG. 1 ).

[0036] 5, the optical signals output to the output optical fibers 41-44 are extracted to the outside of the housing 10 and input to the input optical fibers 21-24 of the next terminal 1 via the connection optical fibers 61-64. For example, the optical signals output from the output optical fibers 41-44 of the terminal 1A are input to the input optical fibers 21-24 of the terminal 1B.

[0037] In this embodiment, the input optical fibers 20 and output optical fibers 40 connected to a certain wavelength demultiplexer 50 are assigned the same number (ordinal number). In other words, the input optical fibers 20 and output optical fibers 40 assigned the same number (ordinal number) are connected one-to-one via the wavelength demultiplexer 50. For example, a first input optical fiber 21 and a first output optical fiber 41 are connected to the same wavelength demultiplexer 50.

[0038] The set value of the wavelength band B described above can be changed by the user as appropriate depending on the design of the optical network NW1. In this embodiment, the wavelength band B set for each of the four wavelength demultiplexers 50A is the same. Similarly, the wavelength band B set for each of the four wavelength demultiplexers 50B is the same. The wavelength band B set for each of the four wavelength demultiplexers 50C is the same. The wavelength band B set for each of the four wavelength demultiplexers 50D is the same. Hereinafter, the wavelength band set for the wavelength demultiplexer 50A will be referred to as the first wavelength band B1, the wavelength band set for the wavelength demultiplexer 50B will be referred to as the second wavelength band B2, the wavelength band set for the wavelength demultiplexer 50C will be referred to as the third wavelength band B3, and the wavelength band set for the wavelength demultiplexer 50D will be referred to as the fourth wavelength band B4. In this embodiment, the wavelength bands B1 to B4 are different from one another. That is, the wavelengths of the optical signals extracted by the wavelength demultiplexers 50A to 50D and output to the distribution optical fiber 30 are different for each of the terminals 1A to 1D.

[0039] Next, the operation of the optical network NW1 configured as above will be described.

[0040] When optical signals are distributed to each subscriber terminal 120 using the optical network NW1, an optical signal S is transmitted from the central office 100 to each of the connecting optical fibers 61 to 64 via the distribution optical cable C1 and the closure 110 (see FIGS. 1 and 5 below). In this embodiment, the optical signal S includes an optical signal S1 belonging to a first wavelength band B1, an optical signal S2 belonging to a second wavelength band B2, an optical signal S3 belonging to a third wavelength band B3, and an optical signal S4 belonging to a fourth wavelength band B4.

[0041] For example, an optical signal S transmitted from the central office 100 to the first connecting optical fiber 61 is first input to a wavelength demultiplexer 50A included in the terminal 1A. The wavelength demultiplexer 50A extracts an optical signal S1 from the optical signal S and outputs it to the distribution optical fiber 30. As a result, the optical signal S1 is transmitted to the subscriber terminal 120 connected to the distribution port 13 of the terminal 1A. The wavelength demultiplexer 50A also outputs the remaining optical signal S (i.e., optical signals S2 to S4) to the first output optical fiber 41.

[0042] The optical signal S including the optical signals S2 to S4 is input to the wavelength demultiplexer 50B of the terminal 1B. The wavelength demultiplexer 50B extracts the optical signal S2 from the optical signal S and outputs it to the distribution optical fiber 30. As a result, the optical signal S2 is transmitted to the subscriber terminal 120 connected to the distribution port 13 of the terminal 1B. The wavelength demultiplexer 50B also outputs the remaining optical signal S (i.e., the optical signals S3 and S4) to the first output optical fiber 41.

[0043] The optical signal S including optical signals S3 and S4 is input to the wavelength demultiplexer 50C of the terminal 1C. The wavelength demultiplexer 50C extracts the optical signal S3 from the optical signal S and outputs it to the distribution optical fiber 30. The wavelength demultiplexer 50C outputs the remaining optical signal S (i.e., the optical signal S4) to the first output optical fiber 41. The optical signal S including the optical signal S4 is input to the wavelength demultiplexer 50D of the terminal 1D. The wavelength demultiplexer 50D extracts the optical signal S4 from the optical signal S and outputs it to the distribution optical fiber 30. In this way, in the optical network NW1 of this embodiment, the optical signal S sent from the central office 100 to the first connection optical fiber 61 is input once to each of the wavelength demultiplexers 50A to 50D.

[0044] The above has described the optical signal S sent from the central office 100 to the first connecting optical fiber 61, but the optical signals S sent from the central office 100 to the second connecting optical fiber 62 to the fourth connecting optical fiber 64 are also input once to each of the wavelength demultiplexers 50A to 50D using the same principle as above. With this configuration, optical signals S1 to S4 can be extracted from each optical signal S sent from the central office 100 to the connecting optical fibers 61 to 64, and the optical signals can be distributed to each subscriber terminal 120.

[0045] As described above, the terminal 1 according to this embodiment is a terminal 1 that inputs and outputs optical signals from a plurality of optical fibers 60 in the optical cable C2, and includes a housing 10, an input port 12 that introduces an optical signal into the housing 10, a plurality of wavelength demultiplexers 50 that receive the optical signal introduced from the input port 12 and demultiplex the optical signal into a predetermined wavelength band and other wavelength bands, a distribution port 13 that distributes the optical signals of the predetermined wavelength band demultiplexed by the wavelength demultiplexer 50 to external terminals (subscriber terminals 120), and an output port 14 that extracts the optical signals of the other wavelength bands demultiplexed by the wavelength demultiplexer 50 to the outside of the housing 10. The number of wavelength demultiplexers 50 included in each terminal 1 is equal to the number of optical fibers 60 that input optical signals to the terminal 1, and one of the plurality of wavelength demultiplexers 50 is connected to one of the plurality of optical fibers 60.

[0046] By preparing a plurality of terminals 1 having this configuration and connecting the plurality of terminals 1 with connecting optical fibers 61 to 64, it is possible to realize a chained optical network NW1 capable of distributing optical signals from the central office 100 to the subscriber terminals 120. Furthermore, in the realized optical network NW1, unlike the optical network disclosed in Patent Document 1, for example, the number of optical fibers 60 (connecting optical fibers 61 to 64) that input optical signals to the terminals 1 is equal to the number of connecting optical fibers 61 to 64 that output optical signals from the terminals 1. Therefore, compared to the optical network disclosed in Patent Document 1, for example, it is possible to maintain the effective density of the connecting optical fibers 61 to 64 throughout the entire optical network NW1.

[0047] Furthermore, the terminal 1 according to this embodiment includes a plurality of wavelength demultiplexers 50, and the same wavelength band B is set for each of the plurality of wavelength demultiplexers 50. With this configuration, an optical network NW1 capable of distributing optical signals to subscriber terminals 120 can be easily realized.

[0048] (Second embodiment) Next, a second embodiment will be described, but the basic configuration is similar to that of the first embodiment. Therefore, the same components are given the same reference numerals, and the description thereof will be omitted, and only the differences will be described.

[0049] As shown in Figure 6, in the optical network NW2 according to this embodiment, the first terminal 2A, terminal 2B, terminal 2C, and terminal 2D each include one wavelength demultiplexer 50A to 50D. As a result, the four terminals 2A to 2D have a common configuration. Hereinafter, when there is no need to distinguish between the terminals 2A to 2D, they may be simply referred to as "terminal 2."

[0050] In this embodiment, the first input optical fiber 21 and the fourth output optical fiber 44 are connected via a wavelength demultiplexer 50A. The second input optical fiber 22 and the first output optical fiber 41 are connected via a wavelength demultiplexer 50B. The third input optical fiber 23 and the second output optical fiber 42 are connected via a wavelength demultiplexer 50C. The fourth input optical fiber 24 and the third output optical fiber 43 are connected via a wavelength demultiplexer 50D. In other words, the numbers (ordinal numbers) assigned to the input optical fiber 20 and the output optical fiber 40 connected via the wavelength demultiplexer 50 are different from each other. In other words, the positions of the connected input optical fiber 20 and output optical fiber 40 at the input port 12 (the inserted fiber hole 12h) and at the output port 14 (the inserted fiber hole 14h) are different.

[0051] Such an optical network NW2 can also distribute optical signals from the central office 100 to each subscriber terminal 120. For example, an optical signal S transmitted from the central office 100 to the first connecting optical fiber 61 is first input to a wavelength demultiplexer 50A included in the terminal 2A. The wavelength demultiplexer 50A extracts an optical signal S1 from the optical signal S and outputs it to the distribution optical fiber 30. The wavelength demultiplexer 50A also outputs the remaining optical signal S (i.e., optical signals S2 to S4) to the fourth output optical fiber 44.

[0052] Optical signal S including optical signals S2 to S4 is input to wavelength demultiplexer 50D of terminal 2B. Wavelength demultiplexer 50D extracts optical signal S4 from optical signal S and outputs it to distribution optical fiber 30. Wavelength demultiplexer 50D also outputs the remaining optical signal S (i.e., optical signals S2 and S3) to third output optical fiber 43.

[0053] The optical signal S including optical signals S2 and S3 is input to a wavelength demultiplexer 50C included in the terminal 2C. The wavelength demultiplexer 50C extracts optical signal S3 from the optical signal S and outputs it to the distribution optical fiber 30. The wavelength demultiplexer 50C outputs the remaining optical signal S (i.e., optical signal S2) to the second output optical fiber 42. The optical signal S including optical signal S2 is input to a wavelength demultiplexer 50B included in the terminal 2D. The wavelength demultiplexer 50B extracts optical signal S2 from the optical signal S and outputs it to the distribution optical fiber 30. In this way, also in the optical network NW2 according to this embodiment, the optical signal S sent from the first connection optical fiber 61 is input once to each of the wavelength demultiplexers 50A to 50D.

[0054] While the optical signal S transmitted from the central office 100 to the first connecting optical fiber 61 has been described above, the optical signal S transmitted from the central office 100 to the second connecting optical fiber 62 to the fourth connecting optical fiber 64 is also configured to be input once to all of the wavelength demultiplexers 50A to 50D. More specifically, as shown in FIG. 6 , for two mutually connected terminals 2 (e.g., terminals 2A and 2B), a plurality of wavelength demultiplexers 50 included in one terminal 2 are connected one-to-one to a plurality of wavelength demultiplexers 50 included in the other terminal 2. Furthermore, the wavelength bands B set for the two connected wavelength demultiplexers 50 are different from each other. With this configuration, optical signals S1 to S4 can be extracted from each optical signal S transmitted from the central office 100 to the connecting optical fibers 61 to 64, and the optical signals can be distributed to each subscriber terminal 120.

[0055] As described above, the terminal 2 according to this embodiment includes a plurality of wavelength demultiplexers 50A-50D, and the wavelength bands B1-B4 set for the plurality of wavelength demultiplexers 50A-50D are different from one another. By configuring the optical network NW2 using a plurality of terminals 2 having this configuration, the configuration of each terminal 2 can be made common throughout the entire optical network NW2. This allows the cost of manufacturing the terminals 2 to be reduced.

[0056] Furthermore, when an optical fiber that transmits an optical signal from the input port 12 to the wavelength demultiplexer 50 is defined as an input optical fiber 20, and an optical fiber that transmits an optical signal from the wavelength demultiplexer 50 to the output port 14 is defined as an output optical fiber 40, the multiple input optical fibers 20 and the multiple output optical fibers 40 are connected one-to-one via the wavelength demultiplexer 50, and the connected input optical fibers 20 and output optical fibers 40 have mutually different positions (numbers, ordinal numbers) at the input port 12 and positions (numbers, ordinal numbers) at the output port 14. By preparing multiple terminals 2 having this configuration and connecting the terminals 2 with a connecting optical cable C2 having a connector 60a at its end, an optical network NW2 capable of distributing optical signals to subscriber terminals 120 can be easily realized.

[0057] Moreover, the optical network NW2 according to this embodiment is an optical network NW2 having a plurality of the above-mentioned terminals 2, and the plurality of terminals 2 include a first terminal 2A and a second terminal 2B, and the plurality of wavelength demultiplexers 50 of the first terminal 2A are connected one-to-one with the plurality of wavelength demultiplexers 50 of the second terminal 2B, and the wavelength demultiplexers 50 of the connected first terminal 2A and the wavelength demultiplexer 50 of the second terminal 2B have different wavelength bands B set. With this configuration, it is possible to more reliably realize an optical network NW2 capable of distributing optical signals to subscriber terminals 120.

[0058] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0059] For example, in the above embodiment, the optical networks NW1 and NW2 each include four terminals 1 and 2, but the number of terminals 1 and 2 may be any number greater than or equal to 1. The number of input optical fibers 20, distribution optical fibers 30, output optical fibers 40, connection optical fibers 60, and wavelength demultiplexers 50 may be any number greater than or equal to 1.

[0060] Furthermore, the end of the connecting optical cable C2 does not have to be connectorized. In other words, the terminal 1 does not have to have ports 12, 14 provided with receptacles 12a, 14a. In this case, the optical fibers 20, 40 and the connecting optical fiber 60 may be connected by fusion splicing. Similarly, the end of the supply optical cable C3 does not have to be connectorized, and the distribution port 13 does not have to be provided with a receptacle 13a.

[0061] Furthermore, the multiple connection optical fibers 60 may be color-coded according to the numbers (ordinal numbers) assigned to each connection optical fiber 60. Similarly, the multiple input optical fibers 20 may be color-coded. The multiple output optical fibers 40 may be color-coded. Furthermore, with regard to the connection optical fibers 60, the input optical fibers 20, and the output optical fibers 40, optical fibers that have the same assigned number may be colored the same color.

[0062] Furthermore, in the above embodiment, only one wavelength band B is set in the wavelength demultiplexer 50, but multiple wavelength bands may be set in the wavelength demultiplexer 50. In this case, the wavelength demultiplexer 50 may be connected to the same number of distribution optical fibers 30 (distribution ports 13, subscriber terminals 120) as the number of set wavelength bands B.

[0063] In addition, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0064] 1, 2...Terminal 2A...First terminal 2B...Second terminal 10...Housing 12...Input port 13...Distribution port 14...Output port 20...Input optical fiber 30...Distribution optical fiber 40...Output optical fiber 50...Wavelength demultiplexer 60...Connection optical fiber 120...Subscriber terminal (external terminal)

Claims

1. A terminal for inputting and outputting optical signals from a plurality of optical fibers included in an optical cable, The housing and an input port for introducing the optical signal into the housing; a plurality of wavelength demultiplexers to which the optical signals taken in from the input ports are input and which demultiplex the optical signals into a predetermined wavelength band and other wavelength bands; a distribution port that distributes optical signals of a predetermined wavelength band demultiplexed by the wavelength demultiplexer to an external terminal; an output port for extracting optical signals other than the predetermined wavelength band demultiplexed by the wavelength demultiplexer to the outside of the housing, the number of the wavelength demultiplexers is equal to the number of the plurality of optical fibers; a terminal, in which one of the plurality of wavelength demultiplexers is connected to one of the plurality of optical fibers;

2. When an optical fiber that transmits an optical signal from the input port to the wavelength demultiplexer is defined as an input optical fiber, and an optical fiber that transmits an optical signal from the wavelength demultiplexer to the output port is defined as an output optical fiber, the input optical fiber and the output optical fiber are connected in a one-to-one relationship via the wavelength demultiplexer; The input optical fiber and the output optical fiber connected to each other are positioned at different positions in the input port and the output port. The terminal of claim 1 .

3. Only one wavelength band is set in the wavelength demultiplexer.

3. A terminal according to claim 1 or 2.

4. A plurality of wavelength bands are set in the wavelength demultiplexer.

3. A terminal according to claim 1 or 2.

5. a plurality of the wavelength demultiplexers; The wavelength bands set for the plurality of wavelength demultiplexers are the same. A terminal according to claim 1 or claim 2.

6. a plurality of the wavelength demultiplexers; The wavelength bands set for the plurality of wavelength demultiplexers are different from one another. A terminal according to claim 1 or claim 2.

7. An optical network comprising a plurality of terminals according to claim 1 or 2.

8. An optical network having a plurality of terminals according to claim 6, the terminals include a first terminal and a second terminal; the plurality of wavelength demultiplexers included in the first terminal are connected to the plurality of wavelength demultiplexers included in the second terminal in a one-to-one relationship; An optical network, wherein the wavelength bands set in the wavelength demultiplexer of the first terminal and the wavelength demultiplexer of the second terminal connected to each other are different from each other.

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