JP2004274616A - Optical brunching device, optical inserting device, and optical branching/inserting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical branching/inserting device suitable for both downsizing and for an optical wavelength multiplex communication network, especially a transmission system which is cost effective. <P>SOLUTION: First and second common ports 11 and 12 are connected to an optical transmission path. An optical multiplexer/demultiplexer (passing means) 13 outputs the signal light other than a specific wavelength signal light (λ<SB>DROP</SB>) among the multiple wavelength signal light which is transmitted from an arbitrary point C and inputted into the first common port 11 to the second common port 12. An optical multiplexer/demultiplexer (branching means) 13 takes a specific wavelength signal light (λ<SB>DROP</SB>) out of the multiple wavelength signal light transmitted in an optical transmission path 2 (2A and 2B), and outputs it to a light receiving part 3. A fixed optical attenuator 16 that has a function to attenuate the optical intensity level of the specific signal wavelength light (λ<SB>DROP</SB>) to the light receiving level of the light receiving part 3, is attached between the optical multiplexer/demultiplexer (branching means) 13 and the light receiving part 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical communication system such as an optical wavelength division multiplexing communication network, and more particularly to an optical branching device, an optical inserting device, and an optical adding / dropping device capable of passing, dropping, and inserting signal light of a specific wavelength. .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an optical add / drop multiplexer, a specific wavelength signal light is split from wavelength multiplexed signal light transmitted in one direction in an optical transmission line, and the split light is input to an optical receiver to extract information and transmit light. There is known a configuration in which a specific wavelength signal light output from a device is inserted in the same direction of a transmission line.
[0003]
Further, in this optical add / drop multiplexer, the optical intensity level of the signal light input to the optical receiver used in combination with the optical add / drop multiplexer is suppressed to a light receiving range permitted by the optical receiver. An optical attenuator (attenuator) is provided for protection, and an optical attenuator configured to adjust the light intensity is known (for example, see Patent Document 1).
Similarly, in the optical add / drop multiplexer described in Patent Document 1, when the specific wavelength signal light output from the optical transmitter is inserted in the same direction of the transmission line, the optical level is adjusted to the optical level of the wavelength multiplexed signal light. In order to perform the adjustment, the optical attenuator described above is also provided.
[0004]
This will be specifically described below with reference to the drawings.
FIG. 5 shows a conventional optical add / drop device. The optical add / drop device 110 includes a specific optical add / drop filter 101 provided at a specific point of the optical transmission line 100 through which the wavelength multiplexed signal light is transmitted. From the wavelength multiplexed signal light being transmitted by the optical add / drop filter 101, a signal light (λ_i) Is branched and output to an optical receiver 102 installed at a specific point, and an optical transmission line 103 for guiding a specific wavelength signal light, and a first variable line provided on the optical transmission line 103 are provided. A specific wavelength signal light (λ) is transmitted from an optical attenuator 104 and an optical transmitter 105 installed at a specific point by a specific optical add / drop filter 101._j) Is provided, and an optical transmission line 106 is provided for multiplexing the optical signals. A second variable optical attenuator 107 is provided on the optical transmission line 106.
[0005]
By the way, in such an optical add / drop multiplexer, in order to protect a PD (Photo Diode) or an APD (Avalanche Photo Diode) which is an optical element, an optical attenuation is required to suppress the light intensity of signal light to a predetermined level. Usually, a variable optical attenuator as described above is used as the device. As this variable optical attenuator, for example, one having a configuration in which two disks are arranged close to and opposed to each other coaxially and concentrically, and these disks are relatively rotatable is known. Specifically, a rotatable translucent disk formed by continuously changing the film thickness of a metal deposition film or the like along the circumferential direction of the surface, and light can be transmitted only to a part thereof A configuration using a disc provided with a through hole is known.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-186085 (page 3, left column [0010], [0010] FIG. 1)
[0007]
[Problems to be solved by the invention]
By the way, in such a conventional optical add / drop multiplexer, as the optical attenuator, the variable optical attenuator as described above is often used, but this variable optical attenuator is the same as the optical attenuator described above. As described above, there is a problem that the size is large, the cost is high, and the price cannot be reduced because of the mechanical structure.
[0008]
On the other hand, among such optical attenuators, in addition to the above-described variable optical attenuators, for example, fixed optical attenuators in which a predetermined metal material or the like is vapor-deposited so as to provide a constant attenuation are also known. Have been.
[0009]
By the way, each signal light that is to be taken out by taking out such an optical add / drop device is, of course, transmitted from another point different from the installation point of the optical add / drop device. Each signal light is not transmitted from the same point at the same transmission distance. Therefore, the amount of signal light attenuation until reaching the optical receiver at the point where the optical attenuator is installed is not the same.
On the other hand, for an optical receiver that receives signal light, the range of proper light reception intensity originally possessed is fixed, and it is necessary to attenuate and adjust the light intensity of signal light accordingly. From the above-described circumstances, the amount of attenuation of each signal light varies depending on the transmission distance of each signal light and the like.
[0010]
Therefore, when installing an optical attenuator in this optical add / drop multiplexer, first, at the installation site or the like, for example, while measuring the light intensity of the signal light to be transmitted in the transmission path, and the like, The optical attenuator is initially adjusted to attenuate the light intensity from the measured light intensity to an appropriate range of the optical receiver to be used.
[0011]
However, usually, in such an optical attenuator, once the initial adjustment is performed, subsequent adjustment work is not required, so that it is not always necessary to use the above-described variable optical attenuator.
[0012]
Recently, a system has been constructed in which the add / drop wavelengths are not single, but a plurality of wavelengths are dropped / added. For this reason, in the conventional add / drop wavelength device for dropping / adding signal lights of a plurality of wavelengths as described above, it is necessary to prepare additional optical attenuators by the number (type) of the wavelengths to be dropped / added. Therefore, if the above-mentioned variable optical attenuator is used, further cost merit is not expected.
[0013]
The present invention has been made to solve these problems, and is suitable for an optical wavelength division multiplexing communication network, particularly a transmission system requiring a cost merit, and is advantageous in miniaturization, an optical branching device, an optical insertion device, and an optical communication device. It is an object to provide a drop-and-insert device.
[0014]
[Means for Solving the Problems]
The optical branching device according to the present invention is configured to transmit a specific wavelength signal light among wavelength multiplexed signal lights being transmitted in an optical transmission line provided between at least two different points, and to convert the wavelength multiplexed signal light at a specific point between the two points. An optical branching device for selectively branching out from inside and outputting to an optical receiving unit provided at the specific point,
First and second common ports connected to the optical transmission line at the specific point;
From the wavelength multiplexed signal light to be transmitted and transmitted through the optical transmission line from any point including the two points and input to one of the first and second common ports, the wavelength multiplexed signal light other than the specific wavelength signal light is used. Passing means for outputting the signal light to one of the first and second common ports;
Branching means for selectively branching out the specific wavelength signal light from the wavelength multiplexed signal light being transmitted in the optical transmission line, extracting the specific wavelength signal light, and outputting the extracted signal light to the optical receiver,
A selected fixed optical attenuator having a predetermined attenuation function so that the light intensity level of the branched specific signal wavelength light becomes a light receiving level allowed in the optical receiving unit, the branching unit and the optical receiving unit It is characterized by being installed between
[0015]
As a result, since a small and inexpensive fixed optical attenuator is used for the optical attenuator, an optical branching device that is suitable for an optical wavelength division multiplexing communication network, particularly a transmission system that requires a cost merit, and that is convenient for miniaturization. Can be provided.
[0016]
Further, the optical branching device according to the present invention is characterized in that the fixed optical attenuator is composed of a plurality of fixed optical attenuators, and adjacent ones are arranged alternately and interchangeably.
[0017]
Thereby, the attachment / detachment operation of the fixed optical attenuator can be reliably performed without using a jig, and the size of the fixed optical attenuator can be further reduced, so that the optical branching device can be further reduced in size. .
[0018]
In addition, the optical insertion apparatus of the present invention may be arranged such that the wavelength multiplexing signal light transmitted at least in an optical transmission line provided between two different points is transmitted from an optical transmitter provided at a specific point between the two points to the wavelength multiplexing. An optical insertion device that emits a signal light having a specific wavelength different from the signal light and combines the signal light having the specific wavelength with the wavelength multiplexed signal light,
First and second common ports connected to the optical transmission line at the specific point;
With multiplexing means for taking in the signal light of the specific wavelength output from the optical transmission unit provided at the specific point and multiplexing with the wavelength multiplexed signal light,
When the signal light of the specific wavelength is inserted into the optical transmission line through which the wavelength multiplexed signal light is transmitted and multiplexed with the wavelength multiplexed signal light, the light intensity level of the signal light of the specific wavelength is changed to the wavelength multiplexed signal light. A fixed optical attenuator having a predetermined attenuating function so as to match the light intensity level of the optical transmitter is mounted between the multiplexing means and the optical transmitter.
[0019]
As a result, a small and inexpensive fixed optical attenuator is used for the optical attenuator, so an optical insertion device suitable for an optical wavelength division multiplexing communication network, particularly a transmission system requiring a cost merit, and advantageous for miniaturization. Can be provided.
[0020]
Further, the optical insertion device of the present invention is characterized in that the fixed optical attenuator is composed of a plurality of fixed optical attenuators, and adjacent ones are arranged alternately and interchangeably.
[0021]
Thereby, the attachment / detachment operation of the fixed optical attenuator can be reliably performed without using a jig, and the size of the fixed optical attenuator can be further reduced, so that the optical insertion device can be further reduced in size. .
[0022]
Furthermore, the optical add / drop multiplexer of the present invention selectively transmits a specific wavelength signal light among wavelength-multiplexed signal lights being transmitted in an optical transmission line provided between different points from the wavelength-multiplexed signal light at a specific point. The signal is branched and output to an optical receiving unit provided at the specific point, and the wavelength multiplexed signal light being transmitted in the optical transmission line is transmitted from the optical transmitting unit provided at the specific point to the wavelength. An optical add-drop multiplexer that emits signal light having a specific wavelength different from the multiplexed signal light and combines the specific wavelength signal light with the wavelength multiplexed signal light,
First and second common ports respectively connected to the optical transmission line at the specific point;
The specific wavelength signal light is selected from the wavelength multiplexed signal light transmitted and transmitted through the optical transmission line from any one of the two points and input to at least one of the first and second common ports. Passing means for outputting the other signal light to the other of the first and second common ports;
Branching means for selectively branching out the specific wavelength signal light from the wavelength multiplexed signal light transmitted in the optical transmission line, extracting the specific wavelength signal light, and outputting the extracted signal light to the optical receiver;
Combining means for taking in the signal light of the specific wavelength output from the optical transmission unit and multiplexing with the wavelength multiplexed signal light transmitted in the optical transmission line,
A predetermined light output level of the specific signal wavelength light branched by the branching means from the wavelength multiplexed signal light transmitted in the optical transmission line is a predetermined light reception level allowed by the light receiving unit. A selected first fixed optical attenuator having an attenuating function is provided between the branching unit and the optical receiving unit, and
When the wavelength multiplexed signal light and the signal light of the specific wavelength output from the optical transmitter are multiplexed by the multiplexing means, the light intensity level of the signal light of the specific wavelength is light of the wavelength multiplexed signal light. A selected second fixed optical attenuator having a predetermined attenuation function that matches the intensity level is provided between the multiplexing unit and the optical transmission unit.
[0023]
As a result, since a small and inexpensive fixed optical attenuator is used as the optical attenuator, it is suitable for an optical wavelength division multiplexing communication network, particularly a transmission system requiring a cost advantage, and an optical add / drop device which is advantageous for miniaturization. Can be provided.
[0024]
Further, in the optical add / drop multiplexer of the present invention, at least the first fixed optical attenuator or the second fixed optical attenuator is composed of a plurality of the fixed optical attenuators, and the first fixed optical attenuator adjacent to the first fixed optical attenuator. The second fixed optical attenuators are arranged alternately and interchangeably between each other or adjacent to each other.
[0025]
As a result, the fixed optical attenuator can be reliably attached and detached without using a jig, and the fixed optical attenuator can be further miniaturized, so that the optical add / drop device can be further miniaturized. Become.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a configuration of an optical add / drop multiplexer 1 according to an embodiment of the present invention. This optical add / drop multiplexer 1 is provided with an optical transmission line 2A installed between point A and point B. It is installed at an arbitrary point C on the way, and is connected to the optical receiving unit 3 and the optical transmitting unit 4 provided at the same point C.
In the case of the present embodiment, the optical add / drop multiplexer 1, the optical receiving unit 3 and the optical transmitting unit 4 are installed in a local broadcasting station at point C. The target to which this communication system is applied is not particularly limited to communication between broadcasting stations as in this embodiment. That is, for example, it can be installed in various facilities and buildings such as banks, companies, newspaper companies, telephone stations and relay stations, and applied to various systems.
Further, in the present embodiment, as shown in FIG. 2, a hierarchical (hierarchical) system structure having a point A as an upper layer is used. However, the present invention is not limited to this. The system structure of may be used.
[0027]
At point A, the same optical add / drop device and optical receiving unit and optical transmitting unit as those provided at the facility at point C will be installed, but these equipment at point A will have a key and It is installed inside a broadcasting station.
[0028]
At point B, the same optical add / drop device and a plurality of optical receivers and optical transmitters as the equipment at point C are installed. In the case of the embodiment, it is installed inside a local broadcasting station.
[0029]
As shown in FIG. 1, the optical add / drop multiplexer 1 includes first and second common ports 11 and 12, an optical multiplexer / demultiplexer 13, and an optical transmission line for each optical receiver 3. 14, each optical transmission line 15 for each optical transmission unit 4, and a first fixed optical attenuation for transmission provided in the middle of each optical transmission line 14 from the optical multiplexer / demultiplexer 13 to each optical reception unit 3. And a second fixed optical attenuator 17 for reception provided in the optical transmission path 15 from each optical transmission unit 4 to the optical add / drop filter 13.
[0030]
Among them, the first and second common ports 11 and 12 are respectively provided with appropriate optical connectors installed on the outer surface of the housing 10 of the optical add / drop multiplexer 1, for example, a single-core single mode optical fiber SC type (for example, SC type). JIS F04 type). It is to be noted that, as the optical connector, of course, various types other than the above, for example, FC type, MT type for multi-core, and the like can be appropriately applied.
In the present embodiment, the first and second common ports 11 and 12 are separately installed at opposite positions facing each other on the outer surface of the housing 10 of the branch insertion device 1. The optical fiber, which is the optical transmission line 2 </ b> C to be routed inside the optical fiber 10, may be housed in a state where the optical fiber is preliminarily processed at a predetermined radius of curvature, and may be arranged at one place as a configuration such as a two-row arrangement.
[0031]
The optical multiplexing / demultiplexing device (optical branching device) 13 performs demultiplexing (branching) and multiplexing (insertion) of the wavelength multiplexed signal light input or output to the first and second common ports 11 and 12. It is. In the present embodiment, the optical multiplexing / demultiplexing device 13 uses a silica-based optical fiber provided as the transmission line 2C in the housing 10 to transmit a fiber that is transmitted by a wavelength division multiplexing (WDM) method. From the near-infrared light (wavelength multiplexed signal light) such as the 1.3 μm band and 1.55 μm band with small loss, a specific wavelength signal light (λ_DROP) Is selectively branched and output to an optical receiving unit 3 (not shown), and a signal light (λ) having a specific wavelength output from the optical transmitting unit 4._ADD), And an optical multiplexer (optical multiplexer) (not shown) for multiplexing with the wavelength multiplexed signal light.
[0032]
For the optical demultiplexer or the optical multiplexer, for example, in the present embodiment, an interference film filter made of a dielectric multilayer film having wavelength selectivity or a fusion type optical fiber coupler as a directional coupler is used. Although it has a configuration with low loss and good isolation, other suitable means such as a diffraction grating (grating), a prism, and other suitable means can be applied. Note that this optical demultiplexer uses a specific wavelength signal light (λ_DROP), And the number of optical multiplexers is also equal to the signal light (λ_ADD) Are installed in the same number.
[0033]
The optical transmission line 14 has, for example, a single-wavelength single-mode optical fiber having a specific wavelength signal light (λ_DROP) Are arranged in the same number as that of the optical demultiplexer. In particular, in order to extract the signal light from the upward direction at the point A, the signal light is curved in a predetermined direction and connected to each optical demultiplexer.
The optical transmission line 15 also has a signal light (λ_{AD D}), And is curved in a predetermined direction and connected to each of the optical multiplexers so that the signal light can be transmitted in a certain upward direction at the point A.
[0034]
The first fixed optical attenuator 16 for the optical receiving unit is configured to split each specific signal wavelength light (λ) from the wavelength multiplexed signal light transmitted through the optical transmission line 2C._DROP) So that the optical output level of each specific signal wavelength light (λ_DROP) Is provided in the middle of each optical transmission line 14 connecting the optical multiplexer / demultiplexer 13 and the optical receiver 3. Therefore, each specific signal wavelength light (λ) branched from the optical multiplexer / demultiplexer 13_DROPIn (1), an optical power meter is attached in the middle of each optical transmission line 14 once at the initial stage of starting the system to measure the optical output level.
[0035]
In the present embodiment, the first fixed optical attenuator 16 does not have wavelength dependency. In other words, the first fixed optical attenuator 16 can exhibit a constant attenuating function for signal light of each wavelength. Therefore, for example, a metal film having a composition of nickel (Ni) and chromium (Cr) is deposited on a glass substrate. The fixed optical attenuator 16 is, of course, not limited to the one of the present embodiment. For example, when the signal light to be attenuated is limited to a signal light having a specific wavelength, there is a wavelength dependency. An interference film filter (dielectric multilayer film) may be formed as an attenuator.
[0036]
The second fixed optical attenuator 17 for the optical transmission unit has a light intensity level of the specific wavelength signal light to be inserted into each optical transmission line 2C through which the wavelength multiplexed signal light is transmitted and multiplexed, and the light intensity of the wavelength multiplexed signal light. The signal light of a specific wavelength (λ_ADD) Are attenuated, and are provided in the middle of the optical transmission path from the optical transmitter 4 to the optical multiplexer / demultiplexer 13. Therefore, the second fixed optical attenuator 17 also outputs the signal light (λ) of each specific wavelength emitted from the optical transmission unit 4._ADDIn (1), an optical power meter is attached in the middle of each optical transmission line 15 to measure an optical output level once in the initial stage of starting up the system.
[0037]
Similarly to the first fixed optical attenuator 16, the second fixed optical attenuator 17 is formed by depositing a metal film while avoiding the use of a dielectric multilayer film so as not to give wavelength dependency. It has become. The fixed optical attenuator 17 is, of course, not limited to the one in the present embodiment. For example, when the signal light to be attenuated is limited to that of a specific wavelength, there is wavelength dependency. An interference film filter (dielectric multilayer film) may be formed as an attenuator.
[0038]
The optical receiving unit 3 outputs the specific wavelength signal light (λ) branched from the optical multiplexer / demultiplexer 13._DROP) To extract information by using PD or APD, and a specific wavelength signal light (λ_DROP) Are installed in the same number.
[0039]
The optical transmission unit 4 transmits the signal light (λ_ADD) To the optical multiplexing / demultiplexing device 13 for multiplexing (inserting) with the wavelength-division multiplexed signal light transmitted through the optical transmission line 2C described above._ADD), And an LED (Light Emitting Diode) or an LD (Laser Diode) is used, and a signal light (λ) having a specific wavelength to be multiplexed is used._ADD) Are installed in the same number.
[0040]
Next, a specific arrangement of the first fixed optical attenuators 5 and 8 provided in the optical add / drop multiplexer 1 according to the embodiment of the present invention will be described in detail with reference to FIG. In the present embodiment, the first fixed optical attenuator 16 on the receiving side will be described. However, the second fixed attenuator 17 on the transmitting side has the same configuration, and the same arrangement configuration is applied. Is done.
[0041]
In the present embodiment, the first fixed optical attenuator 16 is composed of four sets, and a pair of left and right SC connectors connected to the optical multiplexer / demultiplexer 13 via each optical transmission line 14. Plugs 16A, 16B, an element body 16C for a fixed optical attenuator inserted between these SC connector plugs 16A, 16B, and this SC connector plug 16A, A JJ connector (adapter) 16D for mating the 16B concentrically.
[0042]
Among them, the JJ connector (adapter) 16D is provided with a flange 161 projecting laterally at the center, and this flange 161 is provided with a screw hole. That is, in the JJ connector (adapter) 16D, adjacent ones adjacent to each other are arranged so as to be shifted by the thickness (d) of the flange 161. Screws (small screws) 162 and the like are attached so as to penetrate the screw holes provided in the 161 integrally, and the adjacent JJ connectors (adapters) 16D are integrally fixed.
[0043]
By arranging in this manner, the adjacent ones of the SC connector plugs 16B can be secured at a fixed interval (D) in the arrangement (short) direction, and are shifted from each other by the distance L in the axial (long) direction. Therefore, when replacing the element body 16C for adjusting the attenuation, a space for inserting and removing the finger can be secured.
[0044]
Therefore, according to the present embodiment, as shown in FIG. 3, when four sets of fixed optical attenuators 16 are installed inside the housing 10, the JJ connector (adapter) 16D is shifted in the longitudinal direction by the distance d. In addition, by installing in a staggered (asymmetric) relationship, all plugs can be easily attached and detached manually without using a dedicated jig.
That is, by alternately arranging the JJ connectors (adapter) 16D in this manner, even if the JJ connector (adapter) 16D is adjacent to the compact minimum interval, a finger is placed between the JJ connector (adapter) 16D. The SC connector plug 16B can be grasped by being inserted, and can be removed and inserted.
[0045]
Next, the operation of the optical add / drop multiplexer 1 according to the present embodiment configured as described above will be described.
(I) When transmitting information from A to C:
In the optical add / drop multiplexer 1, each wavelength multiplexed signal light transmitted from the key broadcast station at the point A through the optical transmission line 2A is transmitted to the optical multiplexer / demultiplexer 13 provided in the local broadcast station at the point C. A maximum of four specific wavelength signal lights (λ_DROP) And transmitted to the optical receiving unit 3 provided in the local broadcasting station at the same point C via each optical transmission line 14.
[0046]
A first fixed optical attenuator 16 is provided in the middle of each optical transmission line 14 wired from the optical multiplexer / demultiplexer 13 to each optical receiving unit 3. The attenuator 16 causes each specific wavelength signal light (λ_DROP) Is attenuated so as to be within the light receiving level range of the optical receiving unit 3 and then input to each optical receiving unit 3.
[0047]
Thereby, the information transmitted from the key broadcasting station at the point A can be safely received at the broadcasting station at the point C, that is, when the signal light of each optical receiver 3 is received, the light intensity can be received at an allowable level. In addition, it is possible to prevent each optical receiving unit 3 from being damaged or damaged (burned out) by the signal light.
[0048]
(II) For information transmission from C to A:
On the other hand, the signal light (λ) having a specific wavelength corresponding to desired information to be transmitted from each optical transmitter 4 provided in the local broadcasting station at the point C to the key broadcasting station at the point A._ADD) Is transmitted from the optical transmission line 15 to the optical multiplexing / demultiplexing device 13 and is multiplexed with the wavelength multiplexed signal light transmitted from the optical transmission line 2B. The light is attenuated by the fixed optical attenuator 17 and the light intensity is adjusted to the same level as the wavelength multiplexed signal light.
[0049]
Thereby, the information transmitted from the broadcasting station at the point C can be transmitted through the optical transmission line 2A and can be safely received by the key broadcasting station at the point A. That is, a signal light of a specific wavelength (λ_ADD) Can be received at an allowable level of light intensity, so that the light receiving unit can transmit the signal light (λ_ADD) Can prevent breakage and damage (burnout).
[0050]
(III) When transmitting information from point C to point B:
When such information transmission is performed, in the communication wiring of the present embodiment as shown in FIG. 1, a direct connection from the point C to the point B is made due to the connection relationship between the optical transmission lines 2A and 2B and the optical transmission line 15. Cannot be transmitted to the A. once, so that the transmission path once relays the point A, that is, C.I. A. Information communication can be performed through the route B.
[0051]
In such a transmission route, a signal light (λ_ADD) Simply passes (PASS) the optical multiplexer / demultiplexer 13 at the point C, that is, is not split at each optical demultiplexer (optical demultiplexer). Therefore, the signal light (λ_ADD) Indicates the wavelength to be demultiplexed by each optical demultiplexer (optical demultiplexer), that is, the specific wavelength signal light (λ_DROP) Is used.
[0052]
Also, by using the same route, information transmission from the point B to the point C can be performed. A. Information communication can be performed through the route C.
[0053]
Various aspects of the optical add / drop multiplexer according to the present embodiment configured as described above will be described with reference to FIG.
(1) When changing to an optical branching device:
As shown in FIG. 2A, for example, when information communication is performed in one direction from the head office at point A to each of the branch offices at point B and point C (only for downlink), the branch office at point C is The first common port 11 and the second common port 12 of the optical multiplexer / demultiplexer 13 to be installed are limited to the input side and the output side of the wavelength multiplexed signal light, respectively.
On the other hand, the optical multiplexer / demultiplexer 13 installed at the branch office at the point C includes a first optical multiplexer / demultiplexer (optical demultiplexer) (not shown) provided at a plurality of locations in the middle of an optical transmission line 14 connected thereto. Although the fixed optical attenuator 16 is provided, the optical multiplexer (optical multiplexer) is not provided with the optical transmission line 15 and the second fixed optical attenuator 17.
[0054]
Further, as shown in FIG. 2A, at point C, the wavelength (of the specific wavelength signal light) is λ_DROP≠ λ_ADDIt is. This is because signal light of the same wavelength cannot be transmitted in the same transmission line due to light interference or the like. Therefore, when there is an insertion signal light from the optical transmission unit 4 at the point C, the wavelength of the insertion signal light cannot be used elsewhere. That is, this wavelength cannot be used for signal light transmitted from point A to point B or from point A to point C.
Thus, when a communication system dedicated to reception is constructed at the branch office at the point C with respect to the head office at the point A, since the wavelength is not restricted by the insertion signal light, more signal light can be received by that much. it can.
Therefore, by constructing in this manner, the optical multiplexer / demultiplexer 13 can be changed to an optical branching device, and can be effectively used especially when only one-way communication is required such as video distribution.
[0055]
(2) When changing to an optical insertion device:
Next, as shown in FIG. 7B, for example, when information communication is performed in one direction from each of the branch offices at the point B and the point C to the head office at the point A (only for uplink), the branch office at the point C is used. The first common port 11 and the second common port 12 of the optical multiplexing / demultiplexing device 13 are limited to the output side and the input side of the wavelength multiplexed signal light, respectively.
On the other hand, the optical multiplexer / demultiplexer 13 installed at the branch office at the point C has a second optical multiplexer / demultiplexer (optical multiplexer), which is connected to a plurality of optical multiplexer / demultiplexers (not shown). The optical multiplexer / demultiplexer (optical demultiplexer) is not provided with the optical transmission line 14 and the first fixed optical attenuator 16.
[0056]
Further, as shown in FIG. 2B, at point C, the wavelength (of the signal light of the specific wavelength) is λ_DROP≠ λ_ADD, Λ_n≠ λ_ADDIt is. As described above, this is because signal light having the same wavelength cannot be transmitted in the same transmission line due to light interference or the like. Therefore, when there is a branched signal light transmitted from the point A and transmitted at the point C, the wavelength of the branched signal light cannot be used elsewhere. That is, this wavelength cannot be used for signal light transmitted from point C to point A.
Thereby, when a transmission-only communication system is constructed at the branch offices at the point C and the point B with respect to the head office at the point A, since the wavelength is not restricted by the branched signal light, more signal light can be used accordingly. Can be sent. However, the wavelength of the signal light transmitted from the point C to the point A is not the same as the wavelength of the signal light transmitted from the point B to the point A.
Therefore, with this configuration, the optical demultiplexer / demultiplexer 13 can be changed to an optical insertion device, and can be effectively used particularly when only one-way communication such as video wiring is required.
[0057]
When A, B, and C do not have the hierarchical structure as described above but have a parallel relationship having no hierarchical relationship with each other, a configuration similar to that of the optical multiplexer / demultiplexer 13 according to the present embodiment is used. By using a plurality of sets and combining them appropriately, it is possible to realize a communication system which can be directly connected to each other and transmitted and received without passing through another point on the way.
[0058]
Further, by expanding the above-described network, it is possible to construct a star network (star network topology).
[0059]
【The invention's effect】
As described above, the optical branching device of the present invention allows the first and second common ports connected to the optical transmission line at a specific point and the transmission from any point including the two points via the optical transmission line. Passage for transmitting the signal light other than the specific wavelength signal light from the wavelength multiplexed signal light input to one of the first and second common ports to the other of the first and second common ports Means, and a branching means for selectively branching out a specific wavelength signal light from the wavelength multiplexed signal light transmitted in the optical transmission line, extracting the specific wavelength signal light, and outputting the extracted signal light to a light receiving unit, A selected fixed optical attenuator having a predetermined attenuating function is mounted between the branching means and the optical receiving unit so that the light intensity level of the light becomes a light receiving level allowed by the optical receiving unit.
[0060]
Therefore, according to the present invention, since a small and inexpensive fixed optical attenuator is used for the optical attenuator, the optical attenuator is suitable for an optical wavelength division multiplexing communication network, particularly a transmission system requiring a cost advantage, and is advantageous for miniaturization. It is possible to provide a simple optical branching device.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram showing an optical add / drop multiplexer according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a communication network (topology) constructed using the optical add / drop multiplexer according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram showing a structure of a fixed optical attenuator of the optical add / drop multiplexer according to the embodiment of the present invention.
FIGS. 4A and 4B are schematic diagrams showing various modes using the optical add / drop device shown in FIG. 1, wherein FIG. 4A is an optical add / drop device, and FIG.
FIG. 5 is a schematic configuration diagram showing a conventional optical add / drop device.
[Explanation of symbols]
1 Optical add / drop device
10 Housing
11,12
First and second common ports
13. Optical multiplexer / demultiplexer (passing means, multiplexing means, demultiplexing means)
14 Optical transmission path
15 Optical transmission line
16 First fixed optical attenuator (for optical transmitter)
16A, 16B
SC connector plug
Element body for 16C fixed optical attenuator
16D JJ connector (adapter)
161 flange
162 screw (small screw)
17 Second fixed optical attenuator (for optical receiver)
2A, 2B, 2C
Optical transmission path
3 Optical receiver
4 Optical transmitter
λ_ADD  Signal light of specific wavelength (for insertion)
λ_DROP  Specific wavelength signal light (for demultiplexing)

Claims (6)

A specific wavelength signal light of wavelength multiplexed signal light being transmitted in an optical transmission line provided between at least two different points is selectively branched from the wavelength multiplexed signal light at a specific point between the two points. An optical branching device for taking out and outputting to an optical receiving unit provided at the specific point,
First and second common ports connected to the optical transmission line at the specific point;
From the wavelength multiplexed signal light to be transmitted and transmitted through the optical transmission line from any point including the two points and input to one of the first and second common ports, the wavelength multiplexed signal light other than the specific wavelength signal light is used. Passing means for outputting a signal light to one of the first and second common ports;
Branching means for selectively branching out the specific wavelength signal light from the wavelength multiplexed signal light transmitted in the optical transmission line, extracting the specific wavelength signal light, and outputting the extracted signal light to the optical receiver,
A selected fixed optical attenuator having a predetermined attenuation function so that the light intensity level of the branched specific signal wavelength light becomes a light receiving level allowed in the optical receiving unit, the branching unit and the optical receiving unit An optical branching device, which is mounted between the optical branching device. 2. The optical branching device according to claim 1, wherein the fixed optical attenuator includes a plurality of fixed optical attenuators, and adjacent ones are arranged alternately and interchangeably. 3. For wavelength multiplexed signal light being transmitted in an optical transmission line provided between at least two different points, signal light having a specific wavelength different from the wavelength multiplexed signal light from an optical transmitter provided at a specific point between the two points. An optical insertion device for emitting the specific wavelength signal light and the wavelength multiplexed signal light,
First and second common ports connected to the optical transmission line at the specific point;
With multiplexing means for taking in the signal light of the specific wavelength output from the optical transmission unit provided at the specific point and multiplexing with the wavelength multiplexed signal light,
When the signal light of the specific wavelength is inserted into the optical transmission line through which the wavelength multiplexed signal light is transmitted and multiplexed with the wavelength multiplexed signal light, the light intensity level of the signal light of the specific wavelength is changed to the wavelength multiplexed signal light. An optical insertion device, wherein a fixed optical attenuator having a predetermined attenuating function so as to match the light intensity level of the optical transmitter is mounted between the multiplexing means and the optical transmitter. 4. The optical insertion device according to claim 3, wherein the fixed optical attenuator includes a plurality of fixed optical attenuators, and adjacent ones are arranged alternately and interchangeably. 5. A specific wavelength signal light of wavelength multiplexed signal light being transmitted in an optical transmission line provided between different points is selectively branched out from the wavelength multiplexed signal light at a specific point and provided at the specific point. A signal light having a specific wavelength different from the wavelength multiplexed signal light from the optical transmission unit provided at the specific point with respect to the wavelength multiplexed signal light being transmitted through the optical transmission path while being output to the optical receiving unit. An optical add-drop multiplexer that emits the specific wavelength signal light and combines the specific wavelength signal light with the wavelength multiplexed signal light,
First and second common ports respectively connected to the optical transmission line at the specific point;
The specific wavelength signal light is selected from the wavelength multiplexed signal light transmitted and transmitted through the optical transmission line from any one of the two points and input to at least one of the first and second common ports. Passing means for outputting the other signal light to the other of the first and second common ports;
Branching means for selectively branching out the specific wavelength signal light from the wavelength multiplexed signal light transmitted in the optical transmission line, extracting the specific wavelength signal light, and outputting the extracted signal light to the optical receiver;
Combining means for taking in the signal light of the specific wavelength output from the optical transmission unit and multiplexing with the wavelength multiplexed signal light transmitted in the optical transmission line,
A predetermined light output level of the specific signal wavelength light branched by the branching means from the wavelength multiplexed signal light transmitted in the optical transmission line is a predetermined light reception level allowed by the light receiving unit. A selected first fixed optical attenuator having an attenuating function is provided between the branching unit and the optical receiving unit, and
When the wavelength multiplexed signal light and the signal light of the specific wavelength output from the optical transmitter are multiplexed by the multiplexing means, the light intensity level of the signal light of the specific wavelength is light of the wavelength multiplexed signal light. An optical add / drop multiplexer, wherein a selected second fixed optical attenuator having a predetermined attenuation function that matches an intensity level is provided between the multiplexing unit and the optical transmission unit. At least the first fixed optical attenuator or the second fixed optical attenuator comprises a plurality of fixed optical attenuators, and the first fixed optical attenuators are adjacent to each other or the second fixed optical attenuators are adjacent to each other. 6. The optical add / drop multiplexer according to claim 5, wherein the devices are arranged alternately and interchangeably.

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