JP3577438B2 - Add-drop optical circuit module - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical component for demultiplexing and / or multiplexing a specific wavelength light from a multiplexed signal light having a plurality of wavelengths in a wavelength division multiplexing optical communication system. The present invention relates to a wavelength division multiplexing optical demultiplexer and / or a multiplexer in which two fiber collimators are arranged to face each other via a. This wavelength division multiplexing optical demultiplexer / multiplexer is particularly useful for realizing an add / drop function in wavelength units in a wavelength division multiplexing optical network.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a wavelength division multiplexing optical network, an optical communication system of an add / drop method for transmitting and receiving a large-capacity signal, such as a relay point in a large city, has been studied. In this method, a specific wavelength light is extracted (dropped) from a multiplexed signal light of a plurality of wavelengths transmitted by a trunk transmission line from a network node, and a signal from this node is transmitted on the specific wavelength light ( Add), a technique of returning the signal light of a plurality of wavelengths multiplexed to the transmission path again.
[0003]
A basic element for realizing the add / drop function in this add / drop type wavelength multiplexing optical network is a wavelength division multiplexer / demultiplexer. For example, a demultiplexing / multiplexing optical integrated circuit using an arrayed waveguide diffraction grating (AWG) or the like has been developed. Here, the multiplexed signal light of a plurality of wavelengths from the transmission line is branched and output to the output port of the arrayed waveguide diffraction grating for each wavelength, and the light of each wavelength is multiplexed to form an optical fiber or the like. Then, by returning to the input port, the data is sent to the transmission path again. However, the structure is complicated and the characteristics are not always sufficient.
[0004]
Recently, a configuration combining two 3-port optical circulators and a fiber grating has been proposed as an add / drop optical circuit of a network node having a fixed wavelength. An example is shown in FIG. Between the first port _{P 21} of the second port _{P 12} and the second optical circulator 12 of the first optical circulator 10 is connected by the fiber grating 14, enter the first port _{P 11} of the first optical circulator 10 port, a third port _{P 13} to the drop port, the second port _{P 22} the output port of the second optical circulator 12, a third port _{P 23} to the add port, a structure in which set respectively. The fiber grating 14 has a Bragg diffraction grating formed in the core of the fiber, and functions as a filter that reflects light of a specific wavelength.
[0005]
Here, for example fiber grating is that it is set to the property of reflecting only the light of wavelength lambda _4. When the wavelength-multiplexed signal light (wavelength: λ ₁ ,..., Λ ₅ ) is input from the first port P ₁₁ of the first optical circulator 10, it is output as it is from the second port P _12. Only the light of λ ₄ is reflected by the fiber grating 14, returns to the first optical circulator 10, and is extracted from the third port P _{13 as} drop light (wavelength: λ ₄ ). Light transmitted through the fiber grating 14 (wavelengths: λ ₁ ,..., Λ ₃ , λ ₅ ) is input from the first port P ₂₁ of the second optical circulator 12 and output from the second port P ₂₂ . The add light (wavelength: λ ₄ ) input from the third port P ₂₃ of the second optical circulator 12 is output from the first port P ₂₁ of the second optical circulator 12, but is reflected by the fiber grating 14, it also becomes possible to output from the second second port P ₂₂ of the optical circulator 12. Accordingly, the output light from the second of the second port P ₂₂ of the optical circulator 12, the input light and the same wavelength multiplexed signal light _{(wavelength: λ 1, ..., λ 5} ) becomes. Here, the first optical circulator 10 and the fiber grating 14 function as an optical demultiplexer, and the fiber grating 14 and the second optical circulator 12 function as an optical multiplexer.
[0006]
[Problems to be solved by the invention]
As described above, the configuration combining the two optical circulators and the fiber grating has a relatively simple structure, but can realize an add / drop function in a network node having a fixed wavelength, and can be connected to an optical fiber as a transmission path. There are advantages such as good consistency. However, there are disadvantages such as an increase in size due to the use of an optical circulator and an increase in cost.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical demultiplexer / multiplexer for wavelength division multiplexing which is small in size and low in cost and has good matching with an optical fiber as a transmission line. It is another object of the present invention to provide an optical demultiplexer / multiplexer for wavelength division multiplexing which can easily realize an add / drop function in a network node having a fixed wavelength while having a simple structure.
[0008]
[Means for Solving the Problems]
The present invention relates to a two-core ferrule having two parallel optical fibers, a first fiber collimator including a common first collimating lens for transmitting the two lights, and a single-core ferrule having one optical fiber And a second fiber collimator comprising a second collimating lens for transmitting the light, and a wavelength division multiplexing optical demultiplexer in which the first and second collimating lenses are opposed to each other via a wavelength selection filter. It is a multiplexer. The two optical fibers of the two-core ferrule are coupled by light reflected by the wavelength selection filter, and one optical fiber of the two-core ferrule and the optical fiber of the single core ferrule are coupled by light transmitted by the wavelength selection filter. The first and second fiber collimators and the wavelength selection filter are positioned. This wavelength division multiplexing optical demultiplexer / multiplexer has either a demultiplexing function or a multiplexing function depending on the use form.
[0009]
That is, when functioning as an optical demultiplexer, a specific wavelength light of the wavelength-division multiplexed light input from one optical fiber of the two-core ferrule is transmitted through the wavelength selection filter and output from the single-core ferrule optical fiber. At the same time, light of a wavelength other than the specific wavelength is reflected by the wavelength selection filter and output from the other optical fiber of the two-core ferrule. When functioning as an optical multiplexer, light of a specific wavelength input from an optical fiber of a single-core ferrule passes through a wavelength selection filter, and light of another wavelength excluding the specific wavelength input from the other optical fiber of a two-core ferrule. Are reflected by the wavelength selection filter and output from one optical fiber of the two-core ferrule.
[0010]
For example, a two-core ferrule has a structure in which one optical fiber is located on the center axis of the ferrule and the other optical fiber is eccentrically arranged from the center axis, and the wavelength selection filter is formed on a parallel plate transparent substrate. It has a structure in which a wavelength selection film is formed, and the wavelength selection film is installed to be inclined with respect to the center axis of the ferrule. Alternatively, the two-core ferrule has a structure in which two optical fibers are eccentrically positioned symmetrically with respect to the center axis of the ferrule, and the wavelength selection filter has a structure in which a wavelength selection film is formed on a wedge-shaped transparent substrate. And the wavelength selection film is disposed substantially perpendicular to the center axis of the ferrule.
[0011]
Further, the present invention provides a first fiber collimator including a first two-core ferrule having two parallel optical fibers and a common first collimating lens for transmitting the two lights, and two parallel lights. A second two-core ferrule having a fiber and a second fiber collimator including a common second collimator lens for transmitting the two lights are provided between the first and second collimator lenses via a wavelength selection filter. It is a wavelength division multiplexing optical demultiplexer / multiplexer arranged to face each other. The two optical fibers of the first two-core ferrule are coupled by the reflected light from the wavelength selection filter, and one of the first two-core ferrule and the other of the second two-core ferrule has a different wavelength. The first and second optical fibers of the first and second two-core ferrules are coupled by the transmitted light of the selective filter, and the other optical fiber of the first two-core ferrule is coupled by the transmitted light of the wavelength selective filter. A second fiber collimator and a wavelength selection filter are positioned. Although the wavelength division multiplexing optical demultiplexer / multiplexer has both the functions of demultiplexing and multiplexing, it can be configured to exhibit only one of the functions of demultiplexing and multiplexing depending on the use form.
[0012]
For example, each of the first and second two-core ferrules has a structure in which two optical fibers are positioned eccentrically and symmetrically with respect to the center axis of the ferrule, and the wavelength selection filter is a transparent parallel plate type. The structure is such that a wavelength selection film is formed on a substrate, and the wavelength selection film is installed substantially perpendicular to the center axis of the ferrule.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to realize an add / drop function of a network node having a fixed wavelength, a wavelength division multiplexing optical network is constructed by using two pairs of the above-described two-core ferrule-single-core ferrule type wavelength division multiplexing / demultiplexing multiplexer. There is a configuration for insertion into a transmission line. One wavelength division multiplexing / demultiplexing / multiplexing device is used as an optical demultiplexer to extract a specific wavelength light from the multiplexed signal light of multiple wavelengths from the transmission line, and the other wavelength division multiplexing / demultiplexing / multiplexing device is used as an optical demultiplexer. The add / drop optical circuit module is configured to add a specific wavelength light to the light excluding the specific wavelength and return the multiplexed signal light of a plurality of wavelengths to the transmission line.
[0014]
As another configuration for realizing the add / drop function of the network node having a fixed wavelength, one wavelength division multiplexer / demultiplexer of the above-described two-core ferrule / two-core ferrule type is provided by using a wavelength division multiplexing optical network. There is a configuration in which the transmission line is inserted into the transmission line. A multiplexed signal light of a plurality of wavelengths is supplied from a transmission line to one optical fiber of the first two-core ferrule, and a specific wavelength light is extracted from one optical fiber of the second two-core ferrule. The specific wavelength light is added to the other optical fiber of the two double-core ferrules, and the signal light of a plurality of wavelengths multiplexed from the other optical fiber of the first two-core ferrule is returned to the transmission line. Next, an add / drop optical circuit module is configured.
[0015]
【Example】
FIG. 1 is an explanatory view showing one embodiment of a wavelength division multiplexing optical demultiplexer / multiplexer according to the present invention. A first fiber collimator 26 including a two-core ferrule 22 having two parallel optical fibers 20a and 20b, a common first collimating lens 24 for transmitting the two lights, and one optical fiber 28 The first collimator lens 24 and the second collimator lens 32 are connected via a wavelength selection filter 36 to a single fiber ferrule 30 and a second fiber collimator 34 including a second collimator lens 32 for transmitting the light. Are arranged so as to face each other.
[0016]
As shown in the enlarged view, the two-core ferrule 22 has a structure in which one optical fiber 20a is located on the center axis of the ferrule and the other optical fiber 20b is eccentrically arranged from the center axis. The wavelength selection filter 36 is provided with a wavelength selection film 39 formed by alternately laminating a large number of dielectric materials having different refractive indexes with a predetermined film thickness on one surface of a parallel plate type transparent substrate 38 made of glass or the like. There is a method in which only light of a specific wavelength is transmitted by using light interference between multilayer films. The wavelength selection filter 36 has a wavelength selection film 39 facing the first collimator lens 24 and installed at an angle with respect to the central axis of the fiber. Of course, the wavelength selection film may be provided on the opposite surface.
[0017]
The two optical fibers 20a and 20b of the two-core ferrule 22 are coupled by reflected light from the wavelength selection filter 36, and one optical fiber 20a of the two-core ferrule 22 and the optical fiber 28 of the single-core ferrule 30 are connected to the wavelength selection filter. The first fiber collimator 26, the second fiber collimator 34, and the wavelength selection filter 36 are positioned so as to be coupled by the transmitted light 36. The two-core ferrule 22 and the single-core ferrule 30 are assembled such that their central axes are parallel. Both the demultiplexing and the multiplexing may have the same module configuration. Depending on the selection of the optical fiber for inputting light and the optical fiber for outputting light, either a demultiplexing function or a multiplexing function can be obtained.
[0018]
FIGS. 2A and 2B show an example of the demultiplexing and multiplexing operations. Here, the wavelength multiplexed light includes wavelengths λ ₁ ,..., Λ _n , and the wavelength selection filter 36 transmits only the light of the specific wavelength λ ₁ among the multiplexed wavelengths. In the case of optical demultiplexing, as shown in FIG. 2A, wavelength-division multiplexed lights λ ₁ ,..., Λ _n are input from one optical fiber 20 a of the two-core ferrule 22. Specific wavelength lambda ₁ of the light of which passes through the wavelength selection filter 36 to output from the optical fiber 28 of single-core ferrule 30. Other wavelengths lambda ₂ other than the specific wavelength λ _{1, ...,} light lambda _n is outputted from the other optical fiber 20b of being reflected by the wavelength selection filter 36 two-core ferrule 22. In the case of optical multiplexing, as shown in FIG. 2B, the specific wavelength light λ ₁ is input from the optical fiber 28 of the single core ferrule 30, and the wavelength λ ₂ , .., Λ _n light is input. The input specific wavelength light λ ₁ passes through the wavelength selection filter 36, and the light of wavelengths λ ₂ ,..., Λ _n input from the other optical fiber 20 b of the two-core ferrule 22 is reflected by the wavelength selection filter 36, 2 one of the wavelength-multiplexed optical lambda ₁ from an optical fiber 20a of the core ferrule 22, ..., and outputs a lambda _n.
[0019]
FIG. 3 shows an example of an optical circuit for realizing an add / drop function of a network node having a fixed wavelength using such an optical demultiplexer / multiplexer for wavelength multiplexing. The wavelength division multiplexing optical demultiplexer / multiplexer shown in FIG. 1 is inserted into the transmission line 42 of the wavelength division multiplexing optical network as two pairs. That is, one wavelength division multiplexing / demultiplexing / multiplexing device is an optical demultiplexer, and the other wavelength division multiplexing / demultiplexing / demultiplexing device is an optical multiplexer 44b. On the optical splitter 44a side, the transmission line 42 is connected using the first optical fiber 20a of the two-core ferrule 22 as an input port. The second optical fiber 20b on the side of the optical demultiplexer 44a is connected to the first optical fiber 20a on the side of the optical multiplexer 44b, and the second optical fiber 20b is connected to the transmission line 42 as an output port. The optical fiber 28 of the single core ferrule 30 on the side of the optical splitter 44a serves as a drop port, and the optical fiber 28 of the single core ferrule 30 on the side of the optical multiplexer 44b serves as an add port.
[0020]
The multiplexed signal light of a plurality of wavelengths (wavelengths: λ ₁ ,..., Λ _n ) transmitted by the transmission line 42 is input to the first optical fiber 20a (input port) of the two-core ferrule 22 on the optical demultiplexer 44a side. ), The specific wavelength light λ ₁ is extracted as drop light from the optical fiber 28 (drop port) of the single core ferrule 30. The light of a plurality of other wavelengths (λ ₂ ,..., Λ _n ) from which the specific wavelength λ ₁ has been removed is output from the second optical fiber 20b of the two-core ferrule 22 on the side of the optical demultiplexer 44a. The input is made from the first optical fiber 20a of the two-core ferrule 22 on the 44b side. The specific wavelength light lambda ₁ is added as an add optical from the optical fiber 28 of single-core ferrule 30 of the optical multiplexer 44b side (add port). As a result, the signal light (wavelengths: λ ₁ ,..., Λ _n ) is returned to the transmission line 42 from the second optical fiber 20 b of the two-core ferrule 22 on the optical multiplexer 44 b side. become.
[0021]
FIG. 4 is an explanatory view showing another embodiment of the wavelength division multiplexing optical multiplexer / demultiplexer according to the present invention. As in the embodiment shown in FIG. 1, a first fiber collimator 56 including a two-core ferrule 52 having two parallel optical fibers 50a and 50b and a common first collimating lens 54 for transmitting the two lights is provided. A second fiber collimator 64 including a single-core ferrule 60 having one optical fiber 58 and a second collimating lens 62 for transmitting the light, and a first collimating lens 54 and a second collimating lens 62; Are arranged so as to face each other via a wavelength selection filter 66.
[0022]
As shown in an enlarged view, the two-core ferrule 52 has a structure in which two optical fibers 50a and 50b are equidistant from the center axis of the ferrule and are eccentrically positioned 180 °. . The wavelength selection filter 66 has a structure in which a wavelength selection film 69 similar to that of FIG. 1 is provided on one surface of a transparent substrate 68 made of glass or the like and having a wedge-shaped cross section. Opposite to the ferrule 54, the ferrule is arranged substantially perpendicular to the center axis of the ferrule. Therefore, the opposite surface (the surface facing the second collimating lens 62) is inclined with respect to the center axis of the ferrule. This inclination angle is set to an angle at which the light incident on the second collimating lens 62 becomes parallel to the center axis of the ferrule. As a result, the central axes of the two-core ferrule 52 and the single-core ferrule 60 become parallel, so that assembly is facilitated.
[0023]
In this embodiment, as in the embodiment shown in FIG. 1, two optical fibers 50a and 50b of a two-core ferrule 52 are coupled by light reflected by a wavelength selection filter 66, and one optical fiber 50a of a two-core ferrule 52 is simply connected. The first fiber collimator 56, the second fiber collimator 64, and the wavelength selection filter 66 are positioned so that the optical fiber 58 of the core ferrule 60 is coupled by the light transmitted through the wavelength selection filter 66. Both the demultiplexing and the multiplexing may have the same module configuration. Depending on the selection of the optical fiber for inputting light and the optical fiber for outputting light, either a demultiplexing function or a multiplexing function can be obtained.
[0024]
FIG. 5 is an explanatory view showing still another embodiment of the wavelength division multiplexing optical multiplexer / demultiplexer according to the present invention. A first fiber collimator 76 including a first two-core ferrule 72 having two parallel optical fibers 70a and 70b and a common first collimating lens 74 for transmitting the two light beams; A second fiber collimator 84 including a second two-core ferrule 80 having optical fibers 78a and 78b and a common second collimating lens 82 for transmitting the two lights is connected to a first collimating lens 74 and a second collimating lens. Are arranged so as to face each other via a wavelength selection filter 86.
[0025]
As shown in an enlarged view, the first two-core ferrule 72 has the two optical fibers 70a and 70b separated by the same distance from the center axis of the ferrule and symmetrically biased by 180 °, as in the case of FIG. It is a structure that is located in mind. Similarly, the second two-core ferrule 80 also has a structure in which the two optical fibers 78a and 78b are equidistant from the center axis of the ferrule and 180 ° symmetrically eccentric. As in the case of FIG. 1, the wavelength selection filter 86 is a wavelength selection film 89 formed by alternately laminating a large number of dielectric materials having different refractive indexes with a predetermined thickness on one surface of a parallel plate type transparent substrate 88 made of glass or the like. This is a method in which only light of a specific wavelength is transmitted by utilizing light interference between multilayer films. This wavelength selection filter 86 is installed substantially perpendicular to the center axis of the ferrule.
[0026]
The two optical fibers 70a and 70b of the first two-core ferrule 72 are coupled by light reflected by the wavelength selection filter 86, and the first optical fiber 70a of the first two-core ferrule 72 and the second two-core ferrule 72 are combined. 80, the first optical fiber 78a is coupled by the transmitted light of the wavelength selection filter 86, and the second optical fiber 78b of the second two-core ferrule 80 and the second optical fiber of the first two-core ferrule 72 The first fiber collimator 76, the second fiber collimator 84, and the wavelength selection filter 86 are positioned so that 70b is coupled by the transmitted light of the wavelength selection filter 86, thereby providing a multiplexing and demultiplexing function.
[0027]
FIG. 6 shows an example of an optical circuit for realizing an add / drop function of a network node having a fixed wavelength using this wavelength division multiplexing optical demultiplexer / multiplexer. One wavelength division multiplexing optical multiplexer / demultiplexer 90 as shown in FIG. 5 is inserted into the transmission line 42 of the wavelength division multiplexing optical network. That is, the transmission line 92 is connected with the first optical fiber 70a of the first two-core ferrule 72 as an input port, and connected to the transmission line 92 with the second optical fiber 70b as an output port. The first optical fiber 78a of the second two-core ferrule 80 serves as a drop port, and the second optical fiber 78b serves as an add port.
[0028]
Here, the multiplexed signal light of a plurality of wavelengths from the transmission path includes wavelengths λ ₁ ,..., Λ _n , and the wavelength selection filter 86 transmits only the light of the specific wavelength λ ₁ among the multiplexed wavelengths. Shall be allowed. The signal light of a plurality of wavelengths (wavelengths: λ ₁ ,..., Λ _n ) transmitted by the transmission line 92 is input from the first optical fiber 70a (input port) of the first two-core ferrule 72. The specific wavelength light λ ₁ is extracted as drop light from the first optical fiber 78 a (drop port) of the second two-core ferrule 80. The light of a plurality of other wavelengths (λ ₂ ,..., Λ _n ) from which the specific wavelength λ ₁ has been removed is output from the second optical fiber 70b of the first two-core ferrule 72. Further, the specific wavelength light λ ₁ is added as add light from the second optical fiber 78b (add port) of the second two-core ferrule 80. As a result, from the second optical fiber 70b (output port) of the first two-core ferrule 72, the multiplexed signal light of a plurality of wavelengths (wavelengths: λ ₁ ,..., Λ _n ) is transmitted to the transmission line. Will be returned. Thus, the add / drop function can be realized by a single optical demultiplexer / multiplexer.
[0029]
【The invention's effect】
As described above, the present invention comprises a combination of a ferrule, a collimating lens, and a wavelength selection filter, so that it can be made compact and inexpensive, and has good matching with an optical fiber constituting a transmission line. An optical demultiplexer / multiplexer is obtained. In particular, in a configuration in which a two-core ferrule is arranged on both sides of a wavelength selection filter, a single device provides a demultiplexing and multiplexing function, so that an effect of easily realizing an add / drop function of a network node having a fixed wavelength is achieved. There is.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing one embodiment of a wavelength division multiplexing optical demultiplexer / multiplexer according to the present invention.
FIG. 2 is an explanatory diagram of the operation of the demultiplexing and multiplexing.
FIG. 3 is an explanatory diagram of an add / drop circuit to which the wavelength division multiplexer / demultiplexer is applied.
FIG. 4 is an explanatory view showing another embodiment of the optical multiplexer / demultiplexer for wavelength multiplexing according to the present invention.
FIG. 5 is an explanatory view showing still another embodiment of the wavelength division multiplexing optical multiplexer / demultiplexer according to the present invention.
FIG. 6 is an explanatory diagram of an add / drop circuit to which the optical multiplexer / demultiplexer for wavelength multiplexing is applied.
FIG. 7 is an explanatory diagram of an add / drop circuit according to a conventional technique.
[Explanation of symbols]
20a, 20b Optical fiber 22 Two-core ferrule 24 First collimator lens 26 First fiber collimator 28 Optical fiber 30 Single-core ferrule 32 Second collimator lens 34 Second fiber collimator 36 Wavelength selection filter

Claims (2)

A first fiber collimator comprising a first two-core ferrule having two parallel optical fibers and a common first collimating lens for transmitting the two lights, and a second fiber having two parallel optical fibers . And a second fiber collimator comprising a common second collimating lens for transmitting the two lights so that the first and second collimating lenses face each other via a wavelength selection filter. No arrangement structure, two optical fibers of the first two-core ferrule bonded by the light reflected by the wavelength selection filter, one of one of the optical fibers of the first two-core ferrule and the second two-wire ferrule of the optical fiber is connected by transmitted light through the wavelength selective filter, and the other optical fiber of the other optical fiber of the second two-wire ferrule and the first two-core ferrule DOO is the first and wavelength division multiplexing optical demultiplexer-multiplexer which exhibits demultiplexing and multiplexing function in the second Rukoto fiber collimator and the wavelength selection filter is positioned to couple with transmitted light through the wavelength selective filter The wavelength division multiplexing / demultiplexing device is inserted into a transmission line of a wavelength division multiplexing optical network to supply multiplexed signal light of a plurality of wavelengths from the transmission line to one optical fiber of the first two-core ferrule. Then, a specific wavelength light is extracted from one optical fiber of the second two-core ferrule, and the specific wavelength light is added to the other optical fiber of the second two-core ferrule. An add / drop optical circuit module configured to return to the transmission path as signal light of a plurality of wavelengths multiplexed from the optical fiber. Each of the first and second two-core ferrules has a structure in which two optical fibers are positioned eccentrically symmetrically with respect to the center axis of the ferrule, and the wavelength selection filter is a parallel plate type transparent substrate. to have a structure in which to form a wavelength selective film, the wavelength selection film add-drop optical according to claim 1, wherein the use of the optical demultiplexer for wavelength multiplexed which is installed substantially perpendicular to the ferrule central axis Circuit module.

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