JP2001330865A - Wavelength variable type optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength variable type optical filter which selects two or more wavelength components in an arbitrary combination. SOLUTION: This optical filter is constituted of an optical circulator 11 having an input end to which a wavelength multiplexed optical signal in which plural optical signals having different wavelengths are multiplexed is inputted, an output end from which an optical signal having a specific wavelength in the wavelength multiplexed optical signals is outputted and an input-output end for emitting the wavelength multiplex optical signal and for making the optical signal having the specific wavelength enter, a (1×N) optical switch 12 selecting one optical path among respective optical paths connecting a single input-output end to be connected to the input and output ends and N pieces of output ends, N pieces of optical gratings 13 whose one ends are connected respectively to N pieces of output ends of the optical switch 12 and which reflect respectively different specific wavelength components and an (N×1) optical switch 15 selecting one optical path among respective optical paths connecting the N pieces of input ends which are connected respectively to the N pieces of output ends of the N pieces of the gratings and a single output end outputting the wavelength multiplexed optical signal except for the arbitrary specific wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable optical filter, and more particularly to a wavelength tunable optical filter capable of selecting any combination of two or more wavelength components from a wavelength multiplexed optical input signal. About.

[0002]

2. Description of the Related Art An example of an optical filter for selecting one or two specific wavelength components from a wavelength multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths is disclosed in Japanese Patent Laid-Open No. 3-263003.
No. 6,086,045. FIG. 5 is a block diagram showing the configuration of the above-described conventional optical filter. In the figure, a 3 dB optical fiber coupler 3 for splitting incident light into two
Are optically connected to the optical input unit 1 and the optical output unit 7 via fiber-type optical isolators 2 and 6, respectively. Fiber optical isolator 2,6 passing light only in one direction, respectively, the optical signal P ₁ goes from the light input section 1 to the port _31, also to pass light signal P ₇ directed from port 33 to the optical output 7 Has become. Further, of the two ports 32 and 34 at the subsequent stage of the 3 dB optical fiber coupler, the port 32 is optically connected to the fiber Bragg reflector 4, and the port 34 is optically connected to the light detector 5. Further, the optical input unit 1 and the optical output unit 5 are each optically connected to an optical data link (not shown) using a wavelength multiplexed optical signal.

The operation of a conventional optical filter will be described with reference to the drawings. Optical data link to optical input unit 1
Is input to the port 31 of the 3 dB optical fiber coupler 3 through the fiber type optical isolator 2. Optical signal P ₂ directed from the optical signal P ₁ and the fiber-type optical isolator 2 directed from the light input section 1 to the port 31 to port 31, a plurality of different wavelengths λ1, λ2, ..., λk,
.., Λp are multiplexed optical signals. Port 3
The optical signal P ₂ incident on the optical fiber ₁ is a 3 dB optical fiber coupler 3
Optical signal P from the ports 32 and 34 toward the fiber Bragg reflector 4 and the photodetector 5.
_3, the optical signal _{P 4} is emitted, respectively. These optical signals P ₃ and P ₄ have multiplexed wavelengths λ 1, λ ₂ , exactly the same as the optical signals P ₁ and P ₂ except that the amplitude is reduced by half.
.., Λp. Optical signal P ₄ of this is output to the optical data link as it via the optical output unit 5.

On the other hand, a desired wavelength of the optical signal P ₃ is selected by the fiber type Bragg reflector 4. That is,
If the refractive index n of the optical waveguide of the fiber type Bragg reflector 4 and the pitch Λ of the diffraction grating are set to an equivalent refractive index nk and an optical pitch Λk under a certain control, the reflection wavelength λk = only an optical signal component of 2nk · .lamda.k is returned toward the fiber Bragg reflector 4 as an optical signal P ₅ to the port 32. The returned desired optical signal P ₅ of wavelength λk were, is branched into two by the 3dB optical fiber coupler 3 again, the optical signal P _6, the optical signal P ₇
Are emitted from the ports 31 and 33 toward the fiber type optical isolators 2 and 6, respectively. These optical signals P
_{6, P 7} consists of only wavelength λk.

Since the optical signal P ₆ is blocked by the fiber optical isolator 2, the optical signal of any wavelength is sent back to the data link without going from the fiber optical isolator 2 to the optical input unit 1. Never. On the other hand, the optical signal P ₇ is
The light is output from the light output unit 7 through the optical path. Optical signal P ₉ consists of only a desired wavelength .lamda.k. Thus, the wavelengths λ1, λ2,
..., .lamda.k, ..., if λp optical signal P ₁ which is multiplexed is inputted from the optical data link to an optical input section 1, on the one hand, the optical signal P ₁ and is completely the same wavelength-multiplexed optical signal By returning P ₄ from the optical output unit 5 back to the optical data link, all wavelength components of the optical signal in the optical data link can be retained, and a desired Bragg reflector arbitrarily selected by the fiber Bragg reflector 4 can be used. it is possible to output an optical signal P ₉ consisting of only the wavelength λk from the optical output unit 7.

[0006]

However, this prior art has the following problems. By using the 3 dB optical fiber coupler, the loss of the selected wavelength component λk is large (6 dB or more). Further, the above-described optical filter has a disadvantage that only two wavelength components can be selected at the maximum.

The present invention has been made in view of the above circumstances, and provides a tunable optical filter that selects two or more wavelength components in an arbitrary combination from wavelength-multiplexed optical input signals. It is intended to be.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a method in which a wavelength multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths is inputted. A wavelength tunable optical filter that outputs only light of a specific wavelength, an input end to which the wavelength multiplexed optical signal is input, an output end that outputs an optical signal of a specific wavelength of the wavelength multiplexed optical signal, and the wavelength An optical circulator having an input / output end for emitting a multiplexed optical signal and receiving the optical signal of the specific wavelength; a single input / output end connected to the input / output end of the optical circulator; (Integer) one of the optical paths connecting the output terminals to select one (1 × N) optical switch, and one end is connected to each of the N output terminals of the (1 × N) optical switch, N light beams that respectively reflect different specific wavelength components My bug rating and N
And a non-reflection terminator connected to the other ends of the optical fiber gratings.

According to a second aspect of the present invention, there is provided the tunable optical filter according to the first aspect, wherein the N optical fiber gratings include a plurality of optical fiber gratings respectively reflecting different specific wavelength components in series. It is characterized by being combined.

According to a third aspect of the present invention, when a wavelength multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, a desired specific wavelength light is output, and the desired specific wavelength is output. A wavelength tunable optical filter that also outputs a wavelength multiplexed optical signal excluding wavelength light, comprising: an input end to which the wavelength multiplexed optical signal is input; and an output that outputs an optical signal of a specific wavelength in the wavelength multiplexed optical signal. End, and an optical circulator having an input / output end for emitting the wavelength multiplexed optical signal and receiving the optical signal of the specific wavelength, and a single input / output end connected to the input / output end of the optical circulator. One (1 × N) optical switch for selecting one of the respective optical paths connecting N (integer of 2 or more) output terminals, and one end connected to the N output terminals of the (1 × N) optical switch Are connected to each other, Each of the N optical fiber gratings, the N input terminals respectively connected to the N output terminals of the N optical fiber gratings, and the wavelength multiplexed optical signal excluding the above-mentioned arbitrary specific wavelength are formed. And (N × 1) optical switches for selecting one of the respective optical paths connecting to a single output terminal for outputting.

According to a fourth aspect of the present invention, there is provided the tunable optical filter according to the third aspect, wherein the (1 × N) optical switch and the (N × 1) optical switch select an optical path.
It is characterized in that synchronous control is performed so as to be performed simultaneously on the same optical fiber grating among the N optical fiber gratings. The invention according to claim 5 relates to the tunable optical filter according to claim 3 or 4, wherein the N optical fiber gratings combine a plurality of optical fiber gratings respectively reflecting different specific wavelength components in series. It is characterized by becoming.

Further, the invention according to claim 6 is the invention according to claim 1.
According to the tunable optical filter according to any one of (1) to (5), selection of an optical path in the (1 × N) optical switch and the (N × 1) optical switch is performed by an external electric control signal. It is characterized by being controlled.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment will be described. The description uses the embodiment.
And specifically. First Embodiment FIG. 1 shows a tunable optical fiber according to a first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a filter. In FIG.
The optical circulator 11 has a plurality of different wavelengths (λ1, λ
2, ..., λN) wavelength multiplexed optical signal
Input port P₁And any fiber grating
Group 13 (FG₁, FG₂,…, FG_N) From the desired specific wave
Output port P that outputs long reflected light₂And (1 × N)
Input / output port P optically connected to switch 12₃Have
You. The (1 × N) optical switch 12 is an optical circulator
11 input / output ports P₃Single input / output port connected to
To P₄And N (an integer of 2 or more) output ports (O₁, O _Two,
…, O_N) And one of the optical paths connecting
It can be arbitrarily selected by an electric control signal. here
The selection of the optical path by the (1 × N) optical switch is
To output reflected light of a specific wavelength,
It depends on whether you need to select a rating. Different
N optical fibers each reflecting a specific wavelength component
Grating 13 (FG₁, FG₂,…, FG_N)
At one end is selected by an external electric control signal (1 × N)
Any output port (O₁, O_Two,…,
O_N) Is optically connected and the other end is a non-reflection terminator 1
4 are connected.

The filter operation of the first embodiment will be described with reference to the drawings. The wavelength-multiplexed optical signal is input to the port P ₁ of the optical circulator 11, output from the port P ₃ , and input to the input port P _{4 of} the (1 × N) optical switch 12. The optical signal incident on the input port 4 of the (1 × N) optical switch 12 passes through an optical path selected by an external electronic control signal, and is connected to an output port connected thereto.
_{(O 1, O 2, ...} , O N) are emitted to either. (1 ×
N) Selected output ports (O ₁ , O ₂ ,
, O _N ) are output to the optical fiber grating 13 (FG ₁ , FG) connected thereto.
₂ ,..., FG _N ).

The optical fiber grating 13 (FG)₁, F
G₂,…, FG_NWavelength multiplexed optical signal
The signal has a narrow wavelength width component centered on a specific reflection wavelength.
Optical fiber grating (FG₁, FG₂,
…, FG_N), Only the desired wavelength component
Is reflected. The desired wavelength component reflected is (1 × N) light
The selected port (O₁, O_Two,…,
O_N), Selected optical path, port P₄And light circular
Port P of data 11₃Returned via port P ₂
Output from Selected fiber grating
Optical signal light of other wavelengths that are incident together are not reflected
At the other end of the reflectionless terminator 14 at the other end.
End processed. Thus, according to the first embodiment, (1
× N) Switch the optical switch to extract different specific wavelength components.
In each of the N optical fiber gratings that reflect
Select an optical fiber grating that reflects the desired wavelength.
Select the desired wavelength component
Can be selected and output.

Second Embodiment FIG. 2 shows a tunable optical fiber according to a second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a filter. In the second embodiment,
Each of the wavelength tunable optical filters of the first embodiment has the same structure.
My Bug Rating 13 (FG₁, FG₂,…, FG_N)
(N × 1) light instead of the non-reflection terminator 14 connected to
Each of the selected input ports (I₁, I_Two,
…, I_N). (1 × N) Optical switch 1
2 selected optical path output ports (O₁, O_Two,…,
O_N) And (N × 1) input of the selected optical path of the optical switch 15.
Power port (I₁, I_Two, ..., I _N) Is always the same fiber
Connect an external power supply to the input / output end of the grating.
It is controlled in synchronization with the air control signal.

In FIG. 2, N optical fiber gratings 13 (F
G _{1, FG} 2, ..., any input port (I _1, I ₂ than an external electrical control signal to one end of the _{FG N), ..., I N} ) can be selected (N × 1) optical switch 15 is connected is, any output port from the outside of the electrical control signals to the other end of each of the optical fiber grating _{(O 1, O 2, ...} , O N) can be selected (1 × N) optical switch 12 is connected . Similarly to the first embodiment, the optical circulator 11 is optically connected to the input port P ₄ of the (1 × N) optical switch 12. The optical circulator 11 has an input port P ₁ for receiving an input optical signal are wavelength-multiplexed, the output port P _2,
With the input and output ports _{P 3.}

The filter operation of the second embodiment will be described with reference to the drawings. The wavelength-multiplexed optical signal is input to the port P ₁ of the optical circulator 11, output from the port P ₃ , and input to the input port P _{4 of} the (1 × N) optical switch 12. The optical signal incident on the input port 4 of the (1 × N) optical switch 12 passes through an optical path selected by an external electronic control signal, and is connected to an output port connected thereto.
_{(O 1, O 2, ...} , O N) are emitted to either. (1 ×
N) Selected output ports (O ₁ , O ₂ ,
, O _N ) are output to the optical fiber grating 13 (FG ₁ , FG) connected thereto.
_2, ..., is incident on the input end of the FG _N).

Optical fiber gratings (FG ₁ , F
G _2, ..., wavelength-multiplexed optical signal incident on FG _N) is an optical fiber grating for reflecting the components of narrow wavelength width centered on a specific reflection wavelength _{(FG 1, FG 2, ...} , the FG _N) Either one reflects only the desired wavelength component.
The desired wavelength component that has been reflected is the (1 × N) optical switch 12.
Of the selected port _{(O 1, O 2, ...} , O N), selected optical path, the port P ₄ and the port P of the optical circulator 1
₃ through, is output from the port _{P 2.}

The optical signal light of another wavelength that has been incident on the optical fiber grating is transmitted as it is without being reflected, and is input to the input port (I ₁ , I ₁ ) of the (N × 1) optical switch 15 at the other end.
I _2, ..., are input to the I _N), is output from the port P ₅ via the selected optical path. As described above, the (1 × N) optical switch and the (N × 1) optical switch are synchronously switched, and an optical fiber that reflects a desired wavelength from among N optical fiber gratings that respectively reflect different specific wavelength components. By selecting the grating, it is possible to arbitrarily select and separately output the desired specific wavelength component and the optical signal light of another wavelength excluding the component.

According to the configuration of the second embodiment, by controlling the (1 × N) optical switch 12, an arbitrary one wavelength component is selected from the wavelength-multiplexed optical signal and the port of the optical circulator 11 is selected. it is possible to output from the P _2, also directly holds a low loss for the other optical signal light wavelengths except any one wavelength component, (N × 1) that through the optical switch 15 to the output port P ₅ Can be.

Third Embodiment FIG. 3 is a block diagram showing a configuration of a wavelength variable optical filter according to a third embodiment of the present invention. In the third embodiment,
In the configuration of the wavelength variable optical filter of the first embodiment, (1)
× N) Each output port (O ₁ , O ₂ ,..., O) of the optical switch 12
_N ) instead of the N optical fiber gratings 13 reflecting one specific wavelength, an N optical fiber grating array 16 connected in series by arbitrarily combining a plurality of optical fiber gratings reflecting different specific wavelengths. Is used.

The N optical fiber gratings of this embodiment
Row 16 is, for example, the first optical fiber grating.
Row FG₁Are k optical fiber gratings (F
G₁₁, FG₁₂, ..., ..., FG_1k) In series, the second
Optical fiber grating array FG ₂Is k optical fibers
Grating (FG_{twenty one}, FG_{twenty two}, ..., ..., FG_2k)
Consists of a row connection and the Nth optical fiber
FG_NIs k optical fiber gratings
(FG_N1, FG_N2, ..., ..., FG_Nk)
Become. The optical fiber gratings that make up each row
The reflected wavelengths must all be different.
It is not necessary, and the number does not need to be the same
Needless to say. Regarding another configuration of the third embodiment,
Since the configuration is the same as that of the first embodiment described above, the description thereof will be omitted.
Omitted.

The filter operation of the third embodiment will be described with reference to the drawings. Port P _{1 of} optical circulator 11
The wavelength-multiplexed optical signal input to port P ₃
The input port P _{4 of} the (1 × N) optical switch 12 is connected to an output port via an optical path selected by an external electronic control signal.
_{(O 1, O 2, ...} , O N) are emitted to either. (1 ×
N) Selected output ports (O ₁ , O ₂ ,
, O _N ) are output from the optical fiber grating array 16 (FG ₁ , F
G ₂ ,..., FG _N ).

The optical fiber grating array 16 (FG₁,
FG₂,…, FG_NWavelength-multiplexed light incident on one of
The signal has a narrow wavelength band centered on different specific reflection wavelengths
Optical fiber grating (FG
I₁, FGI_Two,..., FGIK).
Only wavelength components are reflected. Desired reflected wavelength component
Is the selected port (O) of the (1 × N) optical switch 12.₁,
O_Two…, O_N), Selected optical path, port P₄And light
Port P of the calculator 11₃Via port P ₂Or
Output from For selected fiber grating
Optical signal light of other wavelengths that are incident together are not reflected
Transmitted as it is, and terminated at non-reflective terminator 14 at the other end
It is processed.

According to the configuration of the third embodiment, the port P of the optical circulator 11 is selected by selecting two or more wavelength components in an arbitrary combination from the wavelength-multiplexed optical signal.
₂ can be output.

Fourth Embodiment FIG. 4 is a block diagram showing the configuration of a wavelength variable optical filter according to a fourth embodiment of the present invention. In the fourth embodiment,
In the configuration of the tunable optical filter of the third embodiment, the output ends (FG ₁ , FG ₂ , FG ₂ , FG ₂ , FG ₂ ) of each fiber grating array in which a plurality of optical fiber gratings reflecting a plurality of specific wavelengths are connected in any combination and connected in series. .., FG _N ) instead of the non-reflection terminator,
Are connected to the selected input ports (I ₁ , I ₂ ,..., I _N ). The other configuration of the fourth embodiment is the same as that of the above-described second and third embodiments, and thus the description thereof is omitted.

According to the structure of the fourth embodiment,
It is possible to obtain substantially the same operation and effect as the filter of the above-described embodiment. The (1 × N) optical switch 12 and the (N × 1) optical switch 15 are synchronously switched, and a desired plurality of N optical fiber grating arrays 16 reflecting respective combinations of a plurality of different specific wavelength components are selected. By selecting an array of optical fiber gratings that reflect wavelengths, it is possible to arbitrarily select and separately output a desired combination of a plurality of specific wavelength components and optical signal light of other wavelengths excluding those components. it can.

[0029] According to the fourth embodiment, two or more wavelength components from the wavelength-multiplexed optical signals that it be selected in any combination, output from the port P ₂ of the optical circulator 11 In addition to this, it is possible to hold the unselected wavelength-multiplexed optical signal as it is with low loss and output it to the output port 5 of the (N × 1) optical switch 15.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. Is also included in the present invention.

[0031]

As described above, according to the tunable optical filter of the present invention, in an optical filter combining an optical circulator and an optical fiber grating, an optical circulator and a plurality of optical fiber gratings are used. By inserting an optical switch into the optical filter, there is an effect that a low-loss wavelength-variable optical filter that can select two or more wavelength components in an arbitrary combination from wavelength-multiplexed optical input signals can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a wavelength variable optical filter according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a wavelength variable optical filter according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a tunable optical filter according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a wavelength variable optical filter according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an optical filter according to a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical input unit 2 fiber type optical isolator 3 3 dB optical fiber coupler 31 to 34 port 4 fiber type black reflector 5 optical output unit 6 fiber type optical isolator 7 optical output unit 11 optical circulator 12 (1 × N) optical switch 13 light Fiber grating 14 Non-reflection terminator 15 (N × 1) optical switch 16 Optical fiber grating array

Claims (6)

[Claims] 1. A wavelength tunable optical filter that outputs only a desired specific wavelength light when a wavelength multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths is provided. An input end for inputting an optical signal, an output end for outputting an optical signal of a specific wavelength of the wavelength multiplexed optical signal, and an input / output end for emitting the wavelength multiplexed optical signal and for inputting the optical signal of the specific wavelength An optical circulator having: and one of the optical paths connecting a single input / output terminal connected to the input / output terminal of the optical circulator and N (an integer of 2 or more) output terminals. One end is connected to each of the (1 × N) optical switch and N output terminals of the (1 × N) optical switch, and each of the N outputs reflects a different specific wavelength component.
A wavelength tunable optical filter comprising: a plurality of optical fiber gratings; and a non-reflection terminator connected to the other ends of the N optical fiber gratings. 2. The tunable optical filter according to claim 1, wherein the N optical fiber gratings are formed by serially combining a plurality of optical fiber gratings respectively reflecting different specific wavelength components. 3. When a wavelength multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, a wavelength-multiplexed optical signal that outputs a desired specific wavelength light and excludes the desired specific wavelength light is provided. A wavelength tunable optical filter that also outputs: an input end to which the wavelength multiplexed optical signal is input, an output end to output an optical signal of a specific wavelength of the wavelength multiplexed optical signal, and the wavelength multiplexed optical signal. And an optical circulator having an input / output end for emitting the optical signal of the specific wavelength, and a single input / output end connected to the input / output end of the optical circulator, and N (an integer of 2 or more) (1 × N) optical switch for selecting one of the respective optical paths connecting to the output end of the optical switch, and one end respectively connected to the N output ends of the (1 × N) optical switch, and different specific wavelengths N that reflects each component
Optical fiber gratings, N input terminals respectively connected to N output terminals of the N optical fiber gratings, and a single unit for outputting a wavelength-division multiplexed optical signal excluding any arbitrary wavelength. A wavelength tunable optical filter comprising: an (N × 1) optical switch for selecting one of the respective optical paths connected to the output terminal. 4. The (1 × N) optical switch and the (N)
4. The wavelength tunable type according to claim 3, wherein the selection of the optical path in the optical switch is synchronously controlled so that the same optical fiber grating among the N optical fiber gratings is simultaneously selected. Light filter. 5. The wavelength tunable light according to claim 3, wherein the N optical fiber gratings are formed by serially combining a plurality of optical fiber gratings respectively reflecting different specific wavelength components. filter. 6. The (1 × N) optical switch, the (N × 1)
6. The tunable optical filter according to claim 1, wherein selection of an optical path in the optical switch is performed by controlling the optical path with an external electric control signal.