JP2003140212A - Device and method for signal light demultiplexing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new light demultiplexing device which has an improved S/N without being influenced by signal light having an approximate wavelength. SOLUTION: The signal light demultiplexing device 10 which selects and demultiplexes signal light of a specified wavelength from among wavelength- division multiplex signal lights is equipped with signal light demultiplexing elements 13a to 13h which input the wavelength-division multiplex signal light, perform wavelength conversion of only signal light of a specific wavelength among the inputted wavelength-division multiplex signal lights by using a peudo phase matching system, and output wavelength-converted signal light as demultiplexed signal light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal light separating apparatus and a signal light separating method for selecting and separating signal light of a predetermined wavelength from wavelength division multiplexed signal light (hereinafter referred to as "WDM signal light").

[0002]

2. Description of the Related Art In recent years, in order to increase the information density of WDM signal light, it has been considered to shorten the wavelength interval from 100 GHz (about 0.8 nm) to 50 GHz (about 0.4 nm). Along with this, it has become necessary to separate and extract only the signal light of a predetermined wavelength from the signal light of which the wavelengths are very close.

The following are examples of conventional signal light separating devices.

First, a dielectric multilayer filter is inserted between the optical waveguides or between the optical fibers so that only the signal light of the filter center wavelength is taken out. For example,
As shown in FIG. 3, when the signal lights of λ1 to λ3 are input from the first port 41, the signal light of λ2 passes through the dielectric multilayer filter 44 and the third port 43 of the signal light demultiplexer 40. While being output, the signal lights of λ1 and λ3 are reflected by the dielectric multilayer filter 44 and output from the second port 42. Thus, the one using the dielectric multilayer filter is low in productivity because it is necessary to form a dielectric multilayer structure of 200 layers or more in the case of 50 GHz, and the manufacturing accuracy is very high. There is a drawback that the yield is poor because it is severe.

Secondly, the signal light of each wavelength is demultiplexed for each optical waveguide by an array optical waveguide (hereinafter referred to as "AWG optical waveguide") using a quartz optical waveguide. For example,
As shown in FIG. 4, when the signal light of λ1 to λ4 is input to one of the optical fibers 51 on the input side, the signal light demultiplexing device 50 causes the first lens 52, the AWG optical waveguide 53, and the second lens 54 to move. Then, from the plurality of optical fibers 55 on the output side to λ
The signal lights of 1, λ2, λ3, and λ4 are separately output. As described above, the one using the AWG optical waveguide has a drawback that the fabrication accuracy of the array structure is strict and that the entire array becomes large when the wavelength interval becomes small such as 50 GHz interval.

Thirdly, a grating structure is formed in the optical waveguide or the optical fiber, and the signal light of a single wavelength is reflected and taken out. For example, as shown in FIG.
When the signal light of n is input, the signal light of λ2 is 3 dB on the input side.
After being reflected by the gratings 67 and 68 via the coupler 65, the second port 62 is again transmitted via the input side 3 dB coupler 65.
While the signal light of λ2 to λn is output from the input side 3d
B coupler 65, gratings 67 and 68, and output side 3
It is configured to be output from the fourth port 64 via the dB coupler 66. Further, by inputting the light of λ1 from the third port 63, it is output to the output side 3 dB coupler 6
After being reflected by the gratings 67 and 68 via 6 and again output from the fourth port 64 via the output side 3 dB coupler 66. As described above, the one using a grating has a drawback that a submicron period grating is required to obtain wavelength selectivity, that is, a half width is narrowed, and an advanced fabrication technique is required.

Fourthly, a diffraction grating is formed in a directional coupler section using a semiconductor optical waveguide so that signal light of a single wavelength can be extracted. For example, as shown in FIG.
This signal light demultiplexing device 70 has λ1 to
When the signal light of λn is input, the signal light of λk is output from the drop port 72, while the signal light other than λk is output from the output port 73. Further, when light of λk is input from the add port 74, it is also output from the output port 73. As described above, the one using the semiconductor optical waveguide and the diffraction grating is useful because it has wavelength tuning property, but since the optical waveguide has a three-dimensional structure, the manufacturing process is very complicated, and in general, Since the semiconductor has a larger refractive index than the optical fiber, there is a drawback that the coupling loss with the optical fiber becomes large.

[0008]

SUMMARY OF THE INVENTION The object of the present application is to achieve S / N without being affected by signal lights of wavelengths close to each other.
It is an object of the present invention to provide a novel optical demultiplexing device and a novel signal optical demultiplexing method with a good ratio.

[0009]

According to the present invention, wavelength-converted light obtained by wavelength conversion using a quasi-phase matching method is output as separated signal light.

Specifically, the present invention is premised on a signal light demultiplexing device which selects and demultiplexes signal light of a predetermined wavelength from among wavelength division multiplexed signal lights. Then, while the wavelength division multiplexed signal light is input, only the signal light of a predetermined wavelength of the input wavelength division multiplexed signal light is wavelength-converted by using the quasi phase matching method, and the wavelength-converted signal light is converted. It is characterized by comprising a signal light separating element for outputting as separated signal light.

According to the above configuration, since wavelength conversion is performed only for a single wavelength and the wavelengths are separated, the separated signal light to be output depends on the signal light having a wavelength close to the original signal light. The S / N ratio is improved without being affected. As described above, selecting and separating only the predetermined signal light from the WDM signal light by using the wavelength conversion is a novel one whose technical idea is completely different from that of the conventional signal light separating apparatus.

In the present invention, the signal light demultiplexing device is a second harmonic generation light (Second Harmonic Generation: SH) of only the signal light of a predetermined wavelength in the input wavelength division multiplexed signal light.
G) may be generated as separated signal light. According to such a configuration, it is not necessary to input pumping light other than the WDM signal light to the signal light separation element, so that the configuration becomes simple. In addition, the intensity of the second-harmonic-generated light is obtained in proportion to the square of the signal light intensity, and its peak becomes clear, so that the S / N ratio becomes better.

Further, a pumping light source which emits pumping light to be inputted to the signal light separating element is further provided, and the signal light separating element is a signal light of a predetermined wavelength among the inputted wavelength division multiplexed signal light and the pumping light. It may be configured to generate the sum frequency generation light (Sum Frequency Generation: SFG) with the excitation light from the light source as the separated signal light.

As the signal light separating element, a non-linear optical crystal having a periodic polarization inversion structure can be mentioned.
According to such a configuration, the signal light separation element is composed only of the nonlinear optical crystal having the periodically poled structure, and the structure is simple, so that it can be easily manufactured. Also WDM
When the wavelength interval of the signal light is short, the length of the nonlinear optical crystal is increased to improve the wavelength resolution and improve the S / N ratio. Then, in this case, the wavelength division multiplexed signal light is input to the nonlinear optical crystal having a periodic polarization inversion structure, and only the signal light of a predetermined wavelength of the input wavelength division multiplexed signal light is wavelength-converted by the nonlinear optical crystal. By generating the second harmonic generation light and outputting the generated second harmonic generation light as the separation signal light from the nonlinear optical crystal, the signal light of a predetermined wavelength can be separated and extracted from the WDM signal light. .

Examples of the non-linear optical crystal forming the signal light separating element include lithium niobate, lithium tantalate, magnesium-added lithium niobate and magnesium-added lithium tantalate.

As a concrete embodiment of the present invention, a signal light input section to which the wavelength division multiplexed signal light is input is provided at one end, and a plurality of signal light output sections branched from the signal light input section are provided at the other end. Each of the plurality of signal light output sections is formed of a non-linear optical crystal having a periodically domain-inverted structure having mutually different periods, and each of the plurality of signal light output sections has a wavelength division multiplex from the signal light input section. When the signal light is input, only the signal light having a predetermined wavelength corresponding to the period of the periodically poled structure is wavelength-converted to generate its second harmonic generation light, and the generated second harmonic generation is generated. Configured to output light as separated signal light, or
A pumping light source that emits pumping light of a predetermined wavelength, and a plurality of signal light outputs branched at one end from a signal light input unit to which the pumping light from the pumping light source and the wavelength division multiplexed signal light are input. And a plurality of signal light output sections, each of which is formed of a non-linear optical crystal having a periodic domain-inverted structure having a different period from each other. The pumping light and the wavelength division multiplexed signal light are input from the input unit, and only the signal light of a predetermined wavelength corresponding to the period of the periodic polarization inversion structure is wavelength-converted from the wavelength division multiplexed signal light and the sum frequency thereof is obtained. An example is one that is configured to generate generated light and output the generated sum frequency generated light as separated signal light. According to such a configuration, a plurality of necessary signal lights can be independently separated and extracted from the WDM signal light, and if the output ends are provided by the number of wavelengths included in the WDM signal light, an arbitrary wavelength can be obtained. It is possible to detect the signal light of, and it is also effective as a wavelength monitor for monitoring which wavelength of the signal light is coming.

Further, in this structure, the optical waveguide is provided with an optical switch at the branching portion so that the wavelength division multiplexed signal light from the signal light input portion can be selectively inputted to a predetermined signal light output portion. It may be one that has been used. According to this configuration, the WDM signal light is guided to the non-linear optical crystal of the predetermined signal light output section by switching the optical switch, so that the loss of the WDM signal light can be reduced, so that the output signal light is also used. High strength can be obtained.

[0018]

As described above, according to the present invention,
Since the wavelength conversion is performed only for a single wavelength and the wavelength conversion is performed, the S / N ratio can be improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows a signal light demultiplexing device 10 for WDM signal light according to a first embodiment of the present invention.

This signal light separating apparatus 10 is a magnesium-doped lithium niobate (Periodically Poled MgO-doped) in which an optical waveguide 12 is formed by a proton exchange method.
LiNbO _3: hereinafter referred to as "PPMgLN") consisting of the substrate 11. The PPMgLN substrate 11 is made of a nonlinear optical crystal.

One end of the optical waveguide 12 has a signal light input portion 12
a, which branches into two, each branch into two, and each branch into two,
The other end has a total of eight signal light output units 13 from the first to the eighth.
a to 13h.

Each of the eight signal light output sections 13a to 13h is formed of a non-linear optical crystal having a periodically domain-inverted structure having mutually different periods, which constitutes a signal light separation element. The polarization inversion period of a nonlinear optical crystal is
The first signal light output section 13a has a wavelength of λ1, the second signal light output section 13b has a wavelength of λ2, and the third signal light output section 13c has a wavelength of λ3. Has become. The length of the nonlinear optical crystal forming the signal light output units 13a to 13h may be set according to the wavelength interval, and if it is 30 mm, the phase matching half width is about 0.
Since it is 3 nm, if it is 30 mm or more, it is possible to cope with the case where the wavelength interval is 50 GHz. The signal light output units 13a to 13h have silicon photodiodes (hereinafter referred to as "SPD") 14a to 14 at their terminal ends.
h is provided.

Next, W using this signal light separation device 10
The operation of separating DM signal light will be described.

First, when WDM signal light including signal lights of λ1 to λ8 is input to the signal light input unit 12a, it propagates through the optical waveguide 12 and the first to eighth signal light output units 13a to 1 are transmitted.
It is input to each nonlinear optical crystal of 3h.

Next, for example, the first signal light output section 13a
The non-linear optical crystal of
Of the M signal light, only the signal light of λ1 is wavelength-converted to generate the second harmonic generation light, which is output as the separated signal light. In each of the nonlinear optical crystals of the second to eighth signal light output sections 13b to 13h, similarly, only the signal light of λ2 to λ8 is wavelength-converted to generate the second harmonic generation light, which is the separated signal light. Is output as.

Then, the output separated signal lights of λ1 to λ8 are input to the respective SPDs 14a to 14h.

According to the optical signal demultiplexing device 10 having the above structure,
In each of the signal light output units 13a to 13h, wavelength conversion is performed only for a single wavelength to be separated, and the output separated signal light is not affected by the signal light having a wavelength close to the original signal light, Further, the intensity of the separated signal light which is the second harmonic generation light is obtained in proportion to the square of the signal light intensity, and its peak becomes clear, so that the S / N ratio becomes extremely good.

Further, signal light output sections 13a to 13 made of a nonlinear optical crystal having a periodically poled structure and a waveguide formed on the PPMgLN substrate 11 by a proton exchange method.
3h, and also the signal light output units 13a to 13
Since it is not necessary to input pumping light other than the WDM signal light to h, the structure is simple and it can be easily manufactured.

Further, when the WDM signal light has a short wavelength interval, the S / N ratio can be further improved by increasing the wavelength resolution by increasing the length of the nonlinear optical crystal.

Further, the signal light output units 13a to 13h are provided by the number of wavelengths included in the WDM signal light, and a plurality of necessary signal lights can be independently separated and extracted from the WDM signal light. It is possible to detect the signal light of the wavelength, and further it can be utilized as a wavelength monitor for monitoring which wavelength of the signal light is coming.

Thus, the selection and separation of a predetermined signal light from the WDM signal light by using the wavelength conversion is a novel one whose technical idea is completely different from that of the conventional signal light separating apparatus.

(Second Embodiment) FIG. 2 shows a signal light demultiplexing device 20 for WDM signal light according to a second embodiment of the present invention.
The same parts as those in the first embodiment are designated by the same reference numerals.

The signal light separating device 20 according to the first embodiment is provided with optical switches 21 to 27 at each branch of the optical waveguide 12. Each optical switch 21-
27 has an input port composed of first and second ports and an output port composed of third and fourth ports,
One input port and both output ports are used. Other configurations are the same as those in the first embodiment.

Next, W using this signal light separation device 20
The operation of separating DM signal light will be described.

First, when WDM signal light including the signal lights of λ1 to λ8 is input to the signal light input section 12a, it is first
It is input to the first port 21a of the optical switch 21, and when the first optical switch 21 is switched, for example, its third port 21c is input.
Is output (see the thick line in FIG. 2).

Next, the WDM signal light output from the third port 21c of the first optical switch 21 is input to the second port 22b of the second optical switch 22, and the second optical switch 2
When switched to 2, it is output to the fourth port 22d, for example.

Next, the WDM signal light output from the fourth port 22d of the second optical switch 22 is input to the first port 25a of the fifth optical switch 25, and the fifth optical switch 2
By switching of 5, the data is output to the third port 25c, for example.

Further, the WDM signal light output from the third port 25c of the fifth optical switch 25 is input to each nonlinear optical crystal of the third signal light output section 13c.

Then, in the nonlinear optical crystal of the third signal light output section 13c, only the signal light of λ3 of the WDM signal light is wavelength-converted by the quasi phase matching method, and the second harmonic generation light is generated. , Which is output as separated signal light.

Then, the separated signal light of λ3 outputted is S
It is input to the PD 14c.

According to the optical signal demultiplexer 20 having the above structure,
By guiding the WDM signal light to the non-linear optical crystal of the predetermined signal light output units 13a to 13h by switching the optical switches 21 to 27, the loss of the WDM signal light can be reduced, so that the signal light to be output is also provided. High strength can be obtained.

Other functions and effects are the same as those in the first embodiment.

(Third Embodiment) FIG. 3 shows a signal light demultiplexing device 30 for WDM signal light according to a third embodiment of the present invention.
The same parts as those in the first embodiment are designated by the same reference numerals.

The signal light separating device 30 is composed of the optical waveguide 12
A coupler 31 is provided in the signal light input section 12a of
The WDM signal light is input from one input port, and the pump light of the wavelength λ0 emitted from a pump light source (not shown) is input from the other input port. Other configurations are the same as those in the first embodiment.

Next, W using this signal light separation device 30
The operation of separating DM signal light will be described.

First, the WDM signal light including the signal lights of λ1 to λ8 and the wavelength λ0 from the pumping light source are input to the signal light input unit 12a.
When the pumping lights of are input, they propagate through the optical waveguide 12 and are input to each of the nonlinear optical crystals of the first to eighth signal light output sections 13a to 13h.

Next, for example, the first signal light output section 13a
The non-linear optical crystal of
Of the M signal lights, only the signal light of λ1 is wavelength-converted to generate the sum frequency generation light of the wavelength λ _OUT shown in the following formula, which is output as the separated signal light.

(1 / λ _OUT ) = (1 / λ1) + (1 / λ0) Even in each of the nonlinear optical crystals of the second to eighth signal light output sections 13b to 13h, similarly, only each signal light of λ2 to λ8. Is subjected to wavelength conversion to generate its sum frequency generation light, which is output as separated signal light.

Then, the output separated signal lights of λ1 to λ8 are input to the respective SPDs 14a to 14h.

According to the optical signal demultiplexing device 70 having the above structure,
In each of the signal light output units 13a to 13h, wavelength conversion is performed only for a single wavelength and the signal light is separated, and the output separated signal light is not affected by the signal light having a wavelength close to the original signal light. , S / N ratio becomes good.

Further, the signal light output portions 13a to 13a each of which is formed of a nonlinear optical crystal having a periodically poled structure and a waveguide formed on the PPMgLN substrate 11 by the proton exchange method.
3h is formed, the structure is simple and it can be easily manufactured.

Other functions and effects are the same as those in the first embodiment.

(Other Embodiments) Above-mentioned Embodiments 1 to 3
Then, the PPMgLN substrate 11 is used, but the PGMgLN substrate 11 is not particularly limited to this, and another substrate may be used.
For example, a substrate made of lithium niobate, lithium tantalate, magnesium-added lithium tantalate, or the like can be used.

Further, in the first to third embodiments, the SPDs 14a to 14h are provided after the signal light output units 13a to 13h, but the present invention is not limited to this, and signals from the signal light output units 13a to 13h are provided. A device may be provided that transmits light as an optical signal without converting the light into an electrical signal.
At that time, wavelength conversion may be performed to return the output signal light to the signal light before wavelength conversion.

Further, in the third embodiment, an optical switch may be provided at the branching portion as in the second embodiment.

[Brief description of drawings]

FIG. 1 is a plan view of a signal light separation device according to a first embodiment of the present invention.

FIG. 2 is a plan view of a signal light separation device according to a second embodiment of the present invention.

FIG. 3 is a plan view of a signal light separation device according to a third embodiment of the present invention.

FIG. 4 is a plan view of a first conventional signal light separation device.

FIG. 5 is a plan view of a second conventional signal light separation device.

FIG. 6 is a plan view of a third conventional signal light separation device.

FIG. 7 is a perspective view of a fourth conventional signal light separation device.

[Explanation of symbols]

10, 20, 30, 40, 50, 60, 70 Signal light separation device 11 PPMgLN substrate 12 Optical waveguide 12a Signal light input sections 13a to 13h Signal light output sections 14a to 14h SPD 21 to 27 Optical switches 21a, 25a, 41, 61 1st port 22b, 42, 62 2nd port 21c, 25c, 43, 63 3rd port 22d, 44, 64 4th port 31 Coupler 51, 55 Optical fiber 52 1st lens 53 AWG array 54 2nd lens 65 Input Side 3 dB coupler 66 Output side 3 dB coupler 67, 68 Grating 71 Input port 72 Drop port 73 Output port 74 Add port

Continued front page    (72) Inventor Junya Maeda             4-3 Ikejiri, Itami City, Hyogo Prefecture Mitsubishi Electric Cable             Industrial Co., Ltd. Itami Works F term (reference) 2K002 AA02 AB12 BA03 CA03 DA06                       EA07 FA26 FA27 GA04 GA10                       HA20                 5K002 AA07 BA05 BA06 BA15 CA05                       DA02 FA01

Claims (10)

[Claims] 1. A signal light demultiplexing device for selecting and demultiplexing signal light of a predetermined wavelength from wavelength division multiplexed signal light, wherein the wavelength division multiplexed signal light is inputted and the inputted wavelength division multiplexed signal is inputted. A signal light having a signal light separating element for wavelength-converting only the signal light of a predetermined wavelength of light using a quasi-phase matching method and outputting the wavelength-converted signal light as separated signal light. Separation device. 2. The signal light demultiplexing device according to claim 1, wherein the signal light demultiplexing device demultiplexes the second harmonic generation light of only the signal light of a predetermined wavelength from the input wavelength division multiplexed signal light. A signal light demultiplexing device, which is configured to generate as signal light. 3. The signal light splitting device according to claim 1, further comprising a pumping light source that emits pumping light to be input to the signal light splitting element, wherein the signal light splitting element receives the input wavelength division. A signal light separation device, which is configured to generate, as separation signal light, a sum frequency generation light of signal light of a predetermined wavelength and pumping light from the pumping light source among multiplexed signal light. 4. The signal light demultiplexing device according to claim 2, wherein the signal light demultiplexing element is composed of a non-linear optical crystal having a periodic domain inversion structure. . 5. The signal light separation device according to claim 4, wherein the nonlinear optical crystal forming the signal light separation element is lithium niobate, lithium tantalate, magnesium-added lithium niobate, or magnesium-added. A signal light separation device, characterized in that it is any one of lithium tantalate. 6. An optical waveguide comprising: a signal light input section for inputting wavelength division multiplexed signal light at one end; and a plurality of signal light output sections branched from the signal light input section at the other end. The plurality of signal light output sections are each formed of a non-linear optical crystal having periodic polarization inversion structures having mutually different periods,
The wavelength division multiplexed signal light from the signal light input unit is input, and only the signal light of a predetermined wavelength corresponding to the period of the periodic polarization inversion structure is wavelength-converted to generate its second harmonic generation light. And, the signal light separation device is configured to output the generated second harmonic generation light as separation signal light. 7. An excitation light source that emits excitation light of a predetermined wavelength,
An optical waveguide in which a signal light input section for inputting pumping light from the pumping light source and wavelength division multiplexed signal light is configured at one end and a plurality of signal light output sections branched from the signal light input section are configured at the other end. And, each of the plurality of signal light output sections is formed of a non-linear optical crystal having a periodic domain inversion structure having mutually different periods,
The pumping light and the wavelength division multiplexed signal light are input from the signal light input unit, and only the signal light of a predetermined wavelength corresponding to the period of the periodic polarization inversion structure is wavelength-converted from the wavelength division multiplexed signal light. A signal light separation device, which is configured to generate the sum frequency generation light and to output the generated sum frequency generation light as separated signal light. 8. The signal light demultiplexing device according to claim 6 or 7, wherein in the optical waveguide, the wavelength division multiplexed signal light from the signal light input unit can be selectively input to a predetermined signal light output unit. A signal light separation device, wherein an optical switch is provided in the branching portion so that 9. A signal light separation method for selecting and separating signal light of a predetermined wavelength from wavelength division multiplexed signal light, wherein the wavelength divided multiplexed signal light is input to a nonlinear optical crystal having a periodic polarization inversion structure, Of the input wavelength division multiplexed signal light, only the signal light of a predetermined wavelength is wavelength converted by the nonlinear optical crystal to generate its second harmonic generation light, and the generated second harmonic generation light is separated signal light. A method for separating signal light, characterized in that the light is output from the nonlinear optical crystal as. 10. A signal light separation method for selecting and separating signal light of a predetermined wavelength from wavelength division multiplexed signal light, wherein the pumping light of the predetermined wavelength and the wavelength division multiplexed signal light are non-linear having a periodic polarization inversion structure. Inputting to the optical crystal, only the signal light of a predetermined wavelength of the input wavelength division multiplexed signal light is wavelength-converted by the nonlinear optical crystal to generate its sum frequency generated light, and the generated sum frequency generated light is separated. A signal light separating method, wherein the signal light is output from the nonlinear optical crystal.