JP4454008B2 - Multi-wavelength batch wavelength converter and multi-wavelength batch wavelength conversion method - Google Patents

Description

  The present invention relates to a wavelength converter and a wavelength conversion method used in an optical node or the like in an optical network based on wavelength division multiplexing technology.

  The wavelength conversion method has the following advantages: (1) optical phase information can be retained in the conversion, (2) independent of the signal modulation speed, and (3) multi-wavelength input signal light can be converted in a batch. A parametric wavelength conversion method using an optical nonlinear medium is actively researched (see Non-Patent Documents 1, 2, and 3).

  As the parametric wavelength conversion method, there are a method using a third-order optical nonlinear effect in an optical fiber, an optical semiconductor amplifier, and the like, and a method using a second-order optical nonlinear effect in an optical nonlinear crystal or the like. The latter has advantages such as high conversion efficiency, compactness, possibility of integration, and small crosstalk between multi-wavelength input signal lights, and is a promising method (see Non-Patent Documents 4 and 5). .

  In wavelength conversion using the secondary light nonlinear effect, a sum frequency light generation / difference frequency light generation process of input signal light and excitation light is used. Usually, compared with the optical frequency band of signal light and pumping light, the optical frequency band of the sum frequency light generated by them differs by about twice as much as the optical frequency, so the difference in the phase velocity of light in both bands is large. . For this reason, the effective interaction distance between the light beams in both bands becomes as short as several tens of μm in the communication wavelength band (1.5 μm band), and high-efficiency conversion cannot be performed. The same applies to the difference frequency light generation process.

Therefore, in general, when using the second-order optical nonlinear effect, a quasi-phase matching (QPM) technique that periodically inverts the optical axis of the second-order nonlinear optical crystal is used in order to increase the effective interaction distance. The As a result, the generation efficiency of sum frequency light / difference frequency light generation in the secondary light nonlinear medium is improved, and high conversion efficiency is realized.
SJB Yoo, "Wavelength conversion technologies for WDM network applications," J. Lightwave Technol., Vol.14, No.6, 1996, pp.955-966 K. Inoue, "Tunable and selective wavelength conversion using fiber four-wave mixing with two pumps," IEEE Photonics Technology Letters, Vol. 6, No. 12, 1994 MH Chou, I. Brener, MM Fejer, EE Chaban, and SB Christman, "1.5μm-band wavelength conversion based on cascaded second-order nonlinearity in LiNbO3 waveguides," IEEE Photonics Technol. Letters, Vol. 11, No. 6, June 1999 M. Asobe, O. Tadanaga, T. Yamagawa, H. Itoh, and H. Suzuki, "Reducing photorefractive effect in periodically poled ZnO- and MgO- doped LiNbO3 wavelength converters," Applied Physics Letters, Vol. 78, No. 21 , May 2001 Tatsuo Kawaguchi, Takafumi Yoshino, Minoru Imae, Kiminori Mizuuchi, Yasuo Kitaoka, Kazuhisa Yamamoto "QPM-SHG Device Using Bonded Ridge Structure LN Optical Waveguide" IEICE Technical Report, LQE2002-8, 2002 , P. 29

In sum frequency light generation using a quasi-phase matching technique, an effective interaction is effective only when sum frequency light having an optical frequency of 2ν ₀ uniquely determined by the inversion period of the optical axis of the secondary optical nonlinear crystal is generated. The distance is increased, and high-efficiency sum frequency light generation is possible. The same applies to the generation of the difference frequency light. Only when the difference frequency light is generated between the light having the optical frequency 2ν _{0 and} the light in the vicinity of the optical frequency ν ₀ , the highly efficient difference frequency light can be generated.

Under such conditions, a method using two excitation lights has been proposed as a method for realizing arbitrary wavelength conversion in which the conversion destination wavelength can be arbitrarily controlled. In this case, the first pumping light having the optical frequency ν _P1 is used for the signal light having the optical frequency ν _s = 2ν ₀ −ν _P1 to generate the sum frequency light having the optical frequency 2ν _0. The signal light is converted into 2ν ₀ −ν _P2 = ν _c by the generation of the difference frequency light between the sum frequency light and the second excitation light having the optical frequency ν _P2 . Therefore, high-efficiency sum-frequency light generation / difference-frequency light generation is possible. By controlling the optical frequencies ν _P1 and ν _P2 of the pumping light, it is possible to input light of any optical frequency while maintaining high conversion efficiency. It can be converted into output light of any optical frequency.

If this method is applied when the input signal light is multi-wavelength light, it is necessary to generate a plurality of sum frequency lights. However, since the QPM secondary optical nonlinear medium can generate high-efficiency sum frequency light for only one optical frequency 2ν _0, it is impossible to perform batch arbitrary wavelength conversion of multi-wavelength input signal light. was there.

  An object of the present invention is to provide a multi-wavelength batch wavelength converter capable of collectively converting multi-wavelength input signal light having an arbitrary wavelength (optical frequency) into multi-wavelength converted light having an arbitrary wavelength (optical frequency). is there.

  In order to achieve the object, the present invention adopts the following characteristic configuration.

That is, in the first invention , as shown in FIG. 1, for an integer N of 2 or more, multiple wavelengths of arbitrary optical frequencies 2ν ₁ −ν _P1 , 2ν ₂ −ν _P1 , ... 2ν _N −ν _P1 . A multi-wavelength batch wavelength converter that converts input signal light into multi-wavelength converted light of arbitrary optical frequencies 2ν ₁ −ν _P2 , 2ν ₂ −ν _P2 ,... 2ν _N −ν _P2 , and has an optical frequency ν _P1. a first pumping light source 11, a second pumping light source 12 of the optical frequency [nu _P2, [nu ₁ as second harmonic light generation efficiency becomes maximum optical frequency (QPM optical frequency), ν _2, ...... ν _N , The multi-wavelength input signal light, the output light from the first excitation light source, and the output light from the second excitation light source are combined into the secondary optical nonlinear medium. The multi-wavelength batch wavelength converter having the multiplexing means 14 for input and the multi-wavelength batch wavelength conversion method are used as the solution means.

In the configuration of the first invention , the sum frequency light generation process and the difference frequency light generation process are performed by the same secondary light nonlinear medium 13. That is, the optical wavelengths 2ν ₁ −ν _P1 , 2ν ₂ −ν _P1 ,... 2ν _N −ν _P1 input to the secondary nonlinear optical medium 13 and the first excitation light having the optical frequency ν _P1 . 2ν ₁ , 2ν ₂ ,... 2ν _N is generated by the sum frequency light generation process between the optical frequency ν _P2 and the optical frequency ν _P2 input to the secondary optical nonlinear medium 13 in the same manner as the sum frequency light. Multi-wavelength converted light of 2ν ₁ −ν _P2 , 2ν ₂ −ν _P2 ,... 2ν _N −ν _P2 is obtained by the difference frequency light generation process with the second pumping light.

Further, in the second invention , as shown in FIG. 2, for an integer N of 2 or more, multiple wavelengths of arbitrary optical frequencies 2ν ₁ −ν _P1 , 2ν ₂ −ν _P1 ,... 2ν _N −ν _P1 A multi-wavelength batch wavelength converter that converts input signal light into multi-wavelength converted light of arbitrary optical frequencies 2ν ₁ −ν _P2 , 2ν ₂ −ν _P2 ,... 2ν _N −ν _P2 , and has an optical frequency ν _P1. a first pumping light source 11, a second pumping light source 12 of the optical frequency [nu _{P2, 1} [nu as an optical frequency second harmonic light generation efficiency becomes maximum, [nu _2, the first and the ...... ν _N First second-order nonlinear optical media 21 and 22, multi-wavelength input signal light and output light from the first pumping light source are combined and input to the first second-order nonlinear optical medium. The multiplexing means 23, the output light from the first secondary optical nonlinear medium, and the output light from the second pumping light source are multiplexed, and the second secondary optical nonlinear medium is combined. The multi-wavelength collective wavelength converter having the second combining means 24 for inputting to the quality and the multi-wavelength collective wavelength conversion method are used as the solving means.

In the configuration of the second invention , the sum frequency light generation process and the difference frequency light generation process are performed by two separate secondary optical nonlinear media 21 and 22 having the same QPM optical frequency. That is, multi-wavelength input signal light and first excitation light are input to the secondary optical nonlinear medium 21 at the front stage, and sum frequency light is generated by the process of generating the sum frequency light, and the secondary optical nonlinear medium 22 at the rear stage is generated. The sum frequency light and the second excitation light are input, and multi-wavelength converted light is obtained by the difference frequency light generation process.

By the way, in the configurations of the first and second aspects of the invention , the multi-wavelength input signal light, the first and second excitation lights, and the sum frequency light are actually output from the final stage together with the multi-wavelength converted light. In a wavelength converter used in an optical network, it is important to prevent excitation light and input signal light from being mixed into output light. Therefore, converted light using a wavelength variable filter such as a wavelength variable bandpass filter (BPF) is used. Only need to output.

Considering this point, in the third invention , as shown in FIG. 3, in the second invention , an optical frequency is provided between the first secondary optical nonlinear medium 21 and the second multiplexing means 24. 2ν ₁ , 2ν ₂ ,... A multi-wavelength collective wavelength converter provided with an optical filter 31 that transmits only 2ν _N light and a multi-wavelength collective wavelength conversion method are used as a solution.

In the configuration of the third invention , light in the vicinity of the wavelength band of the sum frequency light (for example, near 780 nm) is transmitted after the secondary optical nonlinear medium 21 in the previous stage, and the wavelength band of the input signal light and the excitation light (for example, 1550 nm band). By using the optical filter 31 such as a dichroic mirror having a wavelength characteristic for blocking the light of (), only the sum frequency light and the second excitation light can be input to the secondary optical nonlinear medium 22 in the subsequent stage. An advantage is that the input signal light and the first excitation light are blocked by the optical filter 31 and are not mixed into the converted light. However, since the second excitation light and the sum frequency light are mixed in the converted light, it is necessary to provide a wavelength tunable filter after the second-order nonlinear optical medium 22 and block it, as in the configurations of the first and second inventions. There is.

In the fourth invention (but not included in the scope of claims) , as shown in FIG. 4, for an integer N of 2 or more, an arbitrary optical frequency 2ν ₁ −ν _P1 , 2ν _2. −ν _P1 ............ 2ν _N −ν _P1 multi-wavelength input signal light is converted into multi-wavelength converted light of any optical frequency 2ν ₁ −ν _P2 , 2ν ₂ −ν _P2 ,… 2ν _N −ν _P2 A multi-wavelength batch wavelength converter, a first pumping light source 11 having an optical frequency ν _P1, a second pumping light source 12 having an optical frequency ν _P2 , and an optical frequency at which the second harmonic light generation efficiency is maximized ν ₁ , ν ₂ ,..., Ν _N containing the secondary optical nonlinear medium 13, the multi-wavelength input signal light and the output light from the first pumping light source are combined and input to the secondary optical nonlinear medium. First light combining means 41 and output light from the second-order nonlinear light medium are combined with output light from the second excitation light source, and the second-order light nonlinear medium The multi-wavelength collective wavelength converter having the second combining means 42 to be input again and the multi-wavelength collective wavelength conversion method are used as the solving means.

In the configuration of the fourth aspect of the invention , the sum frequency / difference frequency light generation process in the secondary optical nonlinear medium at the front stage / rear stage in the configuration of the second invention is changed to the forward / return path of one secondary optical nonlinear medium 13, respectively. To do. That is, the multi-wavelength input signal light and the first excitation light are input to the secondary optical nonlinear medium 13, sum frequency light is generated by the sum frequency light generation process, and is output from the secondary optical nonlinear medium 13. The light and the second excitation light are input again to the secondary light nonlinear medium 13, and multi-wavelength converted light is obtained by the difference frequency light generation process.

Further, in the configuration of the fourth aspect of the invention, similar to that of the first and second aspects of the invention, the multi-wavelength converted light to be finally output multi-wavelength input signal light, first, second excitation light and the sum Since the frequency light is mixed, it is necessary to provide a wavelength tunable filter before the first multiplexing means 41 so as to output only the converted light.

In consideration of this point, in the fifth invention (but not included in the scope of claims) , as shown in FIG. 4, in the fourth invention , the output light from the secondary optical nonlinear medium is Among them, second light combining means 42 'for combining only light of optical frequencies 2ν ₁ , 2ν ₂ ,... 2ν _N with the output light from the second pumping light source and inputting it again to the second-order nonlinear optical medium. The multi-wavelength collective wavelength converter and the multi-wavelength collective wavelength conversion method are used as solving means.

In the configuration of the fifth invention , the multi-wavelength input signal light out of the sum frequency light, the multi-wavelength input signal light, and the first pumping light output from the secondary optical nonlinear medium 13 by the second multiplexing means 42 ′ is used. The first excitation light is emitted to the outside as it is, and only the sum frequency light is input to the secondary optical nonlinear medium 13 together with the second excitation light. However, since the second excitation light and the sum frequency light are mixed in the converted light, it is necessary to provide a wavelength variable filter in front of the first multiplexing means 41 and block it as described above.

In the sixth invention , as shown in FIG. 5, for an integer N of 2 or more, multiple wavelengths of arbitrary optical frequencies 2ν ₁ −ν _P1 , 2ν ₂ −ν _P1 ,... 2ν _N −ν _P1 . A multi-wavelength batch wavelength converter that converts input signal light into multi-wavelength converted light of arbitrary optical frequencies 2ν ₁ −ν _P2 , 2ν ₂ −ν _P2 ,... 2ν _N −ν _P2 , and has an optical frequency ν _P1. a first pumping light source 11, a second pumping light source 12 of the optical frequency [nu _{P2, 1} [nu as an optical frequency second harmonic light generation efficiency becomes maximum, [nu _2, the first and the ...... ν _N The second secondary optical nonlinear medium 21 and 22 and the multi-wavelength input signal light are separated into two orthogonally polarized waves, and one of them is combined with a part of the output light from the first pumping light source. The first secondary light nonlinear medium is input to one end, and the other is combined with a part of the output light from the first excitation light source to combine the second secondary light nonlinear medium. Input to one end of the medium, or combine multi-wavelength input signal light and output light from the first excitation light source and separate them into two orthogonal polarizations, one of which is the first secondary A first multiplexing / demultiplexing means 51 that inputs to one end of the optical nonlinear medium and inputs the other to one end of the second secondary optical nonlinear medium, and an output from the other end of the first secondary optical nonlinear medium Light and a part of the output light from the second pumping light source are combined and input to the other end of the second secondary optical nonlinear medium, and from the other end of the second secondary optical nonlinear medium And a second multiplexing / demultiplexing means 52 that multiplexes a part of the output light from the second pumping light source and inputs it to the other end of the first secondary nonlinear medium. The solution is a wavelength batch wavelength converter and a multi-wavelength batch wavelength conversion method.

In the configuration of the sixth aspect of the invention , the first and second secondary nonlinear optical media 21 and 22 are respectively generated in the state where the sum frequency light / difference frequency light generation process is separated into two polarized waves orthogonal to each other. This is done using the forward / return route. That is, one polarization component of the multi-wavelength input signal light and the first pumping light are input to the first secondary optical nonlinear medium 21, and the multi-wavelength input signal light is input to the second secondary optical nonlinear medium 22. The other polarization component and the first pumping light are input, the sum frequency light is generated by the sum frequency light generation process, and the sum frequency light generated by the first secondary light nonlinear medium 21 and the second pumping light are generated. The light is input again to the second secondary optical nonlinear medium 22, and the sum frequency light and the second excitation light generated in the second secondary optical nonlinear medium 22 are input to the first secondary optical nonlinear medium 21. The signals are inputted again, and multi-wavelength converted lights are obtained by the difference frequency light generation process, and are combined. The optical power of the converted light does not depend on the polarization state of the input signal light, and a constant conversion efficiency is maintained.

In the configuration of the sixth invention, as in the configurations of the first, second, and fourth inventions , the multi-wavelength converted light that is finally output includes the multi-wavelength input signal light, the first and second pumps. Since light and sum frequency light are mixed, it is necessary to provide a wavelength tunable filter before the first multiplexing / demultiplexing means 51 so as to output only the converted light.

Considering this point, in the seventh invention , as shown in FIG. 5, in the sixth invention , the optical frequencies 2ν ₁ and 2ν ₂ of the output light from the other end of the first second-order nonlinear optical medium in the sixth invention . ,..., Only 2ν _N light is combined with a part of the output light from the second excitation light source and input to the other end of the second secondary light nonlinear medium, and the second secondary light is input. Of the output light from the other end of the nonlinear medium, only the light having the optical frequency 2ν ₁ , 2ν ₂ ,... 2ν _N is combined with a part of the output light from the second pumping light source, and the first two. The multi-wavelength collective wavelength converter having the second multiplexing / demultiplexing means 52 'for inputting to the other end of the next-order nonlinear medium and the multi-wavelength collective wavelength conversion method are used as the solution means.

In the configuration of the seventh invention , the sum frequency light, the multi-wavelength input signal light and the first pumping light output from the first and second secondary optical nonlinear media 21 and 22 by the second multiplexing / demultiplexing means 52 ′. Of the light, the multi-wavelength input signal light and the first excitation light are directly emitted to the outside, and only the sum frequency light is input to the first and second secondary nonlinear media 21 and 22 together with the second excitation light. To do. However, since the second excitation light and the sum frequency light are mixed in the converted light, it is necessary to provide a wavelength variable filter in front of the first multiplexing / demultiplexing means 51 and cut it off as described above.

In the configurations of the fourth to seventh inventions , since the multi-wavelength converted light propagates in the reverse direction on the input optical path of the multi-wavelength input signal light, the multi-wavelength converted light cannot be used as it is.

Considering this point, in the eighth invention , as shown in FIG. 6, in the fourth to seventh inventions ( the fourth or fifth invention in the figure), the multiwavelength input signal light and the multiwavelength converted light A multi-wavelength collective wavelength converter in which an optical irreversible circuit 61 for separating light into two directions according to the propagation direction is inserted in a portion in which the signals are propagated in opposite directions, and a solution means using the multi-wavelength collective wavelength conversion method To do.

In the configuration of the eighth invention, the light inputted from the port A is output to only the port B, the light input from the port B is output to only the port C, the light input from the port C to only the port A The multi-wavelength converted light is separated from the multi-wavelength input signal light by the optical irreversible circuit 61 such as an optical circulator for outputting.

  In FIG. 6, the optical irreversible circuit 61 is provided between the first multiplexing circuit 41 and the secondary optical nonlinear medium 13, but it may be provided before the first multiplexing circuit 41.

  When changing the optical frequency of the converted light, it is necessary to control the transmission wavelength of the wavelength tunable filter to output only the necessary converted light at the same time as changing the optical frequency of the second excitation light. There are problems such as complication of the configuration and limitation of the conversion wavelength switching speed due to the operating speed of the wavelength tunable filter.

Considering this point, in the ninth invention , as shown in FIG. 7, in the first to eighth inventions ( fifth invention + eighth invention in the figure), in the output optical path of the multi-wavelength converted light, Optical wavelength ν ₁ , ν ₂ ,... Long wavelength band transmission filter 71 having a cutoff optical frequency near ν _N or optical frequencies ν ₁ , ν ₂ ,..., Short wavelength band having a cutoff optical frequency near ν _N The multi-wavelength batch wavelength converter having the transmission filter 71 inserted therein and the multi-wavelength batch wavelength conversion method are used as the solving means.

In the ninth aspect of the invention , a long wavelength band transmission optical filter 71 having the cutoff optical frequency in the vicinity of the QPM optical frequency (ν ₁ , ν ₂ ,..., Ν _N ) as shown in FIG. Insert into the light output optical path. Basic operation of the configuration shown in FIG. 7 is similar to the configuration of the invention of the fifth aspect + 8 performs sum frequency light / difference frequency light generated respectively in the forward / backward. The multi-wavelength input signal light and the first excitation light are emitted to the outside by the second multiplexing means, but the second excitation light and the sum frequency light are mixed in the converted light output from the optical irreversible circuit 61. . This can be removed by using the optical filter 71 having the wavelength characteristics shown in FIG. 8, and only the multi-wavelength converted light can be output. However, in this example, the conversion destination wavelength is limited to the longer wavelength side than the QPM wavelength of the secondary optical nonlinear medium.

When the conversion destination wavelength is shorter than the QPM wavelength of the secondary optical nonlinear medium, transmission in a short wavelength band having the cutoff optical frequency near the QPM optical frequency (ν ₁ , ν ₂ ,..., Ν _N ). Use an optical filter.

  As described above, by using the multi-wavelength collective wavelength converter of the present invention, it becomes possible to collectively convert multi-wavelength input signal light having an arbitrary wavelength into multi-wavelength converted light having an arbitrary wavelength. .

FIG. 9 shows a first embodiment of a multi-wavelength batch wavelength converter according to the present invention, here an embodiment corresponding to the first invention . As an input signal light to the wavelength converter, a modulation rate of 10 Gbps is shown. Assuming wavelength multiplexed signal light having a wavelength multiplexing number of 4 waves, a multiplexed optical frequency interval Δν = 100 GHz, and signal light center optical frequencies ν _S1 , ν _S2 , ν _S3 , ν _S4 of each wavelength, this multi-wavelength input signal light Are collectively converted to optical frequencies ν _C1 , ν _C2 , ν _C3 , and ν _C4 , respectively.

In the figure, 101 is a first pumping light source having an optical frequency ν _P1 , 102 is a second pumping light source having an optical frequency ν _P2 , 103 is a secondary optical nonlinear medium, 104 and 105 are erbium-doped optical fiber amplifiers (EDFA), 106 and 107 are directional couplers, and 108 is a wavelength tunable bandpass filter (BPF).

  In the above configuration, the excitation light from the first excitation light source 101 and the second excitation light source 102 is amplified by the EDFAs 104 and 105 and then combined with the multi-wavelength input signal light via the directional couplers 106 and 107. Wave is input to the second-order nonlinear optical medium 103. The multi-wavelength converted light generated by the sum frequency light generation process and the difference frequency light generation process in the secondary light nonlinear medium 103 is transmitted through the wavelength variable BPF 108 and output.

  FIG. 10 shows an example of the arrangement of the optical frequencies of the multi-wavelength input signal light and the secondary optical nonlinear medium.

Here, as the second-order nonlinear optical medium 103, as shown in FIG. 10, the quasi-phase-matched optical frequency that maximizes the second-order harmonic light generation efficiency is set to the optical frequencies ν ₁ and ν ₂ at the optical frequency interval Δν / 2 = 50 GHz. , Ν ₃ , ν ₄ , a multi quasi phase matching lithium niobate waveguide (multi quasi phase matching LNWG) is used.

  Usually, there is only one quasi-phase-matched optical frequency, but in recent years, a method for realizing a plurality of phase-matched optical frequencies has been proposed and actually manufactured (for example, reference: M. Asobe, et. al., Optics Letters, Vol. 558-561, 2003). An example of the production method is shown below.

  A multi quasi phase matching (QPM) element can be produced by forming an optical waveguide on a lithium niobate substrate having a domain-inverted structure formed by applying an electric field. The polarization inversion structure for realizing the multi-QPM element can be realized by subjecting the periodic polarization inversion structure to continuous phase modulation as described in the above-mentioned reference, and repeating the structure with another period. An example of a manufacturing procedure of the element is shown below.

In this embodiment, a LiNbO ₃ Z plate (a substrate cut out so as to be a plane perpendicular to the Z axis) was used, and the polarization inversion portion was subjected to polarization inversion at a basic period of 15.5 μm by an electric field application method. SiO ₂ was patterned on the polarization-reversed substrate using a photolithography technique, immersed in benzoic acid at a temperature of about 180 ° C., and then heat-treated in an oxygen atmosphere to form a proton exchange waveguide. In the present embodiment, the apparatus is configured to support four excitation wavelengths. Details of the polarization inversion portion will be described below.

  When the second harmonic generation (SHG) is performed at 1.55 μm, the phase modulation period is set to 28.52 μm so that the frequency interval of the phase matching peak is 50 GHz, and the entire length of the polarization inversion unit is 57. The phase modulation pattern was repeated for two periods as 04 μm. The domain-inverted structure arranged per period of the phase modulation pattern is 1840 periods. In the present embodiment, the polarization inversion structure with a period of 15.5 μm is divided into units of every four periods, the phase modulation period is divided into 460, and the phase for each of the domain inversion structure units is optimized to obtain the maximum at the four excitation wavelengths. The conversion efficiency is obtained.

A method for producing a LiNbO ₃ substrate having a domain-inverted structure used in this embodiment will be briefly described. A resist is applied to the + Z surface of the LiNbO ₃ substrate, patterned using photolithography technology, electrodes are deposited, an electrolyte is brought into contact with both sides of the substrate, an electric field is applied, and the resist-free electrode is directly applied to the substrate. Inverts the polarization of the touched part.

  By using the multi-QPM-LNWG produced by the manufacturing method as described above, arbitrary wavelength conversion is possible even for multi-wavelength input signal light. Details of the principle are shown.

The sum frequency light generation efficiency η of the first pumping light and the light of each wavelength ν _{S1 to} ν _S4 of the multi-wavelength input signal light in the QPM-LNWG is approximately expressed by the equation (1) using the proportional coefficient c. It is expressed as follows.

Where β (ν _Sn ) is the propagation constant of each signal light, β (ν _P1 ) is the propagation constant of the first excitation light, β (ν _Sk + ν _P1 ) is the propagation constant of the sum frequency light of both, and L is It is the waveguide length of QPM-LNWG103. Δβ _n0 is a constant uniquely determined by the optical axis inversion period, and is represented by the following equation.

Here, since the optical frequency interval of the multi-wavelength input signal light is twice the quasi-phase matched optical frequency interval of the QPM-LNWG 103, the first frequency so as to satisfy ν _Sn + ν _P1 = 2ν _n for any _n . It is possible to set the optical frequency ν _P1 of the excitation light.

  Using this, equation (1) can be transformed into equation (3).

Furthermore, ν _Sn is assumed to have an optical frequency near ν _n (| ν _Sn / ν _n −1 | << 1), β (ν) is developed near ν _n , and higher-order terms are ignored. Thus, equation (3) can be transformed into equation (4).

Therefore, [nu _Sn is sufficiently [nu _n vicinity when it is _{(| | ν Sn / ν n} -1 «1), by using the first excitation light optical frequency [nu _P1, signals of any optical frequency [nu _Sn It can be seen that highly efficient sum frequency generation is possible for light.

  FIG. 11 shows the generation of sum frequency light and difference frequency light.

As shown in FIG. 11A, the signal light of each optical frequency ν _Sn is converted into the signal light of optical frequency 2ν _n by the sum frequency light generation. Further, converted light is obtained by generating a difference frequency light between each sum frequency light and the second excitation light. It is possible to set ν _P2 so as to satisfy ν _Cn + ν _P2 = 2ν _n for an arbitrary n as the optical frequency ν _P2 of the second pumping light. In this process, the same principle as above is used. Thus, the quasi-phase matching is satisfied, and high-efficiency difference frequency light generation is realized (FIG. 11B).

Also, although the destination optical frequency is controllable by varying the [nu _P2, because it satisfied irrespective quasi-phase matching in [nu _P2, higher sum frequency / difference frequency light generation efficiency for any [nu _P2 The power of the converted light does not fluctuate even if the conversion destination optical frequency is changed. Here, the quasi phase matching optical frequency is half of the multiple optical frequency interval Δν, but may be a fraction of an integer.

FIG. 12 shows a second embodiment of the multi-wavelength batch wavelength converter of the present invention, here an embodiment corresponding to the seventh invention , in which 111 is the first excitation light source, 112 is The second pumping light source, 113 is a first secondary optical nonlinear medium (QPM-LNWG), 114 is a second secondary optical nonlinear medium (QPM-LNWG), 115 and 116 are EDFAs, 117 is a multiplexer, 118 is a polarization-dependent beam splitter (PBS), 119 is a polarization rotator, 120 is a beam splitter, and 121 is a mirror that reflects light in the 780 nm band and transmits light in the 1550 nm band.

Here, the multiplexer 117, the PBS 118, and the polarization rotator 119 constitute the first multiplexing / demultiplexing means referred to in the seventh invention , and the beam splitter 120 and the mirror 121 are the second multiplexing / demultiplexing referred to in the seventh invention. Constitutes wave means.

  In the above-described configuration, the multi-wavelength input signal light is generated by the first pumping light source 111, combined with the first pumping light amplified by the EDFA 115 by the multiplexer 117, and then the polarization beam splitter (PBS) 118. Is separated into two orthogonally polarized waves. One polarization component is input to the QPM-LNWG 113 as it is, and the other polarization component is rotated 90 degrees by the polarization rotator 119 and input to the QPM-LNWG 114 to cause sum frequency light generation.

  Of the output light from each of the QPM-LNWGs 113 and 114, only the sum frequency light is reflected by the mirror 121 and input to the other QPM-LNWG 114 and 113. At this time, the light is generated by the second excitation light source 112, amplified by the EDFA 116, and multiplexed with the second excitation light equally divided by the beam splitter 120.

  In each of the QPM-LNWGs 113 and 114, the input sum frequency light and the second excitation light propagate in the opposite direction to the sum frequency light generation process and cause difference frequency light generation. The generated difference frequency light is multiplexed by the PBS 118, and converted into multi-wavelength converted light, which is output from the input signal light input port of the PBS 118. Thereafter, the light is separated from the input optical path by an optical non-reciprocal circuit (not shown) and output.

  In this configuration, the input signal light is separated into two orthogonal polarizations, and after being individually wavelength-converted, the input signal light is multiplexed, so that a constant conversion efficiency can be maintained for any polarization state.

  The insertion position of the optical irreversible circuit may be either between the PBS 118 and the multiplexer 117, or before the multiplexer 117. In FIG. 12, the multi-wavelength input signal light is separated into two orthogonal polarizations after being combined with the first excitation light, but only the multi-wavelength input signal light is separated into two orthogonal polarizations. Thereafter, the first excitation light may be multiplexed for each of them.

The block diagram which shows the outline | summary of the multi-wavelength batch wavelength converter of 1st invention The block diagram which shows the outline | summary of the multi-wavelength batch wavelength converter of 2nd invention The block diagram which shows the outline | summary of the multi-wavelength batch wavelength converter of 3rd invention Configuration diagram showing an outline of the multi-wavelength batch wavelength converter of the fourth and fifth inventions Configuration diagram showing an outline of a multi-wavelength batch wavelength converter of the sixth and seventh inventions The block diagram which shows the outline | summary of the multi-wavelength batch wavelength converter of 8th invention The block diagram which shows the outline | summary of the multi-wavelength batch wavelength converter of 9th invention Characteristic diagram showing an example of frequency characteristics of a fixed wavelength filter The block diagram which shows 1st Embodiment of the multi-wavelength batch wavelength converter of this invention Characteristic diagram showing an example of arrangement of optical frequencies of multi-wavelength input signal light and secondary optical nonlinear medium Explanatory drawing showing how sum frequency light generation and difference frequency light generation occur The block diagram which shows 2nd Embodiment of the multi-wavelength batch wavelength converter of this invention

  11, 101, 111: first excitation light source, 12, 102, 112: second excitation light source, 13, 21, 22, 113, 114: secondary optical nonlinear medium, 14, 23, 24, 41, 42, 42 ': multiplexing means, 31: optical filter, 51, 52, 52': multiplexing / demultiplexing means, 61: optical irreversible circuit, 71: wavelength fixed filter, 103: multi-pseudo phase matching LNWG, 104, 105, 115 116: EDFA, 106, 107: directional coupler, 108: wavelength tunable BPF, 117: multiplexer, 118: PBS, 119: polarization rotator, 120: beam splitter, 121: mirror.

Claims (14)

For two or more integer N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multi-wavelength batch wavelength converter that converts to 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of the optical frequency [nu _P2,
[Nu ₁ as an optical frequency second harmonic light generation efficiency becomes maximum, [nu _2, a secondary optical nonlinear medium comprising ...... ν _N,
A multiplexing means for combining the multi-wavelength input signal light, the output light from the first excitation light source, and the output light from the second excitation light source, and inputting the combined light to the secondary optical nonlinear medium. Multi-wavelength batch wavelength converter characterized. For two or more integer N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multi-wavelength batch wavelength converter that converts to 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of optical frequency ν _P2 ;
First and second second-order nonlinear optical media including ν ₁ , ν ₂ , ν _N as optical frequencies at which the second-harmonic light generation efficiency is maximized;
First multiplexing means for multiplexing multi-wavelength input signal light and output light from the first pumping light source and inputting the multiplexed light to the first secondary optical nonlinear medium;
Second combining means for combining the output light from the first secondary light nonlinear medium and the output light from the second pumping light source and inputting the combined light to the second secondary light nonlinear medium; A multi-wavelength batch wavelength converter characterized by comprising: The multi-wavelength batch wavelength converter according to claim 2,
An optical filter that transmits only light having an optical frequency of 2ν ₁ , 2ν ₂ ,... 2ν _N is provided between the first secondary optical nonlinear medium and the second multiplexing means. Wavelength batch wavelength converter. For two or more integer N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multi-wavelength batch wavelength converter that converts to 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of optical frequency ν _P2 ;
First and second second-order nonlinear optical media including ν ₁ , ν ₂ , ν _N as optical frequencies at which the second-harmonic light generation efficiency is maximized;
The multi-wavelength input signal light is separated into two orthogonally polarized waves, and one of them is combined with a part of the output light from the first pumping light source to one end of the first secondary optical nonlinear medium. The other is combined with a part of the output light from the first excitation light source and input to one end of the second secondary optical nonlinear medium, or the multi-wavelength input signal light and the first excitation The output light from the light source is multiplexed and separated into two orthogonal polarized waves, one of which is input to one end of the first secondary optical nonlinear medium, and the other is input to the second secondary optical nonlinear First multiplexing / demultiplexing means for inputting to one end of the medium;
The output light from the other end of the first secondary light nonlinear medium and the part of the output light from the second excitation light source are combined and input to the other end of the second secondary light nonlinear medium. And combining the output light from the other end of the second secondary optical nonlinear medium and a part of the output light from the second pumping light source to combine the other end of the first secondary optical nonlinear medium. And a second wavelength multiplexing / demultiplexing means for inputting to the multi-wavelength batch wavelength converter. The multi-wavelength batch wavelength converter according to claim 4 ,
Wherein among light frequency 2v ₁ of the output light from the other end of the first secondary optical nonlinear medium, 2v _2, only light of ...... 2ν _N combined with the part of the output light from the second excitation light source And input to the other end of the second secondary optical nonlinear medium, and light having optical frequencies of 2ν ₁ , 2ν ₂ ,... 2ν _N out of the output light from the other end of the second secondary optical nonlinear medium. And a second multiplexing / demultiplexing unit that multiplexes only a part of the output light from the second excitation light source and inputs it to the other end of the first second-order nonlinear optical medium. Wavelength batch wavelength converter. The multi-wavelength batch wavelength converter according to claim 4 or 5 ,
Multi-wavelength collective, characterized in that an optical non-reciprocal circuit that separates light into two directions according to the propagation direction is inserted in the part where multi-wavelength input signal light and multi-wavelength converted light propagate in opposite directions Wavelength converter. The multi-wavelength batch wavelength converter according to any one of claims 1 to 6 ,
The output path of the multi-wavelength converted light, optical frequency ν _1, ν _2, ...... ν long wavelength transmission filter or optical frequency [nu ₁ having a cut-off light frequency around _N, [nu _2, cut around ...... [nu _N A multi-wavelength batch wavelength converter, wherein a short wavelength band transmission filter having an off-light frequency is inserted. For two or more integer N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multiple wavelength batch wavelength conversion method for converting into 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of optical frequency ν _P2 ;
Using a second-order nonlinear optical medium including ν ₁ , ν ₂ , ν _N as the optical frequencies at which the second-harmonic light generation efficiency is maximized,
Multi-wavelength input signal light, output light from the first excitation light source, and output light from the second excitation light source are combined and input to the second-order nonlinear optical medium. Wavelength conversion method. For two or more integer N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multiple wavelength batch wavelength conversion method for converting into 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of optical frequency ν _P2 ;
Using first and second second-order nonlinear optical media including ν ₁ , ν ₂ ,... Ν _N as optical frequencies at which the second-harmonic light generation efficiency is maximized,
Multi-wavelength input signal light and output light from the first excitation light source are combined and input to the first secondary optical nonlinear medium,
A multi-wavelength package characterized in that the output light from the first secondary light nonlinear medium and the output light from the second pumping light source are combined and input to the second secondary light nonlinear medium. Wavelength conversion method. In the multiple wavelength batch wavelength conversion method according to claim 9 ,
Of the output light from the first secondary optical nonlinear medium, only the light with optical frequencies 2ν ₁ , 2ν ₂ ,... 2ν _N is combined with the output light from the second excitation light source, and the second A multi-wavelength batch wavelength conversion method characterized by inputting to a secondary optical nonlinear medium. Respect integer of 2 or more N, any optical frequency _{2ν 1 -ν P1, 2ν 2 -ν} P1, ...... 2ν N arbitrary optical frequency -v _P1 multi-wavelength input signal light of each 2v ₁ -v _P2, 2ν ₂ −ν _P2 ............ Multiple wavelength batch wavelength conversion method for converting into 2ν _N −ν _P2 multi-wavelength converted light,
A first excitation light source having an optical frequency ν _P1 ;
A second excitation light source of optical frequency ν _P2 ;
Using first and second second-order nonlinear optical media including ν ₁ , ν ₂ ,... Ν _N as optical frequencies at which the second-harmonic light generation efficiency is maximized,
The multi-wavelength input signal light is separated into two orthogonally polarized waves, and one of them is combined with a part of the output light from the first pumping light source to one end of the first secondary optical nonlinear medium. The other is combined with a part of the output light from the first excitation light source and input to one end of the second secondary optical nonlinear medium, or the multi-wavelength input signal light and the first excitation The output light from the light source is multiplexed and separated into two orthogonal polarizations, one of which is input to one end of the first secondary optical nonlinear medium, and the other is input to the second secondary optical nonlinear Input to one end of the medium,
The output light from the other end of the first secondary light nonlinear medium and the part of the output light from the second excitation light source are combined and input to the other end of the second secondary light nonlinear medium. And combining the output light from the other end of the second secondary optical nonlinear medium and a part of the output light from the second pumping light source to combine the other end of the first secondary optical nonlinear medium. A multi-wavelength batch wavelength conversion method characterized by: In the multiple wavelength batch wavelength conversion method according to claim 11 ,
Of the output light from the other end of the first second-order nonlinear optical medium, only light with optical frequencies 2ν ₁ , 2ν ₂ ,... 2ν _N is combined with a part of the output light from the second excitation light source. And input to the other end of the second secondary optical nonlinear medium, and light having optical frequencies of 2ν ₁ , 2ν ₂ ,... 2ν _N out of the output light from the other end of the second secondary optical nonlinear medium. A multi-wavelength collective wavelength conversion method characterized in that only a part of the output light from the second excitation light source is combined and input to the other end of the first secondary nonlinear optical medium. The multi-wavelength batch wavelength conversion method according to claim 11 or 12 ,
A multi-wavelength batch characterized by separating multi-wavelength input signal light and multi-wavelength converted light propagating in opposite directions using an optical irreversible circuit that separates light into two paths according to the propagation direction Wavelength conversion method. The multi-wavelength batch wavelength conversion method according to any one of claims 8 to 13 ,
Optical wavelength ν ₁ , ν ₂ ,... Long wavelength band pass filter with cutoff optical frequency near ν _N or optical frequency ν ₁ , ν ₂ ,... Short wavelength band transmission with cutoff optical frequency near ν _N A multi-wavelength batch wavelength conversion method, wherein only a multi-wavelength converted light is extracted from an output optical path of the multi-wavelength converted light using a filter.

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