Wavelength adapter and wavelength correction method

Abstract

This wavelength adaptor comprises: a first conversion unit; a first filter; a second conversion unit; and a second filter. The first conversion unit converts first signal light into second signal light having a wavelength, which is not included in a target wavelength band, by means of first pump light while maintaining the phase relationship of the first signal light. The first filter shuts off the first signal light and the first pump light, but transmits the second signal light. The second conversion unit converts the second signal light transmitted through the first filter into third signal light having a wavelength, which is within the target wavelength band, by means of second pump light while maintaining the phase relationship of the second signal light. The second filter shuts off the second signal light and the second pump light, but transmits the third signal light.

Description

[Technical field]

[0001] The present invention relates to a wavelength adapter and a wavelength modification method. [Background technology]

[0002] All-Photonics Network (APN) provides end-to-end, full-mesh optical paths. APN uses an optical GW (Photonic Gateway) as one of the optical nodes (see Non-Patent Document 1, for example). The optical GW has a transmission / stop function that transmits signal light and stops unnecessary signal light when a line is opened. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Tomoaki Yoshida, "Photonic Gateway and Optical Access Technologies Supporting APN," NTT Technical Journal, February 2021, pp. 36-41 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to avoid affecting other traffic, the optical gateway blocks the input of a signal light with a wavelength other than that set. Therefore, if a wavelength shift occurs in the signal light, the optical gateway blocks the signal light with the shifted wavelength. This can cause problems such as traffic not being able to flow.

[0005] In view of the above circumstances, an object of the present invention is to provide a wavelength adapter and a wavelength correction method capable of correcting the wavelength shift of signal light. [Means for solving the problem]

[0006] A wavelength adapter of one embodiment of the present invention includes a first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light, a first filter that blocks the first signal light and the first pump light and transmits the second signal light, a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by a second pump light while maintaining a phase relationship of the second signal light, and a second filter that blocks the second signal light and the second pump light and transmits the third signal light.

[0007] A wavelength correction method according to one embodiment of the present invention includes a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by using a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; and a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light. Effect of the Invention

[0008] According to the present invention, it is possible to correct the wavelength shift of the signal light. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of a wavelength adapter according to a first embodiment of the present invention. [Diagram 2] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Diagram 3] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 4] 4 is a diagram showing a transmission width of a filter according to the same embodiment. FIG. [Diagram 5] 4 is a diagram showing a transmission width of a filter according to the same embodiment. FIG. [Figure 6] 4 is a diagram showing a transmission width of a filter according to the same embodiment. FIG. [Figure 7] 4 is a diagram showing a transmission width of a filter according to the same embodiment. FIG. [Figure 8] 4 is a diagram showing a transmission width of a filter according to the same embodiment. FIG. [Figure 9] FIG. 11 is a configuration diagram of a wavelength adapter according to a second embodiment. [Figure 10] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 11] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 12] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 13] FIG. 11 is a configuration diagram of a wavelength adapter according to a third embodiment. [Figure 14] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 15] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 16] 4 is a diagram showing the transmission characteristics of the filter according to the embodiment. FIG. [Figure 17] 4 is a diagram showing a transmission width of a duplexer according to the same embodiment. FIG. [Figure 18] FIG. 13 is a configuration diagram of an optical GW according to a fourth embodiment. [Figure 19] FIG. 2 is a configuration diagram of an optical gateway according to the embodiment. [Figure 20] FIG. 13 is a configuration diagram of an optical GW according to a fifth embodiment. [Figure 21] FIG. 2 is a configuration diagram of an optical GW according to the embodiment. [Figure 22] FIG. 2 is a configuration diagram of an optical gateway according to the embodiment. [Diagram 23] FIG. 2 is a configuration diagram of an optical GW according to the embodiment. [Figure 24] FIG. 2 is a configuration diagram of an optical GW according to the embodiment. [Diagram 25]FIG. 2 is a configuration diagram of an optical GW according to the embodiment. [Figure 26] FIG. 13 is a configuration diagram of a wavelength adapter according to a sixth embodiment. [Figure 27] 1A and 1B are diagrams illustrating examples of wavelengths of signal light before and after wavelength modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the same parts in the various drawings are given the same reference numerals, and the description thereof will be omitted.

[0011] The wavelength adapter according to the embodiment of the present invention corrects the wavelength of the signal light by performing two-stage wavelength conversion. Correcting the wavelength means returning a wavelength that is deviated from a desired wavelength band to a wavelength within the desired wavelength band.

[0012] One of the problems in correcting a wavelength is that when the original wavelength shift is small, the signal light before and after wavelength correction overlap on the wavelength axis, making it impossible to separate the signal lights. FIG. 27 is a diagram showing an example of the wavelength of the signal light before and after wavelength correction. In a network having equipment such as an optical GW (gateway), most of the wavelengths of the signal light Q1 before correction are within the wavelength band w allowed for the signal light, and only some of the wavelengths are outside the wavelength band w. In a type of wavelength conversion that preserves phase information when converting phase information, as described later, both the original signal light and the converted signal light are often output together. The wavelength conversion is performed by blocking the original signal light from the signal lights and extracting the converted signal light. Therefore, if the entire wavelength of the signal light Q1 is corrected to be within the wavelength band w, many of the wavelengths of the signal light Q1 before correction and the signal light Q2 after correction overlap. In such a case, the signal light Q2 after correction cannot be extracted. Therefore, the wavelength adapter of this embodiment first converts the signal light to be wavelength-corrected into signal light with a wavelength that does not overlap on the wavelength axis with the final target wavelength band w after the wavelength correction, and then converts the converted signal light back into signal light with a wavelength within the wavelength band w. This allows the wavelength-shifted traffic to be conducted at a wavelength that does not affect other traffic.

[0013] In addition to the above, when modifying the wavelength of the signal light, the phase information of the signal light must be maintained before and after the modification. For example, optical gate type wavelength conversion using modulation or cross phase modulation loses phase information due to wavelength conversion. In other words, the signal light does not become transparent before and after wavelength conversion. For this reason, optical gate type wavelength conversion is not adopted in this embodiment.

[0014] On the other hand, lightwave mixing type wavelength conversion such as four-wave mixing and difference frequency generation can maintain phase information. In this wavelength conversion, the spectrum shape undergoes wavelength inversion, and the time variation of the phase (chirp) also undergoes sign inversion (phase conjugation). However, by changing the wavelength an even number of times, the phase inversion returns to the original state. Therefore, in this embodiment, lightwave mixing type wavelength conversion is adopted. Lightwave mixing type wavelength conversion is described, for example, in Reference 1 below. Furthermore, cross-phase modulation type wavelength conversion maintains phase information. Therefore, in this embodiment, cross-phase modulation type wavelength conversion may be adopted. Cross-phase modulation type wavelength conversion is described, for example, in Reference 2 below.

[0015] (References 1) Eiichi Yamada et al., "Wavelength conversion of signal light using sideband generation by modulation," IEICE Transactions on Information and Communication Engineers, Vol. J96-C, No. 10, pp. 265-274 (Reference 2) Nobuyuki Matsuda, "Lossless Wavelength Conversion of Single Photons," NTT Technical Journal, May 2017, pp. 15-19

[0016] In the following explanation, degenerate four-wave mixing will be taken as an example of lightwave mixing-type wavelength conversion, but the same applies to non-degenerate four-wave mixing, difference frequency generation, and cross-phase modulation. In addition, if the wavelength is λ (m), the speed of light is c (m / s), and the frequency is f (Hz), then the relationship λ [m] = c [m / s] ÷ f [Hz] holds. In this way, since the wavelength and the frequency are converted to each other, it is possible to specify the frequency by the wavelength, and it is also possible to specify the wavelength by the frequency. In the same way, the wavelength bandwidth and the frequency bandwidth can be converted to each other. In the following, the frequency of the optical signal will also be referred to as the optical frequency.

[0017] [First embodiment] 1 is a diagram showing an example of the configuration of a wavelength adapter 100 according to the first embodiment. The wavelength adapter 100 has light sources 111 and 121, wavelength conversion elements 112 and 122, and filters 113 and 123.

[0018] The light source 111 generates a pump light P11 with a variable wavelength. The light source 121 generates a pump light P12 with a fixed or variable wavelength. The pump light P11 is a first pump light, and the pump light P12 is a second pump light. Here, the light source 111 and the light source 121 generate the pump light P11 and the pump light P12 of degenerate four-wave mixing, respectively. In addition, when generating non-degenerate pump light, the light source 111 and the light source 121 generate a plurality of pump lights. Therefore, when performing wavelength conversion using a plurality of pump lights, the pump light in the embodiment may be replaced with a pump light group. For example, the first pump light may be replaced with the first pump light group, and the second pump light may be replaced with the second pump light group. When the pump light is replaced with the pump light group, the frequency relationship between the pump light group and the signal light and the idler light may be made to correspond to the frequency relationship between the pump light and the signal light and the idler light. The wavelength adapter 100 may not be provided with the light source 111 and may input the pump light P11 from outside. The wavelength adapter 100 may not be provided with the light source 121 and may input the pump light P12 from outside. The wavelength (optical frequency) of the pump light P11 is set according to the wavelength difference (optical frequency difference) to be converted. Here, the pump light P11 is set to a variable wavelength and the pump light 12 is set to a fixed wavelength or a variable wavelength, but the pump light P11 may be set to a fixed wavelength and the pump light 12 to a variable wavelength.

[0019] The wavelength conversion element 112 and the wavelength conversion element 122 include a nonlinear medium. The nonlinear medium is an optical fiber, a periodically poled lithium niobate (PPLN), a semiconductor optical amplifier (SOA), or the like. When an optical frequency corresponding to the wavelength of the pump light is fa and an optical frequency corresponding to the wavelength of the signal light is fb, the wavelength conversion element 112 and the wavelength conversion element 122 generate an idler light having a wavelength corresponding to an optical frequency (2fa-fb). The wavelength conversion element 112 receives the pump light P11 from the light source 111 and the signal light Q11 to be wavelength-corrected, and outputs the signal light Q12 of the idler light. The wavelength conversion element 122 receives the pump light P12 from the light source 121 and the signal light Q12 from the filter 113, and generates the signal light Q13 of the idler light. The signal light Q13 is the signal light corrected to the wavelength of the correction target. The corrected target wavelength is referred to as a target wavelength, and the frequency corresponding to the target wavelength is referred to as a target frequency.

[0020] The filter 113 blocks a wavelength band including the wavelengths of the pump light P11 and the signal light Q11, and transmits a wavelength band including the wavelength of the signal light Q12. That is, the filter 113 blocks a frequency band including the frequency of the pump light P11 and the frequency of the signal light Q11, and transmits a frequency band including the frequency of the signal light Q12. The filter 123 blocks a wavelength band including the wavelengths of the pump light P12 and the frequency of the signal light Q12, and transmits a wavelength band including the wavelength of the signal light Q13. That is, the filter 123 blocks a frequency band including the frequency of the pump light P12 and the frequency of the signal light Q12, and transmits a frequency band including the frequency of the signal light Q13.

[0021] FIG. 2 is a diagram showing the transmission characteristic of the filter 113, and FIG. 3 is a diagram showing the transmission characteristic of the filter 123. In the transmission characteristic, the line above the frequency axis means transmission, and the line below means blocking. The blocking characteristic is expressed by an ideal step function, but as long as light of a frequency indicated by an upward arrow in the transmission region can be transmitted and light of a frequency in the blocking region can be blocked, a blocking characteristic that is gentler than a step function may be used. When pump light groups are used and the pump light groups are arranged between the signal light and the idler light on the frequency axis, it is sufficient to block the signal light and the pump light groups. When an idler light is arranged in the pump light groups on the frequency axis, it is sufficient to block the pump light groups and the signal light on the signal light side of the idler light, and the pump light groups on the opposite side of the signal light from the idler light, respectively, and to transmit the idler light. The operation of the wavelength adapter 100 will be described with reference to FIGS. 1 to 3. The wavelength adapter 100 corrects the wavelength of the signal light Q11, which is shifted in wavelength, to a target wavelength within a target wavelength band. The frequency corresponding to the target wavelength of the signal light Q11 is set as a target frequency fs1.

[0022] The pump light and the signal light have wavelength widths (frequency widths). The unmodulated pump light has a wavelength width equal to its linewidth. The signal light has a wavelength width equal to the modulation sideband in addition to the linewidth. In cases such as when the signal light is directly modulated, the wavelength width is also affected by chirp. The center of the frequency of the signal light, the maximum peak of the spectrum, and the center of the spread of the modulation sideband may not coincide. In such cases, the median of the full width at half maximum (FWHM, 3 dB width) of the spectrum of the signal light, the median of the 20 dB width of the spectrum of the signal light, the value at which the peak of the spectrum of the signal light is maximum, and the value that contains the most of the modulation sideband or the main lobe of the modulation sideband included in the wavelength width (optical frequency width) allowed for the signal light are selected and regarded as the frequency or wavelength of the signal light. The value that contains the most is, for example, a value that contains more than half of the modulation sidebands on both sides or one side. The same applies to the following embodiments.

[0023] The wavelength adapter 100 inputs the signal light Q11 with a frequency (fs1-d1). That is, a frequency shift of d1 occurs in the signal light Q11. The light source 111 generates the pump light P11 with a frequency (fp-d1 / 2). That is, the wavelength of the pump light P11 is a wavelength corresponding to a frequency shifted by a frequency d1 / 2 from the frequency fp of the pump light 12, which is determined according to a frequency shift d1 between the frequency (fs1-d1) of the signal light Q11 and a target frequency fs1 in a target frequency band corresponding to the signal light Q11. That is, it can be said that the wavelength of the pump light P11 is determined according to a shift between the wavelength of the signal light Q11 and the target wavelength of the signal light Q11.

[0024] The wavelength conversion element 112 receives the pump light P11 and the signal light Q11 and generates the signal light Q12, which is an idler light. The frequency of the signal light Q12 is 2(fp-d1 / 2)-(fs1-d1)=2fp-fs1. The frequency (fp-d1 / 2) of the pump light P11 corresponds to the frequency fa, the frequency (fs1-d1) of the signal light Q11 corresponds to the frequency fb, and the frequency (2fp-fs1) of the signal light Q12 corresponds to the frequency (2fa-fb) of the idler light. The filter 113 receives the pump light P11, the signal light Q11, and the signal light Q12 from the wavelength conversion element 112.

[0025] 2, the filter 113 has a transmission characteristic R11 that transmits a frequency band including the frequency (2fp-fs1) and does not transmit a frequency band including the frequency (fs1-d1) and the frequency (fp-d1 / 2). The filter 113 blocks the pump light P11 and the signal light Q11 and outputs the signal light Q12 to the wavelength conversion element 122.

[0026] The light source 121 generates pump light P12 with a frequency fp. The wavelength conversion element 122 inputs the pump light P12 and the signal light Q12, and generates the signal light Q13, which is an idler light. The frequency of the signal light Q13 is 2fp-(2fp-fs1)=fs1. The frequency fp of the pump light P12 corresponds to the frequency fa, the frequency (2fp-fs1) of the signal light Q12 corresponds to the frequency fb, and the frequency fs1 of the signal light Q13 corresponds to the frequency (2fa-fb) of the idler light. The filter 123 inputs the pump light P12, the signal light Q12, and the signal light Q13 from the wavelength conversion element 122.

[0027] 3, the filter 123 has a transmission characteristic R12 that transmits a frequency band including the frequency fs1 and does not transmit a frequency band including the frequency (2fp-fs1) and the frequency fp. The filter 123 blocks the pump light P12 and the signal light Q12, and outputs the signal light Q13 whose wavelength has been corrected to a target wavelength corresponding to the target frequency fs1.

[0028] As described above, the latter-stage wavelength conversion element 122 receives the pump light and the idler light output from the former-stage wavelength conversion element 112, and outputs the corrected signal light. This makes it possible to correct the wavelength of the signal light.

[0029] In FIG. 2, the pump light P11 has a variable wavelength depending on the frequency shift d1, and the pump light P12 has a fixed wavelength. However, as long as the frequency relationship in which the frequency (fs1-d1) of the signal light Q11 is converted to the target frequency fs1 is maintained, both the pump light P11 and the pump light P12 may have variable wavelengths, or the pump light P11 may have a fixed wavelength and the pump light P12 may have a variable wavelength. For example, in the latter case, if the pump light P11 has a fixed optical frequency fp', the frequency of the pump light P12 may be fp'+d / 2. That is, the frequency of the signal light Q12 is 2fp'-(fs1-d1), and the frequency of the signal light Q13 is 2(fp'+d / 2)-{2fp'-(fs1-d1)}=fs1.

[0030] In the above example, the signal light to be wavelength-corrected is one, but depending on the wavelength relationship between the signal lights to be wavelength-corrected, multiple signal lights may be the target. When the wavelength range of the converted light after wavelength correction has a predetermined relationship, for example, when the signal lights of multiple wavelength grids and pump light of the same frequency (fp-d1 / 2) are input to the wavelength conversion element, the full width at half maximum (3 dB width), 20 dB width, modulation sidebands, or the main lobe of the modulation sideband, or more than half of the main lobe, of the spectrum of the idler light of all grids generated are within the full width at half maximum (3 dB width) or 20 dB width transmitted by the filter 113.

[0031] FIG. 4 is a diagram showing the transmission width of the filter 113 when a plurality of signal lights are to be corrected. The plurality of signal lights Q11 are assumed to be signal lights Q11-1 to Q11-N. Furthermore, the signal light Q13 generated by wavelength-converting the signal light Q11-n (n is an integer between 1 and N) is assumed to be signal light Q13-n. The signal lights Q11-1 to Q11-N are signal lights of each grid, respectively, and the grid spacing is G. The frequency of the signal light Q11-n is fsn-dn. The FWHM of the signal light Q11-n is Mn. Furthermore, the center frequency of the target frequency band of the signal light Q11-n is fscn. The target frequency band is a frequency band corresponding to the target wavelength band. The filter 123 transmits light of a transmission width W centered on the center frequency fscn.

[0032] Let's take the case of n=1 as an example. When the following formula (1) is satisfied, wavelength conversion of the signal light Q11-1 is not necessary, and when (2) or (3) is satisfied, conversion of the signal light Q11-1 is necessary.

[0033] -(W / 2-M1 / 2)≦fsc1-(fs1-d1)≦(W / 2-M1 / 2) …(1)

[0034] fsc1-(fs1-d1)≦-(W / 2-M1 / 2) …(2)

[0035] (W / 2-M1 / 2)≦fsc1-(fs1-d1) …(3)

[0036] The allowable range of the signal light Q13-1 is given by the following formula (4).

[0037] fsc1-(W / 2-M1 / 2)≦fs1≦fsc1+(W / 2-M1 / 2) …(4)

[0038] We will use n=2 and n=3 as examples. The condition for sharing the pump light P11 and the pump light P12 by the target frequency fs2 and the target frequency fs3 is expressed as the following formula (7) from the formulas (5) and (6).

[0039] fsc2-(W / 2-M2 / 2)≦fs2≦fsc2+(W / 2-M2 / 2) …(5)

[0040] fsc3-(W / 2-M3 / 2)≦fs3≦fsc3+(W / 2-M3 / 2) …(6)

[0041] -(W / 2-M3 / 2)≦d2-d3≦(W / 2-M3 / 2) …(7)

[0042] In the adjacent signal lights Q11-1 to Q11-N, if the same condition as in formula (7) is satisfied, the same pump light P11 and pump light P12 can be shared. In the above, the FWHM spectral width is used, but according to Shannon's theorem, 50% or more of the main lobe of the modulation sideband is required. Here, the half-width is used as the width of M, but it may be a width that includes, for example, 80%. This is because in baseband modulation, the signal is cut off to about 70% to 80% by an electrical low-pass filter after photoelectric conversion.

[0043] The above conditions change depending on whether double sideband transmission or single sideband transmission is used. Fig. 5 is a diagram showing the transmission width W that filter 123 transmits in the case of double sideband transmission. In double sideband transmission, normally, both modulation sidebands are allowed to enter as shown in the following equation (8). Here, m ≠ n, and m is an integer between 1 and N. Fig. 5 shows an example where n = 1 and m = 2.

[0044] |dn-dm|+Mn / 2+Mm / 2≦W … (8)

[0045] In order to operate simply without taking into consideration the frequency relationship between a plurality of signal lights, the frequency (fsn-dn) of the input light is transformed by the following equation (9).

[0046] fsn-dn=fscn-(dn+fscn-fsn)=fscn-dn' …(9)

[0047] The frequency (fsm-dm) of the input light is also transformed in the same way as in the above formula (9). When the following formula (10) is satisfied, the pump light P11 and the pump light P12 can be shared.

[0048] |dn'+Mn / 2|≦W / 2,|dm'-Mm / 2|≦W / 2 …(10)

[0049] Fig. 6 is a diagram showing the transmission width W that filter 123 transmits when double-sideband transmission is used and the equalizer on the receiving side is allowed. When the equalizer on the receiving side is allowed, it is sufficient to satisfy the following formula (11) so that one of the modulation sidebands is included. Fig. 6 shows an example where n=1 and m=2.

[0050] |dn-dm|≦W … (11)

[0051] 7 is a diagram showing the transmission width W that filter 123 transmits in the case of single sideband transmission. In single sideband transmission including suppressed carrier single sideband transmission, it is sufficient that the sideband transmitting the signal light is included in the transmission width W. For example, when using sidebands on opposite sides, the outward sideband should be included in the transmission width W as in FIG. 5, and when using sidebands facing each other, the inward sideband should be included in the transmission width W as in FIG. 6. When sidebands on the same side are used, one signal light is outward and the other signal light is inward, it is sufficient to satisfy the following formula (12) or formula (13).

[0052] As shown in Figure 7, when the modulation sideband of M1 is outward and the modulation sideband of M2 is inward, it is sufficient to satisfy formula (12). The modulation sideband of M1 is on the opposite side to the shared carrier. Note that Figure 7 is an example where n = 1 and m = 2.

[0053] |dn-dm|+Mn / 2≦W … (12)

[0054] Conversely, when the modulation sideband of M1 is outward and the modulation sideband of M2 is inward, it is sufficient to satisfy formula (13).

[0055] |dn-dm|+Mm / 2≦W … (13)

[0056] 8 is a diagram showing the transmission width that the filter 123 transmits in the case of suppressed carrier single sideband transmission and not baseband transmission. In the case of SCM or the like and not baseband transmission, as shown in FIG. 8, it is sufficient that the frequency band for transmitting the signal is included in the transmission width W.

[0057] Furthermore, the filter 113 has a transmission characteristic of transmitting a fixed band, but the transmission characteristic may be variable as long as it can pass the signal light Q12 of the idler light generated in the wavelength conversion element 112 and block the signal light Q11 and the pump light P11. Similarly, the filter 123 has a transmission characteristic of transmitting a fixed band, but the transmission characteristic may be variable as long as it can pass the signal light Q13 of the idler light generated in the wavelength conversion element 122 and block the signal light Q12 and the pump light P12. In the case of a transmission characteristic of transmitting a fixed band, the closer the boundary between transmission and blocking is to the pump light, the more the wavelength grid that can be adjusted is increased.

[0058] When an optical amplifier is used in wavelength adapter 100, in order to avoid the effects of amplified spontaneous emission (ASE) noise, it is desirable to use tunable filters that can select the wavelength to be transmitted so that filter 113 transmits only the wavelength of signal light Q12, and filter 123 transmits only the wavelength of signal light Q13.

[0059] When the signal light to be wavelength-modified is a WDM (wavelength division multiplexed) signal and the wavelength adapter 100 outputs the signal light while keeping it wavelength-multiplexed, the filters 113 and 123 may be configured to branch the transmitted wavelengths using an AWG (arrayed-waveguide grating) or the like along a wavelength grid, convert the wavelengths, and then multiplex the converted signals using the AWG or the like. It is also possible to use MZ (Mach-Zehnder) filters, in which the grid interval and the period of the transmitted wavelengths match, as the filters 113 and 123. However, in this case, regardless of whether the wavelength is modified or not, ASE noise that passes through the AWG or MZ filter passes through, and becomes noise for signals that are not to be modified. The above also applies to the following embodiments.

[0060] [Second embodiment] In the first embodiment, two conversion elements, a front wavelength conversion element and a rear wavelength conversion element, are used to correct the wavelength of the signal light of one user. In this embodiment, in order to correct the wavelengths of the signal light of multiple users, the same number of front wavelength conversion elements as the number of users whose wavelengths are to be corrected are provided, and the rear wavelength conversion element is shared by multiple users.

[0061] 9 is a diagram showing an example of the configuration of a wavelength adapter 200 according to the second embodiment. The wavelength adapter 200 has light sources 211-1 to 211-N, 221, wavelength conversion elements 212-1 to 212-N, 222, and filters 213-1 to 213-N, 223. N is an integer equal to or greater than 2. In this embodiment, a case where N=2 will be described as an example.

[0062] Light source 211-n (n is an integer between 1 and N) generates pump light P21-n of degenerate four light waves with variable wavelength. Light source 221 generates pump light P22 of degenerate four light waves with fixed or variable wavelength. Pump light P21-n is a first pump light, and pump light P22 is a second pump light. When generating non-degenerate pump light, light sources 211-1 to 211-N and 221 generate a plurality of pump lights. Note that wavelength adapter 200 may not be provided with light source 211-n and may input pump light P21-n from outside. Also, wavelength adapter 200 may not be provided with light source 221 and may input pump light P22 from outside.

[0063] The wavelength conversion elements 212-1 to 212-N, 222 are nonlinear media similar to the wavelength conversion elements 112, 122 of the first embodiment. The wavelength conversion element 212-n receives the pump light P21-n from the light source 211-n and the signal light Q21-n to be wavelength corrected, and outputs the signal light Q22-n of the idler light. The wavelength conversion element 222 receives the pump light P22 from the light source 221 and the signal lights Q22-1 to Q22-N from the filters 213-1 to 213-N, respectively, and outputs the signal lights Q23-1 to Q23-N. The signal light Q23-n is the idler light generated by the pump light P22 and the signal light Q22-n. The signal light Q23-n is the signal light Q21-n corrected to a target wavelength within the target wavelength band.

[0064] The filter 213-n blocks a wavelength band including the wavelength of the pump light P21-n and the wavelength of the signal light Q21-n, and transmits a wavelength band including the wavelength of the signal light Q22-n. That is, the filter 213-n blocks a frequency band including the frequency of the pump light P21-n and the frequency of the signal light Q21-n, and transmits a frequency band including the frequency of the signal light Q22-n. The filter 223 blocks a wavelength band including the wavelength of the pump light P22 and the wavelengths of the signal lights Q22-1 to Q22-N, and transmits a wavelength band including the wavelengths of the signal lights Q23-1 to Q23-N. That is, the filter 223 blocks a frequency band including the frequency of the pump light P22 and the frequencies of the signal lights Q22-1 to Q22-N, and transmits a frequency band including the frequencies of the signal lights Q23-1 to Q23-N.

[0065] Fig. 10 is a diagram showing the transmission characteristics of filter 213-1, Fig. 11 is a diagram showing the transmission characteristics of filter 213-2, and Fig. 12 is a diagram showing the transmission characteristics of filter 223. The operation of wavelength adapter 200 will be described with reference to Figs. 9 to 12. Wavelength adapter 200 corrects signal light Q21-n, which is experiencing a wavelength shift, to a target wavelength within the target wavelength band. The frequency corresponding to the target wavelength of signal light Q21-n is set as target frequency fsn.

[0066] The wavelength adapter 200 inputs the signal light Q21-n with a frequency (fsn-dn). That is, the signal light Q21-n has a frequency shift of dn. The light source 211-n generates the pump light P21-n with a frequency (fp-dn / 2). That is, the frequency of the pump light P21-n is shifted from the frequency fp of the pump light 22 by a frequency dn / 2 determined according to the shift dn between the frequency (fsn-dn) of the signal light Q21-n and the target frequency fsn in the target frequency band corresponding to the signal light Q21-n. The wavelength conversion element 212-n inputs the pump light P21-n and the signal light Q21-n, and generates the signal light Q22-n of the idler light. The frequency of the signal light Q22-n is 2(fp-dn / 2)-(fsn-dn)=2fp-fsn. The filter 213-n receives the pump light P21-n, the signal light Q21-n, and the signal light Q22-n from the wavelength conversion element 212-n.

[0067] The filter 213-n has a transmission characteristic of transmitting a frequency band including the frequency (2fp-fsn) and not transmitting a frequency band including the frequency (fsn-dn) and the frequency (fp-dn / 2). The filter 213-n blocks the pump light P21-n and the signal light Q21-n and outputs the signal light Q22-n.

[0068] Specifically, the wavelength conversion element 212-1 receives the pump light P21-1 with the frequency (fp-d1 / 2) output by the light source 211-1 and the signal light Q21-1 with the frequency (fs1-d1) to be wavelength corrected, and generates the signal light Q22-1 with the frequency 2fp-fs1, which is an idler light. As shown in Fig. 10, the filter 213-1 has a transmission characteristic R21-1 that transmits an optical frequency band including the frequency (2fp-fs1) and does not transmit an optical frequency band including the frequency (fs1-d1) and the frequency (fp-d1 / 2). The filter 213-1 blocks the pump light P21-1 and the signal light Q21-1, and outputs the signal light Q22-1.

[0069] Similarly, the wavelength conversion element 212-2 receives the pump light P21-2 with the frequency (fp-d2 / 2) output by the light source 211-2 and the signal light Q21-2 with the frequency (fs2-d2) to be wavelength corrected, and generates the signal light Q22-2 with the frequency 2fp-fs2, which is an idler light. As shown in Fig. 11, the filter 213-2 has a transmission characteristic R21-2 that transmits an optical frequency band including the frequency (2fp-fs2) and does not transmit an optical frequency band including the frequency (fs2-d2) and the frequency (fp-d2 / 2). The filter 213-2 blocks the pump light P21-2 and the signal light Q21-2, and outputs the signal light Q22-2.

[0070] The light source 221 generates pump light P22 with a frequency fp. The wavelength conversion element 222 receives the pump light P22 and the signal lights Q22-1 to Q22-N, and generates signal lights Q23-1 to Q23-N of idler lights. The frequency of the signal light Q23-n is 2fp-(2fp-fsn)=fsn. The filter 223 receives the pump light P22, the signal lights Q22-1 to Q22-N, and the signal lights Q23-1 to Q23-N from the wavelength conversion element 222.

[0071] 12, the filter 223 has a transmission characteristic R22 that transmits an optical frequency band including frequencies fs1 to fsN and does not transmit an optical frequency band including frequencies (2fp-fs1) to (2fp-fsN) and frequency fp. The filter 223 blocks the pump light P22 and the signal lights Q22-1 to Q22-N and outputs the signal lights Q23-1 to Q23-N. As a result, the filter 223 outputs the signal light Q23-1 corrected to a target wavelength corresponding to the target frequency fs1 and the signal light Q23-2 corrected to a target wavelength corresponding to the target frequency fs2. The filter 223 may output a signal light in which the signal lights Q23-1 to Q23-N are multiplexed, or may separate and output all or a part of the signal lights Q23-1 to Q23-N.

[0072] As described above, the wavelength adapter 200 can correct the wavelengths of a plurality of signal lights. Moreover, the wavelength adapter 200 of this embodiment includes a wavelength conversion element at the front stage for each wavelength, and a wavelength conversion element at the rear stage is shared by a plurality of wavelengths. Therefore, in the case of two wavelengths, four wavelength conversion elements are required in the first embodiment, but this can be reduced to three in this embodiment. Moreover, in the case of three wavelengths, six wavelength conversion elements are required in the first embodiment, but this can be reduced to four in this embodiment.

[0073] As described above, the wavelength adapter 200 of the present embodiment includes a light source 211-n that generates variable wavelength pump light P21 for each signal light Q21-n to be wavelength corrected, a wavelength conversion element 212-n, and a filter 213-n that blocks the signal light Q21-n and the pump light P21 at the front stage. The wavelength adapter 200 inputs the signal lights Q22-1 to Q22-N of the idler light output from the wavelength conversion elements 212-1 to 212-N at the front stage together with the pump light P22 from the light source 221 again to the wavelength conversion element 222 at the rear stage. The wavelength conversion element 222 outputs the signal lights Q23-1 to Q23-N whose wavelengths have been corrected. The latter filter 223 blocks the idler signal lights Q22-1 to Q22-N output from the former wavelength conversion elements 212-1 to 212-N and the pump light P22, and outputs wavelength-corrected signal lights Q23-1 to Q23-N.

[0074] When the wavelength conversion element in the rear stage is shared as described above, the wavelength region of the target wavelength is set not to overlap with the wavelength of the pump light to be blocked and the wavelength of the idler light generated on the way. The front stage filters 213-1 to 213-N block the signal light Q21-1 to Q21-N to be wavelength corrected and the front stage pump light P21-1 to P21-N, and transmit the idler light. The rear stage filter 223 blocks the signal light Q22-1 to Q22-N, which is the front stage idler light, and the rear stage pump light P22, and transmits the signal light after wavelength correction. The rear stage filter 223 has the transmission characteristics shown in FIG. 4, but the frequency can be adjusted by the front stage pump light P21-1 to P21-N. Therefore, when there is only one signal light to be wavelength corrected in each of the front stage wavelength conversion elements 212-1 to 212-N, there is no restriction on sharing the front stage pump light P21-1 to P21-N. When multiple signal lights Q21-n to be wavelength-adjusted are input to the upstream wavelength conversion element 212-n, the multiple signal lights Q21-n are subject to the same restrictions as when multiple signal lights Q11 to be wavelength-adjusted are input to the wavelength adapter 100 of the first embodiment.

[0075] As long as the loss and gain limitations due to multiplexing are within an acceptable range, the number of multiplexes N can be set to any value. In Fig. 9, the light after wavelength correction follows the wavelength grid, and the wavelength of the pump light is adjusted so that the idler light in the previous stage also follows the wavelength grid. Therefore, during wavelength conversion in the subsequent stage, the idler light can be concentrated using an AWG or the like according to the wavelength grid, so that splitting loss due to couplers during concentration can be avoided.

[0076] [Third embodiment] In the wavelength adapter of this embodiment, a wavelength conversion element at a front stage is shared by multiple users, and the idler light of the signal light of each user is wavelength-separated. The wavelength-separated idler light is input to a wavelength conversion element at a rear stage corresponding to each user.

[0077] 13 is a diagram showing an example of the configuration of wavelength adapter 300 according to the third embodiment. Wavelength adapter 300 has light sources 311, 321-1 to 321-N, wavelength conversion elements 312, 322-1 to 322-N, filters 313, 323-1 to 323-N, and demultiplexer 314. N is an integer equal to or greater than 2. In this embodiment, a case where N=2 will be described as an example.

[0078] The light source 311 generates pump light P31 of degenerate four light waves with a fixed or variable wavelength. The light source 321-n (n is an integer between 1 and N) generates pump light P32-n of degenerate four light waves with a variable wavelength. The pump light P31 is a first pump light, and the pump light P32-n is a second pump light. When generating non-degenerate pump light, the light sources 311, 321-1 to 321-N generate a plurality of pump lights. The wavelength adapter 300 may not include the light source 311 and may input the pump light P31 from outside. The wavelength adapter 300 may not include the light source 321-n and may input the pump light P32-n from outside.

[0079] The wavelength conversion elements 312, 322-1 to 322-N are nonlinear media similar to the wavelength conversion elements 112, 122 of the first embodiment. The wavelength conversion element 312 receives the pump light P31 from the light source 311 and the signal light Q31-1 to Q31-N to be wavelength-adjusted, and outputs the signal light Q32-1 to Q32-N. The signal light Q32-n is an idler light generated based on the pump light P31 and the signal light Q31-n. The wavelength conversion element 322-n receives the pump light P32-n from the light source 321-n and the signal light Q32-n from the demultiplexer 314, and outputs the signal light Q33-n, which is an idler light.

[0080] The filter 313 blocks a wavelength band including the wavelength of the pump light P31 and the wavelengths of the signal lights Q31-1 to Q31-N, and transmits a wavelength band including the wavelengths of the signal lights Q32-1 to Q32-N. That is, the filter 313 blocks a frequency band including the wavelength of the pump light P31 and the frequencies of the signal lights Q31-1 to Q31-N, and transmits a frequency band including the frequencies of the signal lights Q32-1 to Q32-N. The filter 323-n blocks a wavelength band including the wavelength of the pump light P32-n and the wavelength of the signal light Q32-n, and transmits a wavelength band including the wavelength of the signal light Q33-n. That is, the filter 323-n blocks a frequency band including the frequency of the pump light P32-n and the frequency of the signal light Q32-n, and transmits a frequency band including the frequency of the signal light Q33-n.

[0081] The demultiplexer 314 separates the wavelengths of the signal light Q32-1 to Q32-N output from the filter 313. The demultiplexer 314 inputs the signal light Q32-n to a wavelength conversion element 322-n.

[0082] Fig. 14 is a diagram showing the transmission characteristics of filter 313, Fig. 15 is a diagram showing the transmission characteristics of filter 323-1, and Fig. 16 is a diagram showing the transmission characteristics of filter 323-2. The operation of wavelength adapter 300 will be described with reference to Figs. 13 to 16. Wavelength adapter 300 corrects the wavelength of signal light Q31-n, which is shifted in wavelength, to a target wavelength within the target wavelength band. The frequency corresponding to the target wavelength of signal light Q31-n is set as the target frequency fsn.

[0083] The wavelength adapter 300 receives signal light Q31-n with a frequency (fsn-dn). The light source 311 generates pump light P31 with a frequency fp. The wavelength conversion element 312 receives pump light P31 and signal lights Q31-1 to Q31-N, and generates signal lights Q32-1 to Q32-N of idler light. The frequency of the signal light Q32-n is 2fp-(fsn-dn). The filter 313 receives pump light P31 and signal lights Q31-1 to Q31-N, and signal lights Q32-1 to Q32-N from the wavelength conversion element 312.

[0084] 14, the filter 313 has a transmission characteristic R31 that transmits a frequency band including frequencies 2fp-(fs1-d1) to 2fp-(fsN-dN) and does not transmit a frequency band including frequencies fp and frequencies (fs1-d1) to (fsN-dN). The filter 313 blocks the pump light P31 and the signal lights Q31-1 to Q31-N and outputs the signal lights Q32-1 to Q32-N. The demultiplexer 314 wavelength-separates the signal lights Q32-1 to Q32-N output from the filter 313. The demultiplexer 314 inputs the wavelength-separated signal light Q32-n to the wavelength conversion element 322-n.

[0085] The light source 321-n generates pump light P32-n with a frequency (fp-dn / 2). That is, the frequency of the pump light P32-n for converting the signal light Q32-n to the signal light Q33-n is shifted from the frequency fp of the pump light 31 by a frequency dn / 2 determined according to a shift dn between a target frequency fn in a target frequency band corresponding to the signal light Q31-n converted to the signal light Q32-n and the frequency (fsn-dn) of the signal light Q31-n. The wavelength conversion element 322-n inputs the pump light P32-n and the signal light Q32-n, and generates the signal light Q33-n of the idler light. The frequency of the signal light Q33-n is fsn. The filter 323-n inputs the pump light P32-n, the signal light Q32-n, and the signal light Q33-n from the wavelength conversion element 322-n.

[0086] The filter 323-n has a transmission characteristic of transmitting a frequency band including the frequency fsn and not transmitting a frequency band including the frequency (fp-dn / 2) and the frequency 2fp-(fsn-dn). The filter 323-n blocks the pump light P32-n and the signal light Q32-n and outputs the signal light Q33-n.

[0087] Specifically, the wavelength conversion element 322-1 receives the pump light P32-1 with the frequency (fp-d1 / 2) output by the light source 321-1 and the signal light Q32-1 separated by the demultiplexer 314, and generates the signal light Q33-1 with the frequency fs1. As shown in Fig. 15, the filter 323-1 has a transmission characteristic R32-1 that transmits a frequency band including the frequency fs1 and does not transmit a frequency band including the frequencies 2fp-(fs1-d1) and (fp-d1 / 2). The filter 323-1 blocks the pump light P32-1 and the signal light Q32-1, and outputs the signal light Q33-1 corrected to a target wavelength corresponding to the target frequency fs1.

[0088] Similarly, the wavelength conversion element 322-2 receives the pump light P32-2 with the frequency (fp-d2 / 2) output by the light source 321-2 and the signal light Q32-2 separated by the demultiplexer 314, and generates the signal light Q33-2 with the frequency fs2. As shown in FIG. 16, the filter 323-2 has a transmission characteristic R32-2 that transmits a frequency band including the frequency fs2 and does not transmit a frequency band including the frequencies 2fp-(fs2-d2) and (fp-d2 / 2). The filter 323-2 blocks the pump light P32-2 and the signal light Q32-2, and outputs the signal light Q33-2 corrected to a target wavelength corresponding to the target frequency fs2. The wavelength adapter 300 may output the signal lights Q33-1 to Q33-N as they are separated, or may multiplex and output a part or all of the signal lights Q33-1 to Q33-N.

[0089] The wavelength adapter 300 shares the upstream pump light P31-1 to P31-N. The downstream filter 323-n has the transmission characteristics shown in Fig. 4, but since the frequency can be adjusted by the upstream pump light P32-1 to P32-N, there is no restriction such as that of formula (7) for sharing the upstream pump light P31-1 to P31-N. However, there are the following restrictions on the frequency of the signal light Q31-1 to Q31-N to be wavelength corrected.

[0090] FIG. 17 is a diagram showing the transmission width of the demultiplexer 314. Here, the demultiplexer 314 is shown to be demultiplexed by a fixed wavelength filter. FIG. 17 uses frequency on the horizontal axis, but the same relationship can be obtained by using wavelength on the horizontal axis. Here, the frequency of the signal light Q32-(j-1) is lower than the frequency of the signal light Q32-j (j is an integer between 2 and N). In this embodiment, the wavelengths of the signal lights Q32-1 to Q32-N, which are idler lights, need to be separated to a certain extent so that they can be demultiplexed. For example, if the wavelength shift of each of the signal lights Q31-1 to Q31-N is a maximum of ±1 grid, the wavelength of each grid may shift to the adjacent grid. Therefore, if the signal lights have wavelengths of three grids with an interval of two grids between adjacent wavelengths, the wavelength adapter 300 of this embodiment can correct them all at once. The demultiplexer 314 transmits the signal light by frequency regions B1 to BN including a transmission width W corresponding to a wavelength width of three grids, that is, for each of ±1 grids. In FIG. 17, fsci is the center frequency when the wavelength conversion element 312 converts the wavelength of the signal light of the i-th grid (i is an integer of 1 or more) without wavelength shift by the pump light P31. The frequency fsci and the frequency fsc(i+1) are separated by a frequency corresponding to the wavelength width of the grid interval G of one grid. The frequency region Bn is a frequency band through which the signal light Q32-n of the 3n-1-th grid may pass. For example, the demultiplexer 314 outputs the signal light Q32-n that has passed through the wavelength width corresponding to the frequency region Bn to the wavelength conversion element 322-n. FIG. 17 shows that the signal light of the 2nd, 5th, and 8th grids, which have center frequencies fsc2, fsc5, and fsc8 when there is no wavelength shift, can be shared by the demultiplexer 314 of a fixed filter when the signal light is to be wavelength corrected.

[0091] As described above, the adjacent wavelengths of signal light Q31-1 to Q31-N, signal light Q31-(j-1) and signal light Q31-j, are separated by a band or more that may cause signal light Q31-n to deviate from its target wavelength. The demultiplexer 314 demultiplexes the wavelength band including the wavelengths of signal light Q32-1 to Q32-N into bandwidths based on the wavelength difference between the target wavelength of signal light Q31-(j-1) and the target wavelength of signal light Q31-j.

[0092] The demultiplexer 314 only needs to be able to demultiplex each signal light Q32-n. Ideally, if the modulation sideband of the signal light Q32-n is Mn and the modulation sideband of the signal light Q32-m is Mm, the signal light Q32-n and the signal light Q32-m can be separated if their frequencies are Mn / 2+Mm / 2 or more apart. However, in this case, in order to block the influence of side lobes other than the main lobe of the modulation sideband, the signal light Q32-n and the signal light Q32-m are passed through a filter before being input to the wavelength conversion element 312. The signal light Q32-n is passed through a filter with a width of Mn for the main lobe of the signal light Q32-n, and the signal light Q32-m is passed through a filter with a width of Mm for the main lobe of the signal light Q32-m. If an equalizer is used, then in double sideband modulation, 50% of one side of the main lobe, i.e., Mn / 4 and Mm / 4, should be included. Therefore, the frequencies of the signal light Q32-n and the signal light Q32-m can be separated if they are apart by Mn / 4+Mm / 4 or more. In single sideband modulation, however, they should be apart by Mn / 2 or Mm / 2 or more.

[0093] In addition, when signal light Q32-n of multiple wavelengths is input to the downstream wavelength conversion element 322-n, the signal light Q31-1 before being converted into the signal light Q32-n of multiple wavelengths has the same restrictions as in the case where multiple signal lights Q11 to be wavelength-adjusted are input to the wavelength adapter 100 of the first embodiment.

[0094] According to this embodiment, the number of wavelength conversion elements can be reduced compared to the case where a plurality of wavelength adapters of the first embodiment are used.

[0095] [Fourth embodiment] This embodiment is an optical gateway (GW) that uses the wavelength adapter 100 of the first embodiment.

[0096] 18 is a diagram showing a configuration example of the optical GW 401. The optical GW 401 includes an optical SW (switch) 410. The optical SW 410 includes ports 411-1 to 411-K (K is an integer of 2 or more) and ports 412-1 to 412-L (L is an integer of 2 or more). When any of the ports 411-1 to 411-K is not specified, or is collectively referred to as port 411, and when any of the ports 412-1 to 412-L is not specified, or is collectively referred to as port 412. The optical GW 401 outputs the signal light input from the port 411 to the port 412 according to a preset route, and outputs the signal light input from the port 412 to the port 411. Furthermore, the wavelengths corresponding to the ports 411 and 412 are preset.

[0097] Each port 411 and each port 412 inputs an optical signal from the transmission path 450 and / or outputs an optical signal to the transmission path 450. The optical SW 410 is connected to a subscriber device (not shown) or an optical node such as another optical GW via the transmission path 450. The transmission path 450 may connect the ports 411 together, or may connect the ports 412 together. In the optical SW 410 shown in FIG. 18, the ports 411-8 and 411-11 are connected by the transmission path 450, and the ports 411-9 and 411-10 are connected by the transmission path 450.

[0098] The optical SW 410 may be connected to one or more WDM devices 420 via a transmission path 450. The WDM device 420 multiplexes signal lights of different wavelengths output from each of a plurality of ports 412 and outputs the multiplexed signal lights to a multiplexed communication transmission path 451. The optical SW 410 shown in FIG. 18 is connected to two WDM devices 420, a WDM device 420-1 and a WDM device 420-2. The WDM device 420-1 multiplexes the signal lights output from each of the ports 412-1 to 412-3 and outputs the multiplexed signal lights to the multiplexed communication transmission path 451. The WDM device 420-2 multiplexes the signal lights output from each of the ports 412-4 to 412-6 and outputs the multiplexed signal lights to the multiplexed communication transmission path 451.

[0099] Furthermore, the optical SW 410 may be connected to one or more wavelength adapters 460. The wavelength adapter 460 is the wavelength adapter 100 in the first embodiment. The wavelength adapter 460 corrects the wavelength of the signal light output from the port 412 of the optical SW 410, and inputs the corrected signal light to the optical SW 410 from the other port 412. The two wavelength adapters 460 connected to the optical SW 410 are respectively described as wavelength adapters 460-1 and 460-2. The wavelength adapter 460-1 is connected to each of the port 412-8 and the port 412-11 via the transmission path 450, and the wavelength adapter 460-2 is connected to each of the port 412-9 and the port 412-10 via the transmission path 450.

[0100] An example of the operation of the optical GW 401 will be described. The optical SW 410 outputs the signal light input from port 411-1 from port 412-1. The optical SW 410 outputs the signal light input from port 411-2 from port 412-8. The wavelength adapter 460-1 corrects the wavelength of the signal light output from port 412-8 and outputs it. The optical SW 410 inputs the signal light with the corrected wavelength from port 412-11 and outputs it from port 411-11. The port 412-8 of the optical SW 410 inputs the signal light output from port 411-11 and outputs it to port 412-5.

[0101] The optical SW 410 receives the signal light input from port 411-4 and outputs it from port 412-4. The optical SW 410 receives the signal light input from port 411-5 and outputs it from port 412-9. The wavelength adapter 460-2 corrects the wavelength of the signal light output from port 412-9 and outputs it. The optical SW 410 receives the signal light with the corrected wavelength from port 412-10 and outputs it from port 411-10. The optical SW 410 receives the signal light output from port 411-10 from port 412-9 and outputs it to port 412-2.

[0102] The WDM device 420-1 multiplexes the signal light output from the port 412-1 and the wavelength-corrected signal light output from the port 412-2, and outputs the multiplexed signal light to the multiplexed communication transmission path 451. The WDM device 420-2 multiplexes the signal light output from the port 412-4 and the wavelength-corrected signal light output from the port 412-5, and outputs the multiplexed signal light to the multiplexed communication transmission path 451.

[0103] 19 is a diagram showing a configuration of the optical GW 402. The optical GW 402 has two optical SWs 410. The two optical SWs 410 are referred to as optical SWs 410a and 410b, respectively. A port 412 of the optical SW 410a and a port 411 of the optical SW 410b are connected by a transmission path 450.

[0104] A wavelength adapter 461 is provided in one or more transmission paths 450 between the optical SW 410a and the optical SW 410b. The wavelength adapter 461 is the wavelength adapter 100 in the first embodiment. The two wavelength adapters 461 are described as wavelength adapters 461-1 and 461-2, respectively. The wavelength adapter 461-1 is provided in the transmission path 450 between the port 412-8 of the optical SW 410a and the port 411-8 of the optical SW 410b, and the wavelength adapter 461-2 is provided in the transmission path 450 between the port 412-9 of the optical SW 410a and the port 411-9 of the optical SW 410b.

[0105] 19 is connected to two WDM devices 420, a WDM device 420-1 and a WDM device 420-2. The WDM device 420-1 multiplexes the signal lights output from each of the ports 412-1 to 412-3 of the optical SW 410b, and outputs the multiplexed signal lights to a multiplexed communication transmission path 451. The WDM device 420-2 multiplexes the signal lights output from each of the ports 412-4 to 412-6 of the optical SW 410b, and outputs the multiplexed signal lights to a multiplexed communication transmission path 451.

[0106] An example of the operation of the optical GW 402 will be described. The optical SW 410a receives the signal light input from the port 411-1 and outputs it from the port 412-1. The optical SW 410b receives the signal light output from the port 412-1 of the optical SW 410a from the port 411-1 and outputs it from the port 412-1. The optical SW 410a receives the signal light input from the port 411-2 and outputs it from the port 412-8. The wavelength adapter 461-1 corrects the wavelength of the signal light output from the port 412-8 of the optical SW 410a and outputs it. The optical SW 410b receives the signal light with the corrected wavelength from the port 411-8 and outputs it from the port 412-2.

[0107] Furthermore, the optical SW 410a outputs the signal light input from the port 411-4 from the port 412-4. The optical SW 410b inputs the signal light output from the port 412-4 of the optical SW 410a from the port 411-4 and outputs it from the port 412-4. The optical SW 410a outputs the signal light input from the port 411-5 from the port 412-9. The wavelength adapter 461-2 corrects the wavelength of the signal light output from the port 412-9 of the optical SW 410a and outputs it. The optical SW 410b inputs the wavelength-corrected signal light from the port 411-9 and outputs it from the port 412-5.

[0108] The WDM device 420-1 multiplexes the signal light output from port 412-1 of the optical SW 410b and the wavelength-corrected signal light output from port 412-2, and outputs the multiplexed signal light to the multiplexed communication transmission path 451. The WDM device 420-2 multiplexes the signal light output from port 412-4 of the optical SW 410b and the wavelength-corrected signal light output from port 412-5, and outputs the multiplexed signal light to the multiplexed communication transmission path 451.

[0109] [Fifth embodiment] This embodiment is an optical GW that uses the wavelength adapter 200 of the second embodiment or the wavelength adapter 300 of the third embodiment.

[0110] FIG. 20 is a diagram showing a configuration example of the optical GW 403. In the optical GW 403 shown in FIG. 20, the same parts as those of the optical GW 401 according to the fourth embodiment shown in FIG. 18 are given the same reference numerals, and the description thereof will be omitted. The optical GW 403 shown in FIG. 20 differs from the optical GW 401 shown in FIG. 18 in that it includes a wavelength adapter 462 instead of the wavelength adapters 460-1 and 460-2. The wavelength adapter 462 is the wavelength adapter 200 in the second embodiment or the wavelength adapter 300 in the third embodiment. The signal light input side of the wavelength adapter 462 is connected to each of the ports 412-8 and 412-9 by the transmission line 450, and the signal light output side of the wavelength adapter 462 is connected to each of the ports 412-10 and 412-11 by the transmission line 450.

[0111] The optical GW 403 operates in the same manner as the optical GW 401 shown in Fig. 18, except for the following. That is, the wavelength adapter 462 corrects the wavelength of the signal light output from the port 412-8 of the optical SW 410 and outputs it to the transmission path 450 between the port 411-11, and corrects the wavelength of the signal light output from the port 412-9 of the optical SW 410 and outputs it to the transmission path 450 between the port 411-10. In this way, the wavelength adapter 462 corrects the wavelengths of multiple signal lights and outputs the multiple signal lights after the wavelength correction to the transmission paths 450 between different ports 412 according to the wavelengths.

[0112] FIG. 21 is a diagram showing the configuration of the optical GW 404. In the optical GW 404 shown in FIG. 21, the same parts as those of the optical GW 403 shown in FIG. 20 are given the same reference numerals, and the description thereof will be omitted. The optical GW 404 shown in FIG. 21 differs from the optical GW 403 shown in FIG. 20 in that it includes a wavelength adapter 463 instead of the wavelength adapter 462. The wavelength adapter 463 is the wavelength adapter 200 in the second embodiment or the wavelength adapter 300 in the third embodiment. However, the wavelength adapter 463 multiplexes and outputs a plurality of wavelength-corrected signal lights. The signal light input side of the wavelength adapter 463 is connected to each of the port 412-8 and the port 412-9 by the transmission line 450, and the signal light output side is connected to the port 412-10 by the transmission line 450.

[0113] An example of the operation of the optical GW 404 will be described. The optical SW 410 outputs the signal light input from the port 411-1 from the port 412-1, outputs the signal light input from the port 411-4 from the port 412-4, and outputs the signal light input from the port 411-9 from the port 412-5. The optical SW 410 outputs the signal light input from the port 411-2 from the port 412-8, and outputs the signal light input from the port 411-5 from the port 412-9. The wavelength adapter 463 outputs a WDM signal obtained by multiplexing the signal light output from the port 412-8 with the signal light with the wavelength corrected and the signal light output from the port 412-9 with the wavelength corrected. The optical SW 410 inputs the WDM signal from the port 412-10 and outputs it from the port 411-10. The optical SW 410 receives the WDM signal output from the port 411-10 at a port 412-9, and outputs the signal to the port 412-2.

[0114] The WDM device 420-1 multiplexes the signal light output from the port 412-1 and the WDM signal output from the port 412-2, and outputs the multiplexed signal to the multiplexed communication transmission path 451. The WDM device 420-2 multiplexes the signal light output from the port 412-4 and the signal light output from the port 412-5, and outputs the multiplexed signal to the multiplexed communication transmission path 451.

[0115] Fig. 22 is a diagram showing the configuration of the optical GW 405. In the optical GW 405 shown in Fig. 22, the same parts as those of the optical GW 402 according to the fourth embodiment shown in Fig. 19 are given the same reference numerals, and the description thereof will be omitted. The optical GW 405 shown in Fig. 22 differs from the optical GW 402 shown in Fig. 19 in that it includes a wavelength adapter 462 instead of the wavelength adapters 461-1 and 461-2. The signal light input side of the wavelength adapter 462 is connected to each of the ports 412-8 and 412-9 of the optical SW 410a by the transmission line 450, and the signal light output side of the wavelength adapter 462 is connected to each of the ports 411-8 and 411-9 of the optical SW 410b by the transmission line 450.

[0116] The optical GW 405 operates in the same manner as the optical GW 402 shown in FIG. 19, except for the following points. That is, the wavelength adapter 462 corrects the wavelength of the signal light output from the port 412-8 of the optical SW 410a, and outputs the signal light with the corrected wavelength to the transmission line 450 connected to the port 411-8 of the optical SW 410b. The wavelength adapter 462 also corrects the wavelength of the signal light output from the port 412-9 of the optical SW 410a, and outputs the signal light with the corrected wavelength to the transmission line 450 connected to the port 411-9 of the optical SW 410b. In this way, the wavelength adapter 462 corrects the wavelengths of multiple signal lights, and outputs multiple signal lights after the wavelength correction.

[0117] Fig. 23 is a diagram showing the configuration of the optical GW 406. In the optical GW 406 shown in Fig. 23, the same parts as those of the optical GW 405 shown in Fig. 22 are denoted by the same reference numerals, and their description will be omitted. The optical GW 406 shown in Fig. 23 differs from the optical GW 405 shown in Fig. 22 in that a wavelength adapter 463 is further provided between the optical SW 410a and the optical SW 410b. The signal light input side of the wavelength adapter 463 is connected to each of the port 412-11 and the port 412-12 of the optical SW 410a by the transmission line 450, and the signal light output side is connected to the port 411-12 of the optical SW 410b by the transmission line 450.

[0118] The optical GW 406 operates in the same manner as the optical GW 405 shown in FIG. 22, except for the following. That is, the optical SW 410a outputs the signal light input from the port 411-11 from the port 412-11, and outputs the signal light input from the port 411-12 from the port 412-12. The wavelength adapter 463 outputs a WDM signal obtained by multiplexing the signal light output from the port 412-11 with the signal light output from the port 412-12 with the wavelength corrected, to the transmission line 450 connected to the port 411-12 of the optical SW 410b. The optical SW 410b inputs the WDM signal from the port 411-12, and outputs it from the port 412-12 to the transmission line 450.

[0119] Fig. 24 is a diagram showing a configuration of the optical GW 407. The optical GW 407 shown in Fig. 24 includes an optical SW 410 and a wavelength adapter 463. A signal light input side of the wavelength adapter 463 is connected to a transmission path 450 between ports 412-1 and 412-2 of the optical GW 407, and a signal light output side is connected to a multiplex communication transmission path 451.

[0120] An example of the operation of the optical GW 407 will be described. The optical SW 410 outputs the signal light input from the port 411-1 from the port 412-1, and outputs the signal light input from the port 411-2 from the port 412-2. The wavelength adapter 463 outputs to the multiplex communication transmission line 451 a WDM signal obtained by multiplexing the signal light output from the port 412-1 with the signal light output from the port 412-2 with the wavelength corrected.

[0121] FIG. 25 is a diagram showing a configuration of the optical GW 408. The optical GW 408 shown in FIG. 25 includes an optical SW 410, WDM devices 421 and 422, and a wavelength adapter 464. One or more wavelength adapters 464 are provided between the WDM device 421 and the WDM device 422. The WDM device 421 is connected to one or more ports 412 of the optical SW 410 by a transmission line 450. The WDM device 421 demultiplexes the WDM signal output from the port 412 of the optical SW 410, and outputs the demultiplexed signal light. A part of the signal light demultiplexed by the WDM device 421 is directly output to the WDM device 422, and the other signal light is output to the wavelength adapter 464. Note that all of the signal light demultiplexed by the WDM device 421 may be input to any one of the wavelength adapters 464. The wavelength adapter 464 is the wavelength adapter 100 of the first embodiment, the wavelength adapter 200 of the second embodiment, or the wavelength adapter 300 of the third embodiment. The wavelength adapter 464 corrects the wavelength of the signal light demultiplexed by the WDM device 421, and outputs the signal light with the corrected wavelength. The WDM device 422 inputs the signal light directly input from the WDM device 421 and the signal light with the wavelength corrected by the wavelength adapter 464, multiplexes these input signal lights, and outputs the multiplexed communication transmission path 451.

[0122] As described above, the optical GW corrects the wavelength of only the signal light to be wavelength-modified by the wavelength adapter, and the signal light other than the target of wavelength modification is bypassed so as not to pass through the wavelength adapter and passes through the short-circuited path. Alternatively, the optical GW may correct only the wavelength of the signal light to be wavelength-modified by the wavelength adapter, and convert the wavelength of the signal light other than the target of wavelength modification by the wavelength adapter, but may return it to the original wavelength. In this case, in an example using degenerate four-wave mixing, the frequency of the pump light is fp in both the front and rear stages, and d / 2=0.

[0123] When outputting each corrected signal light, as in the wavelength adapter 462, an AWG or the like is used. When multiplexing and outputting the corrected signal light, as in the wavelength adapter 463, in order to remove ASE, the signal light is demultiplexed by the AWG and then multiplexed by the AWG, or an MZ filter that transmits the grid at intervals is used. When using an MZ filter, it is preferable to use one with a ring resonator that has a flat transmission band.

[0124] [Sixth embodiment] In the sixth embodiment, pump light is utilized in the wavelength adapters of the first to third embodiments. To utilize this pump light, the wavelength adapter separates the pump light from the signal light before wavelength correction and from the idler light generated in between. Therefore, a filter with multiple ports is used as the filter of the wavelength adapters of the first to third embodiments. The filter outputs light of a wavelength to be transmitted and light of a wavelength to be blocked to different ports, and extracts only the pump light from the output of the light of the wavelength to be blocked. The extracted pump light is then utilized in the configuration of another wavelength adapter.

[0125] Specifically, filter 123 of wavelength adapter 100 outputs the blocked pump light P12 of frequency fp to another wavelength adapter 100, 200, or 300. Also, filter 223 of wavelength adapter 200 outputs the blocked pump light P22 of frequency fp to another wavelength adapter 100, 200, or 300. Also, filter 313 of wavelength adapter 300 outputs the blocked pump light P31 of frequency fp to another wavelength adapter 100, 200, or 300. The pump light P12 output from wavelength adapter 100, the pump light P22 output from wavelength adapter 200, and the pump light P31 output from wavelength adapter 300 are collectively referred to as pump light P.

[0126] The wavelength adapter 100 to which the pump light P is input does not include a light source 121, and uses the pump light P as pump light P12. The filter 123 of the wavelength adapter 100 to which the pump light P is input may output the blocked pump light P to another wavelength adapter 100, 200, or 300. The wavelength adapter 200 to which the pump light P is input may not include a light source 221, and uses the pump light P as pump light P22. The filter 223 of the wavelength adapter 200 to which the pump light P is input may output the blocked pump light P to another wavelength adapter 100, 200, or 300. Alternatively, the wavelength adapter 300 to which the pump light P is input may not include a light source 311, and uses the pump light P as pump light P31. The filter 313 of the wavelength adapter 300 to which the pump light P is input may output the blocked pump light P to another wavelength adapter 100, 200, or 300.

[0127] Furthermore, for signal light whose wavelength region of the converted light after wavelength correction has a predetermined relationship, pump light of frequency (fp-dn / 2) may be shared by multiple wavelength adapters 100, 200, or 300. The predetermined relationship is, for example, signal light whose 3 dB bandwidth falls within the 3 dB band of the grid transmission. Specifically, the filter 113 of the wavelength adapter 100 outputs the blocked pump light P11 to another wavelength adapter 100, 200, or 300. The filter 113 outputs the pump light P11 to the wavelength adapter 100, 200, or 300 that outputs the signal light Q13, Q23-h, or Q33-h whose wavelength has a predetermined relationship with the wavelength of the signal light P13 (h is an integer between 1 and N). Furthermore, the filter 213-n of the wavelength adapter 200 outputs the blocked pump light P21-n to another wavelength adapter 100, 200, or 300. The target to which the filter 213-n outputs the pump light P21-n is the wavelength adapter 100, 200, or 300 that outputs the signal light Q13, Q23-h, or Q33-h having a wavelength that has a predetermined relationship with the wavelength of the signal light P23-n. The filter 323-n of the wavelength adapter 300 outputs the blocked pump light P32-n to another wavelength adapter 100, 200, or 300. The filter 323-n is the wavelength adapter 100, 200, or 300 that outputs the signal light Q13, Q23-h, or Q33-h having a wavelength that has a predetermined relationship with the wavelength of the signal light 33-n to be transmitted. The pump light P11 output from the wavelength adapter 100, the pump light P21-n output from the wavelength adapter 200, and the pump light P32-n output from the wavelength adapter 300 are collectively referred to as pump light P'.

[0128] The wavelength adapter 100 to which the pump light P' has been input does not include a light source 111, and uses the pump light P' as pump light P11. The filter 113 of the wavelength adapter 100 to which the pump light P has been input may output the blocked pump light P' to another wavelength adapter 100, 200, or 300. The wavelength adapter 200 to which the pump light P' has been input may not include a light source 211-h, and uses the pump light P' as pump light P21-h. The filter 213-h of the wavelength adapter 200 to which the pump light P' has been input may output the blocked pump light P' to another wavelength adapter 100, 200, or 300. Alternatively, the wavelength adapter 300 to which the pump light P' has been input may not include a light source 321-h, and uses the pump light P' as pump light P32-h. The filter 323-h of the wavelength adapter 300 to which the pump light P' has been input may output the blocked pump light P' to another wavelength adapter 100, 200, or 300. However, the number of times that the pump light can be utilized is limited to the number of times that the intensity of the corrected signal light becomes an acceptable intensity.

[0129] FIG. 26 is a diagram showing a configuration example of a wavelength adapter 800. The wavelength adapter 800 corresponds to a configuration in which N (N is an integer equal to or larger than N) wavelength adapters 100 are provided. FIG. 26 shows an example in which N=5. The wavelength adapter 800 corrects the signal light Q81-n in which a wavelength shift occurs to a target frequency fsn corresponding to a target wavelength within a target wavelength band (n is an integer equal to or larger than 1 and equal to or smaller than N). Note that all or some of the frequencies fs1 to fsN may be the same frequency. The wavelength adapter 800 includes light sources 811-1 to 811-N, 821, wavelength conversion elements 812-1 to 812-N, 822-1 to 822-N, and filters 813-1 to 813-N, 823-1 to 823-N.

[0130] The light source 811-n, the wavelength conversion element 812-n, the filter 813-n, and the light source 821 have the same functions as the light source 111, the wavelength conversion element 112, the filter 113, and the light source 121 of the first embodiment, respectively.

[0131] The wavelength conversion element 822-n has the same function as the wavelength conversion element 122 of the first embodiment. However, the wavelength conversion element 822-j (j is an integer between 2 and N) inputs the pump light output by the filter 823-(j-1). The filter 823-n has a plurality of ports. The filter 823-n blocks a wavelength band including the wavelength of the pump light output by the wavelength conversion element 822-n and the wavelength of the signal light of the idler light, and transmits a wavelength band including the wavelength of the signal light after the correction. The filter 823-n outputs the signal light after the correction from a port, and outputs the pump light of the blocked light from another port and inputs it to the wavelength conversion element 822-(n+1). However, the filter 823-N does not have to output the pump light.

[0132] The transmission characteristics of filter 813-1 are similar to the transmission characteristics of filter 213-1 shown in Fig. 11, and the transmission characteristics of filter 813-2 are similar to the transmission characteristics of filter 213-2 shown in Fig. 12. Moreover, the transmission characteristics of filter 823-1 are similar to the transmission characteristics of filter 123 shown in Fig. 3. Pump light of frequency fp that is not transmitted by filter 823-1 is utilized by filters 823-2 to 823-N.

[0133] The operation of the wavelength adapter 800 will be described. The wavelength adapter 800 corrects the wavelength of the signal light Q81-n, which is experiencing a wavelength shift, to a target wavelength within the target wavelength band. The frequency corresponding to the target wavelength within the target wavelength band of the signal light Q81-n is set to the target frequency fsn.

[0134] The wavelength adapter 800 inputs the signal light Q81-n of the frequency (fsn-dn). The light source 811-n generates the pump light P81-n of the frequency (fp-dn / 2). The pump light P81-n is the first pump light. The wavelength conversion element 812-n inputs the pump light P81-n and the signal light Q81-n, and generates the signal light Q82-n of the frequency (2fp-fsn) which is an idler light. The filter 813-n inputs the pump light P81-n and the signal light Q81-n, and the signal light Q82-n from the wavelength conversion element 812-n. The filter 813-n blocks the pump light P81-n and the signal light Q81-n, and outputs the signal light Q82-n to the wavelength conversion element 822-n.

[0135] The light source 821 generates pump light P82 of frequency fp. The pump light P82 is a second pump light. The wavelength conversion element 822-1 inputs the pump light P82 from the light source 821, inputs the signal light Q82-1 from the filter 813-1, and generates signal light Q83-1 of frequency fs1, which is an idler light. The filter 823-1 inputs the pump light P82, the signal light Q82-1, and the signal light Q83-1 from the wavelength conversion element 822-1. The filter 823-1 outputs the signal light Q83-1 to the outside, and outputs the pump light P82 to the wavelength conversion element 822-2.

[0136] The wavelength conversion element 822-j receives the pump light P82 from the filter 813-(j-1), receives the signal light Q82-j from the filter 813-j, and generates the signal light Q83-j of frequency fsj, which is an idler light. The filter 823-j receives the pump light P82, the signal light Q82-j, and the signal light Q83-j from the wavelength conversion element 822-j. The filter 823-j outputs the signal light Q83-j to the outside, and outputs the pump light P82 to the wavelength conversion element 822-(j+1).

[0137] As described above, the wavelength adapter 800 can correct the wavelengths of the wavelength-shifted signal lights P81-1 to P81-N. As described above, the pump light P82 with frequency fp generated by the light source 821 can be utilized as is in the downstream multiple filters 823-1 to 823-N. In addition, the pump light with frequency (fp-dn / 2) generated by the light source 811-n may be shared with signal light having a wavelength region in a predetermined relationship with the converted light after wavelength correction, for example, a signal light whose 3 dB bandwidth falls within the 3 dB band of the grid transmission.

[0138] In the above, an example was shown in which the pump light P12 of frequency fp of wavelength adapter 100 is shared, but similarly, the pump light P22 of frequency fp of wavelength adapter 200 may be shared, and the pump light P31 of frequency fp of wavelength adapter 300 may be shared. The conditions for sharing are the same as those in the first embodiment, that is, the following equation (13). Here, n and n' are integers between 1 and N, and Mn, which is the FWHM of signal light Q81-n, and Mn', which is the FWHM of signal light Q81-n', are both set to M.

[0139] -(W / 2-M / 2)≦dn-dn'≦(W / 2-M / 2) …(13)

[0140] Note that the frequency fp is not common to all wavelength adapters, but may be treated as a different frequency for each wavelength adapter, and pump light of frequency fp used in one wavelength adapter may be used as pump light of frequency (fp-dn / 2) in another wavelength adapter. In this case, pump light P12 output by filter 123 of wavelength adapter 100, pump light P22 output by filter 223 of wavelength adapter 200, or pump light P31 output by filter 313 of wavelength adapter 300 may be shared as pump light P11 of wavelength adapter 100, pump light P21-n of wavelength adapter 200, and pump light P32-n of wavelength adapter 300. Furthermore, pump light P11 output by filter 113 of wavelength adapter 100, pump light P21-n output by filter 213-n of wavelength adapter 200, and pump light P32-n output by filter 323-n of wavelength adapter 300 may be shared as pump light P12 of wavelength adapter 100, pump light P22 of wavelength adapter 200, or pump light P31 of wavelength adapter 300. The condition for sharing is that the corrected signal light satisfies a predetermined upper limit.

[0141] According to the above-described embodiment, the wavelength adapter has a first conversion unit, a first filter, a second conversion unit, and a second filter. The wavelength adapter corresponds to, for example, the wavelength adapters 100, 200, 300, and 800 of the embodiments. The first conversion unit corresponds to, for example, the wavelength conversion elements 112, 212-1 to 212-N, 312, and 812-1 to 812-N of the embodiments. The first filter corresponds to, for example, the filters 113, 213-1 to 213-N, 313, and 813-1 to 813-N of the embodiments. The second conversion unit corresponds to, for example, the wavelength conversion elements 122, 222, 322-1 to 322-N, and 822-1 to 822-N of the embodiments. The second filter corresponds to, for example, the filters 123, 223, 323-1 to 323-N, and 823-1 to 823-N in the embodiment.

[0142] The first filter converts the first signal light by the first pump light into second signal light of a wavelength not included in the target wavelength band while maintaining the phase relationship of the first signal light. The first filter blocks the first signal light and the first pump light, and transmits the second signal light. The second conversion unit converts the second signal light transmitted by the first filter into third signal light of a wavelength within the target wavelength band by the second pump light, while maintaining the phase relationship of the second signal light. The second filter blocks the second signal light and the second pump light, and transmits the third signal light.

[0143] The wavelength adapter may include a set of a first conversion unit and a first filter corresponding to each of a plurality of first signal lights having different wavelengths. In this case, the second conversion unit converts each of the plurality of second signal lights transmitted by each of the plurality of first filters into a third signal light having a wavelength in a different target wavelength band by the second pump light while maintaining the phase relationship of the second signal light. The second filter blocks the plurality of second signal lights and the plurality of second pump lights and transmits the plurality of third signal lights. Note that the frequency of the first pump light for converting the first signal light into the second signal light is shifted from the frequency of the second pump light by a frequency corresponding to the shift between the frequency of the first signal light and the frequency corresponding to the target wavelength in the target frequency band corresponding to the first signal light.

[0144] The first conversion unit may convert each of the multiple first signal lights having different wavelengths into a second signal light having a different wavelength and not included in any target wavelength band corresponding to the first signal light, by using the first pump light while maintaining the phase relationship of the first signal light. The first filter blocks the multiple first signal lights and the first pump light, and transmits the multiple second signal lights. The wavelength adapter includes a demultiplexer that separates the multiple second signal lights transmitted by the first filter by wavelength, and a set of a second conversion unit and a second filter for each of the multiple second signal lights demultiplexed by the demultiplexer. Note that the frequency of the second pump light for converting the second signal light into the third signal light is shifted from the frequency of the first pump light by a frequency corresponding to the shift between the frequency corresponding to the target wavelength in the target wavelength band corresponding to the first signal light converted into the second signal light and the wavelength of the first signal light. The target wavelengths of the different first signal lights are separated by a wavelength width or more by which the wavelength of the first signal light may deviate from the target wavelength of the first signal light. The demultiplexer demultiplexes the first signal lights for each bandwidth based on the wavelength difference between the target wavelengths of the different first signal lights.

[0145] The first conversion unit may have a plurality of first ports and may input the first signal light from a first optical switch that outputs the signal light input from any one of the first ports from another first port. The second filter may have a plurality of second ports and may output the third signal light to a second optical switch that outputs the signal light input from any one of the second ports from another second port, or may output the third signal light to the first optical switch.

[0146] The wavelength adapter may input the multiple first signal lights from multiple different first ports of a first optical switch having multiple first ports and outputting the signal light input from any one of the first ports from another first port. The wavelength adapter may output the multiple third signal lights to the same or different second ports of a second optical switch having multiple second ports and outputting the signal light input from any one of the second ports from another second port, or to the same or different first ports of the first optical switch.

[0147] The first filter may output the first pump light to another wavelength adapter. The first pump light output from the first filter is used as the first pump light or the second pump light in the other wavelength adapter. The first filter may also output the first pump light to another wavelength adapter that outputs a third signal light having a wavelength that has a predetermined relationship with the wavelength of a third signal light generated based on the first signal light. The first pump light output from the first filter is used as the first pump light or the second pump light in the other wavelength adapter.

[0148] The second filter may output the second pump light to another wavelength adapter. The first pump light output from the second filter is used as the first pump light or the second pump light in the other wavelength adapter. The second filter may also output the second pump light to another wavelength adapter that outputs a third signal light having a wavelength that has a predetermined relationship with the wavelength of the third signal light to be transmitted. The first pump light output from the second filter is used as the first pump light or the second pump light in the other wavelength adapter.

[0149] In the above description, the operation of converting the wavelength has been described, but the processing of this embodiment may be performed under control of the optical GW, its network, or a controller related to either of them. The processing of this embodiment may also be performed under control of a functional unit or monitor that detects a wavelength shift. The functional unit that performs the processing of this embodiment may snoop instructions to the transmitter, and use the observed values ​​of the functional unit or monitor that observes the wavelength of the signal light to determine the shift and perform the above-mentioned processing.

[0150] In this embodiment, the input wavelength is converted to a predetermined wavelength by a wavelength adapter provided at the entrance of the network. However, the received wavelength may be converted back to the input wavelength by a wavelength adapter provided at the exit of the network. In this case, information related to the wavelength at the time of input is transmitted to the exit side. The information related to the wavelength at the time of input is, for example, at least one of the central wavelength of the signal light, the intermediate value of the wavelength width of the signal light, the maximum value of the wavelength spectrum of the signal light, the wavelength of each pump light used for conversion, the value of the wavelength of the other pump light when the wavelength of one pump light is a predetermined value, the wavelength difference between the pump light of the predetermined value and the other pump light, and a value for restoring the signal light on the output side. The value for restoring the signal light on the output side is, for example, the value of the wavelength of the pump light to be set on the exit side. When the processing of this embodiment is controlled by a controller or other functional units, the controller may transmit these values. Also, the functional unit performing the processing of this embodiment may transmit these values ​​to the functional unit on the exit side. This is preferable when the functional unit performing the processing of this embodiment makes the determination. In this way, by returning the signal light to the original wavelength, it is possible to provide relief even when the wavelength to be received at the receiving side of the user is shifted, just as it is at the transmitting side.

[0151] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0152] 100, 200, 300, 460-1, 460-2, 461-1, 461-2, 462, 463, 464, 800…wavelength adapters, 111, 121, 211-1, 211-2, 221, 311, 321-1, 321-2, 811-1~811-5, 821...Light source, 112, 122, 212-1, 212-2, 222, 312, 322-1, 322-2, 812-1 to 812-5, 822-1 to 822-5...wavelength conversion elements, 113, 123, 213-1, 213-2, 223, 313, 323-1, 323-2, 813-1~813-5, 823-1~823-5…filters, 314…Brancher, 401, 402, 403, 404, 405, 406, 407, 408...Hikari GW, 410, 410a, 410b…optical SW, 411-1~411-12, 412-1~412-12…Ports, 420-1, 420-2, 421, 422...WDM equipment, 450…Transmission line, 451...Multiple communication transmission lines

Claims

1. a first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; A wavelength adapter comprising: a set of the first conversion unit and the first filter corresponding to each of a plurality of first signal lights having different wavelengths; the second conversion unit converts each of the second signal lights transmitted through each of the first filters into the third signal lights having a different wavelength within the target wavelength band by the second pump light while maintaining a phase relationship of the second signal lights; the second filter blocks the plurality of second signal lights and the plurality of second pump lights and transmits the plurality of third signal lights; Wavelength adapter.

2. the frequency of the first pump light for converting the first signal light into the second signal light is shifted from the frequency of the second pump light by a frequency corresponding to a shift between the frequency of the first signal light and a frequency corresponding to a target wavelength within the target wavelength band of the first signal light; 2. The wavelength adapter of claim 1.

3. A first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; A wavelength adapter comprising: the first conversion unit converts each of the plurality of first signal lights having different wavelengths into the second signal light having a different wavelength and not included in the target wavelength band corresponding to any of the first signal lights by the first pump light while maintaining a phase relationship of the first signal lights; the first filter blocks the first signal light beams and the first pump light beam and transmits the second signal light beams; The wavelength adapter comprises: a demultiplexer that separates the plurality of second signal lights transmitted through the first filter according to wavelength; a pair of the second conversion unit and the second filter for each of the plurality of second signal lights demultiplexed by the demultiplexer; Wavelength adapter.

4. a frequency of the second pump light for converting the second signal light into the third signal light is shifted from the frequency of the first pump light by a frequency corresponding to a target wavelength within the target wavelength band of the first signal light converted into the second signal light, and a frequency corresponding to the frequency of the first signal light.

4. The wavelength adapter of claim 3.

5. the target wavelengths of the different first signal lights are separated by a wavelength width or more by which the wavelength of the first signal light may deviate from the target wavelength of the first signal light, The demultiplexer demultiplexes the first signal light for each bandwidth based on a wavelength difference between the target wavelengths of the different first signal light.

5. The wavelength adapter of claim 4.

6. A first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; Equipped with the first conversion unit has a plurality of first ports, and receives the first signal light from a first optical switch that outputs the signal light input from any one of the first ports from another of the first ports; the second filter has a plurality of second ports, and outputs the third signal light to a second optical switch that outputs the signal light input from any one of the second ports from another of the second ports, or to the first optical switch. Wavelength adapter.

7. the first signal lights are output from different first ports of a first optical switch having a plurality of first ports and configured to output the signal light input from any one of the first ports from another of the first ports; the plurality of third signal lights have a plurality of second ports, and are output to the same or different second ports of a second optical switch that outputs the signal light input from any of the second ports from another of the second ports, or to the same or different first ports of the first optical switch; A wavelength adapter according to any one of claims 1 to 5.

8. A first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; A wavelength adapter comprising: the first filter outputs the first pump light to another wavelength adapter; The first pump light output from the first filter is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength adapter.

9. A first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; A wavelength adapter comprising: the first filter outputs the first pump light to another wavelength adapter that outputs a third signal light having a wavelength that is in a predetermined relationship with the wavelength of the third signal light generated based on the first signal light; The first pump light output from the first filter is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength adapter.

10. A first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light; A wavelength adapter comprising: the second filter outputs the second pump light to another wavelength adapter; The second pump light output from the second filter is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength adapter.

11. the second filter outputs the second pump light to another wavelength adapter that outputs a third signal light having a wavelength that has a predetermined relationship with the wavelength of the third signal light to be transmitted; The second pump light output from the second filter is used as the first pump light or the second pump light in the other wavelength adapter.

5. The wavelength adapter according to claim 3 or 4.

12. a first conversion unit that converts a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filter that blocks the first signal light and the first pump light and transmits the second signal light based on a frequency; a second conversion unit that converts the second signal light transmitted by the first filter into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filter that blocks the second signal light and the second pump light and transmits the third signal light based on a frequency; Equipped with The frequency of the signal light which is the first signal light, the second signal light, or the third signal light is set to the median of the full width at half maximum of the spectrum of the signal light, the median of the 20 dB width of the spectrum of the signal light, or a value at which the spectrum peak of the signal light is maximum, or the wavelength of the signal light is set to a value at which the modulation sideband or the main lobe of the modulation sideband included in the wavelength width allowed for the signal light is most abundant. Wavelength adapter.

13. a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having the first conversion step and the first filtering step are performed for each of the plurality of first signal lights having different wavelengths; In the second conversion step, each of the plurality of second signal lights transmitted in the first filtering step executed for each of the plurality of first signal lights is converted into the third signal light having a different wavelength within the target wavelength band by the second pump light while maintaining a phase relationship of the second signal light, In the second filtering step, the second signal light beams and the second pump light beams are blocked, and the third signal light beams are transmitted. Wavelength correction method.

14. a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having In the first conversion step, the first signal lights having different wavelengths are converted into the second signal lights having different wavelengths and not included in the target wavelength band corresponding to any of the first signal lights by the first pump light while maintaining a phase relationship of the first signal lights, In the first filtering step, a plurality of the first signal lights and the first pump light are blocked, and a plurality of the second signal lights are transmitted; a demultiplexing step of separating the plurality of second signal lights transmitted in the first filtering step by wavelength, the second conversion step and the second filtering step are performed on each of the plurality of second signal lights demultiplexed by the demultiplexing step; Wavelength correction method.

15. a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having In the first conversion step, the first signal light is input from a first optical switch having a plurality of first ports and configured to output the signal light input from any one of the first ports from another of the first ports; In the second filtering step, the third signal light is output to a second optical switch having a plurality of second ports and outputting the signal light input from any one of the second ports from another of the second ports, or to the first optical switch. Wavelength correction method.

16. A wavelength modification method performed by a wavelength adapter, comprising: a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having In the first filtering step, the first pump light is output to another wavelength adapter; The first pump light output in the first filtering step is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength correction method.

17. A wavelength modification method performed by a wavelength adapter, comprising: a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having In the first filtering step, the first pump light is output to another wavelength adapter that outputs a third signal light having a wavelength that is in a predetermined relationship with a wavelength of the third signal light generated based on the first signal light; The first pump light output in the first filtering step is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength correction method.

18. A wavelength modification method performed by a wavelength adapter, comprising: a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light; having In the second filtering step, the second pump light is output to another wavelength adapter; The second pump light output in the second filtering step is used as the first pump light or the second pump light in the other wavelength adapter. Wavelength correction method.

19. a first conversion step of converting a first signal light into a second signal light having a wavelength not included in a target wavelength band by a first pump light while maintaining a phase relationship of the first signal light; a first filtering step of blocking the first signal light and the first pump light and transmitting the second signal light based on a frequency; a second conversion step of converting the second signal light transmitted in the first filtering step into a third signal light having a wavelength within the target wavelength band by using a second pump light while maintaining a phase relationship of the second signal light; a second filtering step of blocking the second signal light and the second pump light and transmitting the third signal light based on a frequency; having The frequency of the signal light which is the first signal light, the second signal light, or the third signal light is set to the median of the full width at half maximum of the spectrum of the signal light, the median of the 20 dB width of the spectrum of the signal light, or a value at which the spectrum peak of the signal light is maximum, or the wavelength of the signal light is set to a value at which the modulation sideband or the main lobe of the modulation sideband included in the wavelength width allowed for the signal light is most abundant. Wavelength correction method.

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