JP2008109248A - Wavelength selection switch circuit and wavelength path switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength selection switch circuit having a wide bandwidth, and to provide a wavelength path switching device employing the wavelength selection switch circuit. <P>SOLUTION: The wavelength selection switch circuit comprises a wavelength interleave means for separating the signal light of odd channel of wavelength multiplex signal light and the signal light of even channel, and a wavelength selection means for even channel. For example, the wavelength interleave means is provided between the wavelength separation means and the wavelength selection means. Alternatively, the wavelength interleave means is provided in the prestage of the wavelength separation means. The wavelength interleave means can be implemented using a periodic filter which repeats reflection and transmission every optical frequency period Δf. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength selective switch circuit used in an optical cross connect or an optical network.

  Research is being conducted on the use of an optical cross connect (OXC) for switching wavelength paths and wavelength group paths in an optical network. One of optical devices for realizing OXC is a wavelength selective switch (WSS) circuit.

  17 and 18 are schematic views of the configuration of a conventional wavelength selective switch. FIG. 17 shows a 1 (input port): 2 (output port) type for easy understanding. Here, reference numeral 101 denotes wavelength separation means, reference numeral 102 denotes wavelength multiplexing means, and reference numeral 103 denotes wavelength selection means. Specifically, a diffraction grating or an arrayed waveguide grating is specifically used as the wavelength separation and multiplexing means, and specifically, a MEMS (Micro Electro Mechanical Systems) mirror is mainly used as the wavelength selection means (see, for example, Non-Patent Document 1).

  The input signal light is wavelength-multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights (optical frequencies f0 ± k · Δf, k is an integer of 0 or more) arranged at an optical frequency interval Δf with the optical frequency f0 as the center. is there. The wavelength-multiplexed signal light is input from the input port, and is separated into signal lights having different wavelengths by the wavelength separation means 101. Thereafter, signal light having a desired wavelength is selected by the wavelength selecting means 103 and output to a desired output port via the wavelength multiplexing means 102. In FIG. 17 and FIG. 18, there are two output ports. Actually, a WSS having three or more ports is also possible. Further, the wavelength separation means 101 and the wavelength multiplexing means 102 can be shared by a single diffraction grating.

  In recent years, research and development of dense wavelength division multiplexing (DWDM) using a narrowed channel interval and a phase modulation method have been actively promoted with the aim of further improving the frequency efficiency of an optical network. For example, wavelength-multiplexed signal light of an OOK, DPSK or DQPSK signal with a bit rate of 10 Gbit / s at a channel interval of 50 GHz, wavelength-multiplexed signal light of an OOK, DPSK or DQPSK signal with a bit rate of 40 Gbit / s at a channel interval of 100 GHz, etc. There are reports on optical transmission and optical networks handled.

  Such a high-density optical network requires a wavelength selective switch circuit having a channel interval corresponding to a high-density WDM signal and a wider transmission bandwidth than the bandwidth of signal light. Also, in an optical network in which optical cross-connects composed of this wavelength selective switch circuit are connected in multiple stages, the optical frequency bandwidth becomes narrower due to the multi-stage filter effect, so it is mounted on each optical cross-connect. The optical frequency bandwidth of the wavelength selective switch circuit must be sufficiently wide.

J. et al. Tsai et al, “A high port-count wavelength-selective switch using a large scan-angle, high fill-factor, two-axis MEMS scannerEarth. Lett. , Vol. 18, no. 13, pp. 1439-1442, 2006 S. Cao et al. "Interleaver Technology: Comparisons and Applications Requirements", IEEE J. Lightwave Technol. , Vol. 22, no. 1, pp. 281-289, 2004

  However, the conventional wavelength selective switch circuit has a drawback that a sufficiently wide optical frequency bandwidth cannot be realized. Currently, the transmission bandwidth of the wavelength selective switch circuit for 50 GHz channel spacing that can be realized is about 30 GHz. Further, the bandwidth having a flat chromatic dispersion characteristic within the transmission bandwidth is further narrowed to about 20 GHz.

  FIG. 19 shows the relationship between the number of wavelength selective switch circuit stages (horizontal axis) and the Q value penalty (vertical axis) when 10 Gbit / s RZ-DPSK signals are transmitted in cascade. As can be seen from FIG. 19, assuming that the allowable Q value penalty is 1 dB, when the bandwidth of the wavelength selective switch circuit is 21 GHz, only up to about seven stages can be connected in cascade.

  The reason why the bandwidth of the conventional wavelength selective switch circuit is reduced will be described with reference to FIG. The signal light of each channel spatially separated by the wavelength separation means is guided to each mirror of a mirror array (MEMS or liquid crystal) which is a wavelength selection means. The reflection angle of each mirror is a mechanism that can be electrically changed independently. By controlling the reflection angle, signal light of a desired channel can be selected and output to a desired output port.

  However, in the conventional wavelength selective switch circuit, as shown in FIG. 20, in order to change the angle while supporting the mirror portion, a non-reflective portion (dead zone) is required between the mirrors. Due to the influence of this dead zone, a wavelength component that cannot be reflected by the signal light is generated, and the band of the wavelength selective switch circuit is narrowed. In addition, a large ripple has occurred in the wavelength dispersion characteristic of the reflected light due to the influence of the dead zone.

  Thus, the conventional wavelength selective switch circuit has a problem that the bandwidth is narrow. For this reason, when used in an optical cross-connect, the number of multi-stage connections is small, so that it was impossible to apply to a large-scale optical network.

  The present invention has been made under such a background, and an object thereof is to provide a wavelength selective switch circuit having a wide bandwidth and a wavelength path switching device using the wavelength selective switch circuit.

  The present invention inputs an input for wavelength-multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights (optical frequencies f0 ± k · Δf, k is an integer of 0 or more) arranged at an optical frequency interval Δf with the optical frequency f0 as the center. Port, wavelength separation means for separating wavelength multiplexed signal light input from this input port into signal lights having different wavelengths, and selecting signal light of a desired wavelength from the signal light wavelength-separated by this wavelength separation means This is a wavelength selective switch circuit comprising wavelength selection means for outputting to a desired output port and wavelength multiplexing means for multiplexing the signal light selected by the wavelength selection means.

  The feature of the present invention is that the wavelength-multiplexed signal light of the odd-numbered channel light (optical frequency f0 ± (2n-1) · Δf, n is an integer of 0 or more) and the signal light of the even-numbered channel ( A wavelength interleaving unit that separates optical frequencies f0 ± (2n) · Δf, n is an integer of 0 or more), a wavelength selection unit for the odd channel, and a wavelength selection unit for the even channel is there. The wavelength separation unit may also serve as the wavelength multiplexing unit.

  As a result, the size of the mirror part of the wavelength selection means can be made larger than the beam width of each channel after interleaving, eliminating the dead zone that was a problem in the prior art, broadening the bandwidth, and chromatic dispersion ripple Can be reduced.

  For example, the wavelength interleaving means is provided between the wavelength separating means and the wavelength selecting means. Alternatively, the wavelength interleaving means is provided upstream of the wavelength separation means.

  The wavelength interleaving means can be realized by using a periodic filter that repeats reflection and transmission for each optical frequency period Δf.

  Further, by eliminating the discontinuity of the reflectance or transmittance at the boundary between the reflecting portion and the transmitting portion in the wavelength interleaving means by apodization, the chromatic dispersion ripple can be reduced.

  Further, it is desirable that the optical frequency band per channel of the wavelength selecting means is set wider than Δf. As a result, a wide-band wavelength selective switch circuit without a dead zone can be realized.

  Further, a condensing unit can be provided between the wavelength demultiplexing unit, the wavelength interleaving unit, the wavelength multiplexing unit, the output port, or between the wavelength interleaving unit and the wavelength selecting unit. According to this, an optical signal can be efficiently coupled (incident) to each means.

  Alternatively, the wavelength selective switch circuit of the present invention includes two branching means for branching the wavelength multiplexed signal light into two and two wavelength multiplexed signal lights branched by the branching means into signal lights having different wavelengths. A wavelength separation unit, and two wavelength interleaving units may be provided between the wavelength separation unit and the wavelength selection unit, respectively.

  According to this, one wavelength separation means and wavelength interleave means can be used exclusively for odd channels, and the other wavelength separation means and wavelength interleave means can be used exclusively for even channels, and signal light can be used for odd channels and even channels. Separation accuracy when separating into two can be ensured with a simple configuration.

  For example, by using a blocking unit that does not reflect light instead of the reflection unit of the wavelength interleaving means, or by adjusting the angle so that the light reflected by the reflection unit is not coupled to the output port, It is possible to eliminate the leakage of the optical signal between the odd-numbered channels.

  The present invention can also be viewed from the viewpoint of a wavelength path switching device. That is, the present invention is a wavelength path switching device including a wavelength path or wavelength group path switching unit in an optical network, wherein the switching unit includes the wavelength selective switch circuit of the present invention.

  According to this, it is possible to configure a wavelength path switching device such as an optical cross-connect that takes advantage of the wavelength selective switch circuit of the present invention.

  According to the present invention, it is possible to provide a wavelength selective switch circuit having a wider bandwidth than conventional ones. By using this wavelength selective switch circuit for an optical cross-connect, it is possible to connect more stages than in the past, and an optical network can be scaled up.

(First embodiment)
A wavelength selective switch circuit according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a wavelength selective switch circuit according to the first embodiment. Reference numerals 104-1 to 104-3 denote odd-numbered signal light (optical frequency f0 ± (2n-1) · Δf, n is an integer of 0 or more) of wavelength-multiplexed signal light and even-channel signal light (optical frequency). f0 ± (2n) · Δf, where n is an integer equal to or greater than 0).

  The input signal light is wavelength-multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights (optical frequencies f0 ± k · Δf, k is an integer of 0 or more) arranged at an optical frequency interval Δf with the optical frequency f0 as the center. is there. The wavelength multiplexed signal light is input from the input port, and the signal light having different wavelengths is spatially separated by the wavelength separation means 101. The separated signal light is divided into two by the wavelength interleaving means 104-1 for odd-numbered channel signal light and even-numbered signal light.

  The divided odd and even channels are respectively incident on the wavelength selecting units 103-1 and 103-2, and the optical path is switched so that signal light having a desired wavelength is selected and output from the desired output port 1 or 2.

  Between the wavelength selection means 103-1 and 103-2 and the output port 1 or 2, the wavelength interleaving means 104-2 and 104-3 and the wavelength multiplexing means 102-1 and 102-2 are arranged, and the odd channel And even-numbered channels are recombined and wavelength division multiplexing of each spatially separated channel is performed and output from a desired output port 1 or 2.

  FIG. 2 is a diagram for explaining odd / even channel division and wavelength selection by the wavelength interleaving means and the wavelength selecting means. After the wavelength division multiplexed signal light is spatially separated by the wavelength separation unit 101, the odd numbered channels (ch1, ch3, ch5,...) Are reflected by the wavelength interleaving unit 104-1, and the even channels (ch2, ch4, ch6,...) Are reflected. Transparent. The reflected signal light enters the wavelength selection unit 103-1 for the odd channel, and the transmitted signal light enters the wavelength selection unit 103-2 for the even channel.

  In this embodiment, since the odd-numbered channel and the even-numbered channel are divided by the wavelength interleaving means 104-1, and then incident on the wavelength selection means, the size of the mirror portion of the wavelength selection means is determined based on the beam width of each channel after interleaving. By increasing the size, it is possible to eliminate the dead zone that has been a problem in the prior art, and to increase the bandwidth and reduce the chromatic dispersion ripple.

  If the axis where the mirrors are arranged is regarded as the optical frequency axis, the diameter of the mirror part of the wavelength selection means corresponds to the transmission band, and the beam width of each channel after interleaving corresponds to the channel interval Δf. Therefore, as shown in FIG. 1, the wavelength interleaving means, the wavelength selecting means 103-1 for odd channels and the wavelength selecting means 103-2 for even channels are used, and the transmission bands of the wavelength selecting means 103-1 and 103-2 are used. By making the width wider than the channel interval Δf, it is possible to realize a wavelength selective switch circuit having a wide bandwidth without a dead zone.

  For example, in the case of wavelength multiplexed signal light with a channel spacing of 50 GHz, a periodic filter that divides the light into two lights with a spacing of 50 GHz to 100 GHz as wavelength interleaving means, and a MEMS mirror for optical signals with 100 GHz spacing as wavelength selection means Alternatively, it can be realized by using a liquid crystal or an arrayed waveguide grating.

  In the case of this embodiment, the bandwidth mainly depends on the characteristics of the wavelength interleaving means. As the wavelength interleaving means, a prism type periodic filter, a periodic filter using a birefringent medium, an arrayed waveguide grating, or the like can be used (for example, see Non-Patent Document 2). Alternatively, a spatial periodic filter in which mirrors are periodically formed in a comb shape as shown in FIG. 3 can also be used. The bandwidth when such wavelength interleaving means is used can be about 33 GHz. At this time, the number of stages in which the wavelength selective switch circuit can be connected in cascade is 20 or more from FIG. 19, and can be increased to about three times that of the conventional seven stages.

  Further, in a spatial periodic filter in which mirrors as shown in FIG. 3 are periodically formed in a comb shape, discontinuity is caused by apodization of reflectance (or transmittance) at the boundary between the reflecting portion and the transmitting portion. By eliminating it, the ripple of chromatic dispersion can be reduced.

  In the above description and the configuration of FIG. 1, there are two output ports, but a wavelength selective switch circuit having three or more ports is also possible. Further, the wavelength separation means 101 and the wavelength multiplexing means 102-1 and 102-2 may be shared by the same diffraction grating. The wavelength interleaving means 104-1 to 104-3 may be shared by the same comb mirror or the like.

  In addition, as shown in FIG. 4, the signal light is collected between the input port and the wavelength separation means, the wavelength separation means and the wavelength interleaving means, the wavelength interleaving means and the wavelength multiplexing means, and the wavelength multiplexing means and the output port. A condensing means 105 for emitting light may be used.

  In particular, when an optical fiber is used as an input port or an output port, signal light spreads. Therefore, by using a condensing means, it can be efficiently coupled to a wavelength separation means, a wavelength multiplexing means, and a wavelength selection means. Further, although not shown in the figure, a light collecting means may be used between the wavelength interleaving means and the wavelength selecting means. In that case, light can be collected by the wavelength interleaving means.

  5 and 6 are specific configuration examples of the wavelength selective switch circuit of the present embodiment. In this example, the same diffraction grating is used as the wavelength separation means and the wavelength multiplexing means, the input port and the wavelength separation and multiplexing means, the wavelength separation and multiplexing means and the wavelength interleave means, the wavelength separation and multiplexing means and the output port. A light collecting means for condensing the signal light is used. As shown in FIG. 6, the output port 1 or 2 can be selected by changing the angle of the mirror of the wavelength selection means for both the even channel and the odd channel.

  As a result, the spatial wavelength interleaving means can improve the cut-off and increase the bandwidth. Also, a reduction in loss can be expected by integrating wavelength interleaving means and WSS in a spatial system.

  7 and 8 show a second example of the wavelength selective switch circuit configuration of the present embodiment. In this example, the spatial wavelength interleaving means is arranged in a portion where the signal light is parallel. Here, after dividing into an odd channel and an even channel by a wavelength selective switch circuit, one of the optical paths is changed by a mirror. Thereby, there is an advantage in manufacturing such that the mirror array of the wavelength selection means can be arranged in the same plane.

  9 and 10 show a third example of the wavelength selective switch circuit configuration of the present embodiment. In this example, the spatial wavelength interleaving means is arranged at a portion where the signal light is collected. Here, a lens as a condensing means is added between the wavelength interleaving means and the mirror as the wavelength selecting means in the configuration of FIGS. The signal light wavelength-separated from the diffraction grating is condensed by the lens at the position of the wavelength interleaving means, and then condensed by another lens on the mirror as the wavelength selecting means.

  When the spatial spread of the signal light wavelength-separated from the diffraction grating affects the characteristics (wavelength resolution, etc.) of the wavelength interleaving means, this configuration for focusing at the position of the wavelength interleaving means is effective.

(Second embodiment)
A wavelength selective switch circuit according to a second embodiment of the present invention will be described with reference to FIGS. 11 and 12 are configuration diagrams of the wavelength selective switch circuit according to the second embodiment. The feature of this embodiment is that wavelength interleaving means 104-1 to 104-3 are used between the input port and the wavelength separation means 101-1 and 101-2, and the wavelength multiplexing means 102-1 to 102-4 and the output port. About others, it is the same as that of 1st embodiment.

  Therefore, by using the wavelength selective switch circuit of FIG. 11, it is possible to realize a wavelength selective switch circuit with a wider bandwidth and less chromatic dispersion slip than in the prior art.

  As shown in FIG. 12, the condensing means for condensing the signal light between the input port and the wavelength interleaving means 104-1 and between the wavelength interleaving means 104-2 to 3 and the output ports 1 and 2. 105-1 to 10-3 may be used.

(Third embodiment)
A wavelength selective switch circuit according to a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a configuration diagram of the wavelength selective switch circuit of the third embodiment. The feature of this embodiment is that the branching means 106 is between the input port and the wavelength separation means 101-1 and 101-2, and the multiplexing means is between the wavelength multiplexing means 102-1 to 10-4 and the output ports 1 and 2. 107-1 and 107-2. The wavelength interleaving means 104-1 to 104-6 are arranged between the wavelength separation means 101-1 and 101-2 and the wavelength selection means 103-1.

  Wavelength multiplexed signal light is input from the input port, and is split into two equal power lights by the branching means 106. Thereafter, the two branched wavelength multiplexed signal lights are spatially separated into signal lights having different wavelengths by the wavelength separation means 101-1 and 101-2, respectively. The signal light separated by the wavelength separation means 101-1 is transmitted only through the odd-numbered signal light of the wavelength multiplexed signal light by the wavelength interleaving means 104-2, and the even-numbered signal light is blocked. The transmitted odd-numbered channel is incident on the wavelength selecting means 103-1, and the optical path is switched so that the signal light of the desired wavelength is selected and output from the desired port.

  Wavelength interleaving circuits 104-3 and 104-5 and wavelength multiplexing means 102-1 and 102-3 are arranged between the wavelength selection means 103-1 and the output port to recombine and spatially separate odd channels. Wavelength multiplexing of each channel is performed and output from a desired output port.

  On the other hand, the signal light separated by the wavelength demultiplexing means 101-2 is transmitted only through the even-numbered signal light of the wavelength multiplexed signal light by the wavelength interleaving means 104-2, and the odd-numbered signal light is blocked. The transmitted even channel is incident on the wavelength selection unit 103-2, and the optical path is switched so that the signal light of the desired wavelength is selected and output from the desired port.

  Wavelength interleaving means 104-4 and 104-6 and wavelength multiplexing means 102-2 and 102-4 are arranged between the wavelength selecting means 103-2 and the output port, output of even channels, recombination and spatial separation Wavelength multiplexing of each channel is performed and output from a desired output port.

  14 to 16 are configuration examples of this embodiment. As the branching unit 106 and the combining unit 107, a 3 dB coupler, a beam splitter, or the like can be used. As the wavelength interleaving means 104, in the periodic periodic filter formed periodically as shown in FIG. 3, it is used as a blocking portion that does not reflect light instead of the reflecting portion, or reflected by the reflecting portion. Adjust the angle so that light does not couple to the output port. The wavelength interleaving means 104 transmits only odd channels (ch1, ch3, ch5,...) Or only even channels (ch2, ch4, ch6,...). The transmitted signal light enters the wavelength selecting means 103, and the reflected signal light is not used.

  In this embodiment, since the odd-numbered channel and the even-numbered channel are divided by the wavelength interleaving unit 104 and then incident on the wavelength selection unit, the size of the mirror portion of the wavelength selection unit is set to the beam width of each channel transmitted through the wavelength interleaving unit 104 By making it larger, it is possible to eliminate the dead zone that has been a problem in the prior art, and to increase the bandwidth and reduce the chromatic dispersion ripple.

  If the axis on which the mirrors are arranged is regarded as the optical frequency axis, the diameter of the mirror part of the wavelength selection means corresponds to the transmission band. If the transmitted beam width of each channel exceeds the channel interval Δf, interference occurs at the same wavelength component when combining by the multiplexing means, so the beam width of each channel is set so as not to exceed the channel interval Δf. Then, by making the mirror width of each wavelength selection means wider than the transmission beam width of the wavelength interleaving means as shown in FIGS. 14 to 16, it is possible to realize a wavelength selective switch circuit having a wide bandwidth with few dead zones.

  According to the present invention, the number of optical cross-connects can be increased more than before, and an optical network can be scaled up. Therefore, operation efficiency is high for network operators and service quality is high for network users. An optical network can be realized.

The block diagram of the wavelength selective switch circuit of 1st embodiment. The figure explaining odd / even channel division and wavelength selection by wavelength interleaving means and wavelength selection means. The figure which shows the specific example (comb-shaped mirror) of a wavelength interleaving means. The block diagram of the wavelength selective switch circuit of 1st embodiment using a condensing means. The figure (top view) which shows the specific structural example (the 1) of the wavelength selective switch circuit of 1st embodiment. The figure (side view) which shows the specific structural example (the 1) of the wavelength selective switch circuit of 1st embodiment. The figure (top view) which shows the specific structural example (the 2) of the wavelength selective switch circuit of 1st embodiment. The figure (side view) which shows the specific structural example (the 2) of the wavelength selective switch circuit of 1st embodiment. The figure (top view) which shows the specific structural example (the 3) of the wavelength selective switch circuit of 1st embodiment. The figure (side view) which shows the specific structural example (the 3) of the wavelength selective switch circuit of 1st embodiment. The block diagram of the wavelength selective switch circuit of 2nd embodiment. The block diagram of the wavelength selective switch circuit of 2nd embodiment using a condensing means. The block diagram of the wavelength selective switch circuit of 3rd embodiment. The figure (actual drawing) which shows the specific structural example of the wavelength selective switch circuit of 3rd embodiment. The figure (top view) which shows the specific structural example of the wavelength selective switch circuit of 3rd embodiment. The figure (side view) which shows the specific structural example of the wavelength selective switch circuit of 3rd embodiment. Schematic of the structure of the conventional wavelength selective switch. Schematic diagram of the configuration of a conventional wavelength selective switch (actual diagram). The figure which shows the relationship between the number of wavelength selection switch circuit stages (horizontal axis) and Q value penalty (vertical axis) when a 10Gbit / s RZ-DPSK signal is transmitted in cascade. The figure for demonstrating the reason for which the bandwidth of the conventional wavelength selective switch circuit becomes narrow.

Explanation of symbols

1, 2 Output ports 101, 101-1 to 2 Wavelength separating means 102-1 to 4 Wavelength multiplexing means 103, 103-1 to 2 Wavelength selecting means 104-1 to 6 Wavelength interleaving means 105-1 to 6-6 Condensing means 106 Branching means 107-1-2 Multiplexing means

Claims (10)

An input port for inputting a wavelength-multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights (optical frequencies f0 ± k · Δf, k is an integer of 0 or more) arranged at an optical frequency interval Δf with the optical frequency f0 as the center;
Wavelength separation means for separating the wavelength multiplexed signal light input from the input port into signal lights having different wavelengths;
Wavelength selection means for selecting signal light of a desired wavelength from the signal light wavelength-separated by the wavelength separation means and outputting it to a desired output port;
In the wavelength selective switch circuit comprising the wavelength multiplexing means for multiplexing the signal light selected by the wavelength selection means,
Wavelength multiplexed signal light of odd-numbered channel light (optical frequency f0 ± (2n−1) · Δf, n is an integer of 0 or more) and even-numbered signal light (optical frequency f0 ± (2n) · Δf, n) Wavelength interleaving means for separating the integers of 0 or more),
Wavelength selection means for the odd channel;
A wavelength selective switch circuit comprising: wavelength selection means for the even channel.   2. The wavelength selective switch circuit according to claim 1, wherein the wavelength separation means also serves as the wavelength multiplexing means.   3. The wavelength selective switch circuit according to claim 1, wherein the wavelength interleave means is provided between the wavelength separation means and the wavelength selection means.   4. The wavelength selective switch circuit according to claim 1, wherein the wavelength interleaving unit is provided in a stage preceding the wavelength separating unit. 5.   5. The wavelength selective switch circuit according to claim 1, wherein the wavelength interleaving means is a periodic filter that repeats reflection and transmission every optical frequency period Δf.   6. The wavelength selective switch circuit according to claim 5, wherein a discontinuity of reflectance or transmittance is eliminated by apodization at a boundary between the reflecting portion and the transmitting portion in the wavelength interleaving means.   7. The wavelength selective switch circuit according to claim 1, wherein an optical frequency band per channel of the wavelength selecting means is set wider than Δf.   8. The condensing unit according to claim 1, further comprising a condensing unit provided before the wavelength separation unit, the wavelength interleaving unit, the wavelength multiplexing unit, or an output port, or between the wavelength interleaving unit and the wavelength selecting unit. Wavelength selective switch circuit. Branching means for branching the wavelength multiplexed signal light into two;
Two wavelength separation means for separating the two wavelength multiplexed signal lights branched by the branching means into signal lights having different wavelengths, and
The wavelength selective switch circuit according to claim 1, wherein the two wavelength interleaving means are provided between the wavelength separating means and the wavelength selecting means, respectively. In a wavelength path switching device comprising a wavelength path or wavelength group path switching means in an optical network,
10. The wavelength path switching device according to claim 1, wherein the switching means includes the wavelength selective switch circuit according to any one of claims 1 to 9.

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