JP7126259B2 - light switch - Google Patents

Description

The present invention relates to optical switches, and more particularly to path-independent optical switches in which there are no optical waveguide crossings between elementary switches.

An optical switch is a component that can freely and dynamically switch a large number (tens to several tens) of optical paths. In order to improve the quality and capacity of the optical information communication network, it is necessary to realize a large-scale optical switch with many ports. For large-scale optical switches, low loss, low power consumption, small footprint, etc. are important.

In an N×N port optical switch, N! A complete non-blocking optical switch has the property that all the ports can be connected in any order. FIG. 1 shows an example of four ports of a polarization independent loss (PILOSS) type optical switch (Patent Document 1), which is one of the completely non-blocking optical switches. In FIG. 1, A is a 2×2 element switch, B is an optical waveguide cross, and C is an optical waveguide.

If a planar optical circuit technology (PLC technology or silicon photonics technology) capable of forming a large-scale optical circuit is used, it becomes an optical switch that operates only on one side of two orthogonal optical polarizations (TE, TM). On the other hand, in the ordinary optical communication system, both TE and TM signals are multiplexed, so an optical switch capable of handling both polarized waves is required. A PILOSS-type optical switch (Non-Patent Document 1) having a counter-polarization diversity configuration is a configuration that realizes this in a small size, and an example of this configuration is shown in FIG. In FIG. 2, A is a 2×2 element switch, B is an optical waveguide cross, and C is an optical waveguide.

As a problem of the conventional PILOSS-type optical switch, the presence of optical waveguide crossings between 2×2 basic switches causes (1) insertion loss not to be completely path-independent, and (2) loss due to optical waveguide crossings. and (3) the size is limited by the optical waveguide crossings. In addition, since there are many optical waveguide crossings in the polarization diversity configuration, the problem (2) is particularly conspicuous.

Published Patent Gazette Sho 63-500140

K. Tanizawa, et. al., Optics Express 25 (10), 10885-10892 (2017)

It is an object of the present invention to provide an optical switch in which there is no optical waveguide crossing between 2×2 basic switches and the number of passing basic switches does not depend on the path, which can solve the above-mentioned problems of the conventional PILOSS type optical switch.

An optical switch of one aspect of the present invention includes the following configurations (1) to (10).
(1) Contains n (n is the number of ports) concentric circles, the first ring to the n-th ring in order from the outermost circle to the innermost circle, and the x-axis direction is at an angle of 0° when viewed from the center of the ring year,
(2) on the first ring, at angles of 0°, (360/n)°, 2 x (360/n)°, ..., (n-1) x (360/n)°, A 2×2 basic switch is arranged with the input port facing outward and the output port facing _inward , and they are S ₁₁ , S ₁₂ , .
(3) Of the input ports of the S _1i (1≤i≤n) switch, the right input port viewed from the center of the ring is the i-th input port of the optical switch, and the other left input port is terminated. ,
(4) Angles 0.5×(360/n)°, 1.5×(360/n)°, . At each position of 0.5)×(360/n)°, a 2×2 basic switch is arranged with the input port facing outward and the output port facing inward, and these are arranged in order as S _m1 , S _m2 , . , S _mn and
(5) connecting the left output port of the S _(m−1)i switch as seen from the center of the ring and the right input port of the S _mi switch as seen from the center of the ring;
(6) S _{(m−1) (i+1)} -th switch (if i+1>n, S _{(m−1) 1-} th switch) output port on the right side as seen from the center of the ring, and _Smi -th switch , connect the input port on the left side as seen from the center of the ring,
(7) Angles 0°, (360/n)°, 2×(360/n)°, . At each position of (360/n)°, a 2×2 basic switch is arranged with the input port facing outward and the output port facing _inward , and they are named S _k1 , S _k2 , . ,
(8) connecting the output port of the S _(k−1)i-th switch on the right side as seen from the center of the ring and the input port of the S _ki -th switch on the left side as seen from the center of the ring;
(9) S _{(k-1) (i-} 1)-th switch (if i-1 < 1, S _(k-1)n-th switch) port on the left side when viewed from the center of the ring; Connect the port on the right side of the _ki switch when viewed from the center of the ring, and
(10) The right output port of the S _ni -th switch as viewed from the center of the ring is the i-th output port of the optical switch, and the other left output port is terminated.

An optical switch according to another aspect of the present invention includes the following configurations (a) to (g).
(a) arranging 2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) in each row from the first row to the n-th row;
(b) the upper input port of the two input ports of the _S1i -th switch of the first row is the i-th input port of the optical switch, and the other lower input port is terminated;
(c) connecting the lower output port of the S _{(m−1) i} switch (m is an even number greater than 1 and less than or equal to n) with the upper input port of the S _mi switch;
(d) the upper output port of the S _(m−1)(i+1) -th switch (if i+1>n, the S _(m−1)1 switch) and the lower input port of the S _mi -th switch connect the
(e) connecting the upper output port of the S _(k−1)i-th switch (k is an odd number greater than 1 and less than or equal to n) with the lower input port of the S _ki -th switch;
(f) the lower port of the S _{(k−1)(i−1)} th switch (if i−1<1, the S _(k−1)nth switch) and the upper side of the S _ki switch connect the ports of
(g) The upper output port of the S _ni -th switch in the n-th column is the i-th output port of the optical switch, and the other lower output port is terminated.

An optical switch according to another aspect of the present invention includes the following configurations (A) to (F).
(A) arranging 2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) in each row from the first row to the n-th row;
(B) 2n 1-input, 2-output polarization splitting elements are arranged, the input port of the 2×i-th polarization splitting element is the i-th input port, and one output port of the polarization splitting element is the i-th input port. The other output port of the polarization separation element is connected to the lower right _{port of the S nA switch} of the nth column, where A=1+{( l+i−2) mod n}, l (English letter ell, hereinafter the same) is the smallest integer of n/2 or more, mod means remainder operation,
(C) The input port of the 2×i+1-th polarization separation element is the {1+[(l+i−1) mod n]}-th output port, and one output port of the polarization separation element is the S _1i -th switch. the bottom left port and the other output port of the polarization separation element to the top right port of the _SnB switch, where B=1+{(l+i−1) mod n};
(D) connecting the lower right port of the S _{(m−1) i} switch (m is an even number greater than 1 and equal to or less than n) and the upper left port of the S _mi switch,
(E) Connect the upper right port of the S _(m−1)(i+1) switch (if i+1>n, the S _{(m−1) 1} switch) and the lower left port of the S _mi switch. ,
(F) connecting the upper right port of the S _{(k−1) i} switch (k is an odd number greater than 1 and less than or equal to n) and the lower left port of the S _ki switch;
(G) The lower right port of the S _{(k−1)(i−1)} th switch (if i−1<1, the S _(k−1)nth switch) and the upper left port of the S _kith switch port is connected.

According to the present invention, it is possible to provide an optical switch in which there is no loss due to optical waveguide crossings, and at the same time the insertion loss can be completely path independent or not limited in size by optical waveguide crossings.

1 is a diagram showing a configuration example of a conventional polarization independent loss (PILOSS) type optical switch with four ports; FIG. FIG. 2 is a diagram showing a configuration example of a conventional PILOSS-type optical switch having an opposing polarization diversity configuration; 1 is a diagram showing the configuration of a 2×2 basic switch according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing a connection example after optical switching of the 2×2 basic switch of one embodiment of the present invention in FIG. 3 ; 1 is a diagram showing the configuration of a concentric n×n optical switch according to one embodiment of the present invention; FIG. It is a figure which shows the structure of the 4x4 optical switch of one Embodiment of this invention. It is a figure which shows the structure of the 4x4 optical switch of one Embodiment of this invention. It is a figure which shows the structure of the 4x4 optical switch of one Embodiment of this invention. FIG. 9 is a schematic diagram showing a bridge structure in region A of FIG. 8; It is a schematic diagram which shows the difference of an area by the presence or absence of intersection. FIG. 11 is a diagram quantitatively showing the difference in area of FIG. 10; It is a figure which shows the structure of the nxn optical switch of one Embodiment of this invention. It is a figure which shows the structure of the 4x4 optical switch of one Embodiment of this invention. It is a figure which shows the structure of the 4x4 optical switch of one Embodiment of this invention. FIG. 15 is a diagram showing an example of a signal path of the 4×4 optical switch of one embodiment of the present invention of FIG. 14;

An embodiment of the present invention will be described with reference to the drawings. First, a 2×2 basic switch that constitutes an optical switch according to one embodiment of the present invention will be described. The 2x2 basic switch used in the present invention is generally referred to as "an optical switch with two inputs and two outputs, where the input ports are located in the upper left and lower right, and the output ports are located in the lower left and upper right. can be defined as As a specific example, FIG. 3 shows the configuration of a 2×2 basic switch according to one embodiment of the present invention.

In FIG. 3(a), two input ports IN1, IN2 are at the top left and bottom left, and two output ports OUT1, OUT2 are at the top right and bottom right. FIG. 3B shows a specific optical circuit structure when a Mach-Zehnder (MZI) switch is used as the optical switch. Solid lines in the figure represent optical waveguides, which include phase shifter regions 1 and 2 and optical couplers 3 and 4 before and after them. For example, when a silicon (Si) optical waveguide is used, the size of the structure in FIG. 3B is approximately 111 μm wide×100 μm long.

In the configuration of FIG. 3(b), by electrically controlling the refractive indices of the phase shifter regions 1 and 2, the light input via the optical coupler 3 is switched to cross or bar state and is transmitted via the optical coupler 4 The output can switch the light to a predetermined path. FIG. 4 is a diagram showing a connection example after optical switching of the 2×2 basic switch of one embodiment of the present invention in FIG. As shown in FIG. 4(a), by setting (controlling) the phase shifter of each MZI switch, the upper left input port IN1 and the upper right output port OUT1 can be connected, and furthermore, the lower left input port IN2 and the lower right output port can be connected. OUT2 can be connected. Further, as shown in FIG. 4(b), by setting (controlling) the phase shifter of each MZI switch, the upper left input port IN1 and the lower right output port OUT2 can be connected, and furthermore, the lower left input port IN2 and the upper right input port IN2 can be connected. Output port OUT1 can be connected.

FIG. 5 is a schematic diagram showing the configuration of a concentric n×n optical switch according to one embodiment of the present invention. In FIG. 5, solid lines represent optical waveguides. First, n (n is the number of ports) concentric circles as indicated by dotted lines in FIG. 5 are assumed. The outermost circle to the innermost circle are named 1st to nth rings in order. The x-axis direction is defined as an angle of 0° when viewed from the center of the ring. 2×2 at each position of angle 0°, (360/n)°, 2×(360/n)°, . The basic switches are arranged so that the input ports face outward and the output ports face inward, and they are named S ₁₁ , S ₁₂ , . . . S _1n in order. Among the input ports of the S _1i (1≤i≤n) switch, the input port on the right side as viewed from the center of the ring is assumed to be the i-th input port of the optical switch. The other left input port is not used and is terminated. For the 2×2 basic switch, for example, switches having configurations shown in FIGS. 3 and 4 can be used. Note that each S _1i (1≦i≦n) switch of the first ring may be replaced with a 2×2 switch and a 1×2 switch may be used.

Next, angles 0.5 × (360/n) °, 1.5 × (360/n) °, ..., (n- At each position of 0.5)×(360/n)°, a 2×2 basic switch is arranged with the input port facing outward and the output port facing inward, and these are arranged in order as S _m1 , S _m2 , . , _Smn . The left output port of the S _(m−1)i-th switch seen from the ring center is connected to the right-hand input port of the S 1 _mi switch seen from the ring center. The output port on the right side of the ring center of the S _{(m−1)(i+1)th} switch (if i+1>n, the S _(m−1)1 switch) and the _Smith switch from the ring center Connect the input port on the left as you see.

Similarly, angles 0°, (360/n)°, 2×(360/n)°, . At each position of (360/n)°, a 2×2 basic switch is arranged with the input port facing outward and the output port facing _inward , and they are named S _k1 , S _k2 , . Name. The right output port of the S _(k−1)i-th switch as seen from the ring center is connected to the left-hand input port of the S _{ki -th} switch as seen from the ring center. S _(k-1)(i- 1)-th switch (if i-1<1, S _(k-1)n-th switch) port on the left side of the ring center and the ring of S _ki -th switch Connect the port on the right side when viewed from the center.

Finally, the output port on the right side of the center of the ring of the _Sni -th switch is assumed to be the i-th output port of the optical switch. The other left output port is terminated because it is not used. A 2×1 switch may be used instead of a 2×2 switch for each S _ni switch in the nth ring. As described above, an n×n switch can be configured.

The configuration of a 4×4 optical switch with n=4 will be described with reference to FIGS. 6 to 8. FIG. FIG. 6 is a configuration example of a 4×4 optical switch in which n=4 is substituted in the configuration of the concentric n×n optical switch in FIG. 5 and arranged as it is. In each figure, solid lines represent optical waveguides. Consider hypothetically from the outermost first ring to the innermost fourth ring. 2×2 basic switches S ₁₁ , S ₁₂ , S ₁₃ and S ₁₄ are arranged at four positions of 0°, 90°, 180° and 270° on the first ring. 2×2 basic switches S ₂₁ , S ₂₂ , S ₂₃ and S ₂₄ are arranged at four positions of 45°, 135°, 225° and 315° on the second ring. 2×2 basic switches S ₃₁ , S ₃₂ , S ₃₃ and S ₃₄ are arranged at four positions of 0°, 90°, 180° and 270° on the third ring. 2×2 basic switches S ₄₁ , S ₄₂ , S ₄₃ and S ₄₄ are arranged at four positions of 45°, 135°, 225° and 315° on the fourth ring. The input ports on the right side of the ring center of S ₁₁ to S ₁₄ on the first ring are assumed to be the first input port (1) to the fourth input port (4) of the optical switch. The output ports on the right side of the ring center of S ₄₁ to S ₄₄ on the fourth ring are assumed to be the first output port (1') to the fourth output port (4') of the optical switch.

An advantage of the optical switch of FIG. 6 is that there are no crossover losses between the 2×2 elementary switches, so no crossover loss occurs. Also, since the structure is symmetrical (n-fold rotational symmetry) with respect to each port, it has the feature that the number of switches passed during propagation is equal to the length of the optical waveguide, regardless of the connection path. With this structure, it is possible to achieve both elimination of loss due to optical waveguide crossings and complete path-independence of insertion loss, which were problems of conventional PILOSS switches. However, since the output ports 1' to 4' are all inside, it is necessary to use a vertical coupler such as a grating coupler when extracting light from the output ports. 5 and 6, which are left-right reversed, also operate as an n.times.n optical switch.

In the configuration of FIG. 6, if one of the 2×2 basic switches is used as a reference and the adjacent 2×2 basic switches are rearranged while bringing them closer together, a 4×4 optical switch configuration as shown in FIG. 7 is obtained. is possible. In the configuration of FIG. 7, four 2×2 basic switches S ₁₁ to S ₁₄ , S ₂₁ to S2 ₂₄ , S ₃₁ to S ₃₄ , and S ₄₁ to S ₄₄ are arranged in order in each of columns 1 to 4. It is The upper input ports of S ₁₁ to S ₁₄ on the first column are assumed to be the first input port (1) to the fourth input port (4) of the optical switch. The upper output ports of S ₄₁ to S ₄₄ on the fourth column are the first output port (1') to the fourth output port (4') of the optical switch. With such an arrangement, the space between the switches can be reduced, and since there are no intersections between the basic switches, it is possible to realize a smaller optical switch than the conventional PILOSS structure. However, since the output ports 1' to 4' are all inside, it is necessary to use a vertical coupler such as a grating coupler when extracting light from the output ports.

FIG. 8 shows the configuration of a 4×4 optical switch in which the output ports 1′ to 4′ are on the outside. Other configurations are the same as in FIG. In the configuration of FIG. 8, the horizontally extending optical waveguides from each of the upper output ports of S ₄₁ -S ₄₄ on the fourth row must be bridged over the three intersecting vertical optical waveguides. FIG. 9 shows an example of the bridge structure using interlayer optical connection. FIG. 9 illustrates interlayer optical connection in region A of FIG. Light from the 2x2 elementary switch S _{41 traverses} from the lower optical waveguide to the upper optical waveguide, and at its end returns to the lower optical waveguide and travels to output port 1'. The configuration of the 4×4 optical switch of FIG. 8 allows for end-face connections because the output ports are outside the switch. Also in this case, the 2.times.2 basic switch and the optical waveguide crossover can be spatially separated and can be integrated at high density, so that miniaturization of the entire optical switch can be expected.

Here, a configuration when the configuration of the matrix-arranged 4×4 optical switch shown in FIGS. 7 and 8 is expanded (generalized) to an n×n optical switch is shown below. That is, an optical switch of one embodiment of the present invention includes the following configuration. 2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) are arranged in each column from the first column to the n-th column. The upper input port of the two input ports of the _S1i -th switch in the first row is taken as the i-th input port of the optical switch, and the other lower input port is terminated. The lower output port of the S _(m−1)i-th switch (m is an even number greater than 1 and less than or equal to n) is connected to the upper input port of the S _mi -th switch.

Connect the upper output port of the S _(m−1)(i+1) -th switch (if i+1>n, the S _(m−1)1 switch) and the lower input port of the S _mi -th switch . The upper output port of the S _(k−1)i-th switch (k is an odd number greater than 1 and less than or equal to n) is connected to the lower input port of the S _ki -th switch. The lower port of the S _(k−1)(i− 1)-th switch (if i−1<1, the S _(k−1)n switch) and the upper port of the S _ki -th switch Connecting. The upper output port of the _n -th Sni-th switch is the i-th output port of the optical switch, and the other lower output port is terminated.

FIG. 10 shows a diagram for explaining the difference between the conventional system and the system of the present invention when an MZI switch is used as the 2.times.2 basic switch _Sij . In the conventional system shown in FIG. 10(a), a region of length L _IS =approximately 207 μm is required to insert the optical waveguide intersection between the MZIs. This length mainly depends on the thermo-optical phase shifter spacing W _MZI in the MZI. The value of this interval _WMZI needs to be a constant value in order to sufficiently avoid thermal interference between adjacent thermo-optical phase shifters. Since it is typically around 100 μm, the value of 100 μm is used in the example of FIG. FIG. 10(b) shows the scheme of the present invention. The presence of the optical waveguide crossings outside the switch matrix allows the area of the optical waveguide crossings to be reduced to a length L _IS =20 μm due to the bend radius. Also, optical waveguide crossings can be compacted by integration.

In order to quantitatively show the advantages (effects) of the system of the present invention, FIG. 11 shows the result of calculating how much size can be typically reduced by the design example shown in FIG. Comparing the conventional system of the white bar graph in FIG. 11 and the system of the invention of the hatched bar graph, it is expected that the area ratio of the system of the invention can be reduced by approximately 2.1 to 2.6 times. However, in the calculation, the bend radius is 10 μm, the length of the MZI is 111 μm, and the minimum distance between adjacent intersections when integrating optical waveguide intersections is 10 μm.

The conventional PILOSS-type optical switch with the opposite polarization diversity configuration shown in FIG. 2 passes through up to 7N−3 optical waveguide crossings per path. Considering a loss of 0.025 dB per optical waveguide intersection, the total loss for N=32 is 5.5 dB, which is a relatively large loss. If the loss of the optical waveguide crossing is greater than this, the total loss will also increase. Therefore, it is important to eliminate optical waveguide crossing loss in a polarization diversity configuration. One of the methods for eliminating the in-plane crossing is to use two layers of optical circuits.

In the silicon photonics technology, it is possible to form a second-layer optical circuit on a silicon optical circuit by film formation and processing of silicon nitride. On the other hand, with the conventional structure, it is extremely difficult to form a two-layered structure due to the intricate crossing of the optical waveguides. For example, if light is transferred from the first layer to the second layer before the optical waveguide intersection (interlayer optical connection) and returned after the intersection, the in-plane intersection can be avoided. However, since the light passes through many interlayer optical connection structures, the total loss becomes worse due to the loss (<1 dB) of the interlayer connection itself.

Therefore, the present invention proposes the structure shown in FIG. FIG. 12 shows a configuration example of polarization diversity when the number of ports is n (n is an integer). In the figure, the solid line represents the optical waveguide of the first layer, and the dotted line represents the optical waveguide of the second layer. The black square on the right is the interlayer interconnect structure that transfers light between the first and second layers, and the open square on the left represents the polarization splitter rotator (PSR). Here, the PSR is an element that rotates the polarization of the side arm by 90 degrees after passing through a polarization beam splitter (PBS).

In FIG. 12, l (English letter ell, the same applies hereinafter) is defined as the smallest integer equal to or greater than n/2. Each of S _ij in the figure represents a 2×2 basic switch. Of the left two ports of S ₁₁ to S _1n , the upper and lower ports are called "upper and lower ports". Similarly, the two ports on the right side of S _n1 to S _nn are called "upper and lower ports". In FIG. 1, the structure except for the PSR indicated by white squares, the optical waveguide of the second layer indicated by dotted lines, and the interlayer connection structure indicated by black squares is as described above with reference to FIGS. The following describes how the PSR, dotted lines, and interlayer connection structure are connected.

Leaving a general description for later, let us first focus on _S11 . One output port of PSR is connected to the upper port of _S11 , and the other output port is connected to the lower port of _Snl on the right side through an interlayer connection structure using a second layer optical waveguide (dotted line). . This is expressed as "connecting the upper port of _S11 and the lower port of _Snl ". Similarly, connect the lower port of S ₁₁ and the upper port of S _n(l+1) . The input ports of the PSR connected to the upper and lower ports of _S11 are named the first input port and the (l+1)'th output port, respectively.

The connection of the general overall configuration is as follows. 2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) are arranged in each column from the first column to the n-th column. Connect the top left port of the _S1ith switch to the bottom right port of the nth _SnA switch. Connect the bottom left port of the S _1ith switch to the top right port of the _SnB switch. Here, mod means remainder operation, and A=1+{(l+i-2) mod n}, B=1+{(l+i-1) mod n}. Also, the input ports of the PSR connected to the upper left and lower left ports of the S _1ith switch are named the ith input port and the {1+[(l+i−1)mod n]}′th output port, respectively.

The lower right port of the S _(m−1)i-th switch (m is an even number greater than 1 and less than or equal to n) is connected to the upper left port of the S _mi -th switch. The upper right port of the S _(m−1)(i+1) -th switch (if i+1>n, the S _(m−1)1 switch) and the lower left port of the S _mi -th switch are connected. The upper right port of the S _(k−1)i-th switch (k is an odd number greater than 1 and less than or equal to n) is connected to the lower left port of the S _ki -th switch. The lower right port of the S _(k−1)(i− 1)-th switch (if i−1<1, the S _(k−1)n switch) and the upper left port of the S _ki -th switch Connecting. By repeating the above operations, a polarization diversity configuration for a general order n is completed. The left port arrangement is 1, (l+1)′, 2, (l+2)′, . . . , i, {1+[(l+i−1) mod n]}′, .

FIG. 13 shows a configuration example in the case of a 4×4 optical switch (n=4, l=2). In FIG. 13, the second optical waveguide indicated by the dotted line is arranged above the 2×2 basic switch _Sij . Focusing _on the upper port of S11, it connects to the lower port of _S42 . The lower port of _S11 connects to the upper port of _S43 . Other ports are similarly connected. FIG. 14 shows a configuration example of another 4×4 optical switch (n=4, l=2). In FIG. 14, the second-layer optical waveguide indicated by the dotted line is arranged separately above and below the 2×2 basic switch _Sij . The method of connecting the optical waveguides in the second layer indicated by the dotted line is basically the same as in the case of FIG.

The operation of the 4×4 optical switch (polarization diversity configuration) in FIG. 14 will be described with reference to FIG. First, as an example, a method of connecting the input 1 to the output 3' in a 4.times.4 optical switch will be described. The input light contains both TE and TM light components. Both of these light components must be propagated correctly from input 1 to output 3'. The PSR separates the input light into a TE component and a TM component, and converts the polarized wave of the TM component into the TE polarized wave. Here, light that was originally a TE component is represented by TE, and light that was originally a TM component is represented by TM. To connect input 1 to output 3', switch _S11 of the first row is in the bar state and the others are in the cross state. In FIG. 15, it can be seen that both the TE path and TM path light components pass through _S11 and finally converge at the output 3' PSR. The TE and TM light components are synthesized again by this PSR and output from the output 3'. The above is an example of the operation of the polarization diversity configuration, and the same applies to other optical paths.

The configurations of FIGS. 13 and 14 can be converted to the same configuration as the conventional configuration shown in FIG. 2 simply by rearranging the switches while adopting the arrangement of the compact 4×4 optical switches according to the present invention, resulting in a polarization diversity configuration. It can be seen that Furthermore, by using a two-layer optical circuit, the number of in-plane intersections becomes zero, and loss due to intersections can be eliminated. In the method of the present invention, the number of interlayer optical connections is only two (up/down) for any route, and it is expected that a loss reduction of about 3 to 5 dB can be achieved in total even when N=32. .

Embodiments of the present invention have been described with reference to the drawings. However, the invention is not limited to these embodiments. Furthermore, the present invention can be implemented with various improvements, modifications, and variations based on the knowledge of those skilled in the art without departing from the scope of the invention.

The optical switch of the present invention can be widely applied to optical switches of various scales as components constituting optical circuits and optical integrated circuits.

1, 2: phase shifter region 3, 4: optical coupler

Claims (8)

an optical switch,
n (n is the number of ports) concentric circles, the outermost circle to the innermost circle are designated as the first ring to the n-th ring in order, and the x-axis direction as viewed from the center of the ring is at an angle of 0°,
2×2 at each position of angle 0°, (360/n)°, 2×(360/n)°, . arranging the basic switches so that the input ports face outward and the output ports face inward, and call them S ₁₁ , S ₁₂ , . . . , S _1n ;
Among the input ports of the S _1i -th (1≤i≤n) switch, the input port on the right side as viewed from the center of the ring is the i-th input port of the optical switch, and the other input port on the left side is terminated,
Angle 0.5×(360/n)°, 1.5×(360/n)°, . )×(360/n)°, a 2×2 basic switch is arranged with the input port facing outward and the output port facing inward, and these are arranged in order as S _m1 , S _m2 , . . . , S _mn ,
connecting the output port on the left side of the S _{(m−1) i} switch when viewed from the center of the ring and the input port on the right side of the S _mi switch when viewed from the center of the ring;
The output port on the right side of the S _(m−1)(i+1) -th switch (if i+1>n, the S _(m−1)1 switch) seen from the center of the ring and the S _mi -th switch seen from the center of the ring to connect the left input port, and
Angle 0°, (360/n)°, 2×(360/n)°, . )°, a 2×2 basic switch is placed with the input port facing outward and the output port facing _inward , and let them be S _k1 , S _k2 , .
connecting the output port on the right side of the S _(k−1)i-th switch with respect to the ring center and the input port on the left side of the ring center of the S _{ki -th} switch;
S _(k-1)(i- 1)-th switch (if i-1<1, S _(k-1)n-th switch) port on the left side of the ring center and the ring of S _ki -th switch Connect the port on the right side as seen from the center,
An optical switch in which the output port on the right side of the ring center of the S _{ni -th} switch is the i-th output port of the optical switch, and the other output port on the left side is terminated. 2. The optical switch according to claim 1, wherein said 2*2 basic switch comprises a 2-input 2-output Mach-Zehnder interferometer. replacing the 2×2 elementary switches of the S _1i switches of the first ring with 1×2 switches, and replacing the 2×2 elementary switches of the S _ni switches of the nth ring with 2×1 switches; The optical switch of claim 1. an optical switch,
2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) are arranged in each row from the first row to the n-th row,
the upper input port of the two input ports of the _S1i -th switch of the first row is the i-th input port of the optical switch, and the other lower input port is terminated;
connecting the lower output port of the S _{(m−1) i} switch (m is an even number greater than 1 and less than or equal to n) and the upper input port of the S _mi switch;
Connect the upper output port of the S _{(m−1)(i+1)th} switch (if i+1>n, the S _(m−1)1 switch) and the lower input port of the _Smi switch. ,
connecting the upper output port of the S _(k−1)i-th switch (k is an odd number greater than 1 and less than or equal to n) and the lower input port of the S _ki -th switch;
The lower output port of the S _{(k−1)(i−1) th} switch (if i−1<1, the S _(k−1)n switch) and the upper input of the S _ki switch connect the port,
An optical switch in which the upper output port of the n-th S _ni switch is the i-th output port of the optical switch and the other lower output port is terminated. 5. The optical switch according to claim 4, wherein said 2×2 basic switch comprises a 2-input 2-output Mach-Zehnder interferometer. replacing the 2×2 elementary switches of the S _1i switches of the first row with 1×2 switches, and replacing the 2×2 elementary switches of the S _ni switches of the n row with 2×1 switches; 5. An optical switch according to claim 4. an optical switch,
2×2 basic switches S _ij (1≦i≦n, 1≦j≦n) are arranged in each row from the first row to the n-th row,
2n 1-input, 2-output polarization splitting elements are arranged, the input port of the 2×i-th polarization splitting element is the i-th input port, and one output port of the polarization splitting element is the first column. The other output port of the polarization separation element is connected to the lower right _{port of the S nA switch} of the nth column, where A=1+{(l+i− 2) mod n}, l is the smallest integer greater than or equal to n/2, mod means remainder operation,
The input port of the 2×i+1-th polarization separation element is the {1+[(l+i−1) mod n]}-th output port, and one output port of the polarization separation element is the lower left port of the S _1i -th switch. , and the other output port of the polarization separation element is connected to the upper right port of the S _nB switch, where B=1+{(l+i−1) mod n};
connecting the lower right port of the S _{(m−1) i} switch (m is an even number greater than 1 and equal to or less than n) and the upper left port of the S _mi switch,
Connect the upper right port of the S _{(m−1)(i+1)th} switch (if i+1>n, the S _(m−1)1 switch) and the lower left port of the _Smi switch,
connecting the upper right port of the S _{(k−1) i} switch (k is an odd number greater than 1 and less than or equal to n) and the lower left port of the S _ki switch,
The lower right port of the S _(k−1)(i− 1)-th switch (if i−1<1, the S _(k−1)n switch) and the upper left port of the S _ki -th switch connected optical switch. 8. The optical switch according to claim 7, wherein said 2x2 basic switch comprises a 2-input 2-output Mach-Zehnder interferometer.

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