阅读说明：本技术 N×n光开关 (NXN optical switch ) 是由 村中勇介 中原达志 桥本俊和 于 2018-04-19 设计创作，主要内容包括：本发明提供一种N×N光开关,其为将输入侧光开关的输出端口和输出侧光开关的输入端口在同一基板上由光波导连接而构成的光开关,在该光开关的交叉数最多、交叉损失最高的光波导所连接的端口中,能减少交叉损失。4×4光开关(10)具备：四个输入侧1×4光开关(SW11～SW14),具有四个输出端口(P1～P4)；四个输出侧4×1光开关(SW21～SW24),具有四个输入端口(Q1～Q4)；以及连接光波导(OW),连接所述输出端口和所述输入端口,其中,一部分连接光波导OW与两条以上的其他连接光波导OW在一处交叉。(the invention provides an N x N optical switch, which is an optical switch formed by connecting an output port of an input-side optical switch and an input port of an output-side optical switch on the same substrate by optical waveguides. A4 x 4 optical switch (10) is provided with: four input-side 1 × 4 optical switches (SW11 to SW14) having four output ports (P1 to P4); four output side 4 × 1 optical switches (SW21 to SW24) having four input ports (Q1 to Q4); and a connection Optical Waveguide (OW) connecting the output port and the input port, wherein a part of the connection Optical Waveguide (OW) intersects with two or more other connection Optical Waveguides (OW) at one point.)

1. An N x N optical switch, comprising: n input side 1 XN optical switches having N output ports; n output side N × 1 optical switches having N input ports; and a connection optical waveguide connecting the output port and the input port, N being an integer of 3 or more, the N × N optical switch being characterized in that,

A part of the connection optical waveguide intersects with two or more other connection optical waveguides at one point.

2. the NxN optical switch according to claim 1,

The intersection of the connection optical waveguide and the other connection optical waveguides is an MMI intersection structure.

3. the NxN optical switch according to claim 1 or 2,

The input side 1 × N optical switch and the output side N × 1 optical switch are arranged in a straight line such that the output port faces the input port,

the output port on one end side of the input-side 1 × N optical switch located on one end side of the input-side 1 × N optical switch is connected to the input port on one end side of the output-side N × 1 optical switch located on one end side of the output-side N × 1 optical switch via the connection optical waveguide that does not intersect with another connection optical waveguide,

The output port on the other end side of the input side 1 × N optical switch located on the other end side of the input side 1 × N optical switch is connected to the input port on the other end side of the output side N × 1 optical switch located on the other end side of the output side N × 1 optical switch via the connection optical waveguide not intersecting with the other connection optical waveguide,

the output port of the input-side 1 × N optical switch located on one end side of the input-side 1 × N optical switches other than the one end side is connected to the input port of the output-side N × 1 optical switch located on the other end side of the output-side N × 1 optical switches other than the one end side via the connection optical waveguide intersecting with the other connection optical waveguide,

the output ports of the input side 1 × N optical switches located on the other end side are connected to the input ports of the output side N × 1 optical switches located on the other end side of the output side N × 1 optical switches and different from each other by the connection optical waveguide intersecting with the other connection optical waveguide,

The output port of the input-side 1 × N optical switch located outside both ends of the input-side 1 × N optical switch is connected to the input port of the output-side N × 1 optical switch different from each other, through the connection optical waveguide intersecting with another connection optical waveguide.

4. The NxN optical switch according to claim 1 or 2,

The input side 1 × N optical switch and the output side N × 1 optical switch are arranged side by side with each other,

The output ports at both ends of the input-side 1 × N optical switch are connected to the input ports at the end portions of the output-side N × 1 optical switches adjacent to the input-side 1 × N optical switch and different from each other via the connection optical waveguides that do not cross other connection optical waveguides,

The output ports of the input-side 1 × N optical switch other than the output ports located at both ends are connected to the input ports of the output-side N × 1 optical switches not adjacent to the input-side 1 × N optical switch and different from each other, located at both ends, via the connection optical waveguides intersecting with the other connection optical waveguides.

5. the NxN optical switch according to any one of claims 1 to 4,

The input side 1 × N optical switch, the output side N × 1 optical switch, and the connection optical waveguide are monolithically formed on the same semiconductor substrate.

6. The NxN optical switch according to any one of claims 1 to 5,

The intersection angle of the intersection portion of the connection optical waveguide and the other connection optical waveguide is equal to the same angle.

Technical Field

the present invention relates to an N × N optical switch as an important optical component for supporting a large-capacity optical communication network.

background

In recent years, in order to cope with a rapid increase in communication traffic, an optical communication network has been advancing to have a high speed and a large capacity. An optical communication network is composed of a plurality of links and nodes, and research and development are being conducted on the links and nodes for high-speed and large-capacity communication, respectively.

while a link is advancing to speed up signals, multiplex wavelengths, and the like, a technique of flexibly changing paths between connected nodes is important in order to realize efficient traffic on the nodes. For example, in a known technique, an optical signal to be transmitted is once subjected to photoelectric conversion at an input end of a node, an electrical signal is switched, and the optical signal is subjected to photoelectric conversion again at an output end of the node and transmitted. In this case, much power is consumed for photoelectric conversion and high-speed switching of electric signals.

On the other hand, a technique of arranging an optical switch in a node and switching without converting an optical signal into an electrical signal has been studied and developed. In this case, since the optical switch directly switches the optical signal and changes the path, it is not necessary to perform photoelectric conversion or high-speed switching of the electrical signal, and thus it is possible to switch the high-speed optical signal with low delay and low power consumption.

As such Optical switches, there are thermo-Optical (TO) switches configured on Planar Lightwave Circuits (PLC), switches using InP-based electric field absorption type Optical modulators (EAM), Mach-Zehnder interferometers (MZI), or Semiconductor Optical Amplifiers (SOA), and BinNO switches₃A phase modulator type switch of the system and the like are under study and development.

For example, non-patent document 1 proposes an example in which an optical switch is configured on a PLC.

As shown in non-patent document 1, as a main configuration of the N × N optical switch, for example, a configuration in which N1 × N optical switches and N × 1 optical switches are connected (where N is a positive integer) is conceivable.

fig. 5 shows a conventional N × N optical switch 100 as an example. As shown in fig. 5, the conventional N × N optical switch 100 includes: n input-side 1 XN optical switches SW11 to SW 1N; and N output side N × 1 optical switches SW21 to SW2N (N is 4 in fig. 5, see later).

the optical pulse groups input from the input ports are output from the input-side 1 × N optical switches SW11 to SW1N to the output-side N × 1 optical switches SW21 to SW2N connected to desired output ports. Therefore, any connection can be realized regardless of the connection state of other ports, and a non-blocking (non-blocking) type N × N optical switch is realized.

as a conventional technique for configuring an input-side 1 × N optical switch, for example, patent document 1 proposes a 2 × 2 optical switch element. Fig. 6 is a perspective view of a conventional 2 × 2 optical switching element. The 2 × 2 optical switching element of fig. 6 is a directional coupler type optical switching element, and is configured such that an optical input section I, an optical switching section II, an optical output section III, and an optical absorption section IV are provided on an n-InP substrate 6.

More specifically, the conventional 2 × 2 optical switching element shown in fig. 6 has a structure in which an i-MQW layer 5, an i-InP clad layer 4, and a p-InP clad layer 3 are sequentially stacked on an n-InP substrate 6. As shown in fig. 6, the p-InP clad layer 3 is formed in a thin line shape. p-InP cladding layers 3 of the optical switch section II and the two p-InP cladding layers 3 of the optical absorption section IV are formed in this order⁺An InGaAs cap layer 2 and a p-type electrode 1. An n-type electrode 7 is formed on the back surface of the n-InP substrate 6. In fig. 6, A, B denotes an input port, and C, D denotes an output port.

Input signal light such as a group of optical pulses is guided in a portion of the i-MQW layer 5 located below the p-InP clad layer 3 formed in a thin line shape. Hereinafter, the I-MQW layer 5 provided below the p-InP clad layer 3 in the light input section I, the light switch section II, the light output section III, and the light absorption section IV is referred to as an input waveguide, an optical switch waveguide, an output waveguide, and a light absorption waveguide, respectively.

the input signal light is input to either one of the input waveguides and guided to the optical switch waveguide. In the optical switch waveguide, a desired voltage is applied between the p-type electrode 1 and the n-type electrode 7 provided in the optical switch section II, and signal light is output from only one of the optical switch waveguides by changing the refractive index of the optical switch waveguide below the p-type electrode 1 by, for example, the Quantum Confinement Stark Effect (QCSE) due to the Multiple Quantum Well (MQW) structure. Namely, the optical path switching is performed. In the light absorbing section IV, a desired electric field is applied between the p-type electrode 1 and the n-type electrode 7 provided in a light absorbing waveguide different from the light absorbing waveguide to which the signal light is input. Thus, the crosstalk light leaking from the optical switch waveguide is absorbed by the light-absorbing waveguide, while the signal light output from the optical switch waveguide is guided to the output waveguide. As described above, in patent document 1, the light absorbing portion IV is provided, thereby realizing a switching element capable of reducing the influence of light leaking from the optical switch waveguide.

Disclosure of Invention

In the above-mentioned non-patent document 1, N input side 1 × N optical switches and N output side N × 1 optical switches are connected by optical fibers, thereby realizing N × N optical switches. In this case, N × N optical fibers, and optical fiber connection points and connectors at 2 × N are required, and the size of the optical switch increases. In addition, a highly optically sealed waveguide such as a semiconductor optical waveguide has a large mode mismatch with an optical fiber, and a large loss occurs in optical coupling. In this configuration, coupling loss occurs four times in each path, and the insertion loss of the N × N optical switch increases.

Therefore, in order to reduce the size and loss of the N × N optical switch, it is conceivable to perform these connections by using a waveguide on the same substrate (see, for example, patent document 2).

here, when the configuration of the N × N optical switch in fig. 5 is implemented on the same substrate, a region having a mechanism for switching an optical path of 1 × N is referred to as an input-side 1 × N optical switch, a region having a mechanism for switching an optical path of N × 1 is referred to as an output-side N × 1 optical switch, and N input-side 1 × N optical switches and N output-side N × 1 optical switches are arranged. The optical switches are connected by waveguides on the same substrate.

Specifically, an example in which N is 4 shown in fig. 5 is described, and in the 4 × 4 optical switch shown in fig. 5, the input side 1 × 4 optical switches SW11 to SW14 are arranged in a row, and the output side N × 1 optical switches SW21 to SW24 are arranged in a row so as to face each other.

The input-side 1 × 4 optical switches SW11 to SW14 have four output ports P1 to P4, respectively. The output side 4 × 1 optical switches SW21 to SW24 have four input ports Q1 to Q4, respectively. In fig. 5, each port is represented by "good".

The four output ports P1 to P4 of the input side 1 × 4 optical switches SW11 to SW14 are connected to the input ports Q1 to Q4 of the different output side 4 × 1 optical switches SW21 to SW24, respectively, via the connection optical waveguide OW. In fig. 5, the connection optical waveguide OW is indicated by a solid line for simplicity.

In such a structure, since the input side 1 × 4 optical switches SW11 to SW14 and the output side 4 × 1 optical switches SW21 to SW24 are connected in a plane, a part of the connection optical waveguides OW does not intersect with other connection optical waveguides OW, but a plurality of connection optical waveguides OW intersect with other connection optical waveguides OW a plurality of times. The number of intersections of the connection optical waveguide OW with other connection optical waveguides OW is at most (N-1) × (N-1) (in the example shown in fig. 5, (4-1) × (4-1) ═ 9).

For example, in the 4 × 4 optical switch shown in fig. 5, the connection optical waveguide OW connecting the output port P1 of the input side 1 × 4 optical switch SW11 and the input port Q1 of the output side 4 × 1 optical switch SW21 does not intersect with other connection optical waveguides OW, but the connection optical waveguide OW connecting the output port P4 of the input side 1 × 4 optical switch SW11 and the input port Q1 of the output side 4 × 1 optical switch SW24 intersects with 9 connection optical waveguides OW.

Therefore, if L (dB/number of intersections) is the loss of light caused by one intersection of the connection optical waveguide OW and another connection optical waveguide OW, the loss of light caused by the intersection of the connection optical waveguide OW at the port connected to the connection optical waveguide OW (hereinafter referred to as "intersection loss") is at most L × (N-1) (dB). Specifically, when L is 0.5dB, the maximum cross loss of the port is 4.5dB when N is 4, and 24.5dB when N is 8.

In the case of an optical switch, since the intensity of output light needs to be adjusted between ports, ports other than the port to which the connection optical waveguide OW having the largest cross loss is connected need to be matched with loss values by preparing other loss sources. Therefore, it is desirable to reduce the number of intersections in the connection optical waveguide OW having the largest number of intersections with other connection optical waveguides OW.

In view of the above-described conventional technology, an object of the present invention is to provide an N × N optical switch in which an output port of an input side 1 × N optical switch and an input port of an output side N × 1 optical switch are connected to each other by a connection optical waveguide on the same substrate, and in which the number of intersections in the optical switch is the largest and the intersection loss of the port connected to the connection optical waveguide having the highest intersection loss can be reduced.

An N × N optical switch according to an embodiment of the present invention includes:

N input side 1 XN optical switches having N output ports, N being an integer of 3 or more; n output side N × 1 optical switches having N input ports; and a connecting optical waveguide connecting the output port and the input port, the N x N optical switch being characterized in that,

a part of the connection optical waveguide intersects with two or more other connection optical waveguides at one point.

In another embodiment of the present invention, an N × N optical switch is characterized in that,

the intersection of the connection optical waveguide and the other connection optical waveguides is an MMI intersection structure.

Another embodiment of the present invention provides an N × N optical switch, wherein the N × N optical switch includes a first optical waveguide and a second optical waveguide

The input side 1 × N optical switch and the output side N × 1 optical switch are arranged in a straight line such that the output port faces the input port,

The output port on one end side of the input-side 1 × N optical switch is connected to the input port on one end side of the output-side N × 1 optical switch via the connection optical waveguide that does not intersect with another connection optical waveguide,

The output port on the other end side of the input side 1 × N optical switch located on the other end side of the input side 1 × N optical switch is connected to the input port on the other end side of the output side N × 1 optical switch located on the other end side of the output side N × 1 optical switch via the connection optical waveguide not intersecting with the other connection optical waveguide,

The output port of the input-side 1 × N optical switch located on one end side of the input-side 1 × N optical switches located on the other end side is connected to the input port of the output-side N × 1 optical switch located on the other end side and different from each other among the output-side N × 1 optical switches via the connection optical waveguide intersecting with the other connection optical waveguide,

the output port of the input side 1 × N optical switch located on the other end side of the input side 1 × N optical switches located on the other end side is connected to the input port of the output side N × 1 optical switch located on the other end side of the output side N × 1 optical switches located on the other end side and different from each other via the connection optical waveguide intersecting with the other connection optical waveguide,

The output port of the input-side 1 × N optical switch located outside both ends of the input-side 1 × N optical switch is connected to the input port of the output-side N × 1 optical switch different from each other by the connection optical waveguide intersecting with the other connection optical waveguide.

In another embodiment of the present invention, an N × N optical switch is characterized in that,

the input side 1 × N optical switches and the output side N × 1 optical switches are alternately arranged side by side,

The output ports at both ends of the input-side 1 × N optical switch are connected to the input ports at the end of the output-side N × 1 optical switches adjacent to the input-side 1 × N optical switch and different from each other via the connection optical waveguide not intersecting with the other connection optical waveguides,

the output port located outside both ends of the output ports of the input-side 1 × N optical switch is connected to the input ports located outside both ends of the output-side N × 1 optical switches that are different from each other and are not adjacent to the input-side 1 × N optical switch, via the connection optical waveguide intersecting with the other connection optical waveguides.

In another embodiment of the present invention, an N × N optical switch is characterized in that,

The input side 1 × N optical switch, the output side N × 1 optical switch, and the connection optical waveguide are monolithically formed on the same semiconductor substrate.

In another embodiment of the present invention, an N × N optical switch is characterized in that,

The intersection angle of the intersection portion of the connection optical waveguide and the other connection optical waveguide is equal to the same angle.

According to the N × N optical switch of the embodiment of the present invention, in the optical switch configured by connecting the output port of the input side 1 × N optical switch and the input port of the output side N × 1 optical switch via the connection optical waveguide on the same substrate, it is possible to reduce the cross loss due to the waveguide cross in the port connected by the connection optical waveguide having the largest number of cross with other connection optical waveguides.

Drawings

Fig. 1 is a configuration diagram showing an example of a tree-shaped optical switch applied to an N × N optical switch according to an embodiment of the present invention.

Fig. 2 is a configuration diagram of an N × N optical switch according to embodiment 1 of the present invention.

Fig. 3 is a configuration diagram of an MMI cross structure showing a case where three waveguides cross.

Fig. 4 is a configuration diagram of an N × N optical switch according to embodiment 2 of the present invention.

Fig. 5 is a configuration diagram showing an example of a conventional N × N optical switch.

fig. 6 is a perspective view showing a conventional 2 × 2 optical switching element.

Fig. 7 is a configuration diagram showing another example of a conventional N × N optical switch.

Detailed Description

An N × N optical switch according to an embodiment of the present invention has a configuration in which output ports of N input side 1 × N optical switches and input ports of N output side N × 1 optical switches are connected by a connection optical waveguide formed on a substrate, the connection optical waveguide is arranged to have a waveguide intersection portion in which three or more connection optical waveguides intersect at one point, and a Multi-mode interference (MMI) intersection structure is used in a waveguide intersection portion in which the connection optical waveguide intersects with a connection optical waveguide connected between other ports.

With the above configuration, according to the N × N optical switch of the embodiment of the present invention, the number of waveguide intersection portions in one connection optical waveguide can be reduced, and intersection with low loss and low crosstalk can be realized at the waveguide intersection portions, and the loss of light due to waveguide intersection can be reduced.

Here, a tree-shaped optical switch used in an embodiment of the present invention will be described with reference to fig. 1. The optical switch is not limited to a 1 × 4 optical switch, and a 1 × 8 optical switch or a 1 × N optical switch having more than one port may be used. Here, a tree-shaped 1 × 4 optical switch will be described as a representative example.

As shown in fig. 1, the 1 × 4 optical switch SW10 is implemented by tree-like connection of 2 × 2 optical switches SW10a, SW10b, and SW10 c. The optical output is branched into four ports by being branched into two by the first 2 × 2 optical switch SW10a and further branched into two by the next 2 × 2 optical switches SW10b and SW10 c. Each of the 2 × 2 optical switches SW10a, SW10b, SW10c can be implemented using MZI, for example.

first, the 2 × 2 optical switches SW10a, SW10b, and SW10c are input to an optical waveguide (for example, OW shown in fig. 1) using a multimode interference optical coupler (hereinafter, MMI optical coupler)₁) Is branched to two optical waveguides not shown. At this time, the length of the MMI optical coupler is designed to be a length that bisects the light intensity. After the bifurcated input light receives the phase difference between the two optical waveguides, it is coupled again by the MMI optical coupler. Thus, if the phase difference between the two optical waveguides is ± n pi according to the interference effect, the input light is transmitted from the optical waveguide on the opposite side to the optical waveguide to which the input light is input (for example, OW shown in fig. 1)₂) If the output is ± (2n +1) pi/2, the output is from the optical waveguide on the same side as the optical waveguide to which the input light is input (for example, WO shown in fig. 1)₃) And outputting (wherein n is an integer).

therefore, when the phase modulation region is arranged in one of the optical waveguides and controlled, a 2 × 2 switching operation can be obtained. The phase modulation can be obtained by changing the refractive index of the optical waveguide. Therefore, the refractive index of the optical waveguide is changed by energizing a current TO the heater by a PLC or the like, by using the TO effect, by using the Franz-Keldysh (FK) effect, the Quantum Confinement Stark Effect (QCSE) effect, or the plasmon effect caused by an applied voltage in the InP-based optical waveguide, or by using the Pockels effect, and by using the Pockels effect, in the LN-based optical waveguide, the refractive index of the optical waveguide is changed, and the switching operation can be performed. Further, a directional coupler or the like may be used as an MMI optical coupler that bisects the light intensity.