WO2024164833A1 - Wavelength selective switch and related device - Google Patents

Abstract

A wavelength selective switch (WSS) (3000), comprising: a first FAU (3100) and a second FAU (3200), used for transmitting optical signals in a first polarization direction and a second polarization direction, respectively; a polarization beam combining element (3300), used for transmitting the optical signal in the first polarization direction and reflecting the optical signal in the second polarization direction, the optical signals from the first FAU (3100) and the second FAU (3200) being coupled to at least one optical switching engine (3500) by means of the polarization beam combining element (3300) and then reflected back to the polarization beam combining element (3300) by the at least one optical switching engine (3500); and a polarization rotating element (3400), located between the polarization beam combining element (3300) and the at least one optical switching engine (3500) and used for rotating a passing optical signal by 45° in a first direction. The polarization direction of the optical signal from the first FAU (3100) after passing twice through the polarization rotating element (3400) rotates by 90° in the first direction, and the optical signal is output from the second FAU (3200). The polarization direction of the optical signal from the second FAU (3200) after passing twice through the polarization rotating element (3400) rotates by 90° in the first direction, and the optical signal is output from the first FAU (3100).

Description

A wavelength selective switch and related equipment

This application claims the priority of the Chinese patent application filed with the State Intellectual Property Office on February 7, 2023, with application number 202310129664.7 and invention name “A wavelength selective switch and related equipment”, the entire contents of which are incorporated by reference in this application.

Technical Field

The embodiments of the present application relate to the field of optical communications, and in particular to a wavelength selective switch and related equipment.

Background Art

In optical transmission networks, reconfigurable optical add/drop multiplexers (ROADM) sites are used to add and drop optical signals. A commonly used ROADM site structure is to use multiple 1xN wavelength selective switches (WSS) to add and drop optical signals.

1xN WSS includes a fiber array unit (FAU) and an optical switching engine. The optical signal is input into the optical switching engine through the input port on the FAU and is output from the output port on the FAU after being switched by the optical switching engine.

There may be multiple input ports on a FAU, and there will be directional crosstalk between the multiple input ports. Directional crosstalk refers to the diffraction crosstalk signal generated by the optical signal input from a certain input port on the FAU after passing through the optical switching engine inside the WSS. The diffraction crosstalk signal is reflected by the optical switching engine to other input ports on the FAU, causing signal crosstalk between the input ports, affecting the isolation of the WSS, and further affecting the signal-to-noise ratio.

Summary of the invention

The embodiments of the present application provide a wavelength selective switch WSS and related devices for reducing directional crosstalk of the WSS.

In a first aspect, an embodiment of the present application provides a wavelength selective switch WSS, which includes: a first fiber array unit (FAU), a second FAU, a polarization beam combining element, at least one optical switching engine and a polarization rotation element. The first FAU and the second FAU are used to transmit optical signals in a first polarization direction and a second polarization direction, respectively. The polarization beam combining element is used to transmit optical signals in a first polarization direction and to reflect optical signals in a second polarization direction. The optical signals from the first FAU and the second FAU are coupled to the optical switching engine through the polarization beam combining element and reflected back to the polarization beam combining element by the optical switching engine.

In the embodiment of the present application, the polarization direction of the optical signal is rotated 90° by a polarization rotation element (non-reciprocal polarization rotation element), and the optical signal input from the first FAU is output from the second FAU in combination with the different guidance of light beams of different polarization directions by the polarization beam combining element, so that the optical signal from the second FAU is output from the first FAU. Then the diffraction crosstalk signal corresponding to a certain input port on the first FAU is output from the second FAU, and will not return to the first FAU, nor will it enter other input ports on the first FAU; the same is true for the second FAU. Therefore, no directional crosstalk will be generated between multiple input ports on the same FAU, which can improve the isolation of WSS and thus improve the signal-to-noise ratio of signal transmission.

In an optional implementation, the first optical signal is input from the first FAU and output from the second FAU. Specifically, the first FAU includes a first input port for the first optical signal, and the second FAU includes a first output port for the first optical signal.

In an optional implementation, at least one optical switching engine includes a first optical switching engine, which is used to switch the optical signal from the first FAU. The first FAU and the second FAU include a first column port and a second column port corresponding to each other, and the first column port and the second column port are arranged along the switching direction. On the first FAU, the first input port of the first optical signal includes a first port set in the first column port; on the second FAU, the first output port of the first optical signal includes a second port set in the second column port. In an embodiment of the present application, the port position corresponding to the surface normal of the first optical switching engine is referred to as the first symmetric position. Then, in the switching direction, the first port set and the first idle position are symmetric with respect to the first symmetric position, and any port in the second port set is outside the first idle position.

In the embodiment of the present application, the input port (the first port set in the first column of ports on the first FAU) and the output port (the second port set in the second column of ports on the second FAU) of the first optical signal do not have symmetrically distributed ports relative to the first symmetrical position, so that the input port and the output port of the first optical signal are isolated from each other in the switching direction. This can prevent the zero-order diffraction light corresponding to the first input port (which will be projected onto the port symmetrical to the first symmetrical position of the first input port) from hitting the first output port, causing zero-order crosstalk to the output signal, thereby solving the problem of zero-order crosstalk.

In an optional implementation, along the switching direction, the first symmetrical position is between the upper edge port and the lower edge port of the first column of ports. (WSS switches the first optical signal using a bilateral switching working mode). If the first input port is a common (COM) port, then along the switching direction, the second port set includes ports located above the first port set and ports located below the first port set. Alternatively, if the first output port is a COM port, then along the switching direction, the first port set includes ports located above the second port set and ports located below the second port set.

In the embodiment of the present application, the first optical signal is switched in a bilateral switching manner through the above port arrangement. Since bilateral switching has the advantage of a small switching angle, the switching dimension N of the WSS for the first optical signal can be made larger when the maximum switching angle supported by the optical switching engine remains unchanged.

In an optional implementation, along the switching direction, the first symmetrical position is outside the first column of ports (WSS uses a unilateral switching working mode to switch the first optical signal). If the first input port is a COM port, then along the switching direction, the first port set is distributed at the upper edge or lower edge of the first column of ports. Alternatively, if the first output port is a COM port, then along the switching direction, the second port set is distributed at the upper edge or lower edge of the second column of ports.

In the embodiment of the present application, the arrangement method is to arrange the combined wave port (COM port) at one end (upper edge or lower edge, if the first symmetrical position is above the first column of ports, then at the upper edge, otherwise at the lower edge) of the column of ports where the combined wave port is located in the switching direction, and the add/drop (AD) port (also called the split wave port) is arranged in a direction away from the COM port. Then the COM port is closest to the first symmetrical position (correspondingly, closest to the symmetry axis), which can reduce the maximum switching angle of switching from the COM port to the A/D port, thereby reducing the switching angle and improving the switching dimension N of the WSS for the first optical signal.

In an optional implementation, the switching of the two optical signals can be realized by WSS. Specifically, in addition to the first output port of the first optical signal, the second FAU can also include a second input port of the second optical signal; in addition to the first input port of the first optical signal, the first FAU can also include a second output port of the second optical signal.

In an embodiment of the present application, the input and output ports of the first optical signal and the second optical signal are integrated on the first FAU and the second FAU. The two optical signals can be integrated into one WSS for switching without generating directional crosstalk, thereby improving the integration of the WSS module.

In an optional implementation, at least one optical switch engine includes a first optical switch engine and a second optical switch engine, and the first optical switch engine and the second optical switch engine are at different heights in the switching direction. The WSS also includes a polarization separation element, which is located between the polarization rotation element and the at least one optical switch engine, and is used to project optical signals with different polarization directions to different heights in the switching direction. After the first optical signal is output from the polarization rotation element, it is projected to the first optical switch engine through the polarization separation element, and after the second optical signal is output from the polarization rotation element, it is projected to the second optical switch engine through the polarization separation element.

In an optional implementation, in the first FAU, the first input port and the second output port are located at different positions in the dispersion direction; in the second FAU, the second input port and the first output port are located at different positions in the dispersion direction.

In the embodiment of the present application, the ports of different optical signals on the first FAU (the first input port and the second output port) are arranged at different positions in the dispersion direction to separate the two optical signals in the dispersion direction. Multiple columns of ports can be arranged in the dispersion direction (the same applies to the second FAU), thereby achieving dimensional expansion in the dispersion direction and improving the module integration of the WSS.

In an optional implementation, at least one optical switching engine includes a second optical switching engine, and the second optical switching engine is used to switch the optical signal from the second FAU. The second FAU and the first FAU include a third column port and a fourth column port corresponding to each other, and the third column port and the fourth column port are arranged along the switching direction. On the second FAU, the second input port of the second optical signal includes a third port set in the third column port; on the first FAU, the second output port of the second optical signal includes a fourth port set in the fourth column port. In an embodiment of the present application, the port position corresponding to the surface normal of the second optical switching engine is referred to as the second symmetric position. Then in the switching direction, the third port set and the second idle position are symmetric with respect to the second symmetric position, and any port in the fourth port set is outside the second idle position.

In the embodiment of the present application, the input port (the third port set in the third column of ports on the second FAU) and the output port (the fourth port set in the fourth column of ports on the first FAU) of the second optical signal are not symmetrically distributed relative to the first symmetrical position, so that the input port and the output port of the second optical signal are isolated from each other in the switching direction. It can be avoided that the zero-order diffraction light corresponding to the second input port (which will be projected onto the port symmetrical to the second input port relative to the second symmetrical position) hits the second output port, causing zero-order crosstalk to the output signal, thereby solving the problem of zero-order crosstalk.

In an optional implementation, along the switching direction, the second symmetrical position is within the upper edge port and the lower edge port of the third column port (WSS switches the second optical signal in a bilateral switching mode). If the second input port is a COM port, then along the switching direction, the fourth port set includes a port located above the third port set and a port located below the third port set. Alternatively, if the second output port If the port is a COM port, then along the switching direction, the third port set includes ports located above the fourth port set and ports located below the fourth port set.

In the embodiment of the present application, the second optical signal is switched in a bilateral switching manner through the above port arrangement. Since bilateral switching has the advantage of a small switching angle, the switching dimension N of the second optical signal of the WSS can be made larger when the maximum switching angle supported by the optical switching engine remains unchanged.

In an optional implementation, along the switching direction, the second symmetrical position is outside the third column port (WSS uses a unilateral switching working mode to switch the second optical signal). If the second input port is a COM port, the third port set is distributed at the upper edge or lower edge of the third column port along the switching direction. Alternatively, if the second output port is a COM port, the fourth port set is distributed at the upper edge or lower edge of the fourth column port along the switching direction.

In the embodiment of the present application, the arrangement method is to arrange the combined wave port (COM port) at one end (upper edge or lower edge, if the second symmetrical position is above the third column port, then at the upper edge, otherwise at the lower edge) of the column of ports where the combined wave port is located in the switching direction, and the add/drop (AD) port (also called the split wave port) is arranged in a direction away from the COM port. Then the COM port is closest to the second symmetrical position (correspondingly, closest to the symmetry axis), which can reduce the maximum switching angle of switching from the COM port to the A/D port, thereby reducing the switching angle and improving the switching dimension N of the WSS for the second optical signal.

In an optional implementation, the first column port also includes a third input port of the third optical signal, and the second column port also includes a third output port of the third optical signal. The first optical switching engine is also used to switch the third optical signal. The third input port includes a fifth port set in the first column port set, and the third output port includes a sixth port set in the second column port set. In the switching direction, the fifth port set and the third idle position are symmetrical with respect to the first symmetric position, and any port in the sixth port set is outside the third idle position.

In the embodiment of the present application, the input port (the fifth port set in the first column of ports on the first FAU) and the output port (the sixth port set in the second column of ports on the second FAU) of the third optical signal are not symmetrically distributed relative to the first symmetrical position, so that the input port and the output port of the third optical signal are isolated from each other in the switching direction. It can be avoided that the zero-order diffraction light corresponding to the third input port (which will be projected onto the port symmetrical to the first symmetrical position of the third input port) hits the third output port, causing zero-order crosstalk to the output signal, thereby solving the problem of zero-order crosstalk.

Optionally, the first optical signal and the third optical signal may be projected onto the same area of the first optical switching engine, and the first optical switching engine may implement the same switching of the first optical signal and the third optical signal.

In the embodiment of the present application, the first optical switching engine is used not only to switch the first optical signal, but also to switch the third optical signal, so that the optical paths of the first optical signal and the third optical signal are the same (the arrangement of the COM port and the A/D port is opposite, that is, the wave splitting and combining states are opposite), and the first optical signal and the third optical signal are integrated on the same optical path, thereby improving the integration of the WSS.

In an optional implementation, the third column port also includes a fourth input port for a fourth optical signal, and the fourth column port also includes a fourth output port for a fourth optical signal. The second optical switch engine is also used to switch the fourth optical signal. The fourth input port includes a seventh port set in the third column port set, and the fourth output port includes an eighth port set in the fourth column port set. In the switching direction, the seventh port set is symmetrical with the fourth idle position relative to the second symmetrical position, and any port in the eighth port set is outside the fourth idle position.

Optionally, the second optical signal and the fourth optical signal may be projected onto the same area of the second optical switching engine, and the second optical switching engine may implement the same switching of the second optical signal and the fourth optical signal.

In the embodiment of the present application, the second optical switch engine is used not only to switch the second optical signal, but also to switch the fourth optical signal, so that the optical paths of the second optical signal and the fourth optical signal are the same (the arrangement of the COM port and the A/D port is opposite, that is, the wave splitting and combining states are opposite), and the second optical signal and the fourth optical signal are integrated on the same optical path, thereby improving the integration of the WSS.

In an optional implementation, at least one optical switching engine includes a target optical switching engine, and the first switching area and the second switching area of the target optical switching engine are at different heights in the switching direction. The first switching area is used to switch the optical signal from the first FAU, and the second switching area is used to switch the optical signal from the second FAU. The WSS also includes a polarization separation element, which is located between the polarization rotation element and the target optical switching engine. The polarization separation element is used to project optical signals of different polarization directions to different switching heights of the optical switching engine at different angles. Specifically, after the optical signal from the first FAU is output from the polarization rotation element, it is projected to the first switching area at a first angle through the polarization separation element, and after the optical signal from the second FAU is output from the polarization rotation element, it is projected to the second switching area at a second angle through the polarization separation element.

In an embodiment of the present application, different optical signals are projected onto different switching areas of the optical switching engine at different angles through a polarization separation element, so that the WSS can switch two optical signals in different directions (the optical signal from the first FAU and the optical signal from the second FAU) in different working modes (for example, one in a unilateral switching mode and the other in a bilateral switching mode), thereby improving the flexibility of the WSS working mode.

In an optional implementation, at least one optical switching engine includes a first optical switching engine and a second optical switching engine. The first optical switching engine is used to switch the optical signal from the first FAU, and the second optical switching engine is used to switch the optical signal from the second FAU. In the switching direction, there is a first angle between the first switching engine and the second switching engine.

In an embodiment of the present application, a first angle is provided between the two optical switching engines, so that the two optical signals can be incident on the two optical switching engines at different angles, so that the WSS switches the two optical signals in different directions (the optical signal from the first FAU and the optical signal from the second FAU) in different working modes (for example, one in a unilateral switching mode and the other in a bilateral switching mode), thereby improving the flexibility of the WSS working mode.

In an optional implementation, at least one optical switch engine includes a first optical switch engine and a second optical switch engine. The first optical switch engine is used to switch an optical signal of a first channel from a first FAU, and the second optical switch engine is used to switch an optical signal of a first channel from a second FAU. In the dispersion direction, a position of the first channel on the first optical switch engine is different from a position of the first channel on the second optical switch engine.

In a second aspect, an embodiment of the present application further provides a reconfigurable optical branching multiplexer (ROADM) site, wherein the ROADM site includes the WSS described in the first aspect.

The beneficial effects of the second aspect refer to the first aspect and will not be repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the ROADM site architecture of the present application;

FIG2 is a schematic diagram of directional crosstalk of the present application;

FIG3 is a schematic diagram of the structure of a WSS provided in an embodiment of the present application;

FIG4 is a schematic diagram of a non-reciprocal polarization rotation element provided in an embodiment of the present application;

FIG5 is a schematic diagram of zero-order crosstalk of the present application;

FIG6 is a schematic diagram of a port arrangement for solving zero-order crosstalk provided by an embodiment of the present application;

FIG7 is a schematic diagram of bilateral switching and unilateral switching of the present application;

FIG8 is a schematic diagram of a FAU port arrangement of a bilateral switching method provided in an embodiment of the present application;

FIG9 is a schematic diagram of another FAU port arrangement of the bilateral switching method provided in an embodiment of the present application;

FIG10 is a schematic diagram of a FAU port arrangement of a unilateral switching method provided in an embodiment of the present application;

FIG11 is a schematic diagram showing an advantageous arrangement of ports in a unilateral switching manner provided in an embodiment of the present application;

FIG12 is a schematic diagram of a WSS structure in which two columns of ports are arranged on a FAU according to an embodiment of the present application;

FIG13 is a schematic diagram of the FAU port arrangement for bilateral switching of two optical signals provided in an embodiment of the present application;

FIG14 is a schematic diagram of the FAU port arrangement for unilateral switching of two optical signals provided in an embodiment of the present application;

FIG15 is a schematic diagram of the FAU port arrangement for unilateral switching of one optical signal and bilateral switching of one optical signal provided in an embodiment of the present application;

FIG16 is a schematic diagram of the structure of a polarization separation element for two optical signals with different emission angles provided in an embodiment of the present application;

FIG17 is a schematic diagram of a WSS structure with an angle between two optical switch engines provided in an embodiment of the present application;

FIG18 is a schematic diagram of the FAU port arrangement in which two optical signals provided in an embodiment of the present application are both unilaterally switched and the symmetrical positions of the two optical signals are different;

FIG19 is a schematic diagram of the FAU port arrangement of two optical signals bound in switching states provided in an embodiment of the present application;

FIG20 is a schematic diagram of the structure of a ROADM site provided in an embodiment of the present application;

FIG21 is a schematic diagram of the FAU port arrangement for unilateral switching of four optical signals provided in an embodiment of the present application.

DETAILED DESCRIPTION

The embodiments of the present application are described below in conjunction with the accompanying drawings. It is known to those skilled in the art that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged in appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attribute in the embodiments of the present application when describing. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment containing a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment. In addition, "at least one" refers to one or more, and "multiple" refers to two or more. "And/or", describes the association relationship of associated objects, indicating that three relationships can exist, for example, A and/or B, can represent: A exists alone, A and B exist simultaneously, and B exists alone, wherein A, B can be singular or plural. The character "/" generally represents that the associated objects before and after are a kind of "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or plural.

In an optical transmission network, optical signals can be added and dropped through ROADM sites. A commonly used ROADM site structure is shown in Figure 1, which includes multiple 1xN WSSs, through which optical signals can be added and dropped.

1xN WSS includes a fiber array unit FAU and an optical switch engine. The optical signal is input into the optical switch engine through the input port on the FAU, and after being switched by the optical switch engine, it is output from the output port on the FAU. For WSS, the problem of directional crosstalk is an important factor that limits the isolation of WSS.

The problem of directional crosstalk occurs in multiple input ports on a FAU. After the optical signal input from a certain input port on the FAU passes through the optical switching engine inside the WSS, a diffraction crosstalk signal will be generated. The diffraction crosstalk signal is reflected by the optical switching engine to other input ports on the FAU, which will cause signal crosstalk between the input ports, affecting the isolation of the WSS and further affecting the signal-to-noise ratio.

For example, as shown in Figure 2, the common (COM) port 1 and COM port 2 on the FAU are the combined wave ports of the WSS, and the optical signal is input into the optical switch engine from these two ports. The add/drop (A/D) ports 1 to 3 are split wave ports, and the optical signal is output from these three split wave ports after being switched by the optical switch engine. Then, the input optical signal on COM port 1 will generate a diffraction crosstalk signal corresponding to COM port 1 after passing through the optical switch engine. The interference signal is reflected to COM port 2 by the optical switch engine, and crosstalk to COM port 2 will be generated.

It is worth noting that FIG2 uses the COM port (combined wave port) as the input port and the A/D port as the output port, which is only an example. The COM port can also be an output port, and the corresponding A/D port is an input port, which is not limited in this application. If the A/D port is an input port, the problem of directional crosstalk can occur between multiple A/D/ports.

It is worth noting that FIG. 2 is only an example of the FAU port of WSS, and does not limit the number of COM ports, the number of A/D/ports, the port arrangement, etc.

In order to solve the above-mentioned directional crosstalk problem, the embodiment of the present application provides a WSS and related equipment. As shown in FIG3 , the WSS 3000 provided in the embodiment of the present application includes: a first FAU 3100, a second FAU 3200, a polarization beam combining element 3300, a polarization rotation element 3400 and an optical switching engine 3500.

The first FAU 3100 is used to transmit an optical signal in a first polarization direction (the first polarization direction is indicated by a dashed line in FIG3 ), and the second FAU 3200 is used to transmit an optical signal in a second polarization direction (the second polarization direction is indicated by a dotted line in FIG3 ). The polarization beam combining element 3300 is used to transmit an optical signal in the first polarization direction and reflect an optical signal in the second polarization direction.

As shown in Figure a of Figure 3, the optical signal (polarization direction is the first polarization direction) input from the first FAU 3100 is transmitted by the polarization beam combining element 3300. The optical signal (polarization direction is the second polarization direction) input from the second FAU 3200 is reflected by the polarization beam combining element 3300. The optical signal from the first FAU 3100 and the optical signal from the second FAU are coupled into a light beam after passing through the polarization beam combining element 3300, and the light beam is projected to the optical switching engine 3500 after passing through the polarization rotation element 3400. The optical switching engine 3500 reflects the light beam back to the polarization beam combining element 3300. Therefore, the light beam returning to the polarization beam combining element 3300 passes through the polarization rotation element 3400 twice.

In the embodiment of the present application, the polarization rotation element 3500 is also called a non-reciprocal polarization rotation element, which has different effects on optical signals passing through different directions. For example, a 1/2 wave plate is a typical reciprocal polarization rotation element. The polarization direction of the optical signal passing through the 1/2 wave plate in the forward direction will rotate by 90°, and the polarization direction of the optical signal passing through the 1/2 wave plate in the reverse direction will rotate by 90°, returning to the state before passing through the 1/2 wave plate for the first time.

However, the non-reciprocal polarization rotation element (polarization rotation element 3500) provided in the embodiment of the present application has different effects in the forward direction and the reverse direction. The optical signal will not return to the state before it first passed through the polarization rotation element, but the effects of the two directions will be superimposed on each other.

For example, as shown in FIG4 , when the optical signal passes through the polarization rotation element 3400 from left to right, the polarization direction of the optical signal rotates 45° clockwise; when the optical signal passes through the polarization rotation element 3400 again from right to left, the polarization direction of the optical signal rotates another 45° clockwise. Compared to before the optical signal passes through the polarization rotation element 3400 for the first time, the polarization direction of the optical signal rotates 90°.

It is worth noting that the clockwise rotation is only an example, and the direction of rotation may also be counterclockwise, as long as the two rotations of the polarization direction act in the same direction, and the present application does not impose any limitation on this.

Optionally, the polarization rotation element 3500 may be a Faraday rotator. In addition, the polarization rotation element 3500 may also be other active devices, such as an active metasurface structure, etc.; as long as the polarization direction of the input optical signal can be rotated and the rotation effects of optical signals input in different directions will not cancel each other, this application does not limit this.

Therefore, in FIG. 3 b, after the optical signal from the first FAU 3100 passes through the polarization rotation element 3400 twice, the polarization direction is rotated by 90°, and becomes a light beam in the second polarization direction (the dotted line in the figure indicates that its polarization direction is the second polarization direction). Since the polarization beam combining element 3300 reflects the light beam in the second polarization direction, the optical signal from the first FAU 3100 passes through the polarization rotation element 3400 twice, is reflected by the polarization beam combining element 3300, and is output from the second FAU 3200.

Similarly, in FIG. 3 b, after the optical signal from the second FAU 3200 passes through the polarization rotation element 3400 twice, the polarization direction is rotated by 90°, and becomes a light beam in the first polarization direction (the dot-dash line in the figure indicates that its polarization direction is the first polarization direction). Since the polarization beam combining element 3300 transmits the light beam in the first polarization direction, the optical signal from the second FAU 3200 passes through the polarization rotation element 3400 twice, is transmitted by the polarization beam combining element 3300, and is output from the first FAU 3100.

In the embodiment of the present application, the first polarization direction and the second polarization direction are perpendicular to each other. With respect to the polarization beam combining element 3300, the light beam in the first polarization direction may be P light, and the light beam in the second polarization direction may be S light; or vice versa, which will not be described in detail here.

For example, if the light beam in the first polarization direction is P light relative to the polarization beam combining element 3300, and the light beam in the second polarization direction is S light relative to the polarization beam combining element 3300. Then the first optical signal is input from the first FAU 3100 in the form of P light, and after being transmitted through the polarization beam combining element 3300, it passes through the polarization rotation element 3400, the optical switching engine 3500 and the polarization rotation element 3400 in sequence, and the polarization direction is rotated by 90° twice through the polarization rotation element 3400 to become S light, which is then reflected by the polarization beam combining element 3300 and output from the second FAU 3200. The second optical signal is input from the second FAU 3200 in the form of S light and output from the first FAU 3100 in the form of P light. The optical path is similar and will not be described here.

In the embodiment of the present application, the polarization direction of the optical signal is rotated 90° by the polarization rotation element 3400 (non-reciprocal polarization rotation element), and the polarization beam combining element 3300 guides the light beams with different polarization directions differently, so that the optical signal input from the first FAU is output from the second FAU, and the optical signal from the second FAU is output from the first FAU.

If the input port and output port of an optical signal (such as the first optical signal or the second optical signal) are respectively set on different FAUs, the diffraction crosstalk signal generated by the optical signal from an input port on the FAU projected onto the optical switching engine will be transmitted to another FAU along with the output signal, and will not return to the FAU where the input port is located, and will not generate crosstalk to other input ports. For example, the diffraction interference signal corresponding to a certain input port on the first FAU 3100 is output from the second FAU 3200, and will not return to the first FAU 3100, and will not enter other input ports on the first FAU 3100; the same is true for the second FAU 3200. Therefore, there will be no directional crosstalk between multiple input ports on the same FAU, which can improve the isolation of the WSS, thereby improving the signal-to-noise ratio of signal transmission.

Optionally, in addition to the above components, WSS 3000 may also include other devices, such as gratings and lenses in FIG3 , which are not limited in this application. Since gratings, lenses and other devices are common structures of WSS, this application does not describe them in detail.

In the embodiment of the present application, the optical signal passes through the polarization rotation element 3400 in the forward direction (toward the optical switch engine 3500) and then passes through the polarization rotation element 3400 in the reverse direction (away from the optical switch engine 3500), so that the polarization direction of the optical signal is rotated by 90°. In the embodiment of the present application, as long as the polarization direction of the optical signal is rotated by 90° after passing through the polarization rotation element 3400 twice, the specific rotation method is not limited.

In addition to the case where the polarization direction of the optical signal passing through the polarization rotation element 3400 in both the forward and reverse directions is rotated by 45° along the first direction as shown in FIG4 , the polarization rotation element 3400 may also produce different rotation effects on the optical signals passing through the two directions. For example, the polarization direction of the optical signal passing through the forward direction may be rotated by 90°, and the polarization direction of the optical signal passing through the reverse direction may be rotated by 0° (or vice versa); or the polarization direction of the optical signal passing through the forward direction may be rotated by 30° along the first direction, and the polarization direction of the optical signal passing through the reverse direction may be rotated by 60° (or vice versa). It is limited to 60° in the forward direction + 30° in the reverse direction. As long as it passes twice, the result of the polarization rotation element 3400 rotating the polarization direction of the optical signal is superimposed to 90°), etc. This application does not make any limitation on this.

In the embodiment of the present application, a column of ports may be provided on the first FAU 3100 and the second FAU 3200, respectively, to implement the switching of one optical signal; two columns of ports may be provided on the first FAU 3100 and the second FAU 3200, respectively, to implement the switching of two optical signals; or the switching of two optical signals bound in switching state may be implemented on a column of ports, so as to improve the integration of WSS. Different numbers of port columns and different switching states will affect the distribution of ports, which will be explained in detail below.

1. A column of ports is distributed on each of the two FAUs to realize the switching of one optical signal.

In the embodiment of the present application, in addition to solving the directional crosstalk problem between multiple input ports, the zero-order crosstalk problem can also be solved by arranging the input ports and output ports on the FAU. As shown in FIG5 , the optical signal is input from the common (COM) port, splits and is switched by the optical switching engine, and is output from any port from the add/drop (AD) port (also called the split wave port) 1 to the A/D/port 4.

In the embodiment of the present application, the surface normal of the optical switching engine is called the symmetry axis, and the port position corresponding to the symmetry axis is called the symmetry position. Then, in the switching direction, the input port of the optical signal and the output port of the zero-order diffracted light of the optical signal are symmetrical relative to the symmetry position.

For example, as shown in FIG5 , the symmetrical position is the position of A/D port 2 on the FAU. The optical signal is input from the COM port, and the zero-order diffraction light corresponding to the COM port is output from the symmetrical A/D port 4. The optical signal input from the COM port may include optical signals of multiple different channels (optical signals of different channels have different central wavelengths). According to the deployment of the optical path, optical signals of different channels can be switched to any port from A/D port 1 to A/D port 4 by the optical switching engine. Then, when the optical signal of a certain channel is switched to A/D port 4, the zero-order diffraction light will cause crosstalk to the optical signal of this channel, which is the reason for the generation of zero-order crosstalk.

In the embodiment of the present application, the input port and the output port of an optical signal are arranged on different FAUs, and the zero-order diffraction light corresponding to the input signal will be projected onto the port column where the output port is located. On the port column where the output port is located, as long as the output port is arranged outside the position where the zero-order diffraction light can reach (the position where the zero-order diffraction light can reach is also called an idle position), it can be avoided that the zero-order diffraction light causes zero-order crosstalk to the output signal.

Next, taking the input and output ports of the first optical signal as an example, it is explained how the embodiment of the present application avoids zero-order crosstalk through the distribution of ports.

As shown in FIG6 , the first FAU 3100 includes a first input port for the first optical signal, and the second FAU 3200 includes a first output port for the first optical signal. The first FAU 3100 and the second FAU 3200 include first column ports and second column ports that correspond one to one (for example, in FIG6 , ports 1 to 8 on the two columns of ports correspond one to one), and the first column ports and the second column ports are arranged along the switching direction.

The optical switch engine 3500 may include a first optical switch engine 3510, and the first optical switch engine 3510 is used to switch the optical signal (e.g., the first optical signal) from the first FAU 3100. The first column port and the second column port correspond to the same switching area of the first optical switch engine 3510. In the embodiment of the present application, the port position corresponding to the surface normal of the first optical switch engine 3510 is called the first symmetric position. For example, in Figure 6, the first symmetric position is between port 4 and port 5.

On the first FAU 3100, the first input port of the first optical signal includes the first port set in the first column of ports. As shown in FIG6 , the first port set (i.e., the first input port) is port 2 and port 3 on the first column of ports. Then, in the switching direction, with the first symmetrical position as the symmetry center, the first input port (the first port set, i.e., port 2 and port 3 in the first column of ports) on the first FAU 3100 and the first idle position (i.e., port 6 and port 7 in the second column of ports) on the second FAU 3200 are symmetrical to each other. From the above description of zero-order crosstalk, it can be seen that when the first optical signal is input from the first input port, the zero-order diffraction light corresponding to the incident light will be emitted from the port on the first idle position, i.e., from port 6 and port 7 in the second column of ports.

On the second FAU 3200, the first output port of the first optical signal includes the second port set in the second column of ports. As long as the ports in the second port set (first output port) are all outside the first idle position, the zero-order diffraction light can be prevented from entering the output port of the first optical signal. In this way, the zero-order crosstalk of the first optical signal can be avoided, the isolation of the WSS can be improved, and the signal-to-noise ratio of the first optical signal can be improved.

For example, in FIG. 6 , the first output port (the second port set) can be located at any position among ports 1 to 5 and port 8 in the second column of ports, as long as it is not located at port 6 and port 7 (the first idle position).

In the embodiment of the present application, the working state of the optical switch engine (also the working state of the optical signal corresponding to the optical switch engine switched by the WSS) can be divided into bilateral switching and unilateral switching according to the different distribution states between the symmetrical positions and ports corresponding to the optical switch engine. The following will explain them one by one.

In the embodiment of the present application, in addition to the COM port and the A/D port, the FAU may also include other ports, such as a DUMMY port, which is not limited in the present application.

In WSS, the optical switch engine is used to switch the optical signal between ports, thereby realizing the uplink and downlink of the optical signal. Specifically, different ports correspond to different switching angles of the optical switch engine. The optical switch engine can change the transmission port of the optical signal by changing the switching angle of the optical signal, thereby realizing the switching of the optical signal between different ports.

As shown in Figure a of FIG7 , if the port position corresponding to the surface normal of the optical switching engine (referred to as the symmetry axis in this application) is located between the upper edge port and the lower edge port of a column of ports (i.e., a column of ports on the FAU where the input port or output port corresponding to the optical switching engine is located), it is a bilateral switching working mode. For example, in Figure a of FIG7 , the upper edge port and the lower edge port are A/D port 1 and A/D port N, respectively. As long as the symmetric position is between A/D port 1 and A/D port N, it is a bilateral switching working mode. In existing technical solutions, the bilateral switching method usually has the problem of zero-order crosstalk, so it is rarely used.

As shown in Figure 7 (b), if the port position corresponding to the surface normal of the optical switch engine (referred to as the symmetry axis in this application) is located outside a column of ports (i.e., a column of ports where the input port or output port corresponding to the optical switch engine is located on the FAU), it is a single-sided switching working mode. For example, in Figure 7 (b), the ports are arranged from the COM port to the A/D port N, then as long as the symmetric position is above the COM port or below the A/D port N, it is a single-sided switching working mode.

1.1. Port arrangement for bilateral switching.

Based on the port arrangement for preventing zero-order crosstalk shown in FIG6, the ports can be arranged in a bilateral switching arrangement as shown in FIG8. As shown in FIG8, along the switching direction, the first symmetrical position is within the upper edge port and the lower edge port of the first column port, and is also within the upper edge port and the lower edge port of the second column port (WSS can use the bilateral switching working mode to switch the first optical signal).

In the embodiment of the present application, the first optical signal is switched in a bilateral switching manner through the above port arrangement. Since bilateral switching has the advantage of a small switching angle, the switching dimension N of the WSS for the first optical signal can be made larger when the maximum switching angle supported by the optical switching engine remains unchanged.

Optionally, as shown in Figure a of FIG8 , the first port set (first input port) on the first FAU 3100 may be a COM port (combined wave port), and the second port set on the second FAU 3200 may be an A/D port (splitting wave port). Alternatively, as shown in Figure b of FIG8 , the first port set may be an A/D port and the second port set may be a COM port, which is not limited in the present application. In the embodiments of the present application, a thin line circle may represent an unused port or a blank area (i.e., no port exists), which is not limited in the present application.

In order to realize bilateral switching, along the switching direction, the A/D port should include ports distributed on the upper and lower sides of the COM port. As shown in Figure a of Figure 8, if the first symmetrical position is at the center of the first column of ports (also the center of the second column of ports), and the first port set (COM port) includes port 4 and port 5 on the first column of ports, then the first idle position is on port 4 and port 5 on the second column of ports (the first port set and the first idle position are symmetrical about the first symmetrical position). Therefore, the second port set only needs to be not on port 4 and port 5. Along the switching direction, the second port set (the first output port, which is also the A/D port) is distributed on both sides of the first port set (the first input port, which is also the COM port). It is also possible to distribute the first port set (the first input port, which is also the A/D port) on both sides of the second port set (the first output port, which is also the COM port) along the switching direction as shown in Figure b of Figure 8, and this application does not limit this.

In an embodiment of the present application, the number of COM ports may be more or less than the two in FIG. 8 , and the present application does not limit this. The two COM ports in FIG. 8 are just symmetrically distributed along the first symmetrical position. Optionally, the COM ports may not be symmetrically distributed along the first symmetrical position. For example, as shown in FIG. 9 , if the first input port (first port set) is a COM port, and is on port 3 and port 4 of the first column of ports. Then the corresponding first idle position is on port 5 and port 6 of the second column of ports. Therefore, the second port set only needs to be not on port 5 and port 6. Therefore, port 3 and port 4 on the second column of ports can also be used as the first output port. In other words, the first port set and the second port set may include corresponding ports (for example, ports 3 and 4 in the first column of ports, and ports 3 and 4 in the second column of ports), and the present application does not limit this.

Through the port distribution of bilateral switching provided in the embodiment of the present application, the zero-order diffraction light can be projected to the unused port of the output port or a blank position (i.e., a position where no port exists), thereby avoiding the crosstalk between ports caused by the zero-order diffraction light. The embodiment of the present application solves the port crosstalk problem of zero-order diffraction light of bilateral switching, making the bilateral switching method an available working method of WSS. Compared with the traditional unilateral switching working method, the switching angle of bilateral switching is smaller (the maximum switching angle that needs to be supported by the optical switching engine is δ*N/2, which is smaller than δ*N of unilateral switching, where δ is the switching angle between adjacent ports), and the switching capacity of the optical switching engine remains unchanged (i.e., the maximum switching angle supported The switching dimension N of WSS 300 (1xN WSS) can be increased while the switching angle remains unchanged.

1.2 Port arrangement for unilateral switching.

In one implementation, the ports on the first FAU 3100 and the second FAU 3200 can be arranged so that the WSS 3000 can operate in a unilateral switching manner, thereby achieving dimensional expansion in the dispersion direction.

Based on the port arrangement for preventing zero-order crosstalk shown in FIG6, the ports can be arranged in a unilateral switching arrangement as shown in FIG10. As shown in FIG10, along the switching direction, the first symmetrical position is outside the first column of ports and outside the second column of ports (WSS can switch the first optical signal in a unilateral switching working mode).

Optionally, as shown in Figure 10 a, the first port set (first input port) on the first FAU 3100 can be a COM port (wave combining port), and the second port set on the second FAU 3200 can be an A/D port (wave splitting port). Alternatively, as shown in Figure 10 b, the first port set is used as an A/D port and the second port set is used as a COM port, which is not limited in this application.

In order to achieve unilateral switching, along the switching direction, the COM ports should be distributed at one end (upper edge or lower edge) of a column of ports. As shown in Figure a of Figure 10, if along the switching direction, the first symmetrical position is above the second column of ports (also above the second column of ports), the first port set (the first input port, which is also the COM port) can be distributed at the upper edge of the first column of ports. Since the first symmetrical position is above the first column of ports, the first idle position is above the second column of ports (the first port set and the first idle position are symmetrical about the first symmetrical position). Therefore, the second port set (the first output port) can include any port in the second column of ports.

Alternatively, as shown in FIG. 10 b, the first port set (first input port, also A/D port) can be distributed at the lower edge of the first column of ports along the switching direction. Since the first symmetrical position is below the second column of ports, the first idle position is below the second column of ports (the first port set and the first idle position are symmetrical about the first symmetrical position). Therefore, the second port set (first output port) can include any port in the second column of ports.

For example, as shown in Figure a of FIG10 , if the first input port (first port set) is a COM port and is on port 1 and port 2 of the first column of ports. Since the corresponding first idle position is above the second column of ports, the second port set can be any port in the second column of ports. Therefore, port 1 and port 2 on the second column of ports can also be used as the first output port. In other words, the first port set and the second port set can include corresponding ports (e.g., ports 1 and 2 in the first column of ports, and ports 1 and 2 in the second column of ports).

That is to say, through the structure provided by the embodiment of the present application, in the unilateral switching working mode, the A/D port can include a port corresponding to the COM port. As shown in Figure 11, compared with the existing unilateral switching structure (the COM port and the A/D port are arranged in the same column of the same FAU, and there is no A/D port corresponding to the COM port), the embodiment of the present application expands the number of A/D ports, thereby expanding the switching dimension N of the WSS in the case of unilateral switching.

2. Two columns of ports are distributed on both FAUs to realize the switching of two optical signals with decoupled switching states.

Optionally, in the embodiment of the present application, two columns of ports may be respectively provided on the first FAU 3100 and the second FAU 3200, so as to realize the transmission of two optical signals. The two optical signals include a first optical signal and a second optical signal, and the transmission directions of the two optical signals in the WSS 300 are opposite. Specifically, the first FAU 3100 is used to realize the input of the first optical signal and the output of the second optical signal, and the second FAU 3200 is used to realize the input of the second optical signal and the output of the first optical signal.

2.1. Both optical signals are switched in a bilateral switching manner.

The corresponding structure is shown in FIG12. The optical fiber array 1 and the polarization processing unit in FIG12 constitute the first FAU 3100, and the optical fiber array 2 and the polarization processing unit constitute the second FAU 3200. The first optical signal is input from the first FAU 3100 (optical fiber array 1) and output from the second FAU 3200 (optical fiber array 2). For the specific optical path, refer to the description of the optical path of the optical signal from the first FAU 3100 in the embodiment of FIG3. The first optical signal is input from the second FAU 3200 (optical fiber array 2) and output from the first FAU 3100 (optical fiber array 1). For the specific optical path, refer to the description of the optical path of the optical signal from the second FAU 3200 in the embodiment of FIG3.

In this structure, the first optical signal from the first FAU 3100 (fiber array 1) and the second optical signal from the second FAU 3200 (fiber array 2) are projected to different heights of the optical switch engine along the switching direction through the polarization separation unit located between the non-reciprocal polarization rotation element and the optical switch engine. For example, the first optical signal is projected to the switching height corresponding to the first switching area in the lower right corner of FIG. 12, and the first optical signal is switched through the first switching area of the optical switch engine; the second optical signal is projected to the switching height corresponding to the second switching area, and the second optical signal is switched through the second switching area of the optical switch engine.

Optionally, the first optical signal and the second optical signal may be switched by switching a first optical switching engine (corresponding to the position of the first switching area in FIG. 12 ) and a second optical switching engine (corresponding to the position of the second switching area in FIG. 12 ) of different heights, and the present application does not disclose the switching of the first optical signal and the second optical signal. Make limitations.

Since the first column port and the fourth column port on the first FAU 3100 are in different positions in the dispersion direction, the corresponding optical switching engines (the first optical switching engine and the second optical switching engine) or switching areas (the first switching area and the second switching area) will have a certain misalignment in the dispersion direction.

As shown in the lower right corner of Figure 12, if the first switching area is used to switch the optical signal of the first channel from the first FAU 3100 (for example, the light spot with a central wavelength of λ1 in the figure, in the embodiment of the present application, different channels correspond to light spots with different central wavelengths on the optical switching engine), the second switching area is used to switch the optical signal of the first channel from the second FAU. Then in the dispersion direction, the position of the first channel (for example, the light spot with a central wavelength of λ1 in the figure) on the first switching area is different from the position of the first channel on the second switching area. The misalignment of the first channel on different optical switching engines is the same as the above-mentioned misalignment on different optical switching areas, which will not be repeated here.

Since the switching areas corresponding to the first optical signal and the second optical signal are different on the optical switch engine, the switching states of the first optical signal and the second optical signal are decoupled from each other. Therefore, the distribution of the ports corresponding to the first optical signal (the first input port and the first output port) is also decoupled from the distribution of the ports corresponding to the second optical signal (the second input port and the second output port).

The specific port distribution is shown in FIG. 13 , where the first FAU 3100 may include a first column of ports and a fourth column of ports distributed along the switching direction, and the second FAU 3200 may include a second column of ports and a third column of ports distributed along the switching direction. The first column of ports corresponds to the second column of ports one by one, and the third column of ports corresponds to the fourth column of ports one by one.

The first port set on the first column port is the first input port of the first optical signal, the second port set on the second column port is the first output port of the first optical signal. The third port set on the third column port is the input port of the second optical signal, and the fourth port set on the fourth column port is the second output port of the second optical signal.

For the first column of ports and the second column of ports, please refer to the description of the embodiments shown in FIG. 6 to FIG. 11 , which will not be described in detail here.

The second input port of the second optical signal may include a second port set on the third column of ports, and the second output port of the second optical signal may include a fourth port set on the fourth column of ports. For the port position relationship between the second input port and the second output port, the port distribution under unilateral switching, the port distribution under bilateral switching, the corresponding COM port or A/D port, etc., please refer to the description of the first input port and the first output port in the embodiments shown in Figures 6 to 11, which will not be repeated here.

It is worth noting that the port distributions corresponding to the two optical signals can be decoupled from each other. Therefore, as shown in Figure 13, the first input port is an A/D port (the corresponding first output port is a COM port), and the second input port is a COM port (the corresponding second output port is an A/D port); or the first input port and the second input port are both A/D ports; or the first input port and the second input port are both COM ports, etc. This application does not limit this.

In an embodiment of the present application, the input and output ports of the first optical signal and the second optical signal are integrated on the first FAU and the second FAU. The two optical signals can be integrated into one WSS for switching without generating directional crosstalk, thereby improving the integration of the WSS module.

2.2. Both optical signals are switched in a unilateral switching manner.

FIG13 is an example of the distribution of ports when both optical signals are switched bilaterally. If both optical signals are switched unilaterally, the specific port distribution is shown in FIG14. It is worth noting that the port distributions corresponding to the two optical signals can be decoupled from each other, so as shown in FIG14, the first input port and the second input port are both COM ports (the corresponding first output port and the second output port are both A/D ports); or the first input port and the second input port are both A/D ports; or the first input port is a COM port and the second input port is an A/D port, etc., and this application does not limit this.

Optionally, as shown in FIG. 14 , the first symmetrical position and the second symmetrical position can be both above the FAU, so that the COM port of the first optical signal and the COM port of the second optical signal are both at the upper edge of the column of ports in which they are located; or the two symmetrical positions can be both below the FAU, so that the COM port of the first optical signal and the COM port of the second optical signal are both at the lower edge of the column of ports in which they are located, and the present application does not impose any limitation on this.

2.3. Of the two optical signals, one optical signal is switched in a bilateral switching manner, and the other optical signal is switched in a unilateral switching manner.

Optionally, for the two optical signals of WSS, one optical signal may adopt a unilateral switching working mode, and the other optical signal may adopt a bilateral switching working mode, and the corresponding port arrangement may be as shown in FIG. 15 .

As shown in FIG. 15, the first input port and the first output port of the first optical signal are respectively distributed in the first column port and the second column port. The ports in the two columns can be arranged in a port arrangement corresponding to the bilateral switching. For details, see the description of the embodiments shown in FIG. 8 and FIG. 9. The third column port and the fourth column port are respectively distributed with the second input port and the second output port of the second optical signal, and the ports in the two columns can be arranged in a port arrangement manner corresponding to unilateral switching, as shown in the embodiments shown in FIG. 10 and FIG. 11, which will not be described here.

Optionally, the ports in the first column and the second column may be arranged in a unilateral switching manner, and the ports in the third column and the fourth column may be arranged in a bilateral switching manner, which is not limited in the present application.

In an embodiment of the present application, the optical signal (including the first optical signal and the second optical signal) from the non-reciprocal polarization rotation element can be projected at different angles to different switching heights (i.e., different heights in the switching direction) of the optical switching engine through a polarization separation element, so that the angles between the two optical signals and the symmetry axis of the optical switching engine are different, so that the first symmetric position and the second symmetric position are distributed at different positions of the FAU, thereby realizing unilateral switching of one optical signal and bilateral switching of one optical signal.

Optionally, the optical switching engine may include a target optical switching engine, and the first switching area and the second switching area of the target optical switching engine are at different heights in the switching direction. The polarization separation element can project optical signals of different polarization directions to different switching heights of the optical switching engine at different angles. Specifically, after the first optical signal is output from the polarization rotation element, it is projected to the first switching area at a first angle through the polarization separation element, and after the second optical signal is output from the polarization rotation element, it is projected to the second switching area at a second angle through the polarization separation element. As a result, the first angle θ1 between the first optical signal and the target optical switching engine and the second angle θ2 between the second optical signal and the target optical switching engine are different. If θ1 is not equal to θ2, the first symmetrical position and the second symmetrical position can be distributed at different positions of the FAU to achieve unilateral switching of one optical signal and bilateral switching of one optical signal.

The structure of the polarization separation element may be as shown in FIG16, including a polarization splitting surface, a first reflection surface and a second reflection surface. The polarization splitting surface is used to reflect the light signal in the third polarization direction and transmit the light signal in the fourth polarization direction. The third polarization direction and the fourth polarization direction are perpendicular to each other.

For example, the optical signal from the polarization rotation element 3400 includes the optical signal from the first FAU 3100 and the optical signal from the second FAU 3200. If the optical signal from the first FAU 3100 is S light relative to the polarization splitting plane, and the optical signal from the second FAU 3200 is P light relative to the polarization splitting plane. As shown in FIG16 , the polarization splitting plane reflects the optical signal (S light) from the first FAU 3100 to the first reflection plane, and transmits the optical signal from the second FAU 3200 to the second reflection plane. Optionally, the polarization splitting plane may also reflect the optical signal from the second FAU 3200 and transmit the optical signal from the first FAU 3100, and the present application does not limit this.

The first reflection surface includes a 1/4 wave plate. After the optical signal from the first FAU is reflected by the first reflection surface, the polarization direction is rotated 90° and becomes an optical signal (P light) with a fourth polarization direction, which can be transmitted from the polarization splitting surface and projected onto the first switching area of the optical switch engine at a first angle (θ1). The second reflection surface reflects the optical signal from the second FAU and projects it onto the second switching area of the optical switch engine at a second angle (θ2).

In an embodiment of the present application, different optical signals are projected onto different switching areas of the optical switching engine at different angles through a polarization separation element, so that the WSS can switch two optical signals in different working modes (for example, one in a unilateral switching mode and the other in a bilateral switching mode), thereby improving the flexibility of the WSS working mode.

Optionally, two optical switching engines placed at different angles can be used to switch different optical signals in different working modes. Specifically, the optical switching engine 3500 includes a first optical switching engine 3510 and a second optical switching engine 3520. The first optical switching engine 3510 is used to switch the optical signal from the first FAU, and the second optical switching engine 3520 is used to switch the optical signal from the second FAU. As shown in FIG17 , in the switching direction, there is a first angle α between the first switching engine 3510 and the second switching engine 3520. Then the optical signal (including the first optical signal and the second optical signal) from the polarization rotation element 3400 (non-reciprocal polarization rotation element) has different angles with the symmetry axis of the first switching engine and the symmetry axis of the second switching engine, so that the first symmetric position and the second symmetric position can be distributed at different positions of the FAU, so as to realize unilateral switching of one optical signal and bilateral switching of one optical signal.

In an embodiment of the present application, a first angle is provided between the two optical switching engines, so that the two optical signals can be incident on the two optical switching engines at different angles, so that the WSS switches the two optical signals in different working modes (for example, one in a unilateral switching mode and the other in a bilateral switching mode), thereby improving the flexibility of the WSS working mode.

Optionally, as shown in FIG. 18 , through the structure shown in FIG. 16 or FIG. 17 , the first symmetrical position and the second symmetrical position are respectively located above and below the FAU. When both paths are switched on one side, the COM ports of the two paths are distributed on different edges of the FAU (one upper edge and one lower edge). For example, as shown in FIG. 18 , the first symmetrical position is located above the first column port and the second column port, and the second symmetrical position is located below the third column port and the fourth column port. The COM port of the first optical signal can be at the upper edge, and the COM port of the second optical signal can be at the lower edge. The reverse is also possible, and the present application does not limit this.

3. A column of ports is distributed on each of the two FAUs to realize the switching of two optical signals whose switching states are bound to each other.

Optionally, two optical signals may be transmitted on one column of ports, and the two optical signals are switched through the same optical switch engine or the same switching area of the optical switch engine, so the switching states of the two optical signals are bound to each other.

For example, as shown in FIG19, the first column port also includes a third input port of the third optical signal, and the second column port also includes a third output port of the third optical signal. The first optical switching engine (or the first switching area) is used to switch the first optical signal and the third optical signal. The third input port includes the fifth port set in the first column port set, and the third output port includes the sixth port set in the second column port set. In the switching direction, the fifth port set is symmetrical with the third idle position relative to the first symmetrical position, and any port in the sixth port set is outside the third idle position.

For example, as shown in FIG19, the third input port includes ports 3-8 on the first column of ports. Since the first symmetrical position is above the first column of ports (and also above the second column of ports), the third idle position is above the second column of ports. The third output port can be any port in the second column of ports, and this application does not limit this. For example, it can be ports 1-2 on the second column of ports as shown in FIG19, or it can be any other port on the second column of ports.

In the embodiment of the present application, the first optical switching engine is used not only to switch the first optical signal, but also to switch the third optical signal, so that the optical paths of the first optical signal and the third optical signal are the same (the arrangement of the COM port and the A/D port is opposite, that is, the wave splitting and combining states are opposite), and the first optical signal and the third optical signal are integrated on the same optical path, thereby improving the integration of the WSS.

The port distribution shown in FIG19 can be applied to the ROADM site structure shown in FIG20. As shown in FIG20, the switching states of the Kx1WSS on the west side (W side in the figure) and the 1xK WSS on the west side (W side in the figure) are bound to each other, so the ports on the W side can be distributed in the same two columns of ports (for example, if the first optical signal corresponds to the third optical signal, the first input port and the third input port are both distributed in the first column of ports, and the third output port and the first output port are both distributed in the second column of ports), realizing the mutual binding of the switching states of the two optical signals.

4. Two columns of ports are distributed on both FAUs to realize the switching of three or four optical signals.

Optionally, the first optical signal and the second optical signal can also be transmitted on two columns of ports, and the first optical signal and the third optical signal are switched through the same optical switching engine or the same switching area of the optical switching engine, and the second optical signal and the fourth optical signal are switched through the same optical switching engine or the same switching area of the optical switching engine, so that the switching states of the first optical signal and the third optical signal are bound to each other, and the switching states of the second optical signal and the fourth optical signal are bound to each other.

For example, as shown in FIG21, the first column port also includes a third input port of the third optical signal, and the second column port also includes a third output port of the third optical signal. The first optical switching engine (or the first switching area) is used to switch the first optical signal and the third optical signal. The third input port includes the fifth port set in the first column port set, and the third output port includes the sixth port set in the second column port set. In the switching direction, the fifth port set is symmetrical with the third idle position relative to the first symmetrical position, and any port in the sixth port set is outside the third idle position.

The third column port also includes a fourth input port for a fourth optical signal, and the fourth column port also includes a fourth output port for a fourth optical signal. The second optical switching engine (or the second switching area) is used to switch the second optical signal and the fourth optical signal. The fourth input port includes a seventh port set in the third column port set, and the fourth output port includes an eighth port set in the fourth column port set. In the switching direction, the seventh port set is symmetrical with the fourth idle position relative to the second symmetrical position, and any port in the eighth port set is outside the fourth idle position.

In the embodiment of the present application, the switching of four optical signals is realized by two optical switching engines, which improves the optical switching dimension of WSS and thus improves the integration of WSS.

Optionally, in the structure shown in FIG21, only two optical signals may be integrated. For example, the first column port and the second column port realize the input and output of the first optical signal and the third optical signal, while the third column port and the fourth column port only realize the input and output of the second optical signal, and the fourth optical signal is not integrated in the optical path of the second optical signal (that is, the third input port and the third output port in the figure are not used); similarly, the third input port and the third output port may be used, and the fourth input port and the fourth output port may not be used, and this application does not limit this.

In the example of FIG. 21 , the first symmetrical position and the second symmetrical position are both arranged above the FAU, and the COM ports are arranged at the upper edge. Optionally, the two symmetrical positions can also be arranged below the FAU, and the COM ports can be arranged at the lower edge of the FAU. Alternatively, the structure shown in FIG. 16 or 17 can be used to make the first symmetrical position and the second symmetrical position one arranged above the FAU and the other arranged below the FAU. Below the FAU, one COM port is distributed on the upper edge and one COM port is distributed on the lower edge, which is not limited in the present application.

The embodiment of the present application further provides a ROADM site, which includes the WSS in any of the above embodiments. Optionally, the ROADM site may also be referred to as a ROADM subrack, which is not limited in the present application.

Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

Claims (16)

A wavelength selective switch WSS, characterized by comprising a first fiber array unit FAU, a second FAU, a polarization beam combining element, at least one optical switching engine and a polarization rotation element: The first FAU and the second FAU are used to transmit optical signals in a first polarization direction and optical signals in a second polarization direction, respectively; The polarization beam combining element is used to transmit optical signals of a first polarization direction and reflect optical signals of a second polarization direction; the optical signals from the first FAU and the second FAU are coupled to the at least one optical switching engine through the polarization beam combining element and then reflected back to the polarization beam combining element by the at least one optical switching engine; The polarization rotation element is located between the polarization beam combining element and the at least one optical switching engine, and is used to rotate the passing optical signal by 45° along the first direction; After the optical signal from the first FAU passes through the polarization rotation element twice, its polarization direction is rotated 90° along the first direction and is output from the second FAU; after the optical signal from the second FAU passes through the polarization rotation element twice, its polarization direction is rotated 90° along the first direction and is output from the first FAU. The WSS according to claim 1, characterized in that the first FAU includes a first input port for a first optical signal, and the second FAU includes a first output port for the first optical signal. The WSS according to claim 2, wherein the at least one optical switch engine comprises a first optical switch engine, the first optical switch engine being used to switch the optical signal from the first FAU; The first FAU and the second FAU include a first column port and a second column port corresponding to each other, and the first column port and the second column port are arranged along the switching direction; The first input port includes a first port set in the first column of ports, and the first output port includes a second port set in the second column of ports; in the switching direction, the first port set is symmetrical to the first idle position relative to the first symmetric position, and any port in the second port set is outside the first idle position; wherein the first symmetric position is the port position corresponding to the surface normal of the first optical switching engine. The WSS according to claim 3, characterized in that, along the switching direction, the first symmetrical position is within the upper edge port and the lower edge port of the first column of ports: If the first input port is a common COM port, then along the switching direction, the second port set includes ports located above the first port set and ports located below the first port set; or, If the first output port is a COM port, then along the switching direction, the first port set includes ports located above the second port set and ports located below the second port set. The WSS according to claim 3, characterized in that, along the switching direction, the first symmetrical position is outside the first column port; If the first input port is a common COM port, then along the switching direction, the first port set is distributed at the upper edge or the lower edge of the first column of ports; or, If the first output port is a COM port, then along the switching direction, the second port set is distributed at the upper edge or the lower edge of the second column of ports. The WSS according to any one of claims 2 to 5, characterized in that the second FAU includes a second input port for a second optical signal, and the first FAU includes a second output port for the second optical signal. The WSS according to claim 6, characterized in that: In the first FAU, the first input port and the second output port are located at different positions in a dispersion direction; In the second FAU, the second input port and the first output port are located at different positions in the dispersion direction. The WSS according to claim 6 or 7, characterized in that the at least one optical switch engine includes a second optical switch engine, and the second optical switch engine is used to switch the optical signal from the second FAU; The second FAU and the first FAU include a third column port and a fourth column port corresponding to each other, and the third column port and the fourth column port are arranged along the switching direction; The second input port includes a third port set in the third column of ports, and the second output port includes a fourth port set in the fourth column of ports; in the switching direction, the third port set is symmetrical with the second idle position relative to the second symmetric position, Any port in the fourth port set is outside the second idle position; wherein the second symmetrical position is a port position corresponding to a surface normal of the second optical switch engine. The WSS according to claim 8, characterized in that, along the switching direction, the second symmetrical position is within the upper edge port and the lower edge port of the third column of ports; If the second input port is a common COM port, then along the switching direction, the fourth port set includes ports located above the third port set and ports located below the third port set; or, If the second output port is a COM port, then along the switching direction, the third port set includes ports located above the fourth port set and ports located below the fourth port set. The WSS according to claim 8, characterized in that, along the switching direction, the second symmetrical position is outside the third column port: If the second input port is a common COM port, then along the switching direction, the third port set is distributed at the upper edge or the lower edge of the third column of ports; or, If the second output port is a COM port, then along the switching direction, the fourth port set is distributed at the upper edge or the lower edge of the fourth column of ports. The WSS according to any one of claims 3 to 10, characterized in that the first column port also includes a third input port for a third optical signal, and the second column port also includes a third output port for the third optical signal; the first optical switching engine is further used to switch the third optical signal; The third input port includes the fifth port set in the first column port set, and the third output port includes the sixth port set in the second column port set; in the switching direction, the fifth port set and the third idle position are symmetrical with respect to the first symmetric position, and any port in the sixth port set is outside the third idle position. The WSS according to any one of claims 8 to 11, characterized in that the third column port also includes a fourth input port for a fourth optical signal, and the fourth column port also includes a fourth output port for the fourth optical signal; the second optical switch engine is further used to switch the fourth optical signal; The fourth input port includes the seventh port set in the third column port set, and the fourth output port includes the eighth port set in the fourth column port set; in the switching direction, the seventh port set and the fourth idle position are symmetrical with respect to the second symmetric position, and any port in the eighth port set is outside the fourth idle position. The WSS according to any one of claims 1 to 12, characterized in that the at least one optical switching engine includes a target optical switching engine, the first switching area and the second switching area of the target optical switching engine are at different heights in the switching direction; the first switching area is used to switch the optical signal from the first FAU, and the second switching area is used to switch the optical signal from the second FAU; the WSS further includes: A polarization separation element, located between the polarization rotation element and the target optical switch engine, for projecting optical signals of different polarization directions to different switching heights of the optical switch engine at different angles; After the optical signal from the first FAU is output from the polarization rotation element, it is projected to the first switching area at a first angle through the polarization separation element. After the optical signal from the second FAU is output from the polarization rotation element, it is projected to the second switching area at a second angle through the polarization separation element. The WSS according to any one of claims 1 to 12, characterized in that the at least one optical switch engine comprises a first optical switch engine and a second optical switch engine, the first optical switch engine is used to switch the optical signal from the first FAU, and the second optical switch engine is used to switch the optical signal from the second FAU; In the switching direction, there is a first angle between the first switching engine and the second switching engine. The WSS according to any one of claims 1 to 14, characterized in that the at least one optical switch engine comprises a first optical switch engine and a second optical switch engine, the first optical switch engine is used to switch the optical signal of the first channel from the first FAU, and the second optical switch engine is used to switch the optical signal of the first channel from the second FAU; In the dispersion direction, a position of the first channel on the first optical switch engine is different from a position of the first channel on the second optical switch engine. A reconfigurable optical add/drop multiplexer (ROADM) site, comprising the WSS according to any one of claims 1 to 15.