1. A wavelength division multiplexing device for demultiplexing or multiplexing light beams of N wavelengths, the wavelength division multiplexing device comprising a filtering unit, a lens and an optical transmission unit;

wherein the content of the first and second substances,

the optical transmission unit is used for transmitting 1 beam of input light beams with N wavelengths or N beams of input light beams with different wavelengths to the filtering unit after being collimated by a lens;

the optical filtering unit is configured to demultiplex or multiplex the collimated 1 beam of input light beams with N wavelengths or the collimated N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths, and the N beams of output light beams are converged to the optical transmission unit through the lens.

2. The wavelength division multiplexing device according to claim 1, wherein the filter unit includes N filters that are not parallel to each other;

each filter is used for reflecting the light beam with any wavelength in the N wavelengths and transmitting the light beams with other wavelengths except any wavelength in the N wavelengths;

different filters reflect different wavelengths of the light beam.

3. The wdm device of claim 2, wherein different filters in the filtering units are in different rotation states, so that different light beams demultiplexed by different filters can be converged into different optical fibers distributed on the light incident surface of the optical transmission unit through the lens;

or different optical filters in the optical filtering unit are in different rotating states, so that different light beams are multiplexed by the different optical filters and then are converged into the optical fiber at the center of the light incidence surface of the optical transmission unit through the lens.

4. The WDM device according to claim 3, wherein the rotation states include a rotation angle and a rotation direction, and the different filters are rotated along the rotation axis by the respective rotation angles based on the rotation direction to be in different rotation states.

5. The wavelength division multiplexing device of claim 3,

the rotation direction and the rotation angle of the optical filter in the rotation state are related to the distribution of each optical fiber in the optical transmission unit on the light incident surface or the light emergent surface.

6. The WDM device according to claim 3, wherein any two filters have different rotation angles and/or rotation directions when they are in different rotation states.

7. The wavelength division multiplexing device according to any one of claims 3 to 6,

the rotation angle is an included angle between a central axis of the optical filter and an optical axis of the optical transmission unit.

8. The wavelength division multiplexing device according to claim 7, wherein the rotation angle is related to a vertical distance between a convergence point corresponding to the optical filter and an optical axis of the optical transmission unit; the converging point corresponding to the optical filter refers to a light spot formed on a light incident surface of the optical transmission unit after the optical filter is converged by the lens when the optical filter is demultiplexed, or refers to a light spot for emitting the corresponding light beam on a light emitting surface of the optical transmission unit when the optical filter multiplexes the corresponding light beam.

9. The wavelength division multiplexing device according to claim 8, wherein the rotation angle is in relation to a vertical distance between a convergence point corresponding to the optical filter and an optical axis of the optical transmission unit;

y＝f×tan(2α)；

y is the vertical distance between a convergence point corresponding to the optical filter and the optical axis of the optical transmission unit, f is the focal length of the lens, and alpha is the rotation angle.

10. The wavelength division multiplexing device according to any one of claims 3 to 6,

the rotation direction refers to an axial direction of the rotation shaft along which the optical filter rotates by a certain rotation angle along the rotation shaft based on the rotation direction; wherein the rotation axis is perpendicular to the optical axis of each optical fiber in the optical transmission unit.

11. The wavelength division multiplexing device of claim 10,

the rotating direction corresponds to the axial direction of the rotating shaft and is vertical to the direction vector of the shaft where the vertical distance between the convergence point corresponding to the optical filter and the optical axis of the optical transmission unit is located;

the converging point corresponding to the optical filter refers to a light spot formed on a light incident surface of the optical transmission unit after the optical filter is converged by the lens when the optical filter is demultiplexed, or refers to a light spot for emitting the corresponding light beam on a light emitting surface of the optical transmission unit when the optical filter multiplexes the corresponding light beam.

12. The wavelength division multiplexing device according to any one of claims 2 to 11, wherein the N filters are arranged in a collinear distribution.

13. The wavelength division multiplexing device of any one of claims 2 to 11, wherein each optical filter is disposed along a main optical axis of the wavelength division multiplexing device.

14. The wavelength division multiplexing device according to any one of claims 2 to 11, wherein the filters are disposed along the axis of the lens.

15. The wdm device according to any one of claims 1-14, wherein the optical transmission unit comprises 1 first optical fiber for transmitting the light beams of N wavelengths simultaneously and N second optical fibers for transmitting the light of any one wavelength.

16. The wavelength division multiplexing device according to claim 15, wherein the optical axis directions of any two optical fibers in the optical transmission unit are arranged in parallel.

17. The wdm device of claim 15, wherein the N second fibers are uniformly distributed about the first fiber.

18. The wdm device of claim 15, wherein the first optical fiber is coaxial with a principal optical axis of the wdm device.

19. The wdm device of claim 15, wherein the first optical fiber and the lens are coaxially disposed.

20. The wdm device of any one of claims 1-19, wherein said lens comprises one or more of a spherical lens, an aspherical lens, or a self-focusing lens.

21. The wdm device of any one of claims 1-19, wherein the light entrance face and the light exit face of the light delivery unit are located at the focal plane of the lens.

22. The wdm device of any one of claims 1-19, wherein said lens is coaxial with a principal optical axis of said wdm device.

23. The wavelength division multiplexing device according to any one of claims 1 to 22, wherein the abutting surface is at a predetermined angle with respect to an optical axis of the lens when the lens and the optical transmission unit are disposed in abutment.

24. A wavelength selective switch comprising the wavelength division multiplexing device as claimed in any one of claims 1 to 22, and a control device;

the control device is used for controlling the filtering unit to demultiplex or multiplex 1 beam of input light beams with N wavelengths or N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths.

25. The wavelength selective switch of claim 24, wherein when the filter unit comprises N filters, each filter is used for reflecting the light beam with any one of the N wavelengths and transmitting the light beams with other wavelengths except any one of the N wavelengths, and different filters reflect the light beams with different wavelengths,

the control equipment is used for controlling different optical filters to be in different rotating states so that different light beams demultiplexed by the different optical filters can be converged into different optical fibers distributed on the light incidence surface of the light transmission unit through the lens; or, the control device is configured to control different optical filters to be in different rotation states, so that different optical filters collimate different light beams to the optical fiber in the center of the light incident surface of the optical transmission unit after multiplexing the light beams.

Background

A Wavelength Division multiplexing device (Wavelength Division Multiplexer, WDM for short) is a key device in an optical communication system. In order to increase the amount of communication data and save fiber resources, WDM is often used at the data transmitting end and the data receiving end.

The existing WDM structure generally includes two types, one is a WDM based on a thin film filter, and the other is a WDM based on a Planar Lightwave Circuit (PLC). However, both of the above-mentioned WDM types have drawbacks:

the WDM based on the thin film filter is composed of a flat glass and a plurality of thin film filters, and is limited by a coating process when the thin film filters are coated, and when the wavelength difference between channels is smaller, the requirement for the incident angle of light incident to the WDM is higher, and the device volume is correspondingly increased. The WDM based on Planar Lightwave Circuit (PLC) uses an Array Waveguide Grating (AWG) structure, and both the input and output ends thereof need to be coupled by using lenses, so that the total loss of the device is greatly increased, and the signal quality of the optical communication system is reduced.

How to provide high quality WDM for optical communication systems has become a major research focus.

Disclosure of Invention

The application provides a wavelength division multiplexing device and a wavelength selection switch for improving the signal quality of an optical communication system.

In a first aspect, the present application provides a wavelength division multiplexing device for demultiplexing or multiplexing light beams of N wavelengths, the wavelength division multiplexing device including a filtering unit, a lens, and an optical transmission unit; the optical transmission unit transmits 1 beam of input light beams with N wavelengths or N beams of input light beams with different wavelengths to the filtering unit after being collimated by the lens; the light filtering unit demultiplexes or multiplexes the collimated 1 beam of input light beams with N wavelengths or the collimated N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths, and the N beams of output light beams are converged to the light transmission unit through the lens.

According to the scheme provided by the embodiment, the lens is additionally arranged in the wavelength division multiplexing device, so that the loss generated when the device is coupled to an optical communication system is reduced.

In one possible design, the filter unit includes N filters that are not parallel to each other; each filter is used for reflecting the light beam with any wavelength in the N wavelengths and transmitting the light beams with other wavelengths except any wavelength in the N wavelengths; different filters reflect different wavelengths of the light beam.

In a possible design, different filters in the filtering unit are in different rotation states, so that different light beams demultiplexed by different filters can be converged into different optical fibers distributed on the light incident surface of the light transmission unit through the lens; or different optical filters in the optical filtering unit are in different rotating states, so that different light beams are multiplexed by the different optical filters and then are converged into the optical fiber at the center of the light incidence surface of the optical transmission unit through the lens.

In one possible design, the N filters are arranged in a collinear distribution.

In one possible design, each optical filter is distributed along a main optical axis of the wavelength division multiplexing device.

In one possible design, the filters are distributed along the optical axis of the lens.

Through the scheme provided by the embodiment, the optical paths do not interfere with each other, the wavelength division multiplexing device can be kept in a smaller volume range under the condition that the number of channels is increased, and the incident light beam of the device has no strict requirement.

In one possible design, the optical transmission unit includes 1 first optical fiber for simultaneously transmitting light beams of N wavelengths and N second optical fibers for transmitting light of any one wavelength.

In one possible design, the optical axis directions of any two optical fibers in the optical transmission unit are arranged in parallel.

In one possible design, the N second optical fibers are uniformly distributed about the first optical fiber.

In one possible design, the first optical fiber is coaxial with a main optical axis of the wavelength division multiplexing device.

In one possible design, the first optical fiber and the lens are arranged coaxially.

By the scheme provided by the embodiment, the light incident surface and the light emergent surface of the wavelength division multiplexing device are the same plane, and dense wavelength division multiplexing in a small volume is realized.

In one possible design, the lens includes one or more of a spherical lens, an aspherical lens, or a self-focusing lens.

In one possible embodiment, the light entry surface and the light exit surface of the light transmission unit are located in the focal plane of the lens.

In one possible design, the lens is coaxial with a principal optical axis of the wavelength division multiplexing device.

In a possible design, when the lens and the light transmission unit are attached to each other, the attaching surface and the optical axis of the lens form a predetermined angle.

Through the scheme provided by the embodiment, the incident light beam and the emergent light beam share the lens, and the volume of the device is further reduced.

In a second aspect, the present application provides a wavelength selective switch comprising a wavelength division multiplexing device for implementing the first aspect, and a control device;

the control device is used for controlling the filtering unit to demultiplex or multiplex 1 beam of input light beams with N wavelengths or N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths.

In one possible design, when the filter unit includes N filters, each filter is used for reflecting the light beam with any one of the N wavelengths and transmitting the light beams with other wavelengths except any one of the N wavelengths, and different filters reflect the light beams with different wavelengths,

the control equipment is used for controlling different optical filters to be in different rotating states so that different light beams demultiplexed by the different optical filters can be converged into different optical fibers distributed on the light incidence surface of the light transmission unit through the lens; or, the control device is configured to control different optical filters to be in different rotation states, so that different optical filters collimate different light beams to the optical fiber in the center of the light incident surface of the optical transmission unit after multiplexing the light beams.

In the above aspects, the lens is additionally arranged in the wavelength division multiplexing device, so that the loss generated when the device is coupled to the optical communication system is reduced, and the signal quality of the optical communication system is further improved.

Drawings

FIG. 1 is a schematic diagram of a prior art thin film filter based wavelength division multiplexing device;

FIG. 2 is a schematic structural diagram of a planar optical waveguide-based wavelength division multiplexing device;

fig. 3 is a schematic structural diagram of a wavelength division multiplexing device provided in the present application;

FIG. 4a is a schematic cross-sectional view of an optical fiber of a 6-channel wavelength division multiplexing device according to the present application;

FIG. 4b is a schematic cross-sectional fiber distribution diagram of a 12-channel wavelength division multiplexing device according to the present application;

FIG. 4c is a schematic cross-sectional view of an optical fiber of an 18-channel wavelength division multiplexing device according to the present application;

FIG. 5a is a first schematic diagram illustrating a rotation state of the optical filter according to the present application;

FIG. 5b is a second schematic diagram illustrating a rotation state of the optical filter according to the present application;

fig. 6a is a schematic diagram of a first optical path of the optical filter provided in the present application at different rotation angles;

fig. 6b is a schematic diagram of a second optical path of the optical filter provided in the present application at different rotation angles;

fig. 6c is a schematic diagram of a third optical path of the optical filter provided in the present application at different rotation angles;

FIG. 7 is a schematic diagram of optical paths of the optical filter of the present application in different positions under the same rotation state;

FIG. 8a is a schematic cross-sectional view of the optical path of the filter provided in the present application under different rotation axes;

FIG. 8b is a perspective view of the optical path of the optical filter provided in the present application under different rotation axes;

FIG. 9a is a schematic cross-sectional view of an optical path of the optical filter provided in the present application in different rotation states;

fig. 9b is a schematic perspective view of an optical path of the optical filter provided in the present application in different rotation states;

FIG. 10a is a schematic side view of a structure of a wavelength division multiplexing device;

FIG. 10b is a schematic top view of a structure of a wavelength division multiplexing device;

FIG. 11a is a schematic view of the fiber distribution of a 4-channel system;

FIG. 11b is a schematic diagram of a 4-channel system with filters in different rotation states;

FIG. 11c is a schematic side view of the optical path of a 4-channel system;

FIG. 11d is a schematic top view of the optical path of a 4-channel system;

FIG. 12a is a schematic view of the fiber distribution of an 8-channel system;

FIG. 12b is a schematic view of the rotation axis of the filter of an 8-channel system under different rotation states;

FIG. 12c is a schematic diagram of the optical path of an 8-channel system;

fig. 13 is a schematic structural diagram of a wavelength selective switch provided in the present application;

fig. 14 is a schematic diagram illustrating a correspondence relationship between an optical fiber, an optical filter, and a wavelength in a wavelength selective switch according to the present application.

Detailed Description

Hereinafter, embodiments of the present embodiment will be described in detail with reference to the accompanying drawings. In the description of the embodiments herein, "/" means "or" unless otherwise specified, for example, a/B may mean a or B; "and/or" herein is merely an association describing an associated object, and means that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality" means two or more than two.

A Wavelength Division multiplexing device (WDM) is a key device in an optical communication system, and multichannel transceiving is one of important ways to improve the transmission rate of the optical communication system. In order to increase the amount of transmitted data as much as possible and save fiber resources, WDM is often used at the data transmitting end and the data receiving end.

The existing WDM structure generally includes two types, one is a WDM based on a thin film filter, and the other is a WDM based on a Planar Lightwave Circuit (PLC).

Fig. 1 is a schematic diagram showing a structure of a wavelength division multiplexing device based on thin film filters in the prior art, and as shown in fig. 1, the structure is implemented based on thin film filters, and includes a flat glass 10 and a plurality of thin film filters 11 to 14. The film layers of the thin film filters 11 to 14 are made of different light-transmitting materials, so that the film layers of the thin film filters 11 to 14 can be used for transmitting light beams with wavelengths of lambda 1 to lambda 4 and reflecting light beams with other wavelengths respectively.

Taking a demultiplexing process as an example, when incident light λ with multiple wavelengths (λ 1 to λ 4) is collimated and then enters the flat glass 10 of the wavelength division multiplexing device, the incident light λ is transmitted to the thin film filter 14, and a light beam with the wavelength of λ 4 in the incident light is transmitted from a coating layer of the thin film filter 14 and exits the wavelength division multiplexing device; the light beams having wavelengths λ 1, λ 2, and λ 3 of the incident light are reflected on the coating layer of the thin film filter 14 and transmitted to the other end surface of the plate glass 10.

Due to the difference in medium between the plate glass 10 and the air, at the other end face of the plate glass 10, light beams having wavelengths λ 1, λ 2, and λ 3 are reflected to be transmitted to the thin film filter 13.

Similarly, a light beam having a wavelength λ 3 in the incident light is transmitted through the coating layer of the thin film filter 13 and exits the wavelength division multiplexing device; the light beams with the wavelengths λ 1 and λ 2 of the incident light continue to be reflected on the coating layer of the thin film filter 13 and are transmitted to the other end surface of the plate glass 11. The transmission of the light beams having wavelengths λ 1 and λ 2 is similar to that described above.

Finally, the incident light λ will be demultiplexed into four outgoing beams of light with wavelengths λ 1, λ 2, λ 13 and λ 4, and respectively emitted from the corresponding thin film filters, the outgoing beams of light should be collimated light.

The multiplexing process is the inverse process of the demultiplexing process, and the principle and the optical path are similar and are not described herein again.

However, the present invention is limited to the coating process when coating the thin film filters, and when the wavelength difference between the channels to which each thin film filter belongs is smaller, the requirement for the incident angle of the light incident to the WDM is higher, that is, the required incident angle of the light is smaller, and the device volume is correspondingly increased, and generally, in the existing product, the minimum channel interval is about 4.5nm, the corresponding device volume is about 4mm 5mm 1mm, and the light incident angle is 8.5 °.

In addition, for the number of channels, the number of the channels increases by 2 times for each increase of the number of the channels, which makes the tolerance requirement of the whole system become more and more strict. For example, for a 4-channel device as shown in FIG. 1, the sheet glass needs to have an included angle of less than 0.2 between its two faces. Thus, the continued increase in the number of channels makes device processing increasingly impractical.

Fig. 2 is a schematic structural diagram of a wavelength division multiplexing device based on planar optical waveguides, and as shown in fig. 2, the structure is implemented based on a Grating, one side of the structure is N ports 21 for transmitting 1 wavelength, the other side of the structure is 1 port 22 for transmitting multiple wavelengths, and the ports on the two sides of the structure are connected through an Arrayed Waveguide Grating (AWG) 23 structure 23. Generally, in the demultiplexing process, one side of 1 port 22 will be used as the light beam input end, and one side of N ports 21 will be used as the light beam output end; in the multiplexing process, one side of its N ports 21 will be the beam input end and one side of its 1 port 22 will be the beam output end.

Whichever side is used as the beam input end or the beam output end, it needs to be coupled through lens coupling, that is, the light beam to be input is focused to be input into the arrayed waveguide grating through the input end, and the output light beam is focused or collimated so that the output light beam can be used.

On one hand, the array waveguide grating brings 3dB insertion loss; on the other hand, the above coupling process will further increase the insertion loss of the whole device, and the total loss after coupling reaches 5 dB. Therefore, such a structure would make coupling of the optical beams difficult, and the insertion loss is large, resulting in degradation of signal quality.

Based on the above-mentioned existing structure and the drawbacks of the existing structure, a new wavelength division multiplexing device is needed to improve the problems of the existing wavelength division multiplexing structure.

In order to improve the signal quality of an optical communication system and reduce the coupling difficulty and the signal loss of a wavelength division multiplexing device when the wavelength division multiplexing device is coupled to the optical communication system, the wavelength division multiplexing device provided by the application comprises a filtering unit, a lens and an optical transmission unit. Compared with the existing wavelength division multiplexing device, the light incident or emergent from the wavelength division multiplexing device is not required to be collimated or converged by adding the lens, but can be directly used, so that the problem of large insertion loss caused by multiple coupling of the light incident or emergent from the wavelength division multiplexing device is effectively solved. In addition, no matter incidence or emergence, the treatment can be carried out through the same lens, and the incidence surface and the emergence surface are positioned on the same plane, so that the volume of the whole device is well compressed, and the device is convenient to use.

The wavelength division multiplexing device provided by the present application will be specifically described below:

fig. 3 is a schematic structural diagram of a wavelength division multiplexing device provided in the present application, and as shown in fig. 3, the wavelength division multiplexing device includes a filtering unit 31, a lens 32, and an optical transmission unit 33.

And an optical transmission unit 33, configured to transmit 1 input beam with N wavelengths or N input beams with different wavelengths to the filtering unit 31 after being collimated by the lens 32.

The filtering unit 31 is configured to demultiplex or multiplex the collimated 1 beam of input light beams with N wavelengths or the collimated N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths, and focus the N beams of output light beams to the optical transmission unit 33 through the lens 32.

Specifically, in the light multiplexing process, the light transmission unit 33 transmits N input light beams with different wavelengths to the lens 32, and the lens 32 collimates the input light beams to form N parallel light beams with different wavelengths; the parallel lights enter the filter unit 31 and are combined into 1 beam of parallel light with different wavelengths under the action of the filter unit 31; the 1 beam of parallel light is retransmitted to the lens 32 by the filter unit 31, and at this time, the lens 32 will condense the beam of parallel light to form 1 beam of condensed light including different wavelengths, which is transmitted to the light transmission unit 33 and output from the light transmission unit 33.

In the light demultiplexing process, the light transmission unit 33 transmits 1 input light beam including different wavelengths to the lens 32, and collimates the 1 input light beam by using the lens 32 to form 1 parallel light beam including different wavelengths; the parallel light enters the filtering unit 31, and is split under the action of the filtering unit 31 to form N parallel light beams, wherein each parallel light beam corresponds to different wavelengths; the N parallel light beams are retransmitted to the lens 32 by the filtering unit 31, and at this time, the lens 32 respectively condenses the N parallel light beams to respectively form N condensed light beams, which are transmitted to the optical transmission unit 33 and output from the optical transmission unit 33.

The filtering unit 31 may be configured to combine N beams of light with different wavelengths to obtain 1 beam of light with different wavelengths, and may also be configured to split 1 beam of light with different wavelengths to obtain N beams of light with different wavelengths, where the number of wavelengths that the filtering unit 31 may be configured to process is N.

As an alternative embodiment, the lens 32 includes one or more of a spherical lens, an aspherical lens, or a self-focusing lens. That is, the lens 32 may be composed of a single type of lens, or may be composed of multiple types of lenses, whichever configuration is required to meet the light collimation and concentration requirements of the lens 32 in the present application.

As an alternative embodiment, the light entrance surface and the light exit surface of the light transmission unit 33 are located in the focal plane of the lens 32. Specifically, in order to maximize the optical signal transmission efficiency and ensure that as much light as possible enters the optical transmission unit 33 or exits from the optical transmission unit 33 to the lens 32, in the present application, a manner in which the light incident surface and the light exit surface of the optical transmission unit 33 are located at the focal plane of the lens 32 may be adopted.

Alternative embodiments, lens 32 is coaxial with the primary optical axis of the wavelength division multiplexing device in order to ensure that the light is compact as a path and has a small optical length.

Meanwhile, in order to make the layout of the whole device more compact and facilitate the compression of the whole volume of the whole device, in one possible implementation mode, an arrangement mode that whether the light is output or input is processed through the lens 32 is adopted. In other words, the optical input direction and the optical output direction may be located on the same side of the wavelength division multiplexing device.

In an alternative embodiment under the above concept, the light incident surface and the light exit surface of the light transmission unit 33 may be the same end surface to make the layout compact by multiplexing the end surfaces.

Specifically, a plurality of optical fibers may be disposed on the end face of the optical transmission unit 33, and based on demultiplexing or multiplexing of light, a part of the optical fibers may be used to transmit the input light beam to the lens 32, and another part of the optical fibers may be used to receive the output light beam transmitted by the lens 32.

Further, considering that there are a single wavelength light beam and a multi-wavelength light beam among the transmitted light beams, the optical transmission unit 33 may include 1 first optical fiber 331 and N second optical fibers 332, the first optical fiber 331 may be used to simultaneously transmit light beams of N wavelengths, and the second optical fiber 332 may be used to transmit light of any one wavelength.

As an alternative embodiment, the optical axis directions of any two optical fibers in the optical transmission unit 33 are both arranged in parallel. That is, regardless of the first optical fiber 331 or the second optical fiber 332, any two optical fibers can be disposed in a distribution in which the optical axes are parallel to each other, so as to ensure that the light entering the optical fibers is maximized while sharing the same end face. Wherein the optical axis direction of the optical fiber is a direction along the center of the optical fiber core.

In addition, since the optical transmission unit 33 includes 1 first optical fiber 331 and N second optical fibers 332, the distribution pattern therebetween may be various.

For example, for a 4-channel wavelength division multiplexing device, it needs to multiplex or demultiplex light beams of 4 wavelengths, and therefore, 4 second optical fibers 332 and 1 first optical fiber 331 are provided in the optical transmission unit 33; for another example, for a 6-channel wavelength division multiplexing device, it is necessary to multiplex or demultiplex light beams of 6 wavelengths, and therefore, 6 second optical fibers 332 and 1 first optical fiber 331 are provided in the optical transmission unit 33. Generally, the number of the optical fibers of the wavelength division multiplexing device is at least 3, which should include 1 first optical fiber 331 and at least 2 second optical fibers 332.

Because the number of the optical fibers is multiple, when the distribution of the optical fibers on the end face is considered, different distribution modes can be adopted, and the optical fibers can be distributed regularly or irregularly, and the optical fibers are based on actual requirements.

As an alternative embodiment, the N second optical fibers 332 in the optical transmission unit 33 are uniformly distributed around the first optical fiber 331.

For example, fig. 4a is a schematic cross-sectional distribution of optical fibers of a 6-channel wavelength division multiplexing device provided herein, as shown in fig. 4a, a first optical fiber 331 is located at a central portion, and 6 second optical fibers 332 are disposed around the first optical fiber 331.

Fig. 4b is a schematic cross-sectional fiber distribution diagram of a 12-channel wavelength division multiplexing device provided in the present application, in which, similar to fig. 4a, a first fiber 331 is located at a central portion, and 12 second fibers 332 are disposed around the first fiber 331 located at the central portion.

Fig. 4c is a schematic cross-sectional fiber distribution diagram of an 18-channel wavelength division multiplexing device according to the present application, in which fig. 4c shows a first fiber 331 in a central portion, and 18 second fibers 332 are disposed around the first fiber 331.

Unlike the previous fig. 4a and 4b, due to the size limitation, the second optical fibers 332 may be layered on the basis of the distribution around the first optical fibers 331 to ensure that the distribution area of the whole optical fibers is kept as small as possible.

Further, in order to ensure compactness of the optical path and minimization of the optical path, as an alternative embodiment, the first optical fiber 331 is coaxial with the main optical axis of the wavelength division multiplexing device, and/or the first optical fiber 331 and the lens 32 are coaxially disposed. Employing such an arrangement will cause the optical axis of the light beam output from the first optical fiber 331 or the light beam input to the first optical fiber 331 to be coaxial with the main optical axis of the wavelength division multiplexing device, and/or the lens 32.

By adopting the above-mentioned structure of the optical transmission unit 33, the volume of the whole wavelength division multiplexing device can be effectively controlled, the processing and the use are convenient, and the cost control is also facilitated.

Compared with the conventional wavelength division multiplexing device, in order to avoid the problem that the angle requirement on the incident light and the device precision requirement are strict due to the multiple reflection of the light in the filter unit 31, on the basis of the above embodiments, in the technical solution provided by the present application, the filter unit 31 may be formed by N filters that are not parallel to each other.

Each filter is used for reflecting the light beam with any wavelength in the N wavelengths and transmitting the light beams with other wavelengths except any wavelength in the N wavelengths; and different filters reflect light beams of different wavelengths.

Specifically, similar to the existing thin film filter, the N filters described herein are coated or plated with different reflective materials, respectively, so that the different filters can reflect light with different wavelengths and transmit light with other wavelengths.

For example, when light with N wavelengths λ 1 to λ N is multiplexed or demultiplexed by a wavelength division multiplexing device, each filter can reflect light with one wavelength, that is, the filter 1 can reflect light with the wavelength λ 1 and transmit light with λ 2 to λ N, the filter 2 can reflect light with the wavelength λ 2 and transmit light with λ 1 and λ 3 to λ N, and so on.

In the existing wavelength division multiplexing devices based on thin film filters, the thin film filters are generally disposed in parallel with each other. The wavelength division multiplexing device is completely different from the existing wavelength division multiplexing device based on the thin film optical filter, in the application, the optical filters are in a non-parallel distribution mode, and through the distribution mode, the optical paths can be ensured not to interfere with each other (namely, the optical paths do not need to reflect light beams with a plurality of wavelengths for a plurality of times like the structure shown in fig. 1), and the problem that the requirement of the processing and adjusting tolerance of an optical communication system is increased due to the increase of the number of channels is avoided.

In terms of the spatial distribution of the filters in the filtering unit 31, in an alternative embodiment, the N filters are arranged in a collinear distribution; or, each optical filter is distributed along the main optical axis of the wavelength division multiplexing device; or the optical filters are distributed along the optical axis of the lens.

In addition, in order to ensure that the optical paths do not interfere with each other, different filters should be in different rotation states.

That is, in the light demultiplexing process, different light beams demultiplexed by different filters may be converged into different optical fibers distributed on the light incident surface of the light transmission unit 33 through the lens 32. In the light multiplexing process, different light beams are multiplexed by different filters and then converged into the optical fiber at the center of the light incident surface of the light transmission unit 33 through the lens 32.

The above-mentioned rotation state refers to a rotation angle and a rotation direction of the filter with respect to the initial state. Here, the initial state may be understood as a state when each filter in the filter unit 31 is mounted or set to the wavelength division multiplexing device.

For the convenience of subsequent debugging, in an initial state, the film coating surface of each optical filter is perpendicular to the optical axis of the main optical axis of the lens/wavelength division multiplexing device, and at this time, the central axis of the optical filter (i.e., the axis perpendicular to the film coating surface and passing through the center of the film coating surface) is parallel to the main optical axis of the lens/wavelength division multiplexing device.

Specifically, when determining the rotation state of each filter, the rotation angle and the rotation direction thereof may be taken into consideration, i.e., different filters in the filter unit 31 will be rotated by respective rotation angles along the rotation axis based on the rotation direction to be in different rotation states. If the plurality of filters are not parallel to each other, the rotation angles and/or the rotation directions of any two filters in the filtering unit 31 at the same time should be different, that is, the rotation angles and/or the rotation directions of any two filters are different when they are in different rotation states.

The rotation angle in the filter rotation state may specifically refer to an included angle between a central axis of the filter and an optical axis of the light transmission unit 33. When the optical transmission unit 33 adopts the structure composed of the 1 first optical fiber 331 and the N second optical fibers 332, the optical axis thereof may be the optical axis of the first optical fiber 331.

The rotation direction in the optical filter rotation state may specifically refer to an axial direction of the rotation shaft along which the optical filter rotates by a certain rotation angle along the rotation shaft based on the rotation direction; wherein the rotation axis is perpendicular to the optical axis of each optical fiber in the optical transmission unit.

Fig. 5a and 5b are schematic diagrams of the rotation state of the optical filter in the present application, and as shown in fig. 5a and 5b, a rectangular coordinate system is established with the main optical axis of the wavelength division multiplexing device/the optical axis of the lens 32/the optical axis of the optical transmission unit 33 as the Z-axis, wherein the XY plane of the rectangular coordinate system is parallel to the focal plane of the lens 32/the light incident surface of the optical transmission unit 33/the cross section of the optical fiber of the optical transmission unit 33.

In the schematic diagram shown in fig. 5a, in the YZ plane, the Z axis is the direction of the main optical axis of the wavelength division multiplexing device/the optical axis of the lens 32/the optical axis of the optical transmission unit 33, the rotation angle of the optical filter 1 in the rotation state is the rotation angle 1 shown in fig. 5a, and the rotation angle of the optical filter 2 in the rotation state is the rotation angle 2 shown in fig. 5 a.

In the schematic diagram of fig. 5b, in the XY plane, a plurality of axes may be arranged such that each axis is at an angle to the X/Y axis and is perpendicular to the Z axis (as shown in fig. 5 b). Then, the plurality of axes may be used as the rotation axes of the filter. That is, for each filter in the initial state, the film-coated surface of each filter is parallel to the XY plane; in the rotating state, each optical filter rotates around the shaft by taking one of the rotating shafts as the axis, and the rotating angle is the rotating angle, so that the coating surface of the rotated optical filter is not parallel to the XY plane any more.

By controlling the rotation direction and the rotation angle of each optical filter, each optical filter can be in different rotation states and in mutually non-parallel distribution states, so that when the optical filter unit multiplexes or demultiplexes light beams, optical paths are irrelevant to each other, and the problem that the requirement on the machining and adjusting tolerance of the optical transmission system is high due to the increase of the number of channels is avoided.

In order to make the filter unit perfectly fit with the light transmission unit through the lens, the rotation state of each filter in the filter unit can be precisely controlled.

Specifically, the rotation direction and rotation angle of the optical filter in the rotation state are related to the distribution (such as the distribution shown in fig. 4a to 4 c) of each optical fiber on the light incident surface or the light emergent surface of the optical transmission unit. It should be noted that, in order to ensure the maximization of the light transmission efficiency, the converging points corresponding to the optical filters mentioned below should be consistent with the positions of the optical fibers on the light incident surface or the light emitting surface, i.e., it can be considered that the optical fiber distributions including fig. 4a to 4c are regarded as the distributions of the converging points corresponding to the optical filters on the light incident surface/the light emitting surface.

For a rotation angle in the rotation state, the rotation angle is related to a vertical distance between a convergence point corresponding to the optical filter and the optical axis of the optical transmission unit. In the demultiplexing process, the convergence point corresponding to the optical filter is a light spot formed on a light incident surface in the optical transmission unit after being converged by a lens; in the multiplexing process, the converging point corresponding to the optical filter refers to a light spot of the light beam on the light emitting surface of the light transmission unit, which emits the corresponding light beam.

Fig. 6a to 6c are schematic diagrams of light paths of the optical filter provided by the present application at different rotation angles, respectively, where fig. 6a to 6c show light paths of the optical filter 1, the optical filter 2, and the optical filter 3 in the same rotation direction and at different rotation angles, respectively. Wherein the rotation angle 1 is less than the rotation angle 2 and less than the rotation angle 3, and the corresponding vertical distance y1 is less than the vertical distance y2 and less than the vertical distance y 3.

That is, the relationship between the rotation angle, the perpendicular distance between the converging point corresponding to the optical filter and the optical axis of the optical transmission unit is:

y＝f×tan(2α)；

y is the vertical distance between a convergence point corresponding to the optical filter and the optical axis of the optical transmission unit, f is the focal length of the lens, and alpha is the rotation angle.

Therefore, in practical application, the vertical distance y between the target optical fiber and the main optical axis and the lens focal length f can be obtained according to the optical fiber distribution in the optical transmission unit, then the rotation angle α of the optical filter required to rotate is determined based on the above relation, and then the position of the corresponding light-focusing point can be coincided with the position of the target optical fiber by controlling the rotation angle of the optical filter, so that the maximum transmission efficiency of light is ensured.

In this process, the distance between the filter and the lens is not considered, and fig. 7 is a schematic diagram of the optical path when the filter of the present application is in different positions under the same rotation state, as shown in fig. 7, the rotation direction and the rotation angle of the same filter 1 are the same, and the difference is the distance between the filter and the lens 32. In other words, in the same rotation state, the position of the corresponding convergence point is fixed regardless of the distance between the filter and the lens 32.

For the rotation direction in the rotation state, the rotation direction corresponds to the axial direction of the rotation shaft, and is perpendicular to the direction vector of the axis where the perpendicular distance between the convergence point corresponding to the optical filter and the optical axis of the optical transmission unit is located.

In the demultiplexing process, the convergence point corresponding to the optical filter is a light spot formed on a light incident surface in the optical transmission unit after being converged by a lens; in the multiplexing process, the converging point corresponding to the optical filter refers to a light spot of the light beam on the light emitting surface of the light transmission unit, which emits the corresponding light beam.

Fig. 8a and 8b are schematic optical path diagrams of the optical filter provided by the present application under different rotation axes, respectively, where fig. 8a is a schematic optical path cross-sectional diagram, and fig. 8b is a schematic optical path perspective diagram corresponding to fig. 8 a. As shown in fig. 8a and 8b, when the optical filter 1 and the optical filter 2 rotate along the rotation axis 1 and the rotation axis 2 respectively by the same rotation angle α 1, the converged light formed by the rotation axes will be distributed on a circle centered on a point on the optical axis.

Therefore, in practical application, the rotating direction, i.e. the rotating axis, corresponding to the optical filter can be determined according to the optical fiber distribution in the optical transmission unit, and then the rotating axis of the optical filter is controlled, so that the position of the corresponding focal point can be overlapped with the position of the target optical fiber, and the maximum transmission efficiency of light is ensured.

In addition, when the other characteristics are not changed with respect to the rotation state, the rotation state of the filter can be changed by changing one of the rotation angle and the rotation direction. Therefore, in order to make the corresponding convergence points of the optical filters correspond to the optical fiber distribution in a one-to-one manner, the purpose of corresponding the optical filters in a one-to-one manner can be achieved by controlling at least one characteristic of the rotation angle and the rotation direction.

Of course, in alternative embodiments, the rotation angle and the rotation direction may be controlled simultaneously to satisfy the use of the wdm device in multiple channels.

Specifically, fig. 9a and 9b are schematic optical path diagrams of the optical filter provided by the present application in different rotation states, respectively, where fig. 9a is a schematic optical path cross-sectional diagram, and fig. 9b is a schematic optical path perspective diagram corresponding to fig. 9 a. As shown in fig. 9a and 9b, when the optical filter 1 and the optical filter 3 rotate along the rotation axis 1 and the rotation axis 2 by the same rotation angle α, the respective converged lights are distributed on a circle centered on a point on the optical axis. The filter 2 and the filter 3 are rotated by different rotation angles α and β, respectively, along the same rotation axis 2, and the perpendicular distances between the converging light and the optical axis formed by the rotation angles α and β are different, respectively.

By the mode, the optical filtering unit can be perfectly matched with the optical transmission unit through the lens, the rotation state of each optical filter in the optical filtering unit can be accurately controlled, and the optical filtering unit is favorably applied to an optical communication system.

In other alternative embodiments, in order to further solve the problem of crosstalk of the optical beams that may occur when the optical beams are transmitted in the wavelength division multiplexing device, the combination relationship between the lens 32 and the optical transmission unit 31 may be further improved.

The general light transmission unit 31 needs to be disposed on the focal plane of the lens 32, and depending on the type of the lens 32, it may be disposed in conformity with the light transmission unit 31. For example, when the lens 32 is a spherical mirror, the lens 32 may be attached to the light transmission unit 31.

Such a relationship will cause crosstalk of light beams when the light beams enter the lens 32 from the light transmission unit 31 or when the light beams enter the light transmission unit 31 from the lens 32, so that part of the light beams are reflected to affect the quality of the light beams. To solve this problem, fig. 10a and 10b are schematic structural diagrams of another wavelength division multiplexing device, respectively, where fig. 10a is a side view and fig. 10b is a top view. As shown in fig. 10a and 10b, when the lens and the light transmission unit are attached to each other, the attachment surface is disposed at a predetermined angle with respect to the optical axis of the lens.

Examples of wavelength division multiplexing devices for several different channels are provided below:

example 1: 4 channel system

Fig. 11a is a schematic fiber distribution diagram of a 4-channel system, wherein a light beam comprising multiple wavelengths will be transmitted in a first fiber located in the center, and a light beam of a single wavelength will be transmitted in a second fiber located on the outside.

FIG. 11b is a schematic diagram of the filters of a 4-channel system in different rotation states, as shown in FIG. 11a, in the initial state, each filter is parallel to the xy-plane, and in the rotation state, each filter will rotate around 4 rotation axes, respectively, as shown by the left rotation axis, to obtain the final rotation state, which matches the position of each fiber in the fiber distribution shown in FIG. 11 a.

Fig. 11c and 11d are schematic diagrams of light paths of a 4-channel system, respectively, fig. 11c is a side view of the light paths, and fig. 11d is a top view of the light paths. As shown in fig. 11c and 11d, the optical filter 1 may be used to reflect the light beam having the wavelength λ 1 and project the light beams having the wavelengths λ 2, λ 3, and λ 4, the optical filter 2 may be used to reflect the light beam having the wavelength λ 2 and project the light beams having the wavelengths λ 1, λ 3, and λ 4, the optical filter 3 may be used to reflect the light beam having the wavelength λ 3 and project the light beams having the wavelengths λ 1, λ 2, and λ 4, and the optical filter 4 may be used to reflect the light beam having the wavelength λ 4 and project the light beams having the wavelengths λ 1, λ 2, and λ 3. With the rotation state shown in fig. 11b, the optical filters 1-4 can split the same beam of light with multiple wavelengths, so that the light with different wavelengths is emitted to different optical fibers; or, light of different wavelengths incident from different optical fibers is combined to form light including a plurality of wavelengths and is emitted to the same optical fiber.

Example 2: 8-channel system

Fig. 12a is a schematic fiber distribution diagram of an 8-channel system, wherein a light beam comprising multiple wavelengths will be transmitted in a first fiber located in the center, and a light beam of a single wavelength will be transmitted in a second fiber located on the outside. Fig. 12b is a schematic view of the rotation axis of the filters of an 8-channel system in different rotation states, as shown in fig. 12b, with the rotation axis of each filter being parallel to the xy-plane. Fig. 12c is a schematic view of the optical path of an 8-channel system, and fig. 12c is a side view of the optical path. The specific implementation manner is similar to that described above, and is not described herein again.

Example 3: wavelength selective switch based on the wavelength division multiplexing device

Fig. 13 is a schematic structural diagram of a wavelength selective switch provided in the present application, as shown in fig. 13, the wavelength selective switch is characterized by comprising the wavelength division multiplexing device 300 according to any of the foregoing embodiments, and a control device 400.

The control device 400 is configured to control the filtering unit 31 in the wavelength division multiplexing device 300, so that the filtering unit 31 demultiplexes or multiplexes 1 beam of input light beams with N wavelengths or N beams of input light beams with different wavelengths to form N beams of output light beams with different wavelengths or 1 beam of output light beams with N wavelengths.

Specifically, the control device 400 is used to control the rotation state of the filter in the filter unit 31.

When the filtering unit 31 includes N optical filters, each optical filter is configured to reflect a light beam with any wavelength of the N wavelengths and transmit a light beam with any wavelength other than the N wavelengths, and different optical filters reflect light beams with different wavelengths, the control device 400 is configured to control different optical filters to be in different rotation states, so that different light beams demultiplexed by different optical filters can be converged by the lens 32 into different optical fibers distributed on the light incident surface of the optical transmission unit 31; alternatively, the control device 400 is configured to control different filters to be in different rotation states, so that different light beams are collimated by the different filters to the optical fiber in the center of the light incident surface of the optical transmission unit 31 through the lens 32 after being multiplexed by the different filters.

The control apparatus 400 may be a mechanical electronic system, which can make the filter rotate in different states according to a preset control program.

In practical applications, the micro control device 400 can switch the rotation states of the N filters according to practical requirements.

For example, the rotation angle α 1 around the rotation axis 1 is a rotation state 1, and the rotation angle α N around the axis N is a rotation state N, and each rotation state corresponds to one of the second optical fibers 332 in the optical transmission unit 33. Fig. 14 is a schematic diagram illustrating a corresponding relationship among optical fibers, optical filters, and wavelengths in a wavelength selective switch according to the present application, as shown in fig. 14, under the control of a control device 400, a certain optical filter may be controlled to rotate to a rotation state 1, or may be controlled to rotate to a rotation state N, so as to correspond to a corresponding second optical fiber 332. In addition, each filter reflects a fixed wavelength, so that the corresponding wavelength of each optical fiber can be switched at will.

Therefore, the wavelength selective switch provided by the application can realize that the control equipment is used for controlling the rotation direction and the rotation angle of the optical filter so as to realize the dynamic switching of the wavelength transmitted by each optical fiber, thereby realizing the switching function and forming a novel switching device.

The above description is only an example of the technical solution of the present invention, and is not intended to limit the scope of the present invention. Any modifications, equivalents, improvements and the like made in accordance with the disclosure of the present invention are intended to be included within the scope of the present invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.