CN111025739B

CN111025739B - Switching unit and wavelength selection switch

Info

Publication number: CN111025739B
Application number: CN201911358684.1A
Authority: CN
Inventors: 方洋; 绪海波; 于艳玲
Original assignee: O Net Communications Shenzhen Ltd
Current assignee: O Net Technologies Shenzhen Group Co Ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2022-12-09
Anticipated expiration: 2039-12-25
Also published as: CN111025739A

Abstract

The invention relates to the technical field of optical fiber transmission, in particular to a switching unit and a wavelength selection switch, wherein the switching unit comprises the following steps: the liquid crystal display device comprises a first half-wavelength liquid crystal, a first equidistant spectroscope, a 3/4 wavelength liquid crystal and a reflecting prism which are sequentially connected; the polarized light is emitted from the first equidistant spectroscope after passing through the first half-wavelength liquid crystal, then returns through the 3/4 wavelength liquid crystal and the reflection prism deflection light path, is changed into P light or S light after passing through the 3/4 wavelength liquid crystal circularly polarized light for the second time, and is finally emitted through the first equidistant spectroscope. By controlling the voltage of the first half-wave liquid crystal and the 3/4 wavelength liquid crystal, the polarization state of the incident light can be changed. When the polarization states of the incident light which enters the first equidistant spectroscope twice are the same as P, the incident light is emitted to the channel (1); and when the polarization state is S, the light is emitted to the channel (3), and if the polarization states are P and S polarization states twice respectively, the two polarization states are emitted to the channel (2) because the light splitting intervals of the first equidistant light splitter are equal.

Description

Switching unit and wavelength selection switch

Technical Field

The invention relates to the technical field of optical communication technology, in particular to a switching unit and a wavelength selection switch.

Background

With the development of 5G technology, the demand for bandwidth from end users is higher and higher, and the technology originally used in the backbone network is sinking to the metropolitan network. The Wavelength Selective Switch (WSS) and the RODAM technology can improve the bandwidth and have potential application prospect if applied to a metropolitan area network. Metropolitan networks, however, are more cost sensitive and temporarily do not have the requirement of large port numbers. Therefore, the WSS with low development cost and low port number can meet the requirements of the next generation of metropolitan area network technology.

The existing main stream WSS has LCOS, MEMS and liquid crystal + triangular birefringent crystal technology. LCOS has higher cost and complex drive, and is not suitable for low cost; the number of ports of the low-cost MEMS technology is limited, the maximum number can only be 1 × 4, and the increase of the number of ports requires a large-scale MEMS array, so that the cost is obviously increased; different channel positions in the liquid crystal + triangular birefringent crystal scheme are not equidistant, and the process flow is complex because the channel positions need to be independently adjusted. Therefore, the existing scheme is difficult to meet the requirement of 50GHz channel interval and the requirement of low cost of the metropolitan area network.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a switching unit and a wavelength selective switch, which solve the problems of complex structure, high cost and the like of the conventional wavelength selective switch.

The technical scheme of the invention is as follows:

the present invention provides a switching unit, comprising: the liquid crystal display device comprises a first half-wavelength liquid crystal, a first equidistant spectroscope, a 3/4 wavelength liquid crystal and a reflecting prism which are sequentially connected; the polarized light is switched into P light or S light through the first half-wavelength liquid crystal, the P light or S light is emitted from different positions after passing through the first equidistant spectroscope, is changed into circular polarized light through the 3/4 wavelength liquid crystal, returns through the reflection prism deflection light path, is changed into the P light or S light through the 3/4 wavelength liquid crystal circular polarized light for the second time, and is emitted from different positions of the first equidistant spectroscope finally.

Further preferred embodiments of the present invention are: the switching unit further comprises an attenuation component which is arranged on one side of the first half-wavelength liquid crystal, away from the first equal-spacing spectroscope and used for attenuating the incident light.

Further preferred embodiments of the present invention are: the attenuation component comprises a second half-wavelength liquid crystal and a polarizer which are connected in sequence; the light beam is decomposed into P light and S light through the second half-wavelength liquid crystal, the S light passes through the polarizer and enters the first half-wavelength liquid crystal, and the P light is blocked.

Further preferred embodiments of the present invention are: the first equal-spacing spectroscope is a PBS array or a square birefringent crystal.

Further preferred embodiments of the present invention are: the cross section of the reflecting prism is an isosceles triangle.

Further preferred embodiments of the present invention are: the switching unit further comprises a channel component which is arranged on one side of the first equidistant beam splitter close to the first half-wavelength liquid crystal and used for increasing an optical path switching channel.

Further preferred embodiments of the present invention are: the channel assembly comprises a third half-wavelength liquid crystal and a second equidistant spectroscope which are sequentially arranged, and the distance between the second equidistant spectroscope is 1/2 of the distance between the first equidistant spectroscope; the polarized light is emitted by the first equidistant beam splitter, enters the third half-wavelength liquid crystal, is adjusted in polarization state by the third half-wavelength liquid crystal and then is emitted from different positions on the second equidistant beam splitter.

The present invention also provides a wavelength selective switch comprising: an optical fiber array provided with an incident port and a plurality of exit ports, a polarization conversion unit, a lens, a grating, a switching unit according to any one of claims 1 to 5; the light beams of the incident ports in the optical fiber array are converted into two beams of linearly polarized light after passing through the polarization conversion unit, the two beams of linearly polarized light are imaged on the grating through the lens, different wavelengths are separated from each other by different angles, the two beams of linearly polarized light are imaged on the switching unit through the lens, the light with different wavelengths are switched to different ports, and the two beams of linearly polarized light are folded back to corresponding emergent ports through the same light path.

Further preferred embodiments of the present invention are: the wavelength selective switch further includes a lens array disposed between the optical fiber array and the polarization conversion unit for collimating the light beam.

Further preferred embodiments of the present invention are: the wavelength selective switch further comprises a dispersion compensation mirror for compensating dispersion.

The invention has the beneficial effects that: by controlling the voltage of the first half-wave liquid crystal and the 3/4 wavelength liquid crystal, the polarization state of the incident light can be changed. When the polarization states of the incident light which enters the first equidistant spectroscope twice are the same as P, the incident light is emitted to the channel (1); and when the polarization state is S, the light is emitted to the channel (3), if the polarization states are P and S polarization states for two times, the light splitting space of the first equidistant spectroscope is equal, the two polarization states are emitted to the channel (2), namely, the 3-path light path switching can be realized by controlling the voltage of the first half-wave liquid crystal and the 3/4 wavelength liquid crystal, and the polarization state switching device has the characteristics of simple structure and simple process flow.

Drawings

Fig. 1 is a schematic structural diagram of a three-channel switching unit (PBS array) according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a three-channel switching cell (birefringent crystal) of an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a six-channel switching unit (PBS array) according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a wavelength selective switch according to an embodiment of the present invention;

fig. 5 is an enlarged view of a lens alignment and polarization conversion unit of an embodiment of the present invention.

Detailed Description

The present invention provides a switching unit and a wavelength selection switch, and in order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

Referring to fig. 1 to 5, a switching unit 100 according to an embodiment of the present invention includes a first half-wavelength liquid crystal 1, a first equidistant beam splitter 2, a 3/4 wavelength liquid crystal 3, and a reflective prism 4, which are connected in sequence; the polarized light is switched into P light or S light through the first half-wavelength liquid crystal 1, the P light or S light is emitted from different positions after passing through the first equidistant spectroscope 2, is changed into circular polarized light through the 3/4 wavelength liquid crystal 3, returns through the reflection prism 4 to turn the light path, is changed into the P light or S light through the 3/4 wavelength liquid crystal circular polarized light for the second time, and is emitted from different positions of the first equidistant spectroscope 2 again. By controlling the voltage of the first half-wave liquid crystal 1 and the 3/4 wavelength liquid crystal 3, the polarization state of incident light can be changed. When the polarization states of the incident light which is incident to the first equidistant spectroscope 2 twice are the same as P, the incident light is emitted to the channel (1); when the polarization state is S, the light is emitted to the channel (3), and if the polarization states are P and S polarization states for two times, the light-emitting intervals of the first equidistant beam splitter 2 are equal, and the two polarization states are both emitted to the channel (2); namely, the switching of 3 paths of light paths can be realized by controlling the voltage of the first half-wave liquid crystal and the 3/4 wavelength liquid crystal, and the method has the characteristics of simple structure, no need of independent adjustment and simple process flow.

Further, the switching unit 100 further includes an attenuation component 5 disposed on a side of the first half-wavelength liquid crystal 1 away from the first equidistant beam splitter 2 for attenuating the incident light. Specifically, the attenuation component 5 comprises a second half-wavelength liquid crystal 51 and a polarizer 52 which are connected in sequence; the light beam is split by the second half-wavelength liquid crystal 51 into P light and S light, which passes the polarizer 52 and enters the first half-wavelength liquid crystal 1, and the P light is blocked. By adding the attenuation component 5 to attenuate the signal of the incident light, the normal operation of the switching unit 100 can be ensured, and the stability of the operation of the switching unit 100 is improved.

Further, the first equal-spacing beam splitter 2 is a PBS array 21 or a square birefringent crystal 22. Equidistant light splitting can be realized through the PBS array 21 or the square birefringent crystal 22, wherein the PBS array 21 has the characteristic of low cost.

Specifically, the cross section of the reflecting prism 4 is an isosceles triangle. Compared with a common prism which can not totally reflect incident light, the reflection prism 4 in the shape of an isosceles right triangle can totally reflect the incident light, so that the loss of optical signals is reduced, and the transmission efficiency is ensured.

Further, referring to fig. 3, the switching unit 100 further includes a channel assembly 6 disposed on a side of the first equidistant beam splitter 2 close to the first half-wavelength liquid crystal 1 for increasing the optical path switching channel. By adding the channel module 6, the operation effect of the switching unit 100 can be improved due to the increase of the number of switchable channels. Specifically, the channel assembly 6 includes a third half-wavelength liquid crystal 61 and a second equidistant beam splitter 62 which are sequentially arranged, and the distance between the second equidistant beam splitter 62 is 1/2 of the distance between the first equidistant beam splitter 2; the polarized light is emitted by the first equidistant beam splitter 2, enters the third half-wavelength liquid crystal 61, is adjusted in polarization state by the third half-wavelength liquid crystal 61, and is emitted from different positions on the second equidistant beam splitter 62. The channel assembly 6 is set to be the third half-wavelength liquid crystal 61 and the second equidistant beam splitter 62, wherein the distance between the second equidistant beam splitter 62 is 1/2 of the distance between the first equidistant beam splitter 2, so that the conversion from three channels to six channels can be realized, the structure is simple, and the production cost is low. In another embodiment, the number of channels may be increased by adjusting the splitting distance of the second equal-spaced beam splitter 62, for example, by setting the distance of the second equal-spaced beam splitter 62 to be the same as that of the first equal-spaced beam splitter 2, one channel may be increased, that is, three channels are changed into four channels. And the change of five channels can be realized by adjusting the light splitting distance of the second equal-distance beam splitter 62.

The second beam splitter 62 has a similar structure to the first beam splitter 2 and is a PBS array or a square birefringent crystal, and is different in that the beam splitting interval of the second beam splitter 62 is 1/2 of the interval of the first beam splitter 2. The PBS array 21 is composed of a plurality of PBS crystals, and the light splitting interval can be set by setting the interval between the PBS crystals. The dispersion pitch of the square birefringent crystal 22 is determined by the thickness of the square birefringent crystal 22.

Further, the channel assembly 6 is provided in plurality, and the plurality of channel assemblies 6 are connected in sequence. The channel assembly 6 can be set according to the actual requirements of users, when the port requirements of the users are large, a plurality of channel assemblies 6 can be set for port expansion, the production cost is low, and the user experience is effectively improved. For example, when two channel assemblies 6 are provided, the distance between one of the channel assemblies 6 is 1/2 of the first equidistant beam splitter 2, and the distance between the other channel assembly 6 is 1/4 of the first equidistant beam splitter 2, so that 12-channel port switching can be realized, and convenience and rapidness are achieved.

Referring to fig. 4 to fig. 5, an embodiment of the invention further provides a wavelength selective switch, including: an optical fiber array 200 provided with an incident port (not shown) and a plurality of exit ports (not shown), a polarization conversion unit 300, a lens 400, a grating 500, a switching unit 100 as described in any of the above; the light beams in the optical fiber array 200 are converted into two beams of linearly polarized light after passing through the polarization conversion unit 300, and are imaged on the grating 500 through the lens 400, different wavelengths are separated by different angles, and are imaged on the switching unit 100 through the lens 400, and the light with different wavelengths is switched to different ports and is then folded back into corresponding exit ports through the same optical path. The invention can realize the light path switching with lower cost by adopting the switching unit 100 and has simple structure.

Specifically, the wavelength selective switch further includes a lens array 600 disposed between the optical fiber array 200 and the polarization conversion unit 300 for collimating a light beam. In this embodiment, the number of lenses in the lens array 600 corresponds to the number of optical fibers in the optical fiber array 200, and a collimator can be formed by the lenses and the optical fibers to collimate the light beam, thereby ensuring the working effect of the wavelength selective switch.

Specifically, the wavelength selective switch further includes a dispersion compensation mirror 700 for compensating dispersion. The dispersion compensation mirror 700 can be used for compensating dispersion, and the working effect of the wavelength selective switch is ensured.

The invention adopts the mode of wavelength liquid crystal and PBS array to carry out light path conversion, and has the advantages over the prior art that:

1. the price of the large-size PBS array is far lower than that of the birefringent crystal with the same size;

2. the multi-port equal spacing of the invention depends on the thickness precision of the PBS array, the spacing of the birefringent crystal depends on the angle of the wedge angle, and the thickness control precision of the PBS array is far higher than the angle precision of the crystal, so the invention is easier to realize equal spacing and has low production difficulty;

3. the square birefringent crystal with parallel end faces can be used for replacing a PBS array, but the square birefringent crystal with parallel end faces are separated by the same distance, the thickness required by the PBS array is far smaller than that of the birefringent crystal, the optical path is shorter, and the bandwidth parameter of the WSS is better if the light spot is smaller;

4. the conversion of more channels can be realized by adding the channel assembly 6, and the production cost is low.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected by those skilled in the art in light of the above teachings and are intended to be within the purview of the appended claims.

Claims

1. A switching unit, comprising: the liquid crystal display device comprises a first half-wavelength liquid crystal, a first equidistant spectroscope, a 3/4 wavelength liquid crystal and a reflecting prism which are sequentially connected, wherein the cross section of the reflecting prism is an isosceles triangle; the polarized light is switched into P light or S light through the first half-wavelength liquid crystal, the P light or S light is emitted from different positions after passing through the first equidistant spectroscope, is changed into circularly polarized light through the 3/4 wavelength liquid crystal, returns through the reflection prism and the deflection light path, is changed into the P light or S light through the 3/4 wavelength liquid crystal circularly polarized light for the second time, and is emitted from different positions of the first equidistant spectroscope again.

2. The switching unit of claim 1, further comprising an attenuation component disposed on a side of the first half-wavelength liquid crystal remote from the first antipodal splitter for attenuating an incident light signal.

3. The switching cell of claim 2, wherein the attenuation module comprises a second half-wavelength liquid crystal and a polarizer connected in series; the light beam is decomposed into P light and S light by the second half-wavelength liquid crystal, the S light passes through the polarizer and enters the first half-wavelength liquid crystal, and the P light is blocked.

4. The switching unit of claim 1, wherein the first equal-spacing beam splitter is a PBS array or a square birefringent crystal.

5. The switching unit according to any one of claims 1 to 4, further comprising a channel assembly disposed on a side of the first equidistant beam splitter adjacent to the first half wavelength liquid crystal for increasing an optical path switching channel.

6. The switching unit of claim 5, wherein the channel assembly includes a third half wavelength liquid crystal and a second equidistant beam splitter sequentially arranged at a pitch of 1/2 of the first equidistant beam splitter pitch; the polarized light enters the third half-wavelength liquid crystal after being emitted by the first equidistant beam splitter, and is emitted from different positions on the second equidistant beam splitter after the polarization state is adjusted by the third half-wavelength liquid crystal.

7. A wavelength selective switch, comprising: an optical fiber array provided with an incident port and a plurality of exit ports, a polarization conversion unit, a lens, a grating, a switching unit according to any one of claims 1 to 6; the light beams of the incident port in the optical fiber array are converted into two beams of linearly polarized light after passing through the polarization conversion unit, the two beams of linearly polarized light are imaged on the grating through the lens, different wavelengths are separated into different angles, the two beams of light are imaged on the switching unit through the lens, the light with different wavelengths is switched to different ports, and the light with different wavelengths is folded back into corresponding emergent ports through the same light path.

8. The wavelength selective switch of claim 7, further comprising a lens array disposed between the fiber array and the polarization conversion unit for collimating the light beam.

9. The wavelength selective switch of claim 7, further comprising a dispersion compensating mirror for compensating dispersion.