阅读说明：本技术 一种可调谐光滤波器 (Tunable optical filter ) 是由 王皓岩 刘杰 叶雨农 李苗 李嵬 于 2021-04-06 设计创作，主要内容包括：本发明提供一种可调谐光滤波器,包括用于输入待处理宽带光信号输入光波导、输出光波导、环形光波导和包括级联的N级2×2光开关的光开关单元,N为正整数；第一级2×2光开关的输入端分别与输入光波导和环形光波导相连,以选择性地将宽带光信号传输至第二级2×2光开关或将宽带光信号中通带内的光信号耦合至环形光波导内；环形光波导分别连接第一级2×2光开关的输入端和第N级2×2光开关的输出端,以形成一闭合的环形谐振腔体进行谐振；输出光波导与第N级2×2光开关的输出端相连,以将谐振后的光信号输出。本发明可实现可重构光学滤波特性,对滤波特性进行灵活控制,损耗小,体积紧凑,稳定性高,调节和控制难度小,便于直接应用。(The invention provides a tunable optical filter, which comprises an input optical waveguide, an output optical waveguide, an annular optical waveguide and an optical switch unit, wherein the input optical waveguide, the output optical waveguide and the annular optical waveguide are used for inputting broadband optical signals to be processed, the optical switch unit comprises cascaded N-level 2 x 2 optical switches, and N is a positive integer; the input end of the first-stage 2 x 2 optical switch is respectively connected with the input optical waveguide and the annular optical waveguide so as to selectively transmit the broadband optical signal to the second-stage 2 x 2 optical switch or couple the optical signal in a passband of the broadband optical signal into the annular optical waveguide; the annular optical waveguide is respectively connected with the input end of the first-stage 2X 2 optical switch and the output end of the Nth-stage 2X 2 optical switch to form a closed annular resonant cavity for resonance; the output optical waveguide is connected with the output end of the Nth-stage 2 x 2 optical switch to output the resonated optical signal. The reconfigurable optical filter can realize reconfigurable optical filter characteristics, flexibly control the filter characteristics, and has the advantages of small loss, compact volume, high stability, small difficulty in adjustment and control and convenient direct application.)

1. A tunable optical filter comprising an input optical waveguide, an output optical waveguide, a ring optical waveguide, and an optical switching unit comprising a cascade of N stages of 2 x 2 optical switches, N being a positive integer, wherein:

the input optical waveguide is used for inputting a broadband optical signal to be processed;

the input end of the first-stage 2 x 2 optical switch is connected with the input optical waveguide to selectively transmit the broadband optical signal to the second-stage 2 x 2 optical switch or couple the optical signal in a passband of the broadband optical signal into the annular optical waveguide;

the annular optical waveguide is respectively connected with the input end of the first-stage 2 x 2 optical switch and the output end of the Nth-stage 2 x 2 optical switch to form a closed annular resonant cavity so as to perform resonance on optical signal reciprocating transmission coupled into the annular optical waveguide;

the output optical waveguide is connected with the output end of the Nth-stage 2 x 2 optical switch so as to output the resonated optical signal.

2. The tunable optical filter of claim 1,

in the N-stage 2 × 2 optical switch, in addition to the first stage 2 × 2 optical switch and the nth stage optical switch:

the output end of the previous stage 2 x 2 optical switch is respectively connected with the input end of the next stage 2 x 2 optical switch.

3. The tunable optical filter of claim 2, wherein in the N-stage 2 x 2 optical switches, each stage 2 x 2 optical switch comprises a first optical waveguide and a second optical waveguide, and the first optical waveguide and the second optical waveguide are the same in structure and material.

4. The tunable optical filter of claim 3, wherein a portion of the first optical waveguide and a portion of the second optical waveguide are adjacent to form a coupling region, the first optical waveguide and the second optical waveguide being parallel to each other in the coupling region to form parallel waveguides.

5. The tunable optical filter of claim 4, wherein the length of the coupling region and the waveguide pitch of the parallel waveguide are not consistent in two adjacent 2 x 2 optical switches, and the waveguide width and the waveguide thickness of the parallel waveguide are consistent.

6. The tunable optical filter of claim 1, wherein each of the 2 x 2 optical switches is an independent switching unit.

7. The tunable optical filter of claim 1, wherein optical signals coupled into the ring optical waveguide travel clockwise within the ring resonator body.

8. The tunable optical filter of claim 1, wherein the input optical waveguide, the output optical waveguide, the ring optical waveguide, and the 2 x 2 optical switch are fabricated on a lithium niobate, silicon dioxide, indium phosphide, gallium arsenide platform by semiconductor processes.

9. A reconfigurable optical add/drop multiplexer, wherein the optical add/drop multiplexer comprises the tunable optical filter of any one of claims 1 to 8.

10. An optical communication device, characterized in that it comprises a tunable optical filter according to any one of claims 1 to 8.

Technical Field

The invention belongs to the technical field of optical fiber communication, and particularly relates to a tunable optical filter.

Background

New data services in the internet, such as video conferencing and electronic commerce, are emerging continuously, and increasingly higher requirements are placed on the capacity, speed and flexibility of communication networks. The use of the reconfigurable optical add-drop multiplexer brings more convenience for service development and reduction of operation cost for network operation. Ideal Reconfigurable Optical networks require next generation Reconfigurable Optical Add-Drop multiplexers (ROADMs) with Reconfigurable, flexibly tunable characteristics. The optical filter uses an optical method and an optical element to realize a filtering function of an optical signal in terms of signal processing in the technical field of optical fiber communication. Compared with the traditional electronic technology, the optical element has the characteristics of flexibility and wide bandwidth, and can directly filter the microwave signal with high frequency bandwidth.

Common reconfigurable and flexibly tunable optical filters usually adopt structures such as Bragg fiber gratings and Mach-Zehnder devices, but the conventional schemes have the problems of large loss, large volume, high cost, poor stability, difficult adjustment and control and the like. The optical filter based on the traditional single micro-ring resonator structure only has specific filtering performance and cannot realize the flexible and tunable functions aiming at filtering indexes such as insertion loss, full width at half maximum, extinction ratio and the like; the optical filter based on a plurality of micro-ring resonator structures is provided with a plurality of cascaded coupling areas, and the problems of complex structure, difficulty in tuning and the like often exist.

Disclosure of Invention

The present invention is directed to at least one of the problems of the prior art, and provides a tunable optical filter.

In one aspect of the present invention, there is provided a tunable optical filter comprising an input optical waveguide, a ring optical waveguide, an output optical waveguide, and an optical switching unit comprising cascaded N-stage 2 × 2 optical switches, N being a positive integer, wherein:

the input optical waveguide is used for inputting a broadband optical signal to be processed;

the input end of the first-stage 2 x 2 optical switch is connected with the input optical waveguide to selectively transmit the broadband optical signal to the second-stage 2 x 2 optical switch or couple the optical signal in a passband of the broadband optical signal into the annular optical waveguide;

the annular optical waveguide is respectively connected with the input end of the first-stage 2 x 2 optical switch and the output end of the Nth-stage 2 x 2 optical switch to form a closed annular resonant cavity so as to perform resonance on optical signal reciprocating transmission coupled into the annular optical waveguide;

the output optical waveguide is connected with the output end of the Nth-stage 2 x 2 optical switch so as to output the resonated optical signal.

In some embodiments, in the N-stage 2 × 2 optical switch, in addition to the first stage 2 × 2 optical switch and the nth stage optical switch:

the output end of the previous stage 2 x 2 optical switch is respectively connected with the input end of the next stage 2 x 2 optical switch.

In some embodiments, in the N-stage 2 × 2 optical switch, each stage 2 × 2 optical switch includes a first optical waveguide and a second optical waveguide, and the first optical waveguide and the second optical waveguide have the same structure and material.

In some embodiments, a portion of the first optical waveguide and a portion of the second optical waveguide are adjacent to form a coupling region, the first optical waveguide and the second optical waveguide being parallel to each other in the coupling region to form parallel waveguides.

In some embodiments, in two adjacent 2 × 2 optical switches, the length of the coupling region and the waveguide pitch of the parallel waveguide are not consistent, and the waveguide width and the waveguide thickness of the parallel waveguide are consistent.

In some embodiments, each of the 2 × 2 optical switches is an independent switch unit.

In some embodiments, an optical signal coupled into the ring optical waveguide travels clockwise within the ring resonator body.

In some embodiments, the input optical waveguide, the output optical waveguide, the ring optical waveguide, and the 2 × 2 optical switch are fabricated by a semiconductor process on a lithium niobate, silicon dioxide, indium phosphide, gallium arsenide platform.

In another aspect of the present invention, there is provided a reconfigurable optical add/drop multiplexer comprising the tunable optical filter of any one of the above-mentioned.

In another aspect of the invention, there is provided an optical communication device comprising the tunable optical filter recited in any one of the above.

The tunable optical filter provided by the invention adopts a straight-through structure based on an annular resonant cavity and an optical switch, a broadband optical signal to be processed is input to a first-stage 2 x 2 optical switch through an input optical waveguide, the first-stage 2 x 2 optical switch selectively transmits the broadband optical signal to a second-stage 2 x 2 optical switch or couples the optical signal in a passband of the broadband optical signal into the annular optical waveguide, so that the optical signal in the passband can be transmitted to and fro in the annular resonant cavity for resonance, the resonant optical signal is output through the output optical waveguide, reconfigurable optical filtering characteristics can be realized, the flexible control on filtering characteristics such as insertion loss, full width at half maximum, extinction ratio, central wavelength and the like can be realized, and the requirements of a ROADM system on reconfigurability and flexible tunability of the optical filter are further met. In addition, the tunable optical filter of the embodiment has the advantages of small loss, compact size, high stability and small difficulty in adjustment and control, and is conveniently and directly used for constructing devices and modules for optical communication such as ROADM.

Drawings

Fig. 1 is a schematic structural diagram of a tunable optical filter according to an embodiment of the present invention;

fig. 2 is a schematic diagram of optical signal transmission paths of a 2 × 2 optical switch in different states according to another embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

In one aspect of the present invention, as shown in fig. 1, there is provided a tunable optical filter including an input optical waveguide 001, an output optical waveguide 002, an annular optical waveguide 003, and an optical switching unit including cascaded N-stage 2 × 2 optical switches 100 to N00, N being a positive integer. As shown in fig. 2, each of the N-stage 2 × 2 optical switches 100 to N00 includes an input terminal I1, an input terminal I2, an output terminal O1, and an output terminal O2. When the 2 × 2 optical switch is in the through state, as shown in fig. 2, the output terminal O1 outputs the optical signal input by the input terminal I1, and the output terminal O2 outputs the optical signal input by the input terminal I2. When the 2 × 2 optical switch is in the cross state, as shown in fig. 2, the output terminal O1 outputs the optical signal input by the input terminal I2, and the output terminal O2 outputs the optical signal input by the input terminal I1.

The input optical waveguide 001 is used for inputting a broadband optical signal to be processed, and serves as an input end of the tunable optical filter. The input of the first stage 2 x 2 optical switch 100 is connected to an input optical waveguide 001 to selectively transmit a broadband optical signal to the second stage 2 x 2 optical switch 200 or to couple an optical signal within a passband of the broadband optical signal into an annular optical waveguide 003. The ring optical waveguide 003 is connected to the input terminal of the first stage 2 × 2 optical switch 100 and the output terminal of the nth stage 2 × 2 optical switch N00, respectively, to form a closed ring resonant cavity (not shown) for resonating optical signal back and forth coupled into the ring optical waveguide 003. The output optical waveguide 002 serves as the output of the tunable optical filter. The output optical waveguide 002 is connected to the output terminal of the nth stage 2 × 2 optical switch N00 to output the resonated optical signal.

When the tunable optical filter of this embodiment is used for filtering, the input optical waveguide 001 inputs a broadband optical signal to be processed to the first-stage 2 × 2 optical switch 100, and then the first-stage 2 × 2 optical switch 100 is controlled to selectively transmit the broadband optical signal to the second-stage 2 × 2 optical switch 200, or selectively couple an optical signal in a passband of the broadband optical signal to the ring optical waveguide 003, where the optical signal in the passband can be transmitted back and forth in the ring resonant cavity to resonate, and the resonated optical signal can be output through the output optical waveguide 002, thereby implementing the filtering function of the tunable optical filter of this embodiment.

The working principle of the annular resonant cavity is that the annular resonant cavity has an intrinsic resonant frequency, when the wavelength transmitted in an incident signal cannot meet the resonance condition of the micro-ring, the light wave continues to propagate along the direction of the input straight waveguide, and when the wavelength transmitted in the incident signal meets the resonance condition of the micro-ring, the micro-ring can play a role of communicating, and the signal with the wavelength is coupled into the straight waveguide on the other side.

The tunable optical filter of the embodiment adopts a straight-through structure based on an annular resonance cavity and an optical switch, a broadband optical signal to be processed is input into a first-stage 2 × 2 optical switch through an input optical waveguide, the first-stage 2 × 2 optical switch selectively transmits the broadband optical signal to a second-stage 2 × 2 optical switch or couples an optical signal in a passband of the broadband optical signal into the annular optical waveguide, so that the optical signal in the passband can be transmitted to and fro in the annular resonance cavity for resonance, the resonated optical signal is output through the output optical waveguide, reconfigurable optical filtering characteristics can be realized, flexible control over filtering characteristics such as insertion loss, full width at half maximum, extinction ratio, central wavelength and the like can be realized, and requirements of a ROADM system on reconfigurability and flexibility of the optical filter are further met. In addition, the tunable optical filter of the embodiment has the advantages of small loss, compact size, high stability and small difficulty in adjustment and control, and is conveniently and directly used for constructing devices and modules for optical communication such as ROADM.

Illustratively, the tunable optical filter of this embodiment is based on the principle of the conventional straight-through micro-ring resonator, and its filter curve is a typical straight-through spectral line of the notch micro-ring resonator arranged periodically.

Illustratively, as shown in fig. 1, in the N-stage 2 × 2 optical switch, in addition to the first stage 2 × 2 optical switch 100 and the nth stage optical switch N00: the output end of the previous stage 2 x 2 optical switch is respectively connected with the input end of the next stage 2 x 2 optical switch. For example, as shown in fig. 1, the input terminal of the second stage 2 × 2 optical switch 200 is connected to the output terminal of the previous stage 2 × 2 optical switch, i.e., the first stage optical switch 100, and the output terminal of the second stage 2 × 2 optical switch 200 is connected to the input terminal of the next stage 2 × 2 optical switch, i.e., the third stage optical switch 300. For another example, the input terminal of the N-1 th stage 2 × 2 optical switch (N-1)00 is connected to the output terminal of the previous stage 2 × 2 optical switch, and the output terminal of the N-1 th stage 2 × 2 optical switch (N-1)00 is connected to the input terminal of the next stage 2 × 2 optical switch, i.e., the nth stage 2 × 2 optical switch N00.

In the tunable optical filter of this embodiment, the output end of the previous stage 2 × 2 optical switch is connected to the input end of the next stage 2 × 2 optical switch, so that the N stages of 2 × 2 optical switches can be sequentially connected together, thereby implementing the cascade connection.

Illustratively, as shown in fig. 1, in the N-stage 2 × 2 optical switch, each stage of 2 × 2 optical switch includes a first optical waveguide and a second optical waveguide, and the first optical waveguide and the second optical waveguide have the same structure and material. For example, as shown in fig. 1, a first-stage 2 × 2 optical switch includes a first optical waveguide 101 and a second optical waveguide 102, respectively, a second-stage 2 × 2 optical switch includes a first optical waveguide 201 and a second optical waveguide 202, respectively, a third-stage 2 × 2 optical switch includes a first optical waveguide 301 and a second optical waveguide 302, respectively, and so on, an N-1-stage 2 × 2 optical switch includes a first optical waveguide (N-1)01 and a second optical waveguide (N-1)02, respectively, and an N-stage 2 × 2 optical switch includes a first optical waveguide N01 and a second optical waveguide N02, respectively.

In the tunable optical filter of this embodiment, the first optical waveguide and the second optical waveguide in the 2 × 2 optical switch are both configured to have the same structure and material, so that when an optical signal passes through the 2 × 2 optical switch, different paths can be selected to pass through according to different states of the 2 × 2 optical switch, without changing other optical characteristics.

Illustratively, a portion of the first optical waveguide and a portion of the second optical waveguide are adjacent to form a coupling region, and the first optical waveguide and the second optical waveguide are parallel to each other in the coupling region to form parallel waveguides. For example, as shown in fig. 1, a portion of the first optical waveguide 101 and a portion of the second optical waveguide 102 in the first stage 2 × 2 optical switch 100 are adjacent to naturally form a coupling region (not shown) in which the first optical waveguide 101 and the second optical waveguide 102 are arranged in parallel up and down to form parallel waveguides.

The tunable optical filter of this embodiment can form different coupling paths according to different states of the 2 × 2 optical switch by the parallel waveguides in the coupling region of the 2 × 2 optical switch.

Illustratively, in two adjacent 2 × 2 optical switches, the length of the coupling region and the waveguide pitch of the parallel waveguide are not consistent, and the waveguide width and the waveguide thickness of the parallel waveguide are consistent. For example, as shown in fig. 1, the coupling region length and the waveguide pitch of the parallel waveguide in the first stage 2 × 2 optical switch 100 and the first stage 2 × 2 optical switch 200 are not uniform, and the waveguide width and the waveguide thickness of the parallel waveguide are uniform.

Since the geometric parameters of the 2 × 2 optical switch may affect the final output filter spectrum, for example, the difference between the waveguide distance and the coupling region length of the adjacent parallel waveguides may affect the coupling efficiency between the input optical waveguide and the ring optical waveguide, so that the characteristics of the final output filter spectrum, such as insertion loss, full width at half maximum, extinction ratio, etc., are changed, therefore, the tunable optical filter of the embodiment sets the coupling region length of the two adjacent 2 × 2 optical switches and the waveguide distance of the parallel waveguides to be different, sets the waveguide width and the waveguide thickness of the parallel waveguides to be the same, so that the optical signal may obtain filter curves with different filter characteristics after passing through different 2 × 2 optical switches, thereby achieving the tunability of the filter characteristics, such as insertion loss, full width at half maximum, extinction ratio, etc.

Illustratively, each 2 × 2 optical switch is an independent switch unit, as shown in fig. 1. That is, the cascaded N-stage 2 × 2 optical switches are independent in function, and the states of each 2 × 2 optical switch can be selectively switched to form different transmission paths.

In the tunable optical filter of this embodiment, the cascaded N-stage 2 × 2 optical switches are respectively set as independent switch units, and the ring-shaped resonant cavity can be in different coupling regions by controlling different optical switches to be in different states, so that flexible control of filtering characteristics such as insertion loss, full width at half maximum, extinction ratio, and the like is achieved, tuning of an individual resonant cavity is achieved, and the tunable optical filter of this embodiment exhibits reconfigurable multiple filtering characteristics.

Illustratively, as shown in fig. 1, an optical signal coupled into the ring-shaped optical waveguide may be transmitted clockwise in the ring-shaped resonant cavity, so as to realize reciprocal transmission to complete resonance.

Illustratively, as shown in fig. 1, the input optical waveguide 001, the output optical waveguide 002, the ring optical waveguide 003, and the 2 × 2 optical switch may be implemented by semiconductor process on a platform of lithium niobate, silicon dioxide, indium phosphide, or gallium arsenide.

The tunable optical filter of the embodiment is manufactured and realized by the input optical waveguide, the output optical waveguide and the annular optical waveguide on a lithium niobate, silicon dioxide, indium phosphide and gallium arsenide platform by using a semiconductor process, is convenient for large-scale integration, and can realize large-scale low-cost mass production.

Illustratively, the center wavelength tuning of the tunable optical filter of the present embodiment may be implemented by using a thermo-optic effect or an electro-optic effect, so as to change the refractive index of the ring-shaped optical waveguide, thereby implementing the tuning.

In another aspect of the present invention, a reconfigurable optical add/drop multiplexer is provided, the reconfigurable optical add/drop multiplexer comprising the tunable optical filter described above. The specific structure of the tunable optical filter can be referred to the above description, and is not described herein again.

In another aspect of the invention, an optical communication device is provided, which comprises the tunable optical filter recited above. The specific structure of the tunable optical filter can be referred to the above description, and is not described herein again.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.