CN113466998B - Tunable optical filter and optical communication device using same - Google Patents
Tunable optical filter and optical communication device using same Download PDFInfo
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- CN113466998B CN113466998B CN202110765221.8A CN202110765221A CN113466998B CN 113466998 B CN113466998 B CN 113466998B CN 202110765221 A CN202110765221 A CN 202110765221A CN 113466998 B CN113466998 B CN 113466998B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
- G02B6/29335—Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity
- G02B6/29338—Loop resonators
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour in optical waveguides, not otherwise provided for in this subclass
- G02F1/0113—Glass-based, e.g. silica-based, optical waveguides
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0147—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on thermo-optic effects
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/035—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure
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- Optics & Photonics (AREA)
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- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
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Abstract
The present disclosure provides a tunable optical filter comprising: the optical waveguide unit is used for inputting a broadband optical signal to be processed, providing an optical path transmission path without filtering processing for the optical signal and outputting the filtered optical signal; the micro-ring optical filter unit comprises an N-level micro-ring optical filter and is used for filtering the broadband optical signal to be processed; wherein N is an integer greater than 1; the optical switch unit is used for receiving the optical signal and controlling the transmission path of the optical signal by switching the optical switch unit, so that the optical signal is filtered by at least one stage of micro-ring optical filter to form a new free spectral region. The tunable optical filter provided by the disclosure adopts the multistage micro-ring optical filter unit, has a small volume, can be integrated on a semiconductor platform through a semiconductor plane process, and has high stability, low loss and small adjusting and controlling difficulty.
Description
Technical Field
The present disclosure relates to the field of optical fiber communication technologies, and in particular, to a tunable optical filter and an optical communication device using the same.
Background
In optical network transmission, a reconfigurable optical add-drop multiplexer (ROADM) is a key node device for realizing the step of the current WDM network to an all-optical network process. The optical filter is used as a key unit of next generation ROADM, and besides the tunable characteristics of the existing research on wider central wavelength and filter bandwidth, the flexibility of the free spectral range is also an important index of the ROADM system.
Common optical filters often adopt structures such as Fiber Bragg Gratings (FBGs), mach-zehnder (MZ), micro-ring resonators (MRR), but when the structures are adopted alone, the problem that the free spectral region is not tunable exists, so that the requirement of a ROADM system on flexibility of the free spectral region of the optical filter cannot be met.
Disclosure of Invention
In view of the above, the present disclosure provides a tunable optical filter and an optical communication device using the same.
In one aspect of the present disclosure, there is provided a tunable optical filter including:
the optical waveguide unit is used for inputting broadband optical signals to be processed, providing optical path transmission paths for the optical signals without filtering processing, and outputting the filtered optical signals; the micro-ring optical filter unit comprises an N-level micro-ring optical filter and is used for filtering the broadband optical signal to be processed; wherein N is an integer greater than 1; and the optical switch unit is used for receiving the optical signal and controlling the transmission path of the optical signal by switching the optical switch unit so that the optical signal is subjected to filtering processing of at least one stage of micro-ring optical filter to form a new free spectral region.
Further, the optical switch unit includes M optical switches, M being an integer greater than 1; the micro-ring optical filter unit comprises a first micro-ring optical filter and a plurality of micro-ring optical filter subunits, and each micro-ring optical filter subunit comprises at least one stage of micro-ring optical filter; the first micro-ring optical filter is used for carrying out primary filtering on a broadband optical signal to be processed; the M optical switches and the micro-ring optical filter subunits are arranged in a staggered mode, and the transmission path of the primarily filtered optical signal is controlled by switching the state of each optical switch to form a new free spectral region.
Further, the optical waveguide unit includes: the input optical waveguide is used for inputting a broadband optical signal to be processed; the M-1 level intermediate optical waveguide is used for forming an optical path part which corresponds to the optical switch and does not pass through the corresponding micro-ring optical filter subunit in the optical path; m is an integer greater than 1; and the output optical waveguide is used for outputting the filtered optical signal.
Further, each stage of micro-ring optical filter has a periodic download spectrum at the resonant wavelength; each stage of micro-ring optical filter comprises a straight waveguide and a micro-ring resonator, wherein the micro-ring resonator is arranged on one side of the straight waveguide and is used for filtering an optical signal wave band meeting the micro-ring resonance condition in the straight waveguide from a spectrum.
Further, the design parameters of each stage of micro-ring optical filter are the same, wherein the design parameters at least include: the distance between the micro-ring resonator and the straight waveguide; the radius of the microring resonator; the width and thickness of the straight waveguide; and the materials used for the micro-ring resonator and the straight waveguide; when a broadband optical signal to be processed passes through K micro-ring optical filters, the size of the free spectral region is 1/K of the size of the free spectral region formed by only passing through the first-stage micro-ring optical filter, wherein K is a positive integer.
Furthermore, the resonance wavelength of the N-level micro-ring optical filter unit can be tuned independently.
Further, the state switching of the optical switch unit and the resonance wavelength tuning of the micro-ring optical filter are realized by a thermo-optical effect or an electro-optical effect.
Further, the optical switch unit and/or the micro-ring optical filter are made of lithium niobate, silicon dioxide, indium phosphide or gallium arsenide.
Further, the optical switch unit employs a directional coupling type optical switch or an MZI type optical switch.
Another aspect of the present disclosure provides an optical communication device applying the tunable optical filter as described above.
In the technical scheme disclosed by the disclosure, the quantity of micro-ring optical filters passed by broadband optical signals in a path is flexibly changed by utilizing an optical switch, so that reconstruction optical filtering and tunable free spectral range are realized, and the requirement of a ROADM system on the flexibility of the free spectral range of the tunable optical filter is further met. In addition, the filter device is integrated on a certain material platform and manufactured by a semiconductor plane process, so that the filter device is high in stability, low in loss, small in size and small in adjusting and controlling difficulty.
Drawings
FIG. 1 shows a schematic structural diagram of a tunable optical filter according to an embodiment of the present disclosure;
FIG. 2 shows a schematic diagram of a per-stage micro-ring optical filter structure according to an embodiment of the disclosure;
fig. 3 shows a schematic diagram of an optical switch structure according to an embodiment of the present disclosure.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
As described in the background, the conventional optical filter has a problem that the free spectral range is not tunable, so that the requirement of the ROADM system for flexibility of the free spectral range of the optical filter cannot be met. In view of the above, the present disclosure provides a tunable optical filter and an optical communication device using the tunable optical filter, so as to at least partially solve the above technical problems.
Embodiments of the present disclosure provide a tunable optical filter, comprising: an optical waveguide unit, a micro-ring optical filter unit, and an optical switch unit.
The optical waveguide unit is used for inputting a broadband optical signal to be processed, providing an optical path transmission path for the optical signal without filtering processing, and outputting the filtered optical signal.
The micro-ring optical filter unit comprises an N-level micro-ring optical filter and is used for filtering the broadband optical signal to be processed, wherein N is an integer greater than 1.
And the optical switch unit is used for receiving the optical signal and controlling the transmission path of the optical signal by switching the optical switch unit so that the optical signal is subjected to filtering processing of at least one stage of micro-ring optical filter to form a new free spectral region.
The tunable optical filter in the embodiment of the disclosure uses the optical switch to flexibly change the number of micro-ring optical filters through which broadband optical signals pass in a path, thereby realizing reconstruction of optical filtering and tunable free spectral range, and further meeting the requirement of a ROADM system on flexibility of the free spectral range of the tunable optical filter.
In some embodiments of the present disclosure, the optical waveguide unit includes an input optical waveguide, an M-1 order intermediate optical waveguide, and an output optical waveguide, M being an integer greater than 1. The input optical waveguide is used for inputting a broadband optical signal to be processed, the M-1 level intermediate optical waveguide is used for forming an optical path part which corresponds to the optical switch and does not pass through the corresponding micro-ring optical filter subunit in the optical path, and the output optical waveguide is used for outputting the filtered optical signal.
In some embodiments of the present disclosure, the micro-ring optical filter unit includes a first micro-ring optical filter and a plurality of micro-ring optical filter sub-units, wherein each micro-ring optical filter sub-unit includes at least one stage of micro-ring optical filter. The sum of the number of the first micro-ring optical filters and the micro-ring optical filters in all the micro-ring optical filter subunits is N (N is an integer greater than 1), that is, the micro-ring optical filter unit includes N stages of micro-ring optical filters.
Each stage of micro-ring optical filter comprises a straight waveguide and a micro-ring resonator, wherein the micro-ring resonator is arranged on one side of the straight waveguide and is used for filtering out the optical signal wave band meeting the micro-ring resonance condition in the straight waveguide from the spectrum.
Each stage of micro-ring optical filter can perform filtering processing on the optical signal. Specifically, each stage of micro-ring optical filter has a periodic download spectrum at a resonant wavelength, and when an optical signal passes through the i (i is more than 1 and less than or equal to N) th stage of micro-ring optical filter, the corresponding i-th stage of micro-ring optical filter has a periodic download spectrum at the resonant wavelength, so that a deep groove is inserted at the corresponding resonant wavelength in the formed spectrum, and a new free spectral region is formed.
In the embodiment of the disclosure, the tuning of the resonant wavelength of the micro-ring optical filter unit can be realized by independently tuning the resonant wavelength of the N-level micro-ring optical filter. In addition, the resonance wavelength tuning of the micro-ring optical filter can be achieved by a thermo-optical effect or an electro-optical effect. The tuning mode of the resonant wavelength may be selected according to practical applications, and is not limited herein.
It should be noted that the number of micro-ring optical filters in each micro-ring optical filter subunit may be the same, may be different, or may be partially the same. For example, each micro-ring optical filter subunit has a first-order micro-ring optical filter, and all the micro-ring optical filter subunits have the same number of micro-ring optical filters; for example, the number of micro-ring optical filters in the first micro-ring optical filter subunit may be two stages, the number of micro-ring optical filters in the second micro-ring optical filter subunit may be three stages, and so on. The number of the micro-ring optical filters in each micro-ring optical filter subunit may be specifically set according to actual needs, and is not limited herein.
In addition, in some embodiments of the present disclosure, design parameters of each stage of micro-ring optical filter in the micro-ring optical filter unit may be the same or different, and may be specifically set according to an actual situation, which is not limited herein. Wherein the design parameters at least include: the distance between the micro-ring resonator and the straight waveguide, the radius of the micro-ring resonator, the width and the thickness of the straight waveguide, the materials adopted by the micro-ring resonator and the straight waveguide, and the like. For example, the materials used for each stage of micro-ring optical filter include, but are not limited to, lithium niobate, silicon dioxide, indium phosphide, or gallium arsenide.
In the embodiment of the present disclosure, the first micro-ring optical filter is connected to the output end of the input optical waveguide, and is configured to perform primary filtering on a to-be-processed broadband optical signal, so as to implement an initial filtering period.
In an embodiment of the present disclosure, the optical switch unit includes M optical switches, each of which includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input end and the second input end are used for receiving optical signals, and the first output end and the second output end are used for switching transmission paths of the optical signals.
In some embodiments of the present disclosure, switching of states of each optical switch in the optical switch unit may be achieved through a thermo-optical effect or an electro-optical effect, which may be specifically set according to an actual need, and is not limited herein.
In some embodiments of the present disclosure, the material used for the optical switch cells includes, but is not limited to, lithium niobate, silicon dioxide, indium phosphide, or gallium arsenide. The optical switch unit is, for example, a directional coupling type optical switch or an MZI type optical switch, and in some other embodiments, other suitable optical switches may also be used, which is not limited herein.
The M optical switches and the micro-ring optical filter subunits are arranged in a staggered mode, the transmission path of the primarily filtered optical signal can be controlled by switching the state of each optical switch, a new filtering period is obtained, and the free spectral region is changed.
As described above, each stage of micro-ring optical filter can filter the optical signal, and it can be understood that the design parameters of each stage of micro-ring optical filter, such as the distance between the micro-ring resonator and the straight waveguide, the radius of the micro-ring resonator, the width and thickness of the straight waveguide, and the materials used for the micro-ring resonator and the straight waveguide, may affect the filtering function of the optical filter and the tunability of the free spectral range, and different effects may be obtained if each stage of micro-ring optical filter is set to different design parameters. In the embodiment of the present disclosure, in order to facilitate the description of the advantages of the technical solution of the present disclosure, the filter period and the tunability of the free spectral range will be described in detail below by taking the design parameters of each stage of micro-ring optical filters as examples, and it should be understood that the description herein by taking the design parameters of each stage of micro-ring optical filters as examples is a preferred example of the technical solution of the present disclosure, and is not a limitation of the technical solution of the present disclosure.
For example, under the condition that the design parameters of each stage of micro-ring optical filter are the same (the design parameters include, but are not limited to, the distance between the micro-ring resonator and the straight waveguide, the radius of the micro-ring resonator, the width and thickness of the straight waveguide, the materials adopted by the micro-ring resonator and the straight waveguide, and the like), the paths of the optical signals are switched by using each optical switch, a group of filter stripes which are the same as the initial filter period are added on the spectral line of the optical signal by the micro-ring optical filter through which the optical signal passes, and the corresponding filter curve is translated by adjusting the resonance wavelength of the corresponding micro-ring optical filter, so that a new filter period is obtained, the free spectral region is changed, and the filtering function of the reconfigurable optical filter is completed.
The size of the formed new free spectral region is inversely proportional to the number of micro-ring optical filters passing through, the number K (K is a positive integer) of the micro-ring optical filters passing through by the optical signal can be determined by adjusting the switching of the optical switch, and the size of the free spectral region can be 1/K of the size of the free spectral region formed by only passing through the first-stage micro-ring optical filter (i.e. by filtering processing of the first micro-ring optical filter) by adjusting the position of the resonance wavelength of the micro-ring optical filter. For example, when a broadband optical signal to be processed passes through the first-order micro-ring optical filter, the size of the Free Spectral Range is FSR (Free Spectral Range) corresponding to the first-order micro-ring optical filter; when the broadband optical signal to be processed passes through the two stages of micro-ring optical filters, the size of the free spectral region is FSR/2.
The following describes the technical solution of the present disclosure in detail with reference to the tunable optical filter structure in a preferred embodiment of the present disclosure. In this embodiment, each micro-ring optical filter subunit has a first-stage micro-ring optical filter, and the design parameters of each stage of micro-ring optical filter are the same. It should be understood that the number, shape and structure of the parts in the tunable optical filter shown in fig. 1 are only exemplary to help those skilled in the art understand the technical solution of the present disclosure, and are not intended to limit the protection scope of the present disclosure.
Fig. 1 is a schematic diagram of a tunable optical filter according to a preferred embodiment of the present disclosure.
As shown in fig. 1, the tunable optical filter includes: an optical waveguide unit, a micro-ring optical filter unit, and an optical switch unit.
An optical waveguide unit comprising an input optical waveguide 101, an M-1 order intermediate optical waveguide (401, 402.., 40 (M-1)), and an output optical waveguide 102, M being an integer greater than 1.
The micro-ring optical filter unit includes a first micro-ring optical filter 201 and N-1 micro-ring optical filter subunits, where each micro-ring optical filter subunit includes a first-order micro-ring optical filter, that is, the number N =1+1 × (N-1) = N (N is an integer greater than 1) of the micro-ring optical filters in the micro-ring optical filter unit.
The optical switch unit includes M optical switches, where the optical switch 301 connected to the micro-ring optical filter 201, the intermediate optical waveguide 401, and the micro-ring optical filter subunit 202 is a 1 × 2 optical switch, the optical switch 30M connected to the micro-ring optical filter 20N, the intermediate optical waveguide 40 (M-1), and the output optical waveguide 102 is a 2 × 1 optical switch, and the other optical switches are 2 × 2 optical switches. Where "1 × 2" indicates that the optical switch has one input terminal and two output terminals, "2 × 1" indicates that the optical switch has two input terminals and one output terminal, and "2 × 2" indicates that the optical switch has two input terminals and two output terminals.
In this embodiment, the structure of the tunable optical filter is specifically as follows:
referring to fig. 1, an input optical waveguide 101 is connected to an input end of a first micro-ring optical filter 201, and an output end of the first micro-ring optical filter 201 is connected to an input end of an optical switch 301; a first output end and a second output end of the optical switch 301 are respectively connected with an input end of the micro-ring optical filter subunit 202 and an input end of the intermediate optical waveguide 401; the first input end and the second input end of the optical switch 302 are respectively connected with the output end of the micro-ring optical filter subunit 202 and the output end of the intermediate optical waveguide 401, and in the same way, M optical switches (301 to 30M) are staggered with N-1 micro-ring optical filter subunits (202, 203.., 20N) and M-1 level intermediate optical waveguides (401 to 40 (M-1)). The output of the optical switch 30M is connected to the output optical waveguide 102.
In an embodiment of the present disclosure, fig. 2 is a schematic structural diagram of each stage of micro-ring optical filter, and as shown in fig. 2a, each stage of micro-ring optical filter includes: the micro-ring resonator is arranged on one side of the corresponding straight waveguide and is used for filtering an optical signal waveband meeting the micro-ring resonance condition in the straight waveguide from a spectrum. Specifically, positive and negative electrodes may be disposed at both ends of each stage of the micro-ring optical filter, and an electrical excitation may be applied between the positive and negative electrodes to change the resonant wavelength of the optical signal in each stage of the micro-ring optical filter by thermal tuning.
In some embodiments of the present disclosure, as shown in fig. 2b, each stage of the micro-ring optical filter structure may also be an up-down loading type structure, and each stage of the micro-ring optical filter includes: the micro-ring resonator is positioned between the upper straight waveguide and the lower straight waveguide, and the modulation region is also positioned between the upper straight waveguide and the lower straight waveguide.
In the embodiment of the present disclosure, as shown in fig. 3, the optical switches 302, 303, and 30 (M-1) are directional coupling type optical switches or MZI type optical switches, as shown in fig. 3a, a schematic diagram of the directional coupling type optical switch is shown, as shown in fig. 3b, a schematic diagram of the MZI type optical switch is shown, and the directional coupling type optical switch and the MZI type optical switch are both 2 × 2 optical switches, that is, each optical switch includes two input ends and two output ends, which respectively correspond to two output ends of the previous stage and two input ends of the next stage.
Specifically, as shown in fig. 3a, the directional coupling type optical switch is composed of two waveguides which are not coupled due to a long distance between the input and output portions, and a coupling region can be formed where the distance between the two waveguides is minimum. According to the coupled mode theory, if the two waveguides are completely consistent, the two waveguides meet the phase matching condition, and the optical power can be completely coupled from the upper port to the lower port. A modulation region is designed on one waveguide, electric excitation is applied to the region, and the phase matching condition of directional coupling is changed, so that the output power of the lower port is minimum, and the optical switch function is realized.
Specifically, as shown in fig. 3b, the MZI type optical switch is composed of two 3dB beam splitters and two straight waveguides, and a modulation region is designed on one of the straight waveguides, that is, an electrical excitation is applied to the waveguide segment, and the effective refractive index of the waveguide segment is changed through a thermo-optical effect or an electro-optical effect, so that the light intensity at the output end of the right 3dB beam splitter can be destructively interfered or increased, thereby realizing optical switching.
The tunable optical filter has the advantages of small volume, high stability, low loss and small difficulty in adjustment and control, and can be integrated on a semiconductor platform through a semiconductor plane process.
Hereinafter, based on the above tunable optical filter structure, a brief description will be made of a method of flexibly changing the number of micro-ring optical filters passing through a path by using an optical switch to tune a filtering period and a free spectral range.
Under the condition that the design parameters of all stages of micro-ring optical filters are the same, the paths of optical signals are switched by utilizing each optical switch, a group of filter stripes with the same filtering period as the initial filtering period are added on the spectral line of the optical signal by the micro-ring optical filter through which the optical signal passes, and the corresponding filtering curve is translated by adjusting the resonance wavelength of the corresponding micro-ring optical filter, so that a new filtering period is obtained, the free spectral region is changed, and the filtering function of the reconfigurable optical filter is completed.
The size of the formed new free spectral region is inversely proportional to the number of micro-ring optical filters passing through, the number K (K is a positive integer) of the micro-ring optical filters passing through by the optical signal can be determined by adjusting the switching of the optical switch, and the size of the free spectral region can be 1/K of the size of the free spectral region formed by only passing through the first-stage micro-ring optical filter (i.e. only passing through the filtering processing of the first micro-ring optical filter) by adjusting the position of the resonance wavelength of the micro-ring optical filter.
For example, when the optical switches 301 to 30 (M-1) are all in the state that the second output end passes, the first output end is blocked, the first input end of the optical switch 30M is blocked, and the second input end passes, the optical signal passes through the micro-ring optical filter 201, at this time, the corresponding free spectral range is the largest, and the size of the corresponding free spectral range is FSR, that is, FSR corresponding to the first-stage micro-ring optical filter.
For example, when the first output terminal of the optical switch 301 passes and the second output terminal thereof is blocked, the optical switches 302 to 30 (M-1) are all in the state that the second output terminal passes, the first output terminal thereof is blocked, the first input terminal of the optical switch 30M is blocked and the second input terminal thereof passes, the optical signal passes through the micro-ring optical filter 201 and the micro-ring optical filter 202, and the corresponding free spectral range size is FSR/2.
For example, when the first output terminals of the optical switches 301 and 302 pass and the second output terminals thereof are blocked, the states of the optical switches 303-30 (M-1) are that the second output terminals pass, the first output terminals thereof are blocked, the first input terminals of the optical switches 30M are blocked and the second input terminals thereof pass, the optical signal passes through the micro-ring optical filters 201, 202 and 203, and the corresponding free spectral range is FSR/3.
By analogy, when the optical switches 301 to 30M are in the state that the first output end passes through and the second output end blocks, the optical signal passes through the micro-ring optical filters 201 to 20N, the corresponding free spectral range is the minimum, and the corresponding free spectral range is FSR/N.
Based on the above embodiments, it can be known that the tunable optical filter provided by the present disclosure flexibly changes the number of micro-ring optical filters through which optical signals pass in a path through an optical switch, thereby implementing reconfigurable optical filtering and free spectral range tunability.
Another aspect of the present disclosure also provides an optical communication device applying the tunable optical filter as described above. The optical communication equipment can flexibly change the number of micro-ring optical filters passed by optical signals in a path by using the optical switch, thereby realizing reconfigurable optical filtering and free spectral range tunability.
In summary, the present disclosure provides a tunable optical filter and an optical communication device applying the tunable optical filter. The tunable optical filter disclosed by the disclosure can flexibly change the number of micro-ring optical filters passed by optical signals in a path by using the optical switch, so that reconfigurable optical filtering and free spectral range tuning are realized.
The above-mentioned embodiments, objects, technical solutions and advantages of the present disclosure are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present disclosure, and should not be construed as limiting the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (6)
1. A tunable optical filter, comprising:
the optical waveguide unit is used for inputting a broadband optical signal to be processed, providing an optical path transmission path without filtering processing for the optical signal and outputting the filtered optical signal;
the micro-ring optical filter unit comprises an N-level micro-ring optical filter and is used for filtering the broadband optical signal to be processed; wherein N is an integer greater than 1; the tuning of the resonance wavelength of the micro-ring optical filter unit can be realized by independently tuning the resonance wavelength of the N-level micro-ring optical filter;
the optical switch unit is used for receiving optical signals and controlling the transmission path of the optical signals by switching the optical switch unit so that the optical signals are subjected to filtering processing of at least one stage of the micro-ring optical filter to form a new free spectral region; wherein, the first and the second end of the pipe are connected with each other,
each stage of the micro-ring optical filter has a periodic download spectrum at a resonant wavelength; each stage of the micro-ring optical filter comprises a straight waveguide and a micro-ring resonator, wherein the micro-ring resonator is arranged on one side of the straight waveguide and is used for filtering an optical signal waveband meeting a micro-ring resonance condition in the straight waveguide from a spectrum;
the design parameters of each stage of the micro-ring optical filter are the same, wherein the design parameters at least comprise: the distance between the micro-ring resonator and the straight waveguide, the radius of the micro-ring resonator, the width and the thickness of the straight waveguide and the materials adopted by the micro-ring resonator and the straight waveguide; when the broadband optical signal to be processed passes through K micro-ring optical filters, the size of the free spectral region is 1/K of the size of the free spectral region formed by only passing through the first-stage micro-ring optical filter, and K is a positive integer.
2. The tunable optical filter of claim 1, wherein the optical switch unit comprises M optical switches, M being an integer greater than 1;
the micro-ring optical filter unit comprises a first micro-ring optical filter and a plurality of micro-ring optical filter subunits, and each micro-ring optical filter subunit comprises at least one stage of micro-ring optical filter;
the first micro-ring optical filter is used for carrying out primary filtering on the broadband optical signal to be processed;
the M optical switches and the micro-ring optical filter subunits are arranged in a staggered mode, and the transmission path of the optical signal after primary filtering is controlled by switching the state of each optical switch so as to form a new free spectral region.
3. The tunable optical filter of claim 2, wherein the optical waveguide unit comprises:
the input optical waveguide is used for inputting the broadband optical signal to be processed;
the M-1 level intermediate optical waveguide is used for forming an optical path part which corresponds to the optical switch and does not pass through the corresponding micro-ring optical filter subunit in the optical path; m is an integer greater than 1;
and the output optical waveguide is used for outputting the filtered optical signal.
4. The tunable optical filter of claim 1, wherein the state switching of the optical switch unit and the tuning of the resonant wavelength of the micro-ring optical filter are achieved by thermo-optical effect or electro-optical effect.
5. The tunable optical filter of claim 1, wherein the optical switch unit is a directional coupling type optical switch or an MZI type optical switch.
6. An optical communication device employing the tunable optical filter of any one of claims 1-5 for optical filtering.
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