CN113031162B - Optical filter - Google Patents

Abstract

The present disclosure provides an optical filter, comprising: N+1 stages of optical switches, each stage of the optical switch includes a first input end, a second input end, a first output end and a second output end; Ring optical filter unit, each second-order micro-ring optical filter unit includes two micro-ring resonant cavities, and the radii of the micro-ring resonating cavities of the N-level second-order micro-ring optical filter units are different, wherein the k-th second-order micro-ring optical filter unit The order micro-ring optical filter unit is connected to the first output end of the k-th level optical switch; the input optical waveguide unit is used to input the received optical signal into the first-level optical switch; the N-level first waveguide, wherein the k-th level The first waveguide is connected to the output end of the k-th second-order micro-ring optical filter unit and the first input end of the k+1-th optical switch; the N-level second waveguide, wherein the k-th second waveguide is connected to the k-th level The second output end of the optical switch and the second input end of the k+1th stage optical switch; and the output optical waveguide unit, connected to the N+1th stage optical switch, for outputting the filtered optical signal.

Description

Optical filter

technical field

The present disclosure relates to the technical field of optical fiber communication, and more particularly, to an optical filter.

Background technique

The reconfigurable optical add-drop multiplexer is an important part of realizing the flexible optical communication network represented by the wavelength division multiplexing network. The need, in turn, creates a need for highly flexible, tunable filtering optical filters.

The existing technical solutions focus on the research on the tunable characteristics of the center wavelength and filter bandwidth of the optical filter. Common research results include optical filters made of fiber Bragg gratings, Mach-Zehnder, and micro-ring resonators. However, the above-mentioned optical filter ignores the influence of the flexibility of the free spectral region on the reconfigurable optical add-drop multiplexer.

In the process of realizing the present disclosure, it is found that the existing technical solution has the problem that the free spectral region is not tunable when used alone, and cannot meet the requirement of the reconfigurable optical add-drop multiplexer for the flexibility of the free spectral region of the optical filter.

SUMMARY OF THE INVENTION

In view of this, the present disclosure provides an optical filter including an N+1-level optical switch, an N-level second-order micro-ring optical filter unit, an input optical waveguide unit, an N-level first waveguide, an N-level second waveguide, and Output optical waveguide unit. in:

N+1 stages of optical switches, each stage of the optical switch includes a first input end, a second input end, a first output end and a second output end, wherein the above N is a positive integer;

N-stage second-order micro-ring optical filter units, each of the above-mentioned second-order micro-ring optical filter units includes two micro-ring resonators, and the radius of the above-mentioned micro-ring resonant cavity of the N-stage second-order micro-ring optical filter units different, wherein the second-order micro-ring optical filter unit of the k-th stage is connected to the first output end of the optical switch of the k-th stage, and is used for filtering the input optical signal, wherein the above k is less than or equal to the above positive integer of N;

an input optical waveguide unit for inputting the received optical signal into the above-mentioned optical switch of the first stage;

N-stage first waveguide, wherein the k-th first waveguide is connected to the output end of the k-th second-order micro-ring optical filter unit and the k+1-th first input end of the optical switch;

N-stage second waveguide, wherein the k-th stage of the second waveguide is connected to the k-th stage of the optical switch the second output end and the k+1-th stage of the optical switch The second input end; and

The output optical waveguide unit is connected to the above-mentioned optical switch of the N+1th stage, and is used for outputting the filtered optical signal.

According to an embodiment of the present disclosure, the above-mentioned optical switch includes a directional coupling type optical switch and an MZI type optical switch.

According to the embodiments of the present disclosure, the above-mentioned optical switch realizes the switching of the optical signal transmission path through the thermo-optic effect or the photoelectric effect.

According to an embodiment of the present disclosure, each stage of the second-order microring optical filter unit further includes an input waveguide and an output waveguide, wherein the distances between the two microring resonators and the input waveguide and the output waveguide are equal.

According to the embodiment of the present disclosure, the radii of the two micro-ring resonators of the second-order micro-ring optical filter unit are the same; the waveguide width and the waveguide width of the micro-ring resonating cavities of the N-level second-order micro-ring optical filter unit Same thickness.

According to an embodiment of the present disclosure, the above-mentioned micro-ring resonant cavity has a resonant wavelength, and a free spectral region is formed between two adjacent above-mentioned resonant wavelengths.

According to an embodiment of the present disclosure, the relationship between the resonant wavelength and the radius of the microring resonant cavity is as follows:

In the formula, m represents the resonant series; λ represents the above-mentioned central wavelength of the current resonant series; n _c represents the effective refractive index of the above-mentioned micro-ring resonator; R represents the radius of the above-mentioned micro-ring resonator;

The size of the above-mentioned free spectral region of the above-mentioned second-order micro-ring optical filter unit of each stage is calculated according to the following formula:

In the formula, FSR represents the size of the above-mentioned free spectral region.

According to an embodiment of the present disclosure, the adjustment of the free spectral region of the above-mentioned optical filter is realized by switching the above-mentioned optical switch.

According to an embodiment of the present disclosure, the aforementioned first waveguide includes: a curved waveguide; and the aforementioned second waveguide includes: a straight waveguide.

According to an embodiment of the present disclosure, the above-mentioned optical filter is fabricated on a lithium niobate, silicon, silicon dioxide, indium phosphide or gallium arsenide platform through a semiconductor process.

According to the embodiments of the present disclosure, by switching the optical switch, microring resonators with different radii are included in the optical path, thereby changing the size of the free spectral region in the filtering curve of the optical filter, thus solving the problem that the free spectral region is not tunable. Therefore, the tunability of the filtering period and bandwidth of the optical filter is realized.

Description of drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1 schematically shows a schematic diagram of an optical filter according to an embodiment of the present disclosure;

2a and 2b show schematic diagrams of an optical switch 110 in an optical filter according to an embodiment of the present disclosure;

FIG. 3 schematically shows a schematic diagram of the second-order micro-ring optical filter unit 120 according to an embodiment of the present disclosure.

Detailed ways

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that these descriptions are exemplary only, and are not intended to limit the scope of the present disclosure. In the following detailed description, for convenience of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent, however, that one or more embodiments may be practiced without these specific details. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. The terms "comprising", "comprising" and the like as used herein indicate the presence of stated features, steps, operations and/or components, but do not preclude the presence or addition of one or more other features, steps, operations or components.

All terms (including technical and scientific terms) used herein have the meaning as commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly rigid manner.

Where expressions like "at least one of A, B, and C, etc.," are used, they should generally be interpreted in accordance with the meaning of the expression as commonly understood by those skilled in the art (eg, "has A, B, and C") At least one of the "systems" shall include, but not be limited to, systems with A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc. ). Where expressions like "at least one of A, B, or C, etc." are used, they should generally be interpreted in accordance with the meaning of the expression as commonly understood by those skilled in the art (for example, "has A, B, or C, etc." At least one of the "systems" shall include, but not be limited to, systems with A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc. ).

The present disclosure provides an optical filter, comprising: N+1 stages of optical switches, each stage of the optical switch includes a first input end, a second input end, a first output end and a second output end, wherein N is positive Integer; N-level second-order micro-ring optical filter unit, each second-order micro-ring optical filter unit includes two micro-ring resonators, and the radii of the micro-ring resonators of the N-level second-order micro-ring optical filter unit are different , wherein, the k-th second-order micro-ring optical filter unit is connected to the first output end of the k-th optical switch, and is used to filter the input optical signal, where k is a positive integer less than or equal to N; input The optical waveguide unit is used for inputting the received optical signal into the first-level optical switch; the N-level first waveguide, wherein the k-th first waveguide is connected to the output end of the k-th second-order micro-ring optical filter unit and the first-level micro-ring optical filter unit. The first input end of the k+1 stage optical switch; the N stage second waveguide, wherein the kth stage second waveguide is connected to the second output end of the kth stage optical switch and the second input end of the k+1 stage optical switch and an output optical waveguide unit, connected to the N+1 th optical switch, for outputting the filtered optical signal.

FIG. 1 schematically shows a schematic diagram of an optical filter according to an embodiment of the present disclosure.

As shown in FIG. 1 , the optical filter includes an optical switch 110 , a second-order micro-ring optical filter unit 120 , an input optical waveguide unit 130 , a first waveguide 140 , a second waveguide 150 and an output optical waveguide unit 160 . Among them, the optical switch 110, the second-order micro-ring optical filter unit 120, the first waveguide 140 and the second waveguide 150 constitute a filtering structure of the optical filter, and the optical filter can be composed of any number of filtering structures by cascading, In this embodiment, it is assumed that the number of the filtering structures is N.

The optical switch 110 at least includes a first input end 111 , a second input end 112 , a first output end 113 and a second output end 114 . The optical signal has four transmission paths in the optical switch 110 , which are respectively input into the optical switch 110 from the first input terminal 111 or the second input terminal 112 , and output from the first output terminal 113 or the second output terminal 114 respectively.

The input end of the second-order micro-ring optical filter unit 120 is connected to the first output end 113 of the optical switch 110 of the same level, and the output end of the second-order micro-ring optical filter unit 120 is connected to the first waveguide 140 of the same level. For example, for the k-th second-order micro-ring optical filter unit 120 , its input terminal is connected to the first output terminal 113 of the k-th stage optical switch 110 , and its output terminal is connected to the k-th stage first waveguide 140 .

The second-order micro-ring optical filter unit 120 includes two micro-ring resonant cavities 121 , and the radii of the micro-ring resonating cavities 121 in different second-order micro-ring optical filter units 120 are different. The microring resonator 121 can be used for filtering the input optical signal.

The input optical waveguide unit 130 includes two straight waveguides, which are respectively connected to the first input end 111 and the second input end 112 of the first-level optical switch 110, and can be used to input the received optical signal into the first-level optical switch.

Particularly, in other embodiments of the present disclosure, the input optical waveguide unit 130 may include only one straight waveguide, and correspondingly, the first-level optical switch may include only one input end, and the number of its output ends remains unchanged.

The first waveguide 140 is connected to the optical switch 110 and the second-order micro-ring optical filter 120. Specifically, the k-th first waveguide 140 is connected to the output end of the k-th second-order micro-ring optical filter unit 120 and the k+th The first input terminal 111 of the level 1 optical switch 110 . Based on the difference in size of the second-order micro-ring optical filter unit 120 and the optical switch 110 , in order to facilitate structural design, the first waveguide 140 may include a curved waveguide.

The second waveguide 150 is connected to two adjacent optical switches 110 . Specifically, the k-th level second waveguide 150 is connected to the second output end 114 of the k-th level optical switch 110 and the second output end 114 of the k+1-th level optical switch. Input 112 . In order to reduce the optical signal loss caused by the long optical path, preferably, the second waveguide 150 may include a straight waveguide.

The output optical waveguide unit 160 includes two straight waveguides, which are respectively connected to the first output end 113 and the second output end 114 of the N+1 stage optical switch 110 , and can be used to receive the light transmitted by the N+1 stage optical switch 110 . signal, and output the optical signal through two straight waveguides.

Particularly, in other embodiments of the present disclosure, the output optical waveguide unit 160 may include only one straight waveguide, and correspondingly, the N+1 th optical switch may include only one output end, and the number of its input ends remains unchanged. In addition, the N+1-level optical switch can also be replaced by other devices with the function of combining optical paths, such as fiber combiners.

The optical waveguides in the input optical waveguide unit 130, the first waveguide 140, the second waveguide 150, and the output optical waveguide unit 160 may be integrated optical waveguides represented by planar dielectric optical waveguides and strip-shaped dielectric optical waveguides, or may be optical fibers As the representative cylindrical optical waveguide, the type of the optical waveguide is not limited in the embodiments of the present disclosure.

According to the embodiments of the present disclosure, by switching the optical switch, microring resonators with different radii are included in the optical path, thereby changing the size of the free spectral region in the filtering curve of the optical filter, thus solving the problem that the free spectral region is not tunable. Therefore, the tunability of the filtering period and bandwidth of the optical filter is realized.

2a, 2b and 3, the optical filter shown in FIG. 1 will be further described with reference to specific embodiments.

2a and 2b show schematic diagrams of the optical switch 110 in the optical filter according to an embodiment of the present disclosure.

As shown in FIG. 2a and FIG. 2b, the model of the optical switch 110 is selected according to the modulating manner. For example, in the case where the optical switch is modulated by the electro-optic effect, the optical switch 110 can be selected as a directional coupling type optical switch, an MZI type optical switch Optical switch, Y-branch type optical switch, SOA optical gate type optical switch, etc.; in the case of modulating the optical switch through the thermo-optic effect, the optical switch 110 can be selected as MZI type optical switch, 3dB directional coupling type optical switch, thermal Optical digital Y branch optical switch, etc. Preferably, in the embodiment of the present disclosure, the optical switch 110 can be a directional coupling type optical switch or an MZI type optical switch, and the function of the optical switch 110 can also be realized by means of thermo-optic effect or photoelectric effect.

FIG. 3 schematically shows a schematic diagram of the second-order micro-ring optical filter unit 120 according to an embodiment of the present disclosure.

As shown in FIG. 3 , the second-order micro-ring optical filter unit 120 further includes an input waveguide 122 and an output waveguide 123 . For each second-order micro-ring optical filter unit 120 , the distance between the two micro-ring resonators 121 is equal to the distance between the input waveguide 122 and the output waveguide 123 .

The micro-ring resonator 121 has a resonant wavelength, and has a periodic download spectrum at the resonant wavelength. The interval between adjacent resonant wavelengths is called the free spectral region, and the bandwidth of the filter curve represents the resonant wavelength when the energy of the filter curve is the output The width between spectral lines corresponding to half the maximum intensity of .

The resonant wavelength of the micro-ring resonator 121 is related to the radius of the micro-ring resonator 121, which can be specifically expressed as:

In formula (1), m represents the resonant series; λ represents the center wavelength of the current resonant series; n _c represents the effective refractive index of the micro-ring resonator; R represents the radius of the micro-ring resonator.

The size of the free spectral region of the microring resonator 121 can be calculated according to formula (1), which can be specifically expressed as:

In formula (2), FSR represents the size of the free spectral region, and the meanings expressed by other parameters are the same as those of formula (1).

At the same time, the position of the resonant wavelength of the microring resonator 121 can also be fine-tuned by the thermo-optic effect or the photo-electric effect.

In the optical filter of the embodiment of the present disclosure, the two microring resonator cavities 121 included in each second-order microring optical filter unit 120 have the same radius, and have the same waveguide width and waveguide thickness. However, among different second-order micro-ring optical filter units 120, the micro-ring resonant cavity 121 has different radii, the same waveguide width and waveguide thickness, and thus causes different second-order micro-ring optical filter units 120 to have different filtering curves .

According to the embodiments of the present disclosure, based on the consideration of enhancing the controllability of the free spectral region of the optical filter, each second-order micro-ring optical filter unit 120 can be connected according to the size of the radius of the micro-ring resonant cavity 121, for example, the first The radius of the micro-ring resonant cavity 121 of the first-stage second-order micro-ring optical filter unit 120 is the smallest, and the radius of the micro-ring resonating cavity 121 of the N-th second-order micro-ring optical filter unit 120 is the largest.

According to the embodiment of the present disclosure, the free spectral region of the optical filter is the least common multiple of the free spectral region of each second-order micro-ring optical filter unit 120 in the optical path. Therefore, different second-order optical paths can be determined by adjusting the switch. The combination of micro-ring filters can realize the tunability of the free spectral region and the bandwidth.

According to embodiments of the present disclosure, the optical switch 110, the second-order micro-ring optical filter unit 120, and the individual optical waveguides in the optical filter may be on lithium niobate, silicon, silicon dioxide, indium phosphide, or gallium arsenide platforms It is realized by semiconductor process fabrication, which brings the characteristics of high stability, low loss and small size to the optical filter.

According to the embodiments of the present disclosure, the paths are switched based on the optical switches at all levels, and a new filter filter is obtained by selecting the combination between different second-order micro-ring filters that the optical path passes through, and adjusting the resonance wavelength of the corresponding filters. period, and the adjustment of the bandwidth to complete the filtering function of the reconfigurable optical filter.

Embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only, and are not intended to limit the scope of the present disclosure. Although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims (10)

1. An optical filter, comprising: N+1 stages of optical switches, each stage of the optical switch includes a first input end, a second input end, a first output end and a second output end, wherein the N is a positive integer greater than or equal to 2; N-stage second-order micro-ring optical filter units, each of the second-order micro-ring optical filter units includes two micro-ring resonators, and the second-order micro-ring optical filter units of different stages The radii of the micro-ring resonators are different, wherein the second-order micro-ring optical filter unit of the k-th stage is connected to the first output end of the optical switch of the k-th stage, and is used for filtering the input optical signal, Wherein, the k is a positive integer less than or equal to the N; an input optical waveguide unit for inputting the received optical signal into the optical switch of the first stage; N-stage first waveguide, wherein the k-th first waveguide is connected to the output end of the k-th second-order micro-ring optical filter unit and the first input end of the k+1-th stage optical switch ; N-stage second waveguide, wherein the k-th second waveguide connects the second output of the k-th optical switch with the second input of the k+1-th optical switch; and The output optical waveguide unit is connected to the optical switch of the N+1th stage, and is used for outputting the filtered optical signal. 2. The optical filter of claim 1, wherein the optical switch comprises a directional coupling type optical switch and an MZI type optical switch. 3 . The optical filter according to claim 1 , wherein the optical switch realizes the switching of the optical signal transmission path through thermo-optic effect or photoelectric effect. 4 . 4. The optical filter of claim 1, wherein the second-order microring optical filter unit of each stage further comprises an input waveguide and an output waveguide, wherein the two microring resonators are connected to the input The waveguides are equidistant from the output waveguides. 5. The optical filter of claim 1, wherein: The radii of the two micro-ring resonators of the second-order micro-ring optical filter unit are the same; The waveguide width and waveguide thickness of the micro-ring resonator of the N-stage second-order micro-ring optical filter unit are the same. 6 . The optical filter according to claim 1 , wherein the microring resonant cavity has a resonant wavelength, and a free spectral region is formed between two adjacent resonant wavelengths. 7 . 7. The optical filter of claim 6, wherein: The relationship between the resonance wavelength and the radius of the microring resonator is as follows:

In the formula, m represents the resonant series; λ represents the resonant wavelength of the current resonant series; nc represents the effective refractive index of the micro-ring resonator; R represents the radius of the micro-ring resonator; The size of the free spectral region of the second-order micro-ring optical filter unit of each stage is calculated according to the following formula:

In the formula, FSR represents the size of the free spectral region. 8. The optical filter of claim 6, wherein the adjustment of the free spectral region of the optical filter is achieved by switching the optical switch. 9. The optical filter of claim 1, wherein: The first waveguide includes: a curved waveguide; The second waveguide includes: a straight waveguide. 10. The optical filter of claim 1, wherein the optical filter is fabricated on a lithium niobate, silicon, silicon dioxide, indium phosphide or gallium arsenide platform by a semiconductor process.

Images