WO2024259766A1 - Combined filter - Google Patents

Abstract

The present disclosure provides a combined filter. The combined filter comprises: a first filter; and a second filter, which is combined with the first filter. The second filter comprises at least an input waveguide structure, an output waveguide structure, and an arrayed waveguide located between the input waveguide structure and the output waveguide structure. The input waveguide structure and/or the output waveguide structure comprise(s): a first waveguide component, which is provided with a gap; and two second waveguide components, which are symmetrically arranged on two opposite sides of the first waveguide component, wherein the second waveguide components are connected to the first waveguide component, and the refractive index of the second waveguide components changes periodically.

Description

Splicing Filters Technical Field

The present disclosure relates to the field of communication technology but is not limited to the field of communication technology, and in particular to a splicing filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with application number 202310748107.3 and application date June 21, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference.

Background Art

In recent years, with the growing demand for large-scale cloud services and data center storage and processing, data center systems have become more and more decentralized. Coupled with the emergence of applications such as artificial intelligence, the low-latency, high-bandwidth IP over WDM open optical network interconnection architecture has been rapidly developed.

In WDM optical communication systems, filters are core components, and IP over WDM optical communication systems have new requirements for filters. On the one hand, system vendors hope to expand capacity at a low price based on the original system, that is, to increase communication capacity without changing the original equipment; on the other hand, capacity expansion has led to the extensive use of complex modulation signals such as QAM, which in turn has put higher and higher requirements on filter indicators, requiring high isolation while requiring wide bandwidth, and also higher requirements on wavelength accuracy and bandwidth accuracy.

In the related art, although a spliced filter composed of a comb filter and an arrayed waveguide grating is proposed to meet the above two index requirements at the same time, compared with the conventional arrayed waveguide grating, the insertion loss of the above spliced filter is larger. Although the insertion loss of the spliced filter spliced by the comb filter and the thermal arrayed waveguide grating can achieve the low insertion loss index requirement, and thus is equivalent to the insertion loss level of the conventional athermal arrayed waveguide grating, due to the introduction of the temperature control compensation device, additional power consumption is required, thereby increasing the cost.

Summary of the invention

The disclosed embodiment provides a splicing filter.

The present disclosure provides a splicing filter, the splicing filter comprising:

A first filter;

A second filter, concatenated with the first filter;

Wherein, the second filter at least comprises: an input waveguide structure, an output waveguide structure and an array waveguide located between the input waveguide structure and the output waveguide structure;

The input waveguide structure and/or the output waveguide structure comprises: a first waveguide component provided with a gap;

Two second waveguide components are symmetrically arranged on two opposite sides of the first waveguide component, and the second waveguide components are connected to the first waveguide component, and the refractive index of the second waveguide components changes periodically.

The disclosed embodiment provides a splicing filter. On the one hand, the disclosed embodiment arranges a first waveguide component with a gap in the input waveguide structure and/or output waveguide structure of the second filter, and arranges second waveguide components with periodically changing refractive index on opposite sides of the first waveguide component, respectively. The two second waveguide components are symmetrical with respect to the first waveguide component, thereby utilizing the two second waveguide components to reduce the slit loss introduced in the second filter due to the gap of the first waveguide component; on the other hand, the splicing filter is obtained by splicing the first filter and the second filter, so that the splicing filter can inherit the high performance indicators of the first filter and the second filter respectively, and further improve the performance indicators of the splicing filter by two-stage cascade splicing between the first filter and the second filter.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram showing the structure of a second filter according to an exemplary embodiment;

FIG2 is a partial enlarged schematic diagram of FIG1;

FIG3 is a structural schematic diagram 1 of a splicing filter according to an exemplary embodiment;

FIG4 is a second structural diagram of a splicing filter according to an exemplary embodiment;

FIG. 5 is a schematic diagram showing the structure of a athermal arrayed waveguide grating according to an exemplary embodiment. one;

FIG6 is a second schematic structural diagram of a athermal arrayed waveguide grating according to an exemplary embodiment;

FIG7 is an enlarged schematic diagram of an input waveguide structure or an output waveguide structure according to an exemplary embodiment;

FIG8 is a schematic diagram showing curve comparison of transmission spectrum parameters of an MGTI comb filter, a PSW athermal arrayed waveguide grating and a spliced filter according to an exemplary embodiment;

FIG9 is a schematic diagram showing a definition of a central wavelength insertion loss index according to an exemplary embodiment;

Figure 10 is a schematic diagram showing the insertion loss comparison between an MGTI+PSW AAWG splicing filter and a variety of different arrayed waveguide gratings according to an exemplary embodiment.

DETAILED DESCRIPTION

To make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the specific technical solution of the invention will be further described in detail below in conjunction with the drawings in the embodiments of the present disclosure. The following embodiments are used to illustrate the present disclosure, but are not used to limit the scope of the present disclosure.

The present disclosure provides a splicing filter, as shown in FIG1 and FIG2 , FIG1 is a schematic diagram of a structure of a second filter according to an exemplary embodiment; FIG2 is a partially enlarged schematic diagram of FIG1 . The splicing filter includes:

A first filter;

A second filter, concatenated with the first filter;

The second filter at least comprises: an input waveguide structure 11, an output waveguide structure 12, and an array waveguide 13 located between the input waveguide structure 11 and the output waveguide structure 12;

The input waveguide structure 11 and/or the output waveguide structure 12 comprises:

The first waveguide component 101 is provided with a gap 101a;

Two second waveguide components 102 are symmetrically arranged on two opposite sides of the first waveguide component 101, and the second waveguide components 102 are connected to the first waveguide component 101, and the refractive index of the second waveguide components 102 changes periodically.

In the embodiment of the present disclosure, the splicing filter includes: a first filter and a second filter; the second filter is spliced with the first filter. It can be understood that the first filter processes the input signal and then outputs it to the second filter.

Exemplarily, the first filter includes but is not limited to a comb filter (Interleaver, INT).

A comb filter is composed of many passbands and stopbands arranged in the same manner at certain frequency intervals. A comb filter only allows signals in certain specific frequency ranges to pass through; the characteristic curve of a comb filter is like a comb, so it is called a comb filter.

Here, the comb filter may include an odd channel and an even channel; the channel interval between the two channels is half of the sub-frequency interval of each channel. When a composite light including a plurality of center wavelengths whose frequency interval corresponds to the frequency interval of the comb filter enters the comb filter, the odd channel can filter and output sub-signal light composed of center wavelengths arranged in odd numbers, and the even channel can filter and output sub-signal light composed of center wavelengths arranged in even numbers, and the frequency intervals of the two sub-signal lights are both doubled, that is, corresponding to the sub-frequency intervals of the two odd channels and the even channel.

The spliced filter may include two second filters, wherein one second filter is connected to the odd channel of the comb filter, and the other second filter is connected to the even channel of the comb filter. It should be noted that the frequency interval of the comb filter is f, the frequency interval of the second filter is 2f, and the filtering wavelengths of the two second filters correspond to the odd and even channel wavelengths of the comb filter respectively.

In the embodiment of the present disclosure, the second filter may be an arrayed waveguide grating; the arrayed waveguide grating filter includes: an input waveguide structure, an output waveguide structure and an arrayed waveguide.

Here, the arrayed waveguide is located between the input waveguide structure and the output waveguide structure, and the input end of the arrayed waveguide is connected to the output end of the input waveguide structure, and the output end of the arrayed waveguide is connected to the input end of the output waveguide structure.

It should be noted that the array waveguide can be composed of a plurality of parallel strip waveguides, and the plurality of strip waveguides are bent and arranged in parallel, there is a length difference between two adjacent strip waveguides, and the length of each strip waveguide is different.

The input waveguide structure comprises: an input waveguide and an input side slab waveguide;

The input end of the input side slab waveguide is connected to the input waveguide, and the output end of the input side slab waveguide is connected to the array waveguide. It can be understood that the optical signal output by the input waveguide is input into the array waveguide through the input side slab waveguide.

An output waveguide structure, comprising: an output waveguide and an output side slab waveguide;

The input end of the output side slab waveguide is connected to the array waveguide, and the output end of the output side slab waveguide is connected to the output waveguide. It can be understood that the optical signal output by the array waveguide is input into the output waveguide through the output side slab waveguide.

It should be noted that when the multiplexed optical signal transmitted in the input waveguide enters the input side slab waveguide, the multiplexed optical signal is no longer constrained in the lateral direction, and thus diffracts and expands; the laterally diffracted and expanded multiplexed optical signal is coupled into multiple strip waveguides and transmitted in the multiple strip waveguides.

Since there is a length difference between the multiple strip waveguides on the input side slab waveguide, there is a certain phase difference between the multiplexed optical signals propagating in each strip waveguide when they reach the output side slab waveguide, so that the array waveguide inputs multiple optical signals with different wavelengths and different phases to the output side slab waveguide.

Since the phase shift is related to the wavelength, the convergence imaging position of each wavelength optical signal depends on the input light wavelength. The output waveguides set at different imaging positions can decompose the optical signals of different wavelengths into the corresponding output waveguides to complete the demultiplexing function.

Conversely, the input optical signal is input from the output waveguide structure and output from the input waveguide structure, that is, the light propagation direction in the array waveguide grating is changed, and optical signals with different wavelengths can be converged into the same waveguide to complete the multiplexing function.

The input waveguide structure and/or the output waveguide structure comprises: a first waveguide component and two second waveguide components; the two second waveguide components are symmetrically arranged on two opposite sides of the first waveguide component.

Here, the two opposite sides of the first waveguide component may be the two ends of the first waveguide component in the light propagation direction, that is, the light propagation direction in the waveguide structure is: transmitted from one second waveguide component to the first waveguide component, and propagated from the first waveguide component to another second waveguide component.

The first waveguide component is provided with a slit; it should be noted that in order to meet the specific requirements of the arrayed waveguide grating, a slit needs to be provided on the first waveguide component. However, since the slit of the first waveguide component will generate a certain additional optical loss (i.e., slit loss) on the optical power transmitted in the first waveguide component, the array The loss of the column waveguide grating increases, which in turn affects the normal operation of the communication system.

The refractive index of the second waveguide component varies periodically; it can be understood that, since the refractive index of the second waveguide component varies periodically, when light propagates in the second waveguide component, the divergence angle of the light field varies periodically in at least one light field limiting direction, and the mode spot size of the light wave also varies periodically.

It should be noted that the slot loss mainly consists of the following two parts: (1) Fresnel reflection caused by the refractive index mismatch or incomplete matching of the waveguides on both sides of the slot; and (2) mode field mismatch caused by the different mode field shapes of the waveguides on both sides of the slot.

It is understandable that after cutting a conventional waveguide, the mode field of the slot part of the conventional waveguide jumps, although the waveguide mode fields of the waveguides on both sides of the slot are not mismatched at this time, but the mode field jumps. And due to the limitation of the current slot cutting process, the slot width can reach about 20um, resulting in large slot cutting loss.

In the embodiments of the present disclosure, second waveguide components with periodically changing refractive index are respectively arranged on two opposite sides of the first waveguide component, so that the mode field of the input waveguide structure and/or the output waveguide structure presents periodic changes; compared with the situation where the mode field increases in a jumpy manner, the input waveguide structure and/or the output waveguide structure shown in the present disclosure includes an array waveguide grating (PSW) of a periodically segmented waveguide (PSW), which effectively reduces the slit loss due to the periodic change of the mode field.

In some embodiments, the input waveguide and/or the output waveguide comprises: a first waveguide component and two second waveguide components;

In some other embodiments, the input-side slab waveguide and/or the output-side slab waveguide comprises: a first waveguide component and two second waveguide components;

In the embodiment of the present disclosure, on the one hand, a first waveguide component having a slot is arranged in the input waveguide structure and/or the output waveguide structure of the second filter, and second waveguide components with periodically changing refractive index are respectively arranged on opposite sides of the first waveguide component, and the two second waveguide components are symmetrical with respect to the first waveguide component, thereby utilizing the two second waveguide components to reduce the slot loss introduced in the second filter due to the slot of the first waveguide component; on the other hand, a spliced filter is obtained by splicing the first filter and the second filter, so that the spliced filter can inherit the high performance indicators of the first filter and the second filter respectively, and further improve the performance of the spliced filter by two-stage cascade splicing between the first filter and the second filter. Performance metrics of the splicing filter.

In some embodiments, the second filter further includes:

The compensation structure is fixedly connected to the two second waveguide components respectively, and is used to drive the two second waveguide components to move relative to each other to compensate for wavelength drift caused by temperature.

In the disclosed embodiment, the second filter further includes: a compensation structure;

Here, the compensation structure is an athermal compensation structure, so that the two second waveguide components are driven to move relative to each other through the athermal compensation structure to compensate for the wavelength drift caused by temperature.

It can be understood that since the first waveguide component of the input side slab waveguide (or the output side slab waveguide) is provided with a gap, the input side slab waveguide (or the output side slab waveguide) is divided into two parts by the gap, namely, a second waveguide component and a connected part of the first waveguide component, and another second waveguide component and a connected part of the first waveguide component.

It should be noted that due to the material of the waveguide body, especially the _SiO2 material of the planar waveguide (PLC), the refractive index of the waveguide body will change with the temperature, and the change of the refractive index will cause the center wavelength of the arrayed waveguide grating to shift. In order to make the arrayed waveguide grating work normally within the working environment temperature, it is necessary to control the center wavelength of the arrayed waveguide grating to work stably near the International Telecommunication Union-Telecommunication Standardization (ITU-T) wavelength.

In the disclosed embodiment, a gap (i.e., a first waveguide component) may be provided in the input waveguide structure and/or the output waveguide structure of the array waveguide grating, and the compensation structure may be fixedly connected to two second waveguide components on both sides of the first waveguide component respectively; here, the fixed connection method includes but is not limited to bonding, welding, screwing, etc.

When the temperature changes, the length of the compensation structure also changes (i.e., there is a phenomenon of thermal expansion and contraction), so that the compensation structure drives the two second waveguide components to move relative to each other, thereby compensating for the center wavelength drift of the array waveguide grating caused by temperature changes.

Exemplarily, as shown in FIG3 , FIG3 is a structural schematic diagram of a splicing filter according to an exemplary embodiment, wherein the first filter is a comb filter; the second filter is a PSW athermal arrayed waveguide grating (Athermal Arrayed Waveguide Grating, AAWG).

As another example, as shown in FIG. 4, FIG. 4 is a diagram showing a splicing filter according to an exemplary embodiment. FIG. 2 is a structural diagram of a filter, wherein the first filter is a Michelson Interferometer (MI) and the second filter is a PSW AAWG.

Among them, the above-mentioned Michelson interferometer can also include a Michelson-GT cavity interferometer (Michelson-Gires-Tournois-Interferometer, MGTI), which is the most common type of optical interferometer; the principle of the Michelson interferometer is that a beam of incident light is divided into two beams by a beam splitter and then each is reflected back by a corresponding plane mirror. Because the two beams have the same frequency, the same vibration direction and a constant phase difference (i.e., they meet the interference condition), interference can occur; the different optical paths of the two beams in the interference can be achieved by adjusting the length of the interference arm and changing the refractive index of the medium, so that different interference patterns can be formed. When the plane reflector in the Michelson interferometer is replaced by a Gires-Tournois resonant cavity, it is called a Michelson-GT cavity interferometer.

It should be noted that the specific structure of the compensation structure can be set according to actual needs. For example, the compensation structure can be a compensation structure based on a single drive rod, or the compensation structure can be a compensation structure based on a double drive rod. The embodiments of the present disclosure are not limited to this.

Exemplarily, as shown in FIG5 , FIG5 is a schematic diagram of a structure of a athermal array waveguide grating according to an exemplary embodiment. The compensation structure may include: a first drive rod 201, a second drive rod 202 and a stress plate 203, and the thermal expansion coefficients of the materials of the first drive rod 201 and the second drive rod 202 are both greater than the thermal expansion coefficient of the material of the stress plate 203. The stress plate 203 includes a first sub-section 203a and a second sub-section 203b; wherein the two second waveguide components are fixedly connected to the two sub-sections of the stress plate 203, respectively. The two ends of the first drive rod 201 are respectively connected to a force-bearing portion and a second sub-section 203b in the first sub-section 203a; the second drive rod 202 acts on another force-bearing portion in the first sub-section 203a.

When the temperature changes, the length of the first driving rod is extended and contracted, so that the two sub-parts of the stress plate are relatively translated and/or rotated, thereby forming temperature compensation. And by using the first driving rod and the second driving rod acting on different positions of the application plate, the distance and/or angle between the two force-bearing parts in the stress plate are changed, forming elastic deformation.

As another example, as shown in FIG6 , FIG6 is a second schematic diagram of a structure of a heatless array waveguide grating according to an exemplary embodiment. The compensation structure may include two drive rods with the same thermal expansion coefficient but different lengths, and the two ends of a drive rod 301 (i.e., the first drive rod) are respectively connected to the two second waveguides. Another driving rod 302 (ie, the second driving rod) has one end connected to a second waveguide component, and the other end detachably contacts a force-bearing end surface, which is relatively fixed with the end surface of the first driving rod on another second waveguide component.

When the temperature changes, the two second waveguide components are driven to move relative to each other by the first driving rod, and the elastic deformation of the first driving rod is changed by using the deformation amount of the second driving rod that is different from the first driving rod, so that the two second waveguide components are driven to have different relative displacements in different temperature ranges.

In some embodiments, the passband width of the transmission spectrum of the second filter is greater than the passband width of the transmission spectrum of the first filter, and the passband non-flatness of the transmission spectrum of the second filter is less than the passband non-flatness of the transmission spectrum of the first filter.

It can be understood that the passband width of the transmission spectrum of the PSW array waveguide grating is greater than the passband width of the transmission spectrum of the comb filter, and the passband unevenness of the transmission spectrum of the PSW array waveguide grating is less than the passband unevenness of the transmission spectrum of the comb filter.

It should be noted that the passband width and passband nonflatness in the present disclosure are discussed when the first filter and the second filter correspond to the same filtering wavelength (or filtering frequency band), reflecting the difference in the passband parameters of the transmission spectra exhibited by the first filter and the second filter.

Since the frequency interval of the second filter is greater than the frequency interval of the first filter, the passband width of the transmission spectrum of the second filter is greater than the passband width of the transmission spectrum of the first filter.

The passband unevenness of the transmission spectrum of the second filter is within the preset unevenness threshold range, that is, the transmission spectrum of the second filter tends to be flat within the passband. When the first filter and the second filter filter the same filtering wavelength (or the same filtering frequency band), the passband width of the second filter is greater than the passband width of the first filter. It can be determined that the second filter has little effect on the transmission spectrum shape of the corresponding filtering wavelength of the splicing filter within the passband. In this way, the transmission spectrum shape of the splicing filter is closer to the transmission spectrum shape of the first filter, so the splicing filter can well inherit the excellent index performance of the first filter within the passband.

In some embodiments, the spectral value (dB) of the transmission spectrum of the spliced filter is the sum of the spectral value (dB) of the transmission spectrum of the first filter and the spectral value (dB) of the transmission spectrum of the second filter.

It should be noted that the spectral value of the transmission spectrum and the insertion loss value are inversely proportional.

In some embodiments, the insertion loss value of the spliced filter is the sum of the insertion loss value of the first filter and the insertion loss value of the second filter.

The spectral value (dB) of the transmission spectrum of the splicing filter is the sum of the spectral value (dB) of the transmission spectrum of the first filter and the spectral value (dB) of the transmission spectrum of the second filter; therefore, the spectral value of the transmission spectrum outside the passband of the splicing filter can satisfy the requirement of being smaller than the spectral value of the transmission spectrum outside the passband of the first filter, and also smaller than the spectral value of the transmission spectrum outside the passband of the second filter. In this way, the embodiment of the present invention makes the spectral value of the transmission spectrum outside the passband of the splicing filter lower than those of the first filter and the second filter, thereby increasing the isolation of the splicing filter and reducing crosstalk.

In some embodiments, the second waveguide assembly comprises:

A plurality of connected waveguide units, each waveguide unit having a first region and a second region, the refractive index of the first region being different from the refractive index of the second region;

The first regions and the second regions in a plurality of waveguide units are arranged alternately.

In the embodiment of the present disclosure, the second waveguide component includes: a plurality of waveguide units, and the plurality of waveguide units are connected in sequence. It should be noted that the plurality of waveguide units have the same width.

Each waveguide unit has a first region and a second region, and the first region and the second region are two adjacent regions in the waveguide unit.

The refractive index of the first region in the waveguide unit is different from the refractive index of the second region.

It can be understood that the refractive indexes of the first regions within the plurality of waveguide units are the same, and the refractive indexes of the second regions within the plurality of waveguide units are the same.

The first regions and the second regions in the plurality of waveguide units are arranged alternately and at intervals. It can be understood that the first regions and the second regions in two adjacent waveguide units are arranged adjacently.

Since the refractive indexes of the first regions in different waveguide units are the same, the refractive indexes of the second regions in different waveguide units are the same, and the refractive index of the first region is different from the refractive index of the second region; by arranging the first regions and the second regions in a plurality of waveguide units alternately and at intervals, the refractive index of the second waveguide assembly composed of a plurality of waveguide units presents a periodic change along the light propagation direction in the second waveguide assembly; thereby, when light propagates in the second waveguide assembly, in at least one light field limiting direction, the divergence angle of the light field presents a periodic change, and the mode spot size of the light wave also presents a periodic change; so as to reduce the cut-off of the second filter. Seam loss.

In some embodiments, the duty cycles of the plurality of waveguide units in the second waveguide assembly are different;

The duty cycle is used to describe the ratio between the width of the first region or the second region in the waveguide unit and the width of the waveguide unit.

In the embodiment of the present disclosure, the duty cycle of the waveguide unit is the ratio between the area width of the first area or the second area within the waveguide unit and the width of the waveguide unit; here, the width of the waveguide unit depends on the sum of the area widths of the first area and the second area.

It can be understood that since the widths of the multiple waveguide units are the same, the duty cycles of the multiple waveguide units in the second waveguide component are different, that is, the area widths of the first areas of the multiple waveguide units in the second waveguide component are different, or the area widths of the second areas of the multiple waveguide units in the second waveguide component are different.

It should be noted that the embodiment of the present disclosure utilizes multiple waveguide units with different duty cycles to form a second waveguide component, so that when light propagates in the second waveguide component, the divergence angle of the light field and the mode spot size of the light wave change with the change of the duty cycle of the multiple waveguide units through the change of the duty cycle between the multiple waveguide units in the second waveguide component.

In some embodiments, the duty cycle of the plurality of waveguide units in the second waveguide assembly presents an increasing or decreasing trend in the light propagation direction of the waveguide units.

In the embodiment of the present disclosure, the second waveguide component includes a plurality of connected waveguide units, and the duty ratios of the plurality of waveguide units show a unidirectional variation trend in the light propagation direction of the second waveguide component.

It can be understood that the duty cycle of the plurality of waveguide units presents an increasing or decreasing trend in the light propagation direction of the second waveguide assembly.

In one embodiment, the duty cycles of the plurality of waveguide units in the two second waveguide components have opposite changing trends in the light propagation directions of the waveguide units.

It should be noted that since the two second waveguide components are symmetrical with respect to the first waveguide component, if the duty cycle of the multiple waveguide units in one second waveguide component shows a decreasing trend in the light propagation direction of the second waveguide component, then the duty cycle of the multiple waveguide units in the other second waveguide component shows an increasing trend in the light propagation direction of the second waveguide component.

In some embodiments, the duty cycle of the waveguide unit is related to the duty cycle of the waveguide unit and the first waveguide. The distance between the guide components is positively correlated;

The duty cycle is a duty cycle corresponding to the first region, and the refractive index of the first region is higher than the refractive index of the second region.

In the embodiment of the present disclosure, the refractive index of the first region of the waveguide unit is higher than that of the second region; that is, the first region may be a high refractive index region within the waveguide unit, and the second region may be a low refractive index region within the waveguide unit.

The ratio between the width of the first region and the width of the waveguide unit can be determined as the duty cycle, and the duty cycle can be used to describe the proportion occupied by the high refractive index region in each waveguide unit.

The duty ratios of the plurality of waveguide units in each second waveguide assembly present a unidirectional variation trend in the light propagation direction of the waveguide units.

The duty cycle of the waveguide unit can be determined based on the distance between the waveguide unit and the first waveguide component; here, the duty cycle of the waveguide unit is positively correlated with the distance between the waveguide unit and the first waveguide component; it can be understood that, in the second waveguide component, the duty cycle close to the first waveguide component is smaller than the duty cycle far away from the first waveguide component.

Since the second waveguide component is symmetrically arranged on two opposite sides of the first waveguide component, in the light propagation direction of the waveguide structure, the duty cycle of the second waveguide component located on the input side of the first waveguide component presents a decreasing trend, that is, in the light propagation direction, the duty cycle in the second waveguide component changes from large to small. The duty cycle of the second waveguide component located on the output side of the first waveguide component presents an increasing trend, that is, in the light propagation direction, the duty cycle in the second waveguide component changes from small to large.

It should be noted that, when light propagates in the second waveguide component, the divergence angle of the light field and the mode spot size of the light wave change with the duty cycle of the multiple waveguide units. By making the duty cycle of the second waveguide component located on the input side of the first waveguide component present a decreasing trend, and the duty cycle of the second waveguide component located on the output side of the first waveguide component present an increasing trend, when light propagates in the waveguide structure, the divergence angle of the light field and the mode spot size of the light wave both show a trend of changing from small to large and then from large to small, so as to compensate for the slit loss of the second filter.

In some embodiments, the duty cycle of the plurality of waveguide units in the second waveguide assembly varies with the change of the waveguide width of the second waveguide assembly in a preset direction;

Wherein, the preset direction is parallel to the light propagation direction in the second waveguide component.

In the embodiment of the present disclosure, since the duty cycle of the waveguide unit is the ratio between the area width of the first area and the width of the waveguide unit, the duty cycle of the waveguide unit can be adjusted by changing the area width of the first area or the width of the waveguide unit (conventionally, the width of the first area is changed).

Since the second waveguide component is arranged in the input side slab waveguide and/or the output side slab waveguide, and the input side slab waveguide and the output side slab waveguide are multimode waveguide components, the duty cycle of the second waveguide component can only be adjusted by adjusting the waveguide width of the second waveguide component in a preset direction.

Here, the preset direction is: a direction parallel to the light propagation direction in the second waveguide component.

Exemplarily, the duty cycle of the second waveguide component may be adjusted by adjusting the lateral waveguide width of the second waveguide component.

In some embodiments, as shown in FIG2 , the first waveguide component 101 includes:

Waveguide body;

The slit mark 101b is disposed on the waveguide body and is used to indicate a position to be cut on the waveguide body to form the slit.

In the embodiment of the present disclosure, the first waveguide component includes: a waveguide body.

In order to facilitate cutting of the waveguide body, a slit mark can be set on the surface of the waveguide body to indicate the position to be cut on the waveguide body, so that when the waveguide body is cut, slits can be made based on the slit mark to form a gap.

In some embodiments, the waveguide body may be provided with a plurality of slit marks, and the slit position of the waveguide body may be determined by the linear positions of the plurality of slit marks.

Here, the waveguide body may be provided with at least two slit marks, and based on the straight line where the at least two slit marks are located, the slit position of the waveguide body can be more accurately located.

The shape of the cutting mark can be determined according to the cutting equipment actually used. For example, the cutting mark can be in the shape of a "one", a "cross", etc.

In some embodiments, the waveguide width of the waveguide body is determined by the slot width and slotting tolerance of the waveguide body.

In the embodiment of the present disclosure, the waveguide width of the waveguide body may depend on the gap width of the waveguide body and Kerf tolerance.

It should be noted that when the waveguide body is cut to form the slit, the waveguide width of the waveguide body should be determined with reference to the slit width of the slit; considering the slit tolerance, the waveguide width of the waveguide body should be determined based on the slit width of the slit and the slit tolerance.

In some embodiments, as shown in FIG7 , FIG7 is an enlarged schematic diagram of an input waveguide structure or an output waveguide structure according to an exemplary embodiment. The first waveguide component 101 includes:

The matching liquid 101c is filled in the gap of the waveguide body; wherein the refractive index of the matching liquid 101c is related to the refractive index of the waveguide body.

In an embodiment of the present disclosure, a first waveguide assembly includes: a matching liquid;

The matching liquid is filled in the gap of the waveguide body; it should be noted that the matching liquid has a high transmittance to the light propagating in the waveguide body; the refractive index of the matching liquid is the same as or similar to the refractive index of the waveguide body. Fresnel reflection caused by the mismatch or incomplete matching of the refractive index of the waveguide on both sides of the gap is also one of the causes of the slot loss. In order to reduce the slot loss, the Fresnel reflection can be reduced by filling the gap with a suitable matching liquid.

In some embodiments, the refractive index of the matching liquid may be determined based on the material of the waveguide body.

Exemplarily, if the waveguide body is made of planar waveguide PLC SiO ₂ material, the refractive index of the corresponding matching liquid is the same as the refractive index of the waveguide body.

As another example, if the waveguide body is made of silicon photonic material, the refractive index of the corresponding matching liquid is smaller than the refractive index of the waveguide body.

In some embodiments, the slot is close to the center of the waveguide body; wherein an insertion loss parameter of the waveguide structure is positively correlated with the distance between the slot and the center of the waveguide body.

In the embodiment of the present disclosure, the gap may be close to the center position of the waveguide body; and the closer the gap is to the center position of the waveguide body, the smaller the insertion loss parameter of the arrayed waveguide grating; conversely, the farther the gap is from the center position of the waveguide body, the larger the insertion loss parameter of the arrayed waveguide grating.

It should be noted that, since the two second waveguide components are symmetrically arranged on both sides of the first waveguide component, if the slot is located at the center of the waveguide body, the two second waveguide components are symmetrically arranged relative to the slot. This can effectively reduce the insertion loss of the array waveguide grating after cutting.

In some embodiments, the slit mark may be set at the center of the waveguide body so as to perform cutting at the center of the waveguide body to form a slit.

The following takes a splicing filter composed of an MGTI comb filter as the first filter and a PSW athermal array waveguide grating (MGTI+PSW AAWG splicing filter for short) as an example to illustrate the performance of the splicing filter shown in the embodiment of the present disclosure.

Assume that the MGTI comb filter has 1 input channel and 2 output channels, the 2 output channels are odd channel and even channel respectively; wherein, the starting wavelength of the odd channel is λ _odd-1 =λ _ITU-1 =1528.773nm (f _odd-1 =f _ITU-1 =196100GHz), the ending wavelength of the even channel is λ _even-32 =λ _ITU-64 =1566.518nm (f _even-64 =f _ITU-64 =191375GHz), the ending wavelength of the odd channel is λ _odd-32 =c/(f _even-64 +75)=1565.905nm, and the starting wavelength of the even channel is λ _even-1 =c/(f _odd-1 -75)=1529.358nm; therefore, the frequency interval of the odd channel/even channel is 150GHz, and the interval between the odd channel and the even channel is 75GHz. The frequency interval of the two 32-channel PSW athermal arrayed waveguide gratings is 150 GHz. The center wavelength and frequency interval of the two PSW athermal arrayed waveguide gratings correspond to the odd channel and the even channel of the MGTI comb filter, respectively, that is, the starting wavelength of the PSW arrayed waveguide grating corresponding to the odd channel is 1528.773 nm, and the ending wavelength is 1565.905 nm. The starting wavelength of the PSW arrayed waveguide grating corresponding to the even channel is 1529.358 nm, and the ending wavelength is 1566.518 nm.

The following describes the splicing filter in detail by taking the starting frequency f _ITU-1 =196100 GHz (the ending frequency f _ITU-64 =191375 GHz), ie, the ITU center wavelength λ _ITU-1 =1528.773 nm as an example.

As shown in Figure 8, Figure 8 is a curve comparison diagram of transmission spectrum parameters of an MGTI comb filter, a PSW athermal arrayed waveguide grating and a spliced filter according to an exemplary embodiment; wherein the abscissa represents the wavelength Wavelength, and the ordinate represents the transmittance Transmittance. As can be seen from Figure 8, under the same wavelength, the transmission spectrum (dB) of the spliced filter is the sum of the transmission spectrum (dB) of the MGTI comb filter and the transmission spectrum (dB) of the PSW arrayed waveguide grating.

As shown in FIG. 9 , FIG. 9 is a schematic diagram showing a definition of a central wavelength insertion loss indicator according to an exemplary embodiment, that is, the central wavelength insertion loss is defined as the insertion loss value corresponding to the ITU central wavelength, also known as ITU Center wavelength insertion loss; Combined with Figures 8 and 9, the insertion loss value corresponding to the ITU center wavelength of the MGTI comb filter can be calculated, that is, the insertion loss value corresponding to the ITU center wavelength IL _ITU-MGTI = 0.45dB, the insertion loss value corresponding to the ITU center wavelength of the PSW array waveguide grating IL _{ITU-PSW AAWG} = 4.04dB, and the insertion loss value corresponding to the ITU center wavelength of the spliced filter IL _{ITU-MGTI+PSW AAWG} = 4.58dB; it can be seen that the ITU center wavelength insertion loss of the spliced filter (4.58dB) is approximately the sum of the insertion losses of the MGTI comb filter (0.45dB) and the PSW array waveguide grating (4.04dB); it should be noted that the extra 0.09dB is affected by factors such as fusion loss and test error during optical fiber splicing.

In order to reflect the performance difference between the MGTI+PSW AAWG splicing filter shown in the embodiment of the present disclosure and the conventional arrayed waveguide grating (Arrayed Waveguide Grating, AWG), as shown in Figure 10, Figure 10 is a schematic diagram of the insertion loss comparison of an MGTI+PSW AAWG splicing filter and various different arrayed waveguide gratings according to an exemplary embodiment.

As can be seen from Figure 10, the insertion loss of a conventional arrayed waveguide grating is about 4dB, the slit loss of a conventional arrayed waveguide grating is about 0.6dB, the insertion loss of a conventional athermal arrayed waveguide grating is about 4.6dB, the loss of the combined MGTI comb filter is about 0.5dB, and the insertion loss of a conventional MGTI+AAWG spliced filter is about 5.1dB.

The PSW array waveguide grating shown in the embodiment of the present invention introduces a second waveguide component with a segmented periodic change in refractive index, namely, a PSW structure, so that the insertion loss of the PSW array waveguide grating is increased by about 0.3dB, that is, the insertion loss of the PSW array waveguide grating is about 4.3dB, and the slit loss is about -0.2dB, so that the insertion loss of the PSW athermal array waveguide grating is about 4.1dB. Combined with the loss of the MGTI comb filter of about 0.5dB, the insertion loss of the MGTI+PSW AAWG spliced filter is about 4.6dB, which is close to the insertion loss of the conventional athermal array waveguide grating (4.6dB). Therefore, the MGTI+PSW AAWG spliced filter shown in the embodiment of the present invention can be replaced by existing athermal array waveguide gratings and other indicators.

The splicing filter recorded in the examples of the present disclosure is only taken as an example of the embodiments described in the present disclosure, but is not limited to this. As long as it involves the splicing filter, it is within the protection scope of the present disclosure.

It should be understood that the references to "one embodiment" or "an embodiment" throughout the specification mean that a particular feature, structure, or characteristic associated with the embodiment is included in at least one embodiment of the present disclosure. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present disclosure, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure. The serial numbers of the embodiments of the present disclosure are only for description and do not represent the advantages and disadvantages of the embodiments.

It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

The above is only an embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims (12)

A splicing filter, wherein the splicing filter comprises: A first filter; A second filter, concatenated with the first filter; Wherein, the second filter at least comprises: an input waveguide structure, an output waveguide structure and an array waveguide located between the input waveguide structure and the output waveguide structure; The input waveguide structure and/or the output waveguide structure comprises: a first waveguide component provided with a gap; Two second waveguide components are symmetrically arranged on two opposite sides of the first waveguide component, and the second waveguide components are connected to the first waveguide component, and the refractive index of the second waveguide components changes periodically. The splicing filter according to claim 1, wherein the second filter further comprises: The compensation structure is fixedly connected to the two second waveguide components respectively, and is used to drive the two second waveguide components to move relative to each other to compensate for wavelength drift caused by temperature. The splicing filter according to claim 1 or 2, wherein the passband width of the transmission spectrum of the second filter is greater than the passband width of the transmission spectrum of the first filter, and the passband non-flatness of the transmission spectrum of the second filter is less than the passband non-flatness of the transmission spectrum of the first filter. The spliced filter according to claim 1 or 2, wherein the second waveguide component comprises: A plurality of connected waveguide units, each waveguide unit having a first region and a second region, the refractive index of the first region being different from the refractive index of the second region; The first regions and the second regions in a plurality of waveguide units are arranged alternately. The spliced filter according to claim 4, wherein the duty cycles of the plurality of waveguide units in the second waveguide assembly are different; The duty cycle is used to describe the first area or the second area in the waveguide unit. The ratio between the width of the region and the width of the waveguide unit. The spliced filter according to claim 5, wherein the duty cycle of the plurality of waveguide units in the second waveguide assembly presents an increasing or decreasing trend in the light propagation direction of the waveguide units. The spliced filter according to claim 6, wherein the duty cycle of the waveguide unit is positively correlated with the distance between the waveguide unit and the first waveguide component; The duty cycle is a duty cycle corresponding to the first region, and the refractive index of the first region is higher than the refractive index of the second region. The spliced filter according to any one of claims 5 to 7, wherein the duty cycle of the plurality of waveguide units in the second waveguide component varies with the change of the waveguide width of the second waveguide component in a preset direction; Wherein, the preset direction is parallel to the light propagation direction in the second waveguide component. The spliced filter according to claim 1 or 2, wherein the first waveguide component comprises: Waveguide body; A slit mark is arranged on the waveguide body and is used to indicate a position to be cut on the waveguide body to form the slit. The splicing filter according to claim 9, wherein the waveguide width of the waveguide body is determined by the slot width and slotting tolerance of the waveguide body. The spliced filter according to claim 10, wherein the first waveguide component comprises: A matching liquid is filled in the gap of the waveguide body; wherein the refractive index of the matching liquid is related to the refractive index of the waveguide body. The splicing filter according to claim 10, wherein the slot is close to the center position of the waveguide body; wherein the insertion loss parameter of the waveguide structure is positively correlated with the distance between the slot and the center position of the waveguide body.