Cascaded optical structure with common phase shifter

Abstract

This invention proposes an optical structure comprising: a first optical interferometer structure and a second optical interferometer structure, and a first phase shifter. The first and second optical interferometer structures are optically connected, and each optical interferometer structure includes a first folded arm and a second folded arm. The first folded arms of the two optical interferometer structures are located on a first side of the optical structure and share the first phase shifter. The second folded arms of the two optical interferometer structures are located on a second side of the optical structure, wherein the second side is opposite to the first side. The first phase shifter is used to perform phase shifting on optical signals propagating in the first folded arm of the first optical interferometer structure and optical signals propagating in the first folded arm of the second optical interferometer structure.

Description

Technical Field

[0001] This invention relates to communication networks, and more particularly to optical communication networks. The invention proposes an optical structure and system for use as optical components in optical communication systems. Background Technology

[0002] Modern optical communication systems require components with high performance, low power consumption, and high tolerance to process variations, such as variable optical attenuators (VOAs), optical switches, and tunable optical filters (TOF).

[0003] However, achieving all the desired functionality simultaneously is challenging. The required functionality includes wavelength independence over a wide bandwidth, arbitrary initial VOA attenuation level or switching state, low power consumption, small footprint with large-scale integration, and robustness to manufacturing errors. Summary of the Invention

[0004] In view of the challenges discussed above, the present invention aims to provide a design for an optical structure and an optical structure system that satisfies all of the aforementioned challenges. One objective is to provide an optical structure that can be used for a wide range of functions. Another objective is to provide the optical structure with high tolerance to process-dependent variations in waveguide dimensions. Yet another objective is to achieve a small footprint for the optical structure.

[0005] These and other objectives are achieved by means of the invention, as described in the appended independent claims. Advantageous implementations are further specified in the dependent claims.

[0006] A first aspect of the present invention provides an optical structure comprising: a first optical interferometer structure, a second optical interferometer structure, and a first phase shifter. The first and second optical interferometer structures are optically connected, and each of the first and second optical interferometer structures includes a first folded arm and a second folded arm. The first folded arm of the first optical interferometer structure and the first folded arm of the second optical interferometer structure are located on a first side of the optical structure and share the first phase shifter. The second folded arm of the first optical interferometer structure and the second folded arm of the second optical interferometer structure are located on a second side of the optical structure, wherein the second side is opposite to the first side. The first phase shifter is used to perform phase shifting on an optical signal propagating in the first folded arm of the first optical interferometer structure and an optical signal propagating in the first folded arm of the second optical interferometer structure.

[0007] This invention proposes an optical structure with two folded optical interferometer arms on both sides (e.g., the top and bottom sides). Arms on the same side share the same phase shifter. Notably, the two arms on the same side achieve balanced / symmetrical phase shifting of the shared phase shifter through a folding mechanism. For example, the folded arms can have sufficient waveguide-waveguide spacing to avoid cross-coupling of optical waveguide modes.

[0008] This type of optical structure achieves low wavelength-dependent loss (WDL) over a wide bandwidth. Due to the integrated shared phase shifter, a uniform phase shift is consistently applied to the two folded arms of each distinct branch, ensuring synchronized phase modulation throughout the system. Therefore, the WDL of the first optical interferometer structure is almost entirely compensated for by the inverse WDL of the second optical interferometer structure in the transmission spectrum. Consequently, the overall WDL of the structure is effectively kept to a minimum, ensuring optimal performance over a wide optical bandwidth.

[0009] In one implementation of the first aspect, the optical structure further includes a second phase shifter, wherein the second folding arm of the first optical interferometer structure and the second folding arm of the second optical interferometer structure share the second phase shifter.

[0010] To make the top and bottom sides of the optical structure structurally symmetrical, a second phase shifter can be introduced. It is possible that the first phase shifter is a working phase shifter and the second phase shifter is a non-working (virtual) phase shifter.

[0011] In the implementation of the first aspect, the optical structure further includes an optical connection structure for optically connecting the first optical interferometer structure and the second optical interferometer structure, wherein the optical connection structure is a waveguide connection or a common coupler for receiving optical signals from the first folded arm and the second folded arm of the first optical interferometer structure and outputting the optical signals to the first folded arm and the second folded arm of the second optical interferometer structure.

[0012] In one implementation of the first aspect, the first folding arm and the second folding arm of the first optical interferometer structure have a first length difference, and / or the second folding arm and the first folding arm of the second optical interferometer structure have a second length difference.

[0013] In one implementation of the first aspect, the first length difference is associated with the wavelength of the optical signal propagating in the optical structure and the effective refractive index of the first or second folded arm of the first optical interferometer structure at the wavelength; and / or the second length difference is associated with the wavelength of the optical signal propagating in the optical structure and the effective refractive index of the first or second folded arm of the second optical interferometer structure at the wavelength.

[0014] In one implementation of the first aspect, the optical structure further includes: a first input port connected to the first optical interferometer structure, wherein the first input port is used to input an optical signal into the first optical interferometer structure; and a first output port connected to the second optical interferometer structure, wherein the first output port is used to output an optical signal from the second optical interferometer structure.

[0015] In this implementation, the optical structure is designed to have one input and one output.

[0016] In the implementation of the first aspect, the first optical interferometer structure further includes: a first splitter for splitting the optical signal received from the first input port to the first folded arm and the second folded arm of the first optical interferometer structure; and a first combiner for combining two optical signals received from the first folded arm and the second folded arm of the first optical interferometer structure into a combined optical signal, and outputting the combined optical signal to the second optical interferometer structure.

[0017] In one implementation of the first aspect, the second optical interferometer structure further includes: a second splitter for splitting the optical signal received from the first optical interferometer structure to the first folded arm and the second folded arm of the second optical interferometer structure; and a second combiner for combining two optical signals received from the first folded arm and the second folded arm of the second optical interferometer structure into a combined optical signal, and outputting the combined optical signal to the first output port.

[0018] Optionally, the combiner / splitter assembly within each optical interferometer structure can be adapted to various types of 1×2 couplers. Examples of such couplers include, but are not limited to, the Trident (adiabatic 1×2 coupler), the 1×2 multimode interferometer (MMI), the Y-junction, and directional couplers.

[0019] In one implementation of the first aspect, the optical structure further includes a second output port connected to the first optical interferometer structure, wherein the second output port is used to output an optical signal from the first optical interferometer structure.

[0020] In this implementation, the optical structure is designed to have one input and two outputs. The other "through" output port of the optical structure is connected via two low-loss waveguides cross-connected to a single waveguide that passes twice through the folded arm, allowing access to external circuitry.

[0021] In one implementation of the first aspect, the first combiner is a coupler, which is used to output the coupled optical signal from the first optical interferometer structure to the second output port.

[0022] The coupler assembly in the first optical interferometer structure is compatible with a range of 2×2 couplers. This includes, but is not limited to, 2×2 MMIs and directional couplers.

[0023] In one implementation of the first aspect, the first length difference is associated with the type of the coupler.

[0024] Optionally, the value of the first length difference depends on the type of 2×2 coupler used in the first optical interferometer structure.

[0025] In one implementation of the first aspect, the optical structure further includes: a second input port connected to the first optical interferometer structure, wherein the second input port is used to input an optical signal into the first optical interferometer structure; and a third output port connected to the second optical interferometer structure, wherein the third output port is used to output an optical signal from the second optical interferometer structure.

[0026] In this implementation, the optical structure is designed with two inputs and two outputs. The two outputs include a first output port and a third output port. The structure can be considered as consisting of two optical interferometer structures connected by a common 2×2 coupler.

[0027] In one implementation of the first aspect, the first optical interferometer structure further includes a first input coupler for receiving optical signals input from the first input port and the second input port, and outputting the optical signals to the first folded arm and the second folded arm of the first optical interferometer structure; the second optical interferometer structure further includes an output coupler for receiving optical signals from the first folded arm and the second folded arm of the first optical interferometer structure, and outputting the optical signals to the first output port and the third output port.

[0028] In one implementation of the first aspect, a first length difference is associated with a filtering function, and / or a second length difference is associated with a filtering function.

[0029] The value of the length difference depends on the filtering function to be implemented.

[0030] In one implementation of the first aspect, at least one of the first optical interferometer structure and the second optical interferometer structure includes a Mach-Zehnder interferometer (MZI) or an optical fiber.

[0031] In one implementation, the entire structure can be considered a planar optical waveguide circuit, consisting of two 2×2 MZIs. However, this cascaded configuration is not limited to planar waveguide platforms and is applicable to a wider range of optical technologies. This includes, but is not limited to, extensions to fiber optics, free-space optics, and other related fields.

[0032] In one implementation of the first aspect, the optical structure is one of the following: an optical switch, an optical attenuator, an optical filter, and a wavelength division multiplexer / demultiplexer.

[0033] The proposed optical structure is general and can be used for a range of functions. These functions include, but are not limited to, use as a VOA, optical switch, and TOF.

[0034] A second aspect of the present invention provides an optical structure system comprising at least two interconnected optical structures, wherein the at least two optical structures are optically connected via a common coupler, and each of the at least two optical structures is an optical structure according to the first aspect or any implementation thereof.

[0035] Optionally, the cascaded optical structure defined in the first aspect can be extended to a system comprising two or more identical cascaded optical structures interconnected in series by sharing a common 2×2 coupler between adjacent optical structures. Importantly, the term "identical" is used in this context to describe the overall structure itself, not necessarily the specific configuration of the individual components within these structures. For example, when two cascaded optical structures exist in the system, the first and second interferometer arms (from the first optical structure) share a phase shifter, and the third and fourth interferometer arms (from the second optical structure) share another phase shifter. It should be noted that while the two shared phase shifters are located on the same side within their respective structures, they are not required to be completely identical.

[0036] It should be noted that some of the devices, elements, units, and components described in this application can be implemented in software or hardware elements or any combination thereof. All steps performed by the various entities described in this application, as well as the functions to be performed by the various entities described, are intended to mean that the respective entities are suitable for or used to perform the corresponding steps and functions.

[0037] Although specific functions or steps performed by an external entity are not reflected in the description of the specific detailed elements of the entity performing the specific steps or functions in the following specific embodiments, those skilled in the art should understand that these methods and functions can be implemented in the corresponding software or hardware elements or any combination thereof. Attached Figure Description

[0038] The following description of specific embodiments, in conjunction with the accompanying drawings, illustrates various aspects and implementations of the present invention, as described in the drawings: Figure 1 An optical structure according to an embodiment of the present invention is shown; Figure 2 (a) shows a conventional dark-type MZI VOA; Figure 2 (b) to Figure 2(d) shows the simulation results of MZI VOA; Figure 3 An optical structure according to an embodiment of the present invention is shown; Figure 4 It shows Figure 3 Simulation results of the optical structure shown; Figure 5 It shows Figure 3 Simulation results of the optical structure shown; Figure 6 An optical structure according to an embodiment of the present invention is shown; Figure 7 It shows Figure 6 Simulation results of the optical structure shown; Figure 8 An optical structure according to an embodiment of the present invention is shown; Figure 9 An optical structure system according to an embodiment of the present invention is shown. Detailed Implementation

[0039] The following describes illustrative embodiments of optical structures and corresponding optical structure systems according to embodiments of the present invention with reference to the accompanying drawings. Although this description provides detailed examples of possible implementations, it should be noted that these details are merely exemplary and do not limit the scope of this application.

[0040] Furthermore, one embodiment or example may refer to multiple other embodiments or examples. For instance, any descriptions mentioned in one embodiment or example, including but not limited to terms, elements, processes, explanations, and / or technical advantages, may also be applicable to multiple other embodiments or examples.

[0041] Figure 1 An optical structure 100 according to an embodiment of the present invention is shown. The optical structure 100 includes a first optical interferometer structure 101 (shown using dashed lines), a second optical interferometer structure 102 (shown using dashed lines), and a first phase shifter 103. The first optical interferometer structure 101 and the second optical interferometer structure 102 are optically connected.

[0042] Each of the first optical interferometer structure 101 and the second optical interferometer structure 102 includes a first folding arm and a second folding arm. The first folding arm of the first optical interferometer structure 101 and the first folding arm of the second optical interferometer structure 102 are located on a first side of the optical structure 100 and share a first phase shifter 103. The second folding arm of the first optical interferometer structure 101 and the second folding arm of the second optical interferometer structure 102 are located on a second side of the optical structure 100, wherein the second side is opposite to the first side.

[0043] The first phase shifter 103 is used to perform phase shifting on the optical signal propagating in the first folded arm of the first optical interferometer structure 101 and the optical signal propagating in the first folded arm of the second optical interferometer structure 102.

[0044] Therefore, this invention proposes an optical structure 100 with two folded optical interferometer arms on both sides (e.g., the top and bottom sides). Arms on the same side share the same phase shifter. The two arms on the same side can achieve balanced / symmetrical phase shifting of the two arms sharing the same phase shifter through a folding mechanism. For example, the folded arms can have sufficient waveguide-waveguide spacing to avoid cross-coupling of optical waveguide modes. The folded arms can be specifically designed to minimize insertion loss and filter out higher-order waveguide modes by using appropriate waveguide bending. Such a structure can be designed to optimize space utilization and significantly reduce the overall footprint.

[0045] In one implementation, the optical structure 100 may be a planar optical waveguide circuit consisting of two 1×1 MZIs connected by a single optical waveguide.

[0046] To facilitate understanding of this application, we will first introduce MZI, which primarily uses a heater as a thermo-optical phase shifter. MZI consists of two couplers and a phase delay waveguide, and is widely used in VOA, optical switches, and TOF in various planar waveguide platforms.

[0047] In such Figure 2 In the conventional dark-type MZI VOA shown in (a), a high extinction ratio (ER) should be used to block light when the tuning power is zero. Therefore, the two arms of the MZI should have λ / (2n) eff The length difference, or π phase shift, is used to block light that causes destructive interference at the combiner of the MZI.

[0048] Due to the dispersion of planar waveguides, the optical length difference is wavelength-dependent, therefore, wavelength-dependent length difference (WDL) is unavoidable in dark-type MZI VOAs with non-zero arm length differences. The WDL of a VOA increases with higher attenuation (e.g., ...). Figure 2 (b) Figure 2 (as shown in (c)). WDL also increases with the increase of VOA operating bandwidth, thereby reducing the attenuation accuracy of VOA. As the operating bandwidth increases, the ER of VOA also decreases rapidly.

[0049] In order to achieve all the desired functions at the same time, this invention proposes a planar waveguide structure that simultaneously satisfies all the above challenges.

[0050] In one embodiment, the optical structure 100 includes the following features: 1. Cascaded MZI configuration and folding MZI arm.

[0051] 2. The folded arms on the same side of each MZI are placed close to each other with just enough gaps to avoid waveguide-to-waveguide cross-coupling, thus sharing the same phase shifter.

[0052] 3. Optionally, the folding arm on the other side of each MZI is also placed close together in the same manner as the other side to share another phase shifter.

[0053] 4. Depending on the coupler and delay length in the MZI, the optical structure 100 can be used for various functions, such as VOA, optical switch, TOF, etc.

[0054] 5. The configuration of the optical structure 100 optimizes space utilization to achieve a small footprint.

[0055] Figure 3 An optical structure 100 according to an embodiment of the present invention is shown. Figure 3 The structure is based on Figure 1 The structure shown. Figure 1 The structural details of the illustrated embodiment, particularly the folding method of the arm, also apply to this situation and to the following embodiments.

[0056] In this embodiment, the optical structure 100 further includes a second phase shifter 104. The second folding arm of the first optical interferometer structure 101 and the second folding arm of the second optical interferometer structure 102 share the second phase shifter 104.

[0057] To achieve structural symmetry between the top and bottom sides of the optical structure, a second phase shifter 104 is introduced. The first phase shifter 103 can be considered a working phase shifter, and the second phase shifter 104 a non-working (virtual) phase shifter. It should be noted that in this embodiment, the first phase shifter 103 is used as a working phase shifter. However, regardless of whether the upper or lower phase shifter is designated as a working unit or a non-working (virtual) unit, the system's function remains consistent. That is, the second phase shifter 104 can also function as a working phase shifter, and the first phase shifter 103 as a virtual phase shifter. In this case, instead of the first phase shifter 103, the second phase shifter 104 is used to perform phase shifting on the optical signal propagating in the second folded arm of the first optical interferometer structure 101 and the optical signal propagating in the second folded arm of the second optical interferometer structure 102.

[0058] The MZI (i.e., optical interferometer structure 101 or 102) has two folded waveguide arms on both the top and bottom sides. The arms on the same side of the two MZIs share the same phase shifter (e.g., a thermo-optical heater), and each phase shifter has four waveguide channels.

[0059] In this optical structure 100, the first optical interferometer structure 101 and the second optical interferometer structure 102 are connected to the connecting waveguide 105 (shown in solid lines).

[0060] It should be noted that the first folded arm and the second folded arm of the first optical interferometer structure 101 have a first length difference. Optionally, the first length difference is related to the wavelength of the light signal propagating in the optical structure 100 and the effective refractive index of the first folded arm or the second folded arm of the first optical interferometer structure 101 at the wavelength.

[0061] The second folded arm and the first folded arm of the second optical interferometer structure 102 may have a second length difference. Similarly, the second length difference is related to the wavelength of the light signal propagating in the optical structure 100 and the effective refractive index of the first or second folded arm of the second optical interferometer structure 102 at the wavelength.

[0062] The difference in arm length between the first MZI and the second MZI is... The additional length is applied to different sides of the arms of the two MZIs, respectively. For either of the two MZIs, there is an additional length... A particular side of the arm will not affect the overall function or performance.

[0063] In this embodiment, the optical structure 100 further includes a first input port connected to the first optical interferometer structure 101 and a first output port connected to the second optical interferometer structure 102. The first input port is used to input an optical signal into the first optical interferometer structure 101, and the first output port is used to output an optical signal from the second optical interferometer structure 102.

[0064] The first optical interferometer structure 101 further includes a first splitter and a first combiner. The first splitter is used to split the optical signal received from the first input port to the first folded arm and the second folded arm of the first optical interferometer structure 101; the first combiner is used to combine the two optical signals received from the first folded arm and the second folded arm of the first optical interferometer structure 101 into a combined optical signal, and output the combined optical signal to the second optical interferometer structure 102.

[0065] The second optical interferometer structure 102 further includes a second splitter and a second combiner. The second splitter is used to split the optical signal received from the first optical interferometer structure 101 to the first folded arm and the second folded arm of the second optical interferometer structure 102; the second combiner is used to combine the two optical signals received from the first folded arm and the second folded arm of the second optical interferometer structure 102 into a combined optical signal, and output the combined optical signal to the first output port.

[0066] Optionally, the combiner / splitter assembly within each optical interferometer structure can be adapted to various types of 1×2 couplers. Examples of such couplers include, but are not limited to, trident (insulated 1×2 coupler), 1×2 MMI, Y-junction, and directional couplers.

[0067] This type of optical structure 100 achieves low WDL over a wide bandwidth. The use of a shared phase shifter (i.e., the first phase shifter 103) allows for uniform phase shifting to be consistently applied to the two folded arms of each different branch, ensuring synchronized phase modulation across the system. Therefore, the WDL of the first optical interferometer structure is largely compensated for by the inverse WDL of the second optical interferometer structure in the transmission spectrum. Thus, the overall WDL of the structure is effectively kept to a minimum, ensuring optimal performance over a wide optical bandwidth.

[0068] Figure 4 (a) to Figure 4 (d) shows the simulation results of the proposed optical structure. Figure 4 (a) and Figure 4 (b) shows the transmission spectrum simulation results of a cascaded MZI VOA with a common phase shifter under different MZI arm temperature differences ΔT and tuning current applied to the working heater. Figure 4 (c) shows the relationship between the simulated WDL (across the C-band) and the average attenuation of a cascaded MZI VOA with a shared phase shifter. Due to its low wavelength dependence, the initial attenuation level of this VOA also remains high over a wide optical bandwidth with a large initial tuning current, such as... Figure 4 As shown in (d). Figure 4 (d) shows the relationship between the simulated average attenuation level of a cascaded MZIVOA with a shared phase shifter in the C band and the tuning current applied to the working heater.

[0069] It has been recognized that the performance of conventional dark MZI VOAs is particularly susceptible to manufacturing errors. This sensitivity primarily stems from variations in the phase delay of the MZI, attributed to dimensional fluctuations in the waveguide caused by processing inconsistencies. In contrast, the structure presented in this invention demonstrates significant insensitivity to such manufacturing errors, thanks to the fact that the same arm length difference is used on the two cascaded MZIs, thereby mutually compensating for spectral response variations in the transmission spectrum caused by the same amount of manufacturing error applied to each MZI.

[0070] Figure 5 (a) to Figure 5 (c) shows the simulated transmission spectrum and WDL versus attenuation level of the proposed MZI VOA structure, with the waveguide dimensions (width and height) deviating from the target design by 6σ in fabrication angle. Specifically, Figure 5 (a) and Figure 5 (b) shows the transmission spectrum simulation results of a cascaded MZI VOA with a shared phase shifter (whose waveguide dimensions deviate from the target design by 6σ in process angle) under different MZI arm temperature differences ΔT and tuning current applied to the working heater. Figure 5(c) shows the relationship between the simulated WDL (across the C-band) and the average attenuation of a cascaded MZI VOA with a shared phase shifter, the waveguide dimensions of which deviate from the target design by 6σ in process angle.

[0071] By comparison, it was found that Figure 4(a) and Figure 5 (a) between Figure 4 (b) and Figure 5 (b) and Figure 4 The difference in spectral response between (c) and Figure 5(c) is small across all tuning currents and attenuation levels.

[0072] Figure 6 An optical structure 100 according to an embodiment of the present invention is shown. Figure 6 The structure is based on Figure 3 The structure shown.

[0073] In this embodiment, the optical structure 100 further includes a second output port connected to the first optical interferometer structure 101. The second output port is used to output an optical signal from the first optical interferometer structure 101.

[0074] In this embodiment, the entire optical structure 100 is a planar optical waveguide circuit, consisting of a 1×2 MZI (i.e., the first optical interferometer structure 101) and a 1×1 MZI (i.e., the second optical interferometer structure 102) connected between the "crossed" output port of the 1×2 MZI and the input port of the 1×1 MZI via a single optical waveguide. The first output port is called the "crossed" output port. The other "through" output port of the 1×2 MZI is connected to a single waveguide passing through the folded MZI arm twice via two low-loss waveguides to access an external circuit. The second output port is called the "through" output port.

[0075] In this embodiment, the first combiner of the first optical interferometer structure 101 is a coupler, which is used to output the combined optical signal from the first optical interferometer structure 101 to the second output port.

[0076] Similar to the embodiments described above, the combiner / splitter assembly within each optical interferometer structure can be adapted to various types of 1×2 couplers. Examples of such couplers include, but are not limited to, trident (insulated 1×2 coupler), 1×2 MMI, Y-junction, and directional couplers.

[0077] Optionally, the coupler assembly in the first optical interferometer structure 101 is compatible with a range of 2×2 couplers. This includes, but is not limited to, 2×2 MMIs and directional couplers.

[0078] Both the 1×1 MZI and the 1×2 MZI have two folded waveguide arms on the top and bottom sides. The arms on the same side of the two MZIs share the same phase shifter (i.e., the first phase shifter 103 and the second phase shifter 104), and each phase shifter has four waveguide channels.

[0079] The first MZI (1×2) arm has a length difference The top side of the MZI arm has an additional length. The value depends on the type of 2×2 coupler used in a 1×2 MZI; for example, for a 2×2 MMI, it is... This means that the first length difference is related to the type of coupler, the wavelength of the light signal propagating in the optical structure 100, and the effective refractive index of the first or second folded arm of the first optical interferometer structure 101 at the wavelength.

[0080] The second MZI (1×1) arm has a length difference The bottom side of the MZI arm has an additional length. That is, the second length difference is still related to the wavelength of the light signal propagating in the optical structure 100 and the effective refractive index of the first or second folded arm of the second optical interferometer structure 102 at the wavelength.

[0081] and Figure 3 Compared to the embodiments shown, Figure 6 The structure shown has an additional output port, out2, for optical switching, and another port, out1, for optical attenuation. The 2×2 coupler in the 1×2 MZI will add additional phase delay for cross-coupling. so as to pass Calculate the arm length difference of 1×2 MZI to achieve Total phase shift. Together with the cascaded 1×1 MZI, the In-Cross-Out1 optical route provides... Figure 3 Similar low WDL optical attenuation is described in the illustrated embodiment. The relationship between simulated transmission spectra and temperature / current tuning and WDL analysis is shown in [reference to relevant data]. Figure 7 (a) and Figure 7 As given in (b). Similar to the embodiment described above, the initial attenuation level of the optical switch at port Out1 remains high over a large initial tuning current range across a wide optical bandwidth (see...). Figure 7 (d)).

[0082] Figure 7 (a) and Figure 7 (b) shows the transmission spectrum simulation results of a cascaded MZI optical switch with a shared phase shifter under different MZI arm temperature differences ΔT and tuning current applied to the working heater. Figure 7(c) illustrates the relationship between the simulated WDL (across the C-band) and the average attenuation of a cascaded MZI optical switch with a shared phase shifter. Due to its low wavelength dependence, the initial attenuation level of the optical switch also remains high over a wide optical bandwidth with a large initial tuning current, such as... Figure 7 As shown in (d). Figure 7 (d) shows the relationship between the simulated average attenuation level of a cascaded MZI optical switch with a shared phase shifter in the C-band and the tuning current applied to the working heater.

[0083] Figure 8 An optical structure 100 according to an embodiment of the present invention is shown. Figure 8 The structure is based on Figure 3 or Figure 6 The structure shown is optical structure 100, which includes a first optical interferometer structure 101 and a second optical interferometer structure 102, which are connected by a common coupler 106.

[0084] The entire structure designed in this embodiment can be a planar optical waveguide circuit, consisting of two 2×2 MZIs connected by a common 2×2 coupler.

[0085] and Figure 6 Compared to the illustrated embodiment, the optical structure 100 further includes a second input port connected to the first optical interferometer structure 101, wherein the second input port is used to input an optical signal into the first optical interferometer structure 101. The optical structure 100 also includes a third output port connected to the second optical interferometer structure 102, labeled "Out2" in the figure, wherein the third output port is used to output an optical signal from the second optical interferometer structure 102. It should be noted that the name "third output port" used herein is only for distinguishing it from other optical interferometer structures. Figure 6 The “second output port” depicted in the illustrated embodiment is distinguished. This term does not imply that the optical structure 100 includes three output ports.

[0086] In this embodiment, the first optical interferometer structure 101 further includes a first input coupler for receiving optical signals input from the first input port and the second input port, and outputting the optical signals to the first folding arm and the second folding arm of the first optical interferometer structure 101.

[0087] The second optical interferometer structure 102 also includes an output coupler for receiving optical signals from the first folded arm and the second folded arm of the first optical interferometer structure 101, and outputting the optical signals to the first output port and the third output port.

[0088] It should be noted that the coupler assembly within the first optical interferometer structure 101, the second optical interferometer structure 102, or the common coupler 106 is compatible with a range of 2×2 couplers. This includes, but is not limited to, 2×2 MMIs and directional couplers (if both input ports or both output ports are present).

[0089] The input / output coupler in the structure can be any type of 1×2 coupler, such as a 1×2 MMI, a Y junction, or a trident (if only one input / output exists).

[0090] Both MZIs have two folded waveguide arms on the top and bottom sides. The arms on the same side of the two MZIs share the same phase shifter (e.g., a thermo-optical heater), and each phase shifter has four waveguide channels.

[0091] It is worth mentioning that, in this embodiment, both the first phase shifter 103 and the second phase shifter 104 are operational phase shifters. They are both used to perform phase shifting on the optical signal propagating in the MZI.

[0092] Determine the difference in arm length between two MZIs ( 1 and 2) The phase portion is applied to the arms of the two MZIs on the same side. 1 and The value of 2 depends on the filtering function to be implemented.

[0093] If the same phase shift needs to be applied to both MZI stages separately, the structure proposed in this embodiment supports identical phase shift control for both stages. The phase components are close together, resulting in minimal random phase variation. Low power consumption is achieved due to the efficient use of the phase shifter. Space utilization is optimized, resulting in a small footprint.

[0094] It should be noted that this structure can be repeated to use 2. N+1 couplers create a lattice MZI TOF, where N is the number of shared phase portions to be tuned.

[0095] Figure 9 An optical structure system 10 according to an embodiment of the present invention is shown. Figure 9 The optical structure system 10 is based on Figure 8 The structure is shown. Specifically, the optical structure system 10 includes at least two interconnected optical structures 100. The at least two optical structures 100 are optically connected in series via a shared common 2×2 coupler. Each of the at least two optical structures 100 is... Figure 8 The optical structure 100 shown.

[0096] In this invention, the cascaded optical structure 100 defined in the above embodiments can be extended to a system comprising two or more identical cascaded optical structures interconnected in series. Importantly, the term "identical" is used in this context to describe the overall structure itself, not necessarily the specific configuration of the individual components within these structures. For example, when two cascaded optical structures exist in the system, the first and second interferometer arms (from the first optical structure) share a phase shifter, and the third and fourth interferometer arms (from the second optical structure) share another phase shifter. It should be noted that although the two shared phase shifters are located on the same side within their respective structures, they are not required to be completely identical.

[0097] It should be understood that the concept of a shared phase shifter on two cascaded MZI arms also applies to other optoelectronic components using MZI structures in planar waveguide platforms, such as MZI-TOF (tunable optical filters) and MZI-WDM (wavelength division multiplexers). The cascaded MZI structure configurations disclosed herein are also applicable to applications outside of planar waveguide platforms, such as fiber optics and free-space optics.

[0098] In summary, this invention proposes a configuration of a cascaded optical interferometer structure (e.g., an MZI structure) and the arrangement of phase delays in each folded arm. This type of optical structure achieves low wavelength dependence, high attenuation levels, and a large extinction ratio over a wide optical bandwidth with a large initial tuning current range. The concept of phase tuning using a shared phase shifter on both folded MZI arms allows for very high tolerance of the spectral response to process-dependent waveguide size variations. It achieves high tuning efficiency and low power consumption. The folded optical waveguide wiring configuration maximizes space utilization, resulting in a small footprint.

[0099] This invention has been described in conjunction with various embodiments as examples and implementations. However, based on a study of the drawings, the invention, and the independent claims, those skilled in the art will be able to understand and implement other variations when practicing the claimed embodiments of the invention. In the claims and the description, the word "comprising" does not exclude other elements or steps, and the quantifier "a" does not exclude a plurality. A single element or other unit may fulfill the function of multiple entities or items listed in the claims. Listing certain measures in dissimilar dependent claims does not indicate that a combination of these measures cannot be used in advantageous implementations.

Claims

1. An optical structure (100), characterized in that, include: The first optical interferometer structure (101), the second optical interferometer structure (102), and the first phase shifter (103). The first optical interferometer structure (101) and the second optical interferometer structure (102) are optically connected, and each of the first optical interferometer structure (101) and the second optical interferometer structure (102) includes a first folding arm and a second folding arm. In this configuration, the first folding arm of the first optical interferometer structure (101) and the first folding arm of the second optical interferometer structure (102) are located on the first side of the optical structure (100) and share the first phase shifter (103). The second folding arm of the first optical interferometer structure (101) and the second folding arm of the second optical interferometer structure (102) are located on the second side of the optical structure (100), wherein the second side is opposite to the first side. The first phase shifter (103) is used to perform phase shifting on the optical signal propagating in the first folded arm of the first optical interferometer structure (101) and the optical signal propagating in the first folded arm of the second optical interferometer structure (102).

2. The optical structure (100) according to claim 1, characterized in that, It also includes a second phase shifter (104). The second folding arm of the first optical interferometer structure (101) and the second folding arm of the second optical interferometer structure (102) share the second phase shifter (104).

3. The optical structure (100) according to claim 1 or 2, characterized in that, It also includes an optical connection structure for optically connecting the first optical interferometer structure (101) and the second optical interferometer structure (102). The optical connection structure is a waveguide, or a common coupler (106) for receiving optical signals from the first folded arm and the second folded arm of the first optical interferometer structure (101) and outputting the optical signals to the first folded arm and the second folded arm of the second optical interferometer structure (102).

4. The optical structure (100) according to any one of claims 1 to 3, characterized in that, The first folding arm and the second folding arm of the first optical interferometer structure (101) have a first length difference, and / or the second folding arm and the first folding arm of the second optical interferometer structure (102) have a second length difference.

5. The optical structure (100) according to claim 4, characterized in that... The first length difference is associated with the wavelength of the optical signal propagating in the optical structure (100) and the effective refractive index of the first folded arm or the second folded arm of the first optical interferometer structure (101) at that wavelength; and / or The second length difference is associated with the wavelength of the optical signal propagating in the optical structure (100) and the effective refractive index of the first or second folded arm of the second optical interferometer structure (102) at that wavelength.

6. The optical structure (100) according to any one of claims 1 to 5, characterized in that, Also includes: A first input port is connected to the first optical interferometer structure (101), wherein the first input port is used to input an optical signal into the first optical interferometer structure (101). A first output port is connected to the second optical interferometer structure (102), wherein the first output port is used to output an optical signal from the second optical interferometer structure (102).

7. The optical structure (100) according to claim 6, characterized in that, The first optical interferometer structure (101) further includes: A first splitter is used to split the optical signal received from the first input port to the first folding arm and the second folding arm of the first optical interferometer structure (101); The first combiner is used to combine two optical signals received from the first folding arm and the second folding arm of the first optical interferometer structure (101) into a combined optical signal, and output the combined optical signal to the second optical interferometer structure (102).

8. The optical structure according to claim 6 or 7, characterized in that, The second optical interferometer structure (102) also includes: The second splitter is used to split the optical signal received from the first optical interferometer structure (101) to the first folding arm and the second folding arm of the second optical interferometer structure (102); The second combiner is used to combine two optical signals received from the first folding arm and the second folding arm of the second optical interferometer structure (102) into a combined optical signal, and output the combined optical signal to the first output port.

9. The optical structure (100) according to any one of claims 6 to 8, characterized in that, Also includes: A second output port is connected to the first optical interferometer structure (101), wherein the second output port is used to output an optical signal from the first optical interferometer structure (101).

10. The optical structure (100) according to claim 9, which is dependent on claim 7 or 8, is characterized in that, The first combiner is a coupler, which is used to output the coupled optical signal from the first optical interferometer structure (101) to the second output port.

11. The optical structure (100) according to claim 10, characterized in that, The first length difference is associated with the type of the coupler.

12. The optical structure (100) according to any one of claims 1 to 4 and 6, characterized in that, Also includes: A first input port is connected to the second optical interferometer structure (101), wherein the second input port is used to input the optical signal into the first optical interferometer structure (101). A third output port is connected to the second optical interferometer structure (102), wherein the third output port is used to output an optical signal from the second optical interferometer structure (102).

13. The optical structure (100) according to claim 12, characterized in that... The first optical interferometer structure (101) further includes a first input coupler for receiving optical signals input from the first input port and the second input port, and outputting the optical signals to the first folding arm and the second folding arm of the first optical interferometer structure (101); The second optical interferometer structure (102) further includes an output coupler for receiving optical signals from the first folding arm and the second folding arm of the first optical interferometer structure (101) and outputting the optical signals to the first output port and the third output port.

14. The optical structure (100) according to claim 12 or 14, characterized in that, The first length difference is associated with a filtering function, and / or the second length difference is associated with a filtering function.

15. An optical structure (100) system, characterized in that, It includes at least two interconnected optical structures (100), said at least two optical structures (100) being optically connected by a common coupler (106), each of said at least two optical structures (100) being the optical structure (100) of any one of claims 12 to 14.

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