Mach-zehnder interferometer tolerant to process and environmental variations

Abstract

The present disclosure relates to Mach-Zehnder interferometers that are tolerant to process and environmental variations, including a first waveguide having a first plurality of phase shift segments and a second waveguide coupled to the first waveguide by an input coupler at a first end of the second waveguide and an output coupler at a second end opposite the first end and having a second plurality of phase shift segments. To minimize the effects of process and / or environmental variations on the Mach-Zehnder interferometer, the first waveguide and the second waveguide are fabricated to be tolerant to various process and / or environmental variations. A first phase shift segment of the first waveguide and a first phase shift segment of the second waveguide form a corresponding pair, the first corresponding pair configured to provide a wavelength tolerance to a wavelength shift of an optical signal propagating through the first waveguide and the second waveguide caused by a first parameter.

Description

Technical Field Background Technology

[0002] A Mach-Zehnder interferometer is a device used to determine the relative phase shift between two collimated beams. Mach-Zehnder interferometers have a variety of applications, including but not limited to wavelength division multiplexing and demultiplexing. Summary of the Invention

[0003] According to one aspect described herein, a Mach-Zehnder interferometer is provided. The Mach-Zehnder interferometer includes: a first waveguide including a first plurality of phase-shifting segments; and a second waveguide coupled to the first waveguide via an input coupler at a first end of the second waveguide and an output coupler at a second end of the second waveguide opposite to the first end, the second waveguide including a second plurality of phase-shifting segments, wherein: the first segments of the first plurality of phase-shifting segments and the first segments of the second plurality of phase-shifting segments form a first pair, wherein the first pair is configured to provide wavelength tolerance for wavelength shifts of optical signals propagating through the first and second waveguides caused by a first parameter.

[0004] In some embodiments, the first parameter includes a variation in the width of the corresponding phase shift segment. In some embodiments, a first segment of a first plurality of phase shift segments in a first pair includes a first width and a first length; and a first segment of a second plurality of phase shift segments in a first pair includes a second width and a second length, wherein the second width and / or the second length is determined based on the first width and the first length to provide wavelength tolerance to the first parameter.

[0005] In some embodiments, a second segment of the first plurality of phase-shift segments and a second segment of the second plurality of phase-shift segments form a second pair; and the first pair and the second pair are configured to provide wavelength tolerance for wavelength shift of the optical signal caused by a second parameter. In some embodiments, the second parameter includes a variation in the height of the phase-shift segments in the first and second pairs. In some embodiments, the first and second waveguides include a plurality of pairs of segments from the first plurality of phase-shift segments and the second plurality of phase-shift segments; and the plurality of pairs are configured to provide wavelength tolerance for wavelength shift of the optical signal caused by a third parameter based on the entirety of at least a subgroup including the plurality of pairs.

[0006] In some embodiments, the third parameter includes temperature. In some embodiments, the Mach-Zehnder interferometer is formed on a temperature-insensitive material. In some embodiments, the temperature-insensitive material includes silicon nitride.

[0007] According to one aspect described herein, a wavelength division multiplexer is provided. The wavelength division multiplexer includes: a plurality of Mach-Zehnder interferometers, each configured to receive optical signals of different wavelengths to be combined into a single output, wherein: a first Mach-Zehnder interferometer of the plurality of Mach-Zehnder interferometers includes corresponding first and second waveguides having a plurality of phase shift segments; and the first Mach-Zehnder interferometer is configured to be wavelength tolerant, at least in part, to wavelength shifts in the optical signal caused by one or more parameters, based on the size of the corresponding phase shift segments.

[0008] In some embodiments, the one or more parameters include at least one of the following: a variation in the width of the phase shift segment, a variation in the height of the phase shift segment, the temperature of the environment in which the multiplexer is operating, and / or the pressure of that environment. In some embodiments, the wavelength division multiplexer is formed on a temperature-insensitive material. In some embodiments, the temperature-insensitive material includes silicon nitride.

[0009] According to one aspect described herein, a demultiplexer is provided. The demultiplexer includes: a plurality of Mach-Zehnder interferometers configured to receive optical signals of light having different wavelengths, and configured to separate the optical signals into a plurality of outputs based on the different wavelengths, wherein: a first Mach-Zehnder interferometer of the plurality of Mach-Zehnder interferometers includes a plurality of corresponding first and second waveguides having phase shift segments; and the first Mach-Zehnder interferometer is configured to be wavelength tolerant, at least in part, to wavelength shifts in the optical signal caused by one or more parameters, based on the size of the corresponding phase shift segments.

[0010] In some embodiments, the one or more parameters include at least one of the following: a variation in the width of the phase shift segment, a variation in the height of the phase shift segment, the temperature of the environment in which the demultiplexer is operating, and / or the pressure of that environment. In some embodiments, the demultiplexer is formed on a temperature-insensitive material. In some embodiments, the temperature-insensitive material includes silicon nitride. Attached Figure Description

[0011] Various aspects and embodiments of this application will be described with reference to the following figures. It should be understood that the figures are not necessarily drawn to scale. Items appearing in multiple figures are indicated by the same or similar figure numbers in all figures.

[0012] Figure 1 Exemplary Mach-Zehnder interferometers, tolerant of process and / or environmental variations according to some embodiments, are shown.

[0013] Figure 2 Exemplary Mach-Zehnder interferometers, tolerant of process and / or environmental variations according to some embodiments, are shown.

[0014] Figure 3 Exemplary Mach-Zehnder interferometers, tolerant of process and / or environmental variations according to some embodiments, are shown.

[0015] Figure 4 An exemplary photonic system is shown, according to some embodiments, which employs a wavelength division multiplexer and a demultiplexer to optically couple two photonic integrated circuits.

[0016] Figure 5 Exemplary wavelength division multiplexers employing multiple process- and / or environment-tolerant Mach-Zehnder interferometers are shown according to some embodiments.

[0017] Figure 6 Exemplary demultiplexers employing multiple process- and / or environment-tolerant Mach-Zehnder interferometers are shown according to some embodiments. Detailed Implementation

[0018] Fiber optic systems have evolved over the past few decades and have been applied in various fields, such as long-distance transmission, fiber-to-the-home (FTTH), and optical sensing applications. Optical transceivers, which transmit and / or receive optical signals, enable data transmission using optical signals with encoded data. For example, a portion of the input data can be used to modulate the amplitude of the optical signal (e.g., a specific wavelength of optical signal generated by a laser) to encode the input data into that optical signal. In many optical data transmission systems, multiple unidirectional single-mode fibers are used in parallel, each fiber for transmitting a single wavelength of optical signal, which can potentially limit the system's transmission capacity. Such links are based on standards and protocols that provide specifications for optical transceivers, such as the IEEE Ethernet standard and multi-source protocols. These standards may provide power, size, and cost standards optimized for specific form factors, such as quad small form factor (QSFP). The specifications defined in the standards may require low cost, low power consumption, high yield, and small form factor.

[0019] To further improve system capacity, wavelength division multiplexing (WDM) technology has been adopted, which enables the transmission of optical signals of multiple wavelengths using the same optical fiber channel. For example, a photonic system may include two or more photonic integrated circuits (PICs) optically connected via an optical fiber channel. The first PIC may employ a wavelength division multiplexer configured to receive multiple different wavelengths (λ1, λ2, ..., λ...). N The optical signals are encoded by data (e.g., by amplitude modulation) and output as a combined optical signal to the same fiber optic channel, which optically couples the two PICs. The second PIC may employ a demultiplexer configured to receive the combined optical signal and separate the optical signal of each wavelength to different output channels so that each optical signal can be detected and processed.

[0020] In many such optical systems, wavelength division multiplexers and demultiplexers can employ a series of Mach-Zehnder interferometers to route optical signals of different wavelengths to a common fiber optic channel. A Mach-Zehnder interferometer typically has two beamsplitters or other optical coupling elements and two optical paths (also referred to herein as “arms”) extending between the beamsplitters. The Mach-Zehnder interferometer can route an optical signal to one of two outputs based on the interference of the optical signals propagating in the two arms at a second beamsplitter, which can be adjusted by introducing a relative phase shift in one arm relative to the optical signal propagating in the other arm. For example, this phase shift can be introduced in a Mach-Zehnder interferometer by making one arm longer than the other. In other examples, the phase shift can also be introduced by using a thermal phase shifter or a PN-doped phase shifter. Mach-Zehnder interferometers can be fabricated to have a specific free spectral range (FSR) that depends on the path length difference between the two arms and the group refractive index of the waveguides in each arm, defining which wavelengths of optical signal can be routed to a specific output without interference. In this way, a Mach-Zehnder interferometer can be fabricated to route a series of different wavelengths of light to the same output.

[0021] The inventors have recognized and understood that conventional Mach-Zehnder interferometers can be sensitive to many different process and environmental variations, thereby diminishing their ability to correctly route optical signals with minimal signal loss. For example, the relative phase shift introduced by one arm of a Mach-Zehnder interferometer may be affected by variations in the width and / or height of the phase shift segment of the arm due to manufacturing processes, or by different environmental factors (such as temperature and pressure) present in the environment in which the Mach-Zehnder interferometer is located. Consequently, the wavelengths at which the Mach-Zehnder interferometer can operate without interference may shift, making the Mach-Zehnder interferometer less efficient or even unsuitable for specific applications using optical signals with a specific set of wavelengths. Accordingly, the inventors have developed a Mach-Zehnder interferometer configured to be tolerant of various process and / or environmental variations.

[0022] According to some aspects, a tolerant Mach-Zehnder interferometer includes an input coupler, an output coupler, and multiple optical arms extending between the input and output couplers. The optical arms may include one or more phase-shifting segments, wherein the arrangement and configuration of the phase-shifting segments enable the Mach-Zehnder interferometer to have wavelength tolerance to one or more process and / or environmental variations. For a single Mach-Zehnder interferometer to be tolerant to N process and / or environmental parameters (… s 1 , s 2 , … , s N In some embodiments, each arm may contain 2N-1 Each phase shift segment. For example, each Mach-Zehnder interferometer can be manufactured to be tolerant of variations in the width and height of various phase shift segments caused by the manufacturing process and / or environmental parameters (such as temperature and pressure). When applied to wavelength division multiplexers and demultiplexers, each multiplexer or demultiplexer may include multiple tolerant Mach-Zehnder interferometers. When each Mach-Zehnder interferometer is independently tolerant of various process and / or environmental variations, the ensemble of Mach-Zehnder interferometers constituting the multiplexer / demultiplexer is also tolerant.

[0023] To make each Mach-Zehnder interferometer tolerant of various process and / or environmental variations, phase shift segments in each arm can be fabricated to meet various conditions. Each phase shift segment in the first arm can be paired with a phase shift segment in the second arm. This maintains symmetry, ensuring that the phase shift caused by different process and environmental variations is the same in each arm, thus keeping the relative phase shift between the two arms identical. The center wavelength of each wavelength channel of the Mach-Zehnder interferometer may depend on the total phase difference between the two arms of the Mach-Zehnder interferometer and is given by the following formula: Formula 1

[0024] In this diagram, subscripts a and b represent the first and second arms of the Mach-Zehnder interferometer, respectively; m represents the phase shift segment in the arm; λ is the wavelength of the light signal propagating through the arm; and β is the known propagation constant of the phase shift segment.

[0025] To be tolerant of different process and / or environmental parameters, the following conditions can be met: Formula 2

[0026] When applied to Formula 1, we can obtain: Formula 3

[0027] in N is the total number of parameters that the Mach-Zehnder interferometer must tolerate, and n is the refractive index of a specific phase shift segment. In some embodiments, the conditions in Equation 2 can be minimized to below a threshold (e.g., (rather than completely eliminating it. Due to the effective refractive index of a specific phase shift segment.) n The dependencies of various parameters (the phase shift segment is made of a specific material and has specific dimensions) are known; the only unknown in Equation 3 is... and Given the free spectral range equation for the Mach-Zehnder interferometer: Formula 4

[0028] in ΔL It is the optical path difference between the two arms ( ), s and q These are scaling factors for different phase shift segment lengths. Given these two equations, the length of the phase shift segment can be determined, thus satisfying the conditions given in Formula 2.

[0029] To provide tolerance for a single process or environmental parameter (e.g., N=1), Equation 3 can be simplified to:

[0030] For each phase shift segment ( m = 1，2，…，M Therefore, the length of each corresponding phase shift segment can be determined, making the phase shift segment tolerant of first process or environmental parameters. In some embodiments, the conditions in simplified Equation 3 can be minimized to below a threshold, rather than eliminated completely. For example:

[0031] in It is due to the change in the first parameter This causes a wavelength shift. In some embodiments, the threshold may be 1 nm.

[0032] In some embodiments, to extend the tolerance to a second process or environmental parameter, the dimensions and configurations of two adjacent pairs can be adjusted to provide tolerance. When N=2, Equation 3 can be simplified to:

[0033] Where m1 corresponds to the phase shift segment of the first pair, and m2 corresponds to the phase shift segment of the second adjacent pair. Because and It has been determined that, to provide the first tolerance, the only unknown in simplified formula 3 is... and In this way, these two lengths can be determined similarly, so that adjacent pairs of corresponding phase shift segments have tolerance for the second process or environmental parameters.

[0034] The methods used to provide the first two tolerances can be similarly extended to make the Mach-Zehnder interferometer tolerant to many such process or environmental parameters, including but not limited to the width and height of the phase shift segment, temperature, and pressure. In some embodiments, to provide tolerance to N different parameters, the Mach-Zehnder interferometer may include 2 N-1 The corresponding phase shift segment.

[0035] However, in some embodiments, the techniques described above can be used in combination with other techniques to provide tolerance for some or all parameters. For example, the techniques outlined above can be used to provide height and width tolerance. Mach-Zehnder interferometers can also be implemented on temperature-insensitive materials (e.g., silicon nitride) to provide temperature tolerance without having to determine the dimensions of additional corresponding phase shift segments. However, in some embodiments, temperature tolerance can be provided in the same manner as other tolerances, thus making the Mach-Zehnder interferometer material-independent.

[0036] Figure 1 An exemplary Mach-Zehnder interferometer 100, tolerant of process and / or environmental variations according to some embodiments, is illustrated. In the illustrated embodiment, the Mach-Zehnder interferometer 100 includes an input coupler 112, an output coupler 114, a first arm 110A, and a second arm 110B extending between the input coupler 112 and the output coupler 114. The first arm 110A includes two phase shift segments 101A and 102A, and the second arm 110B includes two phase shift segments 101B and 102B. In some embodiments, each of the phase shift segments 101A and 102A may form a pair of phase shift segments 101 and 102. Thus, as described above, the Mach-Zehnder interferometer 100 can be manufactured to be tolerant of both process and / or environmental variations, for example, to variations in height and width.

[0037] Phase shift segments 101A-102B can be configured in any suitable manner to provide tolerance to various process and / or environmental variations. For example, in some embodiments, each phase shift segment can be formed of the same material. In some embodiments, the phase shift segments can be formed of silicon nitride or any other suitable material. In some embodiments, different phase shift segments can be formed of different materials. For example, counterpart 101 can be formed of a first material (e.g., silicon nitride), while counterpart 102 can be formed of a second material (e.g., lithium nitride). In other examples, phase shift segment 101A can be formed of a different material than phase shift segment 101B.

[0038] For any suitable material (or combination of materials), the size of the phase shift segment in each corresponding pair can be determined using Formula 3 above, so that each pair has tolerance to a first process or environmental parameter. For example, since the dependence of the material's refractive index on a specific parameter is known, the phase shift segment 101A can be manufactured with a first length L. a1 Thus, Formula 3 can be evaluated to determine the second length L of the corresponding phase shift segment 101B. b1This allows the response to 101 to be tolerant of specific parameters. As mentioned above, Formula 3 can then be evaluated to determine the size of the phase shift segment, making the overall size of the phase shift segment tolerant of second process and / or environmental parameters. For example, L is determined by evaluating Formula 3. a1 L b1 L a2 and L b2 The relative lengths can be adjusted to change the size of each of the phase shift segments 101A-102B so that adjacent pairs of 101 and 102 are tolerant of the second process and / or environmental parameters relative to each other.

[0039] In some embodiments, the first parameter may be the width variation along the phase shift segment caused by defects in the manufacturing process, and the second parameter may be the height variation of the phase shift segment caused by defects in the manufacturing process. However, the technique is not limited to this approach, and the Mach-Zehnder interferometer can be manufactured in any order to be tolerant to any two suitable parameters. For example, the first parameter may be height tolerance, and the second parameter may be width tolerance. In other examples, the first parameter may be an environmental parameter, such as temperature or pressure variation, and the second parameter may be a process parameter, such as height or width tolerance.

[0040] In the illustrated embodiment, the Mach-Zehnder interferometer 100 can be manufactured to be tolerant of two process and / or environmental variations by determining the dimensions of the phase shift segments 101A-102B. To be more tolerant of process and environmental variations, more phase shift segments can be included, the dimensions of which can be determined according to Formula 3, as with the first two parameters. However, in some embodiments, the Mach-Zehnder interferometer 100 can be tolerant of process and / or environmental variations by being formed on an insensitive material. For example, in some embodiments, instead of introducing additional phase shift segments, the Mach-Zehnder interferometer 100 can be made tolerant of temperature variations by being formed on a temperature-insensitive silicon photonic substrate. In some embodiments, the temperature-insensitive silicon photonic substrate is formed of silicon nitride. In some embodiments, the silicon photonic substrate can become temperature-insensitive by including a cladding material. This cladding material may have a temperature coefficient opposite to that of the silicon photonic substrate to mitigate temperature sensitivity.

[0041] Figure 2 An exemplary Mach-Zehnder interferometer 200, tolerant of process and / or environmental variations according to some embodiments, is shown. As mentioned above, tolerance to more process and / or environmental parameters or variations can be provided by including additional phase shift segments, the dimensions of which can be determined according to Formula 3. In the illustrated embodiment, the Mach-Zehnder interferometer 200 can be manufactured to be tolerant of three process and / or environmental parameters.

[0042] The corresponding lines for each phase shift segment, 201-204, can be combined as described above. Figure 1 The aforementioned components are manufactured to be tolerant of first process and / or environmental parameters. Then, each adjacent pair (e.g., adjacent pairs 201 and 202, 203 and 204) can be combined as described above. Figure 1 They are all tolerant of each other regarding the second process and / or environmental parameters.

[0043] Finally, by evaluating the following simplified Formula 3 to take into account third process and / or environmental parameters, the overall response to 201-204 can be made more tolerant of third process and / or environmental parameters:

[0044] The above iterative evaluation process can be extended and used to manufacture Mach-Zehnder interferometers that are tolerant to N process and / or environmental parameters. Figure 3 An exemplary Mach-Zehnder interferometer 300, tolerant of process and / or environmental variations according to some embodiments, is illustrated. In the illustrated embodiment, the Mach-Zehnder interferometer 300 includes M phase shift segments corresponding to each other. In some embodiments, to be tolerant of N process and / or environmental parameters, the Mach-Zehnder interferometer 300 may include M=2. N-1 Corresponding phase shift segments. Thus, Formula 3 can be used to evaluate the dimensions of various phase shift segments, thereby making the Mach-Zehnder interferometer tolerant to N process and / or environmental parameters.

[0045] As described above, the tolerant Mach-Zehnder interferometer described herein can be implemented as part of a photonic system to facilitate one or more functions of the photonic system. For example, the Mach-Zehnder interferometer can be used in a photonic system for amplitude or phase modulation of an input optical signal, and / or for multiplexing and demultiplexing functions. Figure 4 An exemplary photonic system 400 is shown according to some embodiments, employing a wavelength division multiplexer and a demultiplexer to optically couple two photonic integrated circuits (PICs). In the illustrated embodiment, the photonic system 400 includes a first PIC 410, a second PIC 420, and an optical fiber 418 optically coupling the first PIC 410 and the second PIC 420.

[0046] The first PIC 410 is configured to transmit an optical signal from the photonic system 400 to the second PIC 420. In some embodiments, the optical signal can be generated by modulating the amplitude of light provided by a light source (such as laser source 412). Data received in the data module 411 may cause the electrical driver 413 to control the optical modulator 414. By controlling the optical modulator 414, the optical signal received from the laser source 412 can be encoded with information indicating the data received by the data module 411, for example, by modulating the amplitude of the optical signal over time. In some embodiments, the optical modulator 414 can be implemented using a Mach-Zehnder interferometer as described herein. To control modulation, the Mach-Zehnder interferometer for the optical modulator may include a thermal phase shifter and / or a PN junction phase shifter to provide slow or fast modulation, respectively.

[0047] In the illustrated embodiment, the first PIC 410 includes multiple data modules 411, an electrical driver 413, an optical modulator 414, and a laser source 412. Each laser source 412 can be configured to generate different wavelengths (e.g., λ1, λ2, …, λ). N The first PIC 410 can encode different portions of the received data in optical signals with different wavelengths. When the optical signals have different wavelengths, they can be transmitted through the optical fiber 418 in any suitable manner without interfering with each other. For example, different optical signals can be transmitted through the optical fiber 418 simultaneously, nearly simultaneously, or interleaved, with minimal interference between the different optical signals.

[0048] To facilitate the transmission of optical signals through the same optical fiber 418, the first PIC 410 includes a wavelength division multiplexer (WDM) 416. The WDM 416 can be configured to receive optical signals of different wavelengths from the optical modulator 414 and combine these optical signals into a combined optical signal. In some embodiments, the WDM 416 may include multiple tolerant Mach-Zehnder interferometers as described herein to perform wavelength division multiplexing.

[0049] The WDM 416 can be configured to support multiple wavelength "channels" to combine optical signals with wavelengths associated with each channel. For example, the WDM 416 can be configured to perform coarse WDM, supporting 18 different wavelength channels from 1270 nm to 1610 nm, with a channel spacing of 20 nm. Each input optical signal can have a wavelength at a different channel of the WDM 416. However, the WDM 416 can be configured in any suitable manner to support any suitable range of wavelength channels, including dense wavelength division multiplexing (supporting up to 80 channels) or ultra-dense wavelength division multiplexing (supporting up to or more than 160 channels), and can operate within any suitable frequency range.

[0050] The second PIC 420 is configured to receive an optical signal from the first PIC 410 via an optical fiber 418. The second PIC 420 may include one or more photodetectors 424 configured to generate electrical signals based on the detected optical signals; one or more data modules 421 for processing or transmitting received data encoded in the optical signals detected by the photodetectors 424; and one or more electrical amplifiers 422 to facilitate the processing or transmission of the received data.

[0051] Upon receiving the combined optical signal from the WDM 416 output, the second PIC 420 may further include a demultiplexer 426 configured to receive the combined optical signal and split it into multiple output optical signals according to the different wavelengths constituting the combined optical signal. For example, the demultiplexer 426 may separate the output optical signal at a first wavelength λ1 and provide it to a first photodetector 424, and the output optical signal at a second wavelength λ2 and provide it to a second photodetector 424. In this way, the data encoded by the optical modulator 414 in each optical signal can be separated and converted into output electrical signals by the corresponding photodetectors 424. Similar to the WDM 416, the demultiplexer 426 may include multiple tolerant Mach-Zehnder interferometers as described herein to perform the demultiplexing function of the demultiplexer 426.

[0052] Although in the illustrated embodiment, the first PIC 410 is configured to transmit optical signals to the second PIC 420 via optical fiber 416, the technology is not limited to this approach. For example, the first PIC 410 and the second PIC 420 may be configured to additionally or alternatively transmit and / or receive optical signals as described above. Furthermore, additional optical fibers may be used to optically couple the first PIC 410, the second PIC 420, and any other PICs not shown in the photonic system 400.

[0053] The Photonic System 400 can be configured to conform to one or more industry-defined optical signal transmission standards. Example standards include a 400Gb / s optical transceiver based on 4 channels x 100Gb / s four-level pulse amplitude modulation (PAM4). The four channels can be four parallel single-mode (PSM) fibers for a 500-meter range, and four wavelength division multiplexing (WDM) channels for 2km and 10km ranges over LAN WDM (channel spacing approximately 800 GHz / 4.5 nm) or coarse WDM (spacing approximately 20 nm). Typical optical connections described above and further herein may operate in the O-band, where dispersion of optical signals of different wavelengths propagating through optical fibers is minimal. The O-band wavelength can be approximately 1300 nm.

[0054] Figure 5An exemplary wavelength division multiplexer (WDM) 500 employing multiple process- and / or environment-tolerant Mach-Zehnder interferometers is illustrated according to some embodiments. In the illustrated embodiment, the WDM 500 includes multiple tolerant Mach-Zehnder interferometers arranged in a cascaded configuration, having a first stage 502, a second stage 504, and a third stage 506. Thus, the WDM 500 supports multiplexing of eight wavelengths. However, the WDM 500 can be configured in any suitable manner to support more or fewer wavelengths, including but not limited to adding additional stages or removing the first and / or second stages.

[0055] The first stage 502 may include four tolerant Mach-Zehnder interferometers 502A-502D. Each Mach-Zehnder interferometer 502A-502D may include two inputs to receive two optical signals of different wavelengths. For example, the Mach-Zehnder interferometer 502A may receive a first optical signal λ1 at the first input and a second optical signal λ2 at the second input. The Mach-Zehnder interferometer 502A may be configured to have a specific free spectral range (FSR) to route the two optical signals to the same output. In this way, the two input optical signals can be combined into the same output (e.g., as an intermediate optical signal). The intermediate optical signal output from the Mach-Zehnder interferometer 502A may be transmitted to a second-stage interferometer (e.g., 504A). Each of the first-stage interferometers 502B-D may be configured in a similar manner, each combining two of the eight input optical signals.

[0056] The second stage 504 may include two tolerant Mach-Zehnder interferometers 504A-504B. Each input of the Mach-Zehnder interferometers 504A-504B can be coupled to the relevant output of the Mach-Zehnder interferometers 502A-502D from the first stage 502. In this way, each second-stage interferometer is configured to receive two of the intermediate optical signals output from the first stage 502, totaling up to four different wavelengths. As with the first stage, each Mach-Zehnder interferometer can be configured to have an FSR to route the two intermediate optical signals to the same output. For example, each Mach-Zehnder interferometer of the WDM 500 can be configured to have the same FSR to maintain the same operating wavelength throughout the cascaded arrangement of the WDM 500.

[0057] The third stage 506 may include a single tolerant Mach-Zehnder interferometer 506. This Mach-Zehnder interferometer 506 may include two inputs, each coupled to a corresponding output of the second-stage interferometers 504A-504B. Thus, the Mach-Zehnder interferometer 506 can receive and combine two second-stage intermediate optical signals into a single combined optical signal for output. This combined optical signal may contain up to all eight wavelengths illustrated.

[0058] While the WDM 500 is described as having three stages to support eight wavelength channels, it is understood that the WDM 500 can be modified to support more or fewer channels to comply with the aforementioned industry-defined multiplexing standards, coarse wavelength division multiplexing (WDM), dense wavelength division multiplexing (DWDM), and / or ultra-dense wavelength division multiplexing (UHDDM). For example, one or more additional stages can be added to support additional wavelength channels, or stages can be removed to support only two or four wavelength channels. Furthermore, each Mach-Zehnder interferometer can be configured to have an FSR to support any of the aforementioned multiplexing schemes and / or industry-defined standards.

[0059] Furthermore, since the WDM 500 includes the above-mentioned combination Figure 1-3 The aforementioned tolerant Mach-Zehnder interferometer, the WDM500, can also be manufactured to be tolerant of the various process and / or environmental parameters that are tolerable to those Mach-Zehnder interferometers. For example, when each Mach-Zehnder interferometer is manufactured to be tolerant of height, width, temperature, and / or other suitable parameters, the collection of Mach-Zehnder interferometers constituting the WDM 500 will also be tolerant of these parameters.

[0060] Figure 6 An exemplary wave demultiplexer 600 employing multiple process- and / or environment-tolerant Mach-Zehnder interferometers is shown according to some embodiments. (In conjunction with the above) Figure 5 The same manner is described in the WDM 500. The demultiplexer 600 includes a first stage 602, a second stage 604, and a third stage 606 of Mach-Zehnder interferometers, which are configured to split a single input combined optical signal into multiple optical signals with different wavelengths.

[0061] The first stage 602 may include a single tolerant Mach-Zehnder interferometer 602 as described herein. The Mach-Zehnder interferometer 602 may be configured to receive an input combined optical signal (e.g., from fiber 418) and split the combined optical signal into two outputs. For example, the Mach-Zehnder interferometer 602 may be configured to have an FSR, enabling the interferometer to split the combined optical signal into a first intermediate signal (e.g., including λ1, λ2, λ3, and λ4, or including λ1, λ3, λ5, and λ7, or any suitable combination of incident optical signals) and a second intermediate signal (e.g., including λ5, λ6, λ7, and λ8, or including λ2, λ4, λ6, and λ8, or any suitable combination of incident optical signals). The second and third stages 604 and 606 may be configured to further split these intermediate signals, such that optical signals of each wavelength can be output separately.

[0062] Similar to the WDM 500, while the demultiplexer 600 is described as having three stages to support eight wavelength channels, it is understood that the demultiplexer 600 can be modified to support more or fewer channels to conform to the industry-defined multiplexing standards, coarse WDM, dense WDM, and / or ultra-dense WDM described above. For example, one or more additional stages can be added to support additional wavelength channels, or stages can be removed to support only two or four wavelength channels. Furthermore, each Mach-Zehnder interferometer can be configured to have an FSR to support any of the multiplexing schemes and / or industry-defined standards described above.

[0063] Furthermore, since the demultiplexer 600 includes the combination described above... Figure 1-3 The described tolerant Mach-Zehnder interferometer, demultiplexer 600, can also be manufactured to be tolerant of the various process and / or environmental parameters to which those Mach-Zehnder interferometers are tolerant. For example, when each Mach-Zehnder interferometer is manufactured to be tolerant of height, width, temperature, and / or other suitable parameters, the set of Mach-Zehnder interferometers constituting demultiplexer 600 will also be tolerant of these parameters.

[0064] Having described several aspects and embodiments of the technology described in this application, it should be understood that various modifications, alterations, and improvements will be apparent to those skilled in the art. These modifications, alterations, and improvements are intended to fall within the spirit and scope of the technology described in this application. Therefore, it should be understood that the foregoing embodiments are merely exemplary, and inventive embodiments may be practiced in ways different from those specifically described within the scope of the appended claims and their equivalents. Furthermore, any combination of two or more features, systems, articles, materials, and / or methods described herein, provided that such features, systems, articles, materials, and / or methods are not contradictory, is included within the scope of this disclosure.

[0065] Furthermore, as mentioned above, some aspects can be embodied as one or more methods. Actions performed as part of a method can be ordered in any suitable manner. Therefore, embodiments can be constructed that perform actions in a different order than described, which could include performing some actions simultaneously, even if they are shown as sequential actions in the illustrative embodiments.

[0066] All definitions in this document, as defined and used, should be understood to take precedence over dictionary definitions, definitions in incorporated documents by reference, and / or the general meaning of the defined terms.

[0067] The indefinite articles “a” and “an”, as used in this specification and claims, shall be understood to mean “at least one” unless expressly stated otherwise.

[0068] The phrase “and / or”, as used in this specification and claims, shall be understood to mean “either or both”, that is, elements that exist simultaneously in some cases and selectively in others.

[0069] As used in this specification and claims, the phrase "at least one" refers to a list of one or more elements and should be understood to mean at least one element selected from the elements in the list, but does not necessarily include at least one of every element specifically listed in the list, nor exclude any combination of elements in the list. This definition also allows for the possibility of other elements besides those specifically identified in the list of elements referred to by "at least one," whether or not these elements are related to the specifically identified element.

[0070] The terms "approximately" and "about" may refer to within ±20% of the target value in some embodiments, within ±10% of the target value in some embodiments, within ±5% of the target value in some embodiments, and within ±2% of the target value in other embodiments. The terms "approximately" and "about" may include the target value.

Claims

1. A Mach-Zehnder interferometer, comprising: The first waveguide includes multiple phase shift segments; as well as A second waveguide is coupled to the first waveguide via an input coupler at a first end of the second waveguide and an output coupler at a second end of the second waveguide opposite to the first end. The second waveguide includes a second plurality of phase shift segments, wherein: The first segment of the first plurality of phase shift segments and the first segment of the second plurality of phase shift segments form a first pair. The first pair is configured to provide wavelength tolerance for wavelength shift of the optical signal propagating through the first and second waveguides caused by the first parameter.

2. The Mach-Zehnder interferometer according to claim 1, wherein: The first parameter includes the width variation of the corresponding phase shift segment.

3. The Mach-Zehnder interferometer according to claim 2, wherein: The first segment of the first plurality of phase shift segments in the first corresponding pair includes a first width and a first length; and The first segment of the second plurality of phase shift segments in the first counterpart includes a second width and a second length, wherein the second width and / or the second length is determined based on the first width and the first length to provide wavelength tolerance for the first parameter.

4. The Mach-Zehnder interferometer according to claim 1, wherein: The second segment of the first plurality of phase shift segments and the second segment of the second plurality of phase shift segments form a second pair; and The first and second pairs are configured to provide wavelength tolerance for wavelength shift of the optical signal caused by the second parameter.

5. The Mach-Zehnder interferometer according to claim 4, wherein: The second parameter includes the variation in the height of the phase shift segment of the first and second pairs of pairs.

6. The Mach-Zehnder interferometer according to claim 4, wherein: The first waveguide and the second waveguide include multiple pairs of segments from the first plurality of phase shift segments and the second plurality of phase shift segments; and The plurality of pairs are configured to provide wavelength tolerance for wavelength shift of the optical signal caused by the third parameter, based on the whole of at least a subgroup comprising the plurality of pairs.

7. The Mach-Zehnder interferometer according to claim 6, wherein: The third parameter includes temperature.

8. The Mach-Zehnder interferometer according to claim 4, wherein: The Mach-Zehnder interferometer is formed on a temperature-insensitive material.

9. The Mach-Zehnder interferometer according to claim 8, wherein: The temperature-insensitive material includes silicon nitride.

10. The Mach-Zehnder interferometer according to claim 8, wherein: The temperature-insensitive material is a silicon substrate having a first temperature coefficient and includes a cladding material having a second temperature coefficient opposite to the first temperature coefficient.

11. A wavelength division multiplexer, comprising: Multiple Mach-Zehnder interferometers, each configured to receive optical signals of different wavelengths to be combined into a single output, wherein: The first Mach-Zehnder interferometer of the plurality of Mach-Zehnder interferometers includes corresponding first and second waveguides with multiple phase shift segments; and The first Mach-Zehnder interferometer is configured to be wavelength tolerant, at least in part, to wavelength shifts in the optical signal caused by one or more parameters, based on the size of the corresponding phase shift segment.

12. The wavelength division multiplexer according to claim 11, wherein: The one or more parameters include at least one of the following: the width variation of the phase shift segment, the height variation of the phase shift segment, the temperature of the environment in which the multiplexer is operating, and / or the pressure of the environment.

13. The wavelength division multiplexer according to claim 11, wherein: The wavelength division multiplexer is formed on a temperature-insensitive material.

14. The wavelength division multiplexer according to claim 13, wherein: The temperature-insensitive material includes silicon nitride.

15. The wavelength division multiplexer according to claim 13, wherein: The temperature-insensitive material is a silicon substrate having a first temperature coefficient and includes a cladding material having a second temperature coefficient opposite to the first temperature coefficient.

16. A demultiplexer, comprising: Multiple Mach-Zehnder interferometers are configured to receive optical signals with different wavelengths and to separate the optical signals into multiple outputs based on the different wavelengths, wherein: The first Mach-Zehnder interferometer of the plurality of Mach-Zehnder interferometers includes a plurality of corresponding first and second waveguides with phase shift segments; and The first Mach-Zehnder interferometer is configured to be wavelength tolerant, at least in part, to wavelength shifts in the optical signal caused by one or more parameters, based on the size of the corresponding phase shift segment.

17. The demultiplexer according to claim 16, wherein: The one or more parameters include at least one of the following: the width variation of the phase shift segment, the height variation of the phase shift segment, the temperature of the environment in which the demultiplexer is operating, and / or the pressure of the environment.

18. The demultiplexer according to claim 16, wherein: The demultiplexer is formed on a temperature-insensitive material.

19. The demultiplexer according to claim 18, wherein: The temperature-insensitive material includes silicon nitride.

20. The demultiplexer according to claim 18, wherein: The temperature-insensitive material is a silicon substrate having a first temperature coefficient and includes a cladding material having a second temperature coefficient opposite to the first temperature coefficient.

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