PATENT DOCUMENT

Publication Number: US-11832364-B2
Application Number: US-202117373167-A
Country: US
Kind Code: B2

Title: Systems and methods for wavelength locking in optical sensing systems

Abstract:
Disclosed herein is an integrated photonics device including a frequency stabilization subsystem for monitoring and/or adjusting the wavelength of light emitted by one or more light sources. The device can include one or more selectors that can combine, select, and/or filter light along one or more light paths, which can include light emitted by a plurality of light sources. Example selectors may include, but are not limited to, an arrayed waveguide grating (AWG), a ring resonator, a plurality of distributed Bragg reflectors (DBRs), a plurality of filters, and the like. Output light paths from the selector(s) can be input into one or more detector(s). The detector(s) can receive the light along the light paths and can generate one or more signals as output signal(s) from the frequency stabilization subsystem. A controller can monitor the wavelength and can adjust or generate control signal(s) for the one or more light sources to lock the monitored wavelength to a target wavelength (or within a targeted range of wavelengths).

Claims:
What is claimed is: 
     
       1. A system, comprising:
 a light source that emits light along an input light path; 
 a selector configured to:
 receive light along the input light path; 
 output light of a first wavelength along a first output; and 
 output light of a second wavelength along a second output; 
 
 a first attenuator connected to the first output; 
 a second attenuator connected to the second output; and 
 a detector connected to the first attenuator and the second attenuator to receive light from the first output and the second output, respectively, wherein: 
 the detector generates a signal indicative of measured light from both the first output and the second output. 
 
     
     
       2. The system of  claim 1 , wherein:
 the first attenuator modulates the light of the first wavelength at a first frequency; and 
 the second attenuator modulates the light of the second wavelength at a second frequency different than the first frequency. 
 
     
     
       3. The system of  claim 2 , further comprising:
 a controller, wherein:
 the controller receives the signal from the detector; 
 determines a monitored wavelength from the signal; 
 determines a difference between the monitored wavelength and a targeted wavelength; and 
 controls the light source based on the determined difference. 
 
 
     
     
       4. The system of  claim 1 , wherein the selector comprises an arrayed waveguide grating. 
     
     
       5. The system of  claim 1 , wherein the selector comprises a set of ring resonators. 
     
     
       6. The system of  claim 1 , wherein the selector comprises a splitter connected to a plurality of distributed Bragg reflectors. 
     
     
       7. The system of  claim 1 , wherein the first attenuator and the second attenuator each comprise a variable optical attenuator. 
     
     
       8. The system of  claim 1 , comprising:
 a plurality of light sources that includes the light source that emit light along a plurality of input light paths; and 
 a frequency stabilization subsystem configured to:
 multiplex light received from the plurality of input light paths along a common light path; 
 direct light of a first wavelength received from the plurality of input light paths along the first output to the detector; 
 direct light of a second wavelength received from the plurality of input light paths along the second output to the detector; and 
 output the signal from the detector. 
 
 
     
     
       9. The system of  claim 8 , further comprising:
 a controller, wherein:
 the controller receives the signal from the detector; 
 determines a monitored wavelength from the signal; 
 determines a difference between the monitored wavelength and a targeted wavelength; and 
 controls a light source of the plurality of light sources based on the determined difference. 
 
 
     
     
       10. The system of  claim 9 , wherein the frequency stabilization subsystem comprises:
 the first attenuator, wherein the first attenuator is configured to modulate the light of the first wavelength received from the plurality of input light paths; and 
 the second attenuator, wherein the second attenuator is configured to modulate the light of the second wavelength received from the plurality of input light paths. 
 
     
     
       11. The system of  claim 10 , wherein the first attenuator and the second attenuator modulate at different frequencies. 
     
     
       12. The system of  claim 10 , wherein the first attenuator and the second attenuator each comprise a variable optical attenuator. 
     
     
       13. The system of  claim 8 , wherein the frequency stabilization subsystem comprises an arrayed waveguide grating. 
     
     
       14. The system of  claim 8 , wherein the frequency stabilization subsystem comprises a multiplexer. 
     
     
       15. The system of  claim 14 , wherein the multiplexer light directs light emitted from the light source to the selector along the input light path. 
     
     
       16. A method, comprising:
 emitting light from a light source along an input light path; 
 receiving, by a selector, light along the input light path; 
 outputting, from the selector, light of a first wavelength along a first output; 
 outputting, from the selector, light of a second wavelength along a second output; 
 receiving, at a detector, the light of the first wavelength and the light of the second wavelength; 
 outputting a signal from the detector; and 
 controlling the light source based on the signal output by the detector. 
 
     
     
       17. The method of  claim 16 , wherein controlling the light source based on the signal output by the detector comprises:
 determining a monitored wavelength from the signal output by the detector; 
 determining a difference between the monitored wavelength and a targeted wavelength; and 
 controlling the light source based on the determined difference. 
 
     
     
       18. The method of  claim 16 , further comprising:
 modulating the light of the first wavelength at a first frequency; and 
 modulating the light of the second wavelength at a second frequency different than the first frequency. 
 
     
     
       19. The method of  claim 16 , wherein the selector comprises an arrayed waveguide grating. 
     
     
       20. The method of  claim 18 , wherein the selector comprises a set of ring resonators.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/582,949, filed Sep. 25, 2019, which is a nonprovisional of, and claims the benefit under 35 USC 119(e) of, U.S. Patent Application No. 62/738,649, filed Sep. 28, 2018, the contents of which are incorporated herein by reference as if fully disclosed herein. 
    
    
     FIELD 
     This disclosure relates generally to optical sensing systems. More particularly, this disclosure relates to methods for wavelength locking and associated optical sensing systems. 
     BACKGROUND 
     Optical sensing systems can be useful for many applications. In some instances, it may be useful to measure the optical properties of light emitted by light sources included in the optical sensing systems. For example, the optical properties of emitted light can be monitored to ensure that a light source is tuned to a target wavelength and/or has a certain amount of wavelength stability. 
     In some examples, the light sources can emit light having different properties such as different wavelengths. The emitted light can propagate along one or more light paths. The optical sensing system can also include one or more multiplexers for combining the emitted light along the light paths, where the multiplexer(s) can be component(s) separate from those measuring the optical properties of the emitted light. Separate components for the two functions may increase the size, cost, and complexity of the optical sensing system. 
     SUMMARY 
     Disclosed herein is an integrated photonics device including a frequency stabilization subsystem for monitoring and/or adjusting the wavelength of light emitted by one or more light sources. The device can include one or more selectors which can combine, select, and/or filter light along one or more light paths, wherein the light can include light emitted by a plurality of light sources. Selectors may include, but are not limited to, an arrayed waveguide grating (AWG), a ring resonator, a plurality of distributed Bragg reflectors (DBRs), a plurality of filters, and the like. Output light paths from the selector(s) can be input into one or more detector(s). The detector(s) can receive the light along the light paths and can generate one or more signals as output signal(s) from the frequency stabilization subsystem. A controller can monitor the wavelength and can adjust or generate control signal(s) for the one or more light sources to lock the monitored wavelength to a target wavelength (or within a targeted range of wavelengths). 
     A system is disclosed which may include at least a plurality of light sources that may emit a light in response to one or more control signals, where the light may propagate along one or more first light paths, a frequency stabilization subsystem that may receive at least a portion of the one or more first light paths, where the frequency stabilization subsystem may include one or more selectors that combine, select, filter, or a combination thereof, of at least a portion of the one or more first light paths, and one or more detectors that may receive light along one or more second light paths from the one or more selectors and may generate one or more signals. In some examples, the one or more signals may be one or more outputs from the frequency stabilization subsystem. The frequency stabilization subsystem may also include a controller that may receive the one or more signals from the frequency stabilization subsystem, may determine a monitored wavelength from the one or more signals, may determine a difference between the monitored wavelength and a targeted wavelength, and may generate the one or more control signals based on the difference. 
     Additionally or alternatively, in some examples, the one or more selectors may include an arrayed waveguide grating (AWG), the AWG including a plurality of waveguides, where at least two of the plurality of waveguides may have different lengths. The AWG may output the light along the one or more second light paths having different phase shifts. Additionally or alternatively, in some examples, the frequency stabilization subsystem may include a plurality of attenuators coupled to the AWG and the one or more detectors, the plurality of attenuators modulating the light along the one or more second light paths at different frequencies. Additionally or alternatively, in some examples, the one or more selectors may include a first ring resonator and a second ring resonator, the first ring resonator including a first looped waveguide which may optically couple at least a portion of the one or more first light paths having a first set of wavelengths, and the second ring resonator including a second looped waveguide which may optically couple at least a portion of the one or more first light paths having a second set of wavelengths. 
     Additionally or alternatively, in some examples, the one or more selectors may include a distributed Bragg reflector (DBR) component, the DBR component including a first DBR having a first structure that outputs at least a portion of the one or more first light paths having a first set of wavelengths, and a second DBR that outputs the at least the portion of the one or more first light paths having a second structure that outputs a second set of wavelengths. Additionally or alternatively, in some examples, the one or more selectors may include a filter component, the filter component including a waveguide, a first filter that filters at least a portion of the one or more first light paths having a first set of wavelengths, and a second filter that filters at least a portion of the one or more first light paths having a second set of wavelengths. Additionally or alternatively, in some examples, the one or more selectors may include one or more of a resonator, a multiplexer, an echelle grating multiplexer, a Mach-Zehnder interferometer, a Fabry-Perot cavity, a nanobeam cavity, and so forth. Additionally or alternatively, in some examples, the one or more detectors may include a single detector, and the one or more selectors may be coupled to different sides of the single detector. 
     Additionally or alternatively, in some examples, the one or more selectors may include one or more of an arrayed waveguide grating (AWG), a resonator, a distributed Bragg reflector (DBR) component, a filter component, a multiplexer, an echelle grating multiplexer, a Mach-Zehnder interferometer, a Fabry-Perot cavity, a nanobeam cavity and so forth. Additionally or alternatively, in some examples, the one or more detectors may include a twin waveguide detector having two waveguides on a same substrate, where a spacing between the two waveguides may be less than a longitudinal dimension of a given waveguide. Additionally or alternatively, in some examples, the one or more selectors may include one or more sensors measuring a temperature of the one or more selectors and one or more heaters for adjusting the temperature of the one or more selectors. Additionally or alternatively, in some examples, the frequency stabilization subsystem may further include a multiplexer, the multiplexer receiving the one or more first light paths and outputting a third light path, the third light path being the at least the portion of the one or more first light paths, where the one or more selectors select from the third light path and output a fourth light path, the fourth light path included in the one or more outputs of the frequency stabilization subsystem. Additionally or alternatively, in some examples, the one or more selectors may select from the one or more first light paths and outputs a fourth light path, the fourth light path included in the one or more outputs of the frequency stabilization subsystem. Additionally or alternatively, in some examples, the frequency stabilization subsystem may further include a multiplexer, the multiplexer receiving the one or more first light paths and outputting a third light path, the frequency stabilization subsystem further including a splitter that receives the third light path and outputs a fourth light path and a fifth light path, the fourth light path included in the one or more outputs of the frequency stabilization subsystem, and the fifth light path being the at least the portion of the one or more first light paths. 
     A method for operating one or more light sources in an optical sensing system is disclosed. The method can include sending one or more control signals to one or more light sources, emitting light from the one or more light sources, where the emitted light is based on the one or more control signals, propagating at least a portion of the emitted light along one or more first light paths to a frequency stabilization subsystem, performing one or more of combining, multiplexing, filtering, and selecting at least a portion of the one or more first light paths using one or more selectors included in the frequency stabilization subsystem, receiving light along one or more second light paths by one or more detectors, generating one or more signals using the one or more detectors, the one or more signals indicative of the light along the one or more second light paths, determining a monitored wavelength from the one or more signals, determining a difference between the monitored wavelength and a target wavelength, and adjusting the one or more control signals to the one or more light sources based on the difference. 
     Additionally or alternatively, in some examples, the performance of one or more of combining, multiplexing, filtering, and selecting the at least the portion of the one or more first light paths may include creating a first phase shift in the at least the portion of the one or more first light paths having a first set of wavelengths using an arrayed waveguide grating (AWG) and creating a second phase shift in the at least the portion of the one or more first light paths having a second set of wavelengths using the AWG. Additionally or alternatively, in some examples, the performance of one or more of combining, multiplexing, filtering, and selecting the at least the portion of the one or more first light paths may include optically coupling at least the portion of the one or more first light paths having a first set of wavelengths using a first ring resonator and optically coupling the at least the portion of the one or more first light paths having a second set of wavelengths using a second ring resonator. Additionally or alternatively, in some examples, the method may further include determining the target wavelength by taking a ratio of the one or more signals and determining an overlapping wavelength of the one or more signals. Additionally or alternatively, in some examples, the method may further include measuring a temperature of the one or more selectors using one or more sensors, determining whether the temperature meets one or more temperature criteria, and in accordance with the temperature not meeting the one or more temperature criteria, adjusting the temperature using one or more heaters. 
     A method for forming an optical sensing system is disclosed. The method can include providing a plurality of light sources, the plurality of light sources emitting light that propagates along one or more first light paths, providing a controller, arranging the plurality of light sources to receive one or more control signals from the controller, forming a frequency stabilization subsystem and arranging the frequency stabilization subsystem to receive the one or more first light paths. In some examples, forming the frequency stabilization subsystem may include forming one or more selectors to combine, select, filter, or a combination thereof at least a portion of the one or more first light paths, forming and arranging one or more detectors to receive light along one or more second light paths from the one or more selectors, arranging the one or more detectors to generate one or more outputs from the frequency stabilization subsystems, and arranging and connecting the controller to the frequency stabilization subsystem and the plurality of light sources. Additionally or alternatively, in some examples, forming the one or more selectors may include forming one or more of an arrayed waveguide grating (AWG), a ring resonator, a distributed Bragg reflector (DBR) component, a filter component, a multiplexer, an echelle grating multiplexer, a Mach-Zehnder interferometer, a Fabry-Perot cavity, a nanobeam cavity, and so forth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG.  1 A  illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that selects and outputs a light path; 
         FIG.  1 B  illustrates an example plot of multiple signals and a target wavelength; 
         FIG.  2    illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that combines multiple input light paths and outputs a selected light path; 
         FIG.  3    illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that receives light paths from a splitter; 
         FIG.  4    illustrates a block diagram of an example device including multiple frequency stabilization subsystems; 
         FIGS.  5 A- 5 B  illustrate block diagrams of example frequency stabilization subsystems including an arrayed waveguide grating and multiple detectors; 
         FIG.  6    illustrates a block diagram of an example frequency stabilization subsystem including ring resonators and multiple detectors; 
         FIGS.  7 A- 7 B  illustrate block diagrams of example frequency stabilization subsystems including a distributed Bragg reflector and multiple detectors; 
         FIGS.  8 A- 8 B  illustrate block diagrams of example frequency stabilization subsystems including a filter component and multiple detectors; 
         FIG.  9    illustrates a flow chart of an example operation of an optical sensing system having multiple detectors; 
         FIG.  10 A  illustrates a block diagram of an example frequency stabilization subsystem including an arrayed waveguide grating and a common detector; 
         FIG.  10 B  illustrates a block diagram of an example frequency stabilization subsystem including a ring resonator and a common detector; 
         FIG.  10 C  illustrates a block diagram of an example frequency stabilization subsystem including a distributed Bragg reflector component and a common detector; 
         FIG.  11    illustrates a cross-sectional view of an example detector including multiple waveguides formed on the same substrate; 
         FIG.  12    illustrates a block diagram of an example optical sensing system including a frequency stabilization subsystem including an arrayed waveguide grating and a detector; 
         FIG.  13 A  illustrates a block diagram of an example ring resonator and calibration components; and 
         FIG.  13 B  illustrates a block diagram of an example distributed Bragg reflector and calibration components. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented between them, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which are shown, by way of illustration, specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     Various techniques and process flow steps will be described in detail with reference to examples as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order not to obscure some of the aspects and/or features described or referenced herein. 
     Further, although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, a sequence or order of steps described in this disclosure does not, in and of itself, indicate a requirement that the steps be performed in that sequence or order. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its description in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     Various reference characters are used throughout the description for purposes of referring to one or more elements drawn in the figures. In some instances, a reference character may include numbers followed by a letter. Other reference characters may include the same numbers, but followed by a different letter. The description may refer to the group of elements by referring to the common numbers only, where no letter is appended. In such case, the reference to the group of elements means that the disclosed examples apply to one or more of the group of elements. 
     Disclosed herein is an integrated photonics device including a frequency stabilization subsystem for monitoring and/or adjusting the wavelength of light emitted by one or more light sources. The frequency stabilization subsystem can include selector(s) which can combine, select, and/or filter light along one or more light paths, which can include light emitted by a plurality of light sources. Example selectors may include, but are not limited to, an arrayed waveguide grating (AWG), a plurality of ring resonators, a plurality of distributed Bragg reflectors (DBRs), a plurality of filters, and the like. Output light paths from the selector(s) can be input into one or more detector(s). The detector(s) can receive the light along the light paths and can generate one or more signals as output signal(s) from the frequency stabilization subsystem. A controller can monitor the wavelength and can adjust or generate control signal(s) for the one or more light sources to lock the monitored wavelength to a target wavelength (or within a targeted range of wavelengths). 
     Representative applications of methods and apparatus according to the present disclosure are described in this section. These examples are being provided solely to add context and aid in the understanding of the described examples. It will thus be apparent to one skilled in the art that the described examples may be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be taken as limiting. 
     Example Frequency Stabilization Subsystems 
     In some examples, monitoring the optical properties of emitted light may employ the use of a frequency stabilization subsystem. The frequency stabilization subsystem can be used to verify whether the light sources are tuned to a target wavelength and/or have a certain amount of wavelength stability and, in some examples, make adjustments accordingly. The frequency stabilization subsystem  108  can be configured with one or more functions: multiplexing, combining, selecting, filtering, etc. In some examples, the number of components in the device  100  may include fewer or more components. 
     In some examples, the frequency stabilization subsystem can include a selector that selects and outputs light on a selected light path.  FIG.  1 A  illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that selects and outputs light on a light path. In  FIG.  1 A , an optical sensing system can include a device  100  which may include one or more light sources  102  and a multiplexer  146  which may be part of a frequency stabilization subsystem  108 . The light sources  102  can be configured to emit light along one or more light paths  144 . In some examples, the light sources  102  can be configured to emit light having different ranges of wavelengths. 
     The light paths  144  can be input into the frequency stabilization subsystem  108 . The frequency stabilization subsystem  108  may include a multiplexer  146 , a selector  110 , and one or more detectors  131 . The multiplexer  146  can receive the emitted light along the light path(s)  144  and can combine the emitted light to output light path  148 . The light path  148  can be input to the selector  110 . The selector  110  can select and output the light on light path  142 , which can be one of the outputs of the frequency stabilization subsystem  108 . The selector  110  can also generate outputs along the light paths  140  to the detectors  131 A and  131 B. The detectors  131 A and  131 B can receive the light paths  140  and output a signal or signals to a controller  112 . Even though the detectors  131 A and  131 B illustrate a combined, single output to the controller  112 , in some examples, an individual output from each of the detectors  131 A and  131 B may be output to the controller  112  such that the controller receives an output from detector  131 A and an output from detector  131 B. 
     The selector  110  can be a component that receives light via an input light path, selects light from the input light path, and outputs the selected light. In some examples, the selector  110  can output multiple light paths, which can include at least two different wavelengths (discussed below). For example, the selector  110  can receive light on the light path  148  as input and can output light along light paths  142  and  140 . The selector  110  can include one or more passive components such as a filter, resonator, multiplexer, an echelle grating multiplexer, an arrayed waveguide grating (AWG), Mach-Zehnder interferometer (MZI), a Fabry-Perot cavity, a nanobeam cavity, a ring resonator, a Distributed Bragg Reflector (DBR), or the like for combining, selecting, and/or filtering light. The terms “frequency stabilization” and “frequency stabilization subsystem” as used throughout this disclosure can refer to frequency stabilization, wavelength tuning, or both. 
     The detectors  131  can include any type of diode that can respond to or measure photons impinging on its active area. The detectors  131  can generate one or more signals indicative of the light along the light paths  140 ; these one or more signals can be an output signal or output signals from the frequency stabilization subsystem  108  to the controller  112 , for example. 
     Although  FIG.  1 A  illustrates the multiplexer  146  as included in the frequency stabilization subsystem  108 , examples may include the multiplexer  146  as being a component separate from the frequency stabilization subsystem  108  (not shown in  FIG.  1 A ). Examples of the device  100  can further include one or more additional components, such as filters, amplifiers, analog-to-digital converters (ADCs), etc. (not shown) located between the detector(s) and the controller  112 . These additional components can perform one or more operations on or with the signals from the detector(s) such as processing the signals, amplifying the signals, performing one or more calculations or comparisons, and so forth. 
     The signal(s) from the frequency stabilization subsystem  108  can be used as feedback in, for example, a control loop. The device  100  can also include a controller  112  that can receive and analyze the signal(s) from the frequency stabilization subsystem  108 . The controller  112  can generate one or more signals that can be inputs to the light sources  102 . In some examples, the analysis can include monitoring the wavelength of the emitted light as discussed herein and determining the difference between the monitored wavelength and a target wavelength. The controller  112  may be configured to lock the monitored wavelength to the target wavelength. 
     The signal(s) from the frequency stabilization subsystem  108  can be the same signals used to control the light sources  102  (e.g., control signal(s)) and the properties of light emitted by the light sources  102  along the light paths  144 . In some examples, the signal(s) from the frequency stabilization subsystem  108  can be indicative of changes in one or more properties (e.g., temperature, current, etc.) of the light sources  102 . The changes may be associated with locking the monitored wavelength to the target wavelength. In some examples, the controller  112  can use other information (e.g., measured temperature of the light sources  102 ) in generating the signal(s). 
     In some examples, the frequency stabilization subsystem  108  outputs multiple signals to the controller  112 . In such instances, the controller  112  can lock the wavelength at or near the crossing points (e.g., overlap) of the signals, as shown in  FIG.  1 B . In some examples, the wavelength locking may occur near the crossing points so long as signals  133 A and B exceed the target signal to noise ratio. Although not illustrated in  FIG.  1 B , in some examples, the wavelength outputs may generally approximate a Gaussian curve. The selector  110  can select light on light paths (from the input light path  148 ) that include sets of wavelengths. In some examples, at least two light paths can include one or more different wavelengths and one or more common wavelengths. A target wavelength  135  can be included in the common wavelength(s), and the selector  110  can select the light on the light paths, such that the range of wavelengths is close to the target wavelength  135 . For example, the selector  110  can select a first light path associated with signal  133 A and a second light path associated with signal  133 B. Signal  133 A can be the signal generated by the detector  131 A (in  FIG.  1 A ), and signal  133 B can be the signal generated by the detector  131 B (in  FIG.  1 A ). The first set of wavelengths may include wavelengths shorter than the target wavelength  135 , and the second set of wavelengths may include wavelengths longer than the target wavelength  135 . 
     The signals may have an intensity that varies with wavelength, and a maximum intensity (e.g., maximum current value) located at one of the wavelengths. The difference between the wavelength of the maximum intensity and the target wavelength  135  can be referred to as a wavelength spacing  137 . Although  FIG.  1 B  shows the wavelength spacings  137  for both signals  133 A and  133 B as being the same, examples may include different wavelength spacings  137 . In instances where the wavelength spacings  137  may differ from one another, the ratio of the signals may affect the location of the target wavelength  135 . 
     The controller  112  can receive the associated signals  133  and can lock the monitored wavelength to the target wavelength  135 , and the target ratio can be determined by taking the ratio of the signals  133 A and  133 B. If the monitored wavelength is not within a certain threshold wavelength from the target wavelength  135 , the controller  112  can adjust or send a new signal to the light sources  102  (or another controller that controls the light sources  102 ). 
     In some instances, the light sources  102  may emit light from at least two of the light sources at different times. For example, the light sources  102  can be activated sequentially, one at a time. The frequency stabilization subsystem  108  can monitor the wavelength of the emitted light, and the controller  112  can adjust the individual signals to one or more light sources. Alternatively, the controller  112  can receive signals from the detectors sequentially, and the controller can adjust the signals to the light sources in response to the plurality of sequentially received signals from the detectors. 
     Although  FIG.  1 B  illustrates the target wavelength  135  as being a single wavelength, examples may include a target range of wavelengths. In some instances, the target wavelength  135  may change during device operation, and the device  100  can be configured for locking to different target wavelengths at different times. Additionally or alternatively, the device can lock the monitored wavelength to a target ratio (which can be the ratio of the signals from the detectors). The target ratio may, in some examples, be different at different times. 
     In some examples, the frequency stabilization subsystem can include a selector that combines the input light on light paths along with selecting and outputting light on a selected light path.  FIG.  2    illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that combines light on multiple input light paths and outputs light on a selected light path. The device  200  can include one or more light sources  202  and a frequency stabilization subsystem  208 . The light sources  202  and its output light paths  244  can be correspondingly similar in functionality and structure as the light sources  102  and the light paths  144  of  FIG.  1 A , respectively. 
     Light on the light paths  244  can be input into the frequency stabilization subsystem  208 . The frequency stabilization subsystem  208  can include a selector  210  and one or more detectors  231 . The detectors  231  can be correspondingly similar in functionality and structure as the detectors  131  of  FIG.  1 A . 
     The selector  210  can be configured with multiple functions, such as the functions of the multiplexer  146  and the selector  110  of  FIG.  1 A . The selector  210  can receive the emitted light along the light paths  244  and can combine the emitted light. The selector  210  can select from the light combined on the emitted light path and output the selected light on light path  242 , which can be one of the outputs of the frequency stabilization subsystem  208 . The selector  210  can also output light along the light paths  240  to the detectors  231 A and  231 B, and the detectors  231 A and  231 B can output signals to a controller  212 . The controller  212  can be correspondingly similar in functionality and structure as controller  112  of  FIG.  1 A . Although the output signals of detectors  231 A and  231 B are illustrated in  FIG.  2    as being combined before being received by controller  212 , in some examples, the output signals of detectors  231 A and  231 B may be individual output signals separately received by the controller  212 . 
     In some examples, the frequency stabilization subsystem can include a selector that receives light paths from a splitter.  FIG.  3    illustrates a block diagram of a portion of an example integrated photonics device including a frequency stabilization subsystem, which can include a selector that receives light paths from a splitter. The device  300  can include one or more light sources  302  and a frequency stabilization subsystem  308 . The light sources  302  and its output light paths  344  can be correspondingly similar in functionality and structure as the light sources  102  and  144  of  FIG.  1 A , respectively. 
     The light paths  344  can be input into the frequency stabilization subsystem  308 . The frequency stabilization subsystem  308  can include a multiplexer  346 , a splitter  355 , a selector  310 , and one or more detectors  331 . The multiplexer  346  and the detectors  331  can be correspondingly similar in functionality and structure as the multiplexer  146  and detectors  131  of  FIG.  1 A , respectively. 
     The multiplexer  346  can receive the emitted light along the light paths  344  and can combine the emitted light on light path  348 . The light path  348  can be input to the splitter  355 . The splitter can split the light on light path  348  to output light on light path  342  and light path  338 . The light path  342  can be one of the outputs of the frequency stabilization subsystem  308 . 
     The light path  338  can be input to the selector  310 . The selector  310  can generate outputs of light along the light paths  340  to the detectors  331 A and  331 B. The detectors  331  can receive the light paths  340  and can output signals to a controller  312 . The controller  312  can be correspondingly similar in functionality and structure as controller  112  of  FIG.  1 A . 
     The splitter  355  can split the light along the light path  348  such that light along the light path  348  has a different proportion of light intensity than the light along the light path  338 . In some examples, the split can be such that light along the light path  338  includes a lower proportion (of light from the light path  348 ) than light along the light path  342 . For example, the light path  338  can include less than 10% of light from the light path  348 , and the light path  342  can include more than 90% of light from the light path  348 . 
     Although  FIG.  3    illustrates the multiplexer  346  as included in the frequency stabilization subsystem  308 , examples of the disclosure can include the multiplexer  346  as being a component separate from the frequency stabilization subsystem  308 . Examples of the disclosure can further include one or more additional components, such as filters, amplifiers, analog-to-digital converters (ADCs), etc. (not shown) located between the detector(s) and the controller  312 . These additional components can perform one or more operations on or with the signals from the detector(s) such as processing the signals, amplifying the signals, performing one or more calculations or comparisons, or any combination thereof, and so forth. 
     In some examples, the device can include multiple frequency stabilization subsystems for monitoring the wavelength of light emitted by multiple light sources, as shown in  FIG.  4   . Device  400  can include light sources  402 , a plurality of frequency stabilization subsystems  408 , and a controller  412  that are correspondingly similar in functionality and structure as device  100  (or device  200  or  300 ), light sources  102  (or light sources  202  or  302 ), frequency stabilization subsystems  108  (or frequency stabilization subsystems  208  or  308 ), and controller  112  (or controller  212  or  312 ), respectively of  FIGS.  1 A,  2   , and/or  3 . Similarly, light paths  444  and light path  442  can be correspondingly similar in functionality and structure as the light paths  144  (or light paths  244  or  344 ) of  FIGS.  1 A,  2   , and/or  3 . Although the frequency stabilization subsystems may be illustrated in  FIG.  4    as separate elements which are not communicating, in some examples, the frequency stabilization subsystems may be configured to communicate with one another as well as with other elements of device  400 . 
     Selector 
     Examples of the disclosure can include a selector that includes an AWG.  FIG.  5 A  illustrates a block diagram of a portion of an example frequency stabilization subsystem including an AWG and multiple detectors. Frequency stabilization subsystem  508 A can receive one or more light paths  541  as inputs and can generate one or more outputs, such as output  549 A, and output  549 B. In some examples, the frequency stabilization subsystem  508 A can include AWG  510 A and detectors  531 A and  531 B. The detectors  531  can be correspondingly similar in function and structure as detectors  131  of  FIG.  1 A . 
     The AWG  510 A can include a plurality of waveguides  515 A, where at least two waveguides can have different lengths. The phase shift induced by the different waveguides  515 A of different lengths can vary. The outputs of the AWG  510 A can have different phase shifts, which may be wavelength dependent. The light path  541  can include light having a plurality of wavelengths and can be multiplexed using the AWG  510 A. One output from the AWG  510 A, such as the one received by the detector  531 A, may include a first set of wavelengths, and another output from the AWG  510 B, such as the one received by the detector  531 B, may include a second set of wavelengths. For example, the output  549 A can include a first set of wavelengths, and the output  549 B can include a second set of wavelengths, where the first and second sets can include wavelengths that are different from the other set in addition to wavelengths that are common. In some examples, the sets of wavelengths can have a non-zero wavelength spacing (e.g., wavelength spacing  137  illustrated in  FIG.  1 B ) from the target wavelength (e.g., target wavelength  135  illustrated in  FIG.  1 B ). 
     The detector  531 A and the detector  531 B may receive light from the AWG  510 A and may generate signals indicative of the measured light. The signals may be transmitted along the output  549 A and the output  549 B. In some examples, the signals may be current signals. A controller (e.g., controller  112  illustrated in  FIG.  1 A ) may receive the output signals, may take the ratio of the signals, and may lock the monitored wavelength to a targeted wavelength by transmitting a signal to the light sources which may provide an adjustment to the light sources, for example, light sources  102  of  FIG.  1 A . 
     In some instances, the AWG may also output light along a light path, as shown in  FIG.  5 B . Frequency stabilization subsystem  508 B may include an AWG  510 B, which may be a selector that is configured to output light on a selected light path such as the light path  542 . The light path  542  may be an output of the frequency stabilization subsystem  508 B. The AWG  510 B can receive light on multiple light paths as inputs. For example, the light paths  144  of  FIG.  1 A  or the light paths  244  of  FIG.  2    may be connected to the light paths  541 . 
     As discussed herein, the selector in the frequency stabilization subsystem can include a ring resonator.  FIG.  6    illustrates a block diagram of a portion of an example frequency stabilization subsystem including one or more ring resonators and multiple detectors. 
     Frequency stabilization subsystem  608  can receive one or more light paths  641  as inputs and can generate one or more outputs, such as output  649 A and output  649 B. The frequency stabilization subsystem  608  can include a first ring resonator  610 A, a second ring resonator  610 B, and a plurality of detectors  631 A and  631 B. The detectors  631  can be correspondingly similar in function and structure as detectors  131  of  FIG.  1 A . 
     The ring resonators  610  can include waveguides. At least one waveguide can be a looped optical waveguide. At least one waveguide can be an input waveguide that receives the light path  641  as input, and two or more waveguides can be output waveguides. In some examples, the input and output waveguides may include the same structure. 
     Light from the light path  641  can travel through the input waveguide, and light can optically couple to a given output waveguide depending on its respective resonant mode. The first ring resonator  610 A can optically couple light having a first set of wavelengths and can output the light to the detector  631 A. The second ring resonator  610 B can optically couple light having a second set of wavelengths and can output the light to the detector  631 B. In this manner, both the first ring resonator  610 A and the second ring resonator  610 B can filter certain wavelengths of light which may pass through the ring resonators from the light path  641 . 
     The detector  631 A and the detector  631 B may receive light from the first ring resonator  610 A and the second ring resonator  610 B, respectively, and may generate signals indicative of the monitored light. The signals may be transmitted along output  649 A and output  649 B. In some examples, the signals may be current signals. A controller, for example, the controller  112  illustrated in  FIG.  1 A , may receive the signals, may take the ratio of the signals, and may lock the monitored wavelength to a targeted wavelength by transmitting a signal to the light sources which may provide an adjustment to the light sources, for example, light sources  102  of  FIG.  1 A . In some examples, multiple sets of ring resonators may be employed in the frequency stabilization subsystem. Different sets of ring resonators may have waveguides with different properties, such that different sets can be used at different times. 
     The selector in the frequency stabilization subsystem may also include a DBR component.  FIG.  7 A  illustrates a block diagram of a portion of an example frequency stabilization subsystem including a DBR component and multiple detectors. Frequency stabilization subsystem  708 A can receive light on one or more light paths  741  as input and can generate one or more outputs, such as output  749 A and output  749 B. The frequency stabilization subsystem  708 A can include a DBR component  710 A and the detectors  731 A and  731 B. The detectors  731  can be correspondingly similar in function and structure as detectors  131  of  FIG.  1 A . 
     In some examples, the DBR component  710 A can include a splitter  711  and a plurality of DBRs  713 . The splitter  711  can split the light received along the light path  741  into multiple outputs that can be received by the DBRs  713 . An example splitter can include, but is not limited to, a Y-junction splitter, a multi-mode interference (MMI) splitter, a directional coupler splitter, and the like. In some examples, the splitter  711  can split the input into any proportion such as 50% of the light along the light path  741  to DBR  713 A and 50% of the light along the light path  741  to DBR  713 B. The DBRs  713  can be configured as filters that allow certain wavelengths to propagate in its structure. The DBRs  713  can include a structure comprising multiple layers of materials having different refractive indices or different periodic characteristics. In some examples, the DBR  713 A may be configured as a different structure than the DBR  713 B, where the output to the detector  731 A can include a first set of wavelengths, and the output to detector  731 B can include a second set of wavelengths. For example, the DBR  713 A may include a stack of dielectric layers with different refractive indices than the stack of dielectric layers of the DBR  713 B. 
     The detector  731 A and the detector  731 B may receive light from the DBR component  710 A and may generate signals indicative of the measured light. The signals may be transmitted along output  749 A and output  749 B. In some examples, the signals may be current signals. A controller (e.g., controller  112  illustrated in  FIG.  1 A ) may receive the signals, take the ratio of the signals, and lock the monitored wavelength to the target wavelength by transmitting a signal to the light sources which may provide an adjustment to the light sources, for example, light sources  102  of  FIG.  1 A . 
     In some instances, the DBR component may also output light along a light path, as shown in  FIG.  7 B . Frequency stabilization subsystem  708 B may include a DBR component  710 B, which may be a selector that is configured to output a selected light path as the light path  742 . The light path  742  may be an output of the frequency stabilization subsystem  708 B. The DBR component  710 B can receive light on multiple light paths as inputs. For example, the light paths  144  of  FIG.  1 A  or the light paths  244  of  FIG.  2    may be connected to the light paths  741  of  FIG.  7   . 
     The selector in the frequency stabilization subsystem may also include a filter component.  FIG.  8 A  illustrates a block diagram of an example frequency stabilization subsystem which may include a filter component and multiple detectors. Frequency stabilization subsystem  808 A can receive light on one or more light paths  841  as inputs and can generate one or more outputs, such as output  849 A and output  849 B. The frequency stabilization subsystem  808 A can include a filter component  810 A and detectors  831 A and  831 B. The detectors  831  can be correspondingly similar in function and structure as detectors  131  of  FIG.  1 A . 
     In some examples, the filter component  810 A can include an optical component  815  and a plurality of filters  821 . In some examples, the optical component  815  can include a waveguide and a DBR, which can output a first set of light to the filter  821 A and a second set of light to the filter  821 B. The filter  821 A can filter the light to output a first set of wavelengths to the detector  831 A, and the filter  821 B can filter the light to output a second set of wavelengths to the detector  831 B. The detector  831 A and the detector  831 B may receive light from the filter component  810 A and may generate signals indicative of the measured light. The signals may be transmitted along output  849 A and output  849 B. In some examples, the signals may be current signals. A controller (e.g., controller  112  illustrated in  FIG.  1 A ) may receive the signals, take the ratio of the signals, and lock the monitored wavelength to a target wavelength by transmitting a signal to the light sources which may provide an adjustment to the light sources, for example, light sources  102  of  FIG.  1 A . 
     In some instances, the filter component may also output light along a light path, as shown in  FIG.  8 B . Frequency stabilization subsystem  808 B may include a filter component  810 B, which may be a selector that is configured to output light on a selected light path such as the light path  841 . The light path  841  may be an output of the frequency stabilization subsystem  808 B. The filter component  810 B can receive multiple light paths as inputs. For example, the light paths  144  of  FIG.  1 A  or the light paths  244  of  FIG.  2    may be connected to the light paths  841 . 
     As discussed herein, the illustrated block diagrams do not limit the configuration (e.g., location, size, orientation, etc.) of the optical routing lines and components. Examples of the disclosure can include other types of configurations not illustrated explicitly in the figures. Additionally or alternatively, the detector can be any type of detector, such as one that is discrete from the other components included in the frequency stabilization subsystem, or the detector may be an integrated component that is inseparable from the other components. 
     Operation of the Optical Sensing System 
       FIG.  9    illustrates a flow chart of an example operation of an optical sensing system having multiple detectors. At  952  of the process  950 , the controller can send one or more signals that control a plurality of light sources and at  954 , the plurality of light sources can receive the signal(s) and can emit light in response. The one or more signals from the controller can be indicative of one or more targeted properties of the light emitted by the plurality of light sources. At  956  of process  950 , a portion of the light emitted by the plurality of light sources can be directed using optics towards a system interface and at  958  another portion of the light (e.g., tapped light) emitted by the plurality of light sources can be directed towards a frequency stabilization subsystem. 
     At step  960  of process  950 , one or more selectors included in the frequency stabilization subsystem can combine, multiplex, select, and/or filter at least a part of the tapped light and at  962 , the selector can output light to the detectors. The light output to the detectors can have one or more unique properties such as different wavelengths, and so forth. At  964 , the detectors can receive the light and generate a signal indicative of the received light. The controller can receive and analyze the signals from the detectors at  966  and at  968  the controller can adjust the control signal(s) input to the plurality of light sources. 
     Common Detector Arrangement 
     A signal from a detector can drift over a given period of time (e.g., its lifetime). For example, the responsivity of a detector can drift. In instances where multiple detectors are used, the drifts of the multiple detectors may not be the same. The signals may include the respective drifts, which may not be detectable, and mathematical functions (e.g., taking the ratio) may not allow for accurate reduction or removal of these drifts from the signal(s). 
     In some examples, a common detector can be used to remove or reduce the detector drift.  FIG.  10 A  illustrates a block diagram of an example frequency stabilization subsystem including an AWG and a common detector. Frequency stabilization subsystem  1008 A can include an AWG  1010 A, one or more attenuators  1037 , and a detector  1031 . The AWG  1010 A can have one or more functions and/or characteristics similar to AWG  510 A illustrated in  FIG.  5 A . For example, the AWG  1010 A can include a plurality of waveguides  1015 A, where at least two waveguides can have different lengths. The AWG  1010 A can generate multiple outputs. A first output can be connected to the attenuator  1037 A, and a second output can be connected to the attenuator  1037 B. The attenuators  1037  can be variable optical attenuators (VOAs), for example. The attenuators  1037  can modulate the signals of the outputs from the AWG  1010 A at different frequencies. 
     The output from one attenuator, such as the attenuator  1037 A, can be connected to one side of the waveguide of the detector  1031 , and the output from another attenuator, such as the attenuator  1037 B, can be connected to the other side of the waveguide of the detector  1031 . The detector  1031  can receive the attenuated signals and can generate a signal on the output  1049 . In this manner, the same detector  1031  can be used for multiple outputs from the AWG  1010 A, and the amount of drift from the detector  1031  included in the output  1049  can be reduced or removed. In some examples, the frequencies that the attenuators  1037  modulate the signals by can differ by 180°. 
     Although  FIG.  10 A  illustrates one output  1049  from the frequency stabilization subsystem  1008 A, some examples may include using a selector that outputs light on a selected light path, such as AWG  510 B illustrated in  FIG.  5 B . 
     In examples where the multiplexer is a component separate from the selector, one light path can be a focal point of an adjacent grating order of the AWG  1010 A, and another light path can be multiplexed into the main grating order. For example, referring to  FIG.  5 B , the light paths to the detectors  531 A and B can be the focal point of the adjacent grating order, and the light path  542  can be multiplexed into the main grating order. The properties (e.g., pitch and width) of the AWG  1010 A can be optimized such that some of the light along the light paths to the detectors  531 A and B can be scattered into the next grating order (e.g., the grating order adjacent to the main grating order). 
     In some examples, the frequency stabilization subsystem may include other types of selectors and a common detector. For example, as shown in  FIG.  10 B , frequency stabilization subsystem  1008 B can include a first ring resonator  1010 B- 1  and a second ring resonator  1010 B- 2  having one or more functionalities and/or characteristics similar to the first ring resonator  610 A and the second ring resonator  610 B illustrated in  FIG.  6   . The ring resonators  1010 B can generate multiple outputs. A first output can be coupled (directly or indirectly) to the attenuator  1037 A, and a second output can be coupled to attenuator  1037 B. The attenuators  1037  can modulate the signals of the outputs from the ring resonators  1010 B at different frequencies. The output from one attenuator, such as attenuator  1037 A, can be coupled to one side of the waveguide of the detector  1031 , and the output from another attenuator, such as attenuator  1037 B, can be coupled to the other side of the waveguide of the detector  1031 . The detector  1031  can receive the attenuated signals and can generate a signal on the output  1049 . 
     As another example, as shown in  FIG.  10 C , frequency stabilization subsystem  1008 C can include a DBR component  1010 C having one or more functionalities and/or characteristics similar to the DBR component  710 A illustrated in  FIG.  7 A  or the DBR component  710 B illustrated in  FIG.  7 B . The DBR component  1010 C can include a splitter  1011  and multiple DBRs  1013 A and  1013 B. Similar to frequency stabilization subsystem  1008 A of  FIG.  10 A  and frequency stabilization subsystem  1008 B of  FIG.  10 B , frequency stabilization subsystem  1008 C can be connected to one or more attenuators  1037  and a detector  1031 . 
     As discussed herein, the illustrated block diagrams do not limit the configuration (e.g., location, size, orientation, etc.) of the optical routing lines and components. Examples of the embodiments described herein can include other types of configuration not illustrated explicitly in the figures. Additionally or alternatively, the detector can be any type of detector, such as one that is discrete from the other components included in the frequency stabilization subsystem, or the detector may be an integrated component that is inseparable from the other components. 
     Detector Including Twin Waveguides 
     In some examples, the drift in the detectors can be due to one or more material properties such as crystal defects. In some examples, the structure of the detectors may be changed to account for such defects.  FIG.  11    illustrates a cross-sectional view of an example detector including multiple waveguides formed on the same substrate. The detector  1130  can include a substrate  1119 , where multiple waveguides, such as waveguide  1115 A and waveguide  1115 B, can be formed on the same substrate  1119 . In some examples, the waveguide  1115 A and the waveguide  1115 B can be twin waveguides, which can be waveguides, spaced with a small separation distance. The separation distance can be such that the wave of distortion from the crystal defects can affect both waveguides. For example, the separation distance  1198  may be in the approximate range of 2-5 μm and can be less than the waveguide&#39;s longitudinal dimension (e.g., 10 μm). The separation distance  1198  can be the distance between inner walls of the waveguides  1115 A and  1115 B. 
     Multiple Light Sources 
     Examples of the disclosure can further include the optical sensing system configured with a plurality of light sources.  FIG.  12    illustrates a block diagram of an example optical sensing system including a frequency stabilization subsystem including an AWG and a detector. 
     The optical sensing system can include a device  1200 . The device  1200  can include a plurality of light sources  1202 , a frequency stabilization subsystem  1208 , and a controller  1212 . The plurality of light sources  1202  can be configured to emit light along light paths  1244 . In some examples, the plurality of light sources  1202  can be configured to emit light having different ranges of wavelengths. Examples of the disclosure can include the plurality of light sources  1202  formed on multiple epitaxial chips. 
     The frequency stabilization subsystem  1208  can include a selector, such as AWG  1210 , attenuators  1237 , and one or more detectors, such as detector  1231 . Although the figure illustrates an AWG  1210 , examples of the disclosure can include other selectors such as filters, resonators, multiplexers, MZIs, Fabry-Perot cavities, nanobeam cavities, ring resonators, DBRs, or the like. The selector (e.g., AWG  1210 ), attenuators  1237 , and detector(s)  1231  can include one or more functionalities and/or characteristics similar to those disclosed herein. For example, the selector can have multiple functions: (1) multiplex, combine, filter, and/or select from its input(s) (e.g., light along the light paths  1244 ), and (2) generate feedback information for controlling the light sources  1202  via, e.g., the controller  1212 . In some examples,  FIG.  12    may not include the AWG  1210  and also may not include the attenuators  1237 . Continuing this example,  FIG.  12    may include an MZI outputting light to two individual detectors  1231 . 
     The frequency stabilization subsystem  1208  can output signals directly from the detector  1231  as output  1249  to the controller  1212 . In some examples, one or more components, such as filters, amplifiers, analog-to-digital converters (ADCs), etc. (not shown in  FIG.  12   ) can receive signal(s) from the detector(s)  1231  and can output signal(s) to the controller  1212 . 
     The signal(s) from the frequency stabilization subsystem  1208  can be used as feedback in, e.g., a control loop. A controller  1212  can receive and analyze the signal(s) from the frequency stabilization subsystem  1208  and can generate one or more signals. The signal(s) from the frequency stabilization subsystem  1208  can be the same signals used to control the light sources  1202  and the properties of light emitted by the light sources  1202 . In some examples, the signal(s) from the frequency stabilization subsystem  1208  (e.g., output  1249 ) can be indicative of targeted changes in one or more properties (e.g., temperature, current, etc.) of the light sources  1202 . In some examples, the controller  1212  can include one or more other pieces of information (e.g., measured temperature of the light sources  1202 ) in generating the signal(s). 
     The frequency stabilization subsystem  1208  can also output light directed to the system interface for a measurement. In some examples, the selector can output the light to the system interface along the light path  1242 . 
     Calibration and Thermal Stabilization 
     The frequency stabilization subsystem can include one or more components for calibrating its temperature and can include one or more sensor components for detecting a change in its operation. The frequency stabilization subsystem can also include one or more heaters for controlling its temperature, which can affect its operation. 
       FIG.  13 A  illustrates a block diagram of an example ring resonator and calibration components. The ring resonator  1310 B can include a plurality of waveguides  1315 B. At least one waveguide, such as waveguides  1315 B- 2 , can be looped optical waveguides. One or more waveguides, such as waveguide  1315 B- 1 , can be an input waveguide, and one or more waveguides, such as waveguide  1315 B- 3  and waveguide  1315 B- 4 , can be output waveguides. Input waveguides can be waveguides connected to light input to the ring resonator  1310 B, and output waveguides can be waveguides connected to light output from the ring resonator  1310 B. In some instances, the input and output waveguides may include the same structure. A looped waveguide  1315 B- 2  can include a closed loop that is optically coupled to the input waveguide  1315 B- 1  and one of the output waveguides  1315 B- 3  or  1315 B- 4 . 
     The ring resonator  1310 B can include calibration components such as heaters  1323  and sensors  1325 . The sensors  1325  can be temperature sensors, for example, that measure the temperature of the ring resonator  1310 B. If the temperature of the ring resonator  1310 B deviates within a certain threshold(s) from the targeted temperature (e.g., does not meet a temperature criteria), a controller (not shown) can send one or more control signals to the heaters  1323  to change the temperature of the ring resonator  1310 B to within the targeted threshold(s). 
     The calibration components can be included in other types of components, such as a DBR, as shown in  FIG.  13 B . DBR  1313  can include calibration components such as heater  1323  and sensor  1325 . Similar to the calibration components discussed above, the sensor  1325  can measure the temperature of the DBR  1313 , and this temperature measurement can be used as feedback to the heater  1323  for controlling (e.g., adjustment) the temperature of the DBR  1313 . Although a single heater  1323  and a single sensor  1325  are illustrated in  FIG.  13 B , examples can include any number of heaters, any number of sensors, and any ratio of heaters to sensors. In some examples, the number of heaters and the number of sensors can depend on the size of the component. For example, larger passive components can have a greater number of calibration components than smaller passive components. 
     Examples of the disclosure can include executing the calibration procedure at periodic intervals, upon system startup, in synchronization with the measurements, when the light emitted by the light sources deviates from its targeted properties, and so forth. Although  FIGS.  13 A- 13 B  illustrate the calibration components as included in a ring resonator and DBR, respectively, examples of the disclosure can include calibration components as included in other types of passive components, such as those described herein. Additionally, examples can include the heaters and sensors having configurations (e.g., location, size, orientation, etc.) not explicitly shown in the figures. For example, heater  1323  in  FIG.  13 A  may be square or any other appropriate shape, instead of rectangular. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings. 
     The present disclosure recognizes that personal information data, including the biometric data acquired using the presently described technology, can be used to the benefit of users. For example, the use of biometric authentication data can be used for convenient access to device features without the use of passwords. In other examples, user biometric data is collected for providing users with feedback about their health or fitness levels. Further, other uses for personal information data, including biometric data that benefit the user are also contemplated by the present disclosure. 
     The present disclosure further contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure, including the use of data encryption and security methods that meets or exceeds industry or government standards. For example, personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection should occur only after receiving the informed consent of the users. Additionally, such entities would take any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. 
     Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data, including biometric data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, in the case of biometric authentication methods, the present technology can be configured to allow users to optionally bypass biometric authentication steps by providing secure information such as passwords, personal identification numbers (PINS), touch gestures, or other authentication methods, alone or in combination, known to those of skill in the art. In another example, users can select to remove, disable, or restrict access to certain health-related applications collecting users&#39; personal health or fitness data.

Metadata:
Filing Date: 20210712
Publication Date: 20231128
Grant Date: 20231128
Priority Date: 20180928
Inventors: BISMUTO, ALFREDO
WU, YI-KUEI RYAN
SCHRANS, THOMAS
TRITA, Andrea
ZILKIE, AARON
Assignee: APPLE INC
CPC Classifications: [{"code": "H05B47/105", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/0238", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4228", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29301", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29328", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29343", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29395", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/4215", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/2935", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/2938", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/29358", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/4215", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B47/105", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/29301", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/29343", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/29395", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/12009", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4257", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0425", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4228", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B47/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/4215", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29301", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29343", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29328", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/29358", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4228", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0238", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/2938", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/2935", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/29395", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 76764418