Multi-wavelength tunable laser

Abstract

The present disclosure relates to multi-wavelength tunable lasers. In some implementations, a laser system can include a gain chip, a tunable wavelength selection component, and a bandpass component. The gain chip, within a cavity of the laser system, can be configured to emit a light beam. The tunable wavelength selection component, within the cavity, can be configured to filter the light beam into a first plurality of tunable transmission channels separated by a free spectral range. The bandpass component, within the cavity, can be configured to define a spectral bandpass that enables a second plurality of tunable transmission channels to form a multi-channel light beam for output from the cavity, where the second plurality of tunable transmission channels can be a subset of the first plurality of tunable transmission channels that fall within the spectral bandpass.

Description

Cross-reference to related applications

[0001] This patent application claims priority to U.S. Patent Application No. 63 / 785,447, filed April 8, 2025, entitled “MULTI-WAVELENGTH TUNABLE LASER”. The disclosure of that earlier application is considered part of this patent application and is incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to optical lasers and multi-wavelength tunable lasers. Background Technology

[0003] An external cavity laser (ECL) is a laser system characterized by a resonant cavity design, in which a portion of the optical cavity is located outside the gain medium, which can be a semiconductor diode. In some ECL setups, light emitted from the laser diode exits through facets of the gain medium, passes through free space or other optical elements, and is then reflected back into the diode by an external mirror or wavelength-selective element. The external cavity of the ECL plays a crucial role in determining the laser's optical characteristics. By adjusting the position or angle of the external cavity, users can finely tune the laser wavelength across a wide spectral range. ECLs may also exhibit narrow linewidths, allowing the emitted light to be monochromatic and stable. The design flexibility of ECLs makes them highly useful in applications that utilize wavelength control and stability. In the telecommunications field, ECLs can be used as a light source for dense wavelength division multiplexing (DWDM) systems. In spectroscopy and sensing, ECLs can be used to selectively probe specific molecular transitions. Additionally, ECLs can be used in metrology, atomic physics, and / or as seed lasers for high-power amplifiers. ECL's combination of wide tunability, narrow linewidth, and stable operation distinguishes it from many other types of lasers, such as integrated cavity lasers. Summary of the Invention

[0004] In some embodiments, the apparatus may include: a gain chip, within a cavity of the apparatus, configured to emit a light beam; an adjustable wavelength selection component, within a cavity, configured to filter the light beam into a first plurality of adjustable transmission channels separated by a free spectral range; and a bandpass component, within a cavity, configured to define a spectral bandpass that enables a second plurality of adjustable transmission channels to form a multi-channel light beam output from the cavity, wherein the second plurality of adjustable transmission channels is a subset of the first plurality of adjustable transmission channels falling within the spectral bandpass.

[0005] In some embodiments, the laser system may include: a gain chip, within a cavity of the laser system, configured to emit a beam; a tunable wavelength selection component, within the cavity, configured to filter the beam into a first plurality of tunable transmission channels separated by a free spectral range; and a bandpass component, within the cavity, configured to define a spectral bandpass that enables a second plurality of tunable transmission channels to form a multi-channel beam for output from the cavity, wherein the second plurality of tunable transmission channels are a subset of the first plurality of tunable transmission channels falling within the spectral bandpass.

[0006] In some implementations, the ECL may include: a gain chip, within the cavity of the ECL, configured to emit a beam; an adjustable wavelength selection component, within the cavity, configured to filter the beam into a first plurality of adjustable transmission channels separated by a free spectral range; and a bandpass component, within the cavity, configured to define a spectral bandpass that enables a second plurality of adjustable transmission channels to form a multi-channel beam for output from the cavity, wherein the second plurality of adjustable transmission channels are a subset of the first plurality of adjustable transmission channels falling within the spectral bandpass. Attached Figure Description

[0007] Figure 1 A side view of the laser system is shown.

[0008] Figure 2 The frequency channel distribution diagram for a multi-channel tunable laser is shown. Detailed Implementation

[0009] The following detailed description of exemplary embodiments is provided with reference to the accompanying drawings. The same reference numerals in different drawings may identify the same or similar elements.

[0010] Tunable laser configurations for single-wavelength lasers, such as tunable telecommunications lasers known as external cavity lasers (ECLs), represent a significant advancement in laser design within the field of optical communications. Unlike integrated cavity lasers, where the laser resonator is a compact and tightly enclosing medium surrounding the gain chip, ECLs offer greater flexibility in configuration. For example, in an ECL, at least one end mirror of the cavity is located away from the gain chip, and additional optics can be placed between the gain chip and the distal end mirror. This configuration allows for greater flexibility and control relative to the laser output, making ECL configurations invaluable for a wide range of high-precision applications in optical communications.

[0011] Additionally, the ECL configuration has the capability to achieve single-wavelength operation with wide frequency tunability. This frequency tunability is achieved by using two optical comb filters (such as Fabry-Perot etalons) within the laser cavity of the ECL. At least one of these filters is tunable, for example, via thermal adjustment. These filters can be designed such that the correlation between the two filters is a difference in their free spectral range (FSR) (e.g., the spacing between the comb teeth). This difference in FSR ensures that within the laser gain wavelength window, the first and second filters have only one overlapping tooth. As a result, a wavelength falling within this narrow overlap window can resonate and amplify within the laser cavity, leading to laser generation at that overlapping wavelength.

[0012] The laser cavity of an ECL functions as a comb filter with narrow, high-density teeth. The structure of the ECL laser cavity is configured to ensure that one cavity mode aligns with the overlapping teeth of two filters. In some examples, a vernier effect allows for wider wavelength tuning. The vernier engagement mechanism enables a single overlapping wavelength to be tuned across a wider spectrum than the filter tuning range.

[0013] However, the single-wavelength output of ECLs has limitations in the context of optical communication requirements. The ongoing trend of driving optical data connections closer to the chip, coupled with the ever-increasing overall bandwidth demands, puts pressure on the bandwidth capacity of optical communication technologies. Therefore, the development of multi-wavelength light sources may enable optical technologies to keep up with the growing bandwidth requirements. However, improvements to ECLs across various parameters are expected, including operational efficiency, integration, compactness, wavelength control, wavelength selection, output power per wavelength, and cost-effectiveness. While single-wavelength ECLs are accurate and stable, they do not inherently support simultaneous multi-wavelength operation associated with dense wavelength division multiplexing (DWDM) systems and other advanced optical communication applications.

[0014] Some embodiments described herein provide multi-wavelength tunable lasers (e.g., multi-wavelength or multi-channel ECLs) capable of synchronous multi-wavelength operation. For example, a multi-wavelength ECL may include an internal comb filter paired with a bandpass filter, such that the selection of the comb filter... N Each adjacent tooth will fall within the passband of the bandpass filter (e.g., ...). N =8; N =16; or another value determined by design choices). Therefore, the laser cavity of a multi-wavelength ECL can simultaneously... N Resonance at various wavelengths, gaining gain and / or generating laser light (within the bandpass band) NThe cavity mode under each of the adjacent comb teeth. Additionally, multi-wavelength ECLs may include one or more semiconductor amplifiers (e.g., one or more semiconductor optical amplifiers (SOAs)). In some embodiments, the one or more semiconductor amplifiers may be "non-uniformly broadened" (e.g., broadening of spectral lines or energy levels in a semiconductor material due to variations in the local environment within the material). Therefore, in the case of non-uniform broadening, multiple wavelengths can be simultaneously amplified by the SOA without significant competition for the same gain medium resources. Thus, the techniques described herein enable multi-wavelength ECLs to... N Stable laser generation at each wavelength. In some embodiments, the cavity comb filter of the multi-wavelength ECL can be tunable to adjust the grid within the bandpass window, enabling stable generation of laser light at the entire wavelength. N Tuning is performed on blocks of wavelengths (e.g., wavelength shifting).

[0015] In some examples, a multi-wavelength ECL may include a gain chip (e.g., a conventional band (C-band), a long band (L-band), or a primitive band (O-band)), a monitoring photodiode (PD), a collimating lens, an optical mirror, a heating element, an integrated resistance temperature device (RTD), and an optical comb filter, an optical isolator, a fiber focusing lens, and / or a bandpass optical filter. These components are combined to generate multi-wavelength laser output from a single fiber. Additionally, the RTD can be used to monitor the temperature with a feedback control loop for controlling the temperature of the comb filter. Therefore, the multi-wavelength laser can be positioned to a desired frequency grid target within the bandpass filter range. Furthermore, such a multi-channel laser can be focused into a single output fiber to simultaneously distribute multiple wavelengths of laser light. Moreover, such a multi-wavelength laser can be simultaneously tuned to multiple wavelengths within the bandpass filter range. This can create an efficient way to communicate and transmit data in parallel between two communication entities, such as multiple data center systems. Therefore, the technique described herein enables the realization of a multi-wavelength tunable laser that utilizes the laser precision technology of a single-wavelength ECL while simultaneously enabling synchronous multi-wavelength communication operation.

[0016] Figure 1 A side view of laser system 100 is shown. In some examples, laser system 100 may be a multi-wavelength tunable laser (such as a multi-wavelength ECL). Figure 1As shown, the laser system 100 includes a controller 102, a gain chip 104, a laser cavity 106, a beam 108, lenses 110 (e.g., lenses 110a, 110b, 110c, and 110d), a tunable wavelength selection component 112, one or more temperature sensors (e.g., temperature sensor 116a and / or temperature sensor 116b), one or more heating components 114 (e.g., heating component 114a and / or heating component 114b), a bandpass component 118, a reflector 120, one or more beam splitter components 122 (e.g., beam splitter component 122a and / or beam splitter component 122b), one or more photodiodes 124 (e.g., photodiode 124a and / or photodiode 124b), one or more isolator components 126 (e.g., isolator component 126a and / or isolator component 126b), an optical amplifier 128, an output fiber 130, a carrier 132, a thermoelectric cooler (TEC) 134, and a thermistor 136. In some other embodiments, the laser system 100 may include, in addition to a reference... Figure 1 Additional and / or different parts besides the described parts, or some of these parts are missing.

[0017] Controller 102 may include memory. For example, the memory of controller 102 may include random access memory (RAM), read-only memory (ROM), hard disk drive, and / or another type of memory (e.g., flash memory, magnetic storage, and / or optical storage). Memory may include internal memory (e.g., RAM, ROM, or hard disk drive) and / or removable memory (e.g., removable via a universal serial bus connection). Memory may be a non-transitory computer-readable medium. Memory may store information related to the operation of laser system 100, one or more instructions, and / or software (e.g., one or more software applications). For example, memory may store one or more instructions (when executed by one or more processors of controller 102) enabling one or more operations of laser system 100 to be performed. In some aspects, memory may include one or more memories coupled to one or more processors (e.g., via a bus). Communication coupling between the processor and memory at controller 102 may enable the processor to read and / or process information stored in memory and / or store information in memory. The processor of controller 102 may include a central processing unit, graphics processing unit, microprocessor, microcontroller, digital signal processor, field-programmable gate array, application-specific integrated circuit, and / or another type of processing unit. A processor can be implemented in hardware, firmware, or a combination of hardware and software. In some aspects, a processor may include one or more processors capable of being programmed to perform one or more operations or processes described elsewhere herein.

[0018] like Figure 1 As shown, controller 102 can be coupled to one or more components of laser system 100, such as via one or more buses. The bus may include one or more components that enable wired and / or wireless communication among the components of laser system 100. One or more buses can... Figure 1 One or more components are coupled to controller 102, such as via operational coupling, communication coupling, electronic coupling, and / or electrical coupling. For example, one or more buses may include electrical connections (e.g., wires, traces, and / or leads) and / or wireless buses. Figure 1 As shown, controller 102 can be coupled to gain chip 104, heating element 114, temperature sensor 116, photodiode 124, optical amplifier 128, TEC 134, and / or thermistor 136. In other embodiments, controller 102 can be coupled to... Figure 1 Any component shown (e.g., via one or more buses).

[0019] Gain chip 104 can be a semiconductor device designed to provide optical gain in specific wavelength bands, such as C-band (1530-1565 nm), L-band (1565-1625 nm), and / or O-band (1260-1360 nm). Therefore, gain chip 104 can amplify optical signals in an optical fiber communication system, enhance signal strength, and extend transmission distance. TEC 134 can be operatively coupled to gain chip 104 to thermally stabilize the distance between the front and rear facets of gain chip 104 and / or provide a stable output from gain chip 104. TEC 134 can be operatively coupled to controller 102.

[0020] like Figure 1 As shown, in the laser system 100, a portion extending from the gain chip 104 to the reflector 120 forms a laser cavity 106. The laser cavity 106 is the optical path for optical amplification and feedback, enabling continuous laser oscillation. This cavity extends from one end of the gain chip 104 (e.g., Figure 1The leftmost side of the gain chip 104 extends to and returns to a reflector 120 (such as an end mirror or diffraction grating). The reflector 120, located outside and / or separate from the gain chip 104, acts as a reflective surface, returning a portion of the emitted light into the gain medium, providing optical feedback for sustaining the laser. Additionally, the gain chip 104 may include a reflective coating on its back side as a second mirror. The back facets of the reflector 120 and the gain chip 104 together form a mirror pair, defining the two ends of the laser cavity 106. This configuration ensures that light reflects back and forth between the two mirrors, passing through the gain medium multiple times to achieve amplification and coherent light emission. Therefore, the facets of the gain chip 104 and the reflector optically coupled to the gain chip 104 can define the laser cavity of the laser system 100. In some embodiments, the mirror coupled to the gain chip 104 (forming a mirror pair with the reflector 120) may be separate from the gain chip 104.

[0021] Additionally, the gain chip 104 within the laser cavity 106 can be configured to emit a light beam 108. The gain chip 104 can act as an active medium that amplifies light through a stimulated emission process. When current is injected into the gain chip 104 (e.g., via controller 102), the current excites electrons within the semiconductor material, allowing them to release photons upon returning to a lower energy state. This process may not produce light of a single fixed wavelength; instead, the gain chip 104 supports amplification of light over a frequency range (or bandwidth) determined by the physical properties of the semiconductor material and the structure of the gain chip 104. This frequency bandwidth defines the set of wavelengths from which the gain chip 104 can effectively generate and amplify light. In other words, the gain chip 104 is configured to emit a light beam 108 spanning a possible wavelength spectrum.

[0022] After beam 108 is generated by gain chip 104, beam 108 can appear as a diverging beam (e.g., due to the small emission area size on gain chip 104). To effectively guide beam 108 along a defined optical path and into an external cavity, lens 110a (e.g., a collimating lens) can be placed in front of the emission facet of gain chip 104. Lens 110a can collect the diffused light and refocus it so that it propagates parallel to each other, producing a collimated or quasi-collimated beam. Collimation can reduce optical losses, ensure effective interaction between beam 108 and external cavity components, and maintain the spatial coherence of beam 108 over the length of laser cavity 106. By shaping the light into a well-defined, parallel beam, lens 110a helps to establish a stable and efficient optical path between gain chip 104 and reflector 120. In some embodiments, lens 110d can also be a re-collimating lens (e.g., to improve the collimation of beam 108 that may be output from optical amplifier 128).

[0023] like Figure 1As shown, after collimation by lens 110a, the beam 108 enters the tunable wavelength selection component 112 (e.g., a comb filter). The tunable wavelength selection component 112 can be an example of an etalon filter. For example, an etalon filter is an optical device comprising two parallel, partially reflective surfaces that produce multiple internal reflections of the light passing through it. Internal reflections cause interference between the reflected light waves, resulting in transmission peaks at specific wavelengths where constructive interference occurs. The spacing between these peaks (e.g., FSR) is determined by the distance between the reflecting surfaces and the refractive index of the materials between them. Therefore, the tunable wavelength selection component 112 within the laser cavity 106 can be configured to filter the beam 108 into a first set of tunable transmission channels separated by the configured FSR.

[0024] In laser system 100, the tunable wavelength selection component 112 may have an FSR of 200 gigahertz (GHz), a thickness of approximately 200 micrometers (µm), and may comprise silicon. In other embodiments, the tunable wavelength selection component 112 may have different FSRs, different thicknesses, and / or be composed of different materials. In some other embodiments, the tunable wavelength selection component 112 may not be an etalon filter, but rather a different type of filter (e.g., a silicon photonic ring resonator filter or a distributed Bragg reflector (DBR) grating filter may also be used to provide the same or similar functionality as an etalon filter). For example, the tunable wavelength selection component 112 may be a silicon ring resonator, which may be configured to have the same FSR (e.g., 200 GHz) as the etalon filter described herein. Alternatively, the tunable wavelength selection component 112 may be a DBR grating filter, wherein the Bragg grating periodicity of the DBR grating filter matches the FSR of the etalon filter described herein. In an embodiment where the tunable wavelength selection component 112 is a DBR grating filter, the back side of the gain chip 104 may have an integrated reflector that can serve as the first reflector of the DBR mirror pair, and the DBR grating filter may include the second reflector of the DBR mirror pair.

[0025] In some embodiments, a temperature sensor 116a (e.g., an RTD) and / or a heating element 114a may be attached to the tunable wavelength selection element 112. The temperature sensor 116a and / or the heating element 114a may be configured to measure and control the temperature of the tunable wavelength selection element 112, and thus control one or more temperature-related optical characteristics of the tunable wavelength selection element 112 (such as the transmission peak of the tunable wavelength selection element 112). For example, the temperature sensor 116a measures the temperature of the tunable wavelength selection element 112, and the heating element 114a applies heat to the tunable wavelength selection element 112 to maintain its selected operating temperature. By regulating to a consistent temperature, the tunable wavelength selection element 112 can reliably separate and / or filter optical signals spaced according to the FSR (defined by the tunable wavelength selection element 112), ensuring stable and accurate performance in applications such as wavelength division multiplexing in optical communication systems. Changing the heat applied to the tunable wavelength selection element 112 alters the temperature, which affects both the refractive index of the tunable wavelength selection element 112 and the physical spacing between its reflective surfaces. Therefore, the resonant wavelength (or frequency) at the transmitted light of the tunable wavelength selection component 112 shifts accordingly. By increasing or decreasing the temperature, the transmission peak of the etalon filter shifts to a longer (e.g., redshift) or a shorter (e.g., blueshift) wavelength, respectively. This thermal tuning allows for precise control of the output wavelength or frequency of the first plurality of channels transmitted through the tunable wavelength selection component 112, enabling dynamic selection or adjustment of multi-channel beams.

[0026] In some examples, a thermistor 136 (e.g., on the optical carrier 132 and / or TEC 134) can be used to calibrate the temperature sensor 116a. For example, during calibration, the thermistor 136 can be placed in close thermal contact with the carrier 132 to measure the temperature of the carrier 132. Therefore, the TEC 134 can be configured to control the temperature of the carrier 132, allowing the temperature reading of the temperature sensor 116a to be compared and adjusted relative to the measurement from the thermistor 136, ensuring that the temperature sensor 116a provides an accurate temperature reading for the tunable wavelength selection element 112. After calibrating the temperature sensor 116a, a wavelengthmeter can be used to calibrate the relationship between the temperature of the tunable wavelength selection element 112 and the temperature of the temperature sensor 116a and the frequency output of the tunable wavelength selection element 112. For example, the tunable wavelength selection element 112 can be continuously operated at various known temperatures using the calibrated temperature sensor 116a, and the corresponding transmission peaks at those known temperatures can be recorded using the wavelengthmeter. By plotting the measured transmission peak wavelength against a known temperature, a relationship between temperature and the resonant frequency of the tunable wavelength selection component 112 can be established. Based on this temperature-frequency relationship, multiple frequencies associated with the outputs of multiple laser channels of the laser system 100 can be simultaneously tuned by controlling the temperature of the tunable wavelength selection component 112. In other words, the target operating frequency of the tunable wavelength selection component 112 can be moved within an adjustable range by changing the temperature of the tunable wavelength selection component 112 using the temperature sensor 116a and the heating element 114a. In some embodiments, the tunable wavelength selection component 112 and the gain chip 104 are located on the same carrier 132 and TEC 134.

[0027] In some embodiments, a thermistor 136, which may be attached to the carrier 132, may be configured to read the temperature of the carrier 132. Therefore, a controller 102, operationally coupled to the thermistor 136 and the TEC 134, may be configured to apply current to the TEC 134 based on the temperature of the carrier 132, wherein the TEC 134 can maintain the temperature of the carrier 132 within a temperature range based on this current. The TEC 134 may operate based on the Peltier effect, which, when current is applied, allows the TEC 134 to transfer heat from one side of the TEC 134 to the other. If the controller 102 receives a temperature reading from the thermistor 136 indicating that the carrier 132 has deviated outside the configured temperature range, the controller 102 adjusts the current supplied to the TEC 134 accordingly. If the carrier 132 becomes overheated (e.g., above the temperature range), the controller 102 increases the current in the direction that causes the TEC 134 to absorb heat from the carrier 132 and dissipate heat to a heat sink (not shown) or the surrounding environment, thereby effectively cooling the carrier 132. Conversely, if the carrier 132 becomes too cold (e.g., below its temperature range), the controller 102 can reverse or modulate the current, causing the TEC 134 to transfer heat towards the carrier 132, thereby raising the temperature of the carrier 132. This closed-loop feedback system allows for temperature regulation because the controller 102 can change the amplitude and direction of the current applied to the TEC 134. Therefore, the carrier 132 (which can support...) Figure 1 The multiple optical or electronic components shown are kept within the configured temperature range to reduce thermal drift and instability of the laser system 100.

[0028] A bandpass component 118 (e.g., an optical bandpass component 118) can be designed to select multiple laser channels for output at the laser system 100. For example, the bandpass component 118 can be configured with a passband that defines a range of wavelengths or frequencies that the tunable wavelength selection component 112 allows to pass through while blocking wavelengths or frequencies outside this range. Therefore, the passband of the bandpass component 118 can be configured such that multiple laser channels (output by the tunable wavelength selection component 112) fall within this passband. In some examples, the number of laser channels ( N ) can be any integer (e.g. N= 8, N =16, and other examples). By controlling the passband, the passband component 118 ensures the utilization of the target. NMultiple laser channels output, thereby enhancing the performance and efficiency of the laser system 100. Therefore, the bandpass component 118 within the laser cavity 106 can be configured to define a spectral passband that enables the formation of a second plurality of tunable transmission channels for a multi-channel beam output from the laser cavity 106. For example, the second plurality of tunable transmission channels may be a subset of the first plurality of tunable transmission channels falling within this spectral passband. Thus, the bandpass component 118 can be configured to allow the second plurality of tunable transmission channels to include a defined number of tunable transmission channels.

[0029] In some embodiments, the bandpass component 118 may comprise a block primarily composed of silicon, a material used in photonic applications due to its optical transparency in the near-infrared spectrum and compatibility with modern manufacturing techniques. Structurally, the silicon block is designed with a planar geometry to facilitate integration within the optical path of the laser cavity 106. One side of the silicon block (e.g., the front facing the gain chip 104 or the rear facing away from the gain chip 104) may be coated with a dedicated bandpass filter material. This filter material may comprise a multilayer stack of thin films engineered using alternating layers of dielectric materials with different refractive indices. These alternating layers may be deposited to produce constructive and destructive interference at specific wavelengths, thereby defining the spectral passband of the bandpass component 118. In some cases, the bandpass component 118 may be located on the opposite side of the gain chip 104 ( Figure 1 (This geometry is not depicted in the text) and also provides a reflector that forms a mirror pair with the reflector 120.

[0030] In some embodiments, a temperature sensor 116b (such as an RTD) and / or a heating element 114b may be physically attached to the bandpass component 118. These elements may be configured to monitor and regulate the temperature of the bandpass component 118. By actively controlling the temperature, the controller 102 can finely tune and stabilize one or more known temperature-dependent optical characteristics of the bandpass component 118. For example, the bandpass component 118 (which may be implemented as an interference filter, a thin-film filter, or a Bragg grating, etc.) may be designed to selectively transmit light within a specific wavelength range while attenuating light outside that range. One or more optical characteristics of the bandpass component 118 that may vary with temperature include the center wavelength (or peak transmission wavelength), bandwidth, and / or transmission profile or shape. The center wavelength of the optical bandpass component 118 may be temperature-sensitive based on thermo-optical effects (e.g., changes in the refractive index of a material with temperature) and / or the coefficient of thermal expansion (e.g., physical thickness or periodic variations of the filter layer or grating). For thin-film interference filters, increased temperature can cause changes in the refractive index of the dielectric material and may also alter the physical thickness of the layers, resulting in a shift in the center wavelength (e.g., a "wavelength drift"). Additionally or alternatively, the bandwidth (e.g., full width at half maximum (FWHM)) of the bandpass element 118 may widen or narrow with temperature variations because constructive and destructive interference conditions are altered. For Bragg gratings used as bandpass elements, thermal expansion and thermo-optical effects can change the grating period and effective refractive index, leading to a shift in the reflected or transmitted wavelength. By integrating the temperature sensor 116b and the heating element 114b with the bandpass element 118, the laser system 100 can employ active feedback control to stabilize the temperature of the bandpass element 118, thus increasing control over the center wavelength, bandwidth, and / or overall filter response. This ensures consistent and reliable optical performance even in the presence of ambient temperature fluctuations or thermal loads generated by other components of the laser system 100.

[0031] Therefore, by controlling the temperature of the bandpass component 118 using the temperature sensor 116b and the heating element 114b, the controller 102 can dynamically influence the number of laser channels (or different wavelengths) present in the beam 108 output from the laser cavity 106. As the temperature is adjusted, the center wavelength and bandwidth of the bandpass component 118 shift accordingly, making it possible to selectively align the transmission peak of the bandpass component 118 with the gain distribution of the laser medium.

[0032] Therefore, as described herein, heating elements 114a and 114b attached to the adjustable wavelength selection element 112 and the bandpass element 118 can be configured to apply heat to the adjustable wavelength selection element 112 and the bandpass element 118. Additionally, temperature sensors 116a and 116b attached to the adjustable wavelength selection element 112 and the bandpass element 118 can be configured to monitor the temperature of the adjustable wavelength selection element 112 and the bandpass element 118. Therefore, the controller 102, operationally coupled to the heating elements 114a and 114b and the temperature sensors 116a and 116b, can be configured to adjust multiple wavelengths corresponding to a second plurality of adjustable transmission channels based on adjusting the temperature output of the heating elements 114a and 114b. In some embodiments, the temperature sensors 116a and 116b can be the same temperature sensor or different / separate temperature sensors. In some embodiments, the heating elements 114a and 114b can be the same heating element or different / separate heating elements.

[0033] In some embodiments, the bandpass component 118 allows for fine adjustment of the length of the laser cavity 106 and the wavelength of the cavity mode. For example, a heating element 114b and a temperature sensor 116b attached to or in thermal contact with the bandpass component 118 can allow for precise temperature control of the silicon block and its bandpass filter surface. When heat is applied via the heating element 114b, the temperature of the silicon block rises, causing the bandpass component 118 to expand due to its coefficient of thermal expansion. This physical expansion results in a slight increase in the optical path length between the gain chip 104 and the reflector 120, thereby increasing the overall length of the laser cavity 106. Conversely, lowering the temperature using the heating element 114b (or by allowing the component to cool) causes the bandpass component 118 to contract, shortening the length of the laser cavity. Additionally or alternatively, the TEC 134 can be used to adjust the length of the laser cavity 106 by controlling the temperature of the carrier 132, on which the gain chip 104, and in some embodiments, the bandpass component 118 or the tunable wavelength selection element 112 may be mounted. By increasing the current supplied to TEC 134, carrier 132 can be heated, causing it to expand and thus increasing the distance between the components at both ends of the laser cavity, effectively lengthening the optical path. Conversely, reversing or reducing the current flowing to TEC 134 allows the carrier to cool and contract, thereby shortening the length of laser cavity 106. These thermal tuning mechanisms, whether applied locally via heating component 114b or globally via TEC 134, provide precise dynamic control relative to the physical length of laser cavity 106, enabling robust wavelength stability and flexible tuning required for high-performance multi-wavelength laser systems.

[0034] Beam splitter component 122a can be used to split beam 108 into two independent paths. In other words, beam splitter component 122a can be configured to reflect a portion of the multi-channel beam (e.g., to photodiode 124a). For example, the first path of beam 108 may continue to the intended application, while the second path is directed to photodiode 124a. Photodiode 124a can be used to monitor output power with closed-loop feedback to control output power and gain medium current. For example, the gain medium current directly affects the amplification of light within laser cavity 106, and photodiode 124a periodically monitors the laser output power. The feedback control loop uses measurements from photodiode 124a to adjust the gain medium current in real time, ensuring that the output power of laser system 100 remains stable and at the configured level. Therefore, photodiode 124a is configured to receive a portion of beam 108 and generate a current value proportional to the output power of beam 108, which controller 102 can receive or acquire from photodiode 124a. Additionally, as Figure 1 As shown, controller 102 is operatively coupled to one or more of photodiode 124a and gain chip 104, and can be configured to adjust a first current applied to gain chip 104 based on a current value measured by photodiode 124a, wherein the first current controls the output power or intensity of beam 108. Although Figure 1 The photodiode 124a and beam splitter component 122a are shown outside the laser cavity 106 (e.g., after the reflector 120), but in other embodiments, the photodiode 124a and beam splitter component 122a may be located inside or within the laser cavity 106. For example, the photodiode 124a and beam splitter component 122a may be located between the lens 110a and the tunable wavelength selection component 112, between the tunable wavelength selection component 112 and the bandpass component 118, or between the bandpass component 118 and the reflector 120.

[0035] In some embodiments, beam splitter component 122b can be used to split beam 108 into two independent paths after the beam has passed through optical amplifier 128. In other words, beam splitter component 122b can be configured to reflect portions of the multi-channel beam (e.g., to photodiode 124b). For example, the first path of beam 108 can continue to the intended application, while the second path is directed to photodiode 124b. Photodiode 124a can be used to monitor output power with closed-loop feedback to control the current and output power of optical amplifier 128. For example, the current applied to optical amplifier 128 can directly affect the amplification of beam 108 after optical amplifier 128, and photodiode 124b can periodically monitor the output power of beam 108 that may be amplified by optical amplifier 128. The feedback control loop uses measurements from photodiode 124b to adjust the current applied to optical amplifier 128 in real time, ensuring that the output power of laser system 100 remains stable and within the configured level. Therefore, photodiode 124b is configured to receive a portion of the light beam 108 after the optical amplifier 128 and generate a current value proportional to the output power of the light beam 108, which the controller 102 can receive or acquire from photodiode 124b. Additionally, as Figure 1 As shown, controller 102 is operatively coupled to photodiode 124b and optical amplifier 128, and can be configured to adjust a second current applied to optical amplifier 128 based on a current value measured by photodiode 124b, which controls the output power or intensity of beam 108. Although Figure 1 The illustrated photodiode 124b and beam splitter component 122b are located directly after the optical amplifier 128. However, in other embodiments, the photodiode 124b and beam splitter component 122b can be located anywhere after the optical amplifier 128 and before the lens 110b (e.g., between the optical amplifier 128 and the isolator component 126b, or between the isolator component 126b and the lens 110b). In some embodiments, the photodiode 124b and beam splitter component 122b may be optional for the laser system 100.

[0036] Outside the laser cavity 106, isolator component 126a can be configured to prevent back-reflection propagation back into the laser cavity 106 and / or other sensitive components of the laser system 100. By allowing the beam 108 to pass unidirectionally, isolator component 126a protects the laser system 100 from potential interference or instability caused by reflected light, ensuring stable and efficient operation. In the context of an external cavity laser, such isolator component 126 may be advantageous because the external cavity laser is sensitive to feedback, which can reduce spectral purity, destabilize the emission wavelength, and / or induce mode jumps. Isolator component 126 can be implemented using various optical isolator techniques. For example, isolator component 126 may include a Faraday isolator, which uses the magneto-optical Faraday effect to rotate the polarization of light in the presence of a magnetic field. Additionally or alternatively, isolator component 126 can be constructed using polarizers and waveplates (such as a combination of a polarizing beam splitter and a quarter-wave plate) to achieve unidirectional transmission of the beam 108. Therefore, isolator component 126a can be configured to prevent light from being reflected back into the laser cavity 106 of the laser system 100.

[0037] Lens 110b can be a fiber optic focusing lens. For example, a fiber optic focusing lens can focus a multi-wavelength laser beam from laser system 100 onto the core of a single optical fiber. Therefore, the beam 108... N Each of the laser channel outputs is focused into a single optical fiber (e.g., output fiber 130) for output from the laser system 100. By accurately aligning and converging the beam 108, lens 110b enables efficient coupling of the laser output to the output fiber 130, reducing losses and increasing the transmission of the optical signal through the output fiber 130.

[0038] In some embodiments of the laser system 100, an optical amplifier 128 (such as an SOA) and a second isolator component (e.g., isolator component 126b) may be located in the optical path between isolator component 126a and lens 110b. The sequence of isolator component 126a, followed by optical amplifier 128, then isolator component 126b, and subsequently lens 110b can increase the stability and output performance of the laser system 100. For example, isolator component 126a protects gain chip 104 and other sensitive upstream components within laser cavity 106 from back reflections that could destabilize or interrupt laser operation. The optical amplifier 128, located downstream of isolator component 126a, can be configured to increase the output power of multi-channel beam 108, compensate for losses in the optical path, and lock a strong signal to output fiber 130. The optical amplifier 128 (such as an SOA) directly amplifies the optical signal using stimulated emission within a semiconductor medium and can simultaneously enhance multiple wavelength channels, making it well-suited for wavelength division multiplexing (WDM) systems. In some implementations, lens 110c may also be a focusing lens (e.g., focusing beam 108 onto the input of optical amplifier 128).

[0039] Including an isolator component 126b downstream of the optical amplifier 128 may be advantageous, as the optical amplifier 128 may also be sensitive to optical feedback. Any back-reflected light re-entering the optical amplifier 128 (such as from lens 110b, connector interface, or output fiber 130) can cause undesirable effects such as gain fluctuations, noise, or parasitic lasing. This can degrade the performance of the optical amplifier 128, thereby affecting the entire laser system 100. By positioning the isolator component 126b downstream of the optical amplifier 128, the laser system 100 effectively prevents these back-reflections from reaching the optical amplifier 128 and upstream components and destabilizing them. This arrangement ensures that amplified light is efficiently and stably transmitted to the output fiber 130 via lens 110b, while maintaining the integrity and reliability of the laser system 100.

[0040] Laser system 100 may differ from other laser systems, such as comb lasers. For example, a comb laser is a mode-locked laser that utilizes the physical relationship that a continuous coherent optical pulse stream is equivalent to a continuous-wave (CW) optical wavelength grid (e.g., each filter in a comb laser stores the incident pulse and emits CW light of a specific wavelength). However, comb lasers have certain fundamental characteristics that may make them less efficient than the technology employed by laser system 100. For example, laser system 100 may be more energy-efficient than a comb laser because it generates multiple wavelengths that are subsequently filtered out, resulting in power waste. Conversely, laser system 100's... NEach of the laser channel outputs can be utilized, increasing the energy efficiency of the laser system 100 relative to a comb laser. Furthermore, compared to the laser system 100, a comb laser may exhibit poorer uniformity across the desired wavelength, which can be problematic when all channels require consistent power output. Therefore, the laser system 100 is likely more energy-efficient than a comb laser, and this, coupled with more uniform laser output, is beneficial in multi-wavelength optical communication.

[0041] As indicated above, Figure 1 This is provided as an example. Other examples may differ from those provided. Figure 1 The content shown and described.

[0042] Figure 2 A frequency channel distribution diagram 200 for a multichannel tunable laser is shown. In some examples, this frequency channel distribution diagram can be an example frequency channel distribution diagram of laser system 100. Figure 200 illustrates the relative output intensity of laser system 100 over a frequency range. The channel grid of a WDM laser is typically defined by the laser frequency, but is often represented as a "wavelength" channel. Optical frequency corresponds to optical wavelength via the fundamental relationship: λ (optical wavelength) • f (optical frequency) = c (speed of light in vacuum).

[0043] like Figure 2 As shown, the laser system 100 outputs a laser beam 108 comprising multiple laser frequency transmission channels 202 to an output fiber 130 (e.g., after passing through a tunable wavelength selection element 112 and a bandpass element 118). As described herein, after the laser beam 108 passes through the tunable wavelength selection element 112, the laser beam 108 may include a first plurality of transmission channels 202 (e.g., tunable transmission channels). For example, after passing through the tunable wavelength selection element 112, the laser beam 108 may include a first plurality of transmission channels 202, each corresponding to a narrowband wavelength or frequency. The frequency or wavelength spacing between these transmission channels 202 may be determined by the FSR 204 of the tunable wavelength selection element 112. The FSR 204 may be defined as the spacing between consecutive transmission channels 202 and may be based on the physical thickness and refractive index of the tunable wavelength selection element 112. Specifically, the FSR 204 is the frequency gap corresponding to an increase of 2π in the phase difference between consecutive reflections in the tunable wavelength selection element 112, resulting in constructive interference at discrete gaps. For example, in Figure 2In this configuration, the tunable wavelength selection component 112 has an FSR 204 that separates each transmission channel 202 from the next by a free spectral range 204. In optical terms, a "transmission channel" refers to a unique narrow band (or wavelength band) within a wider optical spectrum that can be used to carry separate data streams in a WDM communication system or to define a single laser mode. Therefore, the tunable wavelength selection component 112 enables the generation of a multi-channel beam, with each transmission channel 202 spaced apart according to the FSR 204. Thus, the FSR 204 defines a fixed channel spacing between the transmission channels 202.

[0044] Additionally, the first plurality of transmission channels 202 (exiting the tunable wavelength selection component 112) may propagate to the bandpass component 118, which can block the first plurality of transmission channels 202 that do not fall within the passband of the bandpass component 118. For example, in Figure 2 In this configuration, the passband of the passband component 118 may allow a subset of the transmission channels 202 within the passband. For example, in one example, the passband may span from 194 terahertz (THz) to 195.4 terahertz. However, in other examples, the passband may span any continuous frequency range covered by the C-band, L-band, and / or O-band.

[0045] like Figure 2 As shown, the passband allows eight consecutive transmission channels 202 to pass through the bandpass component 118 (e.g., transmission channels 202a, 202b, 202c, 202d, 202e, 202f, 202g, and 202h), which are uniformly spaced in the frequency domain. That is, the distance between transmission channels 202a and 202b is equal to the distance between transmission channels 202b and 202c (e.g., defined by FSR 204). Therefore, the bandpass component 118 allows a second plurality of transmission channels 202 to propagate, which may be a subset of the first plurality of transmission channels 202. Although Figure 2 The illustration shows eight transmission channels 202, but in other embodiments, the bandpass component 118 can be configured to allow a limited number of... N 202 transmission channels (e.g., 8, 16, or any other number).

[0046] As described herein, the adjustable wavelength selection component 112 can be configured to simultaneously shift the frequencies of the second plurality of transmission channels 202. For example, by raising or lowering the temperature of the adjustable wavelength selection component 112 (e.g., via heating component 114a), the controller 102 can synchronously increase or decrease the second plurality of transmission channels 202 by the same amount of frequency shift. For example, as Figure 2As shown, transmission channel 202a is centered at a first frequency, and transmission channel 202b is centered at a second frequency. Therefore, controller 102 can apply heat to the adjustable wavelength selection component 112 to shift the first transmission channel 202a from the first frequency to any frequency of the second frequency (e.g., shifting each of the transmission channels 202 by the same frequency shift amount). In other words, controller 102 can be operable to simultaneously shift a second plurality of wavelengths across a spectral range.

[0047] This simultaneous frequency shifting capability of the laser system 100 allows each of the transmission channels 202 generated by the tunable wavelength selection component 112 to be collectively tuned (or switched) across the entire span of the FSR 204. In other words, by adjusting the temperature of the tunable wavelength selection component 112, the controller 102 can move all the transmission channels 202 together, maintaining the relative spacing defined by the FSR 204, and positioning the transmission channels 202 anywhere within the available frequency window defined by the passband of the bandpass component 118. As a result, a second plurality of transmission channels 202 can be uniformly distributed across any desired portion of the passband, providing flexible spectral alignment. This can be advantageous for applications such as WDM, allowing the frequencies of the transmission channels 202 to be matched to the output channels of one or more predefined frequency grids, or for dynamic reconfiguration of multichannel systems. Therefore, the laser system 100 enables the generation of multiple equally spaced transmission channels 202 and allows this set of transmission channels 202 to be positioned at any location within a wider spectral region defined by the bandpass component 118, thereby increasing operational versatility and compatibility with various optical networks.

[0048] As indicated above, Figure 2 This is provided as an example. Other examples may differ from those provided. Figure 2 The content shown and described.

[0049] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Modifications and variations can be obtained from the foregoing disclosure or from practice of the embodiments. Furthermore, unless the foregoing disclosure expressly provides a reason why one or more embodiments cannot be combined, any embodiments described herein can be combined.

[0050] As used herein, the term "component" is intended to be interpreted broadly as hardware, firmware, and / or a combination of hardware and software. Clearly, the systems and / or methods described herein can be implemented in various forms of hardware, firmware, or combinations of hardware and software. The actual dedicated control hardware or software code used to implement these systems and / or methods does not limit the implementation. Therefore, the operation and behavior of the systems and / or methods described herein are not based on any specific software code—it should be understood that software and hardware can be designed to implement these systems and / or methods based on the descriptions herein.

[0051] As used in this article, "meeting the threshold" may refer to a value greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, or not equal to the threshold, depending on the context.

[0052] Even if specific combinations of features are disclosed in the claims and / or description, these combinations are not intended to limit the disclosure of various embodiments. In fact, many of these features can be combined in ways not specifically listed in the claims and / or description. Although each dependent claim listed below may depend directly on only one claim, the disclosure of various embodiments includes combinations of each dependent claim with every other claim in the claim set. As used herein, the phrase “at least one” in the list of descriptive items refers to any combination of these items, including a single member. For example, “at least one of: a, b, or c” is intended to cover a, b, c, ab, ac, bc, and abc, as well as any combination including multiple identical items.

[0053] This language is intended to broadly encompass a wide range of architectures and contexts when describing or claiming (within a single claim or across multiple claims) a component or one or more components (e.g., a laser emitter or one or more laser emitters) performing or being configured to perform multiple operations. For example, unless explicitly required otherwise (e.g., by using “first component” and “second component” or other language distinguishing components in the claims), this language is intended to cover a single component performing or configured to perform all operations, a group of components jointly performing or configured to perform all operations, a first component performing or configured to perform a first operation and a second component performing or configured to perform a second operation, or any combination of components performing or configured to perform these operations. For example, when a claim has the form “one or more components are configured to: perform X; perform Y; and perform Z,” the claim should be interpreted as “one or more components are configured to perform X; one or more (possibly different) components are configured to perform Y; and one or more (possibly different) components are configured to perform Z.”

[0054] Unless explicitly described as critical or necessary, no element, action, or instruction used herein should be construed as critical or necessary. Furthermore, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more.” Additionally, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more.” Furthermore, as used herein, the term “group” is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items) and may be used interchangeably with “one or more.” When referring to only one item, “only one” or similar language is used. Similarly, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Furthermore, the phrase “based on” is intended to mean “at least partially based on” unless otherwise explicitly stated. Similarly, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and / or” unless otherwise explicitly stated (e.g., if used in conjunction with “either” or “only one of”). Furthermore, spatially relative terms such as “below,” “lower,” “above,” “upper,” etc., may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s), as illustrated in the figures. Spatially relative terms are intended to cover different orientations of devices, equipment, and / or elements in use or operation other than those depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

Claims

1. An apparatus comprising: A gain chip, located within the cavity of the device, is configured to emit a beam of light; An adjustable wavelength selection component, within the cavity, is configured to filter the light beam into a first plurality of adjustable transmission channels separated by a free spectral range; as well as A bandpass component, within the cavity, is configured to define a spectral bandpass that enables a second plurality of tunable transmission channels to form a multi-channel beam output from the cavity, wherein the second plurality of tunable transmission channels is a subset of the first plurality of tunable transmission channels falling within the spectral bandpass.

2. The apparatus according to claim 1, further comprising: A heating element, attached to the tunable wavelength selection element and the bandpass element, is configured to apply heat to the tunable wavelength selection element and the bandpass element; A temperature sensor, attached to the tunable wavelength selection component and the bandpass component, is configured to monitor the temperature of the tunable wavelength selection component and the bandpass component; as well as A controller, operably coupled to the heating element and the temperature sensor, is configured to adjust multiple wavelengths corresponding to the second plurality of adjustable transmission channels based on adjusting the temperature output of the heating element.

3. The apparatus of claim 2, wherein the controller is operable to simultaneously shift the second plurality of wavelengths across the spectrum.

4. The apparatus of claim 1, wherein the free spectral range defines a fixed channel interval between the second plurality of adjustable transmission channels.

5. The apparatus of claim 1, wherein the adjustable wavelength selection component comprises an etalon filter.

6. The apparatus of claim 1, wherein the facets of the gain chip and a reflector optically coupled to the gain chip define the cavity of the apparatus.

7. The apparatus of claim 1, wherein the bandpass component is configured to allow the second plurality of adjustable transmission channels to include a defined number of adjustable transmission channels.

8. The apparatus of claim 1, further comprising a first isolator component, a lens, and an optical fiber output, wherein: The first isolator component is configured to prevent optical back reflections into the cavity of the device; The lens is configured to focus the multi-channel beam into the fiber optic output.

9. The apparatus of claim 8, further comprising an optical amplifier and a second isolator component located between the first isolator component and the lens, wherein the optical amplifier is configured to increase the output power of the multi-channel beam.

10. The apparatus according to claim 1, further comprising: The beam splitter component, either inside or outside the cavity, is configured to reflect the multi-channel beam. A photodiode, inside or outside the cavity, is configured to receive the portion of the multi-channel beam and generate a photodiode current value proportional to the output power of the multi-channel beam. as well as A controller, operably coupled to one or more of the photodiode and the gain chip or optical amplifier, is configured to adjust one or more of a first current applied to the gain chip or a second current applied to the optical amplifier based on the current value of the photodiode, wherein the first current or the second current controls the output power of the multi-channel beam.

11. The apparatus according to claim 1, further comprising: carrier; as well as A thermoelectric cooler (TEC) is attached to the carrier, wherein the gain chip and the adjustable wavelength selection component are attached to the TEC.

12. The apparatus of claim 11, further comprising: A thermistor is attached to the carrier and configured to indicate the temperature of the carrier; as well as A controller, operably coupled to the thermistor and the TEC, is configured to apply a current to the TEC based on the temperature of the carrier, wherein the TEC maintains the temperature of the carrier within a temperature range based on the current.

13. A laser system, comprising: A gain chip, within the cavity of the laser system, is configured to emit a beam; An adjustable wavelength selection component, within the cavity, is configured to filter the light beam into a first plurality of adjustable transmission channels separated by a free spectral range; as well as A bandpass component, within the cavity, is configured to define a spectral bandpass that enables a second plurality of tunable transmission channels to form a multi-channel beam output from the cavity, wherein the second plurality of tunable transmission channels is a subset of the first plurality of tunable transmission channels falling within the spectral bandpass.

14. The laser system according to claim 13, further comprising: A heating element, attached to the tunable wavelength selection element and the bandpass element, is configured to apply heat to the tunable wavelength selection element and the bandpass element; A temperature sensor, attached to the tunable wavelength selection component and the bandpass component, is configured to monitor the temperature of the tunable wavelength selection component and the bandpass component; as well as A controller, operably coupled to the heating element and the temperature sensor, is configured to adjust multiple wavelengths corresponding to the second plurality of adjustable transmission channels based on adjusting the temperature output of the heating element.

15. The laser system of claim 14, wherein the controller is operable to simultaneously shift the second plurality of wavelengths across the spectrum.

16. The laser system of claim 13, wherein the free spectral range defines a fixed channel spacing between the second plurality of tunable transmission channels.

17. The laser system of claim 13, wherein the tunable wavelength selection component includes an etalon filter.

18. The laser system of claim 13, wherein the facets of the gain chip and a reflector optically coupled to the gain chip define the cavity of the laser system.

19. The laser system of claim 13, wherein the bandpass component is configured to allow the second plurality of adjustable transmission channels to include a defined number of adjustable transmission channels.

20. An external cavity laser, comprising: The gain chip, located within the cavity of the external cavity laser, is configured to emit a beam. An adjustable wavelength selection component, within the cavity, is configured to filter the light beam into a first plurality of adjustable transmission channels separated by a free spectral range; as well as A bandpass component, within the cavity, is configured to define a spectral bandpass that enables a second plurality of tunable transmission channels to form a multi-channel beam output from the cavity, wherein the second plurality of tunable transmission channels is a subset of the first plurality of tunable transmission channels falling within the spectral bandpass.

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