Erbium doped fiber optical amplifier with adaptive filter

Abstract

To provide an erbium doped fiber optical amplifier with an adaptive filter.SOLUTION: According to an aspect of a certain embodiment, an optical signal and an optical pump signal may be acquired and multiplexed onto an erbium doped optical fiber. An optical fiber may be configured to perform amplification of an optical waveform within a first wavelength range. A signal in the first wavelength range of the optical signal may be amplified using the optical fiber. In some embodiments, a bend radius of a bend in a fiber-based filter may be adjusted such that the filter is configured to attenuate a signal within a second wavelength range. The filter is configured to attenuate the optical waveform for a wavelength range that varies depending on the bend radius of the bend in the filter. The second wavelength range may include wavelengths longer than the first wavelength range. The signal in the second wavelength range may be attenuated using the filter bent at the bend radius.SELECTED DRAWING: Figure 1D

Description

[Technical Field]

[0001] The embodiments discussed in this disclosure relate to erbium doped fiber optical amplifiers (EDFAs). [Background technology]

[0002] Telecommunications systems, cable television systems, and data communication networks use optical networks to convey information between remote points. In optical networks, information is conveyed in the form of optical signals through optical fibers or other optical media. Optical networks can include various components, such as amplifiers, dispersion compensators, multiplexer / demultiplexer filters, wavelength selective switches, and couplers, configured to perform various operations within the optical network. Additionally, optical amplification can be used to amplify optical signals propagating through an optical network.

[0003] The subject matter claimed herein is not limited to embodiments that solve any drawbacks or that operate only in environments such as those described above. Rather, this background is provided only to illustrate one example technology area where some embodiments described herein may be practiced. Summary of the Invention [Means for solving the problem]

[0004] According to certain aspects of certain embodiments, an optical signal and an optical pump signal may be acquired and multiplexed onto an erbium-doped optical fiber. The optical fiber may be configured to perform amplification of an optical waveform within a first wavelength range. The signal within the first wavelength range of the optical signal may be amplified using the optical fiber. In some embodiments, a bend radius of a bend in a fiber-based filter may be adjusted such that the filter is configured to attenuate signals within a second wavelength range, and the filter is configured to attenuate the optical waveform for a wavelength range that varies depending on the bend radius of the bend in the filter. The second wavelength range may include wavelengths longer than the first wavelength range. The signal within the second wavelength range may be attenuated using a filter bent at a bend radius.

[0005] The object and advantages of the embodiments will be realized and attained at least by the elements, features, and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. [Brief explanation of the drawings]

[0006] Example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings.

[0007] [Figure 1A] 1 illustrates an exemplary embodiment of an erbium-doped fiber optical amplifier (EDFA) in accordance with one or more embodiments of the present disclosure.

[0008] [Figure 1B] 1 shows an exemplary refractive index profile.

[0009] [Figure 1C] 1 illustrates an exemplary W-shaped refractive index profile according to one or more embodiments of the present disclosure.

[0010] [Figure 1D] 1 illustrates an exemplary loss profile according to one or more embodiments of the present disclosure.

[0011] [Figure 1E] 10 illustrates another exemplary loss profile according to one or more embodiments of the present disclosure.

[0012] [Figure 2] 2A-2B show exemplary bending structures according to one or more embodiments of the present disclosure.

[0013] [Figure 3] 1 is a flowchart of an exemplary method for amplifying an optical signal in accordance with one or more embodiments of the present disclosure.

[0014] [Figure 4] FIG. 1 illustrates a block diagram of an exemplary computing system that may be used with an EDFA, in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] An optical network may include nodes that may be configured to communicate information with each other via optical signals carried by optical fibers. In some situations, amplification of the optical signals in the optical fibers may allow the optical signals to travel longer distances by compensating for losses that may affect the optical signals, such as degradation of the optical signals due to noisy channels in the optical network.

[0016] Amplification of optical signals in optical networks may be achieved using erbium-doped fiber amplifiers (EDFAs) in some instances. However, the gain profile of EDF amplification may depend on certain wavelength bands. Thus, EDFAs may amplify signals in certain wavelength bands more efficiently than signals in other wavelength bands. For example, EDFAs are more commonly used to amplify signals in the normal band (C-band) ranging from approximately 1530 nanometers (nm) to 1565 nm and the long-wavelength band (L-band) ranging from approximately 1565 nm to 1600 nm. These EDFA characteristics have led to the increased use of C-band and L-band in optical communications. As optical communications using C-band and L-band become more widespread, there is an increasing need to utilize other optical communications bands, such as the short-wavelength band (S-band) ranging from approximately 1495 nm to 1530 nm.

[0017] However, amplifying the S-band signal may be limited by how effectively the noise present in the C-band and L-band can be attenuated while optimizing the gain applied to the S-band. For example, a low-pass filter can be used to attenuate the noise signals in the C-band and L-band while passing the S-band optical signal. However, such filters have fixed characteristics in that the cutoff wavelength cannot be modified once it is fixed to an initially assigned value.

[0018] According to one or more embodiments of the present disclosure, an EDFA can be configured to allow adaptive modification of an attenuation wavelength range in which signals and noise are attenuated. In particular, as described in detail herein, an EDFA can be configured to include a fiber-based filter in which the loss profile of the filter can be adjusted based on various applications. In particular, the filter can be bent to have a bend with a certain bend radius, and the bend radius can be tuned to modify the attenuation wavelength range. Such modification can allow for reduced noise amplification at wavelengths that do not correspond to the optical signal being transmitted.

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0020] 1A illustrates an exemplary embodiment of an EDFA 100 in accordance with at least one embodiment of the present disclosure. In general, the EDFA 100 may be configured to amplify an optical signal 102 to generate an amplified optical signal 112. The EDFA 100 may be included in any suitable optical device or network.

[0021] The optical signal 102 may include any optical signal configured to carry data. For example, the optical signal 102 may include an optical signal generated by a light emitting diode (LED), a laser, such as a laser diode, having data modulated thereon, and / or other similar optical signals. In some embodiments, the optical signal 102 may be generated by a transmission source, such as an optical transmitter, configured to communicate data and / or information through an optical network.

[0022] In some embodiments, optical signal 102 may carry data within a wavelength range corresponding to an optical signal communication band. For example, optical signal 102 may carry data within a first wavelength range corresponding to what may commonly be referred to as the S-band of optical signal communication, which may be approximately 1495 nm to 1530 nm. In these and other embodiments, EDFA 100, and in particular erbium-doped optical fiber ("optical fiber") 108, may be configured to amplify signals in the first wavelength range.

[0023] In some embodiments, the optical pump 104 may be optically coupled to the optical coupler 106. In these and other embodiments, the optical pump 104 may be configured to generate an optical pump signal and provide the optical pump signal to the optical coupler 106. In some embodiments, any type of optical pump may be used. For example, the optical pump 104 may be a laser diode, an arc lamp, a flash lamp, etc. The optical pump signal may include a wavelength different from the wavelength of the optical input signal 102. In these and other embodiments, the optical pump signal may not include any wavelength used by the optical input signal 102. In some embodiments, the wavelength of the optical pump signal may be selected based on the optical fiber 108, such as the length, material, etc. of the optical fiber 108, among other characteristics of the optical fiber 108. By way of example, the optical pump signal may have a wavelength of 810 nm, 980 nm, 1480 nm, etc.

[0024] In some embodiments, the optical pump signal may be determined based on the gain shape of the EDFA 100. For example, the gain shape or gain spectrum of the optical fiber 108 may be modified based on the optical pump signal. In these and other embodiments, the optical pump 104 may determine the optical pump signal such that the gain spectrum of the optical fiber 108 is suitable for the optical signal 102 and the optical fiber 108.

[0025] In some embodiments, the optical coupler 106 may be optically coupled to the optical pump 104 and the optical fiber 108. In these and other embodiments, the optical coupler 106 may be configured to take multiple signals and multiplex them onto the optical fiber 108. For example, the optical coupler 106 may be configured to take the optical signal 102 and the optical pump signal and multiplex and / or combine the optical signal 102 and the optical pump signal onto the optical fiber 108. As an example, the optical coupler 106 may be a wavelength division multiplexer (WDM). Alternatively or additionally, the optical coupler 106 may include one or more optical components, fused optical fibers, or waveguides to multiplex the optical signal 102 and the optical pump signal.

[0026] In some embodiments, the EDFA 100 may be configured to provide gain to the optical signal 102 such that the power of the optical signal 102 may increase as the optical signal 102 passes through the EDFA 100. For example, the optical fiber 108 may be configured to amplify the optical signal 102 using an optical pump signal. For example, interaction between ions in the optical fiber 108 and the optical pump signal may cause the release of energy within the optical fiber 108 that may be used to amplify the optical signal 102.

[0027] In some circumstances, the amplification of the optical signal 102 may vary based on the wavelength of the optical signal 102. For example, signals of different wavelengths may experience different levels of amplification within the optical fiber 108. In some examples, such varying amplification may be caused by a gain profile of the optical fiber 108, in which the optical fiber 108 applies different amounts of amplification to signals of different wavelengths. In some embodiments, the optical fiber 108 may be manufactured and / or tuned such that the optical fiber 108 applies maximum amplification to a wavelength range corresponding to the optical signal 102. For example, in some embodiments, the optical signal 102 may comprise a signal carrying data within the S-band of optical communications. In such a case, the optical fiber 108 may be configured to amplify signals within the S-band so that the optical signal 102 may be transmitted over a distance.

[0028] In these and other embodiments, amplified spontaneous emission (ASE) noise in wavelength ranges not corresponding to the optical signal 102 may be unavoidable. For example, when the optical signal 102 is amplified, ASE noise outside of the S-band may also be amplified. For example, the optical signal 102 may experience increased ASE noise within ranges such as a second wavelength range (e.g., the C-band and / or the L-band) and / or a third wavelength range (e.g., the E-band, which ranges from approximately 1360 nm to 1460 nm). Such increased ASE noise may affect the transmission quality of the optical signal 102.

[0029] In some embodiments, the EDFA 100 may include a filter 110 that may be configured to attenuate and / or reduce ASE noise present in wavelength ranges within the second wavelength range and / or the third wavelength range. In some embodiments, the filter 110 may be fiber-based. In these and other embodiments, the filter 110 may be made of any type of suitable optical fiber. For example, in some embodiments, the filter 110 may be made of dispersion compensating fiber (DCF). In these and other embodiments, the filter 110 may have a fiber-based loss profile and / or a corresponding gain profile to attenuate signals within the second wavelength range and / or the third wavelength range. The loss profile may represent different wavelengths at which signals experience attenuation within the fiber. In this disclosure, a reference to the filter 110 may include a reference to the fiber forming the filter 110. For example, a reference to the loss profile of the filter 110 may include a reference to the loss profile of the fiber forming the filter 110. Further, in this disclosure, a loss profile may also be referred to as a loss curve.

[0030] In some examples, the loss profile of filter 110 may be determined based at least in part on the refractive index profile of the fiber corresponding to filter 110. The refractive index profile may describe and / or represent how the refractive index of filter 110 varies across the cross-section of filter 110. For example, the refractive index profile may represent the refractive index of filter 110 at different locations of the optical fiber, such as the core and cladding. The refractive index of filter 110 may represent how light of different frequencies and / or wavelengths or amplified optical signal 102 propagates through filter 110.

[0031] Optical fibers generally can have different types of refractive index profiles. The type of refractive index profile can be determined based on the manufacturing process and / or external components. For example, an optical fiber can have a graded-index profile or a step-index profile. A particular optical fiber with a graded-index profile can have a refractive index that decreases continuously with increasing radial distance from the fiber axis or core. For example, a particular optical fiber can have a higher refractive index closer to the core than in the cladding.

[0032] In contrast, an optical fiber with a step-index profile may have a uniform refractive index within the core and an abrupt decrease in refractive index at the core-clad interface, such that the refractive index in the cladding is lower than that in the core. The refractive index in the cladding may be so low that the optical signal leaks at a constant value or rate.

[0033] FIG. 1B illustrates an exemplary graded index profile 120 that may correspond to a different generic optical fiber than filter 110. FIG. 1B is provided as an example so that the refractive index profile of filter 110, described with respect to FIG. 1C, may be contrasted with exemplary graded index profiles, such as graded index profile 120. In FIG. 1B, refractive index 122 decreases with increasing distance from the central core of the optical fiber. As refractive index 122 decreases, optical signals propagating through the optical fiber may leak and / or lose signal energy, especially as the optical signal travels further from the central core.

[0034] 1A , in some embodiments, the refractive index profile of filter 110 may be designed such that the refractive index profile of filter 110 is W-shaped. In some embodiments, filter 110 may be designed and / or manufactured such that filter 110 has a W-shaped refractive index profile. For example, different characteristics of filter 110, such as the materials of the core and cladding of filter 110, the use of dopants or co-dopants, etc., may be determined to modify the refractive index profile. Additionally or alternatively, manufacturing processes, such as manufacturing techniques, temperature and pressure control, etc., may be modified to produce filter 110 with a W-shaped refractive index profile.

[0035] A filter 110 with a W-shaped refractive index profile may have characteristics that allow the filter 110 to begin leaking signals at certain wavelengths because the propagation mode constant becomes negative at longer wavelengths. For example, unlike a graded-index profile, where the refractive index decreases gradually, the refractive index of a W-shaped refractive index profile may decrease abruptly at certain wavelengths, similar to a step-index profile. However, unlike a typical step-index profile, the refractive index or propagation mode constant of a W-shaped refractive index profile may decrease negatively, which generally does not occur in other fibers or refractive indices. Such a negative refractive index may increase leakage for signals at wavelengths corresponding to the negative refractive index.

[0036] For example, FIG. 1C shows an exemplary refractive index profile 124 of an optical fiber that may correspond to the refractive index profile of filter 110 of FIG. 1A in accordance with one or more embodiments of the present disclosure. In some embodiments, refractive index profile 124 may have a refractive index 126 that has a generally W-shape. For example, refractive index 126 may have a peak 127 or maximum refractive index that corresponds to a core portion of the optical fiber. In these and other embodiments, refractive index 126 may drop off sharply at a certain distance away from the center of the core. For example, refractive index 126 may drop off sharply at a first drop point 128a and a second drop point 128b.

[0037] In these and other embodiments, the refractive index 126 may decrease negatively until the first trench 129 a and the second trench 129 b. In some embodiments, the first trench 129 a and the second trench 129 b may correspond to the cladding of an optical fiber. For example, as the optical signal travels away from the core of the optical fiber, the refractive index may decrease sharply until it reaches the first trench 129 a and the second trench 129 b.

[0038] Returning to FIG. 1A , in some embodiments in which filter 110 has a W-shaped refractive index profile, filter 110 may have a corresponding loss curve that rises sharply at certain wavelengths. For example, abrupt drops (e.g., first drop point 128a and second drop point 128b in FIG. 1C ) and / or trenches (e.g., first trench 129a and second trench 129b in FIG. 1C ) present in the refractive index profile may cause abrupt rises in the corresponding loss curve. The loss curve may represent the attenuation or loss experienced by a signal as it propagates through filter 110. In some embodiments, the amount of attenuation experienced by an optical signal of a corresponding wavelength may vary based on the loss curve. For example, if the loss curve rises suddenly at a certain wavelength, the level of attenuation applied to the signal and / or noise at that wavelength may correspondingly increase. In some embodiments, such a characteristic of a W-shaped refractive index profile (e.g., abrupt rise in the loss curve at a certain wavelength) may be used to remove and / or attenuate ASE noise in an optical signal for wavelengths that do not carry meaningful data. For example, while optical fiber 108 performs amplification of optical signal 102 carrying data in a first wavelength range, undesired ASE noise may be added in a second wavelength range outside the first wavelength range. In these and other embodiments, optical signal 102 may pass through filter 110 following amplification using optical fiber 108 so that ASE noise in the second wavelength range may be reduced.

[0039] In some embodiments, the loss curve of filter 110 can be shifted such that the loss edge, i.e., the wavelength at which the loss curve rises sharply, can be shifted and / or modified. Such a shift of the loss edge can allow the frequency response of filter 110 to be adjusted, which can allow for control of the wavelength range at which signal and / or noise can be attenuated. For example, optical signal 102 and / or optical fiber 108 can have different characteristics in different applications, such that ASE noise can be increased at different wavelength ranges. In such an example, the frequency response or loss curve of filter 110 can be adjusted so that filter 110 can accommodate optical signal 102 and / or optical fiber 108.

[0040] In some embodiments, the loss edge may shift based on bending of filter 110. For example, bending filter 110 may shift the refractive index profile and corresponding loss edge of filter 110. In some embodiments, the bend radius or level of bend applied to filter 110 may control how much the loss edge may shift. For example, in some embodiments, as the bending radius decreases (e.g., a tighter bend), the loss edge of filter 110 may shift toward shorter wavelengths.

[0041] For example, FIG. 1D illustrates an exemplary loss profile 130 illustrating the loss curve of an optical fiber according to one or more embodiments of the present disclosure. For example, the loss profile 130 may correspond to the filter 110 of FIG. 1A. In these and other embodiments, the optical fiber may have a W-shaped refractive index profile as shown in FIG. 1C. In some embodiments, the loss profile 130 may have a first loss curve 132 that represents the loss curve of the filter 110 without modification or bending. For example, the first bend radius corresponding to the first loss curve 132 may be zero. In some embodiments, the first loss curve 132 may have a first loss edge 133 along which the loss curve rises. In these and other embodiments, signals at wavelengths corresponding to the wavelength of the first loss curve 132 at or past the first loss edge 133 may experience increased attenuation. In some embodiments, as an example, the first loss edge 133 may be approximately 1600 nm. In such cases, signals and / or noise at wavelengths of 1600 nm or greater may experience increased attenuation.

[0042] In some embodiments, the loss profile 130 may exhibit a second loss curve 134 having a second loss edge 135. In these and other embodiments, the second loss curve 134 may represent the loss curve of the filter 110 when the filter 110 is modified or bent at a second bend radius. In some embodiments, the second bend radius may be greater than the first bend radius. In these and other embodiments, the second loss curve 134 and the second loss edge 135 may be shifted toward shorter wavelengths compared to the first loss curve 132 and the first loss edge 133. For example, the second loss edge 135 may be near 1530 nm, and signals and / or noise at wavelengths greater than 1530 nm may be attenuated. For example, signals in the C-band (e.g., 1530 nm to 1565 nm) and the L-band (e.g., 1565 nm to 1625 nm) may be attenuated. Such attenuation may allow amplification of signals in the S-band (eg, 1495 nm to 1530 nm) while reducing ASE noise in the C-band and L-band.

[0043] In some embodiments, loss profile 130 may exhibit a third loss curve 136 having a third loss edge 137. In these and other embodiments, third loss curve 136 may represent the loss curve of filter 110 bent at a third bend radius greater than the first and second bend radii. In these and other embodiments, third loss curve 136 and third loss edge 137 may be shifted to shorter wavelengths than second loss curve 134 and second loss edge 135. For example, third loss edge 137 may be near 1400 nm, such that signals and / or noise above 1400 nm may be attenuated. While loss profile 130 exhibits first loss edge 133, second loss edge 135, and third loss edge 137, loss profile 130 may have any other suitable loss edges and corresponding loss curves based on the bend radius of the optical fiber.

[0044] FIG. 1E illustrates another exemplary loss profile 140 of an optical fiber according to some embodiments of the present disclosure. In some embodiments, the loss profile 140 may be the loss profile of the filter 110 of FIG. 1A. In some embodiments, the loss profile 140 may be associated with an ASE spectrum 142 that represents the level of ASE noise caused by an EDFA, such as the EDFA 100 of FIG. 1A. In particular, the ASE spectrum 142 may represent the noise caused by the optical fiber 108 when the optical fiber 108 performs amplification of the optical signal 102. For example, the ASE spectrum 142 may indicate an increase in ASE noise at a certain wavelength (e.g., 1500 nm). In these and other embodiments, the loss edge of the filter 110 may be controlled based on the bend radius of the filter 110 such that the ASE spectrum 142 may be substantially compensated. For example, the filter 110 may have a first loss curve 144. In some embodiments, the first loss curve 144 may represent the loss curve of the filter 110 at a first bend radius. In some embodiments, the first bend radius may be zero (e.g., the optical fiber 108 may not be bent or modified). In some examples, the first loss curve 144 may have a first loss edge (e.g., 1530 nm) greater than a particular wavelength where the ASE spectrum rises. In such cases, the ASE noise may not be substantially compensated. For example, in an optical fiber having the first loss curve 144, ASE noise present at wavelengths between the particular wavelength and the first loss edge may not be attenuated.

[0045] In these and other embodiments, filter 110 may be bent to have a bend radius such that the loss edge of the optical fiber may be shifted to correspond to ASE spectrum 142. For example, filter 110 may be bent at a second bend radius that is greater than the first bend radius. In these and other embodiments, the loss curve of filter 110 may be shifted toward shorter wavelengths. For example, second loss curve 146 may represent the loss curve of filter 110 bent at the second bend radius. Such bending may shift the loss curve toward shorter wavelengths corresponding to second loss curve 146.

[0046] In some embodiments, in response to determining that the loss curve with filter 110 bent at the second bend radius still does not correspond to ASE spectrum 142, filter 110 may be bent at a third bend radius. In these and other embodiments, the third bend radius may be adjusted until third loss curve 148 substantially aligns with ASE spectrum 142. In these and other embodiments, substantial alignment between ASE spectrum 142 and second loss curve 148 may cause substantial attenuation of ASE noise.

[0047] Returning to FIG. 1A , in some embodiments, the bend radius of filter 110 may be adjusted based on optical signal 102. For example, optical signal 102 may carry data within a first wavelength range. In some embodiments, the first wavelength range may correspond to the S-band. In these and other embodiments, the bend radius of filter 110 may be determined so that the loss curve is shifted to attenuate ASE noise within a second wavelength range covering wavelengths longer than the S-band. For example, the second wavelength range may correspond to wavelengths longer than 1530 nm. In these and other embodiments, filter 110 may be bent so that the loss curve has a loss edge near 1530 nm. In these and other embodiments, EDFA 100 may amplify optical signal 102 in the S-band (e.g., 1495 nm to 1530 nm) while attenuating ASE noise in the C-band and L-band.

[0048] In these and other embodiments, the characteristics of the loss curve corresponding to the W-shaped refractive index profile may allow for flexible attenuation of noise associated with the amplification of the optical signal 102. For example, the loss curve and corresponding loss edge may vary based on the particular optical fiber. The ability to shift the loss edge to a certain wavelength range allows for amplification of the optical signal 102 regardless of the natural loss edge of the filter 110 (e.g., the loss edge of the filter 110 as manufactured).

[0049] In some embodiments, filter 110 may be bent using a bending structure. For example, filter 110 may be positioned near a bending structure such that filter 110 is bent with a bend corresponding to the bend radius. In these and other embodiments, the bending structure may have a set of varying diameters such that the bend radius of filter 110 may be adjusted. Examples of bending structures having a set of varying diameters may be disclosed in further detail in this disclosure, such as with respect to Figures 2A and 2B.

[0050] Modifications, additions, or omissions may be made to EDFA 100 without departing from the scope of the present disclosure. For example, in some embodiments, system 100 may include any number of other components that may not be explicitly shown or described. For example, in some embodiments, EDFA 100 may have multiple amplification stages.

[0051] For example, certain components shown in FIG. 1 may be repeated multiple times. For example, the EDFA 100 may include a second erbium-doped optical fiber configured to perform amplification of the optical waveform. The EDFA 100 may include a second optical pump configured to output a second optical pump signal. The EDFA 100 may include a second optical coupler configured to couple the second optical pump signal and the amplified signal 112 onto the second optical fiber so that the amplified signal 112 may be further amplified. In these and other embodiments, the EDFA 100 may include a second filter configured to attenuate the amplified signal 112 after additional amplification by the second optical fiber. The second filter may be configured to attenuate the amplified signal 112 for various wavelength ranges depending on a second bend radius of the second filter. The second filter may be bent using a second bending structure. In some embodiments, the EDFA 100 may include additional amplification stages. For example, as the transmission distance of the optical signal 102 increases, the EDFA 100 may include additional amplification stages.

[0052] 2A shows a diagram of an exemplary bending structure 200 according to one or more embodiments of the present disclosure. In some embodiments, bending structure 200 can have a conical shape in which the diameter of bending structure 200 gradually increases. For example, bending structure 200 can include a first end 202, a second end 204, and a body 206 extending between first end 202 and second end 204. In some embodiments, first end 202 can have a first diameter, and second end 204 can have a second diameter that is larger than the first diameter. In these and other embodiments, the diameter of body 206 can gradually increase from the first diameter to the second diameter as body 206 progresses from first end 202 to second end 204.

[0053] In these and other embodiments, an optical fiber 208 (e.g., filter 110 in FIG. 1A ) may be positioned near a bending structure 200 such that the optical fiber 208 is bent. Varying diameters of the bending structure may be used to control the bend radius of the optical fiber 208, which may shift the loss curve of the optical fiber. In some embodiments, the conical shape of the bending structure 200 may allow convenient adjustment of the bend radius as the optical fiber 208 may be moved between the first end 202 and the second end 204. In some embodiments, the bending structure 200 may be fabricated using any material suitable for bending the optical fiber 208 and allowing the optical fiber to move therealong. For example, the bending structure 200 may be fabricated using stainless steel, aluminum, glass, etc.

[0054] Modifications, additions, or omissions may be made to bending structure 200 without departing from the scope of the present disclosure. For example, in some embodiments, bending structure 200 may include any number of other components that may not be explicitly shown or described.

[0055] 2B shows another exemplary bending structure 210 according to one or more embodiments of the present disclosure. In some embodiments, the bending structure 210 may include a set of cylinders having a set of varying diameters. For example, the bending structure 210 may include a first cylinder 212a having a first diameter, a second cylinder 212b having a second diameter, a third cylinder 212c having a third diameter, a fourth cylinder 212d having a fourth diameter, a fifth cylinder 212e having a fifth diameter, and a sixth cylinder 212f having a sixth diameter. In some embodiments, the diameters may gradually increase from the first diameter to the sixth diameter. In these and other embodiments, the cylinders may be stacked and / or connected in order of increasing and / or decreasing diameter. For example, the cylinders may be connected in the following order: first cylinder 212a, second cylinder 212b, third cylinder 212c, fourth cylinder 212d, fifth cylinder 212e, and sixth cylinder 212f. Although shown as having six cylinders, bending structure 210 may include any suitable number of cylinders having various diameters.

[0056] In some embodiments, optical fiber 214 (e.g., filter 110 of FIG. 1A) may be positioned around one of the cylinders such that optical fiber 214 can be bent at a bend radius. In these and other embodiments, optical fiber 214 may be positioned around one of the cylinders such that the bend radius can be controlled and / or adjusted based on the diameter of the cylinder. For example, when optical fiber 214 is positioned around first cylinder 212a, optical fiber 214 can be bent at a minimum bend radius that may cause increased tension on optical fiber 214.

[0057] In some embodiments, in response to determining that the bend radius of the optical fiber around the first cylinder 212a is too tight, the optical fiber 214 may be moved to be disposed around another cylinder having a larger diameter. In such a case, the first cylinder 212a may be released away from the optical fiber 214, thereby releasing the tension on the optical fiber 214. The bending structure 210 may be shifted so that a cylinder having a larger diameter, such as the third cylinder 212c, is aligned with the optical fiber 214. The bending structure may be shifted back toward the optical fiber 214 so that the third cylinder 212c engages the optical fiber 214 and applies tension within the optical fiber 214. In some embodiments, the bending structure 210 may be fabricated using any material suitable for bending the optical fiber 214. For example, the bending structure 210 may be fabricated using stainless steel, aluminum, glass, etc.

[0058] Modifications, additions, or omissions may be made to bending structure 210 without departing from the scope of the present disclosure. For example, in some embodiments, bending structure 210 may include any number of other components that may not be explicitly shown or described.

[0059] 3 is a flowchart of an example method 300 of performing amplification on an optical signal using an EDFA, configured in accordance with at least one embodiment of the present disclosure. One or more operations of method 300 may be implemented by any suitable elements of an EDFA, such as EDFA 100 of FIG. 1A, and bending structures, such as bending structure 200 of FIG. 2A and bending structure 210 of FIG. 2B. Although shown as separate steps, various steps of method 300 may be divided into additional steps, combined into fewer steps, or eliminated, depending on the desired implementation. Furthermore, the order in which different steps are performed may vary depending on the desired implementation.

[0060] In some embodiments, method 300 may include block 302. In block 302, an optical signal and an optical pump signal may be acquired and / or received at an EDFA. In some embodiments, the optical signal may include data at a wavelength corresponding to a first wavelength range (e.g., S-band). In some embodiments, the optical signal may correspond to optical signal 102 of FIG. 1A, and the optical pump signal may correspond to the optical pump signal generated by optical pump 104 of FIG. 1A.

[0061] In block 304, the optical signal and the optical pump signal may be multiplexed by an optical coupler onto an erbium-doped optical fiber, such as optical fiber 108 in FIG. 1A. In some embodiments, the optical fiber may be configured to perform amplification of an optical waveform within a first wavelength range. For example, the optical fiber may be configured to amplify an S-band optical signal.

[0062] In block 306, the signal within the first wavelength range of the optical signal may be amplified using an optical fiber. For example, the optical signal may be propagated through an optical fiber, and ions in the optical fiber may interact with the optical pump signal to output energy that may be used to amplify the optical signal.

[0063] At block 308, a bend radius of the filter may be adjusted such that the filter is configured to attenuate signals in a second wavelength range. In some embodiments, the second wavelength range may include a wavelength range that includes longer wavelengths than the first wavelength range. For example, if the first wavelength range corresponds to the S-band, the second wavelength range may correspond to the C-band and / or L-band of optical communications.

[0064] In some embodiments, the filter may be a fiber-based filter, where the filter may attenuate signals based on the loss profile of the fiber. In some embodiments, the filter may have a W-shaped refractive index profile, as shown in FIG. 1C. In these and other embodiments, the filter may have a loss curve that rises at a wavelength, which may vary based on the bend radius of the filter, as shown in FIGS. 1D-1E. In some embodiments, the bend radius of the filter may be adjusted such that the loss curve of the filter may be shifted to correspond to a second wavelength range. For example, the loss curve may be shifted such that signals within a first wavelength range are not attenuated, while signals and noise outside the first wavelength range (e.g., a second wavelength range) are attenuated and / or lost. For example, the bend radius may be determined based on the location of a loss edge on the loss curve of the filter. In some embodiments, adjusting the loss curve of a filter based on the bend radius of the bend in the filter may be described in further detail in this disclosure, such as with respect to filter 110 of FIG. 1A.

[0065] In some embodiments, the bend radius of the filter may be adjusted using a bending structure having a set of varying diameters. For example, a bending structure such as that shown in Figures 2A-2B of the present disclosure may be obtained. The filter may be disposed around the bending structure such that the bend radius is adjustable by moving the filter along different portions of the bending structure that correspond to different diameters of the set of varying diameters.

[0066] In block 310, signals in the second wavelength range may be attenuated. In some embodiments, the attenuation may allow ASE noise generated from amplification of the optical signal in the optical fiber to be reduced. Such attenuation allows the optical signal to be amplified without the quality of the optical signal being affected by undesired noise signals. In some embodiments, the EDFA may further attenuate signals in a third wavelength range. For example, one or more additional filters may be used to attenuate signals in the third wavelength range. In these and other embodiments, the third wavelength range may correspond to a wavelength range that includes shorter wavelengths than the first wavelength range. For example, the third wavelength range may correspond to the E-band of optical communications.

[0067] Modifications, additions, or omissions may be made to method 300 without departing from the scope of the present disclosure. For example, those skilled in the art will understand that the functions and / or operations performed for this and other processes, operations, and methods disclosed herein may be implemented in a different order. Furthermore, the outlined functions and operations are provided only as examples, and some of the functions and operations may be optional, combined into fewer functions and operations, or expanded into additional functions and operations without detracting from the essence of the disclosed embodiments.

[0068] 4 illustrates a block diagram of an exemplary computing system 400 that may be used in connection with an EDFA, in accordance with at least one embodiment of the present disclosure. For example, computing system 400 may be used to adjust the pumping wavelength of a pump source (e.g., one or more of the pump sources described above) of the EDFA and / or the frequency response of a filter (e.g., one or more of the filters described above) of the EDFA. Additionally or alternatively, computing system 400 may be used to determine a bend radius of the EDFA to modify the loss profile of the EDFA.

[0069] The computing system 400 may include a processor 410, a memory 412, and a data storage 414. The processor 410, the memory 412, and the data storage 414 may be communicatively coupled.

[0070] In general, processor 410 may include any suitable special-purpose or general-purpose computer, computing entity, or processing device, including various computer hardware or software modules, and may be configured to execute instructions stored on any applicable computer-readable storage medium. For example, processor 410 may include a microprocessor, microcontroller, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or any other digital or analog circuit configured to interpret and / or execute program instructions and / or process data. Although shown as a single processor in FIG. 4 , processor 410 may include any number of processors configured to individually or collectively perform or direct the execution of any number of operations described in this disclosure. Additionally, one or more of the processors may reside on one or more different electronic devices, such as different servers.

[0071] In some embodiments, processor 410 may be configured to interpret and / or execute program instructions and / or process data stored in memory 412, data storage 414, or memory 412 and data storage 414. In some embodiments, processor 410 may fetch program instructions from data storage 414 and load the program instructions into memory 412. After the program instructions are loaded into memory 412, processor 410 may execute the program instructions.

[0072] Memory 412 and data storage 414 may include computer-readable storage media that carry or store computer-executable instructions or data structures. Such computer-readable storage media may include any available media that can be accessed by a general-purpose or special-purpose computer, such as processor 410. By way of example, and not limitation, such computer-readable storage media may include tangible or non-transitory computer-readable storage media including random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory devices (e.g., solid-state memory devices), or any other storage medium that can be used to store specific program code in the form of computer-executable instructions or data structures and that can be accessed by a general-purpose or special-purpose computer. Combinations of the above may also be included within the scope of computer-readable storage media. Computer-executable instructions may include, for example, instructions and data configured to cause processor 410 to perform a certain operation or group of operations.

[0073] Modifications, additions, or omissions may be made to computing system 400 without departing from the scope of the present disclosure. For example, in some embodiments, computing system 400 may include any number of other components that may not be explicitly shown or described.

[0074] The terms used in this disclosure, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including, but not limited to," etc.).

[0075] Furthermore, where a specific number of introduced claim recitations is intended, such intention will be expressly recited in the claim; absent such recitation, no such intention exists. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that introducing a claim recitation with the indefinite article "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation. This is true even if the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be construed to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations.

[0076] Additionally, even when a particular number of introduced claim recitations is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the recitation "two recitations" without other modifiers means at least two recitations, or more than two recitations). Furthermore, when idiomatic expressions similar to "at least one of A, B, and C, etc." or "one or more of A, B, and C, etc." are used, such constructions are generally intended to include A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together, etc. Furthermore, use of the term "and / or" is intended to be interpreted in this manner.

[0077] Furthermore, any disjunctive phrase presenting two or more alternative terms, whether in the present document, claims, or drawings, should be understood to contemplate the inclusion of one of those terms, either of those terms, or both terms. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B" or "A and B," even if the term "and / or" is used elsewhere.

[0078] All examples and conditional language set forth in this disclosure are intended for educational purposes to aid the reader in understanding the disclosure and the concepts contributed by the inventor to further the art, and should be construed as not being limited to such specifically set forth examples and conditions. Although embodiments of the present disclosure have been described in detail, various changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the present disclosure.

[0079] The following additional notes are provided regarding the embodiments including the above examples. (Appendix 1) a first bent structure having a plurality of diameters; a first erbium-doped optical fiber (the "first optical fiber") configured to perform amplification of an optical waveform; an optical pump configured to output an optical pump signal; an optical coupler coupled to the optical pump and the optical fiber, the optical coupler configured to multiplex one or more optical data signals and the optical pump signal onto the optical fiber; A first fiber-based filter ("first filter") comprising: attenuating the optical waveform for a wavelength range that varies depending on a bend radius of a bend in the first filter; a first filter disposed around a first bending structure to form the bend, and disposed such that the bending radius is adjustable by moving the first filter along different portions of the first bending structure corresponding to different diameters of the plurality of diameters; The first filter is configured as follows: An optical amplifier having: (Appendix 2) 2. The optical amplifier of claim 1, wherein the first optical fiber is configured to amplify signals within a first wavelength range. (Appendix 3) 3. The optical amplifier of claim 2, wherein the bend radius is adjusted such that the filter is configured to attenuate a second wavelength range of optical communications, the second wavelength range being greater than the first wavelength range. (Appendix 4) the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to one or more of the C-band or the L-band of optical communications; 4. An optical amplifier as defined in claim 3. (Appendix 5) 2. The optical amplifier of claim 1, wherein the filter has a W-shaped refractive index profile. (Appendix 6) 6. The optical amplifier of claim 5, wherein the bend radius of the filter is determined based on the W-shaped refractive index profile. (Appendix 7) 7. The optical amplifier of claim 6, wherein the bend radius of the filter is determined further based on the wavelength of the one or more optical data signals. (Appendix 8) 2. The optical amplifier of claim 1, wherein the first bending structure has a conical shape with a first end and a second end, the first end having a first diameter smaller than a second diameter of the second end, and the conical shape includes the plurality of diameters increasing in diameter from the first end to the second end. (Appendix 9) 2. An optical amplifier as described in claim 1, wherein the first bending structure includes a plurality of cylinders corresponding to the plurality of diameters. (Appendix 10) the plurality of diameters of the first bending structure are a first plurality of diameters, and the optical amplifier comprises: a second bent structure having a second plurality of diameters; a second erbium-doped optical fiber configured to provide amplification of optical waveforms over a varying wavelength range; a second optical pump configured to output a second optical pump signal; a second optical coupler coupled to the second optical pump and the second optical fiber, the second optical coupler configured to multiplex an output optical data signal from the first optical fiber and the second optical pump signal onto the second optical fiber; a second fiber-based filter ("second filter"), attenuating the optical waveform for a wavelength range that varies depending on a second bend radius of a second bend in the second filter; a second filter disposed around a second bending structure to form the second bend, and disposed such that the second bend radius is adjustable by moving the second filter along different portions of the second bending structure corresponding to different diameters of the plurality of diameters; and a second filter configured as follows: 2. The optical amplifier of claim 1, further comprising: (Appendix 11) obtaining an optical signal and an optical pump signal; multiplexing, by an optical coupler, the optical signal and the optical pump signal onto an erbium-doped optical fiber, the optical fiber configured to perform amplification of an optical waveform within a first wavelength range; adjusting a bend radius of a bend in the fiber-based filter such that the fiber-based filter is configured to attenuate signals within a second wavelength range of optical communications, the second wavelength range including wavelengths longer than the first wavelength range, and the filter configured to perform attenuation of the optical waveform for a wavelength range that varies depending on the bend radius of the bend in the filter; attenuating the signals within the second wavelength range using the filter bent at the bend radius; 12. A method for amplifying a signal, comprising: (Appendix 12) the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to one or more of the C-band or the L-band of optical communications; 12. A method for amplifying a signal as described in Appendix 11. (Appendix 13) the filter is disposed around a bent structure having multiple diameters, and wrapping the filter around the bent structure forms the bends in the filter; adjusting the bend radius of the filter includes moving the position of the filter along the bent structure such that the filter is wrapped around a particular portion of the bent structure having a particular diameter corresponding to the bend having the bend radius; 12. A method for amplifying a signal as described in Appendix 11. (Appendix 14) 14. The method of amplifying a signal of claim 13, wherein the bending structure has a conical shape with a first end and a second end, the first end having a first diameter, the second end having a second diameter larger than the first diameter, and the diameter of the bending structure gradually increasing from the first end to the second end. (Appendix 15) 14. The method of amplifying a signal described in claim 13, wherein the bending structure includes a plurality of cylindrical structures corresponding to the plurality of diameters. (Appendix 16) 12. The method of amplifying a signal of claim 11, wherein the bend radius is determined based on a position of a loss edge on a loss curve corresponding to the filter, the loss curve corresponding to a W-shaped refractive index profile of the filter. (Appendix 17) One or more non-transitory computer-readable media storing instructions that, when executed by one or more processors, cause a system to perform operations, the operations including: obtaining an optical signal and an optical pump signal; multiplexing, by an optical coupler, the optical signal and the optical pump signal onto an erbium-doped optical fiber, the optical fiber configured to perform amplification of optical waveforms over a varying wavelength range; amplifying signals within a first wavelength range of the optical signal using the optical fiber; determining a bend radius of a bend in a fiber-based filter based on the optical signal and a loss curve of the filter, the filter configured to attenuate a second wavelength range of optical communication, the second wavelength range including wavelengths longer than the first wavelength range, and the filter configured to perform optical waveform attenuation for a wavelength range that varies depending on the bend radius of the bend; adjusting the bend radius of the filter; attenuating the second wavelength range of the optical communication;

[0023] 1. One or more non-transitory computer-readable media, including: (Appendix 18) The action further comprises: attenuating a third wavelength range that includes wavelengths shorter than the first wavelength range. 18. One or more non-transitory computer-readable media as described in Clause 17. (Appendix 19) the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to at least the E-band of optical communications; The third wavelength range corresponds to at least the C-band of optical communications. 19. One or more non-transitory computer-readable media as described in Clause 18. (Appendix 20) 18. The one or more non-transitory computer-readable media of claim 17, wherein the bend radius of the filter is adjusted using a bending structure. [Explanation of symbols]

[0080] 110 Filters 102 Optical Signal 104 Pump 106 Coupler 108 Erbium-doped optical fiber 110 Filters 112 Amplified Signal 302 Acquire optical signal and optical pump signal 304. An optical coupler multiplexes the optical signal and the optical pump signal onto an erbium-doped optical fiber, the optical fiber configured to perform amplification of an optical waveform within a first wavelength range. 306 Amplifying a signal within a first wavelength range of an optical signal using an optical fiber 308. Adjusting a bend radius of the fiber-based filter such that the filter is configured to attenuate signals within a second wavelength range of the optical communication, the second wavelength range including wavelengths longer than the first wavelength range, the filter configured to perform attenuation of the optical waveform for various wavelength ranges depending on the bend radius of the bend of the filter. 400 System 410 processor 412 memory 414 Data Storage

Claims

1. a first bent structure having a plurality of diameters; a first erbium-doped optical fiber ("first optical fiber") configured to perform amplification of an optical waveform; an optical pump configured to output an optical pump signal; an optical coupler coupled to the optical pump and the optical fiber, the optical coupler configured to multiplex one or more optical data signals and the optical pump signal onto the optical fiber; A first fiber-based filter ("first filter") comprising: attenuating the optical waveform for a wavelength range that varies depending on a bend radius of a bend in the first filter; a first filter disposed around a first bending structure to form the bend, and disposed such that the bending radius is adjustable by moving the first filter along different portions of the first bending structure corresponding to different diameters of the plurality of diameters; The first filter is configured as follows: An optical amplifier having:

2. The optical amplifier of claim 1 , wherein the first optical fiber is configured to amplify signals within a first wavelength range.

3. 3. The optical amplifier of claim 2, wherein the bend radius is adjusted such that the filter is configured to attenuate a second wavelength range of optical communications, the second wavelength range being greater than the first wavelength range.

4. the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to one or more of the C-band or the L-band of optical communications; 4. An optical amplifier according to claim 3.

5. The optical amplifier of claim 1 , wherein the filter has a W-shaped refractive index profile.

6. The optical amplifier of claim 5 , wherein the bend radius of the filter is determined based on the W-shaped refractive index profile.

7. 7. The optical amplifier of claim 6, wherein the bend radius of the filter is determined further based on the wavelength of the one or more optical data signals.

8. 2. The optical amplifier of claim 1, wherein the first bending structure has a conical shape with a first end and a second end, the first end having a first diameter that is smaller than a second diameter of the second end, and the conical shape includes the plurality of diameters that increase in diameter from the first end to the second end.

9. The optical amplifier of claim 1 , wherein the first bending structure includes a plurality of cylinders corresponding to the plurality of diameters.

10. the plurality of diameters of the first bending structure are a first plurality of diameters, and the optical amplifier comprises: a second bent structure having a second plurality of diameters; a second erbium-doped optical fiber configured to provide amplification of optical waveforms over a varying wavelength range; a second optical pump configured to output a second optical pump signal; a second optical coupler coupled to the second optical pump and the second optical fiber, the second optical coupler configured to multiplex an output optical data signal from the first optical fiber and the second optical pump signal onto the second optical fiber; a second fiber-based filter ("second filter"), attenuating the optical waveform for a wavelength range that varies depending on a second bend radius of a second bend in the second filter; a second filter disposed around a second bending structure to form the second bend, and disposed such that the second bend radius is adjustable by moving the second filter along different portions of the second bending structure corresponding to different diameters of the plurality of diameters; and a second filter configured as follows:

10. The optical amplifier of claim 1, further comprising:

11. obtaining an optical signal and an optical pump signal; multiplexing, by an optical coupler, the optical signal and the optical pump signal onto an erbium-doped optical fiber, the optical fiber configured to perform amplification of an optical waveform within a first wavelength range; adjusting a bend radius of a bend in the fiber-based filter such that the fiber-based filter is configured to attenuate signals within a second wavelength range of optical communications, the second wavelength range including wavelengths longer than the first wavelength range, and the filter configured to perform attenuation of the optical waveform for a wavelength range that varies depending on the bend radius of the bend in the filter; attenuating the signals within the second wavelength range using the filter bent at the bend radius; 12. A method for amplifying a signal, comprising:

12. the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to one or more of the C-band or the L-band of optical communications; 12. A method for amplifying a signal according to claim 11.

13. the filter is disposed around a bent structure having multiple diameters, and wrapping the filter around the bent structure forms the bends in the filter; adjusting the bend radius of the filter includes moving the position of the filter along the bent structure such that the filter is wrapped around a particular portion of the bent structure having a particular diameter corresponding to the bend having the bend radius; 12. A method for amplifying a signal according to claim 11.

14. 14. The method of claim 13, wherein the bending structure has a conical shape having a first end and a second end, the first end having a first diameter, the second end having a second diameter greater than the first diameter, and the diameter of the bending structure gradually increasing from the first end to the second end.

15. 14. The method of amplifying a signal of claim 13, wherein the bent structure comprises a plurality of cylindrical structures corresponding to the plurality of diameters.

16. 12. The method of amplifying a signal of claim 11, wherein the bend radius is determined based on a position of a loss edge on a loss curve corresponding to the filter, the loss curve corresponding to a W-shaped refractive index profile of the filter.

17. One or more non-transitory computer-readable media storing instructions that, when executed by one or more processors, cause a system to perform operations, the operations including: obtaining an optical signal and an optical pump signal; multiplexing the optical signal and the optical pump signal onto an erbium-doped optical fiber by an optical coupler, the optical fiber being configured to perform amplification of optical waveforms over a varying wavelength range; amplifying signals within a first wavelength range of the optical signal using the optical fiber; determining a bend radius of a bend in a fiber-based filter based on the optical signal and a loss curve of the filter, the filter being configured to attenuate a second wavelength range of optical communication, the second wavelength range including wavelengths longer than the first wavelength range, and the filter being configured to perform optical waveform attenuation for a wavelength range that varies depending on the bend radius of the bend; adjusting the bend radius of the filter; attenuating the second wavelength range of the optical communication; [0023] 1. One or more non-transitory computer-readable media, including:

18. The operations further comprise: attenuating a third wavelength range that includes wavelengths shorter than the first wavelength range.

20. One or more non-transitory computer-readable media as recited in claim 17.

19. the first wavelength range corresponds to the S-band of optical communications; the second wavelength range corresponds to at least the E-band of optical communications; The third wavelength range corresponds to at least the C-band of optical communications.

20. One or more non-transitory computer-readable media as recited in claim 18.

20. 20. The one or more non-transitory computer-readable media of claim 17, wherein the bend radius of the filter is adjusted using a bending structure.

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