Method and system for filtering optical signal spectra using amplifier enhancement

Abstract

To provide a method and system for filtering broadband light. [Solution] A broadband optical signal is filtered several times, and while or after being filtered, it is optically amplified once or multiple times and provided to an optical receiving device. The optical filtering may include using the same or different filtering functions. When the optical filtering includes different filtering functions, the first of the different filtering functions may include phase and amplitude filtering, and the second of the different filtering functions may include amplitude-only filtering.

Description

Technical Field

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[0001] The present disclosure relates to methods and systems for optically filtering broadband optical signal spectra, and more particularly, to methods and systems for optically shaping or filtering broadband optical signal spectra using amplifier enhancement.

Background Art

[0002] There is a continuing desire to generate broadband optical signal spectra, for example, spectra having wavelengths (near infrared) between 1520 and 1610 nm with sharp features or transitions. For example, as shown in FIG. 1, a desired broadband optical signal spectrum 2 may include sharp features or transitions 4-14, where the slope of the desired broadband optical signal spectrum 2 (e.g., at 4, 6, 10, and 12) may, for example, change abruptly or suddenly from a positive slope to a negative slope, or vice versa, or (e.g., at 8 and 14) from a negative (or positive) slope having a first value to a negative (or positive) slope having a second value.

[0003] However, in practice, with currently state-of-the-art methods and systems for filtering broadband optical signal spectra, these sharp features or transitions are smoothed in the realized broadband optical signal spectrum 16, as shown, for example, at 4’-14’.

Summary of the Invention

Problems to be Solved by the Invention

[0004]

Means for Solving the Problems

[0005] A method for filtering a broadband optical signal is disclosed. The method may include the steps of: (a) outputting a broadband optical signal; (b) filtering the broadband optical signal multiple times; (c) optically amplifying the broadband optical signal; and (d) providing the filtered and amplified broadband optical signal to an optical receiving device.

[0006] Also disclosed is a method for filtering a broadband optical signal, which includes the steps of: (a) passing the broadband optical signal through a first wavelength selective switch (WSS1) multiple times; (b) amplifying the broadband optical signal during at least one set of passes of the broadband optical signal through WSS1 in step (a); (c) passing the broadband optical signal through a second wavelength selective switch (WSS2) multiple times after steps (a) and (b); and (d) amplifying the broadband optical signal during at least one set of passes of the broadband optical signal through WSS2 in step (c).

[0007] Finally, a broadband optical signal filtering system is also disclosed, comprising a first optical amplifier and a second optical amplifier, and a first wavelength-selective switch and a second wavelength-selective switch (WSS1 and WSS2) connected thereto, wherein a broadband optical signal passes through the broadband optical signal filtering system in the following order: (a) WSS1 at least once, (b) the first optical amplifier, (c) WSS1 at least one more time, (d) WSS2 at least once, (e) the second optical amplifier, and (f) WSS2 at least one more time. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a schematic plot illustrating the frequency vs. gain of the realized broadband optical signal spectrum for a desired broadband optical signal spectrum.

[0009] [Figure 2A]This figure shows a schematic example of a broadband optical signal filtering system in accordance with the principles of this disclosure.

[0010] [Figure 2B] This is a schematic flowchart of the broadband optical signal filtering system shown in Figure 2A, which more clearly illustrates the flow of optical signals through the broadband optical signal filtering system shown in Figure 2A.

[0011] [Figure 3A] This figure shows another schematic example of a broadband optical signal filtering system in accordance with the principles of this disclosure.

[0012] [Figure 3B] This is a schematic flowchart of the broadband optical signal filtering system shown in Figure 3A, which more clearly illustrates the flow of optical signals through the broadband optical signal filtering system shown in Figure 3A.

[0013] [Figure 4A] This figure shows yet another schematic example of a broadband optical signal filtering system in accordance with the principles of this disclosure.

[0014] [Figure 4B] This is a schematic flowchart of the broadband optical signal filtering system shown in Figure 4A, which more clearly illustrates the flow of optical signals passing through the broadband optical signal filtering system shown in Figure 4A.

[0015] [Figure 5A] Figures 2A to 4B show schematic example plots of frequency versus gain for broadband optical signal spectra output by the exemplary broadband optical signal filtering systems.

[0016] [Figure 5B] This is a magnified view of the circled portion of the schematic example plot of frequency versus gain in the broadband optical signal spectrum shown in Figure 5A, after it has been separated. [Modes for carrying out the invention]

[0017] When used herein, terms relating to space or direction, such as “left,” “right,” “inside,” “outside,” “above,” “below,” and others, are relating to this disclosure as shown in the drawings. However, it should be understood that this disclosure may assume various alternative orientations, and therefore such terms should not be considered limiting. Furthermore, when used herein, all figures used in this specification and in the claims to express dimensions, physical properties, processing parameters, amounts of components, reaction conditions, and others should be understood in all cases to be modified by the term “approximately” or “about.” Therefore, unless otherwise indicated, the figures specified in the following specification and claims may vary depending on the desired properties to be obtained by this disclosure.

[0018] At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical value should be interpreted at least in light of the reported number of significant figures and by applying ordinary rounding techniques. Furthermore, all scopes disclosed herein should be understood to encompass the starting and ending scope values, and all sub-scopes contained therein. For example, the scope described as "1 to 10" should be understood to include all sub-scopes between the minimum value of 1 and the maximum value of 10 (and including them), that is, all sub-scopes starting with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5, 5.5 to 10, and so on. "A" or "an" refers to one or more.

[0019] As used herein, the terms "coupled," "coupling," and the like refer to two or more elements that are joined, connected, fastened, attached, in communication, or otherwise associated with each other (e.g., mechanically, electrically, fluidically, optically, electromagnetically). In various examples, the elements may be associated directly or indirectly. As an example, element A may be directly associated with element B. As another example, element A may be indirectly associated with element B, e.g., via another element C. It will be understood that not all associations between the various disclosed elements are necessarily represented. Thus, couplings other than those depicted in the figures may also exist.

[0020] As used herein, the phrase "at least one of" when used with a list of items means that different combinations of one or more of the listed items may be used and only one of each item in the list may be required. For example, "at least one of item A, item B, and item C" may, without limitation, include item A, or may include item A and item B. This example may also include item A, item B, and item C, or item B and item C. In other examples, "at least one of" may, without limitation, include, e.g., two of item A, one of item B, and ten of item C; four of item B and seven of item C; and other suitable combinations.

[0021] Referring to FIGS. 2A to 4B, in the present disclosure, one or more wavelength selective switches (WSSs) are used in combination with one or more optical amplifiers (OAs) to provide sharper filtering of optical signals. WSS’ are well known in the art as made clear by U.S. Pat. No. 10,461,878, U.S. Pat. No. 8,867,917, U.S. Pat. No. 7,397,980, and U.S. Pat. No. 7,092,599, each of these patents being incorporated herein by reference in its entirety. Thus, for the purposes of brevity, details regarding the configuration and / or internal operation of each WSS disclosed herein will only be described as necessary to understand the present disclosure.

[0022] As will be understood by those skilled in the art, each WSS disclosed in the present disclosure may be programmed, operated, and / or configured to control the optical signals passing therethrough using the same filter pattern or filtering function for each optical signal passing therethrough. In one example, this filter pattern or filtering function may include controlling (1) only the amplitude of the optical signal passing through the WSS each time, (2) only the phase of the optical signal passing through the WSS each time, or (3) both the amplitude and phase of the optical signal passing through the WSS each time.

[0023] In the example shown in Figures 4A and 4B, the first WSS (WSS1) may, in one example, be programmed, operated, and / or configured to control both the phase and amplitude of the optical signal passing through it, and the optical signal may be received from an optical signal source. The optical signal may pass through WSS1 multiple times, and between each pass, WSS1 may control the phase and amplitude of the optical signal, for example, using the same filter pattern or filtering function. However, this should not be interpreted as limiting, as it is assumed that WSS1 may be programmed, operated, and / or configured to control only the phase or only the amplitude from each pass of the optical signal through WSS1, using the same filter pattern or filtering function. Multiple passes of the optical signal through WSS1 can be combined with, for example, amplification by OA between sets of passes through WSS1 to minimize the effect of crosstalk on the optical signal. After passing through WSS1 multiple times, the optical signal may be provided to a second WSS (WSS2), which may be programmed, operate, and / or configured to control the phase and / or amplitude of the optical signal. The optical signal then passes through WSS2 multiple times to remove artifacts created by any phase control applied to the optical signal by passing it through WSS1 multiple times. In a specific example, WSS2 may be programmed, operate, and / or configured to control only the amplitude of the optical signal while the optical signal passes through WSS2, using the same filter pattern or filtering function. Multiple passes of the optical signal to WSS2 can minimize the effect of crosstalk to the optical signal, for example, by amplification by OA during a set of passes to WSS1. After multiple passes of the optical signal to WSS2, the optical signal may be provided to a suitable and / or desired optical receiving device for further processing and / or manipulation.

[0024] In one example, each WSS may be programmed, operate, and / or configured to generate an output optical signal having a programmable optical spectrum from a broadband optical signal input to the WSS, the programmable optical spectrum having a programmable intensity, for example, between wavelengths of 1520 to 1610 nm (within the near-infrared spectrum), with each wavelength having a magnitude of several orders of magnitude (e.g., approximately 4).

[0025] As is known in the art, a WSS may have several programmable inputs / outputs (I / O), each of which comprises an optical fiber for the propagation of optical signals, for example, incoming to or outgoing from the WSS. In one example, each I / O of the WSS may be independently programmed, operated, and / or configured as an input for receiving incoming optical signals for subsequent processing by the WSS (e.g., filtering). Alternatively, each I / O may be independently programmed, operated, and / or configured as an output for outputting optical signals after processing by the WSS. In the exemplary WSS' shown in Figures 2A to 4B, each WSS has four I / Os 20-1 to 20-4 programmed, operated, and / or configured as optical inputs, and four I / Os 22-1 to 22-4 programmed, operated, and / or configured as optical outputs.

[0026] Referring to Figures 2A to 4B, in one example, the optical signal input to I / O20-1 of the WSS may be output via I / O22-1 of the WSS after "passing through 1" to the WSS and processing by the WSS (including WSS1 and WSS2 shown in Figures 4A to 4B) (in other words, phase and / or amplification control). The optical signal output via I / O22-1 of the WSS is then input to I / O20-2 of the WSS for processing by the WSS, and then output via I / O22-2 of the WSS after "passing through 2" to the WSS.

[0027] The optical signal output via WSS I / O22-2 is then input to WSS I / O20-3 for processing by WSS, and after a "pass-through 3" to WSS, it may be output via WSS I / O22-3. Next, the optical signal output via WSS I / O22-3 may be optionally input to WSS I / O20-4 for processing by WSS, and after an optional "pass-through 4" to WSS, it may be output via WSS I / O22-4.

[0028] In the example shown in Figures 2A to 2B, the optical signal input to I / O 20-1 of the WSS may be received from an optical signal source 24, and after passing through WSS 1 to 4, the optical signal output via I / O 22-4 of the WSS may be provided to an optical amplifier 28 for amplification and then to a suitable and / or desired optical receiving device 26. In this example, the WSS may be programmed, operate, and / or configured to control the phase and / or amplitude, preferably both phase and amplitude, of the optical signal using the same filter pattern or filtering function each time the optical signal passes through the WSS. In the example shown in Figures 3A to 3B, the optical signal input to I / O 20-1 of the WSS may be received from an optical signal source 24, and after passing through WSS 1 and 2, the optical signal output via I / O 22-2 of the WSS may be provided to an optical amplifier 28 for amplification and then to I / O 20-3 of the WSS for passing through WSS 3 to 4. After passing through the WSS 4, the optical signal output via the WSS's I / O 22-4 may be provided to a preferred and / or desired optical receiving device 26. In this example, the WSS may be programmed, operate, and / or configured to control the phase and / or amplitude, preferably both, of the optical signal using the same filter pattern or filtering function each time the optical signal passes through the WSS.

[0029] In the example shown in Figures 4A and 4B, the optical signal input to I / O 20-1 of WSS1 may be received from the optical signal source 24. After passing through WSS1 1 and 2, the optical signal may be output to the first optical amplifier 28-1 via I / O 22-2 of WSS1. After amplification by the first optical amplifier 28-1, the optical signal may be input to I / O 20-3 of WSS1 for passing through WSS1 3 and 4. In this example, WSS1 may be programmed, operate, and / or configured to control the phase and / or amplitude, preferably both phase and amplitude, of the optical signal using the same filter pattern or filtering function each time the optical signal passes through WSS1. After passing through WSS1 4, the optical signal output via I / O 22-4 of WSS1 may be input to I / O 20-1 of WSS2.

[0030] After passing through WSS2 1 and 2, the optical signal may be output to a second optical amplifier 28-2 via I / O 22-2 of WSS2. After amplification by the second optical amplifier 28-2, the optical signal may be input to I / O 20-3 of WSS2 for passing through WSS2 3 and optionally passing through 4. If WSS2 is not configured to perform optional passing through 4, after passing through WSS2 3, the optical signal may be output to a preferred and / or desired optical receiving device 26 via I / O 22-3 of WSS2. Conversely, if WSS2 is configured to perform optional passing through 4, the optical signal may be output to a preferred and / or desired optical receiving device 26 via I / O 22-4 of WSS2 after passing through WSS2 4. In this example, WSS2 may be programmed, operate, and / or configured to control the phase and / or amplitude, preferably amplitude only, of the optical signal using the same filter pattern or filtering function each time the optical signal passes through WSS2.

[0031] In one example, each optical signal source 4 may be any currently known or future preferred and / or desired light source, such as an amplified spontaneous emission (ASE) broadband light source, for example, a doped fiber amplifier or a light-emitting diode. However, this should not be interpreted as limiting, as it is assumed that the optical signal source can be any preferred and / or desired broadband light source.

[0032] In one example, passing the optical signal, after amplification by the OA28 (including OA28-1 and OA28-2 shown in Figures 4A-4B), through at least one WSS (including WSS1 and WSS2 shown in Figures 4A-4B) may be desirable to remove any undesirable wavelengths of light output by the OA28; in other words, the WSS can remove light emitted by the OA at frequencies that the user or application may not want present.

[0033] In one example, each optical amplifier 28 may be any preferred and / or desired type of optical amplifier currently known or to be developed in the future, such as an erbium-doped fiber amplifier (EDFA), without limitation. However, this should not be interpreted as limiting, as it is assumed that each optical amplifier 28 could be any preferred and / or desired type of optical amplifier.

[0034] In one example, each optical receiving device 26 may be any currently known or future-developed preferred and / or desired optical receiving device, such as an optical amplifier, optical switch, optical receiver, optical transponder, optical splitting and insertion device, wavelength selective switch, optical filter, or spectral analyzer. However, this should not be interpreted as limiting, as it is assumed that the optical receiving device 26 may be any currently known or future-developed preferred and / or desired optical receiving device that can be used to process the optical signal output to the optical receiving device 26 via the WSS.

[0035] The examples shown in Figures 2A to 4B and described above are for illustrative purposes only and should not be interpreted as limiting. For example, the configuration of each WSS (including WSS1 and WSS2 shown in Figures 4A to 4B), the number of passes through each WSS, and / or the location of each optical amplifier in the optical signal path from the optical signal source 24 to the optical receiving device 26 should not be interpreted as limiting, for it is assumed that the configuration of each WSS, the number of passes through each WSS, and / or the location of each optical amplifier in the optical signal path from the optical signal source 24 to the optical receiving device 26 can be selected by a person skilled in the art to achieve a desired level or degree of optical filtering of the optical signal that is considered suitable and / or desired for a particular application.

[0036] In one example, unless expressly described herein, each WSS may be programmed, operate, and / or configured to perform the same filtering function each time an optical signal passes through the WSS. For example, each WSS (including WSS1 and WSS2) may be programmed, operate, and / or configured to perform the same filtering function each time an optical signal passes through the WSS, for example, to perform phase-only filtering, amplitude-only filtering, or both phase and amplitude filtering.

[0037] In another example, WSS1 may be programmed, operate, and / or configured to perform both phase and amplitude filtering each time an optical signal passes through it, while WSS2 may be programmed, operate, and / or configured to perform only amplitude (or only phase) filtering each time an optical signal passes through it; in other words, WSS1 and WSS2 may be programmed, operate, and / or configured to perform different filtering functions. In another example, WSS1 and WSS2 may be programmed, operate, and / or configured to perform the same filtering function, for example, only amplitude filtering, only phase filtering, or both amplitude and phase filtering.

[0038] Figures 5A and 5B show illustrative plots of broadband optical signal spectra 30, 32, and 34 that can be received at the input of the optical receiving device 26 shown in Figures 2A, 3A, and 4A, respectively. As can be seen, the broadband optical signal spectrum 34 that can be generated by the broadband optical signal filtering system in Figure 4A has sharper features or transitions 36, 38, 40, and 42 compared to the features or transitions 36', 38', 40', and 42' of the broadband optical signal spectrum 32 that can be generated by the broadband optical signal filtering system in Figure 3A (where the slope of the broadband optical signal spectrum 34 changes abruptly or suddenly). Similarly, compared to the features or transitions 36'', 38'', 40'', and 42'', of the broadband optical signal spectrum 30 that can be generated by the broadband optical signal filtering system in Figure 2A, the broadband optical signal spectrum 32 that can be generated by the broadband optical signal filtering system in Figure 3A has sharper features or transitions 36', 38', 40', and 42'.

[0039] The illustrative plots 30, 32, and 34 shown in Figures 5A and 5B are for illustrative purposes only and should not be interpreted as limiting. For example, although the bandwidths of plots 30, 32, and 34 are illustrated as being spaced apart, with plot 30 having the largest bandwidth and plot 36 having the smallest, in reality, two or more of these bandwidths may be the same or different, and / or overlap and / or intersect at various points. In another example, although the maximum gains of the illustrative plots 30, 32, and 34 are shown spaced vertically apart, in reality, two or more of these gains may be the same or different, and / or overlap and / or intersect at various points. Therefore, the illustrative plots 30, 32, and 34 shown in Figures 5A and 5B should not be interpreted as limiting.

[0040] Details on how each WSS (including WSS1 and WSS2 shown in Figures 4A-4B) can control the phase and / or amplitude of the optical signal as it passes through each are described in the paper "Dispersion Trimming in a Reconfigurable Wavelength Selective Switch" by Roelens et al., published January 1, 2008, in the Journal of Lightwave Technology, Vol. 26, No. 1, which is incorporated herein by reference in its entirety. In short, the key points of this paper include: (a) the optical signal may be attenuated in a WSS by a WSS that redirects a portion of the light in a direction different from that which it is configured to switch, for example, between internal elements of the WSS or to I / O22 of the WSS, i.e., it may experience a wavelength-dependent loss (or negative gain) referred to herein as "amplitude"; and (b) the phase of the light may also change. Under conditions that the WSS does not contain a strong phase gradient, a change in the phase of the light may not cause attenuation. However, if a strong phase gradient is present, attenuation may occur. This attenuation can be caused by misalignment of the optical signal as it propagates between the internal elements of the WSS each time the optical signal passes through it.

[0041] For this purpose, WSS can be programmed to change the phase of the optical signal, and just as the amplitude of the optical signal can be changed, the phase of the optical signal can be changed wavelength by wavelength; in other words, each wavelength can be assigned its own phase value. The phase gradient (called "group delay" in the paper) refers to how the intrinsic phase assignment at a given wavelength compares to the phase assignments of its adjacent wavelengths, and if the phases are significantly different, this will be a large gradient. Therefore, if the phase values ​​are relatively constant across all wavelengths, there is only a small gradient and only negligible attenuation. However, for wavelengths with large phase gradients, attenuation can occur at those wavelengths.

[0042] These two methods of attenuating optical signals are orthogonal, meaning that both can be performed independently by WSS. In one example, attenuation of an optical signal by WSS due to phase control (point (b) above) is thought to be "sharper" than attenuation of an optical signal by WSS due to amplitude control (point (a) above), but since phase-induced attenuation is rather a byproduct of phase control, the controllability of phase-induced attenuation is lower. Consequently, attenuation via phase control can create side lobes.

[0043] Other non-limiting examples or aspects of this disclosure are specified in the following illustrated and exemplary numbered clauses.

[0044] Clause 1: A method for filtering a broadband optical signal includes the steps of (a) outputting a broadband optical signal, (b) filtering the broadband optical signal multiple times, (c) optically amplifying the broadband optical signal, and (d) providing the filtered and amplified broadband optical signal to an optical receiving device.

[0045] Clause 2: The method according to Clause 1, wherein step (c) may include a step of optically amplifying a broadband optical signal multiple times after step (b).

[0046] Clause 3: The method according to Clause 1 or 2, wherein step (c) may include a step of optically amplifying a broadband optical signal during a set of multiple occurrences in step (b).

[0047] Clause 4: The method according to any one of Clauses 1 to 3, wherein step (b) includes a step of filtering a broadband optical signal using the same filtering function multiple times, each time.

[0048] Clause 5: The method according to any one of Clauses 1 to 4, wherein step (b) may include a step of filtering a broadband optical signal a first multiple time using the same filtering function each time, and step (c) may include a step of optically amplifying the broadband optical signal between the first multiple sets.

[0049] Clause 6: The method according to any one of Clauses 1 to 5, wherein step (b) may further include a step of filtering the broadband optical signal a second multiple time using the second filtering function each time, and step (c) may include a step of optically amplifying the broadband optical signal between the second multiple sets.

[0050] Clause 7: The method according to any one of Clauses 1 to 6, wherein the first filtering function may include phase and amplitude filtering, and the second filtering function may include amplitude filtering only.

[0051] Clause 8: The method according to any one of Clauses 1 to 7, wherein the first filtering function is performed by a first wavelength selector switch and the second filtering function is performed by a second wavelength selector switch.

[0052] Clause 9: A method for filtering a broadband optical signal includes the steps of (a) passing the broadband optical signal multiple times through a first wavelength-selective switch (WSS1), (b) amplifying the broadband optical signal during at least one set of passes of the broadband optical signal through WSS1 in step (a), (c) passing the broadband optical signal multiple times through a second wavelength-selective switch (WSS2) after steps (a) and (b), and (d) amplifying the broadband optical signal during at least one set of passes of the broadband optical signal through WSS2 in step (c).

[0053] Clause 10: The method according to Clause 9, wherein WSS1 may be programmed, operate, and / or configured to perform spectral shaping or filtering of broadband optical signals using phase and amplitude filtering, and WSS2 may be programmed, operate, and / or configured to perform spectral shaping or filtering of broadband optical signals using amplitude-only filtering.

[0054] Clause 11: The method according to Clause 9 or 10, wherein after step (d), the broadband optical signal may have the shape of a bandpass filtered signal.

[0055] Clause 12: The method according to any one of Clauses 9 to 11, further comprising step (e) of outputting a broadband optical signal to an optical receiving device after steps (c) and (d).

[0056] Clause 13: The method according to any one of Clauses 9 to 12, wherein steps (a) and (b) include a step (1) of passing a broadband optical signal through WSS1 twice, a step (2) of amplifying the broadband optical signal after step (1), and a step (3) of passing the broadband optical signal through WSS1 at least one more time after step (2).

[0057] Clause 14: The method according to any one of Clauses 9 to 13, wherein steps (c) and (d) include a step (1) of passing a broadband optical signal through the WSS2 twice, a step (2) of amplifying the broadband optical signal after step (1), and a step (3) of passing the broadband optical signal through the WSS2 at least one more time after step (2).

[0058] Clause 15: A broadband optical signal filtering system comprising a first optical amplifier and a second optical amplifier and a first wavelength-selective switch and a second wavelength-selective switch (WSS1 and WSS2) connected thereto, wherein a broadband optical signal passes through the broadband optical signal filtering system in the following order: (a) WSS1 at least once, (b) the first optical amplifier, (c) WSS1 at least one more time, (d) WSS2 at least once, (e) the second optical amplifier, and (f) WSS2 at least one more time.

[0059] Clause 16: A broadband optical signal filtering system as described in Clause 15, wherein at least one of the following is performed: WSS1 is programmed, operates, and / or configured to perform spectral shaping or filtering from each pass of a broadband optical signal to WSS1 using phase and amplitude filtering, and WSS2 is programmed, operates, and / or configured to perform spectral shaping or filtering from each pass of a broadband optical signal to WSS2 using amplitude-only filtering.

[0060] Clause 17: A broadband optical signal filtering system as described in Clause 15 or 16, wherein WSS1 can perform the same spectral shaping or filtering from each pass of a broadband optical signal to WSS1, and WSS2 can perform the same spectral shaping or filtering from each pass of a broadband optical signal to WSS2.

[0061] Clause 18: A broadband optical signal filtering system according to any one of Clauses 15 to 17, further comprising at least one of a broadband optical signal source that outputs a broadband optical signal to WSS1 before step (a), and an optical receiving device coupled to receive a broadband optical signal from WSS2 after step (f).

[0062] Clause 19: A broadband optical signal filtering system according to any one of Clauses 15 to 18, wherein step (a) includes passing a broadband optical signal through WSS1 twice, step (c) includes passing a broadband optical signal through WSS1 twice, and step (d) includes passing a broadband optical signal through WSS2 twice.

[0063] While this disclosure has been described in detail for illustrative purposes based on what is currently considered the most practical and preferred embodiments, it should be understood that such details are for that purpose only, and this disclosure is not limited to the disclosed embodiments, but rather intended to include modifications and equivalents within the spirit and scope of the appended claims. For example, it should be understood that this disclosure intends, wherever possible, to allow one or more features of any embodiment to be combined with one or more features of any other embodiment. [Explanation of Symbols]

[0064] 1. First wavelength selective switch (WSS) 2. The Second WSS 20-1 Input / Output (I / O) 20-2 I / O 20-3 I / O 20-4 I / O 22-1 I / O 22-2 I / O 22-3 I / O 22-4 I / O 24 Optical signal source 26 Optical receiving devices 28 Optical Amplifier 28-1 First Optical Amplifier 28-2 Second Optical Amplifier 30. Broadband optical signal spectra, plotted. 32. Broadband optical signal spectra, plotted. 34. Broadband optical signal spectrum, plotted. 36 Features or transitions 36' Features or transitions 36'' Feature or transition 38 Features or transitions 38' Features or transitions 38'' Feature or transition 40 Features or transitions 40' Features or transitions 40'' Feature or transition 42 Features or transitions 42' Features or transitions 42'' Feature or transition

Claims

1. A method for filtering broadband optical signals, Step (a) of outputting a broadband optical signal, (b) the step of filtering the broadband optical signal multiple times, Step (c) optically amplifying the broadband optical signal, (d) providing a filtered and amplified broadband optical signal to an optical receiving device A method that includes this.

2. The method according to claim 1, wherein step (c) includes a step of optically amplifying the broadband optical signal after the multiple times in step (b).

3. The method according to claim 1, wherein step (c) includes a step of optically amplifying the broadband optical signal during a set of multiple occurrences in step (b).

4. The method according to claim 1, wherein step (b) includes filtering the broadband optical signal using the same filtering function each of the multiple times.

5. Step (b) includes the step of filtering the broadband optical signal a first multiple time by using the first filtering function each time, Step (c) includes a step of optically amplifying the broadband optical signal during one of the first sets of multiple occurrences. The method according to claim 1.

6. Step (b) further includes the step of filtering the broadband optical signal a second multiple time by using the second filtering function each time, Step (c) includes a step of optically amplifying the broadband optical signal during a second set of multiple times, The method according to claim 5.

7. The first filtering function includes phase and amplitude filtering, The second filtering function includes filtering of amplitude only. The method according to claim 6.

8. The first filtering function is performed by a first wavelength selector switch. The second filtering function is performed by a second wavelength selector switch. The method according to claim 6.

9. A method for filtering broadband optical signals, Step (a) involves passing a broadband optical signal through a first wavelength selector switch (WSS1) multiple times, Step (a) includes, at least one set of steps in which the broadband optical signal passes through the WSS1, a step (b) of amplifying the broadband optical signal, After steps (a) and (b), step (c) is to pass the broadband optical signal through a second wavelength selector switch (WSS2) multiple times, During at least one set of the broadband optical signal passing through the WSS2 in step (c), step (d) amplifies the broadband optical signal. A method that includes this.

10. The WSS1 is programmed, operates, and / or configured to perform spectral shaping or filtering of the broadband optical signal using phase and amplitude filtering, and The WSS2 is programmed, operates, and / or configured to perform spectral shaping or filtering of the broadband optical signal using amplitude-only filtering. The method according to claim 9, wherein at least one of the following is the method according to claim 9.

11. The method according to claim 9, wherein after step (d), the broadband optical signal has the shape of a bandpass filtered signal.

12. Step (e) after steps (c) and (d), the broadband optical signal is output to an optical receiving device. The method according to claim 9, further comprising:

13. Steps (a) and (b) are, Step (1) passing the broadband optical signal through the WSS1 twice, After step (1), step (2) amplifies the broadband optical signal, After step (2), step (3) is to pass the broadband optical signal through the WSS1 at least one more time. The method according to claim 9, including the method described in claim 9.

14. Steps (c) and (d) are, Step (1) passing the broadband optical signal through the WSS2 twice, After step (1), step (2) amplifies the broadband optical signal, After step (2), step (3) is to pass the broadband optical signal through the WSS2 at least one more time. The method according to claim 13, including the method described in claim 13.

15. A broadband optical signal filtering system comprising a first optical amplifier and a second optical amplifier, and a first wavelength-selective switch and a second wavelength-selective switch (WSS1 and WSS2) connected thereto, wherein the broadband optical signal is, (a) Perform the WSS1 at least once, (b) The first optical amplifier, (c) Perform the WSS1 at least one more time, (d) Perform the WSS2 at least once, (e) The second optical amplifier, and (f) Perform the WSS2 at least one more time The signals pass through the broadband optical signal filtering system in the following order: Broadband optical signal filtering system.

16. The WSS1 is programmed, operates, and / or configured to perform spectral shaping or filtering of the broadband optical signal from its respective passage to the WSS1 using phase and amplitude filtering, and The WSS2 is programmed, operates, and / or configured to perform spectral shaping or filtering of the broadband optical signal from each of its passes to the WSS2 using amplitude-only filtering. A broadband optical signal filtering system according to claim 15, wherein at least one of the above.

17. The WSS1 performs the same spectral shaping or filtering on each of the broadband optical signals as they pass through the WSS1. The WSS2 performs the same spectral shaping or filtering on each of the broadband optical signals as they pass through the WSS2. The broadband optical signal filtering system according to claim 16.

18. A broadband optical signal source that outputs the broadband optical signal to the WSS1 before step (a), and An optical receiving device coupled to receive the broadband optical signal from the WSS2 after step (f) The broadband optical signal filtering system according to claim 15, further comprising at least one of the following.

19. Step (a) includes the broadband optical signal passing through the WSS1 twice, Step (c) includes the broadband optical signal passing through the WSS1 twice, and Step (d) includes the broadband optical signal passing through the WSS2 twice. A broadband optical signal filtering system according to claim 15, wherein at least one of the above is true.

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