Pump sharing between reflective optical amplifiers

Abstract

The invention relates to pumping sharing between reflective optical amplifiers. An optical fiber-based optical amplifier is formed to assume a reflective architecture in a particular configuration in which a single pump source is shared among a plurality of individual reflective amplifier elements. A passive, non-variable power divider is used to direct sub-beams of sufficient power into rare earth doped optical fibers contained within separate amplifiers. Due to the fact that an optical signal passes through a doped optical fiber coil (gain medium) twice due to a reflective framework, the same target output power level can be obtained by using low pumping power (compared with a conventional single-pass structure). And a single pump source is considered sufficient to provide sufficient output power to arrange and deliver sufficient pump power through the power distribution to provide amplification of the propagating optical signal in each individual amplifier.

Description

Technical Field

[0001] The present disclosure relates to doped-fiber amplifier technology and, more particularly, to pumping configurations for use in amplifier modules based on reflection amplifier designs. Public background

[0003] Rare earth doped fiber amplifiers (e.g., erbium doped fiber amplifiers (EDFAs)) can be used in applications where there are limitations in terms of physical size, electrical power, number of optical modules, optical gain fibers, etc. In these cases, a reflective EDFA is a useful design option, in which the distal end of the doped fiber coil includes a reflective element that enables the initially amplified signal to pass through the doped fiber a second time to form an amplified output signal, as opposed to using two or more gain fiber coils to produce the same level of gain in a single-pass arrangement.

[0004] In addition to reducing the physical length of doped fiber required to obtain the desired amount of amplification, it is contemplated that the reflective amplifier topology may provide additional benefits in applications where the optical noise figure (NF), a known shortcoming in reflective designs, is not a major concern. For example, optical transponders may be a suitable application for a reflective amplifier configuration because no optical-to-electrical conversion and data recovery processes are required. Overview

[0006] A reflective EDFA architecture is disclosed herein, which is suitable for use in applications where it is important to reduce factors such as physical size, electrical power consumption, number of components, cost, etc. In particular, a reflective EDFA system is proposed that shares a single pump source between multiple individual amplifiers by using a passive, non-variable power splitter (splitter) to direct sub-beams of sufficient power to separate amplifiers. Since the reflective architecture causes the optical signal to pass through the doped fiber coil (gain medium) twice, a lower pump power (compared to a conventional single-pass structure) can be used to obtain the same target output power level. Therefore, a conventional pump source is considered sufficient to provide sufficient output power to be divided into sub-beams and transmitted to each of the individual reflective amplifiers. In particular, the pump beam output from the pump source can be arranged by a passive power distribution to produce separate pump sub-beams.

[0007] It has been found that this pump-sharing configuration, combined with an appropriate length (coil) of the gain fiber (in particular, the "optical length" with respect to the absorbance of the gain dopant), alleviates to some extent the dependency between input signal wavelength (or input signal power) and pump power, thereby allowing the disclosed reflective EDFA system to operate over a limited input signal wavelength range without the need for adjustments to the pump source itself.

[0008] By using a passive optical power divider to provide a pump sub-beam to each EDFA, the resulting amplifier system can be formed as a "closed" system that does not require any further adjustments during use. Alternatively, the reflective amplifier system can be formed as a modular arrangement that can be modified by adding / removing sections of gain fiber to adjust the optical signal wavelength range over which amplification can be produced. This is a useful feature when switching between the C-band wavelength range (about 1525nm-1575nm) and the L-band wavelength range (about 1575nm-1625nm) for use.

[0009] The reflective elements included within each EDFA may take the form of a fiber Bragg grating (or other wavelength selective device) configured to reflect wavelengths (both signal and pump beams) within a defined band, ideally absorbing any type of noise (including amplified spontaneous emission (ASE)) generated during the amplification process. Each reflective amplifier may utilize a combination of an optical circulator and a wavelength division multiplexer (WDM) to guide the propagation of the optical signal (before and after amplification) and the pump beamlets in an efficient manner with a minimum number of components. In practice, these elements may be combined into a single hybrid component, which further reduces the overall size of the reflective amplifier. A bidirectional optical tap may be included as an in-line element to monitor the amount of gain generated during amplification without unduly expanding the size or complexity of the system.

[0010] Exemplary embodiments of the present disclosure may take the form of a fiber-based optical amplifier module comprising a plurality of individual reflective optical amplifier elements, N in number, wherein a passive optical power divider is used to provide an individual pump sub-beam to each amplifier element. In particular, each individual reflective optical amplifier element is formed to include a rare earth-doped fiber coil (having a proximal terminal and a distal terminal) and an optical coupler disposed at the proximal terminal of the rare earth-doped fiber coil. The optical coupler receives a known wavelength λ S The optical signal and the pump wavelength λ P The pump beam is used as an independent input, and the pump wavelength λ PThe optical coupler is configured to inject both the optical signal and the pump beam into the rare earth doped fiber coil to initiate amplification. Each reflective amplifier element further includes a reflective element disposed outside of a distal end terminal of the rare earth doped fiber coil, wherein the reflective element is configured to redirect the optical signal so that the optical signal passes through the rare earth doped fiber coil again to exit the distal end terminal as an amplified output signal.

[0011] In some examples, the optical amplifier assembly may include a fiber-based optical amplifier module as described above as a "closed" self-contained arrangement, where an external pump source is used to direct an incident pump beam to a passive power divider. Thus, the module is considered self-contained because no electrical components need to be included in the module, only passive optical devices are required, thereby reducing size.

[0012] Other and further embodiments of the present disclosure may become apparent during the course of the following discussion and by reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Referring now to the drawings, wherein like numerals represent like elements throughout the several views:

[0015] Figure 1 is a general block diagram of a reflective optical amplifier architecture;

[0016] Figure 2 An example of pump sharing between a pair of reflective EDFAs is shown;

[0017] Figure 3 Another example of pump sharing in a reflective amplifier arrangement is shown, in this case a single pump is shared between a set of four individual EDFAs;

[0018] Figure 4 yes Figure 3 A slightly simplified view of an example of a self-contained configuration of optical elements within a module, wherein an external source is used to provide the required pump beam;

[0019] Figure 5 An alternative pump-sharing amplifier arrangement is shown, in which case an unequal power split ratio is used to provide optimal pump energy to a C-band reflective amplifier that shares a pump source with an L-band reflective amplifier;

[0020] Figure 6 An example reflective EDFA is shown, including additional passive elements that may be incorporated as desired for certain applications; and

[0021] Figure 7A reconfigurable reflective amplifier formed according to the disclosed principles is shown. Detailed Description

[0023] Figure 1 1 is a general block diagram for understanding the pump sharing principle of the disclosed reflective amplifier system. The pump sharing reflective optical amplifier module 10 is shown to include a plurality of individual reflective fiber amplifier elements 201-20 N Each reflective fiber amplifier element 20 i is shown in response to an input optical signal IN i , and generates an amplified version as the associated output signal OUT i As particularly shown in the following figures, the inclusion of a reflective element at the terminal end of the doped fiber coil within the amplifier allows the optical signal IN i Passing back and forth through the doped fiber, experiencing amplification in each direction, the "double-pass" of the optical signal through the doped fiber means that less pump power is required to achieve the same level of optical gain as obtained with a conventional single-pass amplifier design using the same length of doped fiber.

[0024] Figure 1 Also shown is the pump beam P, which has a known wavelength λ P When erbium is used as a dopant in an amplifying fiber, a wavelength of about 980 nm can be used. P A pump beam P operating at a certain frequency is used to promote amplification of optical wavelengths (e.g., C-band or L-band) commonly used in communication systems. Typical laser sources are capable of producing pump beams P with output powers on the order of hundreds of mW; in the reflective EDFA amplifiers used in the disclosed system, lower powers on the order of tens of mW have been found to be sufficient to produce target levels of gain for the output signal. Therefore, in accordance with the principles of the present disclosure, a passive power splitter 30 is included within the reflective amplifier module 10 and is used to generate a set of lower power pump sub-beams from the original pump beam P, thereby providing a compact and cost-reduced multi-amplifier assembly.

[0025] The power divider 30 is Figure 1 , which is depicted as a 1:N power splitter, which generates a number N of multiple pump sub-beams, which are applied as inputs to each reflective amplifier 20 (sometimes referred to as a "reflective EDFA 20" hereinafter). Figure 1Specifically, the pump beam P1 is applied as input to the reflective EDFA 201, the pump beam P2 is applied as input to the reflective EDFA 202, and so on. N As input is applied to the reflective EDFA 20 N In this example, the power divider 30 is configured as a 1:N ratio power divider so that each sub-beam presents approximately the same power fraction; other arrangements may use other power division ratios. As described above, the reflective EDFA arrangement allows relatively low levels of pump power to be sufficient to achieve the target amplification level, and therefore allows a pump source of conventional power levels to be distributed among the various amplifier elements.

[0026] It has been found that a reflective EDFA that uses a relatively low power pump to produce amplification exhibits minimal dependence on its input conditions (i.e., input signal wavelength and / or input signal power). Thus, in the disclosed pump sharing arrangement, each individual amplifier is able to achieve the same target output signal power by using an equal power share of the input pump power, even when the input signals to the individual amplifiers use different wavelengths and exhibit somewhat different signal powers.

[0027] The use of different input wavelengths Figure 1 The reflective amplifier module 10 is particularly shown, which shows that the module 10 receives a plurality of independent input signals IN1-IN N , each input signal is at a (possibly different) wavelength λ1-λ within a defined signal band used by a specific application N In an example arrangement, the individual wavelengths may be provided by a single source, such as a parametric frequency comb or other type of optical device known in the art for generating multiple individual wavelengths useful in a multi-wavelength communication system.

[0028] As described above, the reflective amplifier module 10 can be configured as a C-band amplifier (accepting wavelengths across the wavelength band λ C The input signal has a wavelength band λ C extending between about 1525nm-1575nm) or L-band amplifiers (a wavelength band λ extending between about 1575nm-1625nm) L ), or any other suitable band amplifier that can be used for optical communication purposes. Although each individual EDFA element 20 i It can operate within a limited wavelength range, but is considered a "single-channel" amplifier; that is, the input is applied to a given reflective EDFA 20 i The optical signal is a single wavelength input signal (as opposed to a multi-wavelength input).

[0029] Figure 2 A specific example embodiment of a reflective amplifier module 10 utilizing pump sharing in accordance with the principles of the present disclosure is shown. In this example, the reflective amplifier module 10 includes a pair of separate reflective EDFAs 201, 202. A pair of separate input optical signals IN1, IN2 are introduced to the module 10, and the reflective EDFAs 201, 202 are used to generate a pair of amplified output signals OUT1, OUT2. Again, while each of these inputs is defined as a "single channel" input (i.e., operating at a specific signal wavelength), the specific wavelengths selected for use by the separate reflective EDFAs can be any desired value within the defined bandwidth utilized by the system including the reflective amplifier module 10. For example, the reflective amplifier module 10 can be configured as a C-band amplifier, where the input wavelength λ S Anywhere within the wavelength range of about 1525nm to 1575nm. In another example, the amplifier module 10 can be configured for use with L-band signals operating within the wavelength range of about 1575nm-1625nm. These are just two examples, and any other reasonable optical signal operating range can also be used.

[0030] continue Figure 2 , a first input signal IN1 is shown as being applied as an input to a first reflective EDFA 201, and a second input signal IN2 is applied as an input to a second reflective EDFA 202. Each EDFA 20 includes a section of an erbium doped fiber (EDF) 22 for increasing the optical power of the propagating input signal in the presence of an applied pump sub-beam (P1 or P2). Each EDFA 20 is shown as including a WDM 24 disposed at the input end of the EDF 22 and configured to transmit a WDM signal at a wavelength λ to the optical fiber 22. P The pump sub-beam operating at wavelength λ1 or λ2 (as the case may be) is multiplexed onto a common signal path input of its associated EDF 22 with an optical signal operating at wavelength λ1 or λ2 (as the case may be).

[0031] According to the principles of the present disclosure, the reflective design of EDFA 20 allows the use of lower pump power levels (compared to a single-pass configuration) to provide a target output power level, regardless of the specific wavelength of the input signal (within the limited range used in the amplifier) ​​and / or the power level of the specific input signal. Therefore, EDFA module 10 is able to share a single pump source (providing an output pump beam with a typical power) between EDFA 201 and 202. To achieve this, Figure 2A single pump P is shown for delivering pump energy to both reflective EDFA 201 and reflective EDFA 202. In this particular example, at wavelength λ P The pump beam P operated at is provided as an input to the reflective amplifier module 10 (or alternatively, is included in the module 10). Figure 1 As shown and discussed, a passive power splitter 30 is included within the amplifier module 10. In this example, a 1:2 ratio passive power splitter 30 (sometimes also referred to as a 50 / 50 passive power splitter) is used to split an incident pump beam P into sub-beams having substantially equal power, wherein a first pump sub-beam P1 is applied as input to WDM 241 and a second sub-beam P2 is applied as input to WDM 242.

[0032] With particular reference to the first reflective EDFA 201 (it should be understood that EDFA 202 includes the same elements and operates in the same manner), the pump beamlet P1 interacts with the rare earth dopant (Er) within the EDF 221 in a manner that causes an optical power gain of the input signal IN1 (operating at a known wavelength λ1). The initially amplified form of IN1 exits the EDF 221 and strikes a reflective element 261 disposed outside the distal end of the EDF 221. As indicated by the curved arrows, the reflective element 261 serves to redirect the initially amplified signal IN1 so that it passes through the EDF 221 a second time and is further amplified due to the continued presence of the pump beamlet P within the EDF 221. In some examples, the reflective element 26 may take the form of a wavelength selective filter (e.g., a fiber Bragg grating) that is configured to reflect signals within a limited wavelength band of the system. An input isolator 11 and an output isolator 13 are also shown as components within each reflective EDFA 20, where these elements are typically included in the fiber amplifier structure to prevent reflections from interfering with the operation of the amplifier.

[0033] As described above, since amplification occurs as the input signal passes through the EDF 221 in each direction, an acceptable amount of gain can be generated in the presence of a relatively low power pump beam (e.g., on the order of tens of mW). The twice amplified version of IN1 that leaves the EDF 221 in the opposite direction is defined as the amplifier output signal OUT1 of the reflective EDFA 201. The amplified output signal OUT1 is Figure 2 It is shown in FIG. 1 as passing through WDM 241 for the second time before leaving the reflective amplifier module 10 .

[0034] In such Figure 2In the illustrated embodiment, each reflective EDFA 20 further includes an optical circulator 28 implemented as part of a reflective architecture to control the propagation direction of various signals and ensure that the amplified output signals are directed out of the reflective amplifier module 10. As shown with respect to the reflective EDF 221, the optical circulator 281 is disposed before the input end of the WDM 241 to receive the input signal IN1 (at the input port 1 of the circulator 281). The input signal IN1 propagates along a defined path within the circulator 281 and exits at the bidirectional port 2 of the optical circulator 281. The bidirectional port 2 of the optical circulator 281 is connected to the optical circulator 281. Figure 2 2 is shown as being coupled to the input end of WDM 241, thereby directing the incident optical signal to EDF 221. Thereafter, the input signal IN1 proceeds in the above-described manner to pass through EDF 221 for the first time, and then is redirected to pass through EDF 221 for the second time after being redirected by reflective element 261.

[0035] The amplified optical signal (i.e., amplified output signal OUT1) exiting after the second pass through EDF 221 will then propagate through WDM 241 and thereafter be directed into bidirectional port 2 of optical circulator 281. Amplified output signal OUT1 will continue to propagate through optical circulator 281, exiting at output port 3. Figure 2 As shown, the output port 3 of the optical circulator 281 becomes one of the output optical ports of the amplifier module 10 .

[0036] Therefore, in Figure 2 In the configuration shown, an externally applied pump beam P can be shared between a pair of reflective EDFAs 201 and 202 by using a passive power splitter, thereby reducing the number of components and the need for a separate pump source compared to some prior art arrangements.

[0037] Figure 3 Another embodiment of a shared pump reflective EDFA module of the present disclosure is shown, where in this case, the reflective amplifier module 40 includes multiple individual reflective EDFA elements that share a single pump source. Here, a set of four reflective EDFAs 201-204 are used to (respectively) amplify a set of four input signals IN1-IN4 and generate a set of four amplified output signals OUT1-OUT4. In this illustration, each input signal is shown as operating at a different wavelength (depicted as λ1-λ4) within the known operating range of the reflective amplifier module 40. For example, all operating wavelengths can be within the C-band range of approximately 1525nm-1575nm. This is just an example; in practice, there may be application scenarios where the same wavelength can be used by multiple EDFAs 20, such as when communications are then directed along different fiber spans to different receiver destinations.

[0038] In accordance with the principles of the present disclosure, a single pump source 42 is used in this example to provide a sub-beam with sufficient power to operate all four reflective EDFA elements 201-204. The pump source 42 generates a pump wavelength λ P A pump beam P (and appropriate input power) of a wavelength known to induce gain within the doped fiber of the reflective EDFA 20 is applied as an input to the reflective amplifier module 40. Advantageously, the implementation of the pump source 42 as an external component (external with respect to the boundaries of the module 40) further simplifies the assembly of the module 40 by not requiring the use of any electrical drive signals within the module 40 itself (such as those necessary to operate the pump source 42).

[0039] The reflective amplifier module 40 is shown to include a passive power distribution arrangement 44 configured to generate a set of four pump sub-beams having substantially equal power from an applied input pump beam P. In this particular arrangement of the reflective amplifier module 40, the passive power distribution arrangement 44 includes a first power divider 46.1 that receives the incident pump beam P and generates a pair of sub-beams having equal power (shown as P / 2 for illustrative purposes). That is, a conventional 50 / 50 divider is used to provide this initial distribution of pump power. Thereafter, each half-power sub-beam output from the first power divider 46.1 is applied as input to another 50 / 50 power divider, wherein the first half-power sub-beam is applied as input to the second power divider 46.1, and the remaining second half-power sub-beam is applied as input to the third power divider 46.3. A pair of outputs from the second 50 / 50 power divider 46.2 each present approximately one quarter of the input pump power (shown as P / 4), wherein a first quarter-power sub-beam P1 is applied as pump input to the first reflective EDFA 201, and a second quarter-power sub-beam P2 is applied as pump input to the second reflective EDFA 202. In a similar manner, the third power divider 46.3 provides a third quarter-power pump sub-beam P3 and a fourth quarter-power pump sub-beam P4 which are applied to the reflective EDFAs 203 and 204, respectively.

[0040] Thus, in accordance with the principles of the present disclosure, the ability to share a single pump source among multiple separate reflective EDFAs using a passive power distribution arrangement in this manner is believed to significantly reduce the component count, size, and complexity of such an amplifier system (which would otherwise utilize a separate pump source for each amplifier, with a separate electrical drive signal required to excite each pump).

[0041] Figure 4 The illustration of again depicts the reflective amplifier module 40, which is presented in a manner that emphasizes the closed, self-contained configuration that can be produced by means of pump sharing between reflective EDFAs. Specifically shown here are a plurality of input optical ports 400, numbered N, for receiving a plurality of incident optical signals. In an exemplary embodiment, the input signals can propagate along a plurality of optical fibers (fiber arrays) coupled to the input ports 400 in a one-to-one arrangement. A plurality of optical signal ports 410, numbered N, are shown as also formed on the exterior of the module 40, with a plurality of output signal paths (which may also be fiber arrays) coupled to the output ports 410. Finally, the pump signal P is shown as entering the reflective module 40 via a pump inlet port 425 (again, possibly propagating along an optical fiber coupled to that port).

[0042] As described above, the pump source 42 is preferably located outside the collection of passive optical devices that form the reflective amplifier module 40 . Figure 4 Also shown is an input drive current source 430 for exciting the pump source 42 and generating a pump beam P as an output. Thus, it is contemplated that a reflective fiber amplifier module formed in accordance with the present disclosure may be implemented as a "closed" module, wherein a pump beam and an optical signal are applied to the module as inputs, and an amplified output signal leaves the module. There is no need to include a pump source within the amplifier module itself, further reducing the cost and complexity of the design and forming a truly "pluggable" optical amplifier with no internal electronics, or other similar compact configurations suitable for specific applications (e.g., "linear drivers" proposed for coherent communication systems).

[0043] like Figure 2 and Figure 3 As shown in the embodiment of , each reflective EDFA amplifier element 20 can respond to input signals operating at different wavelengths (however, all are "single channel" amplifiers) and possibly different input powers, and still share a common pump source. In implementation, pump power is passively and non-variably distributed to these multiple EDFAs.

[0044] Figure 5 Shows Figure 2 An alternative configuration of a pump-sharing reflective amplifier module 10 is provided. In this particular alternative configuration, each individual reflective EDFA element is specifically configured to amplify an optical input signal operating in a different wavelength band, but is still able to share a single pump source. For illustration purposes, Figure 5 The arrangement is represented as a reflective amplifier module 10 CL , wherein the first reflective EDFA element 20 CThe second reflective EDFA element 20 is configured to amplify the C-band optical input signal and L The device is configured to amplify an L-band optical input signal.

[0045] As will be appreciated by those skilled in the art, one requirement for obtaining amplification in the longer wavelength range of an L-band input signal is the need to use a longer length of gain fiber in order to provide sufficient interaction material to allow the longer wavelength signal to be adequately amplified. Figure 5 , C-band reflective EDFA element 20 C is shown as including an EDF 22 having a first length L1 C , and L-band reflective EDFA components 20 L is shown to include an EDF 22 having a second length L2 L , where L2>L1.

[0046] Advantageously, a single pump source can still be used again to supply power to the EDFA element 20. C and EDFA element 20 L Both provide pump beamlets with sufficient power. However, in this example, a different passive distribution of the pump power is necessary so that both C-band and L-band signals can be amplified. Figure 5 , reflective amplifier module 10 CL is shown to include a passive power divider 50 configured to have a power ratio selected such that a greater portion of the pump power is directed to the EDFA 20. L In order to amplify the L-band optical signal. Figure 5 is depicted as the output of k% of the pump power (denoted as P k ) provided to WDM 24 C and the output of (100-k)% of the pump power (P (100-k) ) provided to WDM 24 L (where k<50). Thus, as shown in this example, embodiments of the disclosed pump-sharing reflective amplifier arrangement can be configured to use a pump power splitter that produces unequal power shares.

[0047] It should be understood that in order to implement this type of reflective EDFA module with a shared pump source, the optical length of the doped fiber coil (i.e., the absorption efficiency of the gain fiber) is a parameter that needs to be evaluated; in other words, the ability to use a low-power pump with a condition-independent input signal is related to the performance of the gain coil. Regardless of the input power or input signal wavelength, each amplifier can use the same total amount of pump power to obtain the target output signal power. This allows the pump power to be passively and non-variably distributed to these multiple EDFAs. The C-band version and the L-band version of the disclosed reflective amplifier arrangement can each be formed to operate with a condition-independent pump power, and therefore these can also be tuned so that the C-band version and the L-band version require the same pump power to achieve a given output signal power.

[0048] As described above, in applications such as optical transponders, where the disclosed arrangement is used as a boosted amplifier, optical NF is not a significant issue and reflective topologies can be used for the amplifier in the manner disclosed above. The reduction in required pump power reduces the need for tight control of input signal wavelength / power relative to pump characteristics, resulting in an amplifier in an optical transponder that is substantially independent of input signal conditions (e.g., wavelength, power) and can be used to operate over a known wavelength range. Thus, as long as the characteristics of the gain medium (here, EDF 22) can be controlled and the length of the medium is appropriately sized, a passive power divider can be used in combination with a low power pump source to deliver a sub-beam to each EDFA element and provide a sufficient amount of gain at a fixed pump power, regardless of the input signal wavelength and / or power.

[0049] Although not explicitly shown in these examples, it should be understood that the various reflective amplifier elements may include additional components useful in specific amplification applications. For example, a gain flattening filter (GFF) may be included within the reflective EDFA to reduce the amount of ASE generated when the input signal passes through the EDF (reducing out-of-band / global OSNR) as well as to ensure that the target output power level is maintained regardless of the specific optical input signal wavelength. Figure 6 A reflective EDFA element 60 is shown including a GFF 62 that is located proximate to the reflective element 26. For example, if the reflective EDFA element 60 is configured for use as a C-band amplifier, the ability to position the GFF 62 between the EDF 22 and the reflective element 26 minimizes the impact of the flattening function on the output signal, as compared to conventional prior art single-pass EDFAs where the GFF is typically located immediately before the output port of the device.

[0050] Figure 6Also shown is an optical splitter 64, which may be included to measure input and output power levels to monitor the gain achieved by each amplifier element. Figure 6 The particular configuration shown takes the form of a bidirectional, inline split monitor, an example of which is described in co-pending U.S. patent application Ser. No. 18 / 121,641, filed on March 15, 2023, and entitled “Bidirectional Optical PowerMonitor,” which describes a relatively compact type of optical splitter that also does not require a significant increase in the overall size of the amplifier module.

[0051] The relatively compact arrangement of components in the disclosed reflective amplifier design may also allow a single reflective EDFA to be not only "pluggable" (as discussed above with respect to Figure 4 discussed), but also easy to modify, such as Figure 7 As shown (which shows a modular type reflective EDFA 70). Specifically, Figure 7 FIG. 1 in FIG. 1 shows an example reflective EDFA 70C formed to provide amplification of an input optical signal within a first wavelength range (e.g., a C-band amplifier). In addition to the elements associated with the reflective EDFA 20 described above, the reflective EDFA 70C is shown to include an EDFA 22 disposed within the first wavelength range. C and reflector 26 C Internal connector elements 72 therebetween.

[0052] According to this aspect of the present disclosure, when it is desired to use the reflective EDFA 70 as an L-band amplifier, as shown in FIG. Figure 7 As shown in FIG. II, the internal connector element 72 can allow the reflective element 26 to be removed. C .like Figure 7 As shown in FIG. III, the separate L-band element 74 can then be coupled to the internal connector element 72. The L-band element 74 is shown as including the EDF 22 L The additional section, and the reflective element 26 L (It may be specifically configured for redirection of L-band signals). Figure 7 Diagram IV in shows the result of the reconfiguration, the reflective EDFA 70L, which is now able to amplify L-band optical signals.

[0053] It should be understood that the described features, structures, or characteristics of the disclosed reflective amplifier system may be combined in any suitable manner in one or more embodiments illustrating various aspects of the present disclosure. Those skilled in the relevant art will recognize that the principles of the present disclosure may be implemented without one or more of the specific details, or using other methods, components, etc. Therefore, although the foregoing examples are considered to be illustrative of the disclosed principles, it is obvious to those skilled in the art that a large number of modifications may be made to the form, usage, and implementation details without exercising creative ability and without departing from the principles and concepts presented in the present disclosure. Therefore, the subject matter of the present disclosure is not intended to be limited, except as set forth in the claims.

[0054] This application provides the following:

[0055] Item 1): An optical fiber-based optical amplifier module, comprising:

[0056] A plurality of individual reflective optical amplifier elements, N in number, each individual reflective optical amplifier element comprising:

[0057] a rare earth-doped optical fiber coil having a proximal terminal and a distal terminal;

[0058] An optical coupler is provided at the proximal end of the rare earth-doped optical fiber coil, and receives a light beam at a known wavelength λ S The optical signal is operated at the pump wavelength λ P The pump beam is operated as an independent input, the pump wavelength λ P is selected to cause amplification of the optical signal in the presence of a rare earth dopant, the optical coupler being configured to inject both the optical signal and the pump beam into the rare earth doped fiber coil to initiate amplification; and

[0059] a reflective element disposed outside the distal end of the rare earth-doped optical fiber coil, the reflective element being configured to redirect the optical signal so that the optical signal passes through the rare earth-doped optical fiber coil again and leaves the distal end as an amplified output signal; and

[0060] A passive optical power divider responsive to an incident pump beam, the passive optical power divider being configured to split the incident pump beam into a plurality of N individual pump sub-beams, each sub-beam being provided as a pump input to an optical coupler of a different one of the N plurality of individual reflective optical amplifier elements.

[0061] Item 2): The fiber-based optical amplifier module according to item 1), wherein the optical coupler of each individual reflective optical amplifier element comprises a wavelength division multiplexer.

[0062] Item 3): The fiber-based optical amplifier module according to Item 1), wherein the passive optical power divider is configured to generate a plurality of sub-beams N in number having substantially equal optical power.

[0063] Item 4): The fiber-based optical amplifier module according to item 3), wherein the passive optical power divider comprises a multi-stage arrangement of 50 / 50 power dividers.

[0064] Item 5): A fiber-based optical amplifier module according to Item 1), wherein the passive optical power divider is configured to generate a plurality of sub-beams N having individual power levels selected according to the length of the rare-earth-doped optical fiber coil.

[0065] Item 6): The fiber-based optical amplifier module according to item 5), wherein N=2, and the plurality of individual reflective optical amplifier elements of number N comprises:

[0066] a first reflective optical amplifier element configured to provide amplification of a C-band input signal using a rare earth doped optical fiber coil of length L1; and

[0067] a second reflective optical amplifier element configured to provide amplification of an L-band input signal using a rare earth doped optical fiber coil of length L2, wherein:

[0068] The passive optical power splitter is configured to direct k% of the pump beam input power to the first reflective optical amplifier element and to direct (100-k)% of the pump beam input power to the second reflective optical amplifier element, where k<50.

[0069] Item 7): An optical fiber-based optical amplifier module according to Item 1), wherein each individual reflective optical amplifier element further comprises an optical circulator disposed at the input end of the optical coupler, the optical circulator comprising: an input port for receiving an applied optical input signal, a bidirectional port coupled to the optical coupler, and an output port for guiding the amplified output signal along an output signal path of the optical fiber-based optical amplifier module.

[0070] Item 8): An optical amplifier component that responds to a plurality of optical input signals of number N and generates a plurality of optical output signals of number N from the plurality of optical input signals of number N, the optical amplifier component comprising:

[0071] Fiber-based optical amplifier modules, including:

[0072] A plurality of individual reflective optical amplifier elements, N in number, each of which is

[0073] The package includes:

[0074] a rare earth-doped optical fiber coil having a proximal terminal and a distal terminal;

[0075] An optical coupler is provided at the proximal end of the rare earth-doped optical fiber coil, and receives a light beam at a known wavelength λ S The optical signal is operated at the pump wavelength λ P The pump beam is operated as an independent input, the pump wavelength λ P is selected to cause amplification of the optical signal in the presence of a rare earth dopant, the optical coupler being configured to inject both the optical signal and the pump beam into the rare earth doped fiber coil to initiate amplification; and

[0076] a reflective element disposed outside the distal end of the rare earth-doped optical fiber coil, the reflective element being configured to redirect the optical signal so that the optical signal passes through the rare earth-doped optical fiber coil again and leaves the distal end as an amplified output signal; and

[0077] a passive optical power divider responsive to a pump input beam, the passive optical power divider being configured to divide the pump input beam into a plurality of N individual pump sub-beams, each sub-beam being provided as a pump input to an optical coupler of a different one of the N plurality of individual reflective optical amplifier elements;

[0078] A pump source is located outside the fiber-based optical amplifier module, and provides the pump input beam to the passive optical power divider.

[0079] Item 9): An optical amplifier assembly according to item 8), wherein the fiber-based optical amplifier module is configured as a closed, self-contained component having only optical signal inputs and outputs.

[0080] Item 10): An optical amplifier assembly according to Item 8), wherein one or more of the individual reflective optical amplifier elements is modular in form, allowing the insertion of additional rare earth-doped optical fiber coils to modify the operating range over which amplification is performed.

Claims

1. An optical fiber-based optical amplifier module, comprising: A plurality of individual reflective optical amplifier elements, N in number, each individual reflective optical amplifier element comprising: a rare earth-doped optical fiber coil having a proximal terminal and a distal terminal; An optical coupler is provided at the proximal end of the rare earth-doped optical fiber coil, and receives a light beam at a known wavelength λ S The optical signal is operated at the pump wavelength λ P The pump beam is operated as an independent input, the pump wavelength λ P is selected to cause amplification of the optical signal in the presence of a rare earth dopant, the optical coupler being configured to inject both the optical signal and the pump beam into the rare earth doped fiber coil to initiate amplification; and a reflective element disposed outside the distal end of the rare earth-doped optical fiber coil, the reflective element being configured to redirect the optical signal so that the optical signal passes through the rare earth-doped optical fiber coil again and leaves the distal end as an amplified output signal; and A passive optical power divider responsive to an incident pump beam, the passive optical power divider being configured to split the incident pump beam into a plurality of N individual pump sub-beams, each sub-beam being provided as a pump input to an optical coupler of a different one of the N plurality of individual reflective optical amplifier elements.

2. The fiber-based optical amplifier module of claim 1, wherein: The optical coupler of each individual reflective optical amplifier element comprises a wavelength division multiplexer.

3. The fiber-based optical amplifier module of claim 1 , wherein: The passive optical power divider is configured to generate a plurality of sub-beams, N in number, having substantially equal optical power.

4. The fiber-based optical amplifier module of claim 3, wherein: The passive optical power splitter comprises a multi-stage arrangement of 50 / 50 power splitters.

5. The fiber-based optical amplifier module of claim 1, wherein: The passive optical power divider is configured to generate a plurality of sub-beams, N in number, having individual power levels selected according to the length of the rare-earth doped optical fiber coil.

6. The fiber-based optical amplifier module of claim 5, wherein: N=2, and the plurality of individual reflective optical amplifier elements, N in number, comprises: a first reflective optical amplifier element configured to provide amplification of a C-band input signal using a rare earth doped optical fiber coil of length L1; and a second reflective optical amplifier element configured to provide amplification of an L-band input signal using a rare earth doped optical fiber coil of length L2, wherein: The passive optical power splitter is configured to direct k% of the pump beam input power to the first reflective optical amplifier element and to direct (100-k)% of the pump beam input power to the second reflective optical amplifier element, where k<50.

7. The fiber-based optical amplifier module of claim 1, wherein: Each individual reflective optical amplifier element also includes an optical circulator disposed at an input end of the optical coupler, the optical circulator including an input port for receiving an applied optical input signal, a bidirectional port coupled to the optical coupler, and an output port for directing the amplified output signal along an output signal path of the fiber-based optical amplifier module.

8. An optical amplifier assembly responsive to a plurality of optical input signals of number N and generating a plurality of optical output signals of number N from the plurality of optical input signals of number N, the optical amplifier assembly comprising: Fiber-based optical amplifier modules, including: A plurality of individual reflective optical amplifier elements, N in number, each individual reflective optical amplifier element comprising: a rare earth-doped optical fiber coil having a proximal terminal and a distal terminal; An optical coupler is provided at the proximal end of the rare earth-doped optical fiber coil, and receives a light beam at a known wavelength λ S The optical signal is operated at the pump wavelength λ P The pump beam is operated as an independent input, the pump wavelength λ P is selected to cause amplification of the optical signal in the presence of a rare earth dopant, the optical coupler being configured to inject both the optical signal and the pump beam into the rare earth doped fiber coil to initiate amplification; and a reflective element disposed outside the distal end of the rare earth-doped optical fiber coil, the reflective element being configured to redirect the optical signal so that the optical signal passes through the rare earth-doped optical fiber coil again and leaves the distal end as an amplified output signal; and a passive optical power divider responsive to a pump input beam, the passive optical power divider being configured to divide the pump input beam into a plurality of N individual pump sub-beams, each sub-beam being provided as a pump input to an optical coupler of a different one of the N plurality of individual reflective optical amplifier elements; A pump source is located outside the fiber-based optical amplifier module, and provides the pump input beam to the passive optical power divider.

9. The optical amplifier assembly of claim 8, wherein: The fiber-based optical amplifier module is configured as a closed, self-contained component having only optical signal inputs and outputs.

10. The optical amplifier assembly of claim 8, wherein: One or more of the individual reflective optical amplifier elements may be modular in form, allowing for the insertion of additional rare earth doped fiber coils, thereby modifying the operating range over which amplification is performed.

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