Pulsed pumping in multi-stage optical pre-amplifier

Abstract

An optical preamplifier is optically coupled to a power amplifier. The optical preamplifier comprises a preamplification stage signal input, a preamplification stage pump input and a preamplification stage signal output. The optical preamplifier is pulsed pumped (instead of being pumped by a continuous-wave (CW) pump). The power amplifier comprises a power amplifier signal input that is optically coupled to the preamplification stage signal output.

Description

PULSED PUMPING IN MULTI-STAGE OPTICAL PRE-AMPLIFIERCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional patent application serial number 63 / 537,862, filed on 2023 -September- 12, with first-named inventor Nicholson, and having the title "Energy Extraction in Pulsed Optical Amplifiers," which is incorporated by reference as if expressly set forth herein in its entirety. This application also claims the benefit of U.S. provisional patent application serial number 63 / 669,939, filed on 2024- July-11, with first-named inventor Nicholson, and having the title "Pulse-Pumped Multistage Erbium-Doped Fiber Amplifier at Low Repetition Rates," which is also incorporated by reference as if expressly set forth herein in its entirety.BACKGROUNDFIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to optics and, more particularly, to optical amplifiers.DESCRIPTION OF RELATED ART

[0003] As is known in the art, for pumped lasers, a pump introduces energy to a lasing medium, thereby exciting atoms and resulting in a population inversion. The stored energy is available for extraction by an incoming signal. Buildup of amplified spontaneous emission (ASE) in optical power amplifiers affects the amount of energy that is available for extraction by the incoming signal.SUMMARY

[0004] The present disclosure teaches an optical amplifier system.

[0005] Briefly described, one embodiment comprises an optical preamplifier that is optically coupled to a power amplifier. The optical preamplifier comprises a preamplification stage signal input, a preamplification stage pump input and a preamplification stage signal output. The optical preamplifier is pulse pumped (instead of being pumped by a continuous-wave (CW) pump). The power amplifier comprises a poweramplifier signal input that is optically coupled to the preamplification stage signal output.

[0006] Other systems, devices, methods, features, and advantages will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure.Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

[0008] FIG. 1 is a block diagram showing one embodiment of an optical amplifier system.

[0009] FIG. 2 is a block diagram showing another embodiment of an optical amplifier system.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] For pumped lasers, a pump introduces energy to a lasing medium, thereby exciting atoms and resulting in a population inversion. The stored energy is available for extraction by an incoming signal.

[0011] Buildup of amplified spontaneous emission (ASE) in optical power amplifiers affects the amount of energy that is available for extraction by an incoming signal. In other words, during intervals between signal pulses, buildup of ASE limits stored energy that is available for extraction by the incoming signal pulses when the power amplifier is pumped with continuous-wave (CW) pumps. At low signal pulse repetition rates (meaning, a repetition rate of a signal such that a time period of pulses is greater than four times (>4x) the gain recovery time), the extracted in-pulse power drops drastically due to high gain available to the inter-pulse ASE over a duration that is longer than the signal pulse width.

[0012] Thus, conventional wisdom taught that turning off the power amplifier pumpbetween signal pulses can limit ASE buildup. However, in practice, for optical gain from population inversion, the pump pulse must precede the signal pulse by a certain duration. Consequently, the ASE buildup in that short duration cannot be prevented, even when the power amplifier pumps are pulsed. Because of that unpreventable ASE buildup, the pulse energy at the power amplifier signal output is limited.

[0013] Despite considerable work to optimize the pulse parameters of both the power amplifier pumps and the power amplifier signal, the inter-pulse power fraction cannot be reduced to desired levels. In other words, conventional wisdom in the industry taught that pulsed pumping of the power amplifier itself would enhance energy extraction at the power amplifier. However, what others in the industry failed to recognize was that residual power feeding through from an optical preamplifier to the power amplifier had significant impact on the power amplifier signal output.

[0014] Contrary to conventional wisdom, the inventors discovered that even small levels of in-band inter-pulse power feeding through from the optical preamplifier to the power amplifier could detrimentally affect the power amplifier signal output. Thus, a major unrecognized source of the problem was not the power amplifier itself but, rather, the residual inter-pulse energy that feeds through from the optical preamplifier, with that residual inter-pulse energy experiencing high gain at the power amplifier in like manner to the ASE that is generated within the power amplifier itself.

[0015] Based on this newly discovered source of the problem (namely, that the root cause of residual inter-pulse power emanates from the preceding optical preamplifier feeding through to the power amplifier), this disclosure teaches remedying that problem by pulsed pumping the optical preamplifier (rather than pumping the optical preamplifier with a CW pump). Furthermore, for multistage optical preamplifiers, only the final preamplification stages that follow an acousto-optical modulator (AOM) needs to be pulse pumped (meaning, the remaining preamplification stages before the AOM can continue to be pumped using CW pumps). By pulse-pumping the final stage of the preamplifier, we achieved 99.96% in-pulse power fraction at its output even at low repetition rate of 150 Hz. The inter-pulse power fraction at the signal wavelength was reduced to -34 dB at the preamplifier output, thus reducing the feedthrough therefrom to the high-gain power amplifier section. While keeping the power amplifier CW-pumped, and upon pulse-pumping the preamplifier final stage, theextractable pulse energy from the power amplifier increased by factor of 1.82, with corresponding improvement in the in-pulse power fraction by factor of 1.76. While keeping the power amplifier pulse-pumped, and upon pulse-pumping the preamplifier final stage, the extractable pulse energy from the power amplifier increased by factor of 1.27, with corresponding improvement in the in-pulse power fraction by factor of 1.6.

[0016] Having provided a broad technical solution to a technical problem, reference is now made in detail to the description of the embodiments as illustrated in the drawings. While several embodiments are described in connection with these drawings, there is no intent to limit the disclosure to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents.

[0017] To clarify the terms and phrases used herein, as would be understood by those having skill in the art, the following definitions are provided for terms and phrases that are used throughout this disclosure.

[0018] "In-pulse power" means power contained within a signal pulse, covering just a pulse duration.

[0019] "In-pulse power fraction" means a fraction of the total power contained within the signal pulse, covering just the pulse duration.

[0020] "Inter-pulse power" means power between two signal pulses.

[0021] "Inter-pulse power fraction" means a fraction of the total power contained between two signal pulses. The in-pulse power fraction in combination with the inter-pulse power fraction represents the total power. When represented in decibels (dB), the reference value (of zero decibels (OdB)) is the total power. By way of example, an inter-pulse power fraction of -33dB means that the inter-pulse power fraction is 0.05% of the total power.

[0022] "In-band" means a wavelength range covered by signal pulses.

[0023] "Out-of-band" means a wavelength range covered by ASE, optical noise impairments, or remnant pump beam, excluding the in-band wavelength range.

[0024] "Pump-signal delay" means a time delay between a leading edge of a pump pulse and a leading edge of a signal pulse.

[0025] "Gain recovery time" means a time that it takes for a population inversion to be recovered completely or substantially completely after a signal pulse depletes or substantially depletes available gain.

[0026] "Upper-state lifetime" a time that it takes for a population in an excited state to decay exponentially to approximately thirty-seven percent (-37%) of an initial value due to spontaneous emission and / or other quenching effects.

[0027] "Low repetition rate" or "low rep rate" means a repetition rate of a signal such that a time period of pulses is greater than four times (>4x) the gain recovery time.

[0028] "Signal" means an optical beam that gets amplified at the expense of a pump beam, with a center wavelength that is longer than a center wavelength of the pump beam.

[0029] "Pump" means an optical beam that provides gain to the signal beam, with a center wavelength that is shorter than the center wavelength of the signal beam.

[0030] "Gain medium" means a physical material doped with rare-earth ions which can absorb optical energy at the pump wavelength band and radiate optical energy at the signal wavelength band. An optical "amplifier" section may include (i) solid-state gain medium with free-space interfaces to other bulk-optic components and devices, (ii) optical fiber gain medium with fiber-guided interfaces to other components and devices, or (iii) hybrid combination of solid-state and optical fiber gain media with hybrid combination of free-space and fiber-guided interfaces to other components and devices.

[0031] "Direct modulation" means signal pulses that are generated at a seed laser itself by directly modulating the cavity gain.

[0032] "External modulation" means signal pulses that are generated from a continuous-wave (CW) seed laser by using an external device, such as an acousto-optic modulator (AOM).

[0033] "Matched repetition rate" or "matched rep rate" means a repetition rate of pulse-pumped lasers at both a preamplifier and a power amplifier are substantially identical and substantially synchronized.

[0034] Other terms and phrases that are not expressly defined herein are understood according to their definitions or usage by those having ordinary skill in the art.

[0035] With these terms and phrases now defined clearly, attention is turned to FIG. 1, which is a block diagram showing one embodiment of an optical amplifier system 100. As shown in FIG. 1, the system 100 comprises an optical preamplifier 110 that is optically coupled to a power amplifier 120.

[0036] The power amplifier 120 comprises a power amplifier signal input 122, apower amplifier pump input 126, and a power amplifier signal output 128. The system 100 further comprises a power amplifier pump 124 that is optically coupled to the power amplifier pump input 126. For some embodiments, the power amplifier pump 124 is a pulsed pump that is substantially synchronized with an incoming signal pulse, thereby limiting ASE buildup at the power amplifier 120 itself.

[0037] The embodiment of FIG. 1 shows a multistage optical preamplifier 110 with an initial preamplification stage 130, one or more intermediate preamplification stages 140, and a final preamplification stage 150. Thus, if the optical preamplifier 110 is a four-stage optical preamplifier 110, then there would be two (2) intermediate preamplification stages 140; if the optical preamplifier is a three-stage optical preamplifier 110, then there would only be one (1) intermediate preamplification stage 140, and so on. However, it should be appreciated that only the final preamplification stage 150 affects the residual signal that feeds through to the power amplifier 120. Thus, the final preamplification stage 150 (which is the preamplification stage that precedes the power amplifier 120) is discussed first.

[0038] The final preamplification stage 150 comprises a preamplification stage signal input 152, a preamplification stage pump input 156, and a preamplification stage signal output 158. The preamplification stage pump input 156 is optically coupled to a preamplification pulsed pump 154, which provides pulsed pump power to the final preamplification stage 150. For some embodiments, the final preamplification stage 150 is optically coupled to a bandpass filter 160 that comprises a bandpass filter signal input 162 and a bandpass filter signal output 168. The bandpass filter signal input 162 is optically coupled to the final preamplification stage signal output 158, while the bandpass filter signal output 168 is optically coupled to the power amplifier signal input 122.

[0039] By pulsed pumping (rather than CW pumping) the final preamplification stage 150 of the optical preamplifier 110, we achieved 99.96% in-pulse power fraction at its output 168, 122 even at low repetition rate of 150 Hz. The inter-pulse power fraction at the signal wavelength was reduced to -34 dB at the preamplifier output 168, 122, thus reducing the feedthrough therefrom 110 to the high-gain power amplifier section 120. While keeping the power amplifier 120 CW-pumped, upon pulse-pumping the preamplifier final stage 150, the extractable pulse energy at the power amplifier output 128 increased by factor of 1.82, with corresponding improvement in the in-pulse power fraction by factor of 1.76. Whilekeeping the power amplifier 120 pulse-pumped, and upon pulse-pumping the preamplifier final stage 150, the extractable pulse energy at the power amplifier output 128 increased by factor of 1.27, with corresponding improvement in the in-pulse power fraction by factor of 1.6.

[0040] For different embodiments, the inter-pulse power fraction (in comparison to the total power) at the optical preamplifier output is less than -27dB (or, less than 0.2% of the total power). Preferably, the inter-pulse power fraction at the optical preamplifier output is less than -30dB (or, less than 0.1% of the total power). More preferably, the inter-pulse power fraction at the optical preamplifier output is less than -33dB (or, less than 0.05% of the total power). Although this disclosure teaches one approach to achieving these preferable values for the inter-pulse power fraction (namely, by pulse pumping of the optical preamplifier), it should be appreciated that the improvements that are realized at the output of the power amplifier correspond to the improvements in the inter-pulse power fraction at the output of the optical preamplifier regardless of the means by which the inter-pulse power fraction at the optical preamplifier output is reduced.

[0041] Continuing with FIG. 1, in this particular embodiment of the system 100 with the multistage optical preamplifier 110, the initial preamplification stage 130 comprises an initial preamplification stage signal input 132, an initial preamplification stage pump input 136, and an initial preamplification stage signal output 138. The initial preamplification stage pump input 136 is optically coupled to a first continuous-wave (CW) pump 134 that pumps the initial preamplification stage 130 with CW pump power.

[0042] The intermediate preamplification stage 140 comprises an intermediate preamplification stage signal input 142 that is optically coupled to the initial preamplification stage signal output 138. The intermediate preamplification stage 140 further comprises an intermediate preamplification stage pump input 146, and an intermediate preamplification stage signal output 148. The intermediate preamplification stage pump input 146 is optically coupled to a second CW pump 144 that pumps the intermediate preamplification stage 140 with CW pump power.

[0043] The optical system 100 further comprises an acousto-optic modulator (AOM) 170 with an AOM signal input 172 and an AOM signal output 178. The AOM signal input 172 is optically coupled to the intermediate amplification stage signal output 148, while theAOM signal output 178 is optically coupled to the final preamplification stage signal input 152.

[0044] In the system 100 of FIG. 1, residual inter-pulse power arises as a result of a limited extinction ratio in the AOM 170. This residual inter-pulse power gets amplified within the final stage of the preamplifier 150. The inter-pulse power spectrum measured at the band-pass filter output 168 thus shows an in-band peak at the signal wavelength. . When the final preamplification stage 150 is pulse-pumped, the strength of the in-band peak in the inter-pulse power spectrum at the band pass filter output 168 is reduced substantially, such that the inter-pulse power fraction is reduced to less than -33 dB (0.05%) in one embodiment. Consequently, by pulse-pumping the final preamplification stage 150 of the optical preamplifier 110, the disclosed optical system 100 mitigates the effects of residual inter-pulse feed-through energy from the optical preamplifier 110 to the power amplifier 120, which diverges from the prior-art approach of mitigating ASE within the power amplifier 120.

[0045] Although FIG. 1 demonstrates an optical preamplifier 110 with a single preamplification stage 150 between the AOM 170 and the power amplifier 120, it should be appreciated that, for other embodiments, multiple preamplification stages may exist between the AOM 170 and the power amplifier 120. In such embodiments, all of the post-AOM, prepower-amplifier stages are pulsed pumped. One such embodiment is shown in FIG. 2.

[0046] FIG. 2 is a block diagram showing an optical amplifier system 200 with multiple intermediate preamplification stages 240 and a final preamplification stage 250 between an AOM 270 and a power amplifier 220. Unlike the embodiment of FIG. 1 (which shows a single final pre-amplification stage 150 between the AOM 170 and the power amplifier 120), the embodiment of FIG. 2 shows multiple pre-amplification stages 240 between the AOM 270 and the power amplifier 220. When multiple pre-amplification stages exist between the AOM 270 and the power amplifier 220, it should be appreciated that all of those preamplification stages affect the residual signal that feeds through to the power amplifier 220. Thus, the intermediate preamplification stage 240 should also be pulse- pumped, in addition to pulse-pumping the final preamplification stage 250.

[0047] With this in mind, FIG. 2 shows an optical preamplifier 210 that is optically coupled to a power amplifier 220, with the power amplifier 220 being pumped by a power amplifier pump 224. As such, the power amplifier 220 comprises a power amplifier signalinput 222, a power amplifier pump input 226 (which is optically coupled to the power amplifier pump 224), and a power amplifier signal output 228. The optical preamplifier 210 comprises an initial preamplifier stage 230 (which is pumped by a CW pump 234), an AOM 270, an intermediate preamplification stage 240 (pumped by a first pulsed pump 244), a final preamplifier stage 250 (pumped by a second pulsed pump 254), and a bandpass filter 260.

[0048] The initial preamplification stage 230 comprises an initial preamplification stage signal input 232, an initial preamplification stage pump input 236 that is optically coupled to the CW pump 234, and an initial preamplification stage signal output 238. The CW pump 234, therefore, provides CW pump power to the initial preamplification stage 230. The AOM 270 comprises an AOM input 272 (which is optically coupled to the initial preamplification stage signal output 238) and an AOM output 278.

[0049] The intermediate preamplification stage 240, which follows the AOM 270, comprises an intermediate preamplification stage signal input 242 (which is optically coupled to the AOM output 278), an intermediate preamplification stage pump input 246 (which is optically coupled to the first pulsed pump 244), and an intermediate preamplification stage signal output 248. Insofar as the intermediate preamplification stage 240 follows the AOM 270, the intermediate preamplification stage 240 is pulse-pumped (rather than being pumped with a CW pump). This is because the intermediate preamplification stage 240 that follows the AOM 270 amplifies the residual inter-pulse pump power that arises as a result of the limited extinction ratio in the AOM 270. Consequently, to mitigate the effects of residual feed-through energy, the intermediate preamplification stage 240 is also pulsed pumped.

[0050] The final preamplification stage 250, which follows the intermediate preamplification stage 240, comprises a final preamplification stage signal input 252 (which is optically coupled to the intermediate preamplification stage signal output 248), a final preamplification stage pump input 256 (which is optically coupled to the second pulsed pump 254), and a final preamplification stage signal output 258. Insofar as the final preamplification stage 250 also exists between the AOM 270 and the power amplifier 220 (similar to how the intermediate preamplification stage 240 exists between the AOM 270 and the power amplifier 220), the final preamplification stage 250 is also pulsed pumped to mitigate the effects of residual feed-through energy.

[0051] For some embodiments, the final preamplification stage 250 is opticallycoupled to a bandpass filter 260 that comprises a bandpass filter signal input 262 and a bandpass filter signal output 268. The bandpass filter signal input 262 is optically coupled to the final preamplification stage signal output 258, while the bandpass filter signal output 268 is optically coupled to the power amplifier signal input 222.

[0052] By pulsed pumping (rather than CW pumping) the preamplification stages 240, 250 that reside between the AOM 270 and the power amplifier 220, the system 200 reduces substantially the inter-pulse power at the optical preamplifier output 268. That improvement results in a corresponding enhancement of the extractable pulse energy at the power amplifier signal output 228.

[0053] Again, as shown in the system 200 of FIG. 2, pulse-pumping the preamplification stages 240, 250 of the optical preamplifier 210 that follow the AOM 270 mitigates the effects of residual inter-pulse feed-through energy from the optical preamplifier 210. Ultimately, the effects of pre- AOM preamplification stages are largely segregated from post-AOM preamplification stages, thereby making mitigation of residual feed-through energy post-AOM more significant than residual energy pre- AOM.

[0054] It is worthwhile to note that, because the prior art teaches pulsed pumping of the power amplifier (meaning, after the preamplifier), the prior art system already taught quelling of the ASE build-up between pulses by the pulse-pumping at the power amplifier. Consequently, the inventors believe that those having skill in the art did not recognize or appreciate the extent to which extractable pulse energy could be increased by also pulsepumping the preamplification stages that followed the AOM. As such, much of the efforts by those having skill in the art were dedicated to pulse shaping (meaning, to shaping the in- band signal), rather than to considering the period between pulses. Furthermore, for higher signal repetition rates, CW pumping sufficiently increased optical signal-to-noise ratio (OSNR) at a given center wavelength, thereby largely removing the need for pulsed pumping at higher repetition rates. As such, discovering the source of the problem (namely, the residual inter-pulse power feed-through to the power amplifier, which was not appreciated by those having skill in the art) was a significant contribution to that led to the embodiments described herein.

[0055] Although exemplary embodiments have been shown and described, it will be clear to those of ordinary skill in the art that a number of changes, modifications, oralterations to the disclosure as described may be made. For example, although the pump for the initial preamplification stage 130, 230 is shown to be a CW pump 133, 234, it should be appreciated that a pulsed pump can be implemented at the initial preamplification stage 130, 230. Similarly, although a CW pump 144 is shown for the intermediate preamplification stage(s) 140 prior to the AOM 170, it should be appreciated that a pulsed pump can also be implemented for pre- AOM intermediate preamplification stage(s) 140. As long as the residual energy at the output of the final preamplification stages 150, 240, 250 is mitigated, the energy extraction at the power amplifier 120, 220 is enhanced considerably.

[0056] All such changes, modifications, and alterations should therefore be seen as within the scope of the disclosure.

Claims

What is claimed is:

1. A system comprising: a multistage optical preamplifier comprising: an acousto-optical modulator (AOM) comprising: an AOM signal input; and an AOM signal output; a pre- AOM preamplification stage optically coupled to the AOM, the preamplification stage comprising: a pre- AOM preamplification stage continuous-wave (CW) signal input; a pre- AOM preamplification stage pump input; and a pre- AOM preamplification stage signal output optically coupled to the AOM input; a pre- AOM preamplification pump optically coupled to the preamplification stage pump input; a post- AOM preamplification stage optically coupled to the AOM, the post- AOM preamplification stage comprising: a post- AOM preamplification stage signal input optically coupled to the AOM signal output; a post-AOM preamplification stage pump input; and a post-AOM preamplification stage signal output; a post-AOM preamplification stage pulsed pump optically coupled to the post- AOM preamplification stage pump input; a power amplifier comprising: a power amplifier signal input optically coupled to the post-AOM preamplification stage signal output; a power amplifier pump input; and a power amplifier signal output; and a power amplifier pulsed pump optically coupled to the power amplifier pump input.

2. The system of claim 1, further comprising:a bandpass filter optically coupled between the post-AOM amplification stage and the power amplifier, the bandpass filter comprising: a bandpass filter signal input optically coupled to the post-AOM preamplification stage signal output; and a bandpass filter signal output optically coupled to the power amplifier signal input.

3. The system of claim 1, wherein the pre-AOM amplification pump is a CW pump.

4. A system comprising: a multistage optical preamplifier comprising: an initial preamplification stage comprising: an initial preamplification stage pulsed signal input; an initial preamplification stage pump input; and an initial preamplification stage pulsed signal output; a first pump optically coupled to the initial preamplification stage pump input; and a final preamplification stage comprising: a final preamplification stage signal input optically coupled to the initial preamplification stage signal output; and a final preamplification stage pump input; and a final preamplification stage signal output; a preamplification pulsed pump optically coupled to the final preamplification stage pump input; and a power amplifier comprising: a power amplifier signal input optically coupled to the final preamplification stage signal output; a power amplifier pump input; and a power amplifier signal output; and a power amplifier pulsed pump optically coupled to the power amplifier pump input.

5. The system of claim 4, further comprising an acousto-optical modulator (AOM) located between the initial preamplification stage and the final preamplification stage, the AOM being configured as a pulse picker to reduce a signal repetition rate from the initial preamplification stage to the final preamplification stage, the AOM comprising: an AOM signal input optically coupled to the initial preamplification stage signal output; and an AOM signal output optically coupled to the final preamplification stage signal input.

6. The system of claim 4, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty-three decibels (-33dB).

7. The system of claim 4, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty decibels (-30dB).

8. The system of claim 4, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative twenty-seven decibels (-27dB).

9. A system comprising: an optical preamplifier comprising: a preamplification stage pump input; and a preamplification stage signal output; a preamplification pulsed pump optically coupled to the preamplification stage pump input; and a power amplifier comprising: a power amplifier signal input optically coupled to the preamplification stage signal output; a power amplifier pump input; and a power amplifier signal output; anda power amplifier pump optically coupled to the power amplifier pump input.

10. The system of claim 9, wherein the preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty-three decibels (-33dB).

11. The system of claim 9, wherein the preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty decibels (-30dB).

12. The system of claim 9, wherein the preamplification stage signal output comprises an inter-pulse power fraction that is less than negative twenty-seven decibels (-27dB).

13. The system of claim 9, further comprising: a bandpass filter positioned between the optical preamplifier and the power amplifier, the bandpass filter comprising: a bandpass filter signal input optically coupled to the preamplification stage signal output; and a bandpass filter signal output optically coupled to the power amplifier signal input.

14. The system of claim 9, wherein the optical preamplifier further comprises a preamplification stage signal input, wherein the system further comprises: an acousto-optic modulator (AOM) comprising an AOM output optically coupled to the preamplification stage signal input.

15. The system of claim 14, wherein the optical preamplifier is a multistage optical preamplifier, wherein the preamplification stage is a final preamplification stage comprising a final preamplification stage signal input, wherein the preamplification stage signal output is a final preamplification stage signal output, wherein the preamplification stage pump input is a final preamplification stage pump input, wherein the AOM further comprises an AOM input, wherein the system further comprises: an intermediate preamplification stage comprising:an intermediate preamplification stage pump input; and an intermediate preamplification stage signal output optically coupled to the AOM input; and an intermediate stage pump optically coupled to the intermediate preamplification stage pump input.

16. The system of claim 15, wherein the intermediate stage pump is a continuous-wave (CW) pump.

17. The system of claim 16, wherein the intermediate preamplification stage further comprises an intermediate preamplification stage signal input, wherein the CW pump is a first CW pump, wherein the system further comprises: an initial preamplification stage comprising: an initial preamplification stage pump input; and an initial preamplification stage signal output optically coupled to the intermediate preamplification stage signal input; and a second CW pump optically coupled to the initial preamplification stage pump input.

18. The system of claim 15, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty-three decibels (-33dB).

19. The system of claim 15, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative thirty decibels (-30dB).

20. The system of claim 15, wherein the final preamplification stage signal output comprises an inter-pulse power fraction that is less than negative twenty-seven decibels (-27dB).

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