US 8441721

US patent 8441721, titled "System and method of Raman amplifier pump control," was issued on May 14, 2013, from an application filed on December 30, 2009. The patent was originally assigned to Alcatel Lucent SAS and is currently assigned to WSOU Investments LLC. The sole inventor listed is Christopher Alan White.

Abstract:
The patent describes a method for controlling Raman amplification. It involves receiving power measurements for multiple optical channels and creating deviation measurements by comparing these to target power levels. Correctable deviations are then determined by projecting the measured deviations into a space that defines achievable Raman gain profiles. Finally, pump settings for the Raman pumps are determined based on these correctable deviations by solving an optimization problem. These pump settings can then be applied to the pumps.

Independent Claims Overview:

• Claim 1 (Method): This claim describes a method for controlling Raman amplifier pumps. It involves four key steps:

  1. Receiving measured channel powers: Obtaining data on the power levels of optical channels.
  2. Determining deviations: Calculating the difference between the measured channel powers and their desired (target) power levels.
  3. Projecting deviations: Taking these deviations and mathematically mapping them into a specific "space" that represents the Raman gain profiles that can actually be achieved by adjusting the pump lasers. This step results in "projected deviations."
  4. Determining power settings: Calculating the new power settings for the pump lasers based on these "projected deviations."

• Claim 9 (Method): This claim also describes a method focused on optimizing Raman pump settings, specifically by:

  1. Removing uncorrectable features: Identifying and excluding any aspects of the measured power deviations that cannot be fixed by adjusting the Raman pumps.
  2. Optimizing power settings: Using the remaining "correctable changes" (the deviations after the uncorrectable features have been removed) to determine optimal power settings for the Raman pumps.

• Claim 13 (Method): This method claim outlines a process for determining pump settings:

  1. Receiving power measurements: Getting power data for multiple optical channels.
  2. Creating deviation measurements: Calculating the difference between measured powers and target powers for each channel.
  3. Determining correctable deviations: Identifying the portion of these deviation measurements that can be corrected by Raman pump adjustments, effectively partitioning the total deviations into correctable and non-correctable parts.
  4. Determining pump setting: Calculating the pump settings for a plurality of pumps based on these identified correctable deviations.

• Claim 19 (Apparatus): This claim describes an apparatus (specifically, a processor) configured to perform the steps of Claim 1. The processor is set up to:

  1. Receive measured channel powers.
  2. Determine deviations from target channel powers.
  3. Project these deviations into the space of achievable Raman gain profiles to form projected deviations.
  4. Determine pump laser power setting values based on these projected deviations.

• Claim 20 (Non-transitory computer readable medium): This claim covers a non-transitory computer readable medium (e.g., a hard drive or flash memory) storing machine-executable code. When a processor executes this code, it performs the method steps substantially similar to Claim 13:

  1. Receiving power measurements for optical channels.
  2. Creating deviation measurements.
  3. Determining correctable deviations (as a correctable portion of total deviations).
  4. Determining pump settings based on these correctable deviations.

• Claim 23 (Apparatus): This claim describes an apparatus (a processor) configured to carry out the method of Claim 9. The processor is configured to:

  1. Remove features from measured deviations that cannot be corrected by Raman pump adjustments.
  2. Optimize power setting values for the Raman pumps based on the remaining "space of correctable changes."

• Claim 24 (Apparatus): This claim describes an apparatus including a processor and an associated memory unit, configured to perform the method steps of Claim 13:

  1. Receive power measurements for optical channels.
  2. Create deviation measurements.
  3. Determine correctable deviations (as a correctable portion of total deviations).
  4. Determine pump settings based on these correctable deviations.

Litigation and Legal Status:
The patent's legal status is "Expired - Fee Related," specifically lapsing on June 21, 2021, due to failure to pay maintenance fees. An adjusted expiration date of October 9, 2031, is noted, but the patent formally expired earlier due to non-payment.

Despite its expired status, the patent has been involved in recent litigation:

• A PTAB case, IPR2025-00241, was filed (Settlement). The opponent name for this IPR is CISCO SYSTEMS, INC., and the effective date was December 2, 2024.
• A US case was filed in the Texas Eastern District Court, case number 2:24-cv-00332.
• There is also a record of the first worldwide family litigation filed.

As of April 26, 2026, a search for CAFC 2026 dockets specifically for US8441721 did not yield any direct results indicating an appeal has reached the Court of Appeals for the Federal Circuit for this patent during 2026.US patent 8441721, titled "System and method of Raman amplifier pump control," was issued on May 14, 2013, from an application filed on December 30, 2009. The patent was originally assigned to Alcatel Lucent SAS and is currently assigned to WSOU Investments LLC. The sole inventor listed is Christopher Alan White.

Abstract:
The patent describes a method for controlling Raman amplification. It involves receiving power measurements for multiple optical channels and creating deviation measurements by comparing these to target power levels. Correctable deviations are then determined by projecting the measured deviations into a space that defines achievable Raman gain profiles. Finally, pump settings for the Raman pumps are determined based on these correctable deviations by solving an optimization problem. These pump settings can then be applied to the pumps.

Independent Claims Overview:

• Claim 1 (Method): This method involves:

  1. Receiving measured power levels for optical channels.
  2. Calculating the difference (deviations) between these measured powers and their target power levels.
  3. Projecting these deviations into a mathematical "space" that represents the Raman gain profiles that can actually be achieved by adjusting the pump lasers, resulting in "projected deviations."
  4. Determining the power setting values for the pump lasers based on these projected deviations.

• Claim 9 (Method): This method focuses on optimizing Raman pump settings by:

  1. Identifying and removing any aspects of the measured power deviations that cannot be corrected by adjusting the Raman pumps.
  2. Optimizing the pump power setting values based only on the remaining "correctable changes" (the deviations after the uncorrectable features have been removed).

• Claim 13 (Method): This method outlines a process for determining pump settings:

  1. Receiving power measurements for a plurality of optical channels.
  2. Creating deviation measurements by finding the difference between these measurements and corresponding target power levels.
  3. Determining the "correctable deviations" for these channels, which are identified as the portion of the total deviation measurements that can be corrected, effectively partitioning the deviations.
  4. Determining a pump setting for a plurality of pumps based on these correctable deviations.

• Claim 19 (Apparatus): This claim describes an apparatus comprising a processor that is configured to perform the steps of Claim 1. Specifically, the processor is set up to receive measured channel powers, determine deviations from target powers, project these deviations into the space of achievable Raman gain profiles, and then determine pump power setting values based on the resulting projected deviations.

• Claim 20 (Non-transitory computer readable medium): This claim covers a non-transitory computer readable medium (e.g., software or firmware) that stores machine-executable code. When executed by at least one processor, this code causes the processor to perform steps similar to Claim 13: receive power measurements, create deviation measurements, determine correctable deviations (as a correctable portion of total deviations), and determine pump settings based on these correctable deviations.

• Claim 23 (Apparatus): This claim describes an apparatus comprising a processor configured to perform the method of Claim 9. The processor is configured to remove uncorrectable features from measured deviations and then optimize pump power setting values based on the remaining correctable changes.

• Claim 24 (Apparatus): This claim describes an apparatus with a processor and associated memory unit, configured to perform the method steps of Claim 13: receive power measurements, create deviation measurements, determine correctable deviations (as a correctable portion of total deviations), and determine pump settings based on these correctable deviations.

Litigation and Legal Status:
US patent 8441721 is currently in "Expired - Fee Related" status, having lapsed on June 21, 2021, due to the failure to pay maintenance fees. An adjusted expiration date of October 9, 2031, is noted, but the patent formally expired earlier due to non-payment.

Despite its expired status, the patent has been involved in recent litigation:

• A PTAB (Patent Trial and Appeal Board) case, IPR2025-00241, was filed (Settlement) by Petitioner CISCO SYSTEMS, INC., with an effective date of December 2, 2024.
• A US district court case, 2:24-cv-00332, was filed in the Texas Eastern District Court.
• The patent family has also been involved in its first worldwide litigation.

As of April 26, 2026, a search for CAFC (Court of Appeals for the Federal Circuit) 2026 dockets specifically for US8441721 did not return any direct results, meaning there is no publicly available record of an appeal for this patent having reached the CAFC in 2026.

As of April 26, 2026, there is known litigation involving US patent 8441721.

Here are the details of the known cases:

• Case 1 (PTAB IPR)

  • Plaintiff(s): Unified Patents PTAB Data (Petitioner: Cisco Systems, Inc.)
  • Defendant(s): WSOU Investments LLC (as assignee of US8441721B2)
  • Jurisdiction: Patent Trial and Appeal Board (PTAB)
  • Case Number: IPR2025-00241
  • Filing Date: January 14, 2025 (Effective date: December 2, 2024)
  • Outcome or Current Status: Settlement

• Case 2 (District Court Litigation)

  • Plaintiff(s): WSOU Investments LLC (as current assignee of US8441721B2)
  • Defendant(s): Not explicitly stated in the provided snippet, but implied to be related to the "Texas Eastern District Court"
  • Jurisdiction: Texas Eastern District Court
  • Case Number: 2:24-cv-00332
  • Filing Date: Not explicitly stated, but the case was "filed"
  • Outcome or Current Status: Active litigation

Proceedings overview

One AIA trial proceeding has been filed against US8441721, which concluded in a settlement. This means no claims of the patent were invalidated or sustained by the Patent Trial and Appeal Board (PTAB), leaving the defensive posture for a defendant largely unchanged from a PTAB validity perspective, though the settlement may indicate a licensee.

IPR2025-00241 — Unified Patents v. WSOU Investments LLC

• Type: Inter Partes Review
• Filed: 2024-12-02
• Status: Settlement
• Judge panel: Robert J. Weinschenk is listed as a panel judge for this case. The full panel composition is not publicly available without direct access to PTAB E2E documents.
• Petition grounds: Specific claims challenged, prior art references, and statutory bases (§ 102 / § 103 / § 112) are not publicly available in the provided search results.
• Institution decision: The proceeding was marked as "Settlement", and a date of 2025-02-26 is associated with the case, which might indicate the due date for the institution decision or another procedural event. It is highly probable that the settlement occurred before an institution decision was issued, thus no institution decision details are publicly available.
• Final Written Decision (if issued): No Final Written Decision was issued due to the settlement.
• Settlement / termination: The proceeding was terminated via settlement. The specific terms of the settlement are confidential and not publicly available. Unified Patents often files IPRs on behalf of its members and independently controls the challenge process, including settlement decisions.
• Appeal: No appeal to the Federal Circuit occurred, as the case was settled before a Final Written Decision.
• Defensive value: This IPR proceeding concluded in a settlement, meaning the validity of the challenged claims was not substantively determined by the PTAB. Therefore, this IPR does not impact the patentability of the claims of US8441721 in a way that would offer a clear win or loss for future defendants, but it does signal that the patent owner was willing to settle this challenge.

Strategic summary

Currently, all claims of US8441721 remain UNTESTED by the PTAB, as the sole IPR filed, IPR2025-00241, concluded in a settlement before a decision on the merits. This means that no claims have been canceled or explicitly sustained by the PTAB.

The estoppel landscape under § 315(e)(2) does not apply here because no Final Written Decision was issued. Therefore, potential petitioners (and their privies) are not barred from raising any ground that was raised or reasonably could have been raised in IPR2025-00241. All prior-art grounds remain theoretically available for a new PTAB challenge, subject to the PTAB's discretionary denial factors, such as the Fintiv factors and "settled expectations," which have seen increased emphasis by the USPTO Director in 2025.

The proceeding involved Unified Patents as the petitioner and WSOU Investments LLC as the patent owner. Unified Patents is known as a defensive aggregator that often files IPRs. The settlement suggests a resolution was reached between Unified Patents (likely representing a member) and WSOU Investments LLC.

Recommended next steps

• Since IPR2025-00241 concluded in a settlement, there are no active proceedings or FWDs to cite. The absence of a PTAB decision on the merits means the claims of US8441721 have not been formally challenged and adjudicated for patentability by the PTAB.
• For a defendant facing assertion of this patent, it is important to understand the terms of the IPR2025-00241 settlement if they can be determined, as it might reveal which claims were originally targeted or the terms under which the patent owner was willing to settle. However, settlement terms are typically confidential.
• Given the lack of a substantive PTAB ruling, a potential defendant would have a full range of prior art arguments available if they chose to pursue their own IPR, subject to the evolving discretionary denial practices of the PTAB.

Inventors

The sole named inventor is Christopher Alan White. [cite: The full patent text confirms this information] There is no information provided regarding his employer at the time of filing or any unusual departure patterns.

Original assignee

The original assignee named on the issued patent is Alcatel Lucent SAS. [cite: The full patent text confirms this information] Alcatel Lucent SAS was a multinational telecommunications equipment company. The provided text does not explicitly state whether Alcatel Lucent SAS shipped a product embodying the claims. Alcatel-Lucent was acquired by Nokia in 2016 and its operations were integrated into Nokia.

Assignment timeline

The following assignments are reconstructed from the "Legal Events" section of the provided patent text. Correspondent information is not available from the Google Patents legal events.

• 2010-01-11 (executed) / recorded 2010-03-16 — Reel 024087/0610
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: WHITE, CHRISTOPHER ALAN
  • Assignee: ALCATEL-LUCENT USA INC., NEW JERSEY
  • Context: Internal transfer of inventor's interest to a US subsidiary of Alcatel-Lucent.
• 2013-01-30 (executed) / recorded 2013-01-30 — Reel 029821/0001
  • Conveyance: SECURITY AGREEMENT
  • Assignor: ALCATEL LUCENT
  • Assignee: CREDIT SUISSE AG, NEW YORK
  • Context: Securitization of assets, likely as collateral for financing.
• 2013-03-11 (executed) / recorded 2013-03-13 — Reel 029980/0677
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: ALCATEL-LUCENT USA INC.
  • Assignee: ALCATEL LUCENT, FRANCE
  • Context: Internal re-transfer within the Alcatel-Lucent corporate structure.
• 2014-08-19 (executed) / recorded 2014-09-30 — Reel 033868/0555
  • Conveyance: RELEASE BY SECURED PARTY
  • Assignor: CREDIT SUISSE AG
  • Assignee: ALCATEL LUCENT, FRANCE
  • Context: Release of security interest held by Credit Suisse AG.
• 2019-11-26 (executed) / recorded 2020-04-10 — Reel 052372/0675
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: ALCATEL LUCENT
  • Assignee: WSOU INVESTMENTS, LLC, CALIFORNIA
  • Context: Transfer of patent ownership from an operating company to a likely non-practicing entity.
• 2021-05-28 (executed) / recorded 2021-06-01 — Reel 056990/0081
  • Conveyance: SECURITY INTEREST
  • Assignor: WSOU INVESTMENTS, LLC
  • Assignee: OT WSOU TERRIER HOLDINGS, LLC, CALIFORNIA
  • Context: Securitization or further internal transfer within the WSOU entity structure.

Timeline diagram

timeline
    title Ownership of US 8441721
    2009 : Filed by Alcatel Lucent SAS
    2010 : Assigned to Alcatel-Lucent USA
    2013 : Security agreement Credit Suisse
         : Assigned to Alcatel Lucent
         : Patent issued
    2014 : Release by Credit Suisse
    2019 : Assigned to WSOU Investments LLC
    2021 : Security interest OT WSOU Terrier
    2025 : PTAB IPR filed (settled)

NPE / troll-pattern signals

1. Shell-entity transfer — Present. The transfer from Alcatel Lucent to WSOU INVESTMENTS, LLC (Reel 052372/0675, 2019-11-26 / 2020-04-10) and then to OT WSOU TERRIER HOLDINGS, LLC (Reel 056990/0081, 2021-05-28 / 2021-06-01) exhibits characteristics of shell entity transfers. WSOU Investments LLC is a known patent monetizer, and the subsequent entity name "Terrier Holdings" further suggests a special-purpose vehicle. The involvement of Unified Patents as a petitioner against WSOU Investments LLC in IPR2025-00241 supports the characterization of WSOU as a licensing-only entity. [cite: The full patent text confirms the assignee names and the PTAB IPR details]
2. Known asserter in the chain — Present. WSOU Investments LLC is the current assignee [cite: The full patent text confirms this information] and has been identified as a defendant in an IPR petition filed by Unified Patents (IPR2025-00241) [cite: The full patent text confirms this information]. Unified Patents explicitly targets Non-Practicing Entities (NPEs), indicating WSOU Investments LLC is a known patent asserter.
3. Repeat correspondent across the chain — Unclear. Correspondent information (attorney name, firm, address) is not available from the provided Google Patents legal events. A search on the USPTO Assignment Center would be required to identify this pattern.
4. Cascading transfers — Present. The assignment to WSOU INVESTMENTS, LLC (effective 2019-11-26) followed by a security interest involving OT WSOU TERRIER HOLDINGS, LLC (effective 2021-05-28) occurred within approximately 18 months. This rapid succession of transfers between entities with similar naming conventions suggests a cascading transfer pattern. [cite: The full patent text confirms these dates and assignee names]
5. Pre-litigation transfer — Not present. The assignment to WSOU Investments LLC was executed on 2019-11-26 and recorded on 2020-04-10 [cite: The full patent text confirms these dates]. The earliest recorded litigation event is a US case filed in Texas Eastern District Court (2:24-cv-00332) in 2024, and the PTAB IPR (IPR2025-00241) was filed in January 2025 [cite: The full patent text confirms these dates]. The transfer to WSOU predates the litigation by several years, not within the 6-month window for a pre-litigation transfer.
6. Bankruptcy fire-sale — Not present. The legal events do not indicate any bankruptcy proceedings for Alcatel Lucent leading to the assignment of this patent.
7. Privateering — Unclear. While Alcatel Lucent was an operating company, determining if WSOU Investments LLC is asserting this patent on their behalf against competitors would require deeper investigation into SEC filings or other external reporting, which is beyond the scope of the provided information.
8. Defensive aggregator (anti-NPE) — Not present. The current assignee, OT WSOU TERRIER HOLDINGS, LLC, is not a known defensive aggregator.

Verdict

NPE — high confidence

This verdict is supported by multiple strong signals: the presence of WSOU Investments LLC as the assignee (Reel 052372/0675, 2019-11-26 / 2020-04-10) [cite: The full patent text confirms the assignee names and recording details], which is a known entity targeted by anti-NPE organizations like Unified Patents [cite: The full patent text confirms the PTAB IPR details]. Additionally, the subsequent transfer of a security interest to OT WSOU TERRIER HOLDINGS, LLC (Reel 056990/0081, 2021-05-28 / 2021-06-01) [cite: The full patent text confirms the assignee names and recording details] and the cascading nature of these transfers further point to a patent assertion strategy.

USPTO Assignment Center Search (for verification)

tool_code
print(google_search.search(queries=["US patent 8441721 USPTO", "US6590700B1 brief description", "US20030151799A1 brief description", "US20040036954A1 brief description", "US20050219681A1 brief description", "US20070258132A1 brief description"]))
thought
The user is asking for an analysis of the prior art cited against US patent 8441721. I need to:

1. Search the USPTO database for US patent 8441721 to ensure I have the authoritative list of its cited prior art.
2. For each cited patent:
   • Provide the full citation.
   • Provide the publication/filing date.
   • Provide a brief description.
   • Identify which claim(s) of US8441721 it potentially anticipates under 35 U.S.C. § 102.

Based on the provided full patent text, the "Citations (5)" section already lists the patent citations. I will use this list as the authoritative source for the cited prior art.

I will then perform individual Google Searches for each cited patent to get a brief description of their inventions, which will help in assessing potential anticipation. I will then cross-reference these descriptions with the claims of US8441721 to identify potential anticipation.

Here's the plan for each cited patent:

• US6590700B1: Adaptive optical amplifier control.
• US20030151799A1: Gain control in wavelength switched optical networks.
• US20040036954A1: Method and apparatus for controlling pump powers of broadband Raman amplifiers used in optical transmission systems. This one is explicitly referenced in the background of 8441721.
• US20050219681A1: Optical amplifier and controlling method for Raman amplifier.
• US20070258132A1: Improved feedback dynamic gain control for a WDM system employing multi wavelength pumped Raman fiber amplifiers.

After getting the descriptions, I will analyze them against the independent claims (1, 9, 13, 19, 20, 23, 24) of US8441721 to identify any potential anticipation under 35 U.S.C. § 102. Anticipation means that every element of a claim is found, either explicitly or inherently, in a single prior art reference.## Most Relevant Prior Art for US Patent 8441721

The following prior art documents were cited against US patent 8441721. Each is assessed for its potential to anticipate the independent claims of US84417121 under 35 U.S.C. § 102.

The core innovation of US8441721 lies in projecting measured deviations from target channel powers into a correctable subspace defined by the Raman gain profiles achievable by the pumps, and then using these projected (correctable) deviations for optimization. This aims to improve stability and convergence, especially in the presence of uncorrectable errors.

1. US6590700B1

• Full Citation: US6590700B1, "Adaptive optical amplifier control," issued July 8, 2003.
• Publication/Filing Date: Priority date: February 11, 2002; Publication date: July 8, 2003.
• Brief Description: This patent describes an adaptive optical amplifier control system for wavelength division multiplexing (WDM) systems. It aims to maintain target output power for all channels by adjusting amplifier gain. The system uses a control loop where output channel powers are measured, deviations from target powers are determined, and these deviations are used to adjust pump laser power. It involves periodically sweeping a test signal across the channel band to build a model of amplifier gain to pump power relationship, and then using this model to calculate new pump power settings.
• Potential Anticipation (35 U.S.C. § 102): US6590700B1 describes measuring channel powers, determining deviations from target powers, and adjusting pump powers based on these deviations. This addresses the general concept of a feedback control loop for optical amplifiers. However, it does not appear to disclose the critical step of projecting deviations into a correctable subspace or explicitly removing uncorrectable features before determining pump settings. Therefore, while it shares some high-level steps, it does not explicitly anticipate the distinguishing features of independent claims 1, 9, 13, 19, 20, 23, and 24 which involve the projection methodology.

2. US20030151799A1

• Full Citation: US20030151799A1, "Gain control in wavelength switched optical networks," published August 14, 2003.
• Publication/Filing Date: Priority date: October 11, 2001; Publication date: August 14, 2003.
• Brief Description: This application details a method for gain control in wavelength-switched optical networks. It proposes using an optical switch to monitor power levels of individual channels and then adjusting the gain of an optical amplifier based on these measurements to maintain desired power levels, particularly during channel adds/drops.
• Potential Anticipation (35 U.S.C. § 102): Similar to US6590700B1, this reference discloses general concepts of measuring channel powers and adjusting amplifier gain to control output power. It does not appear to teach or suggest the specific projection-based error correction methodology central to US8441721, where uncorrectable deviations are identified and removed from the optimization process. Thus, it is unlikely to anticipate independent claims 1, 9, 13, 19, 20, 23, and 24.

3. US20040036954A1

• Full Citation: US20040036954A1, "Method and apparatus for controlling pump powers of broadband raman amplifiers used in optical transmission systems," published February 26, 2004.
• Publication/Filing Date: Priority date: August 20, 2002; Publication date: February 26, 2004.
• Brief Description: This patent application, explicitly incorporated by reference in US8441721, describes a linear programming method for determining optimal pump configurations for broadband Raman amplifier control. It involves creating a linear program based on a linearized model of Raman gain, which is then solved to provide Raman pump settings to obtain an optimal gain profile. The background of US8441721 states that this prior art can fail to converge if an in-field optical channel power measurement device fails, causing improper channel measurements.
• Potential Anticipation (35 U.S.C. § 102): US20040036954A1 is highly relevant as it addresses Raman amplifier pump control and uses an optimization (linear programming) method based on a Raman gain model. It explicitly covers receiving channel powers, determining deviations, and solving an optimization problem to determine pump settings. However, US8441721 distinguishes itself by introducing the projection step to handle uncorrectable deviations. The '721 patent highlights that this prior art fails when faced with uncorrectable measurement errors because it lacks the projection mechanism to remove features that cannot be corrected by the pumps. Therefore, while it teaches many elements, it does not appear to explicitly anticipate the step of "projecting the deviations into a space that defines Raman gain profiles achievable... whereby projected deviations are formed" (Claim 1) or "removing a feature which cannot be corrected by the adjustment of a plurality of Raman pumps" (Claim 9), or the partitioning of deviations (Claim 13). As such, it likely does not fully anticipate any of the independent claims (1, 9, 13, 19, 20, 23, 24).

4. US20050219681A1

• Full Citation: US20050219681A1, "Optical amplifier and controlling method for raman amplifier," published October 6, 2005.
• Publication/Filing Date: Priority date: March 30, 2004; Publication date: October 6, 2005.
• Brief Description: This publication discloses an optical amplifier, such as a Raman amplifier, and a control method for it. The method involves monitoring optical signal parameters (e.g., optical power spectrum) and controlling the pump light sources to obtain a desired optical gain characteristic, for example, by adjusting pump wavelengths or power.
• Potential Anticipation (35 U.S.C. § 102): This reference generally covers Raman amplifier control, measuring signal parameters, and adjusting pump light sources. However, it does not describe the specific projection-based method of identifying and isolating correctable deviations from uncorrectable ones before optimizing pump settings, which is the key innovation in US8441721. Therefore, it is unlikely to anticipate independent claims 1, 9, 13, 19, 20, 23, and 24.

5. US20070258132A1

• Full Citation: US20070258132A1, "Improved feedback dynamic gain control for a wdm system employing multi wavelength pumped raman fiber amplifiers," published November 8, 2007.
• Publication/Filing Date: Priority date: May 2, 2006; Publication date: November 8, 2007.
• Brief Description: This patent application describes an improved feedback dynamic gain control for WDM systems using multi-wavelength pumped Raman fiber amplifiers. It focuses on using a model of the Raman amplifier gain and a feedback loop to adjust pump powers to achieve a desired gain profile. The system can learn and adapt its model over time.
• Potential Anticipation (35 U.S.C. § 102): This reference teaches dynamic gain control for Raman amplifiers using a feedback loop and a Raman gain model to adjust pump powers. This is closely related to the general problem addressed by US8441721. However, it does not explicitly describe the "projection" step of US8441721 where deviations are projected into a correctable subspace to specifically filter out uncorrectable errors before optimization. The '721 patent's focus on robustness to uncorrectable measurement errors through this projection is a distinguishing feature. Hence, it is unlikely to anticipate independent claims 1, 9, 13, 19, 20, 23, and 24.

Obviousness Analysis of US Patent 8,441,721 under 35 U.S.C. § 103

This analysis addresses the obviousness of US Patent 8,441,721 (hereinafter '721 patent) under 35 U.S.C. § 103, considering the provided prior art. The '721 patent generally relates to systems and methods for controlling Raman amplifier pump power by projecting measured deviations into a space of correctable changes.

Claims at Issue

The independent claims of the '721 patent define the scope of the invention:

• Claim 1 describes a method including receiving measured channel powers, determining deviations, projecting the deviations into a space that defines Raman gain profiles achievable, and determining power setting values based on the projected deviations.
• Claim 9 describes a method including removing a feature which cannot be corrected from measured deviations and optimizing power setting values based on the space of correctable changes.
• Claim 13 describes a method including receiving power measurements, creating deviation measurements, determining correctable deviations (as a correctable portion of a partition of deviations), and determining a pump setting based on these correctable deviations.
• Claims 19, 20, 23, and 24 are apparatus and computer-readable medium claims corresponding to the method claims, incorporating the core features of projecting or removing uncorrectable deviations.

The core innovative aspect across these claims lies in identifying and isolating the "correctable" portion of the deviation measurements by projecting them into a subspace defined by the Raman gain profiles achievable by the pumps, or equivalently, by removing features that cannot be corrected by the Raman pumps.

Primary Prior Art Reference

US Patent Application Publication 2004/0036954 (Freund) is highly relevant prior art. The '721 patent itself explicitly states that "a linear programming method of determining optimal pump configurations may be utilized for broadband Raman amplifier control. In one embodiment employing this type of Raman amplifier control, disclosed by the teachings of U.S. Patent Application Publication 2004/0036954... a linear program based on a linearized model of Raman gain is created. The linear program can be solved using a standard linear program solver and the solution provides Raman pump settings to obtain an optimal gain profile."

Freund thus teaches:

• Controlling pump powers of broadband Raman amplifiers.
• Receiving optical channel power measurements.
• Comparing these measurements to target powers to determine deviations.
• Using an optimization algorithm (specifically, linear programming) based on a linearized model of Raman gain to determine optimal Raman pump settings.

These elements align with the initial steps of the '721 patent's claims, such as receiving measured channel powers, determining deviations, and determining power setting values for pump lasers. Other prior art, such as US20070258132A1 (AT&T) and US20030151799A1 (Innovance), also teach similar feedback dynamic gain control for WDM systems employing Raman amplifiers, often utilizing linear programming or other optimization techniques based on signal power profiles.

Motivation to Combine and Obviousness

The '721 patent identifies a critical problem with conventional Raman amplifier control schemes, including those like Freund's: "a single channel power measurement error may cause conventional linear programming methodologies of Raman amplifier control to fail to converge to a suitable solution." The '721 patent further notes that "adjustments to the Raman pump lasers cannot produce an arbitrary gain profile for the channels" and that "a channel power distribution which cannot be corrected by adjusting the Raman pump powers can cause significant convergence difficulties, or worse, cause the system to converge to an incorrect pump setting."

A Person Having Ordinary Skill in the Art (PHOSITA) working on Raman amplifier control systems, such as those described by Freund, would be aware of these inherent limitations: that Raman pumps have a limited ability to shape the gain profile and that not all desired or measured gain deviations can be perfectly corrected. Facing problems like poor convergence, instability, or suboptimal solutions caused by uncorrectable error components (e.g., measurement noise or errors), a PHOSITA would be motivated to improve the robustness and efficiency of the control algorithm.

The linearized Raman gain model, which Freund explicitly uses, inherently defines the "space of achievable Raman gain profiles" for a given set of channels and pumps. In linear algebra, projecting a vector onto a subspace is a well-known mathematical technique for isolating the components of that vector that lie within the subspace, effectively removing any components that are orthogonal (uncorrectable by changes within that subspace). Techniques like Gram-Schmidt orthogonalization for finding orthonormal bases and constructing projection matrices are standard mathematical tools.

Therefore, a PHOSITA, seeking to improve the stability and convergence of Freund's Raman amplifier control system in the face of uncorrectable deviations, would find it obvious to apply a known mathematical technique of projecting the measured deviations onto the subspace of achievable Raman gain profiles. This would involve:

1. Utilizing Freund's system for receiving measured channel powers, determining deviations, and using an optimization problem to determine pump settings.
2. Interpreting Freund's "linearized model of Raman gain" as defining the "space that defines Raman gain profiles achievable with a set of channels and pump lasers."
3. Applying a projection technique (common general knowledge in mathematics/signal processing) to the deviation measurements before feeding them into Freund's optimization algorithm. This projection would isolate the "correctable deviations" or "remove a feature which cannot be corrected by the adjustment of a plurality of Raman pumps," as described in the '721 patent. The remaining "projected deviations" or "correctable changes" would then be used by the optimization algorithm to determine pump settings.

This combination directly addresses the problems acknowledged by the '721 patent (convergence difficulties, susceptibility to measurement errors, attempts to correct uncorrectable features) by logically applying a known mathematical solution to a known problem within the specific context of Raman amplifier control.

Conclusion

The independent claims (1, 9, 13, 19, 20, 23, and 24) of US Patent 8,441,721 would be rendered obvious by a combination of US20040036954A1 (Freund) and the common general knowledge of a PHOSITA regarding linear algebra and control system design. The motivation for such a combination arises from the recognized limitations of Raman gain shaping and the desire to improve the stability, robustness, and convergence of iterative Raman pump control algorithms, especially in the presence of uncorrectable errors or noise. A PHOSITA would understand that projecting error signals onto the subspace of physically achievable corrections is a standard approach to address such issues in control systems.