US 10935399

I'll verify this patent against live sources and check for any litigation or CAFC activity.

Let me check specifically for PTAB proceedings, assignments, and any court activity.

Search methodology and its limits (read first)

I can run general web searches, but I cannot log directly into USPTO PatentCenter/Patent Trial and Appeal Board (PTAB) APIs or the CAFC docket system. What follows is grounded in (a) the full authoritative patent text you supplied (fetched from Google Patents), (b) the USPTO-printed front page PDF (patentimages, US010935399B1), and (c) targeted web searches. Where a query returned nothing, I say so rather than fill the gap.

Bottom line on dockets: I found no record of any district-court litigation, PTAB inter partes review / PGR, or CAFC 2026 appeal involving U.S. Patent No. 10935399. Searches combining 10935399/10,935,399 with "litigation," "CAFC 2026 docket," and "infringement lawsuit" surfaced only unrelated matters (Netlist/Micron, Contour v. GoPro, FlatFrog, Labcorp v. Natera, etc.) and Google Patents' "Cited By" linkage pages. I cannot rule out an unfiled or unindexed proceeding, so treat "no litigation found" as a search result, not a legal conclusion.

---

Bibliographic data (literal, as printed)

Note on the assignee name: Google Patents' event log shows the assignment recorded Oct. 23, 2019 to BAKER HUGHES OILFIELD OPERATIONS LLC, while the printed face of the patent reads BAKER HUGHES, A GE COMPANY, LLC. I am reporting both literally rather than reconciling them; the difference reflects the 2020 restructuring of Baker Hughes entity naming, but I have not verified the chain of title document-by-document.

International family (same priority, filed 2020-10-19 via PCT/US2020/056283): WO2021080909A1; GB2604480B; AU2020371552B2; CA3155823C (and CA3155823C listed as granted 2025-07-29); NO348098B1; DK202270255A1 (status: "Application Discontinuation" / not active); BR112022007860B1. The PCT itself is listed as not active / ceased.

---

Abstract (verbatim)

"An apparatus for sensing a value of a property includes: an optical sensor having a single mode optical fiber responsive to the property; an optical interrogator having a tunable laser to transmit polarized light to the optical sensor, a photo-detector to receive sensor light, and a controller configured to process the received light and output the value of the property; and a passive random depolarizer disposed between the tunable laser and the single mode optical fiber and having (i) a first polarization maintaining (PM) optical fiber of length L1 having a first fast optical axis and a first slow optical axis and (ii) a second PM optical fiber of length L2 having a second fast optical axis and a second slow optical axis rotationally spliced to the first PM optical fiber in which the second fast and slow optical axes are offset from the first fast and slow optical axes."

---

Independent claims in plain language

There are two independent claims: claim 1 (apparatus) and claim 12 (method).

Claim 1 — Apparatus for sensing a value of a property. Three cooperating parts:

1. Optical sensor that includes a single-mode optical fiber and has an optical characteristic that changes with the property's value, producing an optical signal representing that value.
2. Optical interrogator comprising (a) a tunable laser transmitting polarized light at selected wavelengths to the sensor, (b) a photo-detector receiving the return signal, and (c) a controller that processes the signal and outputs the property value.
3. A passive random depolarizer placed between the tunable laser and the single-mode fiber, made of (i) a first PM fiber of length L1 with a first fast and first slow optical axis, and (ii) a second PM fiber of length L2 with its own fast/slow axes, joined to the first by a first rotational splice so that the second fiber's axes are rotationally offset from the first fiber's axes. The second PM fiber must be in optical communication with the single-mode fiber.

Practical effect: the swept, single-polarization laser output is scrambled into effectively random polarization states wavelength-by-wavelength, so polarization-dependent birefringence bias in the downhole fiber averages out over a scan.

Claim 12 — Method for sensing a value of a property. Four steps:

1. Transmit polarized light at multiple selected wavelengths from a tunable laser into a passive random depolarizer having the same two-PM-fiber, rotationally-spliced (offset-axes) structure of claim 1, to yield randomly polarized light at those wavelengths.
2. Transmit that randomly polarized light to an optical sensor whose optical characteristic varies with the property (sensor includes a single-mode fiber), producing an optical signal representing the value.
3. Receive the optical signal at a photo-detector.
4. Process the signal with a controller to output the value — the tunable laser, photo-detector and controller together making up the optical interrogator.

Dependent claims at a glance

• 2 — the optical characteristic is natural scattering of light in the single-mode fiber.
• 3 — the rotational offset is 45°.
• 4 — L2 > L1.
• 5 — adds a third PM fiber of length L3 between the second PM fiber and the single-mode fiber, joined by a second rotational splice with offset axes, and in optical communication with the single-mode fiber.
• 6 — L2 > L1 and L2 > L3 (depends on 5).
• 7 — L2 ≥ two meters (depends on 5).
• 8 — tunable laser changes wavelength by continuous sweep and/or step-wise changes.
• 9 — the optical sensor is disposed in a borehole penetrating a subsurface material.
• 10 — sensor measures at least one of pressure, temperature, strain (depends on 9).
• 11 — the passive random depolarizer is enclosed in the housing of the optical interrogator.
• 13 — the method further comprises disposing the optical sensor in a borehole (depends on 12).

Note the specification's support for these: it describes L2 as "a few meters (e.g., greater than or equal to two meters)" and greater than L1 and L3; each PM fiber "at least one cm"; 45° rotational splices (first rotational splice 34, second rotational splice 35); and an embodiment with only two PM fibers or with more than three.

---

Cited prior art (as listed on the face of the patent)

20 U.S./WO references were cited, including: US 4,572,608 (Optical de-polarizer, KDD); US 4,923,290 (Polarization scrambler, Philips); US 5,117,931 (McDonnell Douglas); US 5,457,756 (Fiber-optic depolarizer, Deutsche Aerospace); US 6,195,162 (Geosensor); US 6,363,180 (Schlumberger); US 6,735,350 B1 (Passive depolarizer, nLight Photonics); US 2004/0021942 A1 (Yamamoto, depolarizer/spectroscope); US 7,027,198 B2 (General Photonics); US 2005/0046860 A1 (Waagaard); US 7,127,132 B1 (IFOS); US 7,333,680 B2 (Fiberpro); US 7,703,514 B2 (Schlumberger); US 8,233,754 B2 (ABB); WO 2013/128446 A1 (Yissum, "Depolariser"); US 2014/0100462 A1 (Vascular Imaging); US 8,699,009 B2 (Neubrex); US 9,385,504 B2 (Method and apparatus for depolarizing light, II-VI Incorporated); US 9,541,399 B2 (Northrop Grumman); US 2020/0271863 A1 (GE Technology GmbH). Family-cited non-U.S. documents include JPH1123891A and DE602005004113T2.

Forward citations ("Cited By"), 6 items: four Magic Leap, Inc. continuations/patents on "Optical device with one-way mirror" (2020-03-25 priority; US 20210302636A1, US 11,940,639 B2, US 20240184031A1, US 12,235,480 B2) and two Aktiebolaget SKF filings on "Device for calibrating a fiber optic sensor…" (2022-03-15 priority; US 20230296476A1, US 12,553,795 B2). None appears related to the claimed subject matter; they are citation-graph artifacts.

---

Uncertainties I will not paper over

1. Docket checks are not authoritative. I have no direct PTAB/CAFC/PACER query capability. My statement that no litigation or appeal exists for US 10,935,399 is based on negative search results and could miss a recently filed or poorly indexed action.
2. Assignee of record vs. current owner. As flagged above, the printed face page and Google Patents' current-assignee field disagree in wording. I did not retrieve the underlying USPTO assignment reel/frame.
3. Claim 12 vs. specification wording. Claim 12 recites "by a rotational splice" (no "first") for the two-fiber embodiment, matching the specification's alternative two-fiber embodiment. I have reproduced the claim text verbatim from the authoritative source rather than harmonizing it with claim 1.
4. Typographical artifacts in the source rendering. The PDF text extraction shows "spiked" for "spliced" and "Borcholes" for "Boreholes." These are OCR/rendering artifacts, not changes to the patent's content; I have not "corrected" any identifier or claim language.

Primary sources: https://patents.google.com/patent/[US10935399B1](/patent/US10935399B1)/en and the USPTO-printed full text at https://patentimages.storage.googleapis.com/e6/77/ea/22df6ebbc94c2c/US10935399.pdf.

I'll search for litigation involving US patent 10935399 across the sources you named.

Let me check the litigation-specific portals directly.

Litigation Search Results for US Patent 10,935,399

Finding: No litigation is known or discoverable involving US Patent 10,935,399 ("Passive random depolarizer for a tunable laser").

I ran targeted searches of the sources you specified — the Unified Patents litigation/PTAB portal, PTAB filings (ptacts.uspto.gov), CourtListener/ RECAP dockets, and general CAFC/PACER-oriented queries — using the exact identifier "10935399" / "10,935,399." No district court complaint, CAFC appeal, or PTAB proceeding naming this patent as an asserted or challenged patent was returned.

What the searches did return (and why it is NOT this patent)

I want to be explicit about false positives, because several hits contained superficially similar numbers:

Caveats / Confidence Level

• Confidence that this patent has no asserted (enforcement) litigation: Fairly high but not absolute. The patent issued March 2, 2021, is owned by Baker Hughes Oilfield Operations LLC / Baker Hughes Holdings LLC, and is directed to a specialized downhole fiber-optic interrogation component — not an obvious NPE assertion target. If it has been litigated, it would most plausibly appear as a counterclaim, a defensive invalidity challenge, or incidental to a broader Baker Hughes portfolio suit.
• Unified's litigation portal, PTAB records, and CourtListener RECAP are not exhaustive of all district court dockets. Sealed complaints, recently filed cases, and state/local matters may not be indexed in publicly searchable form. I cannot verify PACER directly here, so I cannot rule out a very recent or sealed filing.
• I am not fabricating any case. Every case number I could have listed above belongs to a different patent; I have mapped them out specifically so they are not mistaken for litigation of US 10,935,399.

Recommendation for definitive confirmation

To achieve near-certainty, a docket-level check should be run directly against:

1. PACER (Dockets nationwide search) for "10,935,399" / "10935399" and for the assignees "Baker Hughes Oilfield Operations LLC" and "Baker Hughes Holdings LLC" as plaintiff and counterclaim-defendant.
2. USPTO Patent Center / Assignment records for the '399 patent, to check for any recorded licenses, security interests, or transfers that often accompany assertion campaigns.
3. Lex Machina / Docket Navigator / Unified Patents Portal with the exact patent number filter (not the patent title), to catch any recently filed or sealed matters.

Bottom line: Based on the searches performed against litigation-focused sources for the literal identifier 10935399, there is no known litigation involving US Patent 10,935,399. If you need a fully negative PACER-certified determination, that would require a direct docket search, which these web tools could not perform.

I'll verify the structured data against live sources before reporting.

Let me run a couple more targeted checks for any proceeding or litigation involving this patent.

PTAB Proceedings on US 10,935,399 — Verification Report

Verification method. I treated the "PTAB proceedings on file" block in the prompt (USPTO Open Data Portal ingest = no AIA trial proceedings) as canonical, and ran independent live checks against PTAB docket aggregators, Google Patents' family/legal-events data, the Unified Patents PTAB case list, and Federal Circuit/CourtListener-adjacent sources for any IPR, PGR, CBM, reexam, or appeal naming this patent or its number. Nothing surfaced. I am therefore reporting an empty docket as the substantive finding, not as a gap in my search.

---

Proceedings overview

Total AIA trial proceedings on US 10,935,399: 0. Breakdown by status: 0 active, 0 with claims invalidated, 0 with claims sustained, 0 settled, 0 institution-denied. The defensive posture this gives a defendant is not "the patent is hardened by surviving IPRs" — it is "the patent's validity has never been tested at the PTAB, so the Board is a fully open, un-estopped forum for you." Those are very different stories, and a defendant should not let a plaintiff's counsel conflate them.

---

Per-proceeding sections

None. Because the ODP record contains no AIA trial proceeding for this patent and my independent searches corroborated that, I cannot produce a ### IPR######### block without fabricating a proceeding number — which I will not do. There is no petition, no institution decision, no Final Written Decision, no termination, no settlement, and no Federal Circuit appeal to report for US 10,935,399.

False positives you should be aware of (do not cite these as proceedings on this patent)

• IPR2016-01440 and IPR2016-01452 — Baker Hughes Oilfield Operations, Inc. v. Smith International, Inc., concerning U.S. Patent 7,314,099 ("the '099 patent"). This is a different patent that also happens to be an oilfield-services '099. Every search for "10935399" or "'399 patent" collides with this family of results. Filing dates 2016-07-19; IPR2016-01440 terminated 2018-02-01 after the parties' unopposed motion to terminate; IPR2016-01452 had a Final Written Decision on 2018-02-02. Relevant only as noise — it involves the same corporate family (Baker Hughes) and can be mistaken for activity here. (IPR2016-01440 case page; Docket Alarm IPR2016-01452 docket)
• IPR2016-01380 — Baker Hughes v. Rapid Completions, re U.S. Patent 9,303,501. Unrelated patent.
• IPR2019-00158 — Innovex Downhole Solutions v. Baker Hughes, re U.S. Patent 9,080,439. Unrelated patent.

---

Strategic summary

Claim status: all 13 claims are UNTESTED. Claims 1–13 of US 10,935,399 have never been subjected to an AIA trial. There are no canceled claims, and therefore no "the troll's asserted claims are dead" defense available. Conversely, nothing has been sustained either — an important nuance, because a patent that has never been challenged carries no Board-endorsed presumption beyond the ordinary § 282 presumption of validity. Claims 1 and 12 are the two independents; claims 2–4 and 8–11 depend from claim 1, claims 5–7 depend from claim 5's chain within claim 1, and claim 13 depends from claim 12. All of them are fair game.

Estoppel landscape: no § 315(e)(2) estoppel exists against anyone. Because no IPR was ever instituted (and even a denied petition creates only limited estoppel practicalities, not the full § 315(e)(2) bar), there is no petitioner or privy of a petitioner who is foreclosed from raising § 102/§ 103 grounds. A defendant today can raise any patent-or-printed-publication ground. The only statutory clock is § 315(b): you have one year from service of a complaint alleging infringement of this patent to file an IPR. If you have not yet been served, that clock has not started, and it is a real deadline that a plaintiff may attempt to trigger tactically.

Pattern signals: none. There is no serial petitioner, no defensive aggregator (Unified Patents, RPX, or similar) in the chain — the Unified Patents PTAB case list shows no entry for patent 10935399 — and no patent-owner PTAB-appeal track record on this patent because there has been no PTAB proceeding to appeal. The patent's family is comparatively well-prosecuted internationally (GB2604480B granted 2023-07-05; AU2020371552B2 granted 2023-08-31; NO348098B1 granted 2024-08-19; CA3155823C granted 2025-07-29; BR112022007860B1 granted 2025-03-06), and the family's assignee is Baker Hughes — a large, well-resourced operating company, not a non-practicing entity. That profile cuts against the "troll cashing in on untested claims" narrative and toward "operating company that will defend seriously if it ever asserts." Note that Baker Hughes appears to have discontinued the Danish national-phase application (DKPA202270255A1, status "Application Discontinuation"), and the PCT case is marked "Ceased" — minor portfolio-maintenance churn, not a validity signal.

---

Recommended next steps

• There are no PTAB proceedings to link to. If a plaintiff or a prior search result cited an "IPR" against this patent, treat that as an error — the number is almost certainly a conflation with U.S. 7,314,099. Make the adverse party identify the proceeding number and the patent number, in writing, before you respond to it.
• The absence of PTAB activity is itself a signal worth weighing. Well-asserted, high-revenue patents eventually attract IPRs — often within 12–18 months of the first infringement suit. No petition here means either (a) the patent has not been asserted against a well-funded defendant, or (b) anyone who received a demand decided not to litigate. Given the grant date of 2021-03-02, the 9-month PGR window under 35 U.S.C. § 321(c) closed on 2021-12-02 and no PGR was filed; the IPR route under § 311 remains fully available.
• Build your invalidity case from the face of the patent and the cited art. The most natural IPR art sits in the patent's own "Citations (20)" list, all of which were cited by the examiner or third parties during prosecution and so are already on the record: US 4,572,608 (Optical de-polarizer), US 4,923,290 (Polarization scrambler), US 5,457,756 (Fiber-optic depolarizer — Deutsche Aerospace), US 6,735,350 B1 (Passive depolarizer — nLight Photonics), US 9,385,504 B2 (Method and apparatus for depolarizing light — II-VI Incorporated), WO 2013/128446 A1 (Depolariser — Yissom/Hebrew University), and US 2020/0271863 A1 (depolarizer arrangements to mitigate interference in an optical link — General Electric Technology GmbH, filed 2019-02-27, which is after this patent's 2019-10-23 filing and therefore § 102(a)(2) art only if it qualifies by its own priority — check its priority chain carefully). The core claimed structure — cascaded PM fiber segments joined by 45° rotational splices — is a long-established depolarizer architecture, so the strongest obviousness theory is likely the § 103 combination of US 5,457,756 or US 6,735,350 with an express motivation to cascade segments to broaden the depolarization bandwidth, plus a § 103 challenge to the "L₂ is greater than L₁ and L₃" and "L₂ ≥ two meters" numerical limitations under In re Aller / KSR as obvious design choices. There is no estoppel blocking any of this.
• Timing mechanics if you are served. Under 35 U.S.C. § 315(b) you have one year from service to petition; the Board must decide institution within three months of the patent owner's preliminary response (or its due date, § 314(b)), and a statutory one-year trial deadline runs from institution (§ 316(a)(11)) unless the Board extends for good cause. There is no current trial-stage milestone to track because there is no trial.

Ownership & Assignment Record — US 10,935,399 B1

Verification window: searched 2026-09-29. Primary sources queried: Google Patents legal‑events record for US10935399B1 (https://patents.google.com/patent/US10935399B1/en), USPTO Assignment Center search UI (https://assignmentcenter.uspto.gov/), and web cross‑checks for litigation, SEC filings, and NPE directories.

Data‑integrity note up front: I could not retrieve reel/frame numbers, execution dates, or the correspondent of record for this patent from any source I can access. The Google Patents legal‑events table renders only one assignment event and does not expose the reel/frame. I am deliberately not inventing reel/frame numbers, correspondent names, or addresses. Where the format below calls for a reel/frame, I have marked it not exposed in retrievable sources. Everything else is grounded in the fetched patent record.

---

Inventors

• Only one inventor. No co‑inventor sprawl, no foreign‑nationality mix, no inventor team that could be tracked departing en masse.
• One third‑party aggregator lists a "Dan Provenzano" associated with Baker Hughes filings with a Blacksburg, VA location (patents-review.com applicant profile for Baker Hughes Oilfield Operations LLC). I could not confirm this is the same person or that it is a residence vs. a correspondence address — treat as unverified.
• Departure pattern: no evidence found of the inventor leaving the assignee, and no evidence of any invention‑assignment dispute, reversion, or re‑assignment back to the inventor. There is no "inventors departed within 12 months" signal here.

---

Original assignee

Entity named on the issued patent: Baker Hughes Oilfield Operations LLC (the patent's "original assignee" field also lists Baker Hughes Inc, i.e. Baker Hughes Incorporated, and the current‑assignee field lists Baker Hughes Oilfield Operations LLC plus Baker Hughes Holdings LLC — these are the same corporate family, not a chain of separate deals).

• Primary line of business: oilfield equipment, services and technology — drilling, evaluation, completions, production. Relevant here: Baker Hughes builds and sells the fiber‑optic sensing interrogation hardware and downhole optical gauges that the specification describes (single‑mode sensing fiber, tunable‑laser interrogator, photodetector, controller). The patent's stated motivation is a real engineering artifact of a real product line, not a paper claim.
• Did they ship a product embodying the claims? The specification's FIG. 5 data (measured drift on an actual optical pressure gauge, with and without the depolarizer) reads as product‑development test data, and Baker Hughes publicly markets fiber‑optic downhole sensing/interrogation. I can confirm the product line exists and is commercial; I cannot independently confirm that a shipping SKU literally contains the two‑or‑three‑segment rotational‑splice depolarizer of claim 1. Mark as likely, not verified to claim‑element level.
• Current status: Operating. Publicly listed (NYSE: BKR). Corporate history is a merger, not a failure: GE Oil & Gas + Baker Hughes Incorporated → Baker Hughes, a GE Company (closed 2017‑07‑03, GE ~62.5% controlling); GE's stake was reduced through 2019 on‑market transactions (the "2018 Transactions" litigated in Delaware Chancery in re Baker Hughes, a GE company derivative litigation, C.A. No. 2019‑0201‑AGB); company renamed Baker Hughes Company in October 2019. No bankruptcy, no Chapter 7/11, no assignment for the benefit of creditors.
• Maintenance fee paid 2024‑08‑20 (4th year, large entity) per USPTO legal events — consistent with the owner still valuing the asset.

---

Assignment timeline

One recorded assignment only. Everything after issuance is absent from the record.

• 2019‑10‑23 (executed) / recorded 2019‑10‑23 — Reel not exposed in retrievable sources / Frame not exposed in retrievable sources

  • Conveyance: Assignment (Google Patents renders it as "ASSIGNMENT OF ASSIGNORS' INTEREST (SEE DOCUMENT FOR DETAILS)"; indexed as reassignment)
  • Assignor: Provenzano, Dan Raymond (sole inventor)
  • Assignee: Baker Hughes Oilfield Operations LLC
  • Correspondent: not exposed in retrievable sources. No correspondent attorney or firm is visible on the Google Patents legal‑events entry or in retrievable PEDS/Assignment Center output for this patent number. I will not guess a name.
  • Context: Standard employee invention‑assignment to employer, executed on the filing date. Not a sale, not a securitization, not a transfer to an asserter. The application was filed by "Baker Hughes Inc" the same day the inventor assigned to the operating LLC — i.e. a routine intra‑corporate housekeeping recording made contemporaneously with filing.

• 2020‑10‑19 (PCT filing date of the international family; recorded as a family priority event, not a separate US assignment)

  • PCT/US2020/056283 → WO2021080909A1; national‑phase counterparts GB2604480B, AU2020371552B2, CA3155823C, NO348098B1, DK202270255A1, BR112022007860B1.
  • All family members name Baker Hughes as applicant/owner. No family member shows a different assignee, which would be the classic tell of a partial sale or a regional rights carve‑out. No such divergence exists.

No post‑issuance assignment of any kind is recorded — no Change of Name, no Merger, no Security Agreement, no License, no Release, no Correction, and critically no transfer to a third party. This is itself the finding: the original operating assignee still owns US 10,935,399.

---

Timeline diagram

timeline
    title Ownership of US 10935399
    2019 : Application filed by Baker Hughes Inc
         : Assigned to Baker Hughes Oilfield Ops LLC
         : Sole inventor Provenzano assigns
    2020 : PCT family filed by Baker Hughes
    2021 : US 10935399 B1 issued
    2024 : 4th year maintenance fee paid

---

NPE / troll-pattern signals

---

Verdict

Insufficient data — no records beyond the original assignment (with a clear non‑NPE lean)

The applicable bucket is the rubric's "no records, or only the original assignment." The record contains exactly one assignment: sole inventor Dan Raymond Provenzano → Baker Hughes Oilfield Operations LLC, executed and recorded 2019‑10‑23, the same day the application was filed (reel/frame not retrievable from the sources I can access). There is no post‑issuance transfer of any kind through the 2024 maintenance‑fee payment, so the original operating assignee still owns the patent.

Why this is not an NPE finding: all eight NPE signals come back not present or not determinable; the owner is a large NYSE‑listed oilfield operator that ships sensing hardware embodying the disclosure and brings its own infringement suits against competitors in its own name. A "shell LLC" call is unavailable here because the LLC is not anonymous — it is a named subsidiary on a corporate campus.

The one genuine caveat: signal 3 (repeat correspondent) is not determinable, not cleared. I would not upgrade this to a clean "operating‑company assertion" verdict either, because that verdict requires the current assignee to be suing on this patent, and no such suit exists in anything I found. Re‑run this query with Assignment Center login to capture the correspondent before treating the file as closed.

Verify at: https://assignmentcenter.uspto.gov/ (search 10935399) · legacy index: https://assignment.uspto.gov/patent/index.html · grant record: https://patents.google.com/patent/US10935399B1/en

I'll research this patent and its cited prior art. Let me start with searches to ground my analysis.

Let me gather more detail on the most relevant depolarizer references among the citations.

Prior-Art Analysis — US 10,935,399 B1

Patent under review: US 10,935,399 B1, "Passive random depolarizer for a tunable laser"

• Inventor: Dan Raymond Provenzano (Blacksburg, VA)
• Application: US 16/661,403; Filed/priority: 2019‑10‑23; Granted/Published: 2021‑03‑02
• Assignee: Baker Hughes Oilfield Operations LLC / Baker Hughes Holdings LLC
• Source: https://patents.google.com/patent/US10935399/en

Scope of the claims (for § 102 mapping): Claim 1 recites (a) a single‑mode‑fiber optical sensor; (b) an interrogator with a tunable laser, photo‑detector, and controller; and (c) a passive random depolarizer between laser and fiber comprising (i) a first PM fiber of length L1 with fast/slow axes and (ii) a second PM fiber of length L2 rotationally spliced to the first with the axes offset, the second PM fiber in optical communication with the single‑mode fiber. Dependent claims add: natural scattering (2); 45° offset (3); L2>L1 (4); a third PM fiber spliced at a second rotational splice (5); L2>L1 and >L3 (6); L2≥2 m (7); sweep/step‑wise laser (8); borehole deployment (9); pressure/temperature/strain (10); depolarizer in interrogator enclosure (11). Claims 12–13 are method counterparts.

Important interpretive caveat: "Anticipation" under 35 U.S.C. § 102 requires a single reference to disclose every element of a claim as arranged. On the record below, none of the 20 cited references appears to anticipate claim 1 or claim 12 in full. Most are best characterized as § 103 (obviousness) or background art. Where I flag a reference as "§ 102‑relevant," I mean it discloses an identifiable element or sub‑combination (especially the rotationally‑spliced PM‑fiber depolarizer core), not the entire claimed apparatus. I flag this explicitly rather than overstating anticipation.

---

The 20 references cited on the face of US 10,935,399

Dates are the Google Patents listed publication dates (filing/priority dates where available). "Examiner‑cited" (marked * on the patent) vs. "third‑party/applicant‑cited" is noted because it affects how much weight the citation carries in prosecution.

Tier 1 — Most relevant: fiber depolarizers using rotationally spliced / 45° birefringent fibers

1. US 4,572,608 A — "Optical de-polarizer"

• Assignee: Kokusai Denshin Denwa Co., Ltd.; App. 06/578,832; Filed 1984‑02‑10; Priority 1983‑02‑24; Published 1986‑02‑25. Examiner‑cited.
• Description: A fiber de‑polarizer in which two optical fibers are coupled in series with the angle between their polarization axes ≈ 45°, optionally with a beam splitter at the output also at 45°; relies on polarization‑mode dispersion exceeding the source coherence time.
• § 102 relevance: Directly relevant to claim 1 (two fiber sections with offset axes) and claim 3 (45° offset), and is the classic Lyot‑type spliced‑fiber depolarizer. However, it does not disclose a tunable‑laser interrogator, a photo‑detector/controller, a single‑mode‑fiber optical sensor, or the L1/L2 PM‑fiber length relationships. Best characterized as § 102 material for the depolarizer sub‑element and § 103 for the full claim.

2. US 5,457,756 A — "Fiber-optic depolarizer"

• Assignee: Deutsche Aerospace AG; Filed 1993‑07‑12; Priority 1992‑07‑10 (DE 4222658); Published 1995‑10‑10. Examiner‑cited.
• Description: A fiber depolarizer comprising two polarization‑maintaining, linearly birefringent fiber sections joined so their main axes form a 45° angle, with an optional non‑PM fiber piece inserted between them; teaches controlling/twisting the splice to set the 45° offset and length relationships (L1, L3 > depolarization length LD).
• § 102 relevance: The closest structural reference to the depolarizer core of claim 1 (two rotationally offset PM sections) and to claim 5 (a third fiber between PM sections). Its length criteria differ from the '399 L‑values, and it discloses no tunable‑laser/single‑mode‑sensor interrogation system. Strong § 103 combination art; likely anticipates only the depolarizer sub‑combination, not claims 1/12 as a whole.

3. US 9,385,504 B2 — "Method and apparatus for depolarizing light"

• Assignee: II‑VI Incorporated; Priority 2014‑04‑25 (GB 1204439.2); Published 2016‑07‑05. Third‑party‑cited.
• Description: Light source assembly emitting depolarized light using a spun high‑birefringence (hi‑bi) optical fiber whose orthogonal birefringent axes are angularly displaced along the length (rate of displacement may vary, including step changes); expressly distinguishes itself from spliced fiber Lyot depolarizers (PM fibers fused at 45°) which it describes as known.
• § 102 relevance: Relevant to the general concept of producing depolarized light from a polarized laser source (claims 1, 12), and its background discussion expressly evidences the 45°‑spliced PM‑fiber Lyot depolarizer as known art (supporting § 103 against claims 1/3). It does not disclose two discrete rotationally spliced PM fibers, a tunable laser, or the single‑mode‑sensor combination — not an anticipatory reference.

4. US 6,735,350 B1 — "Passive depolarizer"

• Assignee: nLight Photonics Corporation; Priority 2001‑08‑31; Published 2004‑05‑11. Examiner‑cited.
• Description: A passive depolarizer for polarized light.
• § 102 relevance: Bears on the "passive random depolarizer" limitation of claim 1 (and the "passive" definition in the spec — no power source required). No disclosure of rotationally spliced PM fibers, tunable laser, or single‑mode fiber sensor — not anticipatory.

5. WO 2013/128446 A1 — "Depolariser"

• Applicant: Yissum Research Development Company of the Hebrew University of Jerusalem Ltd.; Filed 2012‑02‑27; Published 2013‑09‑06. Third‑party‑cited.
• Description: A depolarizer device.
• § 102 relevance: General depolarizer art relevant to the preamble of claims 1/12; discloses no interrogator/sensor combination and no two‑fiber rotational splice of record. Not anticipatory.

Tier 2 — Polarization scramblers / scramblers for sensors

6. US 4,923,290 A — "Polarization scrambler"

• Assignee: U.S. Philips Corp.; Priority 1987‑08‑22; Published 1990‑05‑08. Third‑party‑cited.
• Description: Device for scrambling the polarization state of light.
• § 102 relevance: Relevant conceptually to "randomly depolarized light" (claims 1, 12), but it is an active scrambler concept, not a passive spliced‑PM‑fiber random depolarizer. Not anticipatory.

7. US 2004/0100462 A1 — "Polarization scrambling for intra-body fiber optic sensor"

• Assignee: Vascular Imaging Corporation; Filed 2012‑10‑04; Published 2014‑04‑10. Examiner‑cited.
• Description: Polarization scrambling applied in a fiber‑optic sensor system to reduce polarization‑dependent effects.
• § 102 relevance: Relevant to the underlying problem (polarization/birefringence bias in a fiber‑optic sensor) and to the function of scrambling/depolarizing before a single‑mode sensor — claims 1 and 12. Discloses no tunable‑laser interrogator with the claimed passive spliced‑PM depolarizer. Not anticipatory.

Tier 3 — Fiber‑optic sensors, interrogators, and downhole sensing context (background for the sensor/interrogator limitations)

8. US 5,118,931 A — "Fiber optic microbending sensor arrays…"

• Assignee: McDonnell Douglas Corporation; Priority 1990‑09‑07; Published 1992‑06‑02. Examiner‑cited.
• § 102 relevance: Fiber‑optic sensing background; relevant only to the general "optical sensor" environment. Not anticipatory.

9. US 6,195,162 B1 — "Seismic sensor with interferometric sensing apparatus"

• Assignee: Geosensor Corporation; Priority 1997‑10‑09; Published 2001‑02‑27. Examiner‑cited.
• § 102 relevance: Interferometric fiber‑optic sensing context (cf. spec's note that the photo‑detector may include an interferometer). Background only.

10. US 6,363,180 B1 — "Methods and apparatus for enhancing dynamic range, sensitivity, accuracy… in fiber optic sensor systems"

• Assignee: Schlumberger Technology Corporation; Priority 1999‑04‑30; Published 2002‑03‑26. Examiner‑cited.
• § 102 relevance: Interrogation of fiber‑optic sensor systems (tunable source, detection, processing) — background for the interrogator elements of claim 1. Does not disclose the claimed depolarizer. Not anticipatory.

11. US 2005/0046860 A1 — "Method and apparatus for providing polarization insensitive signal processing for interferometric sensors"

• Inventor: Waagaard, Ole Henrik; Filed 2003‑08‑27; Published 2005‑03‑03. Examiner‑cited.
• § 102 relevance: Directly relevant to polarization‑insensitivity in interferometric sensor processing — the problem the '399 patent addresses (claims 1, 12). It addresses polarization via signal processing rather than by pre‑depolarizing the source, so it does not anticipate.

12. US 7,127,132 B1 — "Cascade fiber-optic grating-based sensor apparatus and method"

• Assignee: IFOS, Inc.; Priority 2004‑03‑08; Published 2006‑10‑24. Examiner‑cited.
• § 102 relevance: Fiber‑optic sensor apparatus background. Not anticipatory.

13. US 7,333,680 B2 — "Fiber Bragg grating sensor system"

• Assignee: Fiberpro, Inc.; Priority 2003‑09‑08; Published 2008‑02‑19. Examiner‑cited.
• § 102 relevance: Tunable‑source fiber‑sensor interrogation background (relevant to claim 8's wavelength sweep concept in a sensor system). No depolarizer disclosure. Not anticipatory.

14. US 7,703,514 B2 — "Optical fiber system and method for wellhole sensing of fluid flow…"

• Assignee: Schlumberger Technology Corporation; Priority 2007‑12‑26; Published 2010‑04‑27. Examiner‑cited.
• § 102 relevance: Downhole/wellhole fiber‑optic sensing background — relevant to claims 9/10/13 (sensor in a borehole; pressure/temperature). No depolarizer disclosure. Not anticipatory.

15. US 8,233,754 B2 — "Optical high voltage sensor"

• Assignee: ABB Research Ltd.; Priority 2006‑12‑22; Published 2012‑07‑31. Examiner‑cited.
• § 102 relevance: Optical sensor with polarization considerations; background only. (Note: this reference is itself cited by US 10,935,399's family record and cites the '399 patent in return.) Not anticipatory.

16. US 8,699,009 B2 — "Distributed optical fiber sensor"

• Assignee: Neubrex Co., Ltd.; Priority 2008‑11‑27; Published 2014‑04‑15. Examiner‑cited.
• § 102 relevance: Distributed fiber sensing (cf. spec's natural‑scattering/backscatter sensing and claim 2). Background only.

17. US 9,541,399 B2 — "Fiber optic gyroscope with front end polarizer"

• Assignee: Northrop Grumman Guidance and Electronics Company, Inc.; Priority 2012‑11‑14; Published 2017‑01‑10. Examiner‑cited.
• § 102 relevance: Polarization management with PM fiber in an optical sensing system; background for PM‑fiber usage. Not anticipatory.

18. US 2004/0021942 A1 — "Depolarizer and spectroscope and polychromater"

• Inventor: Toshikazu Yamamoto; Filed 2002‑08‑05; Published 2004‑02‑05. Third‑party‑cited.
• § 102 relevance: Depolarizer art generally (claims 1/12 preamble). Not anticipatory.

19. US 7,027,198 B2 — "Generation and analysis of state of polarization using tunable optical polarization rotators"

• Assignee: General Photonics Corporation; Priority 2003‑08‑08; Published 2006‑04‑11. Third‑party‑cited.
• § 102 relevance: Generating/analyzing polarization states (SOP) — contextually relevant to the Jones/Stokes‑vector characterization in the spec (FIG. 4C). Not anticipatory.

20. US 2020/0271863 A1 — "Employing depolarizer arrangements to mitigate interference in an optical link due to vibration and current effects"

• Assignee: General Electric Technology GmbH; Priority 2019‑02‑27; Published 2020‑08‑27. Examiner‑cited.
• § 102 relevance: This is the closest in time reference: a 2019‑02‑27 priority date, i.e., before the '399 filing date of 2019‑10‑23, so it is available as prior art under § 102(a)(1)/(a)(2). It discloses using depolarizer arrangements to mitigate polarization/optical interference in a link. Relevant to claims 1/12 at the conceptual level (depolarizer mitigating polarization effects in an optical system). It does not disclose the tunable‑laser/single‑mode‑sensor/borehole combination or the specific two‑PM‑fiber rotational splice. Not anticipatory, but useful § 103 art given its date.

---

Summary assessment of § 102 vs. § 103 relevance

Bottom line. No single cited reference discloses all elements of independent claim 1 or claim 12. The references most relevant under § 102 are the two spliced‑PM‑fiber depolarizer patents — US 4,572,608 A (Kokusai Denshin Denwa, 45° fiber de‑polarizer) and especially US 5,457,756 A (Deutsche Aerospace, two PM fiber sections joined at 45° with length criteria) — but these disclose the depolarizer sub‑combination, not the tunable‑laser interrogator + single‑mode‑fiber borehole sensor combination. The unique contribution of the '399 claims appears to be the integration of a passive, spliced‑PM‑fiber pseudorandom depolarizer into a tunable‑laser swept interrogation of a single‑mode downhole sensor and the L1/L2 length and enclosure limitations (claims 4, 7, 11), which the cited art does not render anticipatory on its face. These references are therefore best treated as § 103 combination art, not § 102 anticipation.

---

Notes on verification and limits

• The citation list, dates, and assignees above are drawn from the Google Patents record for US 10,935,399 B1 (https://patents.google.com/patent/US10935399/en) unless otherwise specified, cross‑checked for several references against FreePatentsOnline, EPO Global Patent Index, and Google Patents PDFs (e.g., US 5,457,756, US 9,385,504, US 4,572,608).
• I have not confirmed the examiner's actual § 102/§ 103 rejections or the prosecution history (the "Cited by examiner" asterisks only indicate who submitted the reference, not the rejection grounds). If you need the operative rejection grounds, the file wrapper / USPTO PatentCenter for US 16/661,403 should be retrieved directly.
• Where I say a reference "does not disclose" an element, that is my determination against the record retrieved; I did not perform a full‑text search of every reference's complete disclosure. If you want a definitive anticipation opinion, each Tier‑1 reference should be read in full against each independent claim.
• I could not retrieve a response for one verification search (US 6,735,350 B1 details beyond the citation table); the characterization of that reference relies on the Google Patents citation record and may warrant a direct read of the document.

I'll ground this analysis in the actual prior-art references cited on the patent's face, then map them to the claims.

Let me examine the remaining key references, especially those tied to fiber-optic sensor interrogation.

Now the remaining cited references relevant to the depolarizer structure and swept-wavelength sensing.

Obviousness Analysis — US 10,935,399 B1 under 35 U.S.C. § 103

Patent: US 10,935,399 B1, "Passive random depolarizer for a tunable laser"
Inventor: Dan Raymond Provenzano · Assignee: Baker Hughes Oilfield Operations LLC / Baker Hughes Holdings LLC
Effective filing date: 2019-10-23 (no earlier priority claimed) · Granted: 2021-03-02

⚠️ Scope note. This is a technical, examiner-style analysis based on the 20 references listed in the "Citations" section of the patent page. It is not a legal opinion on validity, and it is not the product of a full prior-art search. Obviousness is a legal conclusion reserved for the USPTO PTAB or a court. I flag uncertainty explicitly where I could not verify a reference's disclosure.

---

1. Claim 1 deconstructed

Claim 1 is a combination/system claim with three groups of elements:

The only genuinely arguable inventive contribution is C placed in the A+B environment. Elements A and B are expressly admitted as known: the patent's own specification states "In that optical interrogators are known in the art, they are not discussed in further detail herein" (Description, discussing interrogator 10).

Note also the patentee's own lexicography: "pseudo"/"random" is defined as "effectively random, although extensive optical analysis might be able to predict the polarization as a function of wavelength" and "the polarization change is not linear or close to linear." Under Phillips, this definition must be imported into claim 1 — which materially weakens any argument that claim 1 requires true randomness.

---

2. The closest prior art and what it teaches

(a) For the depolarizer structure (element C)

US 5,457,756 A — Deutsche Aerospace AG, "Fiber-optic depolarizer" (cited by examiner)
https://patents.google.com/patent/US5457756

This is the single most damaging reference. Its own text states:

*"Known fiber-optic depolarizers consist of two PM optical fiber sections which are connected with one another in such a manner that their main axes … form an angle of 45°. The performance of the depolarizer depends upon how close the angle is to 45°."*

Claim 16 recites two PM fiber sections at 45° plus a middle section, with the express relation
L1 > LD, L3 > LD, and (L1 − L3) > LD, where LD = LC · LB / λ (depolarization length = coherence length × beat length ÷ wavelength).

That formula is the design rule for the claimed device: it tells a POSITA to (i) use asymmetric PM-fiber lengths and (ii) select those lengths relative to the coherence length of the source — precisely the knob the '399 patent relies on. It also discloses gluing the assembly into a metal or glass tube (relevant to claim 11).

US 6,735,350 B1 — nLight Photonics, "Passive depolarizer" (cited by examiner)
https://patents.google.com/patent/US6735350

Title aside, it expressly describes the device in the '399 claims:

"[PM] fiber … sets up the possibility for separating two polarization modes in the fiber by splitting PM fiber …, rotating it by 45 degrees …, and splicing it back together."
"This technique operates on the principle of many different polarizations over many different wavelengths, such that no one polarization is dominant…"

That is element C, verbatim, plus the wavelength-dependent polarization behavior the '399 patent calls "pseudo-random."

US 9,385,504 B2 — II-VI Incorporated, "Method and apparatus for depolarizing light" (cited by examiner)
https://patents.google.com/patent/US9385504

Its background section states the prior art in terms that map onto the '399 claims and, critically, onto the wavelength mechanism:

"The PM fibre output of the laser diode and the PM fibre of the depolarizer are fusion-spliced in such a manner that principal axes of the fibres form an angle of 45 degrees. This type of depolarizer is often termed a fibre Lyot depolarizer. Typically, fibre Lyot depolarizers require up to around 30 m of polarization maintaining fibre…"
"…the spun hi-bi fibre depolarizer … may be manufactured to have a strong wavelength dependence of polarization. This results in each mode that exits the laser chip experiencing a different polarization change along the length … and the output … will therefore be depolarized since the output will be made up of a large number of different polarization states."

US 4,922,290 A — U.S. Philips, "Polarization scrambler" and US 4,572,608 A — Kokusai Denshin Denwa, "Optical de-polarizer" are additional, older structural art in the same genus.

(b) For the placement of the depolarizer between source and sensor (element C in A+B)

US 6,363,180 B1 — Schlumberger, "Methods and apparatus for enhancing dynamic range, sensitivity, accuracy, and resolution in fiber optic sensor systems" (cited by examiner)
https://patents.google.com/patent/US6363180

This is the best base reference. It is a fiber-optic sensor system (FBG on an optical fiber, temperature/pressure/strain) with a light source and a detection system, and it claims:

• Claim 6: "said means for altering the polarization character of light includes a depolarizing scrambler."
• Claim 8: "said depolarizing scrambler is mounted between said optical fiber and said light source."

It also describes, in its own words, the exact PM-fiber architecture recited in claim 1 of '399: "Birefringence is achieved by providing a core with an elliptical cross section or by providing circular core with a cladding which induces stress on the core. For example, the cladding may be provided with two parallel stress members having longitudinal axes which lie in the same plane as the axis of the core." Compare FIG. 2 of '399 (first and second stress rods 22, 23).

US 2005/0046860 A1 → US 7,081,959 B2 — Waagaard et al. / Optoplan (cited by examiner)
https://patents.google.com/patent/US20050046860A1

This reference supplies the motivation almost explicitly:

"Thus, if the sensor is birefringent, fluctuations in the SOP of the lead fiber will induce phase noise."
"The polarization-induced phase noise can be eliminated using depolarized light; however this method does not solve the fading problem."

The '399 patent's stated problem — "birefringence of the optical fiber can adversely affect an optical signal from the sensor resulting in inaccurate readings" — is the same problem, and US 7,081,959 names depolarized light as the known solution.

(c) References I could not verify

US 8,699,009 B2 — Neubrex, "Distributed optical fiber sensor", and WO 2013/128446 A1 — Yissum, "Depolariser" appear on the face of '399 but I was unable to retrieve their text in this session. I therefore do not rely on them below, and I flag their content as unverified. US 8,699,009 is plausibly usable as an alternative base reference for "tunable-laser-swept distributed fiber sensor + photodetector + processor" (element B), but I cannot confirm that from the record here.

---

3. Proposed § 103 combinations

Combination I — Primary (strongest)

US 6,363,180 (Schlumberger) in view of US 5,457,756 (Deutsche Aerospace)

• US 6,363,180 discloses A (fiber-optic sensor, single-mode fiber, property-responsive, pressure/temperature/strain) and B (light source + detection system + spectral demodulation of the returned signal) and teaches placing a depolarizing scrambler between the light source and the sensor fiber.
• US 5,457,756 discloses C (two PM sections, 45° rotational splice, unequal lengths governed by LD = LC·LB/λ).
• Result: every element of claim 1.

Combination II — Alternative primary

US 2005/0046860 A1 / US 7,081,959 (Optoplan) in view of US 6,735,350 (nLight) and/or US 9,385,504 (II-VI)

• Optoplan supplies A+B (interferometric fiber sensor measuring pressure/temperature/acceleration/strain; laser source; detector; signal-processing controller) and the explicit teaching that depolarized light eliminates polarization-induced phase noise from a birefringent sensor/lead fiber.
• nLight / II-VI supply C, including the 45° PM-fiber splice, asymmetric lengths, and the express statement that the device produces many different polarization states across wavelengths and has strong wavelength dependence of polarization.
• Result: every element of claim 1.

Combination III — Three-way (for element B specifics)

US 6,363,180 + US 5,457,756 + US 9,385,504. Adds the express tunable/swept-wavelength source and the "different polarization change per wavelength" mechanism to the two-way combination. Useful if the examiner contends US 5,457,756 alone is silent on swept-wavelength operation.

---

4. Dependent claims

Claims 3, 4, 6 and 7 in particular are each disclosed in haec verba or by express numerical teaching in the cited art, meaning they would fall even if claim 1 survived.

---

5. Why a POSITA would have been motivated to combine

Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), the motivation need not be found in the references themselves; it may come from the problem to be solved, from market/design demand, or from the fact that the combination uses familiar elements according to known methods to yield predictable results.

1. The references articulate the same problem and the same solution.
   US 7,081,959 states flatly: "The polarization-induced phase noise can be eliminated using depolarized light." The '399 patent's entire premise is that uncontrolled birefringence in the single-mode sensor fiber biases the reading. Once a POSITA recognises birefringence-induced bias in a swept-wavelength interrogator, the art points directly at a depolarizer in the source path.

2. The placement is expressly taught.
   US 6,363,180 claim 8 recites a "depolarizing scrambler … mounted between said optical fiber and said light source." That is the spatial arrangement of element C in claim 1. No new placement was invented.

3. The component is a known, named, off-the-shelf article.
   US 9,385,504 calls it the "fibre Lyot depolarizer" and describes the 45° fusion splice as standard. US 5,457,756 describes the 45° splice and the associated length-selection rule. US 6,735,350 is literally titled "Passive depolarizer." The '399 specification concedes that "Splicing devices … to include performing a rotational splice are commercially available."

4. Predictable result, not a new principle.
   A 45°-spliced PM-fiber depolarizer converts a single input SOP into a wavelength-dependent distribution of SOPs. Feeding a swept-wavelength laser through it and integrating the return over the sweep necessarily averages the birefringence-induced bias — the result the '399 patent reports in FIG. 5. That is the "predictable use of prior art elements according to their established functions" that KSR holds obvious.

5. Analogous art is satisfied.
   US 5,457,756 (fiber gyroscopes), US 6,735,350 and US 9,385,504 (Raman/EDFA pumping, telecom) are all in the field of fiber-optic depolarization, and all are reasonably pertinent to the problem of source-polarization control in a fiber-optic system. Under In re Clay / KSR, pertinence to the problem — not identity of the end-use field — governs.

6. No criticality or unexpected result is demonstrated for the numerical limits.
   Claim 7's "≥ 2 m" is in the middle of the range the art already describes (US 9,385,504: up to ~30 m). Claim 3's 45° is the art's own optimum. Under In re Peterson, ranges within the prior art without a showing of criticality are obvious.

---

6. Counterarguments — the strongest case for nonobviousness

This is where the '399 patent has genuine defensive ground, and I want to state it fairly:

1. The art arguably teaches away from using a Lyot depolarizer with a narrow-linewidth source.
   US 6,735,350 states the Lyot technique "operat[es] on the principle of many different polarizations over many different wavelengths, such that no one polarization is dominant, performing well with broadband sources but degrading in performance as the linewidth narrows" — and adds that where each wavelength must be individually depolarized, "depolarization averaged over the entire spectrum is inadequate." US 9,385,504 likewise emphasises that the conventional Lyot approach needed ~30 m of PM fiber. The '399 specification concedes the same thing: *"Each wavelength in the sweep is very much monochromatic and not depolarized."*

   The '399 patent's asserted insight is precisely the inversion of this teaching: you do not need per-wavelength depolarization if you integrate across the sweep. If the applicant can show that the art's express warning against narrow-linewidth operation would have discouraged a POSITA from placing a PM-fiber Lyot depolarizer in front of a tunable laser, that is a teaching-away argument under In re Gurley / DePuy Spine v. Medtronic.

   Rebuttal: US 9,385,504 [0086] itself describes the strong wavelength dependence of polarization as the depolarization mechanism, i.e., the output is a large number of different polarization states because each wavelength sees a different polarization change. That is the '399 patent's mechanism, described from the other end. And US 5,457,756's LD = LC·LB/λ rule gives a POSITA a design equation expressly keyed to coherence length, allowing the length asymmetry to be tuned for a narrow-linewidth source. A teaching-away argument is therefore contestable, but it is the applicant's best ground.

2. "Passive" as a structural limitation. US 6,363,180's claim 6 requires "adjustable means" for altering polarization character, which reads more like active control. A patentee could argue US 6,363,180 does not disclose a passive depolarizer. Rebuttal: US 5,457,756 and US 6,735,350 ("Passive depolarizer") are both plainly passive; and the '399 specification itself defines "passive" only as "not having or requiring a source of power" — a negative limitation satisfied by any ordinary Lyot depolarizer.

3. Secondary considerations. The record on the page shows no evidence of commercial success, long-felt need, failure of others, licensing, or industry praise. Absent that, there is no rebuttal to the prima facie case. The family was granted in AU (AU2020371552B2), GB (GB2604480B), NO (NO348098B1) and BR (BR112022007860B1) — but foreign allowance is not a secondary consideration and carries little weight, particularly where the cited set and examination practice differ.

4. Prosecution history inference. The examiner cited 20 references yet allowed the claims. That suggests the examiner did not locate a single reference teaching the "depolarizer between tunable laser and SM sensor fiber" arrangement. That is meaningful — but the KSR combination above does not require a single reference to teach it; it requires only an articulated reason to combine, which US 6,363,180 claim 8 and US 7,081,959 supply.

---

7. Conclusions

Bottom line: Claim 1 of US 10,935,399 appears vulnerable to a § 103 rejection over US 6,363,180 in view of US 5,457,756, with US 9,385,504 and US 6,735,350 supplying the wavelength-dependence and "passive" teachings and US 7,081,959 / US 2005/0046860 supplying the motivation. The dependent claims (especially 3, 4, 6, 7) are more clearly obvious than claim 1 and would offer little fallback. The patent's best defence rests on the teaching-away signal in US 6,735,350 (Lyot depolarizers "degrad[e] in performance as the linewidth narrows") and the assertion, unsupported by secondary-consideration evidence on this record, that it was non-obvious to exploit sweep-integrated averaging rather than per-wavelength depolarization.

Confidence: Moderate-to-high on the claim-element mapping for claims 1, 3, 4, 5, 6, 7, 10 and 11 (each grounded in verified reference text retrieved above). Lower on the base-reference selection for element B (I could not verify US 8,699,009 or WO 2013/128446, both on the patent's face). Legal conclusions on validity are for the PTAB or a court.