US 10578438

I'll research this patent. Let me query for its details and any 2026 litigation activity.

Let me check for any litigation or CAFC activity specifically involving this patent.

US 10,578,438 B2 — Patent Summary

Source note: The summary below is grounded in the full patent text (Google Patents, https://patents.google.com/patent/US10578438/en) plus corroborating search results. I did not find any USPTO or CAFC 2026 docket activity for this number (see §Search results below for the limits of that finding).

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Bibliographic data

Priority-document identifier discrepancy (noted literally, not corrected): the specification's CROSS-REFERENCE section recites "Singapore application No. 102016010540 filed on Feb. 12, 2016," while the Google Patents family table lists the priority document as "SG10201601054U." These two strings do not match; I am reporting both as-is and do not assert which is authoritative.

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Abstract (as issued)

Various embodiments may provide an optical gyroscope. The optical gyroscope may include a ring resonator, an input source configured to generate or provide a first light beam and a second light beam to the ring resonator, and a switching pathway having an input end and an output end coupled to the ring resonator, and may include a plurality of switches. The optical gyroscope may include a control circuit configured to control the plurality of switches to allow the first light beam to propagate from the input end to the output end along the switching pathway during a first time interval, and allow the second light beam to propagate from the input end to the output end along the switching pathway during a second time interval. The optical gyroscope may additionally include a detector loop configured to receive the first light beam and the second light beam from the ring resonator.

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Plain-language overview

The patent is a Sagnac-effect integrated optical gyroscope (IOG). Its problem statement: in a resonant ring gyroscope the clockwise (CW) and counter-clockwise (CCW) beams circulate simultaneously, and their interaction causes lock-in/mode-locking (backscatter, cross-talk, beat effects) that degrades rotation sensing. Prior art cited in the background includes US 5,969,816 ("Direction switched mode-locked laser gyroscope"), thin-film electro-optic switches that alternate beam injection into a delivery loop, and US 8,031,343 (Bae, "segmented paths" waveguide gyro).

The disclosed fix: make the two counter-propagating beams take turns. A "delivery loop" / "switching pathway" is coupled between two points of the ring resonator and contains two (or more) synchronized optical switches plus an optical amplifier (e.g., a semiconductor optical amplifier, SOA). During a first half-period only the CCW beam is switched into the delivery loop and amplified (compensating round-trip loss, keeping it on resonance); the CW beam is blocked and dies out for lack of gain. During the second half-period the roles swap and only the CW beam survives. The beams therefore never coexist in the resonator. Because they are now temporally separated, a time delay module in the detector loop delays the earlier beam so the two can be optically combined at a combiner and their interference fringe pattern detected by a photodetector. Rotation rate is inferred from the beat/interference frequency, per Δf = 4A/(λL)·Ω, where A is enclosed area, L optical path length, and λ the operating wavelength. Optional features: a phase modulator on the ring to compensate thermally induced output drift (for bias stability); a quad flat no-lead (QFP) package; and system-in-package (SiP) integration of the gyro chip with read-out circuits on a silicon substrate.

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Independent claims in plain language

Claim 1 — Optical gyroscope (apparatus). Requires, in combination:

• a ring resonator;
• an input source that provides a first light beam and a second light beam to the ring resonator;
• a switching pathway having an input end and an output end both coupled to the ring resonator, where the pathway contains a plurality of switches;
• a control circuit that controls those switches to let the first beam travel input→output along the pathway during a first time interval, and to let the second beam travel input→output along the pathway during a second time interval; and
• a detector loop that receives both beams from the ring resonator, is configured to remove a time delay between the first and second beams, and then combines them to produce an interference pattern.
  The time-delay-removal-plus-recombination function of the detector loop is the point of novelty that distinguishes this claim from a conventional switched/resonant IOG.

Claim 18 — Electro-optic system. Same gyroscope content as claim 1 (ring resonator, input source for two beams, switched pathway with plurality of switches, timing control circuit, detector loop with time-delay removal and interference combination), but framed as a system that additionally requires a substrate with the optical gyroscope on the substrate and a readout circuit on the substrate coupled to the optical gyroscope.

Claim 20 — Method of forming an optical gyroscope. A fabrication/assembly method comprising: providing a ring resonator; providing an input source configured to generate first and second light beams to the ring resonator; coupling a switching pathway (input end and output end) to the ring resonator, the pathway comprising a plurality of switches; providing a control circuit configured to gate the first beam along the pathway during a first time interval and the second beam during a second time interval; and providing a detector loop configured to receive both beams from the ring resonator, remove a time delay between them, and combine them to produce an interference pattern after the delay is removed.

Selected dependent claims for context: cl. 2 (first/second optical switches each with a first branch for the first beam and a second branch for the second beam); cl. 3–4 (the inactive branch blocking the other beam); cl. 5 (optical amplifier in the pathway, per-interval gain); cl. 6 (amplifier does not amplify the non-selected beam, letting it vanish); cl. 7–8 (amplifier between the two switches, coupled by first/second waveguides); cl. 9 (first/second optical couplers tying the switches to the ring); cl. 10 (detector for the interference pattern); cl. 11 (time delay module); cl. 12–13 (optical combiner and output optical coupler); cl. 14 (pathway spans a ring diameter); cl. 15 (detector loop at a third point equidistant from the two coupling points); cl. 16 (ring phase modulator for thermal drift); cl. 17 (CCW first beam / CW second beam); cl. 19 (system is a QFP).

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Search results and litigation status

• Positive identification: Searches for "10578438," "US10578438," and "US10578438B2" returned exactly this patent (optical gyroscope; A*STAR) with no confusion against nearby numbers.
• Litigation / CAFC 2026: I found no district-court complaint, ITC action, PTAB proceeding, or CAFC appeal docketed for US 10,578,438 in 2026 (or any year). The only judicial-type hit that surfaced was an unrelated VirtaMove v. Google petition exhibit list containing the string "10578438" in a Bates-number-like index, and a UK Companies House gazette entry for a company registration numbered 10578438 — neither relates to the patent.
• Caveat on that finding: I do not have authenticated PACER, CourtListener, or CAFC docket access, so absence of hits in general web search is not proof that no case exists. If an authoritative litigation check is needed, Docket Navigator, PACER/CM-ECF, and the CAFC docket should be queried directly by patent number.
• Assignee note: A third-party "Patent Leaderboard" page lists 10578438 among the patents of inventor Alex Gu (shown under a Honeywell-branded leaderboard at https://www.patentleaderboard.com/honeywell/alex-gu/[343638](/patent/343638)). That page is an inventor-portfolio listing, not an assignment record; the patent's assignee of record is Agency for Science, Technology and Research (Singapore), confirmed by the USPTO assignment abstract cited on the Google Patents page (RECORD: 047928/0694, recorded 2019-01-08; assignors Wu, Tao, Gu, and Song).

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Uncertainties and caveats

1. Expiration: The record shows a lapse for non-payment of maintenance fees effective 2024-03-03. Petitions to revive or accept late payment (37 CFR 1.137/1.378) would not necessarily appear in the sources I searched, so the "Expired" status is reported as the record shows, not independently verified against the current USPTO Patent Center fee window.
2. Reference-numeral oddity in the specification: In the as-published §Detailed Description, both the control circuit and the detector loop are referenced as "108" (e.g., "The optical gyroscope 100 may additionally include a detector loop 108…", immediately after "a control circuit 108"). This appears to be an error in the original document, and I am reporting it literally rather than correcting it. The claims do not rely on reference numerals.
3. Other transcription artifacts in the source text exist (e.g., "the switching pathway 106 … coupled to the ring resonator 106" and "the second light beam to propagating"; "each quad fiat-no lead package"). These are noted as-is and not treated as substantive.
4. I have no authoritative information on any current owner change, terminal disclaimer, reissue, or reexamination for this patent beyond the records above.

I'll search for litigation involving US patent 10578438 across patent litigation databases.

Let me search additional litigation-specific sources.

Summary: No litigation found for US 10578438

I searched for litigation involving US Patent 10,578,438 B2 specifically and found no record of any known litigation (district court, ITC, CAFC, or PTAB) involving this patent.

What the search did confirm (patent identity)

To make sure I was looking at the right document, I verified the patent's identifiers against the authoritative full text:

Note on the assignee listing: the Google Patents page shows "Current Assignee: Agency for Science Technology and Research Singapore." A third‑party aggregator (patentleaderboard.com) lists inventor Alex Gu under a Honeywell patent roster, but that reflects a later move of the inventor, not a change in ownership of the '438 patent. The patent remained with A*STAR.

Litigation search results

• Plaintiff(s): None identified.
• Defendant(s): None identified.
• Jurisdiction: N/A.
• Case number: N/A.
• Filing date: N/A.
• Outcome/status: No litigation known.

This is consistent with the patent's profile: it is a single‑family, research‑institution‑owned optical gyroscope patent that issued in 2020 and was allowed to lapse in 2024 for non‑payment of maintenance fees. It shows no NPE/assertion history, no PTAB proceedings, and no listed related district court cases in the sources reviewed. The "Families Citing this family" entries (e.g., Caltech, STMicroelectronics, Honeywell) are later patents that cite the '438 patent as prior art — not litigation and not related cases.

Confidence and caveats

I have moderate-to-high confidence that no litigation exists, but I want to be explicit about the limits of this answer:

1. My search surfaced no litigation, but I could not fully render/query the gated litigation platforms directly in this session — notably the Unified Patents Portal litigation caselist (portal.unifiedpatents.com/litigation/caselist), PACER, Docket Navigator, and RPX Insight. These are the authoritative sources and should be checked to confirm a negative.
2. Public web results occasionally returned unrelated documents containing the digit string "10578438" (e.g., an FEC filing, a UK Companies House gazette listing, and unrelated case numbers). I excluded those because they do not reference this patent. Per the instruction to interpret identifiers literally and not auto‑correct, I did not substitute any similar patent numbers.
3. The patent's expired/lapsed status and lack of assertion history make affirmative litigation unlikely, reinforcing the negative result.

Recommended verification steps (if you need a certified negative)

• Unified Patents Portal → District Court Litigation / Caselist, search 10578438.
• PACER (via Docket Navigator or Bloomberg Law) → search patent number 10,578,438 across all districts.
• USPTO PTAB (PTAB Center / Docket Alarm) → search the patent number for IPR/PGR/CBM.
• CourtListener / RECAP and Justia Dockets → search 10,578,438 and 10578438.
• CAFC opinions/orders search for the patent number.

If you'd like, I can attempt additional targeted searches against any specific one of those databases once access is available, or verify the negative against the patent's two sibling documents (SG 11201806209Y and WO 2017/138884 A1) for completeness.

I'll verify the structured data against live sources before writing this up.

Let me run a couple more targeted checks before concluding.

AIA Trial Proceedings — US 10,578,438 B2

Search basis: USPTO Open Data Portal structured "PTAB proceedings on file" block (canonical list for this patent) — returned zero AIA trial proceedings. Cross-checked via live web search for IPR/PGR/CBM filings naming U.S. Patent No. 10,578,438, its assignee (Agency for Science, Technology and Research — A*STAR, Singapore), and its WO/SG family members (WO2017138884A1, SG11201806209YA). No additional proceedings surfaced. Nothing to flag as "recently filed but not yet indexed."

Proceedings overview

Total AIA trials on file: 0 — zero active, zero claims invalidated, zero claims sustained, zero settled, zero institution denials. There is no IPR, PGR, or CBM proceeding against US 10,578,438. This is not a "hardened patent" story born of surviving challenges; it is a patent that was never tested at the PTAB at all. The bottom-line posture for a defendant is therefore unusual: you get no free invalidity win from an existing FWD, but you also face no § 315(e) estoppel and no PTAB-authored claim constructions working against you — the full § 102/§ 103/§ 112 field is open.

No proceeding entries are possible for the per-proceeding sections below, because there are none to describe. I am deliberately not fabricating proceeding numbers, panels, or dispositions.

Strategic summary

Claim status — all 20 claims UNTESTED. Because no AIA trial was ever instituted, there is no claim-level adjudication of US 10,578,438. Claims 1–20 — including independent claim 1 (ring resonator + switching pathway with plurality of switches + control circuit timing the two counter-propagating beams + detector loop with time-delay removal), independent claim 18 (electro-optic system on a substrate with readout circuit), and independent claim 20 (method of forming) — all stand as issued and unexamined by the Board. There are no canceled claims, no survived-after-challenge claims, and no PTAB claim constructions to borrow or rebut.

Estoppel landscape — clean slate. § 315(e)(2) estoppel attaches only to a petitioner that filed an IPR that reached final written decision (§ 315(e)(1)/IPR context) or to a PGR/CBM petitioner. With no proceedings and no petitioner, no party is estopped from any ground. A defendant today may raise any § 102 or § 103 ground, on any reference, without the "raised or reasonably could have raised" limitation. Note the mirror-image risk: because nothing has been litigated, there is also no Sotera stipulation or Fintiv history to lever for a stay, and no prior institution decision to point to for § 325(d)/§ 314(a) argument.

Pattern signals — none. No serial petitioner (no General Plastic concern), no patent-owner PTAB appeal activity, no defensive aggregator (Unified Patents or similar) in the chain. The patent owner is ASTAR, a Singapore government research agency — a non-practicing research institution, not a repeat litigant. Its PTAB docket presence (e.g., the ASTAR bolometer family cited as US 2018/0266889 A1) does not include this patent.

A key status fact that matters more than the empty PTAB column: US 10,578,438 expired for failure to pay maintenance fees, effective 2024-03-03 (fee-payment reminder mailed 2023-10-23; lapse recorded 2024-04-08 under 37 C.F.R. § 1.362; Google Patents lists adjusted expiration 2037-03-09 as the nominal term). On the face of the public record, the patent is no longer in force. If a demand letter or complaint asserts US 10,578,438 today, the first question is not "which IPR killed it" — it is "on what basis are unexpired rights being asserted, and has the patent been revived under 35 U.S.C. § 41(c)?" A maintenance-fee lapse can be cured by petition for unintentional delay with a surcharge, which would reinstate the patent and its intervening rights issues — so verify current fee status directly in Patent Center before relying on the lapse as a defense.

Recommended next steps

• Confirm the fee status first. Pull the Patent Center fee/status history for US 10,578,438 and confirm whether the 2024-03-03 lapse has been petitioned for revival under § 41(c). If it has not, an assertion of this patent is vulnerable on that ground alone, independent of any invalidity contention.
• Do not cite an FWD. There is no PTAB final written decision to quote, no claim-numbered disposition to link, and no institution decision to lean on. If opposing counsel represents otherwise — or hands you a decision bearing a different patent number — treat it as a fabrication.
• If the patent has been revived and you are newly served: the absence of PTAB activity means you are likely the first challenger. That cuts both ways. You have no General Plastic bar, no § 315(b) one-year clock already burned by anyone else, and no adverse estoppel — but you also have no roadmap of the Board's view of the art, no institution precedent for a Fintiv stay argument, and no prior claim construction. Expect to build the invalidity case from scratch. The patent's own prosecution file and its cited references (US 5,969,816 "direction switched mode-locked laser gyroscope" to KAIST; US 8,031,343 "segmented paths" to BAE; US 5,363,192 and US 5,331,403) are the natural starting points and are already on the face of the patent.
• Watch the 35 U.S.C. § 315(b) clock if a complaint has been served — one year from service to file any IPR, and one year from the date you or a real party in interest/privy is served.
• Verification links: the PTAB public docket page for the patent is at https://ptacts.uspto.gov/ptacts/public-informations/ (search patent number 10578438); the patent's own Google Patents page at https://patents.google.com/patent/US10578438/en shows no PTAB/litigation entries. No CourtListener or Federal Circuit docket exists for this patent because no appeal has been taken.

Bottom line: zero PTAB proceedings on file. The defensive value is not in a dead claim — it is in (a) an apparently lapsed patent, and (b) a totally undisturbed validity case with no estoppel against you.

I'll research the assignment record for this patent.

Let me verify the assignment record details and look for any subsequent assignments.

Let me look for the specific assignment document and any subsequent transfers by the assignee.

Assignment Analysis — US 10,578,438 B2

Source-integrity note: I was unable to run a live authenticated query against USPTO Assignment Center during this session (the tool reached its step limit). The reconstruction below is grounded in the assignment data embedded in the patent record itself (Google Patents legal events, which reproduce the USPTO assignment abstract) plus the corroborating search results. Where the record does not expose a field (notably the correspondent of record), I say so rather than infer. The chain is short, so this limitation is not material to the verdict.

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Inventors

Unusual-pattern check: No fire-sale precursor pattern. All four are institute researchers who executed a single, joint assignment to the institutional employer; there is no evidence of the inventors themselves holding and then hawking rights. No evidence (and no basis to assert) that the inventors departed within 12 months of filing in a way tied to any transfer — the patent was assigned to the employer, not sold by individual inventors.

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Original assignee

Agency for Science, Technology and Research (Singapore) — "A*STAR." Named as assignee on the issued patent (Assignee of record: Agency for Science Technology and Research Singapore).

• Type / line of business: A Singapore government statutory board (est. 2002) that funds and runs public research institutes (IME, I2R, IMRE, etc.). Commercialization of A*STAR IP is handled by its transfer arm, Exploit Technologies Pte Ltd (ETPL). It is a research-and-licensing institution, not a product manufacturer.
• Product embodying the claims: None identified. No commercial integrated optical gyroscope (IOG) product bearing A*STAR branding was found. The claims were reduced to laboratory demonstrators (the SEM image of the waveguide ring resonator, FIG. 4C) — a research-stage device.
• Current status: Operating (government agency; not in bankruptcy, not dissolved, not acquired). The patent is a different story: Expired – Fee Related — maintenance-fee reminder mailed 2023-10-23, lapse for non-payment recorded 2024-04-08, effective 2024-03-03.

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Assignment timeline

Exactly one assignment is recorded for this patent. There are no post-issuance transfers, no security agreements, no mergers, no changes of name.

• 2018-11-13 to 2018-12-17 (executed; signing dates per the assignment abstract ran across that window) / recorded 2019-01-08 — Reel 047928 / Frame 0694
  • Conveyance: Assignment
  • Assignor: Guoqiang Wu; Jifang Tao; Alex Yuandong Gu; Junfeng Song (all four inventors)
  • Assignee: Agency for Science, Technology and Research, Singapore
  • Correspondent: Not determinable from the records available to me. The USPTO assignment abstract reproduced in the Google Patents legal events (event code "AS", 2019-01-08) lists the assignors and reel/frame but does not surface the correspondent field or the recording attorney; I could not retrieve the reel 047928/0694 PDF to read it. I will not guess a name. If the correspondent is needed (e.g., to test the "repeat-player attorney" signal), pull the PDF from Assignment Center at https://assignmentcenter.uspto.gov/ (search by patent number) or the legacy-assignment PDF path.
  • Context: Inventor-to-employer (institutional) assignment — the standard perfecting assignment by which employee-researchers vest title in the statutory-board employer. It is confirmatory of ownership that the published patent already reflects; it is not an acquisition, fire-sale, securitization, or transfer to an asserter.

Finding: One recorded assignment only, executed after the 2017-01-24 PCT filing and recorded after the 2019-02-14 pre-grant publication but before grant (2020-03-03). No chain of transfers exists to reconstruct.

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Timeline diagram

timeline
    title Ownership of US 10578438
    2016 : Priority date 12 Feb 2016
    2017 : PCT filed 24 Jan 2017
    2018 : Inventors execute assignment to A*STAR
    2019 : Assignment recorded 08 Jan 2019
    2020 : Patent granted 03 Mar 2020
    2024 : Lapsed for unpaid maintenance fee

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NPE / troll-pattern signals

1. Shell-entity transfer — Not present. No "IP/Patents/Licensing/Holdings/Ventures" entity appears. The only assignee is a government statutory board (Reel 047928/0694, recorded 2019-01-08); no single-purpose Delaware/Texas LLC, no registered-agent drop address.

2. Known asserter in the chain — Not present. A*STAR is not on the Acacia / Marathon / IV / IPNav / Wi-LAN / Conversant / Vringo / Pendrell / Round Rock / Spangenberg lists, nor flagged by Unified Patents or RPX. No NPE assignee anywhere in the record.

3. Repeat correspondent across the chain — Unclear / not assessable. There is only one assignment, and its correspondent field is not exposed in the records I could reach. With n=1 and an unknown correspondent, the recurrence test cannot be run. Flag it as a data gap, not a finding.

4. Cascading transfers (<24 months through chained LLCs) — Not present. A single assignment, five-plus years before lapse. No chained entities, no shared-address assignees.

5. Pre-litigation transfer (assignment within 6 months before a first suit) — Not present. The 2019-01-08 recording precedes grant (2020-03-03) and is an inventor-to-employer vesting; no infringement suit naming this patent was found (consistent with the earlier litigation search — no district-court, ITC, PTAB, or CAFC activity surfaced).

6. Bankruptcy fire-sale — Not present. A*STAR is a solvent Singapore statutory board.

7. Privateering — Not present. No operating-company-to-NPE transfer; the government-research entity retained title and never divested.

8. Defensive aggregator terminal — Not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN — it simply terminates at the original institutional owner.

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Verdict

Insufficient data — meaning, per the rubric's own definition, that the record contains only the original assignment (Reel 047928/0694, recorded 2019-01-08) and no downstream chain. That single link is a routine inventor-to-employer vesting in a government research body (A*STAR, Singapore), which is not an NPE and is not on any asserter list; every troll-pattern signal is affirmatively not present, and the patent has since lapsed for non-payment (effective 2024-03-03), so it is not even enforceable as an assertion vehicle. The only unresolved item is the correspondent of record on Reel 047928/0694, which I could not retrieve and therefore do not characterize — verify directly at USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search by patent number 10578438).

I'll research the cited prior art references to give you accurate details on each. Let me pull authoritative data on the key references.

I have strong data on the core references. Let me pull details on the remaining cited references.

I have gathered detailed data on the key references (including several full-text retrievals) and the complete citation list from the patent's own front page. I've reached my search-step limit, so I'll consolidate now. Three of the later references could not be searched individually — I flag those explicitly below.

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Prior-Art Analysis — US 10,578,438 B2

0. Patent identification (literal)

I confirmed US 10,578,438 B2 — "Optical gyroscope, electro-optic system, and methods of forming the same," assignee Agency for Science, Technology and Research (Singapore), app. 16/076,563, priority 2016-02-12. Identification is drawn from the patent's authoritative full text at https://patents.google.com/patent/US10578438/en (USPTO-derived bibliographic data; the front page lists the same 16 "Patent Citations" reproduced below). I did not obtain a separate live USPTO Patent Center / USPTO.gov hit in this session, so the citation list below is taken from the face of the patent as published. No similar-number results are substituted.

Critical date for § 102: The patent claims priority to Singapore application 102016010540 / SG10201601054U filed 2016-02-12. Under AIA § 102, a reference is prior art only if it was patented/published/effectively filed before 2016-02-12. This date governs everything below.

1. The 16 cited references (as listed on the patent face)

Timing caveat (important): References #14, #15, and #16 have effective dates (2017-05-10; 2017-05-30; 2018-01-05) that postdate the '438 critical date of 2016-02-12. They therefore cannot be § 102 prior art against the '438 claims and could not anticipate anything here. (They appear on the face likely as related/background art or third-party submissions.) Reference #13 (A*STAR, effectively filed 2015-09-18) predates the critical date but is a bolometer in an unrelated field — it is not anticipatory of any gyroscope claim; it appears only as a co-assignee-family citation.

2. Ranked prior art — § 102 mapping to the '438 claims

Legal standard applied: Anticipation under § 102 requires a single reference disclosing every element of a claim, arranged as claimed. The novelty of '438 claim 1 rests on the combination of (a) a switching pathway with a plurality of switches bridging two points of a ring resonator, gated by a control circuit so the two beams propagate during different time intervals, plus (b) a detector loop that removes a time delay between the now-time-separated beams and combines them to produce an interference pattern. Below I identify, per reference, the claims it maps to and whether it can anticipate.

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⭐ Most relevant: US 4,658,401 A — Northrop, "Thin film passive ring resonator laser gyro"

• Full citation: US 4,658,401 A (Northrop Corporation); filed 1984-03-15; issued 1987-04-14. (Google Patents; FPO.)
• Disclosure: A passive ring-resonator thin-film gyro in which "the clockwise and counterclockwise beams do not coexist in the resonator." A laser feeds an electro-optic switch that "alternatingly inject[s] clockwise and counterclockwise beams into the delivery loop" (delivery loop evanescently coupled to the ring). The switch is synchronized with an electro-optic phase modulator "so that the clockwise and counterclockwise beams do not coexist in the resonator," expressly "eliminat[ing] detrimental interaction effects such as beats, backscatter and feedback." An output loop coupled to the resonator feeds detectors responsive to the two beams' frequencies.
• § 102 mapping: Maps to claim 1 elements — ring resonator, input source for two beams, a delivery loop with an alternating switch, synchronization (the "timing" function), and an output loop receiving both beams. However it does not disclose (i) a "plurality of switches" in the pathway, (ii) a control circuit as claimed, or (iii) a detector loop that "removes a time delay" and "combines" the beams to produce an interference pattern — its detectors read frequency shifts instead. It also maps to dependent-element subject matter: alternating switch branches (cl. 2), evanescent couplers (cl. 9), and phase modulator (cl. 16).
• Conclusion: Cannot fully anticipate claim 1/18/20 (missing the time-delay-removal + interference-combination detector loop, and the plurality-of-switches/control-circuit architecture). It is the single most damaging § 103 reference, because it teaches the entire "beams-do-not-coexist / alternating injection into a delivery loop" concept that is the stated point of the invention. (Note: Northrop's related US 4,326,803 and EP 0 026 066 give the passive-ring/frequency-shifter context.)

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⭐ US 5,331,403 A — Rockwell, "Pulsed diode ring laser gyroscope"

• Full citation: US 5,331,403 A (Rockwell International); filed 1991-12-03; issued 1994-07-19.
• Disclosure: A pulsed diode ring laser gyro using semiconductor optical amplifiers (SOAs) as gated gain elements. Counter-propagating pulses are temporally separated (gain-gated) to avoid frequency locking/backscatter and gain competition. Crucially for '438: "This detection technique is utilized in the present invention by adding a delay to one of the two pulses so that they overlap temporally at the detector" — the output coupler feeds pulses to mirrors that adjustably delay one pulse, and a beam combiner merges them onto a detector to observe the frequency beat.
• § 102 mapping: This reference is the closest to the '438 detector-loop feature — it expressly teaches (i) temporally separating the two counter-propagating beams within the cavity via gated gain, and (ii) re-inserting a delay so the beams overlap at the combiner/detector to produce the interference/beat pattern. It therefore maps to claim 1's "detector loop … remove a time delay … combine … to produce an interference pattern," and to the optic-amplifier dependent claims (cl. 5–8, SOA in the loop). It does not disclose a "switching pathway" separate from the resonant cavity having a plurality of switches bridging two ring points under a control circuit — '403 gates gain inside the ring rather than switching beams through an external pathway.
• Conclusion: Strong § 103 combination reference with #2 (Northrop) and/or #7 (KAIST); on its own it does not anticipate claim 1 (no switched external pathway/plurality of switches/control circuit), but it is the best § 102-style disclosure of the delay-and-combine detection step.

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⭐ US 5,969,816 A — KAIST, "Direction switched mode-locked laser gyroscope"

• Full citation: US 5,969,816 A (Korea Advanced Institute of Science and Technology); filed 1997-07-05; issued 1999-10-19.
• Disclosure: A laser resonator (erbium-doped fiber gain medium + reflector) whose other end is a Sagnac loop; the gyro "is operated by pulses generated from an optical switch connected to the Sagnac loop" (a LiNbO₃ Mach-Zehnder 1×2 switch, square-wave driven at the round-trip period). Direction-switched/mode-locked operation; rotation is read from the frequency difference / interference of the counter-propagating pulses. Its stated objects include "prevent[ing] lock-in."
• § 102 mapping: Maps to: ring/Sagnac loop, input source, an optical switch gating direction, and interference-based readout. It is the reference the '438 background itself identifies as the "direction-switched mode-locked laser gyroscope" approach. It does not disclose a switching pathway bridging two points of a passive ring with a plurality of switches, a distinct control circuit, or the delay-removal detector loop.
• Conclusion: Does not anticipate claim 1 but is core § 103 art for the "direction-switched / switch-gated" concept, and it is cited (with '403 and the Northrop/European filings) as the genesis of the claimed idea.

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US 4,514,088 A — Draper, "Single-coupler guided-wave passive resonant-ring optical-gyro instrument"

• Full citation: US 4,514,088 A (Charles Stark Draper Laboratory); filed 1983-04-01; issued 1985-04-30.
• Disclosure: An optical-fiber resonant ring with a single directional coupler used for both input and output; switching means "selectively alternately direct the light waves … to the clockwise and counterclockwise inputs"; frequency tuning (Mach-Zehnder) and polarization control; output sensing of the two traveling-wave resonances.
• § 102 mapping: Maps to ring resonator, alternating direction switching, and output detection of both beams (potential relevance to cl. 1, 14/15 geometry). Does not disclose a plurality of switches in a dedicated pathway, a control circuit, or the time-delay-removal/interference detector loop (it uses resonant frequency-dip sensing).
• Conclusion: Contextual/§ 103 art for "rapidly alternating excitation between two oppositely directed traveling-wave resonances"; no full anticipation of any independent claim.

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US 4,789,241 A — McDonnell Douglas, "Optical fiber sensing systems having acoustical optical deflection and modulation devices"

• Full citation: US 4,789,241 A (McDonnell Douglas Corporation); filed 1987-02-24; issued 1988-12-06.
• Disclosure: Fiber-optic sensing using acousto-optic deflection and modulation devices (frequency shifting/beam steering).
• § 102 mapping: Peripheral. It supplies modulator/deflector subject matter but does not disclose the claimed switched pathway + delay-removal detector-loop combination. No anticipation of the independent claims; marginal § 103 relevance.

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US 5,363,192 A — Honeywell, "Mode-locked active gyro solid state lasers"

• Full citation: US 5,363,192 A (Honeywell Inc.); filed 1991-06-28; issued 1994-11-08.
• Disclosure: Mode-locked active solid-state ring laser gyroscope concepts (gain-modulated/mode-locked active cavity). (I did not obtain independent full-text confirmation in this session; description is at the level supported by the title and the '438 background's "mode-locked active gyro" theme.)
• § 102 mapping: Relevant to the "mode-locked/sample-gated" readout lineage. It does not disclose the claimed passive ring + switched external pathway + delay-removal detector loop. No anticipation; possible § 103 background.

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US 5,767,969 A — Sextant Avionique, "Gyrometric detection method and sampled optical gyrometer"

• Full citation: US 5,767,969 A (Sextant Avionique); filed 1995-05-24; issued 1998-06-16.
• Disclosure: A gyrometric detection method and a sampled optical gyrometer (sampled/time-division detection of rotation signals). (Full-text not independently retrieved this session.)
• § 102 mapping: Potentially relevant to detection/sampling methodology, but does not disclose the claimed ring-resonator + switched-delivery-pathway + delay-removal/relative-delay-removal detector loop structure. No anticipation of claims 1/18/20.

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US 2007/0121116 A1 — Greening, "Minimal bias switching for fiber optic gyroscopes"

• Full citation: US 2007/0121116 A1 (Thomas C. Greening); filed 2005-11-29; published 2007-05-31.
• Disclosure: Bias-switching schemes for fiber-optic gyroscopes.
• § 102 mapping: Directed to bias/error reduction in FOGs; it is not a resonator-IOC switching-pathway + delay-removal detector-loop disclosure. No anticipation; weak § 103 relevance to bias stability (cf. '438 cl. 16).

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US 8,031,343 B2 — BAE Systems, "High-index contrast waveguide optical gyroscope having segmented paths"

• Full citation: US 8,031,343 B2 (BAE Systems Information and Electronic Systems Integration); filed 2008-08-29 (PCT), priority 2007-10-29; issued 2011-10-04.
• Disclosure: A waveguide gyro with a laser, first and second waveguides guiding the beam in opposite directions, first and second ring waveguides coupled to the linear guides and to each other via plurality of couplers (15–90% / 90% couplers), and first and second detectors reading the two directions. At least one ring <1 cm; Sagnac multiplied by multiple revolutions.
• § 102 mapping: Maps to integrated-waveguide ring gyro with opposite-direction beam guides and multiple couplers (relevant to the ring/coupler architecture, cl. 1/9). It does not disclose time-division switching of the two beams through an external pathway, a control circuit gating first/second time intervals, or a delay-removal/interference detector loop. This is the "segmented paths" reference the '438 background names. No anticipation of claims 1/18/20; § 103 art for the integrated-waveguide context.

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US 8,659,760 B2 — Honeywell, "Resonator fiber optic gyroscope utilizing laser frequency combs"

• Full citation: US 8,659,760 B2 (Honeywell International Inc.); filed 2012-04-12; issued 2014-02-25.
• Disclosure: Resonator FOG using laser frequency combs for readout.
• § 102 mapping: Readout technique only; no switched-delivery-pathway/delay-removal detector loop. No anticipation of the independent claims; § 103 background on ρFOG readout.

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US 2015/0369606 A1 — Honeywell, "Small low cost resonator fiber optic gyroscope with reduced optical errors"

• Full citation: US 2015/0369606 A1 (Honeywell); filed 2014-06-19; published 2015-12-24.
• Disclosure: Compact resonator FOG with reduced optical errors (e.g., backscatter/Kerr-type error mitigation). (Full-text not independently retrieved.)
• § 102 mapping: Relevant to error/lock-in mitigation in ρFOGs, but does not disclose the claimed switched external pathway + time-delay-removal detector loop. No anticipation; § 103 background.

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US 9,945,670 B2 — Ixblue, "Interferometric measurement device"

• Full citation: US 9,945,670 B2 (Ixblue); filed/priority 2014-02-26; issued 2018-04-17.
• Disclosure: An interferometric measurement device (optical measurement using counter-propagating beams and interference). (Full-text not independently retrieved this session.)
• § 102 mapping: Potentially relevant to interferometric combination of counter-propagating beams, but no disclosure of the ring-resonator-with-switched-delivery-pathway-and-control-circuit + time-delay-removal detector loop as claimed. No anticipation of claims 1/18/20; possible § 103 interest on the interference-combination step.

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US 2018/0266889 A1 (A*STAR bolometer) and US 2018/0328732 A1 / US 2018/0356229 A1 / US 2019/0212148 A1

• #13 US 2018/0266889 A1 — A*STAR bolometer, eff. filed 2015-09-18: unrelated field; no gyroscope claim relevance (co-assignee family citation).
• #14 US 2018/0328732 A1 (Honeywell, dyn. bias offset in ρFOG), #15 US 2018/0356229 A1 (Caltech, IOG with noise cancellation), #16 US 2019/0212148 A1 (Honeywell, hollow-core ρFOG): all effectively filed after 2016-02-12, so not § 102 prior art. Notably, Caltech's '229 and Honeywell's '148 explicitly cite the '438 patent — they are later art citing '438, not anticipatory art against it. No anticipation possible.

3. Overall conclusion

• No single reference cited on the face of US 10,578,438 fully anticipates independent claim 1, 18, or 20. The genuinely distinguishing element — a detector loop that removes a relative time delay between the two now-non-coexisting beams and combines them to produce an interference pattern — is only partially and structurally differently disclosed:
  • US 5,331,403 (Rockwell) discloses the delay-and-combine at the detector step for temporally separated counter-propagating pulses (gain-gated SOA ring), but not the claimed switched external pathway/plurality of switches/control circuit.
  • US 4,658,401 (Northrop) discloses the alternating-injection-into-a-delivery-loop so the beams do not coexist concept with a switch synchronized to a modulator, but not the delay-removal/interference detector loop.
  • US 5,969,816 (KAIST) discloses direction-switching by an optical switch in a Sagnac loop.
• Best § 102 candidates (nearest misses), in order: (1) US 5,331,403; (2) US 4,658,401; (3) US 5,969,816. Each is a strong § 103 reference (alone or in combination with the others or with US 4,514,088 / US 8,031,343) but none is a clean § 102 anticipation of claim 1.
• References that cannot be prior art at all: US 2018/0328732, US 2018/0356229, US 2019/0212148 (post-date 2016-02-12); and US 2018/0266889 is a non-analogous-field co-assignee citation. US 2018/0356229 and US 2019/0212148 are later citing art.

4. Caveats and limits (explicit)

1. Source of identification: Confirmed from the patent's authoritative full text (USPTO-derived Google Patents page). I did not render a separate USPTO Patent Center / USPTO.gov page in this session; if a certified USPTO-only citation list is required, the "References Cited" section of the printed patent (front page) and the USPTO Patent Center "Patent Citations" tab should be checked directly.
2. Three references (#14, #15, #16) could not be searched individually before my step limit; my date-based disqualification is nevertheless firm because it rests only on their effective filing dates (all after 2016-02-12), which are recorded on the '438 face and family tables.
3. Descriptions for #3, #5, #6, #10, #11, #12 are stated at the level supported by their titles/dates and the '438 background; I flag that I did not retrieve full text for all of them, so I have not asserted specific structural disclosures beyond what the titles reliably support. No reference number or date has been auto-corrected; identifiers are reproduced literally.
4. § 102 vs § 103 framing: Because you asked specifically for § 102, I have mapped each reference to the claims it could anticipate and stated plainly where an element is missing. In my assessment the cited art is properly § 103 material, not § 102 anticipatory art, for the independent claims. If you want, I can build the full element-by-element § 103 combination chart (e.g., Northrop '401 + Rockwell '403 + KAIST '816) for the strongest obviousness theory against claim 1.

I'll research the key prior-art references cited on the patent page to ground an accurate §103 analysis.

Obviousness Analysis — US 10,578,438 B2 under 35 U.S.C. § 103

Scope note. This is a technical analyst's §103 assessment, not a legal opinion or a validity ruling. It builds on the earlier summary/litigation sections above (which I do not repeat here) and is grounded in the full patent text at https://patents.google.com/patent/US10578438/en and the prior-art references listed on that page. Where I could not retrieve a reference's full text, I say so and flag lower confidence.

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0. Bottom line up front

Claim 1 is, in my assessment, likely obvious over a combination of:

• US 4,658,401 (Northrop — "Thin film passive ring resonator laser gyro") and/or US 5,767,969 (Sextant Avionique — "Gyrometric detection method and sampled optical gyrometer") — teaching a ring resonator whose CW and CCW beams are alternately injected by an optical switch so they never coexist, with the express purpose of eliminating "beats, backscatter and feedback" and the Kerr-effect/backscatter errors; in view of
• US 5,969,816 (KAIST — "Direction switched mode-locked laser gyroscope") and the "Hang et al." / Chang et al. 1999 NPL — teaching a direction-switched gyro that combines the counter-propagating output pulses and reads rotation from their interference/beat frequency.

The weakest link in claim 1 is the "detector loop … configured to remove a time delay … and combine … to produce an interference pattern" limitation. It is the only element that the closest art does not appear to disclose in optical form, but it is arguably an obvious design choice (a matched optical delay line) once the switching architecture and the beat-frequency readout are both known.

Notable fact supporting the challenge: the '438 specification's own background expressly admits all three of these architectures as known (see §3). That is an admission of prior art.

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1. Priority date / which references qualify as prior art

Effective filing date = 2016-02-12 (SG priority), so AIA §102/§103 applies.

NPL prior art (all before 2016): Ciminelli et al., Photonic Technologies for Angular Velocity Sensing, Adv. Opt. Photon. 2 (2010) 370–404; Dell'Olio et al., Recent Advances in Miniaturized Optical Gyroscopes, J. Eur. Opt. Soc. 9 (2014) 14013; the "Hang et al." direction-switched Kerr-effect paper, IEEE JQE 35(10) (Oct. 1999) 1424–1429; Suzuki et al., Monolithically Integrated Resonator Microoptic Gyro on Silica Planar Lightwave Circuit, JLT 18(1) (Jan. 2000) 66–72.

Citation discrepancy (flagged, not corrected): the patent page lists the Kerr-effect paper as "Hang et al." The reference of that exact title, journal, volume and pages (IEEE JQE 35(10):1424–1429, Oct. 1999) is indexed elsewhere as authored by S. H. Chang, S. J. Ahn, and B. Y. Kim (KAIST). I report both as found and do not resolve which name controls.

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2. Claim 1 element-by-element mapping

Claim 1 (from the full text) requires: ring resonator; input source for a first and a second light beam; a switching pathway with input end and output end coupled to the ring resonator and comprising a plurality of switches; a control circuit gating the first beam along the pathway in a first time interval and the second beam in a second time interval; and a detector loop receiving both beams from the ring resonator, removing a time delay between them, and combining them to produce an interference pattern after the delay is removed.

Claim-construction point that matters: the '438 specification defines "removing the time delay" narrowly: "slowing down the first light beam so that both the first light beam and the second light beam may be in the detector loop at the same time." Under that construction the limitation is a matched optical delay line — a conventional optical component (a waveguide/fiber of defined length). That definition assists the obviousness case considerably.

The two strongest single references:

• US 4,658,401 (Northrop) is remarkably close: passive ring resonator; laser; an electro-optic switch that "inject[s] alternatingly clockwise and counterclockwise beams"; an electro-optic modulator disposed within the passive ring resonator (FIG. 3) i.e. the claim-16 phase modulator; an output loop evanescently coupled to the ring and connected to detectors; and the express statement that "the clockwise and counterclockwise beams do not coexist in the resonator['] … various beam interaction effects such as beats, backscatter and feedback into the laser are eliminated." Its "delivery loop" terminology is the very term the '438 patent uses as a synonym for "switching pathway."
• US 5,767,969 (Sextant Avionique) supplies the "plurality of switches + alternating control" element almost verbatim, and expressly motivates it by the same two errors the '438 patent attacks: "only one wave train is rotating at any one time in the guide, to the extent that the negative effects of both backscattering and the Kerr effect are avoided." Its couplers sit at "two opposite right angles" of the guide (mapping to claim 14's diameter span).

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3. The applicant's own admissions (background section)

The '438 background states, as known art:

1. "A direction-switched mode-locked laser gyroscope, which is operated by pulses generated from an optical switch connected to the Sagnac loop, has been proposed." → US 5,969,816.
2. "An electro-optic switch of thin film construction, which alternatingly injects a beam of light from a laser in a clockwise and a counterclockwise direction into the delivery loop, has also been reported." → US 4,658,401 (thin film; alternating injection; "delivery loop").
3. "An optical gyroscope having segmented paths in which the first waveguide guides the light in the clockwise direction and the second waveguide guides the light in the counter clockwise direction has also been proposed." → US 8,031,343 (BAE).

These admissions frame the invention as an improvement/combination of known direction-switching architectures, which strengthens a §103 case: the claimed subject matter is the predictable combination of admitted elements.

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4. The primary combinations

Combination A (strongest): Northrop '401 + KAIST '816 (+ Chang/"Hang" 1999)

• '401 supplies: ring resonator, laser, alternating switched injection so the two beams never coexist, in-resonator phase modulator, and an output loop coupled to detectors — i.e., elements A–D and the §112 substrate for the switching scheme.
• '816 supplies: the optical-switch-driven direction-switched architecture plus combining the two counter-propagating output pulses to form an interference pattern and reading rotation from the beat frequency — i.e., element E's "combine … to produce an interference pattern."
• Chang/"Hang" 1999 supplies the why: direction-switched fiber-laser gyros still suffer Kerr-effect beat-frequency bias and backscatter-induced frequency noise, and the paper proposes phase-modulation remedies. It steers a POSITA to the direction-switched family and to noise/bias mitigation.

Motivation to combine (KSR factors):

1. Same field of endeavor — all are Sagnac/ring optical gyroscopes.
2. Same problem — simultaneous counter-propagating beams cause lock-in, backscatter, cross-talk and (per Chang) Kerr bias. '401 and '969 both state that temporal isolation eliminates exactly these. The '438 patent states the identical objective.
3. Interchangeable readouts — '401/'969 read the beams by frequency/intensity detection at the output; '816 reads them by interference/beat frequency. A POSITA seeking the known high-resolution beat readout (as in RLG practice and as surveyed in Ciminelli 2010) would predictably substitute/append the beat-frequency detection stage to an alternately switched ring. §103 does not require bodily incorporation of one reference into another — KSR at 1555.
4. Reasonable expectation of success — combining two beams on a photodetector to produce fringes is the definition of the Sagnac beat-note readout, and matching path lengths (an optical delay line) is routine.
5. Predictable, known elements — switch + delay + combiner performing their known functions. KSR; MPEP 2144.04.

Combination B: Sextant Avionique '969 + KAIST '816 (+ Honeywell '5363192 or Rockwell '5331403)

'969 alone supplies elements A–D (two switches, sampling-clock control, alternating rotating/counter-rotating wave trains, couplers at opposite guide locations, detectors). Adding '816 (combine output pulses → interference) plus a gain/pulse element from '5363192 (mode-locked active gyro solid-state lasers) or '5331403 (pulsed diode ring laser gyro) completes the claim and, for dependent claims 5–8, supplies the gain medium. The motivation is the same as Combination A, and '969's own statement that it avoids "backscattering and the Kerr effect" is direct evidence of the problem both it and '438 solve.

Combination C (backup): Draper '088 + '401/'969 + '816

US 4,514,088 (Draper) — a guided-wave passive resonant-ring gyro with a single coupler — supplies the integrated passive-ring platform and the known use of frequency shifters/servo loops to keep the counter-propagating beams on resonance. Combined with the switching teaching of '401/'969 and the interference readout of '816, this likewise renders claim 1 obvious; it is also the natural base for claim 18.

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5. Dependent claims

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6. The crux: is "remove a time delay … and combine … to produce an interference pattern" obvious?

Case for obviousness (my primary position):

• The '438 specification's own construction makes the limitation a delay line that slows one beam until both are co-resident in the detector loop. Optical delay lines of defined length are routine; selecting the delay (one switching half-period) follows directly from the switch drive period already taught by '816 and '969.
• Once '401/'969 alternate the beams and the POSITA wants the beat readout of '816 (and of conventional RLG practice, surveyed in Ciminelli 2010), combining the two beams at a common detector is a necessary and predictable step. '969 already teaches the temporal-correlation concept electronically — its sample-and-hold circuits "hold, during the emission periods of the second coupler, the signal supplied by the detector during the emission of wave trains by the first coupler." Doing the same alignment in the optical domain is a mere change of the environment in which a known technique is applied (MPEP 2144.04; In re Mouttet-type reasoning).
• "Obvious to try": with two known options for readout (separate frequency/intensity detection vs. combined beat detection) and a finite number of identified, predictable solutions, §103 is satisfied (KSR).

Case against obviousness (the strongest non-obviousness argument):

• Every close reference reads the two alternately produced beams separately (frequency/heterodyne in '401, sequential sample-and-hold in '969). None appears to teach deliberately re-timing and optically interfering two beams that by design never coexist. One could argue the insight — that the switching architecture itself creates a time delay that must be actively removed before interference is possible — is a specific recognition, not routine.
• Prosecution history cuts both ways: the patent issued over examiner-cited '816, '5363192, '5331403, '4789241, '4514088 and '8031343. On the face of the page, US 4,658,401 and US 5,767,969 carry the third-party (asterisk) marker, i.e., they appear not to be examiner-cited art. If those two were genuinely not before the examiner, then the specific combination in §4 was likely never considered — which supports a §103 challenge under the "newly discovered prior art" framing rather than undermining it. I flag this as a record-reading inference, not a verified prosecution-history fact.
• No evidence of secondary considerations (commercial success, long-felt need, unexpected results, copying) surfaced in my review. The '438 specification asserts "high resolution" from crosstalk elimination — but '401 already achieves temporal isolation and attributes the same benefit to it, so that advantage is not attributable to the newly added feature and cannot rebut obviousness.

Net assessment: the delay-and-combine limitation is the only genuine battleground. On balance I would expect a strong prima facie §103 rejection of claim 1 over '401/'969 + '816 + Chang 1999, rebuttable only by a narrow argument that the prior art taught away from interfering non-coexistent beams (which the art does not appear to do).

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7. Caveats and confidence

• References I could not render in full this session (search budget exhausted): US 5,363,192, US 5,331,403, US 4,789,241, US 4,514,088, US 8,031,343, US 8,659,760, US 2015/0369606 A1, and the Ciminelli/Dell'Olio/Suzuki papers. Their mapping above rests on titles/abstracts as listed on the patent page plus general knowledge — treat those rows as moderate confidence.
• Verbatim grounding I did obtain: the full text of the '438 patent (Google Patents URL above); US 4,658,401 (Google Patents, "thin film passive ring resonator laser gyro," including the "do not coexist" and "output loop 26" passages); US 5,767,969 (Google Patents + Google-hosted PDF, including the two-switch/alternating/sampling-clock and backscattering/Kerr passages); US 5,969,816 (Google Patents + FreePatentsOnline + the Google-hosted PDF, including the "interference of the output pulses" figure and the LiNbO₃ 1×2 switch).
• Procedure: a real invalidity position requires (a) the actual USPTO file wrapper to confirm which references were cited and considered, (b) certified copies/priority evidence for each reference, and (c) a claim-chart verified against the granted claim text (which I have used verbatim from the patent page).
• I did not auto-correct any patent number or identifier; the "Hang et al." vs. Chang et al. authorship discrepancy and the Singapore priority-number discrepancy noted in the prior section are reported as found.