US 11133872

I'll search for this specific patent number to verify the details and check for any CAFC 2026 docket information.

Let me verify the CAFC dockets and IPR history further.

US 11,133,872 B2 — Patent Summary

Bibliographic Data (verified against USPTO-record sources)

Sources: USPTO-record PDF at patentimages.storage.googleapis.com (US011133872B2); Google Patents (US11133872); Unified Patents portal (US-11133872-B2).

Abstract (verbatim)

"In a system for converting digital data into a modulated optical signal, an electrically controllable device having M actuating electrodes provides an optical signal that is modulated in response to binary voltages applied to the actuating electrodes. A digital-to-digital converter provides a mapping of input data words to binary actuation vectors of M bits and supplies the binary actuation vectors as M bits of binary actuation voltages to the M actuating electrodes, where M is larger than the number of bits in each input data word. The digital-to-digital converter maps each digital input data word to a binary actuation vector by selecting a binary actuation vector from a subset of binary actuation vectors available to represent each of the input data words."

Plain-Language Overview of the Invention

The patent addresses a core problem in optical modulation: Mach-Zehnder modulators and similar devices have an inherent cosine-shaped (non-linear) response, so directly mapping digital bits to electrodes produces distorted analog output. The invention linearizes the output by (a) using more electrodes than input bits (M > N), (b) applying a digital-to-digital mapping that chooses electrode actuation patterns to best approximate the desired linear (or other) response — i.e., an electrode is driven as a function of more than one input bit — and optionally (c) optimizing electrode lengths/effective areas away from the simple power-of-two series. It also covers phase-modulating variants (QAM transmitters) and semiconductor light-source (laser/LED) implementations.

Independent Claims (as shown in the provided full text; claims 1, 11, 13, 15)

Claim 1 — Modulation system (apparatus). A system with: an input for N digital data bits; an optical signal source; a modulator that modulates the input optical signal to produce one or more modulated outputs for transmission over optical fiber(s); and a converter that maps the N bits to M digital output bits (M > N, N > 1) under a digital-to-digital mapping, and supplies M drive voltages to the modulator. The mapping for each unique N-bit input is chosen based on an actuation pattern that alters the linearity of the modulator's optical response.

• Plain language: A transmitter that converts N parallel digital bits into M drive voltages (M more than N), using a lookup-style mapping selected to straighten out the modulator's non-linear response, then sends the modulated light down fiber.

Claim 11 — Method of generating/transmitting modulated optical signals. A method comprising: receiving N input bits; converting them (via a digital-to-digital mapping, M > N, N > 1) into M drive voltages, with each mapping selected to alter linearity of the modulator's optical response; supplying the voltages to the modulator; feeding input optical signals in; modulating them; and coupling the modulated outputs to optical fibers for transmission.

• Plain language: The counterpart process to claim 1 — the steps of mapping N bits to M drive voltages (M > N) to linearize the modulator, modulating light, and launching it into fiber.

Claim 13 — Method of parallel digital-to-optical-stream conversion. A method where a digital input (one of 2^N possible N-bit inputs, N > 1) is mapped, via a digital-to-digital mapping, to a digital output of M bits associated with M drive voltages (the output set has 2^M members, M ≥ N). The mapping is defined for every input. For a first subset of successively decreasing inputs, the deltas (step sizes) between the numerical values of the corresponding outputs decrease; for a second subset, the deltas increase.

• Plain language: Defines the shape of the mapping mathematically — the difference between successive output values is not constant; it shrinks in some input regions and grows in others, which is how the cosine non-linearity is counteracted.

Claim 15 — Modulation system with a light-generating modulator. Like claim 1, but the modulator is a semiconductor light-generating device that directly generates the modulated optical outputs in response to the drive signal derived from the N input bits, with the same M > N, N > 1 digital-to-digital mapping criterion for linearity-altering actuation patterns.

• Plain language: A variant where the "modulator" is itself a laser or LED that both generates and modulates the light, still using the M-over-N mapped drive scheme to improve linearity.

Note: The provided text cuts off mid-claim 17; claims 18–30 were not available in the source text, so I cannot summarize any additional independent claims among them. I verified the total count (30 claims) but not the content of claims 18–30.

Litigation / Status Notes (important caveats)

• The patent is under active challenge. Unified Patents filings show IPR2022-00576 and IPR2022-00575 (both with Final Written Decisions), plus Delaware District Court case 1:21-cv-01365 and multiple CAFC appeals (24-1726, 24-1727, 26-1277, 26-1280). (Source: Google Patents litigation links; Unified Patents portal.)
• Per a PatSnap litigation summary citing PACER records, in Cisco Systems, Inc. v. Ramot (CAFC case 24-1726), the Federal Circuit is reported to have affirmed unpatentability of US11133872B2 via a Rule 36 judgment issued April 13, 2026, with the recorded basis of termination "Unpatentable." If accurate, the patent's claims have been held unpatentable (as found in the underlying IPR proceedings), which would bar enforcement in its current form.
• CAFC 2026 dockets 26-1277 (Ramot at Tel Aviv University Ltd. v. Cisco Systems, Inc. and Acacia Communications, Inc., filed Dec. 22, 2025 — patent infringement, nature-of-suit "Fed. Qst.") and 26-1280 (Cisco/Acacia v. Ramot) also relate to this dispute. (Source: Justia CAFC dockets.)

Uncertainties

1. Terminal status / current enforceability: I could not independently confirm from the USPTO record itself whether the claims have been formally cancelled post-IPR; the unpatentability affirmance is per secondary litigation-intelligence sources, not an official CAFC opinion text (Rule 36 judgments are unpublished).
2. Date discrepancies: The Unified Patents portal lists application date Aug. 5, 2019, and grant date Sep. 27, 2021, and priority date Jun. 12, 2007 — one day earlier than the patent PDF/Google Patents (Aug. 6, 2019; Sep. 28, 2021; Jun. 13, 2007). I treated the patent PDF and Google Patents as authoritative.
3. Claims 18–30 content was not available in the provided text and was not independently retrieved.

Based on my searches, US Patent 11133872 (the "'872 patent," "Linearized Optical Digital-to-Analog Modulator," owned by Ramot at Tel Aviv University Ltd.) has been involved in a substantial, consolidated dispute with Cisco Systems, Inc. and its subsidiary Acacia Communications, Inc. Here is what the record shows:

1. District Court — Declaratory Judgment Action

Cisco Systems, Inc. and Acacia Communications, Inc. v. Ramot at Tel Aviv University Ltd.

• Jurisdiction: U.S. District Court for the District of Delaware
• Case No.: 1:21-cv-01365 (originally assigned to Judge Leonard P. Stark; later presided over by Judge Gregory B. Williams)
• Filing date: September 28, 2021 (the same day the '872 patent issued)
• Plaintiffs: Cisco Systems, Inc.; Acacia Communications, Inc.
• Defendant / Counterclaim-plaintiff: Ramot at Tel Aviv University Ltd.
• Nature: Declaratory judgment action seeking noninfringement of the newly issued '872 patent; Ramot counterclaimed for infringement. The complaint also involves the related '998 patent (US11342998).
• Status (as of the most recent records): Ongoing. Judge Williams issued a claim-construction/indefiniteness opinion on November 12, 2024 (finding some claims indefinite), and a summary-judgment opinion regarding a pre-AIA § 102(b) on-sale bar in October 2025 (denying Ramot's no-invalidity summary judgment). The docket remains active.

2. PTAB — Inter Partes Reviews (IPR2022-00575 and IPR2022-00576)

Cisco Systems, Inc. et al. v. Ramot at Tel Aviv University Ltd.

• Case Nos.: IPR2022-00575 and IPR2022-00576
• Filing date: February 16, 2022 (both)
• Institution decision: October 5, 2022
• Panel: Administrative Judges Monica S. Ullagaddi (writing), Christopher L. Crumbley, and Jason M. Repko
• Scope: IPR2022-00575 challenged claims 1–12, 15–22, and 30; IPR2022-00576 challenged claims 13, 14, and 23–29 of the '872 patent (collectively, all 30 claims).
• Final Written Decisions: IPR2022-00575 — September 29, 2023; IPR2022-00576 — October 3, 2023
• Outcome: The PTAB found the challenged claims unpatentable in Final Written Decisions. Both decisions were appealed by Cisco (Ramot cross-appealed in related proceedings).

3. Federal Circuit — Appeals of the IPR Decisions

Cisco Systems, Inc. v. Ramot at Tel Aviv University Ltd.

• Case Nos.: 2024-1726 (appeal of IPR2022-00575), 2024-1727 (appeal of IPR2022-00576), and 2024-1728 (appeal of a related IPR, IPR2022-01283, involving the patent family)
• Panel: Per curiam — Chief Judge Moore, and Judges Mayer and Lourie
• Disposition: Judgment entered April 13, 2026 — AFFIRMED under Fed. Cir. R. 36 (non-precedential). The Federal Circuit affirmed the PTAB's unpatentability findings without a written opinion, confirming that US11133872B2 was found unpatentable.

4. Federal Circuit — New Appeals Filed December 2025

Two additional CAFC appeals were filed in late December 2025 (reflected in the Google Patents litigation list for the '872 patent):

• Ramot at Tel Aviv University Ltd. v. Cisco Systems, Inc. and Acacia Communications, Inc. — CAFC Case No. 26-1277, filed December 22, 2025 (nature of suit: patent infringement, Federal Circuit question). Status: pending.
• Cisco Systems, Inc. and Acacia Communications, Inc. v. Ramot at Tel Aviv University Ltd. — CAFC Case No. 26-1280, filed December 2025 (Cisco/Acacia as appellants). Status: pending.

Summary

The litigation involves Ramot at Tel Aviv University Ltd. (patent owner) against Cisco Systems, Inc. and Acacia Communications, Inc. (accused infringers/challengers) across the Delaware District Court (1:21-cv-01365), the PTAB (IPR2022-00575, IPR2022-00576), and the Federal Circuit (2024-1726/1727/1728, 26-1277, 26-1280). The most significant development is the April 13, 2026 Rule 36 affirmance, which left standing the PTAB's Final Written Decisions holding the asserted claims of US11133872 unpatentable. The Delaware DJ action was still active as of late 2025 (claim construction and § 102(b) on-sale-bar summary-judgment rulings issued), and the two December 2025 CAFC appeals (26-1277, 26-1280) were pending as of the date of this report.

Caveat: I did not find litigation involving the '872 patent against any party other than Cisco/Acacia. IPR2022-01283 (appeal 2024-1728) was consolidated with the '872 IPR appeals but may involve a family member patent (e.g., the '998 patent); I could not confirm its specific patent from the available sources before hitting the search limit.

Proceedings overview

The USPTO ODP block says "no AIA trial proceedings on file" — but that ingest is stale. Web search confirms two Inter Partes Reviews against US 11,133,872, both filed by Cisco Systems, Inc. (with Acacia Communications, Inc.), both fully instituted, both ending in Final Written Decisions invalidating every challenged claim, and both affirmed by the Federal Circuit on 2026-04-13. Together the two IPRs covered the patent's entire claim set (claims 1–30). Status breakdown: 0 active, all 30 claims invalidated, 0 settled, 0 institution denied.

Bottom line for a defendant: this patent is dead. Every claim of US 11,133,872 was canceled at the PTAB and the cancellation is now final after a Federal Circuit affirmance — Ramot cannot enforce this patent against anyone. If you are being demanded on this patent, the demand has no surviving claim to hang on.

IPR2022-00575 — Cisco Systems, Inc. et al. v. Ramot at Tel Aviv University, Ltd.

• Type: Inter Partes Review
• Filed: 2022-02-16
• Status: Final Written Decision — Appealed (appeal since resolved — CAFC affirmed 2026-04-13)
• Judge panel: Monica S. Ullagaddi (author of the FWD), Christopher L. Crumbley, Jason M. Repko
• Petition grounds: Claims 1–12, 15–22, and 30 of US 11,133,872, challenged on prior-art grounds (35 U.S.C. § 102/§ 103). I could not verify the specific reference names from the public docket summaries in my search window — the petition was supported by a declaration (Ex. 1003 in the parallel proceeding) — so I won't name art I can't confirm.
• Institution decision: Instituted on 2022-10-05 — the Board instituted on the grounds set forth in the Petition for each challenged claim.
• Final Written Decision (2023-09-29): The Board found the challenged claims unpatentable. I was unable to pull the full FWD text for a verbatim quote before hitting my search limit, but the outcome is independently confirmed: the recorded basis of termination is "Unpatentable," and the Federal Circuit's 2026 affirmance necessarily upholds the cancellation. Claims 1–12, 15–22, and 30 were canceled.
• Settlement / termination: No settlement — litigated to a final decision.
• Appeal: 2024-1726, consolidated with 2024-1727 (IPR2022-00576) and 2024-1728 (IPR2022-01283, a sibling patent). Argued by Haynes & Boone for Cisco; Bunsow De Mory for Ramot. Affirmed per Fed. Cir. R. 36 on 2026-04-13 (per curiam: Moore, C.J., Mayer, Lourie) — no written opinion (CAFC Rule 36 judgment PDF; Justia copy).
• Defensive value: Claims 1–12, 15–22, and 30 are canceled with appellate finality. Any infringement theory built on those claims is sanction-bait.

IPR2022-00576 — Cisco Systems, Inc. et al. v. Ramot at Tel Aviv University Ltd.

• Type: Inter Partes Review
• Filed: 2022-02-16 (same day as IPR2022-00575 — coordinated split of the claim set)
• Status: Final Written Decision — Appealed (appeal since resolved — CAFC affirmed 2026-04-13)
• Judge panel: Monica S. Ullagaddi (author), Christopher L. Crumbley, Jason M. Repko
• Petition grounds: Claims 13, 14, and 23–29 — the claims not challenged in IPR2022-00575 — on prior-art grounds (§ 102/§ 103), supported by the Declaration of Dr. Daniel J. Blumenthal (Ex. 1003). Specific reference identities not confirmed in my search.
• Institution decision: Instituted on 2022-10-05 for every challenged claim on the ground set forth in the Petition. Ramot's rehearing request and Precedential Opinion Panel (POP) review request were denied (POP denial 2023-02-22; combined rehearing/supplemental-information denial 2023-05-22, DocketAlarm copy of the decision).
• Final Written Decision (2023-10-03): Challenged claims 13, 14, and 23–29 found unpatentable and canceled (same outcome confirmation path as IPR2022-00575; no verbatim FWD quote available from my searches).
• Settlement / termination: None — litigated to final decision.
• Appeal: 2024-1727, consolidated with 2024-1726 and 2024-1728; affirmed per Rule 36 on 2026-04-13 (same judgment as above).
• Defensive value: The remaining claims of 11133872 — 13, 14, and 23–29 — are canceled with finality. Combined with IPR2022-00575, no claim of this patent survives.

Related, non-PTAB context (not a proceeding on this patent)

• IPR2022-01283 (Cisco et al. v. Ramot, filed 2022-07-20; FWD 2024-02-20; appeal 2024-1728, affirmed in the same 2026-04-13 Rule 36 judgment) was directed to US 11,342,998 — the immediate continuation in the same family — not to 11133872. It's included here only because the CAFC consolidated it with the two appeals above.
• Delaware district court: Cisco/Acacia filed DJ actions (1:21-cv-01365, 1:22-cv-00674, D. Del.); Judge Gregory B. Williams ruled on 2024-11-12 that certain claims of the '998 family patent are indefinite (claims 45–47, 49–54) while others were not (claims 1, 4, 6–15, 58, 61–63). CAFC dockets 26-1280 and 26-1277 (listed on Google Patents) are district-court appeals in that family litigation — not PTAB proceedings.
• Caveat on the ODP data: the structured block in this prompt reports no AIA trials, which conflicts with the two confirmed IPRs above. The Google Patents litigation annotations and Patexia/DocketAlarm records are consistent with each other and with the CAFC judgment; treat the ODP "none" as stale indexing.

Strategic summary

Canceled vs. sustained vs. untested. Every claim of US 11,133,872 is CANCELED. IPR2022-00575 killed claims 1–12, 15–22, and 30; IPR2022-00576 killed claims 13, 14, and 23–29. That is all 30 claims — there are zero surviving claims and zero untested claims. The two FWDs were affirmed by the Federal Circuit (Rule 36, 2026-04-13), so the cancellation is final and the patent is unenforceable. Note the oddity worth flagging to any client: the USPTO ODP API shows no AIA proceedings, so a quick ODP-based diligence pass will miss the two IPRs that invalidated the patent — always cross-check PTAB E2E and the assignment/litigation records.

Estoppel landscape. Under 35 U.S.C. § 315(e)(2), Cisco and its privies (including Acacia) are estopped from raising in district court any ground they raised or reasonably could have raised in these IPRs — but that is moot as to 11133872 because there are no claims left to assert. For a new defendant (not Cisco/privy), estoppel doesn't bind, but it doesn't matter either: with all claims canceled, there is nothing to defend against on this patent. The live exposure, if any, sits in the continuation family: US 11,342,998 (partially invalidated for indefiniteness in Delaware, on appeal at the CAFC), US 11,716,148, US 12,191,912, US 12,388,533, and pending application US 2025/0350366 A1. Those are the claims a fresh demand letter is more likely to cite.

Pattern signals. This is a textbook coordinated campaign by one petitioner, Cisco (joined by Acacia) — two same-day IPRs splitting the claim set of 11133872 (a deliberate strategy to keep each petition under the word limits and map the full claim set), plus a third IPR on the '998 continuation. Ramot defended hard at every turn: preliminary response, rehearing requests, a POP review request, a motion to submit supplemental information, and a CAFC appeal — all denied or affirmed. Unified Patents appears on the Google Patents annotations only as the litigation-data provider, not as a petitioner; do not attribute the IPRs to a defensive aggregator. Cisco's willingness to push through to a CAFC appeal and its current appeals in the family litigation signal that the optical-DAC space is being actively cleared — and that Ramot's broader portfolio (the '998 patent, now partially indefinite in Delaware) remains the real battleground.

Recommended next steps

1. If you're a defendant on 11133872 today: file the answer and move to dismiss or for judgment on the pleadings. All 30 claims are canceled with appellate finality. Cite the CAFC judgment (24-1726/27/28, entered 2026-04-13) and pull the two FWDs from PTAB E2E (IPR2022-00575, decision 2023-09-29; IPR2022-00576, decision 2023-10-03) to attach the claim-by-claim dispositions. Demand letters citing this patent are now baseless; if one cites family continuations instead, pivot to the Delaware indefiniteness ruling on the '998 patent and monitor CAFC dockets 26-1280/26-1277.
2. No active PTAB milestones — both trials are fully concluded, so there are no pending institution-decision deadlines, oral hearings, or FWD due dates to track for this patent.
3. Diligence correction: because the ODP API shows no proceedings for this patent, make sure any internal IP-diligence process for the Ramot optical-DAC family also checks PTAB E2E directly and the continuation patents — the invalidated '872 patent is a signal that the remaining family members are vulnerable and are being attacked.

Source caveat: I confirmed the two IPRs, their docket dates, panels, claim splits, the CAFC consolidation, and the Rule 36 affirmance from public web sources (Patexia, DocketAlarm, CAFC, Justia, PatSnap). I could not retrieve the full FWD texts before the search limit, so the claim-level "unpatentable" findings are reported from the recorded termination basis and the CAFC affirmance rather than direct FWD quotes — pull the FWD PDFs from PTAB E2E before citing them in a filing.

I'll research the assignment/ownership record for US 11,133,872 before producing the analysis.

I hit the search-step limit while trying to pull the 2019 Assignment Center entry directly. Here is the reconstruction based on the records I did retrieve, with explicit flags on what is verified versus unconfirmed.

Ownership & Assignment Analysis — US 11,133,872 B2 ("Linearized optical digital-to-analog modulator")

Primary sources checked: Google Patents legal events for US 11,133,872 and family member US 8,044,835; the prosecution file-history excerpt in the Cisco IPR record (Ramot Ex. 2013 / CISCO 1002); Ramot's technology-offer listing; Unified Patents portal. USPTO Assignment Center itself (https://assignmentcenter.uspto.gov/ ; https://assignment.uspto.gov/patent/index.html) could not be live-queried inside my search budget — reel/frame values below are the ones that surfaced from indexed legal-event data, and one entry could not be confirmed at all.

Inventors

Pattern note: No unusual departure pattern is determinable. These are university researchers, not employees of a startup that wound down. The only "unusual" feature worth flagging is the inventor-to-assignee assignment was executed on the original 2009 application (12/636,805) — signing dates 2009-12-07 to 2009-12-13 — long before the '872 continuation was even filed. There is no evidence of inventors departing an operating company or a portfolio fire-sale. (I cannot determine any inventor's post-2019 employment from the records retrieved.)

Original assignee

Ramot at Tel Aviv University Ltd. (Tel-Aviv, Israel) — the technology-transfer company of Tel Aviv University, named as both original and current assignee on the face of the patent.

• Primary line of business: University technology transfer — IP protection, licensing, and commercialization of TAU faculty/student inventions. Ramot self-describes as "Tel Aviv University's (TAU) technology transfer company and its liaison to industry… providing the legal and commercial frameworks for inventions made by TAU faculty, students and researchers."
• Did they ship a product embodying the claims? No. Ramot's own commercialization vehicle for this invention is a licensing offer, not a product. The technology was marketed via Innoget as "High Speed Photonic Digital-To-Analog Conversion," Project ID 7-2009-59, describing a "novel integrated optical modulator based on a multi-electrode Mach-Zehnder modulator… developed at Tel-Aviv University," with a stated "final product expected" of a "high speed integrated chip optical modulator" — i.e., a licensee would build it. There is no evidence Ramot manufactured or sold anything.
• Current status: Operating. Ramot remains an active TTO and is the named assignee across the family (US 8,044,835; 8,797,198; 9,031,417; 9,203,425; 9,479,191; 10,205,527; 10,270,535; 11,342,998; 11,716,148; 12,191,912; 12,388,533; and pending US 2025/0350366 A1). Not acquired, dissolved, or in bankruptcy — SEC filings are not applicable (a private Israeli university subsidiary is not an SEC registrant).

Assignment timeline

The Assignment Center record for this patent is sparse: the only chain-of-title event is the original inventor-to-university assignment, and it was recorded against the 2009 parent application and carried forward by the continuations. There is no recorded post-issuance transfer of US 11,133,872 — that is itself the finding (Ramot still owns it).

• 2009-12-07 … 2009-12-13 (executed) / recorded on or about December 2009 — Reel 023715 / Frame 0801

  • Conveyance: Assignment (Assignment of Assignors' Interest)
  • Assignor: Yossef Ehrlichman; Ofer Amrani; Shlomo Ruschin (individually)
  • Assignee: Ramot at Tel Aviv University Ltd., Tel-Aviv, Israel
  • Correspondent: Not confirmed from the Assignment Center entry. The correspondence address of record on the prosecution file at that period is Martin D. Moynihan d/b/a PRTSI, Inc., P.O. Box 16446, Arlington, VA 22215 — a plausible assignment correspondent, but I could not verify it appears on the reel 023715/0801 cover sheet. Flagged as unverified.
  • Context: Original technology-transfer assignment — the standard university route by which faculty/student inventors convey rights to TAU's TTO. Not a sale, not securitization, not a transfer to an asserter.
  • Source: Google Patents legal events for US 8,044,835 (the first patent in the family, same inventors): "ASSIGNMENT OF ASSIGNORS INTEREST; ASSIGNORS: EHRLICHMAN, YOSSEF; AMRANI, OFER; RUSCHIN, SHLOMO; SIGNING DATES FROM 20091207 TO 20091213; REEL/FRAME: 023715/0801."

• 2019-09-12 (recorded) — Reel/Frame: NOT OBTAINED

  • Conveyance: Assignment / reassignment recordation carried with the continuation application 16/532,567
  • Assignor: Shlomo Ruschin; Ofer Amrani; Yossef Ehrlichman
  • Assignee: Ramot at Tel-Aviv University Ltd.
  • Correspondent: Not obtained.
  • Context: Formal recordation of the standing inventor→Ramot assignment against the '872 application; same three inventors, same assignee — not a change of ownership.
  • Source: Google Patents legal-event entry "2019-09-12 Assigned to RAMOT AT TEL-AVIV UNIVERSITY LTD., reassignment; Assignors: RUSCHIN, SHLOMO, AMRANI, OFER, EHRLICHMAN, YOSSEF." Reel/frame was not exposed in the data I retrieved.

• No further assignments recorded. No transfer to any LLC, holding company, SPV, aggregator, or litigation vehicle. No security agreement, merger, change of name, or release on record.

⚠️ Discrepancy flag: the earlier-generated "Patent summary" section in this analysis states the prosecution firm was Artegis Law Group, LLP. The Cisco IPR file-history exhibit I retrieved (application 15/298,327) shows the USPTO correspondence address as Martin D. Moynihan d/b/a PRTSI, Inc., Arlington, VA. These may reflect different periods (PRTSI earlier, Artegis later) or one source may be imprecise — either way, verify the counsel-of-record and the assignment correspondent independently before citing in a filing.

Timeline diagram

timeline
    title Ownership of US 11133872
    2007 : Provisional filed Jun 13
    2009 : Inventors assign rights to Ramot
         : Reel 023715 Frame 0801
    2019 : Continuation 16 532 567 filed Aug 6
         : Assignment re-recorded Sep 12
    2021 : Patent issues Sep 28
         : Cisco and Acacia file DJ suit
    2022 : IPRs filed Feb 16
    2023 : PTAB cancels all 30 claims
    2026 : CAFC Rule 36 affirmance

NPE / troll-pattern signals

Verdict

Insufficient data — and, on the evidence available, not an NPE/troll fact pattern.

Among the eight enumerated NPE signals, none is present; the evidence affirmatively negates the classic pattern (0 shell transfers, 0 cascading assignments, 0 pre-litigation transfers, no known asserter, no defensive aggregator). Consequently no NPE classification (high or moderate) is supportable, and this is not an "operating-company assertion" either, because Ramot does not ship a product embodying the claims — it licenses them (Innoget Project ID 7-2009-59). The record contains only the original inventor→Ramot assignment (reel 023715/0801, executed 2009-12-07 to 2009-12-13, plus the unverified 2019-09-12 re-recordation), which is the literal definition of the "Insufficient data (only the original assignment)" category — though here it is a finding of benign ownership, not a gap: the original assignee simply still owns the patent.

So what is this really? A university technology-transfer entity asserting its own patent against a large commercial vendor (Cisco/Acacia). It is non-practicing, but that is an artifact of being a TTO, not of troll economics: it acquired nothing, it flipped nothing, and it is not a repeat shell-LLC plaintiff. Any "NPE" framing of Ramot would be a naming-based inference the evidence does not support.

Verification links:

• USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search patent 11133872)
• Legacy assignment search — https://assignment.uspto.gov/patent/index.html
• Google Patents legal events — https://patents.google.com/patent/US11133872/en

Open items to close before relying on this in a filing:

1. Pull the reel/frame for the 2019-09-12 recordation from Assignment Center (not obtained here).
2. Confirm the assignment-cover-sheet correspondent for reel 023715/0801 (tentatively PRTSI / Martin D. Moynihan; unverified).
3. Resolve the PRTSI vs. Artegis counsel discrepancy flagged above.
4. Search the full family in Assignment Center (11,342,998; 11,716,148; 12,191,912; 12,388,533; and pending US 2025/0350366) — if any family member has been assigned away from Ramot, that would be the first real NPE signal; on the records reviewed, none has.

Let me pull the actual reference list from the Google Patents front page and USPTO records for US11133872B2.

I've reached the step limit for live searching, so let me be precise about what is and is not verifiable from the record I could access.

Prior Art Analysis — US Patent 11,133,872 B2 ("Linearized Optical Digital-to-Analog Modulator")

Important scope caveat

I was not able to retrieve the complete front-page "References Cited" (PTO-1449 / examiner citation) list for US11133872B2 in this session before hitting the search limit. The analysis below therefore distinguishes three tiers of evidence:

1. References the specification itself identifies as prior art (certain — quoted in the patent's Field and Background section and incorporated in the prosecution record).
2. Non-patent literature visible in family and citing-document records (high confidence these are on the face of this patent or its immediate parents, but each is flagged).
3. A broader U.S.-patent list retrieved from a family-member patent (US12191912) page, which is not confirmed to be the identical citation list for 11133872 and should be verified against the USPTO Patent Center file wrapper before citation in any filing.

Per Unified Patents, the record for 11133872 shows 69 patent-art items and 71 non-patent literature items attributed to the file — consistent with a heavily continued prosecution chain in which many references accumulated across the 2008 PCT → 2021 grant lineage.

Tier 1 — References identified as prior art in the patent's own specification

The Background section of US11133872B2 expressly discusses the following as the state of the art that the invention improves upon. These are the most relevant references for any § 102/§ 103 analysis because the applicant conceded their materiality.

1. US 4,288,785 — "Light intensity modulator with digital control and a digital-analog converter comprising such a modulator" — Papuchon et al. (Thomson-CSF)

2. US 7,061,414 — "Optical digital-to-analog converter" — Chen et al. (Lucent Technologies)

3. Yacoubian et al., "Digital-to-Analog Conversion Using Electrooptic Modulators" — IEEE Photonics Technology Letters, vol. 15, no. 1, pp. 117–119, January 2003

4. Leven et al., "A 12.5 Gsamples/s Optical Digital-to-Analog Converter with 3.8 Effective Bits" — LEOS 2004, 17th Annual Meeting of the IEEE, vol. 1, pp. 270–271, November 2004

Tier 2 — Non-patent literature appearing in the family/citing-document record

The Google Patents records for citing documents (e.g., US 7,277,603 B1) and for the family's earlier members show this NPL set traveling with the Ramot lineage (Leven; Yacoubian; plus the following):

5. M. F. Lewis et al., "A High-Speed D/A Converter Using Optics" — IEE Colloquium on Optical Interconnects, 1998, pp. 1–4 (approximately)

6. M. Papuchon et al., "Bits Digital Driven Integrated Amplitude Modulator for Data Processing," Electronics Letters, vol. 16, no. 4, pp. 142–144, Feb. 14, 1980

Tier 3 — U.S. patents listed as cited references on a family-member patent (US 12,191,912) — NOT confirmed as 11133872's own citation list

These were retrieved from the Justia "Referenced Cited — U.S. Patent Documents" section of US 12,191,912 (a 2025 continuation in the same family claiming priority to 2007-06-13). The lists overlap heavily with what would be in 11133872's file history but must be verified against the 11133872 file wrapper before use:

US 4,288,785 (Papuchon, Sep. 8, 1981); US 4,613,204 (Verber, Sep. 23, 1986); US 4,649,505 (Zinser, Mar. 10, 1987); US 5,010,346 (Hamilton, Apr. 23, 1991); US 5,137,359 (Steele, Aug. 11, 1992); US 5,418,976 (Iida, May 1995); US 5,543,952 (Yonenaga, Aug. 6, 1996); US 5,625,722 (Froberg, Apr. 29, 1997); US 5,694,504 (Yu, Dec. 2, 1997); US 5,724,178 (Grandpierre, Mar. 3, 1998); US 5,917,638 (Franck, Jun. 29, 1999); US 5,977,899 (Adams, Nov. 2, 1999); US 6,326,910 (Hayduk, Dec. 4, 2001); US 6,337,755 (Cao, Jan. 8, 2002); US 6,760,111 (Mark, Jul. 6, 2004); US 6,781,537 (Taraschuk, Aug. 24, 2004); US 6,781,741 (Uesaka, Aug. 24, 2004); US 7,061,414 (Chen, Jun. 13, 2006); US 7,146,109 (Chen, Dec. 5, 2006); US 7,167,651 (Shpantzer, Jan. 23, 2007); US 7,173,551 (Vrazel, Feb. 6, 2007); US 7,203,552 (Solomon, Apr. 10, 2007); US 7,212,292 (Vanbrocklin, May 1, 2007); US 7,277,603 (Roberts, Oct. 2, 2007); US 7,308,210 (Khayim, Dec. 11, 2007); US 7,403,711 (Chen, Jul. 22, 2008); US 7,483,597 (Shastri, Jan. 27, 2009); US 7,536,112 (Yonenaga, May 19, 2009); US 7,609,935 (Burchfiel, Oct. 27, 2009); US 7,792,398 (Tanaka, Sep. 7, 2010); US 7,873,284 (Chen, Jan. 18, 2011); US 7,881,354 (Yoshikawa, Feb. 1, 2011); US 7,978,390 (Kikuchi, Jul. 12, 2011); US 8,044,835 (Oct. 25, 2011) — plus the intermediate family patents (8,797,198; 9,031,417; 9,203,425; 9,479,191; 10,205,527; 10,270,535; 10,433,566; 10,461,866; 11,133,872; 11,342,998).

The immediately most relevant to the 11133872 claims among this group (beyond Tier 1) are likely US 7,277,603 (Roberts et al.) and US 7,873,284 / US 7,403,711 / US 7,146,109 (Chen et al. — Lucent optical DAC family) and US 6,760,111 (Mark) — all pre-2007 optical-modulator/DAC art. But I could not confirm their presence on the 11133872 front page specifically.

Claim-by-claim § 102 anticipation summary (what can be said with confidence)

Bottom line

The four references the applicant itself concedes as the prior art — US 4,288,785 (Papuchon), US 7,061,414 (Chen/Leven), Yacoubian 2003, and Leven 2004 — are the most relevant prior art, and they correspond exactly to the art the specification says the invention overcomes. For a rigorous § 102 anticipation argument against the independent claims (1, 11, 13, 15), none of these singly discloses the defining feature set (M>N digital-to-digital mapping chosen to linearize the modulator response). The IPR petitions (IPR2022-00575/00576) that ultimately invalidated all 30 claims necessarily relied on these or closely related references in § 102/§ 103 combinations, and the specific ground/reference identifications are in the PTAB E2E records for those cases.

Recommended verification steps (unresolved)

1. Pull the file wrapper / front-page "References Cited" for US11133872B2 from USPTO Patent Center (application 16/532,567) to obtain the authoritative, complete citation list — including any references I could not confirm here.
2. Pull the IPR2022-00575 and IPR2022-00576 petitions and Final Written Decisions from PTAB E2E to identify the exact references and the claim-by-claim grounds (the FWD texts were not retrievable within my search limit).
3. Before citing any Tier-3 patent (e.g., US 7,277,603; US 7,873,284; US 7,403,711) as "cited in 11133872," confirm it appears on the 11133872 citation list and not only on the later continuation US 12,191,912.

I have enough verified information from the search results to deliver this analysis. Note upfront: the searches confirm that IPR2022-00575's instituted Ground 1 was obviousness under pre-AIA 35 U.S.C. § 103(a) over Roberts (U.S. 7,277,603) + Taraschuk (U.S. 6,781,537) against claims 1–12, 15–22, and 30, and that the PTAB's Final Written Decisions were affirmed by the Federal Circuit on April 13, 2026 (Rule 36). My analysis below builds the § 103 case from the ground up, centered on that prevailing combination, and adds secondary reference combinations that the record shows were in play for dependent and method limitations. I could not retrieve the full FWD texts or the specific ground chart for IPR2022-00576 (claims 13, 14, 23–29) before the search limit, so the portions depending on that proceeding are flagged as such.

Obviousness Analysis of U.S. Patent 11,133,872 Under 35 U.S.C. § 103

1. Legal framework

Obviousness under § 103 is assessed through the Graham factors: (1) the scope and content of the prior art; (2) the differences between the prior art and the claimed invention; (3) the level of ordinary skill in the field; and (4) objective indicia of non-obviousness. Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), a combination of familiar elements is obvious when it yields predictable results, and the analysis must account for the "interrelated teachings of multiple patents," the "effects of demands known to the design community," and the "background knowledge possessed by a person having ordinary skill in the art."

The '872 patent itself concedes the core problem and the state of the art: Mach-Zehnder (MZI) modulators have an inherent cosine transfer function, and prior multi-electrode DAC attempts (Papuchon U.S. 4,288,785 — power-of-two segmented electrodes; Yacoubian 2003 — one MZI per bit; Leven 2004 / Chen U.S. 7,061,414 — one modulator per two bits) all failed to linearize adequately. The patent's asserted solution is not a new physical device, but a mapping strategy: route N input bits through a digital-to-digital mapping into M > N drive bits chosen per input word to "alter the linearity" of the modulator's optical response (claims 1, 11, 15), and, in claim 13, define the mapping mathematically so that successive output step-sizes (deltas) shrink in some input regions and grow in others — the characteristic signature of an inverse-cosine compensation table.

2. Person of ordinary skill in the art (POSITA)

A POSITA would have a B.S./M.S. in electrical engineering, physics, or optical engineering (or equivalent industry experience), with 3–5 years working on optical transmitters, external modulators (MZI and electro-absorption), high-speed mixed-signal electronics, and digital signal processing for fiber-optic or RF-over-fiber links. Such a person would be fluent in: (i) the cos² transfer function of MZI modulators; (ii) segmented/multi-electrode modulator drive; (iii) digital pre-distortion and look-up-table linearization; and (iv) the standard reference texts in the record (Saleh & Teich, Fundamentals of Photonics; Agrawal, Fiber-Optic Communication Systems; Kaminow et al., Optical Fiber Telecommunications).

3. Scope and content of the prior art

Primary references (the prevailing IPR ground)

Roberts — U.S. Patent 7,277,603 ("Optical transmission system...")
Roberts is directed to optical transmission using a multi-electrode Mach-Zehnder modulator. A digital signal processor (DSP 34) computes multi-bit drive sample streams V_R(n) and V_L(n), and a non-linear compensator 18 computes those streams "taking into account non-linearities of ... the MZ modulator 4, such that ... the output of the MZ modulator 4 closely matches the target E-field modulation." The electrodes produce phase delays that "vary directly with the number of active electrodes on that branch." Roberts is squarely analogous art: same field (optical communications), same device (MZ modulator), same problem (compensating the modulator's nonlinear transfer function via digitally computed drive signals).

Taraschuk — U.S. Patent 6,781,537 ("High resolution WDM...") (as characterized in the IPR petition)
Taraschuk teaches a linearizer 44 for an optical modulator 52 (including a Mach-Zehnder modulator). Critically, Taraschuk discloses a digital-to-digital mapping from an M-bit input digital signal 46 to an N-bit signal 60 with N > M (e.g., six input bits mapped to eight drive bits), "which compensates for the combined non-linear effects of ... the sinusoidal response of the modulator." This is, element-for-element, the "expand the word width via a lookup-style mapping chosen to counteract the cosine response" concept that the '872 claims capture.

Secondary references in the IPR record (Exhibit list, IPR2022-00575 petition)

• Zinser — U.S. 4,649,505: analog/digital conversion and linearization in a modulation context (Ex. 1019).
• Iida — U.S. 5,418,976: driving an optical/electro-optical device with digital control (Ex. 1020).
• Kurahashi — U.S. 6,548,824: optical modulator control circuitry (Ex. 1021).
• Ackerman et al., "Bias Controllers for External Modulators..." (Ex. 1014): operating-point/bias control to manage modulator distortion.
• Bridges et al., "Distortion in Linearized Electrooptic Modulators" (Ex. 1018): taxonomy of nonlinear distortion mechanisms in electrooptic modulators and linearization techniques.
• Ho, Phase-Modulated Optical Communication Systems (Ex. 1007); Saleh (Ex. 1013); Kaminow (Ex. 1012); Agrawal (Ex. 1015): standard treatises establishing what a POSITA knew about modulator transfer functions, fiber-induced nonlinearity, and drive architectures.
• Gauck, "Comparison of Direct and External Modulation for CATV..." (Ex. 1017): relevant to claims directed at light-generating/direct-modulation embodiments (claim 15 family).

References already cited as background in the '872 patent itself

• Papuchon U.S. 4,288,785: multi-electrode MZI DAC with power-of-two segmented electrodes (the admitted starting point the patent tries to improve).
• Yacoubian et al., IEEE PTL 15:117–119 (2003): one MZI per bit.
• Leven et al., LEOS 2004; Chen U.S. 7,061,414: one modulator per two bits, "highly nonlinear" (3.8 effective bits).

None of the background references teach away from digital-domain mapping linearization; they merely failed to implement it well, which is exactly the gap Roberts and Taraschuk fill.

4. Combination 1 (prevailing ground): Roberts + Taraschuk → claims 1–12, 15–22, 30

Claim 1 element-by-element mapping

Every element of claim 1 is present: Taraschuk supplies the M > N digital-to-digital mapping with per-input-word output selection tuned to the modulator's sinusoidal response; Roberts supplies the multi-electrode MZ modulator in a fiber transmission system with digitally computed, nonlinearity-compensated drive patterns. The claim adds nothing beyond joining these two known teachings.

Why a POSITA would combine them (motivation + reasonable expectation of success)

1. Same problem, complementary solutions. Both references sit in optical transmission and both target the MZI cosine nonlinearity. Roberts solves it at the signal-computation level (compute analog multi-bit drive values that pre-compensate), Taraschuk at the code-mapping level (expand an input word to a larger drive word through a defined table). A POSITA reading Roberts who needed a cleaner digital implementation would naturally consult Taraschuk's linearizer — the two are the digital-domain and mapping-domain halves of the same design task.
2. Direct incentive to use M > N. Taraschuk's own example (6→8 bits) teaches that expanding the drive-word width gives extra degrees of freedom to place output levels on the desired linear grid — precisely the redundancy the '872 specification says M > N provides (the patent admits duplicate representations arise with M = N and are "effectively mitigated by choosing M>N"). The '872 patent's claimed M > N limitation is thus Taraschuk's express teaching, not an invention.
3. Obvious substitution in a known architecture. Roberts already has a DSP computing drive streams for a segmented MZ modulator. Replacing Roberts' direct digital computation with Taraschuk's lookup/mapping (or feeding Roberts' compensator output through Taraschuk's mapping) is a routine implementation choice — "combining familiar elements according to known methods ... [that] yields predictable results" (KSR). The output — a linearized optical DAC — is the predictable sum of the two references' stated goals.
4. No teaching away; no unexpected result. The '872 patent's own Background describes prior segmented-electrode DACs as inadequate, not as incompatible with mapping linearization. Nothing in Roberts or Taraschuk discourages their combination, and the claimed "alter[s] the linearity" language is a functional restatement of what both references' compensation circuits do by design.

Dependent claims 2–10 and 30 (representative)

• Claims 2, 5–10 (correction of modulator and/or fiber nonlinearities): Roberts' nonlinear compensator expressly targets modulator nonlinearity so the transmitted field matches the target; Roberts and the standard texts (Ackerman, Bridges, Agrawal, Ho) all treat fiber propagation distortion as a known further nonlinearity that drive-side pre-compensation can address. Taraschuk likewise states its mapping "can also be used to compensate non-linearities of the optical modulator" and related components.
• Claim 3 (MZI-based modulator): disclosed by both Roberts (MZ modulator 4) and Taraschuk (modulator 52 "such as ... a Mach-Zehnder modulator").
• Claim 4 (converter comprises a digital-to-digital converter): Taraschuk's linearizer is by definition a digital-to-digital mapping device; the '872 patent's own definition of "digital-to-digital converter" (a nontrivial mapping where bits are not one-to-one) describes Taraschuk's 6→8 mapping verbatim.
• Claims 15–22 (semiconductor light-generating device embodiment): the light-source/direct-modulation architecture is standard (Gauck's CATV direct-vs-external modulation comparison; laser/LED drive literature, e.g., Iida), and once the M > N digital-to-digital mapping concept from Taraschuk is applied to a digitally sectioned laser/LED drive electrode — which the '872 patent's Figure 9 embodiment itself describes as needing no more than area-weighted electrodes — the claim adds only conventional hardware. The mapping still does the linearity work.

Disposition: The PTAB instituted and, in its Final Written Decision (Sept. 29, 2023), found claims 1–12, 15–22, and 30 unpatentable on this ground; the Federal Circuit affirmed (Rule 36, April 13, 2026). The record therefore confirms that Combination 1 is not merely colorable — it is legally sufficient and has withstood appeal.

5. Combination 2: Roberts + Taraschuk (and/or + Zinser/Iida/Kurahashi) → claims 13, 14, 23–29

Claim 13 is a method claim that characterizes the mapping geometrically: for a first subset of successively decreasing input words the deltas between successive mapped output values decrease, and for a second subset they increase. This is not an arbitrary constraint — it is the necessary shape of any inverse-cosine (or inverse-sinusoidal) compensation table. Explanation:

• An MZI's power output is cos²(φ/2), which is concave near its minima/maxima and steepest near its quadrature point. To produce uniformly spaced optical output levels, the drive-word increments must be large where the transfer function is flat and small where it is steep — i.e., the mapped deltas must decrease across one portion of the input range and increase across another.
• Taraschuk's linearizer, by construction ("compensates for ... the sinusoidal response of the modulator"), produces exactly such a non-uniform mapping; Roberts' nonlinear compensator, which shapes drive values so the modulator output "closely matches" a linear target, implies the same delta profile.
• A POSITA deriving the mapping table for claims 13/14 would, in the most routine way, invert the modulator transfer function (a standard exercise found in Bridges, Saleh, and the linearization literature), and that inversion necessarily yields the claimed alternating delta behavior. The claim therefore captures an inherent mathematical property of applying the admitted prior-art linearization technique, not a new structure.

Dependent claims 23–29 (and any claims 18–30 not in view) add further limitations I could not fully retrieve in the source text. To the extent they recite QAM/constellation operation, return-to-zero (RZ) signaling, dynamic-range spanning, common two-level actuation voltages, and electrode-area relationships, those features are either (a) inherent to driving segmented modulators with binary voltages (Roberts; Papuchon; Chen 7,061,414) or (b) supported by Zinser, Iida, and Kurahashi, which the petitioner placed in the record as secondary references. Caveat: I could not retrieve IPR2022-00576's specific ground chart before the search limit; the institution and Final Written Decision (Oct. 3, 2023) did find claims 13, 14, and 23–29 unpatentable, and the CAFC's Rule 36 affirmance covered that decision as well — so the outcome for Combination 2's target claims is confirmed even though I cannot verify the exact reference pairing the Board adopted.

6. Combination 3 (fallback, if a tribunal rejects Roberts/Taraschuk as primary): Papuchon (4,288,785) or Chen (7,061,414) + Taraschuk

For completeness — and because the '872 patent itself admits these as the closest prior DAC architectures — a POSITA seeking to improve Papuchon's power-of-two segmented MZI DAC (which the patent criticizes only for non-linearity, not for the segmented-electrode concept) would:

1. Recognize the failure mode as the uncompensated cosine response (explicitly diagnosed in the '872 Background and in Bridges' distortion taxonomy);
2. Apply Taraschuk's digital-to-digital linearizing mapping (6→8 bit expansion) ahead of Papuchon's electrode array to re-place each input word at the electrode pattern whose optical output lands nearest the desired linear level;
3. Arrive at every structural element of claims 1, 11, 13, and 15.

The patent's own Figures 2A→2B narrative — "for each input value, pick the actuation pattern whose output is closest to the ideal linear point" — is literally the algorithm Taraschuk's linearizer executes. The Roberts+Taraschuk combination remains the strongest ground, but Taraschuk paired with any segmented-electrode optical DAC reference yields the same conclusion, which is why the family's reexaminations (referenced in the IPR petition as ongoing against the continuation patents) reached consistent rejections.

7. Secondary considerations

No objective indicia favoring patentability were identified in the record that would outweigh the strong prima facie case: the invention was not commercially adopted by Ramot as a standalone product (the record shows licensing/enforcement, not practice), the "long-felt need" for linear optical DACs is conceded in the patent itself and was unmet precisely because the prior art (as the patent admits) had not applied digital-domain mapping — which Roberts and Taraschuk had — and there is no evidence of unexpected results, skepticism, or praise. The PTAB's unpatentability findings and the CAFC's affirmance are consistent with the absence of such evidence.

8. Conclusion

Under § 103, the claims of U.S. 11,133,872 are obvious as a matter of law over Roberts (U.S. 7,277,603) in view of Taraschuk (U.S. 6,781,537), with Taraschuk supplying the M > N digital-to-digital linearization mapping and Roberts supplying the multi-electrode MZ modulator/fiber-transmission context — the exact ground the PTAB adopted and the Federal Circuit affirmed on April 13, 2026. A POSITA would have been motivated to combine them because they solve the same MZI-cosine-nonlinearity problem in complementary, non-conflicting ways, and the combination yields the predictable result of a linearized optical digital-to-analog modulator. Secondary references (Zinser, Iida, Kurahashi, Ackerman, Bridges, Gauck, and the standard treatises) reinforce the obviousness of dependent and method limitations, including the delta-profile claim (claim 13), which merely describes the mathematical shape that any inverse-cosine compensation table must take. The absence of any surviving claim — all 30 canceled and affirmed — means the § 103 analysis is now of historical/diligence value, but it is decisive: the claims were obvious, and the final judgment of the PTAB and Federal Circuit confirms it.

Remaining uncertainties: (i) exact reference-to-limitation charts in IPR2022-00576 and the content of claims 18–30 were not retrievable within the search budget; (ii) the specific roles of Zinser/Iida/Kurahashi in the petitions are inferred from the exhibit list and dependent-claim features, not verified from ground charts; and (iii) no full FWD text was quoted — the unpatentability outcome is confirmed from the recorded termination basis, the institution order language quoted in the petition excerpt, and the CAFC judgment.