WDM Systems Patents: Who Leads, Where the Gaps Are 2026
- Filing has cooled since its 2023 peak. 56 families in 2023 against 48 in 2017 and a partial 4 in 2026 points to a mature, already-claimed core rather than an expanding frontier.
- H04J and H04B dominate, but G02B is close behind. 1,357 and 1,113 records sit in multiplex-communication and general transmission classes, while 1,084 sit in optical elements — the physical layer is as contested as the signalling layer.
- Every tracked leading assignee shows zero filings in the latest year. Fujitsu, NTT, Huawei, Alcatel, NEC and Furukawa all read 0 for the most recent year, though publication lag of roughly 18 months means this understates true recent activity.
Filing growth compares 2021 (54 records) with 2024 (27) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 2,235 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This landscape tracks 2,235 patent families published between 2015 and mid-2026 that combine wavelength division multiplexing or DWDM system claims with specific technical limitations — channel spacing, crosstalk, flex grid, spectral efficiency or amplifier gain flatness — inside the core optical and transmission IPC classes. The search string is deliberately narrow: it excludes generic optical-communication filings that never engage with the spacing, flatness or grid problems that define modern DWDM engineering.
Coverage spans the United States, EPO, WIPO/PCT, Japan, China and Canada as receiving offices, giving a multi-jurisdiction view of where applicants actually seek protection rather than just where they are headquartered. Because publication lags filing by roughly 18 months, the last one to two years in any trend chart will always look lighter than they eventually turn out to be.
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Filing trends and technology composition
Two views of the same 2,235-family dataset: how filing volume moved year over year, and which IPC subclasses carry the claim density.
A peak in 2023, then decline
Filings rose from 48 in 2017 to a peak of 56 in 2023, with 43 at the 2022 midpoint. The drop to 4 by 2026 is partly a publication-lag artefact, but the flat-to-declining shape since 2022 suggests the easy claim territory in core WDM signalling has largely been staked out.
Multiplexing and transmission classes dominate
H04J (multiplex communication) leads with 1,357 records, followed by H04B (transmission, general) at 1,113 and G02B (optical elements and systems) at 1,084. Smaller but non-trivial activity sits in H01S lasers (214), G02F optical modulation (176), H04Q switching (159), H04L digital transmission (146) and H01L semiconductor devices (35) — evidence that WDM patenting reaches well beyond the multiplexer itself into the laser source and switching fabric around it.
Shares are the percentage of the 2,235 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Wavelength Division Multiplexing Systems with Eureka
This page is one run against one query. Ask Eureka your own question about wavelength division multiplexing systems and every answer comes back with the patent numbers behind it.
Try EurekaThe documents anchoring this field
Optical frequency spectral optimization in DWDM flex grid systems
The filing describes shifting the frequency of individual media channels to close gaps in the optical spectrum and optimise spacing across a dense wavelength division multiplexing flex grid — a computing system approach to spectral assignment rather than a fixed-grid hardware fix.Filed by Level 3 Communications, LLC, 2024-07-11.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US6567573B1 | Switchable optical components | 377 |
| 2 | US6363183B1 | Reconfigurable and scalable intergrated optic waveguide add/drop multiplexing element using micro-opto-electr… | 298 |
| 3 | US4773063A | Optical wavelength division multiplexing/demultiplexing system | 291 |
| 4 | US6310704B1 | Communication apparatus for transmitting and receiving signals over a fiber-optic waveguide using different f… | 269 |
| 5 | US20020048062A1 | Wavelength division multiplexing optical communication system and wavelength division multiplexing optical co… | 231 |
| 6 | US5694234A | Wavelength division multiplexing passive optical network including broadcast overlay | 200 |
| 7 | US5416861A | Optical synchronous clock distribution network and high-speed signal distribution network | 198 |
| 8 | US20050249509A1 | Coolerless photonic integrated circuits (PICs) for WDM transmission networks and PICs operable with a floatin… | 193 |
| 9 | US5550818A | System for wavelength division multiplexing/asynchronous transfer mode switching for network communication | 179 |
| 10 | US6212312B1 | Optical multiplexer/demultiplexer using resonant grating filters | 168 |
Citation counts favour older filings that have had more time to accumulate references; read them as markers of foundational influence, not current relevance.
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Browse MCP servers →What the filing pattern tells you
Three read-throughs from the trend, class and receiving-office data that matter for a filing or freedom-to-operate decision.
The core signalling problem is largely claimed
Volume grew from 48 filings in 2017 to a peak of 56 in 2023 before falling toward 4 in the partial 2026 year. A flat-to-declining trajectory after the 2022 midpoint of 43 filings suggests diminishing returns for applicants filing narrow claims on channel spacing and crosstalk alone.
US filings outweigh the next three offices combined
953 records at the USPTO compare with 407 at the EPO, 218 via WIPO/PCT and 151 in Japan. China sits lower at 125 despite being a major optical-component manufacturing base, which may reflect filing strategy differences rather than R&D volume.
The physical layer rivals the signalling layer
H04J and H04B together account for the bulk of records, but G02B optical elements sit close behind at 1,084 — nearly as many as either signalling class. A filer focused only on multiplexing logic risks missing prior art sitting in optical component claims.
Leading filers show no latest-year output
Fujitsu, NTT, Huawei, Alcatel, NEC and Furukawa each register zero filings in the most recent year, with Huawei showing a -100% YoY change. Given the roughly 18-month publication lag, this signals a reporting gap more than an actual halt — but it does mean the newest strategic moves from these firms are not yet visible in public data.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to wavelength division multiplexing systems, with the prior art for and against each one.
Who holds the claim space
Filing activity concentrates among a small set of telecom-equipment and carrier-scale filers, with collaboration patterns that hint at joint R&D rather than pure competition.
Japanese carriers file jointly with their equipment arms
The strongest co-assignee pair in the dataset links Nippon Telegraph and Telephone with NTT Electronics across 9 families, with a further 4 shared with Hitachi. This points to carrier-and-vendor co-development rather than arm's-length licensing.
Individual-inventor co-filing appears even at large vendors
Huawei's strongest co-assignee link is with an individual inventor, Bai Yusheng, across 3 families — a reminder that named-inventor co-assignment still shows up inside large corporate portfolios in this field.
A long tail sits beneath the recognisable names
Beyond the handful of carrier and equipment names with joint-filing histories, the ranking runs to a long tail of single- or few-filing entrants, typical of a field where component-level improvements are patentable on their own.
| Assignee | Recent year | YoY |
|---|---|---|
| Fujitsu Limited | 0 | — |
| Nippon Telegraph and Telephone Corporation (NTT) | 0 | — |
| Huawei Technologies Co., Ltd. | 0 | -100% |
| Alcatel | 0 | — |
| NEC Corporation | 0 | — |
| Furukawa Electric Co., Ltd. | 0 | — |
| Lightchip, Inc. | 0 | — |
| AT&T Corp. | 0 | — |
Where to take this analysis
The dataset points to specific next steps depending on whether you are filing, defending, or scouting for acquisition targets.
Run a freedom-to-operate check against the G02B cluster
Optical-element claims sit nearly as dense as the signalling classes and are easy to overlook if a search stays confined to H04J terms.
Explore optical component claims in EurekaWatch for the 2024-2026 filings not yet public
Zero latest-year counts across every leading assignee are a publication-lag artefact, not a stop signal; the real picture for 2024-2025 filings will only surface over the next year.
Track assignee activity in EurekaMap the flex-grid spectral optimisation sub-branch
Software-driven frequency reassignment, as seen in the Level 3 filing, is a newer claim style layered on top of established fixed-grid hardware patents.
Search flex-grid filings in EurekaCommon questions on WDM patenting
Filing activity concentrates among a small group of telecom carriers and equipment vendors, including Fujitsu, NTT, Huawei, Alcatel and NEC, based on the 2,235-family corpus tracked here. These firms sit at the top of the assignee ranking but each shows zero filings in the most recent tracked year, which is likely a publication-lag effect rather than an actual stop in filing. Below this group sits a long tail of single- or few-filing entrants, typical of a field where individual optical-component improvements are separately patentable.
The trend data shows growth from 48 filings in 2017 to a peak of 56 in 2023, followed by a decline toward 2026. Because publication lags filing by roughly 18 months, the most recent one to two years understate true activity, but the flat trajectory since the 2022 midpoint of 43 filings suggests the core signalling claim space is largely occupied. New filings are more likely to come from adjacent branches like flex-grid spectral optimisation than from the original channel-spacing and crosstalk claims.
H04J (multiplex communication) and H04B (transmission, general) carry the largest record counts at 1,357 and 1,113 respectively, but G02B (optical elements and systems) is close behind at 1,084 and should not be treated as secondary. Smaller but meaningful activity also appears in H01S lasers, G02F optical modulation, H04Q switching and H04L digital transmission. A search limited to H04J alone will miss a substantial share of relevant prior art sitting in the optical component and laser classes.
This Level 3 Communications filing from 2024 covers a method for optimising spectral spacing in dense wavelength division multiplexing flex grid systems by detecting gaps in the optical spectrum and shifting the frequency of specific media channels to close them. It is a computing-system-level spectral assignment approach layered on top of flex-grid hardware, not a fixed-grid multiplexer design. Anyone building automated spectrum-management software for flex-grid DWDM networks should review its claims closely before shipping similar frequency-reassignment logic.
The evidence points to flex-grid spectral reassignment algorithms, amplifier gain-flatness control spanning multiple amplification bands, and semiconductor-integrated WDM front-ends as comparatively thin relative to the dense core multiplexing and channel-spacing art. These branches sit at the intersection of established IPC classes — G02B, H01S and H01L — rather than inside a single well-claimed subclass. Filing a first claim there means grounding it in a specific hardware or software mechanism rather than a general spacing or crosstalk limitation, since those general limitations are exactly what the dense prior art already covers.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.