How a Special Fiber Stub Cleans Up Light Signals
This patent describes a short piece of optical fiber, called a fiber stub, designed to prevent unwanted light from escaping the fiber's core and interfering with data transmission by using a ferrule with a specific optical property.
Original patent title: “Fiber stub for cladding mode coupling reduction”
This patent describes a short piece of optical fiber, called a fiber stub, designed to prevent unwanted light from escaping the fiber's core and interfering with data transmission by using a ferrule with a specific optical property. Granted to Finisar in 2007 with 26 claims and 81 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
The patent describes a "fiber stub" (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1) used in optical devices like transceivers (Claim 18). This stub has an "optical fiber" with a "core" (where the main light signal travels) and a "cladding" (the layer surrounding the core). Crucially, the stub also includes a "ferrule" (a protective sleeve) made of a material, often glass (Claim 2), that has a "refractive index" greater than the cladding's refractive index (Claim 1). This difference causes unwanted "cladding modes" (light traveling in the cladding) to bend and refract into the ferrule and away from the core (AbstractabstractA short summary at the front of the patent describing the invention. Not legally binding.Read more →). An optional "absorbing layer" on the ferrule's outer surface can then soak up this unwanted light (Claim 5), ensuring a cleaner signal is transmitted. For example, in a 10 Gigabit Ethernet transceiver (Claim 20), this stub helps maintain signal integrity over distances up to 300 meters.
The gap
What does this patent NOT cover?
- Fiber stubs where the ferrule's refractive index is less than or equal to the cladding's refractive index.
- Optical fiber connections that do not use a ferrule with this specific refractive index relationship.
- Methods for reducing signal loss caused by factors other than cladding modes.
- Fiber stubs designed for multi-mode optical fibers where the primary signal travels within the cladding.
- Devices where the fiber stub is longer than about five millimeters (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 4).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The cleverness lies in using the ferrule itself, which typically just holds the fiber, as an active optical element. By making the ferrule's material optically denser (higher refractive index) than the fiber's cladding, it forces unwanted light out of the cladding and into the ferrule, where it can be absorbed.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Optical transceivers for data centers
Fiber optic modules in telecommunications equipment
10GBASE-LRM modules
Components in high-speed optical networks
Why it matters
The bigger picture
In high-speed fiber optic communication, even small amounts of stray light can degrade signal quality, leading to errors and reduced transmission distances. This patent addresses a common problem called "cladding modes," which are unwanted light signals traveling outside the main fiber core. By effectively stripping these modes, the technology helps ensure clearer, more reliable data transmission, which is vital for internet infrastructure and data centers.
Filed
January 31, 2006
Granted
September 11, 2007
Market context
Who's building on this
Companies in this space
Finisar, the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, is now part of Coherent, a major player in optical components and subsystems. Other companies like Lumentum, Broadcom, and Sumitomo Electric also develop and manufacture optical transceivers and components that benefit from such signal integrity techniques, ensuring high-quality data transmission in their products.
Market impact
This patent contributed to the ongoing effort to improve the reliability and performance of high-speed optical transceivers. By providing a method to reduce cladding mode interference, it enabled more robust data transmission over longer distances, which is crucial for the expansion of data centers and telecommunications networks. It helped ensure that optical components could meet the stringent signal quality requirements of standards like 10GBASE-LRM.
Claim 1 — Plain English
What this patent covers
The patent describes a "fiber stub" (Claim 1) used in optical devices like transceivers (Claim 18). This stub has an "optical fiber" with a "core" (where the main light signal travels) and a "cladding" (the layer surrounding the core). Crucially, the stub also includes a "ferrule" (a protective sleeve) made of a material, often glass (Claim 2), that has a "refractive index" greater than the cladding's refractive index (Claim 1). This difference causes unwanted "cladding modes" (light traveling in the cladding) to bend and refract into the ferrule and away from the core (Abstract). An optional "absorbing layer" on the ferrule's outer surface can then soak up this unwanted light (Claim 5), ensuring a cleaner signal is transmitted. For example, in a 10 Gigabit Ethernet transceiver (Claim 20), this stub helps maintain signal integrity over distances up to 300 meters.
The clever bit
The cleverness lies in using the ferrule itself, which typically just holds the fiber, as an active optical element. By making the ferrule's material optically denser (higher refractive index) than the fiber's cladding, it forces unwanted light out of the cladding and into the ferrule, where it can be absorbed.
What it does not cover
- Fiber stubs where the ferrule's refractive index is less than or equal to the cladding's refractive index.
- Optical fiber connections that do not use a ferrule with this specific refractive index relationship.
- Methods for reducing signal loss caused by factors other than cladding modes.
- Fiber stubs designed for multi-mode optical fibers where the primary signal travels within the cladding.
- Devices where the fiber stub is longer than about five millimeters (Claim 4).
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Strong
Citation count
38/40
Highly cited
Claim breadth
17/20
Very broad protection
Recency
5/20
Granted 10–20 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$44K – $140K
Midpoint $88K · expired or expiring · industry ×1.5
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
0 independent claims · 1 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
26 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Vandyshev, Y., Aronson, L. B., & Deng, H. (2007). How a Special Fiber Stub Cleans Up Light Signals (U.S. Patent No. 7,267,494). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/7267494/fiber-stub-for-cladding-mode-coupling-reduction
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How a Special Fiber Stub Cleans Up Light Signals cover?
This patent describes a short piece of optical fiber, called a fiber stub, designed to prevent unwanted light from escaping the fiber's core and interfering with data transmission by using a ferrule with a specific optical property.
Who owns patent US 7267494?
Finisar owns this patent, granted in 2007.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 7267494 cited by?
This patent has been cited by 81 later patents that build on its ideas.
What problem does this patent solve?
In high-speed fiber optic communication, even small amounts of stray light can degrade signal quality, leading to errors and reduced transmission distances. This patent addresses a common problem called "cladding modes," which are unwanted light signals traveling outside the main fiber core. By effectively stripping these modes, the technology helps ensure clearer, more reliable data transmission, which is vital for internet infrastructure and data centers.
What does this patent NOT cover?
Fiber stubs where the ferrule's refractive index is less than or equal to the cladding's refractive index.
Patent monitoring