Invalidity dossier
US 6959149
Added 9/24/2026, 2:19:38 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 6,959,149 B2
Title: Power balancing in DWDM optical networks
Assignee / Inventors: Original assignee Nortel Networks Ltd.; current assignee listed as Ciena Luxembourg SARL / Ciena Corp. Inventors: Nigel L. Bragg, Bram Peeters, Alan Robinson.
Key dates: Priority/filing date 2002-03-29; published as US20040208535A1 (2004-10-21); granted 2005-10-25; status "Expired – Lifetime," adjusted expiration 2024-01-20.
Purpose: In amplified DWDM networks, channels accumulate gain tilt and ripple along amplifier chains, and each amplifier adds amplified spontaneous emissions (ASE) noise, degrading OSNR. Because ring deployments route different wavelengths over different distances while long-haul routes carry a full aggregate, gain/loss variations arise both systematically (accumulated gain ripple) and randomly (e.g., demux/mux filter loss variation). The invention balances per-channel power to achieve a desired OSNR at the receiver.
Plain-language scope: Power is measured at an optical transmitter (referenced to the nominal power level in the multiplex immediately following it) and at a receiver (referenced to the nominal level in the multiplex immediately preceding it). The mean of these two referenced levels is computed, and a first-order closed mean power control loop between transmitter and receiver adjusts that mean so a desired receive OSNR is met. The approach uses a metric (mean power) guaranteed drivable to target on all wavelengths, a simple first-order loop in log space, and time-constant selection to prevent instability from inter-channel coupling. The scheme also addresses interaction between end-to-end wavelength loops and local amplifier aggregate loops, and requires reliable messaging between multiplex end-points, known wavelength counts via OAM, and per-wavelength source control and measurement; no per-wavelength measurement is required at intermediate network elements. Claims recite the method, corresponding apparatus, an optical communications system, and a computer-readable storage medium.
What the excerpt does not establish: It omits the full claim text and detailed control-loop description (truncated at "The mean power con…"), the complete figures/embodiments, and any litigation, validity, prior-art, or ownership analyses. The cited legal status is an assumption per the source.
Generated 10/1/2026, 9:30:52 PM
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Assignment history
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Prior art
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