Tunable Optical Transmitter Wavelength Calibration
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Solution Overview
Problem
In optical wavelength division multiplex (WDM) systems, it is challenging to switch on tunable optical transmitters without interfering with other channel signals, especially when low-cost transmitters with uncertain wavelength accuracy are used, leading to potential interference with existing optical channel signals.
Innovation Solution
A method for tuning a tunable optical transmitter to a predetermined target wavelength during the power-on procedure, using a secure wavelength range and calibration information to ensure the transmitter operates within a non-interfering range, allowing for the use of low-cost transmitters without pre-calibration, by controlling the optical center wavelength through temperature and mechanical adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-cost tunable optical transmitters without pre-calibration are used, then device cost is reduced, but wavelength accuracy deteriorates causing interference with other channel signals
Solution Approach 1:
The patent applies preliminary action by performing a calibration procedure during the power-on sequence before the transmitter begins normal operation. The control unit determines calibration information by measuring the actual wavelength and comparing it to the target wavelength, then stores this calibration data for use during operation. This preliminary calibration eliminates the need for expensive pre-calibrated transmitters while ensuring accurate wavelength control.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual wavelength output of the transmitter and using this information to adjust the tuning control. The control unit compares the measured wavelength with the target wavelength and modifies the tuning parameters accordingly, creating a closed-loop system that maintains accurate wavelength control even with low-cost transmitters that have uncertain wavelength dependencies.
2Measurement precision
If the transmitter is tuned to the target wavelength during power-on, then channel signal accuracy is improved, but interference with other channel signals may occur during the tuning process
Solution Approach 1:
The patent performs the wavelength calibration and determination of tuning parameters as a preliminary action during the power-on sequence, before the transmitter is switched to normal operational mode. This ensures that the transmitter is properly calibrated to the target wavelength before beginning transmission, preventing interference with other channels during the tuning process.
Solution Approach 2:
The patent executes the calibration procedure rapidly during the power-on sequence, completing the wavelength measurement and adjustment before normal operation begins. This quick calibration approach minimizes the time during which the transmitter might operate at incorrect wavelengths, thereby reducing the risk of interfering with other channel signals.
3Object-affected harmful factors
If a secure wavelength range is used during calibration, then interference with existing channels is prevented, but the tuning range is restricted
Solution Approach 1:
The patent determines the secure wavelength range as a preliminary step during system setup or power-on, before normal transmission begins. This calibration phase uses the restricted secure range to safely measure and adjust the transmitter wavelength without risking interference with operational channels. Once calibrated, the transmitter can operate at the target wavelength within the full available range.
Solution Approach 2:
The patent introduces a secure wavelength range as an intermediary zone during the calibration process. This intermediate wavelength range serves as a safe testing area that is distinct from the operational channel wavelengths, allowing calibration activities to proceed without risking interference with live channels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables cost-efficient and accurate tuning of tunable optical transmitters, preventing interference with other channel signals and allowing their use in complex WDM systems, even with unknown wavelength dependencies, thereby reducing the need for expensive, precisely calibrated transmitters.
Implementation Method 1
controlling the optical center wavelength through temperature and mechanical adjustments
Data Source
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AI summary
The invention relates to a method for tuning a tunable optical transmitter (35) of a given type out of a plurality of optical transmitters that are connected to a first end of an optical WDM transmission link to a predetermined target wavelength, especially during a power-on procedure of the tunable optical transmitter (35), wherein the tunable optical transmitter (35) is controllable to create an optical signal having a predetermined wavelength according to a tuning information which is supplied to the tunable optical transmitter (35) through at least one tuning signal (Stune), wherein the tuning information comprises at least one parameter of the at least one tuning signal (Stune). The method comprises the step of controlling the tunable optical transmitter (35) to create an optical calibration signal (Scal) according to a nominal tuning information in such a way that the optical calibration signal (Scal) has a wavelength lying within a secure wavelength range, the nominal tuning information being determined by using a known nominal wavelength dependency characterizing the wavelength dependency of the given type of tunable optical transmitters on the at least one parameter of the at least one tuning signal (Stune), and the secure wavelength range being defined in such a way that it does not comprise any optical channel wavelength ranges predefined for the WDM transmission link and that it is broad enough to ensure that the wavelength of the optical calibration signal (Scal) lies within the secure wavelength range. The method further comprises the steps determining a calibration information for the optical tunable transmitter by directly or indirectly measuring, within the secure wavelength range, a deviation between an actual wavelength dependency of the tunable optical transmitter (35) and the nominal wavelength dependency, and controlling the tunable optical transmitter (35) to create an optical channel signal according to a target tuning information in such a way that the optical signal has a wavelength being equal or lying, within predetermined acceptable tolerances, close to the target wavelength, wherein the target tuning information is determined by using a corrected nominal wavelength dependency, the correction being effected by using the calibration information. Further, the invention relates to a tuning control device for at least one tunable optical transmitter (35) adapted to be used in an optical WDM system (1, 1'), the tuning control device realizing the respective method, and to an optical WDM system (1,1') comprising such a tuning control device.