Optical Channel Spectrum Dithering for Frequency Offset Control
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Solution Overview
Problem
Relative frequency offsets between optical filter transmittance and optical channel spectra in optical networks lead to reduced baud rates and compromised throughput performance, due to factors like temperature changes and manufacturing defects.
Innovation Solution
The method involves transmitting a dithered optical channel signal with alternating frequency detunings, and based on measured bit error rates, adjusting the optical channel spectrum or filter transmittance to reduce relative frequency offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If narrower guard bands are used between optical channel signals, then higher baud rates can be achieved, but relative frequency offsets between optical filter transmittance and optical channel spectrum reduce the baud rate
Solution Approach 1:
The patent implements a feedback mechanism where the receiver measures bit error rate (BER) and sends control signals back to the transmitter to adjust the optical channel spectrum frequency. The transmitter alternates between two frequency offsets (positive and negative) and receives feedback indicating which offset provides lower BER, allowing dynamic adjustment to maintain optimal alignment despite temperature changes and manufacturing variations.
Solution Approach 2:
The system dynamically adjusts the optical channel spectrum frequency based on measured performance. Instead of using a fixed frequency, the transmitter alternates between two frequency offsets and selects the one that provides better alignment with the optical filter transmittance, as determined by BER measurements. This dynamic adaptation allows the system to compensate for environmental changes and maintain high baud rates.
2Productivity
If higher baud rates are achieved with narrower guard bands, then throughput performance improves, but optical network elements are susceptible to temperature changes and manufacturing defects causing frequency offsets
Solution Approach 1:
The system performs preliminary testing by transmitting signals with both positive and negative frequency offsets before settling on the optimal offset. The transmitter alternates between the two offsets and allows the receiver to measure BER for each, preparing the system to select the best offset before normal operation begins, thus preemptively compensating for environmental factors.
Solution Approach 2:
The patent changes the frequency parameter of the optical channel signal by introducing two different frequency offsets (positive and negative) relative to the nominal frequency. By alternating between these parameter variations and selecting the one that provides better alignment with the optical filter, the system compensates for temperature changes and manufacturing defects without sacrificing throughput performance.
3Speed
If the optical channel spectrum is adjusted to reduce frequency offset, then baud rate improves, but additional control mechanisms are required
Solution Approach 1:
The system is self-adjusting through an automated feedback loop. The receiver autonomously measures BER, determines which frequency offset performs better, and sends control signals back to the transmitter to adjust the spectrum. This self-service mechanism eliminates the need for manual calibration and reduces the complexity of external control systems while maintaining high baud rates.
Data Source
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AI summary
The disclosed systems, apparatuses and methods are directed to controlling optical channel signal and an optical network equipment in optical networks. The methods comprise adjusting an optical channel spectrum based on bit error rates (BER) measured for a dithered optical channel signal. The optical channel spectrum is dithered such that a signal reference frequency is alternated between a first second signal reference frequency and a second signal reference frequency. BER is measured and analysed separately for the dithered signal reference frequency being detuned to the first and to the second signal reference frequencies. Based on a BER difference between BER at the first signal reference frequency and BER at the second signal reference frequency, the optical channel spectrum is shifted with regards to frequency in order to improve optical network performance.