Dynamic FEC Bit Adjustment for WDM OSNR Degradation
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Solution Overview
Problem
Wavelength division multiplexed (WDM) communication systems, compliant with ITU-T G.709 standards, face performance degradation over time due to component degradation, leading to errors or loss of communication, as existing systems do not effectively adapt to changes in optical signal-to-noise ratio (OSNR).
Innovation Solution
The system dynamically adjusts the number of forward error correction (FEC) bits in frames transmitted over optical channels, increasing the coding gain by reducing data payload bits and adding more FEC bits in response to decreasing OSNR, maintaining compliance with G.709 frame length and rate requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of FEC bits is increased to improve coding gain, then the coding gain improves, but the payload data rate decreases
Solution Approach 1:
The system dynamically adjusts the number of FEC bits in each frame based on real-time OSNR measurements. When OSNR deteriorates, the system increases FEC bits to maintain coding gain; when OSNR is good, the system reduces FEC bits to maximize payload data rate. This dynamic adaptation resolves the contradiction between reliability and productivity by making the frame structure flexible rather than fixed.
Solution Approach 2:
The invention changes the parameter of FEC bit count based on OSNR conditions. By varying the number of FEC bits from 0 to maximum (e.g., 36 bits for OTU2) depending on the measured OSNR, the system optimizes the trade-off between coding gain and payload data rate, allowing the same physical infrastructure to adapt to different signal quality conditions.
2Reliability
If the overhead ratio is increased to improve error correction capability, then the error correction capability improves, but the effective payload capacity decreases
Solution Approach 1:
The system dynamically adjusts the overhead ratio by varying the number of FEC bits based on real-time OSNR measurements. When signal quality deteriorates, the overhead ratio increases to provide better error correction; when signal quality is good, the overhead ratio is minimized to maximize payload capacity. This dynamic approach allows the system to adapt the overhead ratio to actual channel conditions rather than using a fixed high overhead ratio.
3Reliability
If the baud rate is reduced to improve signal quality, then the signal quality improves, but the transmission speed decreases
Solution Approach 1:
The system dynamically adjusts the baud rate based on OSNR conditions to optimize the trade-off between signal quality and transmission speed. When OSNR deteriorates, the system reduces the baud rate to improve signal quality and reduce errors; when OSNR is good, the system maintains high baud rates to maximize transmission speed. This dynamic adaptation allows the system to respond to changing channel conditions in real-time.
Data Source
AI summary
Consistent with the present disclosure, based on system requirements or in response to an increase in optical signal-to-noise level of an optical channel, such as a WDM channel, additional FEC bits are inserted into and replace selected data payload bits in each frame carried by the channel. The replaced data payload bits may then be transmitted in subsequent frames on the same channel. As a result, the transmitted frames have a reduced data payload rate, but a higher coding gain. Alternatively, the replaced data payload bits may be included in frames transmitted on another optical channel. In that case, the frames carried by the two channels typically have the same bit length or number of bits and may thus be compliant with the frame length requirements of G.709, for example. Preferably, the number of coding bits may be changed dynamically to obtain different coding gains.