Optical Module FEC Layering With Low-State Trellis Coding
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Solution Overview
Problem
Complex FEC encoders and decoders in communication systems achieve better performance but consume more power, posing a challenge in applications where power reduction is crucial.
Innovation Solution
An optical module with a second FEC encoder having a bit-level trellis representation with fewer than 64 states is used to further code a subset of the first FEC encoded data, reducing power consumption while maintaining performance, and a complementary decoding process is implemented in the receiving apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex FEC encoders and decoders are used, then data recovery performance is improved, but power consumption increases
Solution Approach 1:
The patent segments the FEC encoding process into two distinct stages: an outer FEC encoder (first encoder) that provides baseline error correction, and an inner FEC encoder (second encoder) that provides additional protection for critical data portions. This segmentation allows the system to achieve high reliability through layered protection while managing power consumption by using different encoder complexities for different data portions, rather than applying uniform complex encoding to all data.
Solution Approach 2:
The patent applies different encoding qualities to different portions of data. The inner FEC encoder with bit-level trellis representation (≤64 states) is applied selectively to a subset of encoded data bits that require higher protection, while other bits use only the outer FEC encoding. This local quality approach ensures that power-consuming complex encoding is applied only where necessary to maintain performance, rather than uniformly across all data.
2Use of energy by moving object
If low-complexity FEC encoders are used, then power consumption is reduced, but data recovery performance deteriorates
Solution Approach 1:
The patent implements prior cushioning by applying outer FEC encoding first to all data bits, creating a baseline level of error protection before transmission. Then, inner FEC encoding is applied to a subset of these already-protected bits, providing an additional layer of defense. This layered approach ensures that even if the low-complexity outer encoder alone would be insufficient, the cumulative effect of both encoding stages provides adequate performance while keeping overall complexity manageable.
Solution Approach 2:
The patent creates a composite FEC encoding scheme that combines two different encoding approaches: outer FEC encoding (which can be simpler) and inner FEC encoding with bit-level trellis representation (which provides enhanced protection). This composite approach is analogous to using composite materials in engineering, where combining different materials with complementary properties creates a system that achieves performance targets while optimizing other characteristics like weight or cost.
Data Source
AI summary
An optical module processes first FEC (Forward Error Correction) encoded data produced by a first FEC encoder. The optical module has a second FEC encoder for further coding a subset of the first FEC encoded data to produce second FEC encoded data. The optical module also has an optical modulator for modulating, based on a combination of the second FEC encoded data and a remaining portion of the first FEC encoded data that is not further coded, an optical signal for transmission over an optical channel. The second FEC encoder is an encoder for an FEC code that has a bit-level trellis representation with a number of states in any section of the bit-level trellis representation being less than or equal to 64 states. In this manner, the second FEC encoder has relatively low complexity (e.g. relatively low transistor count) that can reduce power consumption for the optical module.