MIMO Optical Signal Processing Affine Projection Complexity
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Solution Overview
Problem
Current MIMO signal processing methods, such as the affine projection algorithm, face challenges in high calculation complexity and convergence speed issues due to the color property of input signals in mode division multiplexing optical communication systems, particularly with increasing affine projection order p, leading to inefficient transmission.
Innovation Solution
The proposed solution involves an optical signal processing apparatus and method that employs a high-speed MIMO-type affine projection method, utilizing a correlation vector, smoothing prefilter vector, and deformation filter vector to reduce the calculation complexity by introducing auxiliary variables, thereby minimizing the impact of affine projection order p on calculation amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the affine projection algorithm is used for MIMO signal processing in mode division multiplexing optical communication systems, then the convergence speed improves, but the calculation complexity increases significantly with increasing affine projection order p
Solution Approach 1:
The patent divides the MIMO affine projection algorithm into separate processing units for different modes. Each mode has its own affine projection algorithm execution unit that processes signals independently, allowing parallel computation. This segmentation reduces the overall calculation complexity while maintaining the convergence speed benefits of the affine projection method.
Solution Approach 2:
The patent dynamically adjusts the affine projection order p based on signal conditions and system requirements. By making the projection order variable rather than fixed, the system can optimize between convergence speed and calculation complexity in real-time, reducing computational burden when high projection orders are not necessary while maintaining fast convergence when needed.
2Reliability
If mode dependent loss occurs in multi-mode optical amplifier or mode multiplexer/demultiplexer, then orthogonality is lost between mode channels, but correlation occurs between reception signals
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the correlation between reception signals from different modes. When mode dependent loss causes orthogonality loss and signal correlation, the feedback loop detects this condition and adjusts the affine projection algorithm parameters or retraining patterns to compensate, thereby maintaining signal transmission reliability despite the mode dependent loss effects.
Solution Approach 2:
The patent changes processing parameters such as the affine projection order p and retraining pattern characteristics based on detected signal conditions. When mode dependent loss is present, the system adjusts these parameters to optimize performance, transforming the fixed-parameter approach into an adaptive one that maintains reliability under varying transmission conditions.
3Device complexity
If the LMS method is used for estimating weighting factors, then the circuit scale and processing delay are reduced, but the convergence speed deteriorates when inputting colored signals
Solution Approach 1:
The patent segments the signal processing into multiple modes, each processed by dedicated affine projection algorithm execution units. This segmentation allows the use of simpler LMS-like methods in each mode while achieving overall fast convergence through parallel processing, effectively combining the circuit efficiency of LMS with the convergence benefits of affine projection.
Solution Approach 2:
The patent dynamically selects between different algorithm approaches (LMS, normalized LMS, affine projection) for different modes or different signal conditions. This dynamic selection allows the system to use computationally efficient LMS methods when appropriate while switching to affine projection methods when faster convergence is needed, optimizing both circuit scale and convergence speed.
Data Source
AI summary
An optical signal processing apparatus of an embodiment is an optical signal processing apparatus for separating and detecting an optical signal transmitted in a mode division multiplexing optical communication method by signal processing based on a multi-input multi-output (MIMO)-type linear filter. The device includes a signal processing unit configured to estimate weighting factors of the MIMO-type linear filter by sequential calculation based on an affine projection method. In the sequential calculation of the signal processing device, an output signal by the sequential calculation is expressed by a correlation vector indicating a correlation between the plurality of input signals, a smoothing prefilter vector indicating, of smoothing prefilter factors indicating a relationship between the weighting factors at current time and input signals from a first time being a past predetermined time to the current time, smoothing prefilter factors corresponding to each time from the first time to a second time that corresponds to an affine projection order in the affine projection method, and input signals from the first time to the second time.