WDM Optical Transmission With Parallel Interleaving for Fading Resistance
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Solution Overview
Problem
Current digital optical communication links between satellites and earth stations face significant challenges due to atmospheric turbulence, leading to signal fading and errors, which existing error-correcting codes and interleaving methods struggle to address effectively, especially at high data transmission rates.
Innovation Solution
A method that splits a high-rate binary data stream into multiple lower-rate streams, applies individual error-correcting encoding and interleaving, and modulates them onto different optical carriers with unique wavelengths for wavelength-division-multiplexing, enabling robust error correction and resistance to long periods of signal fading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error-correcting codes and time-interleaving are used to correct transmission errors during fading periods, then data integrity is improved, but device complexity and processing difficulty increase significantly at high data transmission rates
Solution Approach 1:
The invention divides the high-rate binary data stream into multiple parallel lower-rate substreams using a serial-to-parallel converter. Each substream is processed independently through separate encoding and interleaving paths, then recombined through a parallel-to-serial converter. This segmentation reduces the processing burden on individual encoding/interleaving units while maintaining overall data integrity during fading periods.
2Reliability
If the duration of time-interleaving is extended to match long fading periods (hundreds of milliseconds), then error correction capability is improved, but memory requirements and processing speed requirements become impossible to meet with current electronics
Solution Approach 1:
By segmenting the high-rate data stream into multiple parallel lower-rate substreams, the invention enables each substream to be interleaved over shorter time intervals that are feasible with current electronics. The parallel structure accumulates the interleaving effect across multiple substreams, achieving effective fading resistance without requiring impractical memory sizes or processing speeds for any single channel.
Solution Approach 2:
The invention transitions from a single-dimensional time-interleaving approach to a multi-dimensional structure by introducing parallel processing channels. Instead of interleaving one long sequence over hundreds of milliseconds, multiple shorter sequences are interleaved in parallel, effectively adding a spatial dimension (number of channels) to compensate for the reduced time dimension in each individual channel.
3Productivity
If conventional single carrier modulation is used, then device complexity is kept low, but the system cannot achieve high data transmission rates (tens to hundreds of Gbps) with sufficient error correction capability
Solution Approach 1:
The invention segments the high-rate data stream into multiple parallel substreams that can each be modulated onto separate optical carriers or processed through separate channels. This allows the system to achieve high aggregate data rates (tens to hundreds of Gbps) by summing the capacities of multiple lower-rate channels, while each individual channel maintains manageable complexity for encoding and interleaving.
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 allows for reliable high-rate data transmission (several Gbps to hundreds of Gbps) with reduced processing demands and power consumption, effectively correcting errors caused by scintillation and wavefront distortions, even during prolonged fading periods.
Implementation Method 1
in a fourth step, in modulating each of the p interleaved and encoded bit streams by means of p optical carriers with different wavelengths in order to obtain p different optical signals
Implementation Method 2
in a fifth step, in wavelength-division-multiplexing the p optical signals in order to obtain a multiplexed optical signal suitable for being transmitted
Data Source
AI summary
A transmitter of a binary data stream comprises: a serial/parallel converter to split the binary data stream into m different parallel bit streams, each bit stream having a rate D/m which is m times lower than the initial rate D; m first encoding modules to error-correcting encode each bit stream individually; a time-interleaver to intermix the information bits originating from different encoded bit streams; an encoder to error-correcting encode the m interleaved bit streams into p bit streams; p electro-optical modulators to modulate each of the p bit streams delivered by the interleaver by means of p optical carriers of different wavelengths; and a wavelength-division multiplexer to combine the less p optical carriers into a single optical signal.