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Updated: May 18, 2026

Quasi-light Storage for Optical Data Packets
Published on: February 6, 2014
45 Gb/s low complexity optical front-end for soft-decision LDPC decoders.
Meer Nazmus Sakib1, Monireh Moayedi, Warren J Gross
1Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7, Canada. meer.sakib@mail.mcgill.ca
This study presents a low-complexity, energy-efficient optical front-end for soft-decision low-density parity-check (LDPC) decoders, achieving significant coding gains. The system also functions as a 2-bit analog-to-digital converter (ADC), offering substantial optical power savings.
Area of Science:
- Optical communications engineering
- Digital signal processing
- Error correction coding
Background:
- Soft-decision decoding offers superior performance over hard-decision decoding in optical communication systems.
- Low-density parity-check (LDPC) codes are advanced error correction codes crucial for high-speed data transmission.
- Efficient front-end processing is essential for managing the complexity and power consumption of modern optical networks.
Purpose of the Study:
- To demonstrate a low-complexity and energy-efficient 45 Gb/s soft-decision optical front-end compatible with soft-decision LDPC decoders.
- To evaluate the coding gain and performance improvements compared to hard-decision front-ends.
- To explore the dual functionality of the soft-decision circuit as a 2-bit flash analog-to-digital converter (ADC) for equalization schemes.
Main Methods:
- Implementation of a 45 Gb/s soft-decision optical front-end.
- Testing with long block length LDPC(32768,26803) codes to determine net coding gain.
- Performance comparison against a hard-decision front-end.
- Integration and testing of the soft-decision circuit as a 2-bit flash ADC with equalization schemes at various bit rates (15 Gb/s) and code types (RS, LDPC).
Main Results:
- A net coding gain of 7.06 dB and 9.62 dB was achieved for LDPC(32768,26803) at BER of 10(-7) and 10(-12), respectively.
- A 1.9 dB performance advantage over hard-decision front-ends was observed for the tested LDPC code.
- Optical power savings of up to 10.5 dB were realized at 15 Gb/s with various error correction codes and a 6-tap FIR equalizer.
- The 2-bit flash ADC demonstrated low power consumption: 2.71 W at 32 GSamples/s and an estimated 4.95 W at 45 GSamples/s.
Conclusions:
- The developed soft-decision optical front-end is effective in enhancing the performance of LDPC-coded systems.
- The dual-mode capability as an ADC integrated with equalization offers significant optical power savings.
- The design presents a viable solution for energy-efficient, high-performance optical communication systems.
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