Optical Communication System Using Advanced Coding and High Modulation Order
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Solution Overview
Problem
Current optical communication systems face challenges in achieving high-speed, error-free transmission over long distances, particularly beyond 1000 km, due to limitations in system sensitivity caused by fiber nonlinearity and phase noise, which are exacerbated by the use of existing fiber amplifiers and modulation formats like QPSK.
Innovation Solution
The implementation of advanced coding schemes, such as low-density parity-check (LDPC) or Turbo coding, combined with high-order modulation techniques, is used to enhance system sensitivity and achieve high-speed transmission. This involves generating optical tones, performing advanced coding and high-order modulation on data signals, and using up-converters and down-converters to transmit and receive optical signals effectively over long distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If advanced coding schemes (LDPC or Turbo coding) combined with high-order modulation are used, then system sensitivity is improved and transmission distance is extended, but device complexity and computation complexity increase
Solution Approach 1:
The patent changes the modulation order parameter from conventional low-order (QPSK, 16-QAM) to high-order modulation (64-QAM, 256-QAM, or higher), thereby increasing the data rate per symbol and improving system sensitivity without requiring additional amplifiers or extending bandwidth. This parameter change enables achieving 1000-km transmission over standard single-mode fiber while managing device complexity through efficient coding schemes.
2Productivity
If high-order modulation is used to increase data rate per channel, then spectrum efficiency is improved, but the system becomes more sensitive to phase noise and fiber nonlinearity
Solution Approach 1:
The patent applies forward error correction coding (LDPC or Turbo coding) as a preliminary action before high-order modulation. This pre-coding creates a more robust signal that can tolerate the increased phase noise and nonlinearity effects inherent in high-order modulation schemes, thereby enabling 1000-km transmission while maintaining data integrity.
3Device complexity
If conventional QPSK modulation is used, then device complexity is kept low and compatibility with existing fiber plants is maintained, but transmission distance is limited and system sensitivity is insufficient for beyond 1000 km
Solution Approach 1:
The patent changes the modulation format from conventional QPSK to high-order modulation (64-QAM, 256-QAM, or higher), thereby increasing the information capacity per symbol and extending the transmission distance capability to beyond 1000 km on existing fiber infrastructure without requiring new amplifier technologies or ultra-large-area fibers.
Data Source
AI summary
A transmitting device, a receiving device, an optical communication system, and associated methods are provided. The transmitting device transmits an optical signal containing data, and comprises: an optical tone generator for generating at least one optical tone; at least one encoder for performing advanced coding on at least one data signal respectively, each of the at least one data signal carrying a part of the data; at least one mapper for performing high order modulation on the at least one coded data signal; and an up-converter for up-converting the at least one high-order-modulated data signal into the optical signal to be outputted through the at least optical tone. Thereby, high speed (e.g., over 1-Tb/s) transmission per single channel over a long-haul distance (e.g. over 1000-km) with error-free recovery may be achieved.