mPQ Optical Signal Processing via Nyquist Filtering
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Solution Overview
Problem
Current optical communication systems using mPQ modulation formats face significant spectral efficiency loss while attempting to improve power efficiency, limiting transmission capacity due to increased bandwidth requirements.
Innovation Solution
The method involves performing serial-to-parallel conversion of data signals, followed by combined encoding using M-ary Pulse Position Modulation (MPPM) and Quadrature Phase-Shift Keying (QPSK), and shaping the signals with Nyquist-filtering before digital-to-analog conversion and mapping onto an optical carrier, rather than direct digital-to-analog conversion, to reduce bandwidth and enhance spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If mPQ modulation format is used to improve power efficiency, then power efficiency is improved, but spectral efficiency is significantly decreased
Solution Approach 1:
The data stream is segmented into multiple parallel sub-streams (I path, Q path, and PPM path) through serial-to-parallel conversion. Each sub-stream is independently modulated using different modulation schemes (QPSK for I and Q paths, mPPM for PPM path), allowing the system to achieve both high power efficiency through PPM modulation and maintain spectral efficiency by parallelizing the data transmission across multiple paths simultaneously.
2Productivity
If high order modulation format is used to increase transmission capacity, then transmission capacity is increased, but bandwidth occupation is increased
Solution Approach 1:
The system transitions from single-dimensional modulation to multi-dimensional modulation by utilizing both amplitude/phase dimensions (through QPSK on I-Q paths) and time-position dimension (through mPPM on PPM path). This multi-dimensional approach increases transmission capacity without linearly increasing bandwidth occupation, as the PPM path encodes information in time slots rather than frequency bandwidth.
3Duration of action of moving object
If mPQ modulation is used to improve transmission distance, then power efficiency is improved, but transmission rate is decreased
Solution Approach 1:
The system merges two modulation approaches: mPPM modulation (which provides high power efficiency and extended transmission distance) and QPSK modulation (which maintains high transmission rate through efficient phase encoding). By combining these in parallel paths, the system achieves both extended transmission distance through the PPM path and maintained transmission rate through the QPSK paths, resolving the contradiction between distance and speed.
Data Source
AI summary
The embodiments of the present application disclose a method and device for sending and receiving an optical signal. The method for sending an optical signal comprises: performing serial-to-parallel conversion on a data signal to be transmitted to obtain an I path data sequence, a Q path data sequence and a PPM path data sequence which are in parallel; performing mPQ-encoding on the I path data sequence, the Q path data sequence and the PPM path data sequence to obtain an I path and a Q path of an mPQ-encoded digital signal; shaping the I path and the Q path of the mPQ-encoded digital signal by Nyquist-filtering to obtain an I path and Q path of a filtered digital signal; performing digital-to-analog conversion on the I path and the Q path of the filtered digital signal and mapping the converted I path and Q path onto an optical carrier to obtain a target optical signal and send the same. By applying the embodiments of the present application, spectral efficiency loss in optical communication can be reduced or even eliminated while power efficiency is increased.