Self-coherent receiver using single delay interferometer
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Solution Overview
Problem
Conventional DQPSK demodulation in optical communication systems requires two delay interferometers, leading to increased size, cost, and complexity due to the need for polarization calibration and multiple balanced detectors, which complicates signal processing and is affected by random polarization changes in fiber channels.
Innovation Solution
A self-coherent receiver based on a single delay interferometer, utilizing a double path bidirectional multiplexing delay interferometer, beam splitters, circulators, and balanced detectors, which splits and processes optical signals to achieve polarization-independent delayed self-interference without active polarization calibration, reducing the number of required detectors and simplifying signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two delay interferometers are used for conventional DQPSK demodulation, then demodulation of I and Q components is achieved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of two separate delay interferometers into a single delay interferometer by utilizing polarization beam splitting. The first polarization beam splitter divides the input signal into two polarization states, each passing through the single delay interferometer to perform both I and Q component demodulation simultaneously, thereby reducing device complexity while maintaining demodulation capability
Solution Approach 2:
The single delay interferometer is designed to perform multiple functions: it demodulates both I and Q components through polarization-independent delayed self-interference, and the system incorporates polarization beam splitting to handle different polarization states. This multi-functional design eliminates the need for separate delay interferometers for each component
2Measurement precision
If polarization calibration is performed to handle random polarization changes, then demodulation accuracy is maintained, but real-time calibration complexity and system cost increase
Solution Approach 1:
The system performs polarization-independent delayed self-interference where the optical signal interferes with its own delayed version. This self-interference mechanism automatically compensates for polarization changes without requiring external polarization calibration equipment or real-time adjustment, as the interference pattern inherently accounts for the actual polarization state of the signal
Solution Approach 2:
The patent utilizes polarization beam splitting to change the polarization state parameters of the signal. By splitting the input signal into different polarization states and processing them through the single delay interferometer, the system transforms the problem of polarization sensitivity into a manageable parameter separation, eliminating the need for complex calibration systems
3Adaptability or versatility
If four balanced detectors are used for polarization-independent demodulation, then polarization independence is achieved, but electrical signal processing difficulty and cost increase
Solution Approach 1:
The patent combines the detection functions into two balanced detectors by utilizing the polarization beam splitting architecture. The first polarization beam splitter directs different polarization states to appropriate detectors, and the single delay interferometer processes both components, reducing the detector count from four to two while maintaining polarization-independent demodulation capability
Solution Approach 2:
Each balanced detector in the patent performs multiple functions: detecting both I and Q component signals through the polarization beam splitting and single delay interferometer processing. This multi-functional detection approach eliminates the need for separate detectors for each component and polarization state, reducing overall system complexity
Data Source
AI summary
Disclosed is a self-coherent receiver based on single delay interferometer, comprising a first beam splitter, a first circulator, a second circulator, a double path bidirectional multiplexing delay interferometer, a first balanced detector, a second balanced detector and an electrical signal processing module.