IRZ-PDM Signal Generation Using Electrical DAC Shaping
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Solution Overview
Problem
Conventional methods for generating interleaved return-to-zero (IRZ) polarization-division multiplexed (PDM) signals are hindered by high optical complexity, loss, cost, size, and power usage, as well as the difficulty in integrating components and adaptively changing data rates.
Innovation Solution
The method employs digital-to-analog converters (DACs) sampled at twice the modulation symbol rate to perform RZ shaping for I/Q modulators, eliminating the need for optical pulse carvers and allowing for reconfigurable modulation formats, thereby reducing optical complexity and loss while enabling adaptive data rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods using optical pulse carvers and fixed delay lines are used to generate IRZ-PDM signals, then the signal generation is achieved, but the optical complexity, loss, cost, size, and power usage increase significantly
Solution Approach 1:
The patent replaces the mechanical/optical pulse carver system with an electrical domain solution using DACs and digital signal processing. Instead of using optical components to carve pulses, the invention uses electrical DACs to generate the RZ pulse train directly, eliminating the need for optical pulse carvers and their associated complexity
Solution Approach 2:
The invention extracts and removes the optical pulse carver component from the system. By taking out the pulse carver and implementing RZ shaping in the electrical domain through DACs, the patent eliminates the harmful optical components while preserving the desired IRZ-PDM signal generation function
2Reliability
If optical pulse carvers and fixed delay lines are used, then IRZ-PDM signal generation is achieved, but loss, cost, size, and power usage increase
Solution Approach 1:
The patent substitutes the optical pulse carver with an electrical DAC-based system, moving the pulse shaping function from the optical domain to the electrical domain. This substitution eliminates optical insertion losses and reduces power consumption associated with optical components
3Manufacturing precision
If fixed delay lines are used to create half symbol period delay, then the required delay is achieved, but adaptability to change data rates is lost
Solution Approach 1:
The patent implements a dynamic delay mechanism using digital signal processing and buffering in the electrical domain. Instead of a fixed physical delay line, the system uses configurable digital buffers that can be adjusted to provide the required half symbol period delay at different data rates, enabling adaptability while maintaining precision
Solution Approach 2:
The invention changes the delay parameter dynamically based on the data rate. By using digital buffering and processing, the system can adjust the delay value to match different symbol rates, allowing the same hardware to adapt to various data rates while maintaining the required half symbol period delay precision
4Reliability
If conventional IRZ-PDM generation methods are used, then signal generation is achieved, but reconfigurable modulation formats are difficult to implement
Solution Approach 1:
The patent creates a universal signal generation platform using DACs and digital processing that can support multiple modulation formats. The electrical domain implementation allows the same hardware to be reconfigured for different modulation schemes (QPSK, QAM, etc.) by changing the digital input sequences, providing multi-functionality and reconfigurability
Data Source
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AI summary
Return To Zero (RZ) shaping is performed for a first I/Q modulator whose output corresponds to a first polarization component using a first two digital-to-analog converters (DACs), each of which is sampled at approximately twice a modulation symbol rate or more and has an output with a first interleaving order that interleaves one of a first pair of intended drive signal patterns and zeros. RZ shaping is also performed for a second I/Q modulator whose output corresponds to a second polarization component using a second two DACs, each sampled at approximately twice the modulation symbol rate or more and having a second interleaving order that interleaves zeros and one of a second pair of intended drive signal patterns, the second interleaving order opposite the first interleaving order. The first polarization and the second polarization may be combined, thereby forming an Interleaved Return To Zero (IRZ) Polarization Division Multiplexed (PDM) signal.