Single Photo-Detector Optical Receiver for Dual-Polarization Signal Detection
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Solution Overview
Problem
Existing optical receivers for dual-polarization QPSK/xPSK/xQAM modulation require four photo-detectors and high-speed ADCs, leading to increased complexity and power consumption due to the need for separate detection of in-phase and quadrature signals.
Innovation Solution
The method involves interleaving 0 and 90-degree phase or polarization diversity signals to enable a single photo-detector and ADC to receive both I and Q signals, reducing the number of optical components and leveraging excessive bandwidth/sampling-rate of high-speed ADCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four photo-detectors and high-speed ADCs are used for dual-polarization QPSK/xPSK/xQAM modulation reception, then reliable signal detection is achieved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines the detection of in-phase (I) and quadrature (Q) signals into a single photo-detector by interleaving their spectral components. The I and Q signals are modulated with orthogonal codes (e.g., +1/-1 and +j/-j) and summed at the optical domain, allowing one photo-detector to capture both signal components simultaneously. This merging eliminates the need for separate balanced detector pairs while maintaining full signal integrity through digital separation at the receiver.
Solution Approach 2:
A single photo-detector is designed to perform multiple functions: detecting both I and Q signal components, handling dual-polarization signals, and supporting high-speed ADC conversion. The detector becomes a multi-functional component that processes interleaved spectral components from both signal dimensions, reducing the overall number of required components while maintaining comprehensive signal reception capability.
2Reliability
If four photo-detectors and high-speed ADCs are used for dual-polarization QPSK/xPSK/xQAM modulation reception, then complete signal capture is achieved, but power consumption increases
Solution Approach 1:
The patent merges the power consumption of four photo-detectors and multiple ADCs into a single photo-detector and one high-speed ADC. By combining I and Q signal detection paths and utilizing the excessive bandwidth capability of a single high-speed ADC, the system reduces the number of active power-consuming components while maintaining complete signal capture through spectral interleaving and digital signal processing.
3Speed
If high-speed ADCs with excessive bandwidth capability are used, then higher sampling rates are achieved, but the sampling capability is wasted when optical signal bandwidth is below maximum ADC capability
Solution Approach 1:
The patent merges I and Q signal spectra into a single interleaved spectrum that fully utilizes the ADC's bandwidth capability. By modulating I and Q signals with orthogonal codes and summing them optically, the combined signal occupies the full ADC bandwidth, ensuring that high-speed ADCs operate at their optimal sampling rates without wasted capability.
Solution Approach 2:
The system dynamically adapts the signal bandwidth to match the ADC's sampling capability. Through spectral interleaving and orthogonal coding, the effective signal bandwidth is expanded to utilize the full ADC bandwidth, ensuring that the sampling rate capability is fully exploited regardless of the original optical signal bandwidth.
Data Source
AI summary
A method for reducing optical components at a receiver which include converting an input signal at a receiver to include an interleaving of alternate signal diversity components, the signal diversity components including phase diversity when the converting includes 0 and 90 degree interleaving and the signal diversity components include polarization diversity interleaving when the converting includes interleaved orthogonal polarizations, and combining the signal diversity components for enabling a single photo detection at the receiver to detect the alternative signal diversity components for subsequent analog-to-digital conversion.