Optical Receiver Phase Data Recovery Without Local Oscillator
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Solution Overview
Problem
Conventional optical data receivers, such as Stokes vector and Kramers-Kronig receivers, are complex and costly, especially when supporting polarization diversity, and often require local optical oscillators to avoid frequency fading, whereas direct detection methods are simpler and more cost-effective but lack efficient solutions for phase-modulated signals with polarization and spatial multiplexing.
Innovation Solution
An optical data receiver design utilizing an optical power splitter and multiple optical intensity detectors with different frequency dependencies, coupled with a digital signal processor, which recovers phase-modulated data without a local oscillator, supporting polarization and spatial multiplexing by applying distinct channel functions to separate signal portions, enabling direct detection and demodulation of phase information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Stokes vector or Kramers-Kronig optical data receivers are used to recover phase-modulated data, then data recovery capability is achieved, but device complexity increases and cost increases
Solution Approach 1:
The patent extracts and eliminates the local optical oscillator from the receiver structure, using only direct detection of the incoming optical signal. By removing this complex component while using multiple optical paths with different dispersion characteristics, the system achieves phase-modulated data recovery without the complexity of conventional coherent receivers
Solution Approach 2:
The incoming optical signal is divided into multiple copies that travel through different optical paths with distinct dispersion characteristics. Each path provides different frequency dependencies, and the combined information from all paths enables phase recovery without requiring complex interferometric measurements
2Reliability
If local optical oscillators are added to avoid frequency fading, then frequency stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent completely removes the local optical oscillator from the system, demonstrating that frequency stability can be achieved through direct detection combined with multiple optical paths having different dispersion characteristics, eliminating the need for complex oscillator-based frequency reference systems
Solution Approach 2:
Instead of using a local oscillator to reference the signal frequency, the system creates multiple copies of the incoming signal that propagate through different dispersion-regime optical paths. These copies retain the original signal's frequency information while experiencing different phase evolution, enabling frequency stability without oscillators
3Device complexity
If direct detection methods are used for phase-modulated signals with polarization and spatial multiplexing, then device simplicity is maintained, but efficient data recovery capability is lost
Solution Approach 1:
The patent extends direct detection from single-dimensional intensity measurement to multi-dimensional detection by utilizing multiple optical paths with different dispersion characteristics. This dimensional expansion in the optical domain enables phase information extraction while maintaining direct detection simplicity
Solution Approach 2:
The system changes the dispersion parameter of different optical paths to create distinct frequency dependencies. By controlling and varying the dispersion characteristics of each path, the patent enables phase-modulated data recovery through direct detection while maintaining device simplicity
Data Source
AI summary
An apparatus includes an optical data receiver to receive a phase-modulated optical signal and to demodulate data therefrom. The optical data receiver includes an optical power splitter, first and second optical intensity detectors, and a digital signal processor. The digital signal processor is connected to receive digital values of intensity measurements of each of the optical intensity detectors. The first optical intensity detector is connected to receive light from the optical power splitter via a first optical path, and the second optical intensity detector is connected to receive light from the optical power splitter via a second optical path. The first and second optical paths have channel functions with different frequency dependencies.