Coherent Optical Receiver Phase Synchronization Feedback Loop
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Solution Overview
Problem
Current coherent optical interconnects face challenges in achieving low power consumption for high-speed data transmission due to the need for high-power ADCs and DSPs, especially for carrier phase/frequency recovery and compensation, which results in high bit-error-rates and increased costs.
Innovation Solution
A receiver for coherent optical communication links is designed with a 90° optical hybrid, carrier phase offset detection block, and a tunable phase delay block configured in a feedback loop, using an endless tunable phase delay element and optical IQ modulator to achieve carrier phase synchronization, reducing the need for high-power components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-power ADCs and DSPs are used for carrier phase recovery and compensation in coherent optical links, then carrier phase synchronization can be achieved, but power consumption increases significantly
Solution Approach 1:
The patent replaces the electronic DSP-based carrier phase recovery system with an all-optical phase compensation system using a tunable optical delay line and phase modulator. This substitution eliminates the need for high-power ADCs and DSP processors, achieving carrier phase synchronization through optical domain operations instead of electronic processing.
Solution Approach 2:
The patent introduces an optical phase conjugator as an intermediary device that generates a phase-conjugated copy of the received signal. This intermediary signal is then combined with the original signal in a 3dB coupler to achieve phase compensation, effectively mediating the phase recovery process without requiring high-power electronic components.
2Reliability
If Costas loop is used for CPRC in BPSK signals, then carrier phase recovery can be achieved, but very specific fast-tunable lasers with poor phase-noise characteristics are required, increasing cost and bit-error-rates
Solution Approach 1:
The patent implements a feedback mechanism where the phase error detected from the combined signal is fed back to control the optical delay line and phase modulator. This closed-loop feedback system automatically adjusts the optical phase to compensate for carrier phase offset, eliminating the need for complex fast-tunable lasers with specific phase-noise characteristics required by Costas loop.
3Productivity
If advanced modulation formats (QPSK, 16-QAM, etc.) are used for higher data rates, then data capacity increases, but carrier phase/frequency recovery and compensation becomes more difficult to implement
Solution Approach 1:
The patent creates a universal optical phase compensation system that can handle multiple modulation formats (BPSK, QPSK, 16-QAM, etc.) through the same all-optical mechanism. The tunable optical delay line and phase modulator provide format-agnostic phase compensation, making the system universally applicable to advanced modulation formats without increasing implementation complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables power-efficient carrier phase recovery and compensation, improving bit-error-rates and reducing power consumption while supporting advanced modulation formats like QPSK and 16-QAM, thus enhancing the efficiency of coherent optical interconnects.
Implementation Method 1
a 90° optical hybrid configured to receive as an input, a reference optical carrier (LO) signal and a modulated optical signal (S)
Implementation Method 2
a tunable phase delay block configured to receive the one or more control signals from the electronic control unit... tuning the phase delay of the tunable phase delay block to achieve carrier phase synchronization
Data Source
AI summary
Embodiments herein disclose receiver of coherent optical communication link and method of compensating carrier phase offset in receiver. 90° optical hybrid is configured to receive input of reference optical carrier (LO) signal and modulated optical signal (S) and carrier phase offset detection block is configured to generate output signal representing average of the phase offset at the input of the carrier phase offset detection block. Electronic control unit configured to receive output signals from the carrier phase offset detection block for generating control signals and tunable phase delay block configured to receive the control signals from the electronic control unit. 90° optical hybrid, carrier phase offset detection block, electronic control unit and the tunable phase delay block are configured in feedback loop, such that outputs of the carrier phase offset detection block are used for tuning the phase delay of the tunable phase delay block to achieve carrier phase synchronization.