Optical IQ Modulator Phase Shift Control for Crosstalk Suppression
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Solution Overview
Problem
Coherent PON systems face challenges with high residual carrier power in the transmitter off-state and limited power budget due to intrinsic losses in IQ modulators, which affect signal integrity and reduce the number of connectable ONUs.
Innovation Solution
Implementing an optical IQ modulator with a controller that adjusts the phase shift between in-phase and quadrature branches to operate in nonorthogonal modes, including high-suppression and high-power modes, to manage power levels and suppress crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional orthogonal mode operation is used in IQ modulator, then signal integrity is maintained, but residual carrier power is high causing crosstalk interference
Solution Approach 1:
The patent changes the phase shift parameter from the conventional orthogonal value (90 degrees) to nonorthogonal values, creating high-suppression mode for reducing residual carrier power and crosstalk, while maintaining signal integrity through controlled parameter adjustment between different operational modes
2Use of energy by moving object
If IQ modulator operates in conventional mode, then device complexity is low, but power budget is limited due to intrinsic losses
Solution Approach 1:
The patent implements dynamic operation of the IQ modulator by enabling switching between conventional orthogonal mode and nonorthogonal modes based on operational requirements, optimizing power budget while managing device complexity through adaptive mode selection rather than fixed configuration
3Quantity of substance
If more ONUs are connected to the PON, then network coverage is improved, but accumulated off-state noise increases reducing system performance
Solution Approach 1:
The patent converts the harmful off-state carrier power into a beneficial suppressed state by using nonorthogonal modulation modes that actively reduce residual carrier power, transforming the source of crosstalk interference into a mechanism for noise reduction and enabling support for more ONUs
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
The nonorthogonal modes significantly reduce crosstalk and increase optical power, allowing for a higher number of ONUs to be connected and improving the power budget without additional components or amplifiers.
Implementation Method 1
an optical IQ modulator with a controller that adjusts the phase shift between in-phase and quadrature branches to operate in nonorthogonal modes
Implementation Method 2
optical IQ modulator configured to generate a complex IQ signal
Data Source
AI summary
Systems and methods for power budgeting within a coherent optical network are provided. A phase shift controller may be provided for controlling a phase shift (θ) between an in-phase (I) and quadrature (Q) branches of an optical IQ modulator to generate a complex IQ signal. The phase shift of the optical IQ modulator may be controlled between an orthogonal mode, such as a conventional QPSK mode, and a nonorthogonal mode, based on an operational state of the modulator. The nonorthogonal mode may include a high-suppression mode and a high-power mode.