Adaptive Modulation for Mixed Optical Receivers
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Solution Overview
Problem
Current Passive Optical Network (PON) technologies face limitations in increasing data rates beyond 50 Gbps per wavelength due to spectrum scarcity and nonlinear physical effects, making it challenging to support higher data rates without replacing existing low-cost receivers or using coherent technology that requires separate wavelengths.
Innovation Solution
An apparatus that modulates a single-wavelength carrier wave using a combination of intensity, phase, and polarization variations, allowing selection of modulation schemes based on the type of optical receivers installed, enabling coexistence of high-tier coherent and traditional low-cost receivers on the same wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional IM-DD method is used to increase data rate, then data rate can reach about 50 Gbps, but it cannot support data rates of 100 Gbps per wavelength or higher
Solution Approach 1:
The system dynamically switches between IM and coherent modulation schemes based on the receiver type detected at the remote end. The OLT adapts its modulation method in real-time, using IM for DD receivers and coherent modulation for coherent receivers, thereby resolving the contradiction between achieving high data rates and maintaining compatibility with different receiver types
Solution Approach 2:
The patent changes the modulation parameter from fixed IM-DD to adaptive modulation that can switch between IM and coherent schemes. By changing the modulation parameter based on receiver type, the system achieves both high data rates for coherent receivers and compatibility with legacy DD receivers
2Productivity
If coherent technology is applied to increase data rate, then higher data rate is achieved, but all legacy technology needs to be replaced
Solution Approach 1:
The patent segments the network into two distinct modulation paths: IM path for legacy DD receivers and coherent path for high-speed coherent receivers. This segmentation allows each receiver type to operate independently with its appropriate modulation scheme, eliminating the need to replace all legacy receivers while still enabling high data rates for users who upgrade to coherent receivers
Solution Approach 2:
The OLT is designed with multi-functionality to support both IM and coherent modulation schemes. This universal capability allows the single OLT to serve both legacy DD receivers and modern coherent receivers simultaneously, avoiding the need to replace all legacy equipment while providing high data rate capability to those who need it
3Productivity
If WDM is used to increase data rate by using more wavelengths, then total capacity increases, but spectrum in O-band is already densely occupied and nonlinear physical effects arise
Solution Approach 1:
Instead of expanding in the wavelength dimension (WDM), the patent expands in the modulation dimension by implementing both IM and coherent modulation schemes on the same wavelength. This dimensional shift allows doubling the data rate per wavelength through coherent modulation without adding new wavelengths, thereby avoiding nonlinear effects while increasing total network capacity
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 approach allows for increased data rates without replacing legacy receivers, utilizes existing infrastructure, and avoids spectrum scarcity issues, enabling efficient data transmission while maintaining compatibility with both intensity and coherent detection receivers.
Implementation Method 1
a first module configured to modulate the carrier wave according to a first modulation scheme, by varying the intensity of the carrier wave
Implementation Method 2
by controlling the phase and/or polarization of the carrier wave during selected periods
Implementation Method 3
by controlling the phase and/or polarization of the carrier wave during selected periods
Implementation Method 4
Direct Detection (DD) at the receiver side, meaning that the receiver only responds to changes in the receiving signal power
Implementation Method 5
A specific optical receiver is required, which allows for coherent detection, meaning that the phase of an optical signal can be recovered
Data Source
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AI summary
Apparatus (200) for signal modulation in a point-to-multipoint optical network (100), the apparatus (200) being configured to modulate a single-wavelength carrier wave (204) before distribution towards optical receivers of a first type (101) adapted for intensity detection and a second type (102) adapted for optical field detection, the apparatus (200) comprising: - a first module (201) configured to modulate the carrier wave (204) by varying the intensity of the carrier wave (204), thereby representing data intended for the first type of receivers (101), and by controlling the phase and/or polarization of the carrier wave (204) during selected periods; - a second module (202) configured to modulate the carrier wave (204) by varying the phase and/or polarization of the carrier wave (204), thereby representing data intended for the second type of receivers (102), and by varying the intensity of the carrier wave (204) during selected periods.