Multi-Dimensional PPM WDM Optical Transmitter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical communication systems for long-range space applications face challenges in achieving high photon information efficiency due to limitations in laser technology, particularly in implementing larger numbers of slots and higher peak power for one-dimensional pulse position modulation (PPM) schemes.
Innovation Solution
The integration of multi-dimensional PPM schemes with wavelength division multiplexing (WDM) or wavelength division multiple access (WDMA) technologies, expanding the modulation dimensions to include time, wavelength, and polarization, allows for higher photon information efficiencies using existing laser technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If one-dimensional PPM scheme is used with larger number of slots to achieve higher transmission speed, then transmission speed is improved, but implementation complexity and system design challenges increase substantially
Solution Approach 1:
The patent transitions from one-dimensional PPM modulation to two-dimensional modulation by combining time slots with wavelength dimensions. This allows the system to achieve higher transmission speeds by utilizing multiple wavelengths simultaneously, effectively adding a new dimension to the modulation scheme and reducing the complexity burden on single-slot implementation.
Solution Approach 2:
The patent merges PPM time-slot modulation with wavelength division multiplexing (WDM) technology. By combining these two approaches, the system achieves higher transmission capacity without proportionally increasing implementation complexity, as the wavelength dimension provides an additional degree of freedom that simplifies the overall system design.
2Loss of information
If larger number of slots and higher peak power are used to achieve higher photon information efficiency, then photon information efficiency is improved, but laser technology limitations are exceeded
Solution Approach 1:
The patent introduces wavelength as an additional dimension beyond time slots. By modulating multiple wavelengths simultaneously with PPM, the system achieves higher photon information efficiency without requiring single-laser peak powers that exceed current laser technology capabilities. Each laser operates at manageable power levels while the collective system achieves high efficiency through dimensional expansion.
3Loss of information
If one-dimensional PPM with larger M is implemented to increase bits per photon, then photon information efficiency is improved, but slot duration requirements become more stringent
Solution Approach 1:
The patent adds wavelength dimension to the modulation scheme, allowing the system to achieve higher bits per photon without proportionally reducing slot duration. By distributing information across multiple wavelengths and time slots, the system maintains feasible slot durations while achieving the desired information efficiency through the combined dimensional space.
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 enhances photon information efficiency by increasing the number of bits per photon, from 6 bits per photon in one-dimensional PPM to 10 bits per photon using 64-PPM with 16 wavelengths, while maintaining manageable average power levels, thus overcoming the limitations of current laser technology.
Implementation Method 1
The integration of multi-dimensional PPM schemes with wavelength division multiplexing (WDM) or wavelength division multiple access (WDMA) technologies, expanding the modulation dimensions to include time, wavelength, and polarization
Implementation Method 2
a plurality of pulse position modulators configured to receive data bits; wherein: a transmission period of the optical transmitter comprises a plurality of time slots; and based on the data bits, the plurality of pulse position modulators are configured to select, during each transmission period: one time slot of the plurality of time slots for transmission of an optical pulse
Implementation Method 3
an optical multiplexer is configured to multiplex the intensity modulated optical pulse to generate an optically multiplexed signal
Data Source
AI summary
Methods and devices implementing a combination of multi-dimensional pulse position modulation (PPM) with wavelength division multiplexing (WDM) or wavelength division multiplexing multiple access (WDMA) for long range space communications are disclosed. The described multi-dimensional PPM scheme can use the laser wavelength and/or polarization as the additional dimension(s) to the time dimension. Through examples it is shown that the disclosed teachings result in a higher photon information efficiency. Various exemplary embodiments are also presented to highlight the applications benefiting from the disclosed methods and devices.