WDM Seed Beam Architecture With Shared EOM for Scalable Fiber Lasers
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Solution Overview
Problem
Fiber laser amplifier systems face limitations in scaling output power due to spectral brightness constraints and nonlinear impairments, such as stimulated Brillouin scattering and Kerr nonlinearity, which require narrow linewidth and low relative intensity noise seed beams, and are hindered by high size, weight, and power (SWaP) requirements of master oscillator front-end assemblies (MOFEAs) with parallel high power RF sources and electro-optic modulators.
Innovation Solution
A wavelength division multiplexing (WDM) seed beam source with a single electro-optic modulator and spectral multiplexer/demultiplexer configuration that combines and separates seed beams onto a single fiber, reducing the need for multiple RF sources and modulators, and modularizing the seed beam source to decouple component powers from channel count, allowing for lower power components and flexible wavelength selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple master oscillators with parallel RF sources and electro-optic modulators are used to generate seed beams at different wavelengths, then the system can provide high spectral brightness and narrow linewidth, but the size, weight, and power (SWaP) requirements increase significantly
Solution Approach 1:
The patent combines multiple seed beam generation channels into a single integrated system. Multiple electro-optic modulators are combined into one shared modulator that sequentially modulates seed beams from different wavelengths. The RF sources are also shared across channels through time-multiplexed operation, reducing the total number of components while maintaining the ability to generate narrow linewidth, high spectral brightness seed beams for each wavelength channel.
Solution Approach 2:
The system employs periodic time-multiplexed operation where a single shared modulator and RF source sequentially serve multiple wavelength channels. Each channel is activated in periodic intervals, with the modulator switching between different seed beam wavelengths in a cyclic manner. This periodic action allows one component to fulfill the function of multiple components while maintaining the required modulation depth and linewidth for each channel.
2Power
If the number of seed beam channels is increased to scale output power, then higher total power is achieved, but the number of duplicate components (RF sources, modulators) increases proportionally
Solution Approach 1:
The patent implements universal components that serve multiple functions across different wavelength channels. A single electro-optic modulator is designed to handle multiple seed beam wavelengths sequentially, and the RF source is configured to provide modulation signals for all channels through time-multiplexed operation. This multi-functionality allows the system to scale to higher channel counts and total output power without proportionally increasing the number of RF sources and modulators.
Solution Approach 2:
The system employs dynamic switching and time-multiplexed resource allocation to allow a fixed number of components to serve a variable number of channels. The modulator and RF source dynamically switch between channels based on operational requirements, enabling the system to adapt to different channel counts and power scaling needs without requiring additional hardware for each channel.
3Measurement precision
If narrow linewidth seed beams are used to achieve high spectral brightness, then beam quality is improved, but the system becomes more sensitive to nonlinear impairments such as stimulated Brillouin scattering
Solution Approach 1:
The patent applies partial linewidth broadening through electro-optic modulation rather than using fully broadened linewidth. The modulator introduces controlled spectral broadening that is excessive enough to suppress stimulated Brillouin scattering and other nonlinear impairments, but not so excessive as to completely degrade beam quality. This partial action approach finds an optimal balance between suppressing harmful nonlinear effects and maintaining acceptable beam quality for the application.
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 configuration enhances spectral brightness, reduces SWaP and cost, and enables scaling to higher channel counts by eliminating duplicate components and relaxing crosstalk requirements, while maintaining beam quality and preventing spectral broadening.
Implementation Method 1
an electro-optic modulator (EOM) that modulates the combined seed beams on the fiber
Implementation Method 2
The amplified fiber seed beams are then directed to a diffraction grating, or other wavelength-selective element, that combines the different wavelength fiber beams into a single output beam
Data Source
Figure 1~2
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AI summary
A WDM seed beam source for a fiber laser amplifier system that includes a number of master oscillators that generate seed beams at different wavelengths and a spectral multiplexer that multiplexes all of the seed beams onto a single fiber. An EOM modulates the combined seed beams on the single fiber and a spectral demultiplexer then separates the modulated seed beams into their constituent wavelengths on separate fibers before the seed beams are amplified and spectrally combined. The fiber laser amplifier system includes a separate fiber amplifier that amplifies the separated seed beams, an emitter array that directs the amplified beams into free space, beam collimating optics that focuses the uncombined beams, and an SBC grating responsive to the collimated uncombined beams that spatially combines the collimated uncombined beams.