Optical Fiber Amplifier Pump Control for Parasitic Oscillation
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Solution Overview
Problem
Optical fiber amplifiers, such as YDFA, face issues with unintended oscillation due to parasitic oscillations at shorter wavelengths when pumped, leading to potential damage from increased gain and reflected ASE light, especially when reflective elements are present or signal light intensity decreases.
Innovation Solution
A laser device with an optical fiber amplifier, a signal light detector, and a control unit that suppresses pumping power when signal light intensity drops below a predetermined threshold or ASE light intensity exceeds a reference value, preventing gain from exceeding oscillation thresholds and reducing the risk of oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the optical fiber amplifier is pumped to amplify signal light, then the amplification gain is improved, but parasitic oscillation at shorter wavelengths occurs due to higher gain at those wavelengths
Solution Approach 1:
The patent applies preliminary anti-action by detecting the presence of reflective elements before they can cause harmful oscillations. The system uses a detector to identify reflective elements in the optical path and preemptively adjusts pump power or activates suppression mechanisms to prevent parasitic oscillation at 1030nm before it occurs, rather than reacting after damage has been caused
Solution Approach 2:
The patent implements feedback control by continuously monitoring the optical path for reflective elements and adjusting the pump power accordingly. When a reflective element is detected, the system feeds back this information to the control unit, which then reduces pump power to prevent the gain from exceeding the oscillation threshold, thereby eliminating the harmful oscillation condition
2Power
If the signal light intensity decreases or becomes zero, then the population inversion density increases and amplifier gain increases abnormally, but this causes the laser to oscillate at 1030 nm wavelength and may cause damage to the optical fiber amplifier
Solution Approach 1:
The patent applies preliminary action by detecting signal light intensity changes before they lead to dangerous oscillations. When the detector senses that signal light intensity has decreased below a threshold level, the control unit preemptively reduces pump power to prevent population inversion from reaching levels that would cause harmful 1030nm oscillation and potential amplifier damage
Solution Approach 2:
The system implements preliminary anti-action by monitoring signal light intensity and anticipating the harmful effect of excessive gain. When signal light intensity drops, the control unit preemptively counteracts the potential oscillation by reducing pump power before the population inversion density reaches the critical level that would cause damage
3Power
If reflective elements are present due to fouling or other causes, then ASE light may be reflected back into the optical fiber amplifier and cause oscillation, but this increases the output intensity and creates danger of damage to the amplifier
Solution Approach 1:
The patent implements feedback control by using the detector to monitor for reflected ASE light caused by reflective elements. When reflection is detected, the system feeds back this information to the control unit, which then reduces pump power to prevent the amplified spontaneous emission from reaching intensity levels that would cause damage to the amplifier or auxiliary optical elements
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 solution effectively prevents unintended oscillation in optical fiber amplifiers by reducing gain when signal light intensity decreases or ASE light increases, thereby protecting the amplifier and auxiliary components from damage.
Implementation Method 1
an optical fiber amplifier having gain in a wavelength band that includes signal light, and that amplifies and emits that signal light
Implementation Method 2
a pump light source that pumps the optical fiber amplifier; a control unit that controls pumping power for pumping the optical fiber amplifier
Implementation Method 3
a signal light detector that detects signal light being propagated to the optical fiber amplifier
Implementation Method 4
an ASE photodetector that detects light that is emitted from the optical fiber amplifier and that has wavelength for which the gain, in the gain distribution of the optical fiber amplifier, is higher than for the signal light
Data Source
AI summary
A laser device includes: an optical fiber amplifier that amplifies and emits a signal light; a control unit that controls pumping power for pumping the optical fiber amplifier; and a signal light detector that detects signal light being propagated to the optical fiber amplifier or an ASE photodetector that detects light that is emitted from the optical fiber amplifier and that has wavelength for which the gain is higher than for the signal light, wherein the control unit suppresses the pumping power for pumping the optical fiber amplifier, when the intensity of the signal light detected by the signal light detector becomes less than or equal to a predetermined signal reference value, or when the intensity of the spontaneously emitted light detected by the ASE photodetector becomes greater than or equal to a predetermined ASE reference value.