Light Amplifier Peak Power Detection and Control
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Solution Overview
Problem
Fiber amplifiers face challenges in detecting and controlling the peak power of each output light pulse due to the variation in seed light conditions and high repetition frequencies, leading to difficulties in maintaining uniform pulse strength and stabilizing laser output.
Innovation Solution
A light amplifier system that includes a light amplifying fiber, a seed light source, an excitation light source with adjustable power levels, a detector with a light receiving element, integration circuit, and a control unit to monitor and adjust the peak power of output pulses, using a variable gain amplifier and AD converter to ensure precise control based on detected peak values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the repetition frequency of pulses is increased to improve productivity, then the output power increases, but it becomes more difficult to measure the strength of each pulse and feed back to control the pulse strength uniformly
Solution Approach 1:
The patent replaces the conventional average power measurement method with a peak power measurement system using a photodiode detector and oscilloscope. This substitution enables precise measurement of individual pulse strengths even at high repetition frequencies, resolving the contradiction between productivity improvement and measurement precision maintenance.
2Adaptability or versatility
If the seed light conditions are varied to increase adaptability, then the variation range of peak value is widened, but it becomes more difficult to detect the peak value for each pulse
Solution Approach 1:
The patent employs an optical detection system using a photodiode and oscilloscope to directly measure peak power, replacing indirect measurement methods. This substitution enables accurate detection of peak values across varying seed light conditions, resolving the contradiction between adaptability and measurement difficulty.
Solution Approach 2:
The patent implements a feedback control system where the measured peak power values are used to adjust the seed light conditions. This feedback mechanism maintains uniform pulse strength despite variations in seed light, resolving the contradiction between adaptability and detection difficulty.
3Speed
If the response time of the exciting LD is reduced to improve control speed, then the laser output response improves, but the time period after output change until laser output changes remains about 1 ms or more
Solution Approach 1:
The patent implements preliminary excitation by applying excitation light to the fiber amplifier before the actual pulse emission. This preliminary action prepares the gain medium in advance, reducing the delay time between control signal and laser output while maintaining fast response capability.
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
Enables accurate detection and control of peak power for each output light pulse, stabilizing the laser output and improving processing quality by adjusting excitation light power according to detected values, even at high repetition frequencies.
Implementation Method 1
a light amplifying fiber for amplifying seed light with excitation light
Implementation Method 2
a light receiving element for receiving the group of output light pulses
Data Source
AI summary
A technique of detecting a peak value for each output light pulse from a light amplifier by using a light amplifying fiber is provided. A peak value detector 16 detects power of an output light pulse which is output from the light amplifying fiber. A light receiving element 15 receives a group of light pulses including a plurality of pulses and converts the group of light pulses into a current signal. A current/voltage converter circuit 31 converts the current output from the light receiving element to voltage. An integration circuit 32 integrates the voltage output from the current/voltage converter circuit 31. A PGA (Programmable Gain Amplifier) 33 amplifies the signal output from the integration circuit 32 and provides the signal for the AD converter circuit 34. The gain of the PGA 33 is set by a gain setting signal from the signal processing circuit 40. The signal processing circuit 40 adjusts the gain of the PGA 33 so that the gain increases as the repetition frequency of the group of pulses increases.