Tunable Laser Wavelength Control via Phase Oscillation
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Solution Overview
Problem
External resonator type laser devices face challenges in preventing signal deterioration due to mode hopping and stimulated Brillouin scattering, particularly on the short wave side where the wavelength margin between the peak transmission wavelength and mode hop boundary is smaller, leading to increased side modes and discontinuous wavelength variation.
Innovation Solution
Incorporating light intensity detecting means and phase adjustment signal oscillating means to synchronize light intensity detection with phase adjustment signal oscillation, allowing for precise control of the wavelength to avoid mode hop boundaries and reduce Brillouin scattering effects by varying the phase adjustment signal with a period shorter than the dither control period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dither control is applied to maximize light intensity, then light intensity is improved, but mode hop occurs on the short wave side causing signal deterioration
Solution Approach 1:
The patent applies periodic oscillation to the phase adjustment signal at a frequency higher than the dither control frequency. This periodic action creates a time window where the wavelength is shifted away from the mode hop boundary on the short wave side, allowing the system to achieve maximum light intensity without triggering mode hop and signal deterioration.
Solution Approach 2:
The patent performs preliminary wavelength shifting by oscillating the phase adjustment signal before the dither control can push the wavelength to the mode hop boundary. This preliminary action prevents the harmful effect of mode hop from occurring in the first place, while still allowing the system to operate at optimal light intensity.
2Measurement precision
If phase adjustment signal is varied to control wavelength, then wavelength control precision is improved, but stimulated Brillouin scattering occurs causing signal deterioration
Solution Approach 1:
The patent uses high-frequency periodic oscillation of the phase adjustment signal to continuously vary the wavelength around the optimal point. This periodic variation prevents the wavelength from staying stationary at a point that would trigger stimulated Brillouin scattering, while still maintaining precise wavelength control through the underlying dither control mechanism.
Solution Approach 2:
The patent introduces dynamic oscillation to the phase adjustment signal, making the wavelength continuously variable rather than fixed. This dynamic approach allows the system to maintain precise wavelength control while avoiding the harmful effect of stimulated Brillouin scattering that occurs when the wavelength remains stationary at certain critical values.
3Productivity
If dither control period is used for wavelength optimization, then light intensity optimization is improved, but wavelength margin to mode hop boundary is insufficient on short wave side
Solution Approach 1:
The patent adds another dimension of control by introducing a second frequency layer (higher frequency oscillation) on top of the existing dither control. This dimensional addition allows the system to simultaneously optimize light intensity through dither control while maintaining adequate wavelength margin to the mode hop boundary through the higher frequency oscillation, effectively solving the contradiction between optimization efficiency and precision control.
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 effectively prevents signal deterioration by optimizing wavelength control, maintaining high light intensity and reducing the occurrence of side modes, thereby enhancing the stability of the laser signal.
Implementation Method 1
a resonator including a wavelength selective filter and a semiconductor light amplifier
Implementation Method 2
a semiconductor light amplifier having a phase adjustment region for changing a phase of light passing through the wavelength selective filter
Implementation Method 3
a phase adjustment region for changing a phase of light passing through the wavelength selective filter in accordance with a phase adjustment signal from outside
Implementation Method 4
light intensity detecting means for detecting light intensity of light emitted from the resonator
Data Source
AI summary
A laser device capable of preventing deterioration of a light signal and a controlling method therefor are provided. A wavelength tunable laser module provided with a resonator including the wavelength tunable filter and a semiconductor light amplifier having a phase adjustment region and a light amplifying region, in which a wavelength margin between a peak transmission wavelength of a wavelength tunable filter and a mode hop occurring wavelength on a short wave side is smaller than that on a long wave side includes: a wavelength tunable laser module controller including an optical output sampling portion for detecting light intensity of light emitted from the resonator, a dither signal source for generating a dither signal for varying a phase adjustment signal to be applied to the phase adjustment region so that the detected light intensity becomes the maximum, and an FM signal source for generating an FM signal for oscillating the phase adjustment signal to be applied to the phase adjustment region with a period shorter than a variation period of the dither signal. The optical output sampling portion detects the light intensity in synchronization with oscillation of the phase adjustment signal by the FM signal.