Optical Pulse Generator Sinusoidal Chirp Compensation
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Solution Overview
Problem
Chirp compensators in existing optical pulse-generators assume a linear variation of chirp with frequency, leading to increased pedestal components and reduced pulse quality, and require high modulation indices, resulting in increased power consumption and inefficient use of the optical frequency comb's entire band.
Innovation Solution
An optical pulse-generator with a phase modulator and sinusoidal modulation, a chirp compensator using Chirped Fiber Bragg Grating (CFBG) with optimized dispersion characteristics, and a band-pass filter to remove mismatched frequency components, allowing efficient compression of the optical frequency comb and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a chirp compensator is designed assuming linear chirp variation, then the compensation is simplified, but the pedestal becomes large and pulse quality deteriorates
Solution Approach 1:
The patent changes the dispersion characteristics parameter of the chirp compensator from linear to sinusoidal variation to match the actual chirp behavior of the optical frequency comb generator. This parameter change allows the compensator to effectively counteract the sinusoidal chirp, reducing pedestal and improving pulse quality.
Solution Approach 2:
The patent incorporates feedback by measuring the actual chirp characteristics of the optical frequency comb and adjusting the chirp compensator's dispersion characteristics accordingly. This feedback mechanism ensures the compensator is optimized for the actual sinusoidal chirp variation rather than assuming linear variation.
2Length of moving object
If a large modulation index is used to compress the optical pulse, then the pulse width is reduced, but power consumption increases
Solution Approach 1:
The patent optimizes the modulation index parameter to the minimum necessary value that achieves adequate pulse compression. By matching the chirp compensator's dispersion characteristics to the actual sinusoidal chirp, the system achieves effective pulse compression at lower modulation indices, reducing power consumption while maintaining short pulse width.
Solution Approach 2:
The patent converts the sinusoidal chirp variation, which was previously considered a deviation from ideal linear chirp, into a beneficial characteristic. By designing the chirp compensator to match this sinusoidal variation, the system achieves more efficient pulse compression with lower power consumption compared to assuming linear chirp.
3Productivity
If the entire band of optical frequency comb is used for pulse generation, then pulse generation efficiency is improved, but pedestal components increase when using conventional chirp compensators
Solution Approach 1:
The patent changes the dispersion characteristics parameter of the chirp compensator to match the sinusoidal chirp variation of the optical frequency comb. This parameter change allows the system to efficiently utilize the entire frequency comb band for pulse generation while preventing pedestal formation, as the compensator correctly counteracts the chirp across the full bandwidth.
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 enables the generation of optical pulses closer to the Fourier limit by efficiently utilizing the entire band of the optical frequency comb, reducing power consumption, and improving pulse quality by effectively compensating for sinusoidal chirp variations.
Implementation Method 1
a chirp compensator configured to compress and output the optical frequency comb output from the optical frequency comb-generating unit in accordance with the dispersion characteristics in which the dispersion values of frequencies increase with increasing the distance from the center frequency of the optical frequency comb
Implementation Method 2
an optical frequency comb generator which includes an optical modulation unit being a phase modulator and a modulation signal-generating unit configured to generate a modulation signal for modulating light
Data Source
AI summary
Provided is an optical pulse-generator capable of efficiently using by a low driving voltage an entire band of an optical frequency comb input to a chirp compensator for the formation of an optical pulse. According to a graph shown in FIG. 4, dispersion compensation amounts (dispersion characteristics) necessary for a chirp (dispersion) compensator to efficiently compress an optical frequency comb which sinusoidally changes become an inverse of a parabolic coefficient. It is found that the dispersion compensation amount required at the center frequency is 2/π of that of a chirp being approximate to a linear chirp, and the required dispersion compensation amount increases as the frequency shift increases.