Tunable Laser With Optical Spectrum Reshaper for High-Speed Modulation
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Solution Overview
Problem
Existing laser transmitters struggle to achieve high data rates in excess of 10 Gb/s and broad frequency modulation capabilities, as not all lasers can be frequency modulated adequately across a range of frequencies, limiting their suitability for use with optical spectrum reshapers.
Innovation Solution
A tunable laser with a short gain section and sampled gratings or ring resonators, coupled with an optical spectrum reshaper, is used to generate adiabatically chirped pulses across a broad frequency range, allowing for high data rate modulation by adjusting the temperature of the gratings or heaters to tune the laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a laser is tuned across a broad frequency range, then frequency modulation capability is improved, but the ability to frequency modulate at high data rates deteriorates
Solution Approach 1:
The laser is divided into separate functional sections: a gain section for light amplification and a tuning section with sampled gratings for frequency control. This segmentation allows the gain section to operate at high speeds while the tuning section provides broad frequency range, resolving the contradiction between speed and adaptability
Solution Approach 2:
Different sections of the laser have specialized properties optimized for their specific functions. The gain section has properties optimized for high-speed modulation, while the sampled grating section has properties optimized for broad frequency tuning. This local optimization allows each section to excel at its designated task without compromising the other
2Speed
If the gain section optical path length is reduced, then frequency modulation speed is improved, but the total optical path length becomes insufficient
Solution Approach 1:
The optical path is segmented into a short gain section and a separate tuning section with sampled gratings. The gain section maintains a short optical path length for high-speed modulation, while the tuning section provides the necessary total optical path length for stable laser operation and broad frequency tuning
Solution Approach 2:
The sampled gratings act as an intermediary element between the gain section and the output. They provide the necessary optical path length and frequency control without interfering with the high-speed modulation capabilities of the gain section, effectively mediating between the conflicting requirements
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 enables high-speed, tunable laser transmitters capable of operating at data rates exceeding 10 Gb/s across a broad range of frequencies, enhancing amplitude modulation and phase relationships in pulses, thus improving transmission performance.
Implementation Method 1
the laser may have a gain section coupled to first and second sampled gratings by an optical power splitter. The sampled gratings may be reverse-biased to facilitate the generation of high data rate adiabatic pulses
Implementation Method 2
The laser may be tuned by changing the temperature of the sampled gratings according to the thermo-optic effect
Implementation Method 3
The ring resonators are coupled to stripe heaters for independently changing the frequency response of the ring resonators
Data Source
AI summary
An optical transmitter is disclosed including a widely tunable laser coupled to a periodic optical spectrum reshaper (OSR) to convert frequency modulated pulses from the laser into amplitude modulated pulses. The laser is tuned to generate pulses corresponding to passbands of the OSR spanning a wide range of frequencies. The laser includes a gain section having an optical path length substantially shorter than the total optical path length of the laser. The laser may be a Y-branch laser having reverse-biased sampled gratings or ring resonator filters tuned by stripe heaters. The laser may also include a reflective external cavity section tunable by modulating the temperature of ring resonators or etalons. The OSR may be integrally formed with the external cavity of the ECL laser.