Semiconductor Laser Relaxation Oscillation Comb Generator
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Solution Overview
Problem
Existing comb generator devices for fibre optic communications are expensive and bulky due to the use of complex modulation techniques, which hinder efficient fibre usage and bandwidth increase in access networks.
Innovation Solution
A comb wavelength generator device utilizing a semiconductor laser driven by a DC bias current and a sinusoidal RF signal, where the RF signal frequency is close to the relaxation oscillation frequency of the laser, producing a coherent optical wavelength comb with reduced hardware complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amplitude modulator pair is used to generate optical wavelength comb, then coherent comb output is achieved, but device cost and size increase
Solution Approach 1:
The patent extracts the essential function of generating coherent comb lines from the complex modulator system and implements it directly through laser relaxation oscillations. By removing the modulators and using only the laser cavity and injection current control, the device achieves comb generation without the bulky and expensive modulation hardware while maintaining coherence through the natural relaxation oscillation mechanism.
Solution Approach 2:
The laser device serves itself by utilizing its own relaxation oscillations to generate the comb spectrum. The laser's inherent physical properties (gain medium, cavity resonances, and relaxation oscillations) are harnessed to produce the desired coherent frequency comb without requiring external modulators or complex control systems. The system uses its own operational characteristics to achieve the comb output.
2Manufacturing precision
If amplitude modulator pair is used to generate optical wavelength comb, then equally spaced frequency lines are produced, but device cost and size increase
Solution Approach 1:
The patent removes the modulator hardware that traditionally creates equally spaced frequency lines and replaces it with the laser's natural relaxation oscillation mechanism. The equally spaced comb lines emerge from the laser's own resonant frequencies and relaxation dynamics, eliminating the need for expensive and bulky modulation components while maintaining precise frequency spacing.
Solution Approach 2:
The patent changes the operating parameters of the laser, specifically operating it near the threshold current and using injection currents at or near the relaxation oscillation frequency. This parameter adjustment causes the laser to naturally generate equally spaced frequency lines through its relaxation oscillations, replacing the need for external modulators that traditionally created these spectral lines.
3Reliability
If modulators are used in comb generator, then wavelength comb output is achieved, but device becomes bulky and expensive
Solution Approach 1:
The patent extracts the comb generation function from the modulator components and implements it through the laser's intrinsic relaxation oscillations. By removing the modulators entirely and using only the laser with controlled injection current, the device achieves the same comb output quality at significantly lower cost and with simpler manufacturing requirements.
Solution Approach 2:
The patent replaces expensive, complex modulator hardware with a simple laser diode and basic current control circuitry. The laser itself, combined with inexpensive injection current modulation, produces the comb output that previously required costly modulator components. This substitution dramatically reduces device cost while maintaining comb generation 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
The solution results in a low-cost, coherent comb generator that minimizes inter-pulse timing jitter and maintains phase coherence, enabling efficient fibre usage and bandwidth increase in fibre optic communications systems.
Implementation Method 1
a laser, a biasing circuit for providing a DC bias current, an RF circuit providing a RF signal, and a drive circuit for combining the RF signal with the DC bias current to provide a drive current to the laser
Implementation Method 2
The frequency of the RF signal is suitably selected to be close to the relaxation oscillation frequency of the laser and preferably within 25% of the relaxation oscillation frequency of the laser
Data Source
AI summary
The present application relates to comb frequency generator devices generally and more particularly to the use of comb generators for use in fibre optic communications. More particularly, the application provides a frequency comb generator device. The device comprises a laser (30), a biasing circuit for providing a DC bias current (26), an RF circuit (22) providing a RF signal and a drive circuit (28) for combining the RF signal with the DC bias current to provide a drive current to the laser (30). With the DC bias current below threshold of the laser diode and RF bias with a frequence close to the relaxation ascillation frequency of the laser diode, a periodic pulse train is emitted with constant phase.