Output Coupler Modulated Laser for Optical Communication
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Solution Overview
Problem
Current laser designs for optical communication systems face limitations in modulation schemes due to the physical properties of optical resonators and gain media, leading to restricted modulation rates and potential signal distortion, such as chirp, which affect the efficiency and bandwidth of data transmission.
Innovation Solution
A modulated laser with a controllable output coupler that selectively allows circulating light to exit the optical resonator, enabling direct amplitude and phase modulation through an interference section responsive to a control signal, decoupling the modulation response from the intrinsic properties of the gain medium and maintaining a steady-state power level, thereby exceeding relaxation resonance frequencies and minimizing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct modulation of laser output is used, then modulation rate can be increased, but signal distortion such as chirp increases
Solution Approach 1:
The laser system is segmented into independent functional components: a laser source that generates continuous wave output and a separate external modulator that performs modulation. This separation allows the laser to operate at optimal conditions while the modulator handles high-rate modulation without generating chirp, thus resolving the contradiction between high modulation rate and low signal distortion.
Solution Approach 2:
An external modulator acts as an intermediary between the laser source and the optical signal transmission. This intermediary device takes the stable laser output and applies modulation externally, enabling high-speed modulation while maintaining signal quality and avoiding the chirp that would result from direct laser modulation.
2Object-generated harmful factors
If external modulation schemes are used, then signal distortion is reduced, but device complexity increases
Solution Approach 1:
The patent combines the laser source and external modulator into an integrated laser system where the modulator is coupled directly to the laser output. This merging approach maintains the advantages of external modulation (reduced signal distortion) while simplifying the overall system architecture and reducing the complexity that would arise from completely separate components.
3Device complexity
If modulation is performed within the optical resonator, then device complexity is reduced, but modulation response is limited by gain medium properties
Solution Approach 1:
The modulation function is extracted from the optical resonator and placed in an external modulator. This extraction allows the resonator to maintain its simple structure while the modulation response is determined by the external modulator's characteristics rather than being constrained by the gain medium's properties, thus achieving both low complexity and high modulation response.
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 allows for high-efficiency modulation with reduced signal distortion and increased bandwidth, enabling the use of advanced modulation schemes like PSK and QAM, while maintaining a stable power level and minimizing chirp, thus enhancing the performance of optical communication systems.
Implementation Method 1
An interference section optically couples the input port with each of the output-coupled port and through port. An operating characteristic of the interference section can be controllable by the control signal to provide selective optical interference in the interference section
Implementation Method 2
In response to the control signal, the output coupler can modulate at least one of amplitude and phase in the modulated optical signal. In particular, the output coupler can apply any of an amplitude modulation, a Phase-Shift Keying (PSK), and a Quadrature Amplitude Modulation (QAM) scheme
Implementation Method 3
A gain medium is housed within the optical resonator in the path of the circulating light, and a pump delivers excitation energy to the gain medium above a laser threshold of the optical resonator to bring the circulating light into coherent oscillation
Data Source
AI summary
There is provided an output coupler modulated laser. The laser includes an optical resonator for light to circulate within, a gain medium housed within the optical resonator and a pump. An output coupler included in the optical resonator is responsive to a control signal to generate a modulated optical signal at a laser output port, and a complementary signal at a through port to retain circulating light within the optical resonator. The output coupler and the pump are jointly controllable to maintain the power level of the circulating light substantially at a selected, steady state level, and to decouple the modulation response of the laser from the intrinsic response of the circulating light due to interaction with the gain medium. The output coupler is configurable for simple amplitude modulation, Phase-Shift Keying (PSK), Quadrature Amplitude Modulation (QAM), and is suitable for use with high-finesse, micron or millimeter scale resonators.