Single-Laser Bidirectional Optical Communication with Phase Shifting
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Solution Overview
Problem
Conventional optical communication systems for data centers face challenges such as high installation and maintenance costs, immobility, high outage probability due to fiber-related faults, and complex architectures, especially when using free-space optical links for modular data centers, which are prone to atmospheric turbulence and require multiple laser sources.
Innovation Solution
A bi-directional optical communication system utilizing a single laser source with a combination of modulation schemes, including differential quadrature phase shift keying (DQPSK) and On-Off keying (OOK), and a wavelength regenerator to achieve high data rates and cost-efficient communication over turbulent free-space optical channels, using components like Mach-Zehnder modulators, phase shifters, and electro-absorption modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If free-space optical links are used for modular data centers, then mobility and flexibility are improved, but the system becomes prone to atmospheric turbulence effects
Solution Approach 1:
The patent introduces phase shifters as intermediary components that actively compensate for atmospheric turbulence effects by adjusting the phase of optical signals. This mediator approach allows the system to maintain both mobility benefits and reliability against turbulence through real-time phase correction.
Solution Approach 2:
The system dynamically changes optical parameters (phase and wavelength) to adapt to atmospheric conditions. By modifying these parameters in response to turbulence, the system maintains reliable communication while preserving the mobility advantages of free-space optical links.
2Reliability
If multiple laser sources are used in free-space optical links, then communication reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes a single laser source perform multiple functions by implementing both DQPSK and OOK modulation schemes on the same optical carrier. This multi-functional approach achieves reliable bidirectional communication without requiring separate laser sources for different modulation types, thereby reducing device complexity while maintaining reliability.
Solution Approach 2:
The system dynamically switches between different modulation schemes (DQPSK and OOK) on a single laser source depending on communication requirements. This dynamic capability allows one laser to adaptively serve multiple communication needs, reducing the total component count while maintaining communication reliability.
3Productivity
If DQPSK and OOK modulation schemes are combined, then data rate is improved, but detection complexity increases
Solution Approach 1:
The patent segments the detection process into separate functional blocks: a photodetector for optical-to-electrical conversion, a low-pass filter for signal conditioning, and a bit-error rate analyzer for performance evaluation. This segmentation simplifies the detection of combined DQPSK and OOK schemes by breaking down the complex detection task into manageable, standardized stages.
Solution Approach 2:
The patent introduces a low-pass filter as an intermediary component between the photodetector and the bit-error rate analyzer. This mediator smooths the combined DQPSK and OOK signal, making it easier to detect and analyze, thereby reducing overall detection complexity while maintaining high data rate performance.
4Length of stationary object
If optical signals are transmitted over turbulent channels, then communication distance is improved, but signal quality deteriorates
Solution Approach 1:
The patent employs wavelength conversion as a parameter change technique to regenerate optical signals after long-distance transmission through turbulent channels. By converting to a different wavelength and regenerating the signal, the system extends communication distance while restoring signal quality, effectively decoupling distance from signal degradation.
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 system provides high data rates and cost-efficient communication with reduced component count, simplifying detection techniques and mitigating atmospheric turbulence effects, while maintaining mobility and flexibility in data center interconnects.
Implementation Method 1
The at least two MZM are configured to phase modulate the at least two optical pulsed signals using the at least two differentially encoded electrical signals to provide a first phase modulated optical pulsed signal and a second phase modulated optical pulsed signal
Implementation Method 2
The phase shifter is configured to phase shift the first phase modulated optical pulsed signal to generate a phase shifted phase modulated optical pulsed signal
Implementation Method 3
The EAM is configured to amplitude modulate the processed optical pulsed signal using the third electrical signal to provide a phase-amplitude modulated optical pulsed signal
Implementation Method 4
The optical amplifier is configured to amplify the pulse-amplitude modulated optical pulsed signal and generate a transmitter optical pulsed signal for transmission
Data Source
AI summary
A bi-directional optical communication system employing a minimum number of single-mode high repetition rate pulsed optical signal sources to achieve cost efficiency while maintaining high data rates. The bi-directional optical communication system includes a first optical data processing unit and a second optical data processing unit. The first optical data processing unit modulates a pulsed optical source using a differential quadrature phase shift keying (DQPSK) modulation and two-level pulse amplitude (PAM-2) modulation and then demodulates it to achieve a pulse amplitude modulated signal. The second optical data processing unit reuses the same optical carrier by passing it through a regenerative wavelength converter to generate three pulsed optical carriers at different wavelengths and employs an On-off keying (OOK) modulation scheme. These carriers are employed to send uplink data at a same rate of as the downlink. As a result, large data is transmitted from one data center to another data center through a downlink and uplink free space optical link network.