Optical Hybrid Signal Processing for CMRR and Dynamic Range Control
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Solution Overview
Problem
In high-speed optical communication systems, the common mode rejection ratio (CMRR) of photodiodes in digital coherent reception devices increases, leading to signal quality deterioration due to reduced optical signal-to-noise ratio (OSNR) resistance and waveform distortion, which affects the dynamic range of optical signal processing.
Innovation Solution
The proposed optical signal processing device employs optical signal generation units with phase differences to generate multiple optical signals, which are then converted into electrical signals and processed through direct-current component correction units and differential trans-impedance circuits to reduce CMRR and enhance dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital coherent reception systems are used to transmit signals at high bit rates exceeding 40 Gbit/s, then signal quality and reliability are improved through high OSNR resistance and waveform distortion correction, but the common mode rejection ratio (CMRR) of photodiodes increases leading to dynamic range reduction
Solution Approach 1:
The optical signal is divided into multiple wavelength components that are processed separately through wavelength division. Each wavelength component undergoes independent optical signal processing including photoelectric conversion and digital signal processing, allowing the system to handle high bit rates while managing CMRR effects on a per-wavelength basis rather than collectively
Solution Approach 2:
The system changes the operating parameters by introducing direct-current component correction specifically tailored for each wavelength component. By adjusting the direct-current component of electrical signals individually for each wavelength, the system compensates for CMRR variations and maintains optimal dynamic range across different wavelength channels
2Reliability
If photodiodes with high CMRR are used to maintain signal quality, then optical signal-to-noise ratio (OSNR) resistance is improved, but dynamic range of optical signal processing is reduced
Solution Approach 1:
The patent introduces a direct-current component correction unit as an intermediary between photoelectric conversion and subsequent signal processing. This intermediary component specifically addresses the CMRR-induced direct-current offset by correcting it before signals proceed to differential trans-impedance amplification, thereby preserving dynamic range while maintaining OSNR resistance
Solution Approach 2:
The system performs preliminary direct-current component correction on electrical signals immediately after photoelectric conversion but before further processing. By addressing the CMRR effect at this early stage, the system prevents dynamic range reduction from propagating through subsequent processing stages while maintaining the OSNR benefits of high CMRR photodiodes
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 approach effectively suppresses the increase in CMRR and increases the dynamic range of the optical signal processing device, improving the accuracy and reliability of signal processing in high-speed optical communication systems.
Implementation Method 1
a first optical signal generation unit that generates a first optical signal by causing a received optical signal which is received from an outside and a local optical signal to interfere with each other with a first phase difference
Implementation Method 2
a first photoelectric conversion element that converts the first optical signal into a first electrical signal
Data Source
AI summary
An optical hybrid (100) generates a first optical signal by causing local light to interfere with a received optical signal which is received from an outside with a first phase difference. In addition, the optical hybrid (100) generates a second optical signal by causing the local light to interfere with the received optical signal with a second phase difference shifted by π from the first phase difference. Two photoelectric conversion elements (150) photoelectrically convert the first optical signal and the second optical signal, respectively, and generate a first electrical signal and a second electrical signal. A differential trans-impedance amplifier (200) includes a direct-current component correction unit (210), a trans-impedance circuit (240), and a variable gain amplifier (250). The direct-current component correction unit (210) reduces a difference of the magnitude of a direct-current component of the first electrical signal and the magnitude of a direct-current component of the second electrical signal.