Optical Receiver LO Power Control for Lower Shot Noise
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Solution Overview
Problem
Conventional optical receivers using automatic gain control (AGC) mode operate with constant maximum optical power, leading to high shot noise and TIA noise, which degrades bit error rate (BER) performance and increases complexity, cost, and power consumption.
Innovation Solution
Implementing an automatic power control (APC) mode that adjusts the power of the optical local oscillator (LO) signal based on signal strength, reducing noise and maintaining constant transimpedance, thereby improving sensitivity and durability while reducing design complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automatic gain control (AGC) mode is used with constant maximum optical power, then the optical receiver can operate with fixed gain, but shot noise and TIA noise increase, degrading bit error rate performance
Solution Approach 1:
The patent implements dynamic optical power control by adjusting the optical LO signal power based on the detected optical signal strength. The optical amplifier dynamically modifies the LO signal power to maintain optimal signal-to-noise ratio conditions, transitioning from static AGC operation to adaptive power control that responds to varying input signal conditions.
Solution Approach 2:
The system changes the optical power parameter of the LO signal based on detected signal strength conditions. By monitoring the optical signal strength and adjusting the LO power accordingly, the system optimizes the operating point to minimize noise while maintaining reliable detection, directly addressing the bit error rate performance issue.
2Reliability
If constant maximum optical power is used in AGC mode, then the system operates with simplified control, but noise increases and sensitivity decreases
Solution Approach 1:
The patent implements a feedback mechanism where the optical signal strength is detected and used to control the optical amplifier that adjusts the LO signal power. This closed-loop feedback system continuously monitors signal conditions and adjusts power levels to maintain optimal sensitivity while minimizing noise generation.
Solution Approach 2:
The system transitions from static power operation to dynamic power adjustment, where the optical LO signal power is continuously adapted based on the detected optical signal strength. This dynamic control enables the system to maintain high sensitivity across varying input conditions while minimizing noise.
3Reliability
If automatic power control (APC) mode is implemented to reduce noise, then bit error rate performance improves, but device complexity increases
Solution Approach 1:
The optical amplifier serves multiple functions: it amplifies the optical LO signal while simultaneously acting as the power control element in the APC loop. By integrating the power control function into the existing amplifier component, the system achieves noise reduction and improved BER performance without adding separate dedicated control hardware, thus limiting the increase in device complexity.
Solution Approach 2:
The patent combines the optical signal amplification function with the optical power control function in a single integrated approach. The optical amplifier is used both for its primary amplification purpose and as the actuator for power control, merging two functions into one component to reduce overall system complexity while achieving the desired noise reduction.
4Use of energy by moving object
If constant maximum optical power is used, then the system maintains stable operation, but power consumption increases
Solution Approach 1:
The system implements dynamic power adjustment where the optical LO signal power is adapted in real-time based on the detected optical signal strength. This dynamic control allows the system to consume only the necessary power for current operating conditions, reducing overall power consumption while maintaining stable operation through continuous adaptation to signal variations.
Solution Approach 2:
The optical power parameter is dynamically changed based on signal strength conditions, allowing the system to operate at optimal power levels rather than constant maximum power. This parameter adaptation reduces energy consumption while maintaining operational stability by adjusting power to match actual signal 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
The APC mode enhances bit error rate performance, reduces noise, and simplifies the design and operation of optical receivers, supporting high bandwidth and linearity with lower power consumption.
Implementation Method 1
an optical amplifier connected to a local oscillator (LO) and a plurality of optical hybrid mixers of the optical receiver, wherein the optical amplifier is configured to: receive an optical LO signal from the LO; receive a voltage value associated with an optical input signal of the optical receiver; adjust a power of the optical LO signal based on the voltage value
Data Source
AI summary
An optical receiver includes an optical amplifier that is optically connected to a local oscillator (LO) and a plurality of optical hybrid mixers of the optical receiver and that is electrically connected to a controller. The optical amplifier is configured to receive an optical LO signal from the LO, receive a voltage value associated with an optical input signal of the optical receiver, control a power of the optical LO signal based on the voltage value, and provide, after adjusting the power of the optical LO signal, the optical LO signal to the plurality of optical hybrid mixers. The controller, is configured to determine the voltage value associated with the optical input signal and cause the voltage value to be provided to the optical amplifier.