Optical Receiving Device Gain Control for High Baud Rate Signal Quality
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Solution Overview
Problem
Existing optical receiving devices face challenges in maintaining signal quality due to fluctuations in frequency response and input referred noise (IRN) of trans impedance amplifiers (TIAs), which worsen as baud rate increases, leading to reduced OSNR resistance and transmission performance.
Innovation Solution
The optical receiving device incorporates a fast response variable optical attenuator (VOA) and erbium doped fiber amplifier (EDFA) to absorb power fluctuations, with a field programmable gate array (FPGA) controlling the gains of TIAs and VOA to minimize difference values, thereby reducing gain fluctuations and maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the baud rate is increased to improve transmission capacity, then the transmission capacity is improved, but the frequency response fluctuation and input referred noise of TIAs worsen, reducing signal quality
Solution Approach 1:
The patent implements automatic gain control (AGC) circuits that continuously monitor the output signal levels from photodiodes and dynamically adjust the gain of TIAs in real-time. This feedback mechanism compensates for frequency response fluctuations and noise variations caused by high baud rates, maintaining stable signal quality despite increased transmission capacity requirements
Solution Approach 2:
The patent dynamically changes operational parameters including TIA gain settings, AGC threshold levels, and decision circuit reference voltages to adapt to varying signal conditions at different baud rates. By adjusting these parameters in response to detected signal characteristics, the system maintains optimal performance across different transmission speeds
2Power
If the gain of TIAs is increased to amplify weak signals, then the signal amplification is improved, but the input referred noise and frequency response fluctuation increase, worsening signal quality
Solution Approach 1:
Automatic gain control circuits monitor output signal levels and provide feedback to dynamically adjust TIA gain settings. This feedback mechanism ensures that gain is increased only when necessary to maintain adequate signal levels, while automatically reducing gain when signal levels are sufficient, thereby preventing noise and frequency response fluctuations from degrading signal quality
Solution Approach 2:
The patent transitions from static TIA gain settings to dynamic gain control where gain values are continuously adjusted based on real-time signal conditions. This dynamic adaptation allows the system to optimize signal amplification while minimizing noise and distortion effects that worsen with high gain settings
3Stability of the object's composition
If a slow response VOA is used to absorb power fluctuation, then the slow power fluctuation is absorbed, but the fast power fluctuation due to transient cannot be absorbed, reducing transient resistance
Solution Approach 1:
The patent segments the power fluctuation compensation function into two distinct components: a slow-response VOA for absorbing gradual power variations and a fast-response VOA for absorbing rapid transient fluctuations. This segmentation allows each component to be optimized for its specific response time characteristic, with the fast-response VOA providing the necessary transient protection that the slow-response device cannot provide
Solution Approach 2:
The patent combines slow-response and fast-response VOAs in the optical signal path to create a hybrid attenuation system. The slow-response VOA handles gradual power changes while the fast-response VOA handles rapid transients, and their combined effect provides comprehensive power fluctuation absorption across all time scales, resolving the limitation of using only a slow-response device
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 solution effectively reduces gain fluctuations in TIAs, minimizing the impact of frequency response and IRN fluctuations, thereby enhancing signal quality and OSNR resistance, especially at higher baud rates.
Implementation Method 1
an erbium doped fiber amplifier (EDFA) to absorb power fluctuations
Implementation Method 2
a photoelectric convertor configured to convert the signal light attenuated by the attenuator into an electric signal
Data Source
AI summary
An optical apparatus includes an attenuator, a photoelectric convertor, an amplifier, and a processor. the attenuator attenuates signal light. The photoelectric convertor converts the signal light attenuated by the attenuator into an electric signal. The amplifier adjusts a gain of the electric signal. The processor detects a monitor value of a target channel from an output signal of the amplifier, calculates a power value of the target channel from the detected monitor value, calculates a difference value between the power value and a target power value, calculates a attenuation amount by adding a current attenuation amount, which is currently set to the attenuator, to the difference value, controls the gain of the amplifier so that the difference value of the target channel is minimized when the set attenuation amount is less than zero, and sets the attenuation amount to the attenuator when the attenuation amount is zero or more.