Optical Receiver Bias Voltage Control for Crosstalk Reduction
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Solution Overview
Problem
In high-speed optical communication systems, the integration of multiple channels in a single package leads to crosstalk issues, which degrade reception sensitivity and increase error rates due to amplitude variability between channels, making it challenging to maintain the desired optical input power range.
Innovation Solution
An optical receiver design that includes a demultiplexer, photoelectric converters, and a control circuit to monitor and adjust the bias voltage applied to avalanche photodiodes (APDs) to minimize amplitude differences between channels, thereby reducing crosstalk and maintaining the signal-to-noise ratio within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple channels are integrated in one package for downscaling, then device size is reduced, but crosstalk between channels increases and amplitude variability worsens
Solution Approach 1:
The patent applies local quality by individually adjusting the bias voltage for each channel's APD based on its specific amplitude characteristic. The control circuit monitors and controls the bias voltage applied to each light receiver separately, allowing localized optimization of amplitude characteristics for each channel while they are integrated in the same package. This resolves the crosstalk issue by equalizing amplitude characteristics locally at each channel rather than using a uniform approach.
2Reliability
If APD is used to amplify photocurrent for high photosensitivity, then reception sensitivity is improved, but amplitude variability between channels increases
Solution Approach 1:
The patent implements feedback control by having the control circuit continuously monitor the amplitude characteristic of each channel through the monitor circuit and adjust the bias voltage applied to each APD accordingly. This closed-loop feedback mechanism ensures that despite variations in APD characteristics, the amplitude characteristics across all channels are equalized, maintaining both high reception sensitivity and consistent amplitude composition.
Solution Approach 2:
The patent changes the operating parameter (bias voltage) of each APD individually to optimize performance. By adjusting the bias voltage applied to each light receiver based on its specific characteristics, the system equalizes the amplitude characteristics across channels while maintaining the high photosensitivity provided by the APD's internal gain mechanism.
3Device complexity
If fixed bias voltage is applied to all channels, then device complexity is reduced, but amplitude characteristic variability increases
Solution Approach 1:
The patent transitions from a static fixed bias voltage approach to a dynamic control system that adjusts bias voltages based on real-time monitoring of amplitude characteristics. The control circuit dynamically modifies the bias voltage applied to each channel to equalize amplitude characteristics, making the system adaptable to variations in APD performance while maintaining relatively simple overall device architecture.
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 effectively reduces crosstalk between channels, maintaining the error rate within standards and optimizing the signal-to-noise ratio by equalizing photocurrent amplitudes and adjusting bias voltages based on temperature and current monitor values, leading to improved data accuracy and reduced noise interference.
Implementation Method 1
a photoelectric converter having a number of light receivers corresponding to the plurality of channels, the photoelectric converter being configured to convert an optical signal into an electric signal for each channel
Implementation Method 2
APD amplifies photocurrent by application of reverse bias (voltage) to achieve high photosensitivity
Data Source
AI summary
An optical receiver includes a demultiplexer configured to demultiplex, for each channel, optical signals input through a plurality of channels, a photoelectric converter having a number of light receivers corresponding to the plurality of channels, the photoelectric converter being configured to convert an optical signal into an electric signal for each channel, a monitor circuit configured to monitor, for each channel, an amplitude characteristic of the optical signal converted into the electric signal by the photoelectric converter, and a control circuit configured to control, based on a monitored result of the monitor circuit, a bias voltage to be applied to the light receiver such that an amount of variability in the amplitude characteristic between the channels is minimum or falls within a predetermined range.