Optical Transmitter Bias Control for Arbitrary Waveforms
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Solution Overview
Problem
Conventional bias control methods are inadequate for applications generating arbitrary optical waveforms, such as OFDM signals, multilevel modulated signals, and pre-equalization signals, as they fail to effectively control the bias to the Null point, leading to unstable optical waveforms and potential disconnection issues.
Innovation Solution
An optical transmitter that performs bias control based on the intensity of output light detected by a light intensity detection means and calculates the average modulation degree of the data sequence, allowing for precise control of the bias to the Null point, even in dynamic drive waveform scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional bias control methods are used for binary signals, then the bias can be controlled to the Null point, but the method becomes inapplicable to arbitrary optical waveforms including analog waveforms such as OFDM signals, multilevel modulated signals, and pre-equalization signals
Solution Approach 1:
The patent changes the control parameter from binary signal levels to average modulation degree calculation. By calculating the average modulation degree from the drive signal and using it to dynamically adjust the bias control target, the system adapts to arbitrary waveforms including OFDM and multilevel modulated signals while maintaining reliable bias control to the Null point
Solution Approach 2:
The patent introduces feedback by calculating the average modulation degree from the actual drive signal and using this information to adjust the bias control. This closed-loop approach allows the system to adapt to different waveform types and modulation degrees, enabling reliable bias control across diverse applications
2Adaptability or versatility
If the bias voltage is not controlled to the Null point, then the optical waveform characteristics can change, but the optical signal transmission becomes unstable
Solution Approach 1:
The patent dynamically adjusts the bias control target based on the calculated average modulation degree. By changing the target bias voltage according to the modulation degree parameter, the system maintains optimal extinction ratio and Null point control even when waveform characteristics change, ensuring both adaptability and stability
3Ease of operation
If bias control is performed without considering modulation degree, then the control is simple, but the bias cannot converge to the Null point in applications with changing modulation degrees
Solution Approach 1:
The patent replaces complex manual bias adjustment mechanisms with an automated calculation system that computes average modulation degree from the drive signal. This substitution maintains operational simplicity while achieving precise bias convergence to the Null point through algorithmic control based on actual signal characteristics
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
Enables stable bias control for arbitrary optical waveforms, ensuring that the bias converges to the Null point, thereby maintaining the desired optical waveform and preventing disconnection, even in applications with changing modulation degrees.
Implementation Method 1
intensity of output light of the optical modulator detected by the light intensity detection means
Data Source
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AI summary
Provided is an optical transmitter for generating an arbitrary optical waveform including an analog optical waveform, which is capable of controlling a bias to a Null point easily. The optical transmitter for modulating light from a light source by an optical modulator with use of a data sequence being an electric signal, to thereby generate the arbitrary optical waveform, includes: light intensity detection means for detecting intensity of output light of the optical modulator; data signal generation means for generating the data sequence; average modulation degree calculation means for calculating an average modulation degree of the data sequence based on the data sequence; and bias control means for performing bias control on the optical modulator based on the intensity of the output light detected by the light intensity detection means and the average modulation degree of the data sequence calculated by the average modulation degree calculation means.