Optical Transmitter Bias Control via Voltage Sweeping
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Solution Overview
Problem
Existing optical transmitters with Mach-Zehnder type modulators face challenges in accurately adjusting bias voltages to maximize the power of optical output signals, leading to inefficiencies in signal modulation and increased power consumption.
Innovation Solution
The optical transmitter employs a configuration with multiple Mach-Zehnder modulators and a phase shifter, utilizing a bias supplying unit to determine optimal bias voltages by sweeping voltage values and detecting the average power of the optical output signal, ensuring that each modulator operates within optimal phase differences to maximize signal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bias voltage is adjusted to maximize optical output signal power, then signal transmission quality is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between bias voltage and optical output signal power in a lookup table during system initialization. When operation begins, the controller retrieves pre-computed optimal bias voltage values based on detected optical power levels, eliminating the need for continuous real-time optimization calculations and reducing power consumption while maintaining signal transmission quality.
2Measurement precision
If multiple bias voltages are swept to find optimal values, then bias voltage accuracy is improved, but adjustment time increases
Solution Approach 1:
The patent performs the time-consuming bias voltage sweeping and optimal value detection during system initialization or calibration phase, storing results in advance. During normal operation, pre-determined optimal bias voltages are applied directly based on operational conditions, achieving both high accuracy and fast response without repeated sweeping.
Solution Approach 2:
The system dynamically adjusts bias voltages based on real-time optical power detection while utilizing pre-computed lookup tables. The controller selects from pre-determined optimal voltage values rather than performing full sweeps, adapting quickly to changing conditions while maintaining measurement precision through the stored calibration data.
3Adaptability or versatility
If Mach-Zehnder modulators are nested to generate modulated optical signals, then modulation capability is improved, but device complexity increases
Solution Approach 1:
The patent implements nested Mach-Zehnder modulators where one modulator is placed within another, enabling complex modulation schemes (such as QAM) by combining the phase modulation capabilities of multiple modulators. The inner modulator processes the optical signal first, then the outer modulator applies additional modulation, achieving high-capacity optical communication with structured complexity management.
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 allows for precise adjustment of bias voltages, maximizing the average power of the optical output signal while minimizing power consumption, thereby enhancing the efficiency and performance of the optical transmitter.
Implementation Method 1
a first inner modulator generating a first modulated optical signal by phase-modulating a first split light in response to a first driving signal, each of the first and second driving signals having a maximum amplitude equal to or smaller than a half-wavelength voltage, the half wavelength voltage being a voltage for changing a phase of light by 180°
Implementation Method 2
a second inner modulator generating a second modulated optical signal by phase-modulating a second split light in response to a second driving signal
Implementation Method 3
an outer modulator generating an optical output signal from the first modulated optical signal and the second modulated optical signal
Data Source
AI summary
An optical transmitter includes a bias supplying unit configured to supply a first bias voltage, a second bias voltage and a third bias voltage to an optical modulator. The bias supplying unit acquires a first voltage value at which an average value of an optical output signal becomes maximum by sweeping the first bias voltage, acquires a second voltage value at which an average value of the optical output signal becomes maximum by sweeping the second bias voltage, and acquires a third voltage value at which an average value of the optical output signal becomes maximum by sweeping the third bias voltage. The bias supplying unit determines a value of the first bias voltage based on the first voltage value, determines a value of the second bias voltage based on the second voltage value, and determines a value of the third bias voltage based on the third voltage value.