Optical Signal Transmitter Bias Control via Dither Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical signal transmitters face challenges in accurately controlling the phase modulation and bias voltage of MZI-type optical modulators, particularly in DQPSK systems, due to poor detection accuracy and the difficulty in determining the direction of divergence from the optimal phase value π/2, which affects the quality of the optical phase shifter and phase modulation accuracy.
Innovation Solution
The implementation of an optical signal transmitter with two phase modulating portions, a phase shifter that displaces carrier phases by π/2, and a dither signal adding and detecting system to asymmetrically dither the data bias voltages, allowing for precise control of the orthogonal bias voltage and phase modulation, enabling high-accuracy bias control and phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bias control methods are used for the optical phase shifter, then the adjustment is extremely severe and requires manual intervention, but the measurement precision and reliability of phase modulation are insufficient
Solution Approach 1:
The patent implements automatic feedback control by detecting the optical power of the DQPSK signal and comparing it with a reference value. The control unit adjusts the orthogonal bias voltage based on the detection result to maintain optimal phase modulation, eliminating manual adjustment and improving both precision and reducing operational complexity
Solution Approach 2:
The system performs self-adjustment of the orthogonal bias voltage through automatic detection and control. The optical phase shifter automatically corrects its own bias drift by using the detected optical power information to regulate the bias voltage, achieving self-service operation without external intervention
2Reliability
If manual adjustment of the orthogonal bias voltage is performed, then some control is achieved, but the direction of divergence from the optimal phase value cannot be determined
Solution Approach 1:
The detection unit provides feedback information about the optical power level, which contains directional information about bias drift. The control unit uses this feedback to determine whether the bias voltage has deviated above or below the optimal value and adjusts accordingly, preserving direction information that would otherwise be lost
3Measurement precision
If the orthogonal bias voltage is not accurately controlled, then the optical quality of the DQPSK signal deteriorates, but achieving accurate control requires extreme precision in phase shifter adjustment
Solution Approach 1:
The system continuously monitors the optical power of the DQPSK signal and uses this information to automatically adjust the orthogonal bias voltage. This feedback mechanism maintains the bias voltage at the optimal value, ensuring high optical quality without requiring extreme manual adjustment precision
Solution Approach 2:
The patent replaces manual mechanical adjustment of the bias voltage with automatic electronic control. The control unit electronically regulates the orthogonal bias voltage based on optical power detection, substituting the mechanical adjustment process with an automated electronic system that achieves superior precision and stability
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 high-accuracy bias control and phase modulation by clearly indicating the direction of bias voltage shift from the optimal value, resulting in improved optical waveform quality and phase modulation accuracy.
Implementation Method 1
an optical phase shifter which displaces by π/2 carrier phases of two output lights from the phase modulating portions
Implementation Method 2
a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides
Implementation Method 3
a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other
Data Source
AI summary
An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by π/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage Vπ of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonal bias electrode portion which supplies an orthogonal bias voltage to the phase shifter; a data bias power supply portion that adjusts delay times in the two phase modulating portions by applying the data bias voltages to the data bias electrode portion; an orthogonal bias power supply portion that adjusts a delay amount relative to a light output from at least one of the two phase modulating portions by applying the orthogonal bias voltage to the orthogonal bias electrode portion; a dither signal adding portion that adds a dither signal to at most three of the four data bias voltages; a dither detecting portion which detects a wave that is n-times a dither component from an output of the multiplexing portion (where n is an integer equal to or greater than one); and an orthogonal bias control portion which feeds back a detection result of the dither detecting portion to the orthogonal bias power supply portion. The orthogonal bias power supply portion adjusts the delay amount relative to the light output from at least one of the two phase modulating portions by controlling the orthogonal bias voltage to be applied to the orthogonal bias electrode portion based on feedback from the orthogonal bias control portion.