Tunable Optical Filter Voltage Control for Loss Stabilization

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Solution Overview

Problem

The use of a dither signal superimposed on the control voltage for a tunable optical filter in optical transmitters leads to fluctuations in the output, degrading transmission characteristics, especially as baud rates increase and data capacity grows.

Innovation Solution

An optical transmitter is designed with a tunable optical filter, a temperature sensor, and a processor that detects optical loss, calculates the control voltage range for minimal loss, adjusts the control voltage based on temperature, and shifts the voltage by a specified amount to maintain optimal transmission characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a dither signal is superimposed on the control voltage for the tunable optical filter, then the transmission frequency can be controlled via feedback system, but the output light will fluctuate and transmission characteristics will be degraded

Engineering Contradiction:

Improvetransmission frequency control precisionVSAvoidoutput stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent extracts and removes the dither signal from the control voltage applied to the tunable optical filter. By eliminating the dither signal component, the feedback control mechanism is simplified while maintaining transmission frequency control precision, thereby preventing output fluctuations and improving transmission characteristics.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using the conventional approach of superimposing a dither signal on the control voltage for feedback control, the patent inverts the approach by applying control voltage without the dither signal. This reversal eliminates the harmful fluctuation effect while preserving the essential frequency control functionality.

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If the baud rate is increased to transmit larger data capacity, then the data transmission capability is improved, but the fluctuation caused by the dither signal becomes more significant and degrades transmission characteristics

Engineering Contradiction:

Improvedata transmission capacityVSAvoidtransmission characteristics

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent removes the dither signal component from the control system, thereby eliminating the source of fluctuation that becomes increasingly problematic at higher baud rates. This extraction allows high-speed data transmission to proceed without the degrading effect of dither-induced output variations.

Inventive Principle:

Principle #2Taking out (Extraction)

3Stability of the object's composition

If feedback control using dither signal is constantly performed, then the transmission frequency can be stabilized, but the output fluctuation increases and transmission characteristics are degraded

Engineering Contradiction:

Improvetransmission frequency stabilityVSAvoidoutput quality

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent extracts and eliminates the dither signal from the feedback control mechanism. By removing this signal component, the system achieves frequency stabilization through alternative means while preventing the output fluctuation and transmission characteristic degradation that result from continuous dither-based feedback control.

Inventive Principle:

Principle #2Taking out (Extraction)

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 stabilizes the output of the optical transmitter, suppresses fluctuations caused by the dither signal, and maintains optimal transmission characteristics even under high baud rates and large data capacities.

Implementation Method 1

a temperature sensor configured to detect a temperature around the tunable optical filter

Methodology Applied

Scientific EffectTemperature detection:

Implementation Method 2

a tunable optical filter provided on an output side of the optical modulator and configured to transmit light of a frequency corresponding to a control voltage

Methodology Applied

Scientific EffectElectro-optic tuning: Electro-Optic Effects

Data Source

PatentUS12328145B2Optical transmitter and control method of tunable optical filter

Publication Date: 2025.06.10 FUJITSU OPTICAL COMPONENTS LTD

AI summary

An optical transmitter includes an optical modulator, a tunable optical filter, a temperature sensor, and a processor. The tunable optical filter is provided on an output side of the optical modulator and transmits light of a frequency corresponding to a control voltage. The temperature sensor detects a temperature around the tunable optical filter. The processor detects an optical loss occurring in the tunable optical filter, calculates a width of a range of the control voltage in which the detected optical loss is smaller than a specified threshold, adjusts the control voltage based on the temperature detected by the temperature sensor, and shifts the control voltage by a specified amount that is larger than zero and smaller than or equal to a half of the calculated width of the range when the optical loss is larger than or equal to the threshold.