Optical Module DBR Laser Modulation Circuit
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Solution Overview
Problem
In PON systems using DBR lasers, the connection of the negative terminal of the laser transmitter and the DBR raster during manufacturing results in a short circuit, preventing modulation of light emitting intensity due to direct current coupling, which limits the ability to control light emission effectively.
Innovation Solution
Incorporating a modulating circuit with capacitors and resistors to control the current flowing through the laser transmitter, allowing for the modulation of light emitting intensity by charging and discharging capacitors, thereby enabling the emission of strong or weak light signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the negative terminal of the laser transmitter and the DBR raster are connected together and grounded during manufacturing, then the manufacturing process is simplified, but the light emitting intensity cannot be modulated due to direct current coupling
Solution Approach 1:
The patent segments the power supply path by introducing separate power supply terminals (positive terminal connected to laser transmitter positive electrode, negative terminal connected to DBR raster negative electrode) that are independent from the signal ground connection. This segmentation allows the manufacturing simplification (grounding both negative terminals together) while preventing DC coupling interference with modulation signals.
Solution Approach 2:
The patent introduces an intermediary power supply circuit structure with dedicated power supply terminals that mediate between the simplified manufacturing grounding approach and the modulation requirement. The power supply terminals act as intermediaries to provide necessary DC bias while allowing AC modulation signals to pass without DC coupling interference.
2Device complexity
If direct current coupling is used in the laser transmitter circuit, then the circuit structure is simplified, but the ability to control light emission intensity is limited
Solution Approach 1:
The patent implements a dynamic modulation capability by separating the static DC bias path (through power supply terminals) from the dynamic AC modulation path (through signal terminals). This allows the circuit to maintain simplicity for DC operation while enabling dynamic control of light emission intensity through differential modulation signals applied to the laser transmitter input terminals.
Solution Approach 2:
The patent enables periodic modulation of light emission by allowing differential signals to be applied to the laser transmitter input terminals while the power supply terminals maintain stable DC bias. This periodic action on top of the DC bias achieves intensity modulation without requiring complex circuit restructuring.
3Device complexity
If the negative terminal of the laser transmitter is connected to the bias pin of the driver chip, then the circuit connection is simplified, but the modulation of light emitting signal is prevented
Solution Approach 1:
The patent extracts the power supply function from the signal ground connection by introducing dedicated power supply terminals. The negative terminal of the laser transmitter is connected to the DBR raster negative electrode through the power supply circuit rather than directly to the driver chip bias pin, separating the power supply path from the modulation signal path and enabling both simplified connection and effective modulation.
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 allows for accurate control of light emitting intensity by using capacitors to store and release charge, effectively modulating the light output of the laser transmitter, overcoming the limitations of direct current coupling and enabling stable current flow for wavelength selection.
Implementation Method 1
a first capacitor, a second capacitor... the first capacitor is connected between the differential signal output positive terminal and the a positive terminal of the laser transmitter; the second capacitor is connected between the differential signal output negative terminal and a negative terminal of the laser transmitter
Data Source
AI summary
An optical module includes a laser transmitter driver chip, a Distributed Bragg reflection (DBR) raster, a laser transmitter, a first resistor, a first capacitor, a second resistor, a second capacitor and a power source. The first resistor is connected between a power source and a differential signal output positive terminal of the laser transmitter; the first capacitor is connected between the differential signal output positive terminal and the a positive terminal of the laser transmitter; the second resistor is connected between the power source and a differential signal output negative terminal of the laser transmitter driver chip; the second capacitor is connected between the differential signal output negative terminal and a negative terminal of the laser transmitter; and the negative terminal of the laser transmitter and a negative terminal of the DBR raster are grounded.