SOA Integrated EA-DFB Optical Transmitter with Dual Light Detectors
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Solution Overview
Problem
The conventional method of automatic power control (APC) for semiconductor lasers with integrated semiconductor optical amplifiers (SOA) fails to provide reliable feedback, as it cannot distinguish between deteriorations in the DFB laser and SOA parts, leading to ineffective intensity monitoring and control.
Innovation Solution
An optical transmitter with an SOA integrated EA-DFB laser, including a first light detector for monitoring the signal light beam from the SOA and a second light detector for monitoring the light beam from the DFB laser without passing through the SOA, allowing for separate control of drive currents and distinguishing between DFB and SOA deteriorations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light detector is used to monitor the output light beam from the SOA integrated EA-DFB laser, then the device complexity is reduced, but the ability to distinguish between DFB laser deterioration and SOA deterioration is lost
Solution Approach 1:
The patent divides the monitoring function into two separate light detectors: one monitors the light beam from the DFB laser before the SOA, and the other monitors the output light beam from the SOA. This segmentation allows independent detection of each component's performance, enabling precise identification of whether deterioration originates from the DFB laser or the SOA.
2Device complexity
If conventional APC method is used with SOA integrated EA-DFB laser, then the light intensity monitoring is simplified, but the feedback reliability is compromised due to inability to distinguish component deteriorations
Solution Approach 1:
The patent implements a dual-feedback mechanism where the first light detector provides feedback on DFB laser performance and the second light detector provides feedback on overall system output. By comparing the readings from both detectors, the system can determine which component is deteriorating and adjust the drive current accordingly, ensuring reliable APC feedback control.
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 reliable APC feedback and distinguishes between semiconductor laser and SOA deteriorations, ensuring effective light intensity monitoring and control.
Implementation Method 1
electro absorption (EA) modulators utilizing the electro absorption effect
Implementation Method 2
changes in light intensity can be monitored by a light detector
Data Source
AI summary
The present invention provides an optical transmitter and a light intensity monitoring method that provide reliable APC feedback for a semiconductor laser equipped with an SOA. The optical transmitter includes an SOA integrated EA-DFB having a DFB laser, an EA modulator connected to the DFB laser, and an SOA connected to the EA modulator. In the structure of the optical transmitter, a light detector part is disposed forward of the output end side of an SOA part. The light detector part changes part of an output light beam from the SOA part into an electric current and detects light, while guiding the remaining part of the output light beam to a waveguide. With the light detector part disposed forward for the SOA part, it is possible to feed back the output result from the SOA part. Hence, good APC is possible.