PLC Optical Multiplexing Circuit for LD Degradation Monitoring
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Solution Overview
Problem
The existing optical multiplexing systems face challenges in accurately monitoring light of multiple wavelengths and tolerating degradation of laser diodes (LDs) in light sources, particularly due to higher power density and energy from visible to ultraviolet light, which leads to reduced life expectancy and increased manufacturing costs.
Innovation Solution
An optical multiplexing circuit using a planar lightwave circuit (PLC) with multiple sets of multiplexers and branching units on a substrate, allowing for accurate monitoring and switching of LDs to extend their life expectancy, while maintaining the same manufacturing process and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk optical components (lenses, dichroic mirrors, half mirrors) are used for light multiplexing and monitoring, then light multiplexing and white balance monitoring can be achieved, but the device size increases and manufacturing cost increases
Solution Approach 1:
The patent integrates multiple bulk optical components (lenses, dichroic mirrors, half mirrors) and photodiodes into a single planar lightwave circuit (PLC) chip. The PLC technology allows waveguides, couplers, and detectors to be fabricated on the same substrate, merging functions that previously required separate components into one integrated device, thereby reducing overall size while maintaining multiplexing and monitoring capabilities
Solution Approach 2:
The PLC chip serves multiple functions simultaneously: it multiplexes light from multiple wavelengths, separates wavelengths for individual monitoring, and integrates detectors for white balance adjustment. This multi-functional integration eliminates the need for separate bulk optical components and reduces device complexity
2Reliability
If multiple LDs of the same color are prepared to tolerate degradation, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
Multiple LDs of the same color are integrated onto a single PLC chip with their respective waveguides and couplers. The PLC structure provides built-in optical switching capability through directional couplers, allowing seamless switching between redundant LDs without requiring external mechanical switches or complex control mechanisms, thus reducing overall device complexity
Solution Approach 2:
The patent implements monitoring photodiodes that continuously detect light output from each LD. When degradation is detected in an active LD, the system uses the monitoring signals to automatically switch to a standby LD, providing feedback-based reliability without complex manual intervention
3Illumination intensity
If visible light LDs are used for RGB light source, then color reproducibility and light emission efficiency are improved, but life expectancy decreases due to higher power density and energy
Solution Approach 1:
The patent prepares standby LDs in advance for each color channel and implements a switching mechanism that activates before complete failure occurs. Monitoring photodiodes detect early signs of degradation, allowing the system to switch to redundant LDs proactively, thus cushioning against the reduced life expectancy of high-power visible light LDs
Solution Approach 2:
When an LD degrades or fails, the system switches to a standby LD and can potentially recover or replace the degraded LD later. The PLC structure allows individual LD replacement without affecting other channels, enabling maintenance and recovery operations that extend overall system life
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 enables accurate monitoring and adjustment of white balance, extends the life expectancy of LDs by allowing for easy switching of degraded LDs, and maintains the manufacturing cost and process complexity of existing systems.
Implementation Method 1
By using mode multiplexing, light of the same wavelength can be multiplexed in different modes
Implementation Method 2
white balance is adjusted by monitoring the divided light of each color by using photodiodes (PDs)
Data Source
AI summary
To provide an optical multiplexing circuit that can accurately monitor light of a plurality of wavelengths, and that can tolerate degradation of LDs. An optical multiplexing circuit includes m sets of multiplexers configured to multiplex light output from n connection waveguides being a plurality of connection waveguides wherein a multiplexing unit configured to input and multiplex light output from the m sets of the multiplexers from m input waveguides, an output waveguide configured to output light multiplexed by the multiplexing unit, and n×m or m branching units being inserted into n×m connection waveguides of the plurality of connection waveguides or the m input waveguides are provided on a same substrate.