Polyphase Pump Diode Control for Fiber Laser Thermal Reliability
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Solution Overview
Problem
LiDAR systems using fiber lasers at 1550 nm wavelength face challenges with low wall plug efficiency (WPE) and pump diode reliability, which can be addressed by improving the redundancy and operation of pump lasers.
Innovation Solution
Implementing multiple pump lasers in a polyphase fashion at a single pumping stage, with controllers generating current pulses of different phases to ensure no timing overlap and monitoring junction temperatures for selective operation, thereby enhancing reliability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple pump diodes are added to improve reliability, then redundancy increases, but device complexity increases
Solution Approach 1:
The pump laser operation is segmented into multiple phases where different pump diodes are activated at different time intervals. The controller divides the pumping duty into sequential segments, activating one pump diode at a time in a polyphase arrangement, which reduces simultaneous thermal loading and extends individual diode lifespan while maintaining overall system reliability
Solution Approach 2:
The system implements periodic activation of pump diodes with phase-shifted timing. Each pump diode operates in periodic cycles with duty cycles less than 100%, and the activation periods are staggered across multiple diodes. This periodic operation allows thermal management and extends diode life while maintaining continuous pumping capability through the array
2Power
If multiple pump lasers are operated simultaneously, then pumping power increases, but thermal management becomes difficult
Solution Approach 1:
Each pump laser is operated in periodic pulses with duty cycles less than 100%, allowing thermal dissipation between pulses. The periodic operation prevents continuous thermal accumulation while maintaining average pumping power through high peak powers during active phases
Solution Approach 2:
The total pumping power is segmented across multiple pump lasers that operate sequentially rather than simultaneously at full power. Each laser handles a portion of the total power requirement, and their staggered operation distributes thermal load across time and space, making thermal management feasible
3Duration of action of moving object
If current pulses are overlapped, then continuous pumping is achieved, but thermal accumulation increases
Solution Approach 1:
Current pulses are designed with periodic timing where each pump laser receives pulsed current with gaps between pulses. The duty cycle is kept below 100% to ensure thermal relaxation periods, preventing thermal accumulation while maintaining continuous overall pumping through the polyphase array
Solution Approach 2:
The system transitions from temporal overlap (simultaneous pulsing) to spatial distribution (polyphase arrangement across multiple lasers). By distributing pump lasers in space with phase-shifted timing, the system achieves continuous pumping coverage across the gain medium while each individual laser experiences periodic operation with thermal management
Data Source
AI summary
A light detection and ranging (LiDAR) system in which multiple pump lasers are operated in polyphase fashion at a single pumping stage is disclosed. In some embodiments, the multiple pump lasers are operated by controllers that generate current pulses through the multiple pump lasers. The current pulses powering at least two of the pumping lasers have different phases. In some embodiments, the phase differences are such that there is no timing overlap in the current pulses through the pump lasers. In some embodiments, the phase difference between successive current pulses is greater than the pulse width such that the sum of the duty cycles of all the current pulses is less than one. In some embodiments, junction temperatures of pump lasers are monitored and temperature information from the monitoring is used to dynamically select which pump laser will be utilized at a given time. Further details of these and other embodiments are disclosed herein.