Extreme Fiber Coupled Laser Diode Power Loss

In summary: The fiber jumper was not making a good connection and was causing the power to drop.In summary, a fiber coupled laser diode might have lost power due to a bad connection between the fiber and the power meter.
  • #1
daniel1211
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What could cause a laser source with fiber coupled laser diodes to have extreme loss of power? The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW.

During some troubleshooting I noticed that one of my optical channels had a loss of -13dB (95%) so I cleaned the fibers to make sure there was no blockage but when I remeasured I was only given a small gain of maybe +30dB (0.1%). I decided to spot check other channels and noticed that they also had significantly dropped in power.

I thought that perhaps the sources had been on for too long and that perhaps the diodes where being affected by heat, I shut everything down and proceeded to check the systems the next day after they had cooled but unfortunately the output was still extremely low.
 
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  • #2
daniel1211 said:
The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW.
They appear to be close to the specified output. What output do you expect from a 60mW diode?

daniel1211 said:
During some troubleshooting I noticed that one of my optical channels had a loss of -13dB (95%) so I cleaned the fibers to make sure there was no blockage but when I remeasured I was only given a small gain of maybe +30dB (0.1%).
I do not understand your dB to % conversions. What do the % represent?
How can +30dB be a small gain when it represents 1000 times as much power?
 
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  • #3
daniel1211 said:
What could cause a laser source with fiber coupled laser diodes to have extreme loss of power? The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW.

During some troubleshooting I noticed that one of my optical channels had a loss of -13dB (95%) so I cleaned the fibers to make sure there was no blockage but when I remeasured I was only given a small gain of maybe +30dB (0.1%). I decided to spot check other channels and noticed that they also had significantly dropped in power.
I'm going to agree with Baluncore

your misunderstanding / misinterpretation of the figures is leading you to believe there is a problem when one doesn't existDave
 
  • #4
I was using a guide that was helping me convert dB to percentage, I must of made a mistake.

Either way I still don't understand why my source channels are outputting less then 10mW when after considering loss they should be outputting around 50mW and are rated at 60mW.

For example when I first measured one channels output power I was given 54mW yet when I recently did a spot check on the same channel I measured 4mW.

Would a source that has been powered on for a day cause the diode to lose power?

Could noise cause this problem?
 
  • #5
Powering off for a time should not make a difference. If it does then that is an important clue. Monitor the temperature of the module.

It might be matching of the fibre to your power meter that is a problem. How is the connection made ?

Some laser diodes have an optical power monitor built onto the back of the diode. Are you able to use that sensor output to independently monitor the laser diode output before the fibre ?

I believe we can identify the problem if we are given a little more information. It would help if we knew the make and model of the fibre coupled laser diode module, and the make and model of the power meter you are using.
 
  • #6
This is the link to the laser diode spec sheet
http://www.blueskyresearch.com/fileupload/FiberTec_II_02-05-2015.pdf

The fiber coupled laser diode uses a FC connector
The fiber jumper used to connect to the power meter is ST to FC

The source that we are using is a recent custom build and the sensor is supposed to be part of the next build

I am using a Thorlab PM200 power meter
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5386
[PLAIN]https://www.thorlabs.com/dra...3-5056-0103-79616E9683171250/PM200-Manual.pdf[/PLAIN]
as well as a Thorlab Photodiode Amplifier
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1003
 
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  • #7
It seems that the issue was due to the bulkhead connector.
 

FAQ: Extreme Fiber Coupled Laser Diode Power Loss

1. What is extreme fiber coupled laser diode power loss?

Extreme fiber coupled laser diode power loss refers to the amount of power that is lost when a laser diode is coupled with a fiber optic cable. This is typically caused by inefficiencies in the coupling process, such as misalignment or poor quality connectors.

2. How is extreme fiber coupled laser diode power loss measured?

Extreme fiber coupled laser diode power loss is typically measured in decibels (dB). This measurement takes into account both the input power and the output power of the system to determine the amount of power that is lost in the coupling process.

3. What factors contribute to extreme fiber coupled laser diode power loss?

There are several factors that can contribute to extreme fiber coupled laser diode power loss, including misalignment of the laser diode and fiber optic cable, poor quality connectors, and contamination or damage to the optical surfaces.

4. How can extreme fiber coupled laser diode power loss be minimized?

Extreme fiber coupled laser diode power loss can be minimized by ensuring proper alignment of the laser diode and fiber optic cable, using high-quality connectors, and regularly cleaning and inspecting the optical surfaces for any damage or contamination.

5. What are the potential consequences of extreme fiber coupled laser diode power loss?

The consequences of extreme fiber coupled laser diode power loss can include reduced efficiency and performance of the laser system, increased heat dissipation, and potential damage to the laser diode. This can lead to decreased reliability and lifespan of the system.

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