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fiber laser fusion

claya

Cast Iron
Joined
Aug 6, 2006
Location
california
We have a 20W fiber laser (Chinese, what else). The fiber loop inside the laser source is broken in half. Has anyone ever been able to use a fiber fusion welder to repair the fiber for a 20W+ laser? From someone that has actual experience? There are many types of fusion welders. (Arc, co2, plasma) Like some expert advice before we start pursuing this.
 
A Fiber Fusion Splice Kit may run well more than you paid for your 20W. Kits may be available to rent however. Then you would be wise to get some fiber like what is in your unit to practice on as the service-loop length inside your laser is probably too short to play with. Also figure out why your fiber failed in the first place. This could turn out to be like replacing a fuse and wondering why it keeps blowing.

Plan B: 5/32" 7018 at 200A as this is a fabrication forum.
 
A Fiber Fusion Splice Kit may run well more than you paid for your 20W. Kits may be available to rent however. Then you would be wise to get some fiber like what is in your unit to practice on as the service-loop length inside your laser is probably too short to play with. Also figure out why your fiber failed in the first place. This could turn out to be like replacing a fuse and wondering why it keeps blowing.

Plan B: 5/32" 7018 at 200A as this is a fabrication forum.
We have access to a fusion welder for free with some effort. And also rental units. Not sure if the rental welders are sufficient for a 20W application.

We think the fiber broke due to high vibration, or really poor QC on the fiber fabrication. The cladding appeared to be damaged at the failure point.

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The fiber itself is probably good quality and made in the US. If the buffer layer has been abraded through and the clad layer gets nicked then it blows. Lucky you may have found the cause and have access to a kit. You will still need some fiber to practice on and a bottle of buffer. Perhaps from where you are borrowing the fusion splice kit. Plenty of YouTube on the details of fiber splicing. 20 watts does not make it special. It's the same at 1000X this power level.
 
How to we measure the actual core and cladding diameter? It looks like the actual fiber is 125um. It only "appears" to be a two layer fiber. The "jacket" is really soft and "wet" looking, like poorly cured urethane. Literally like macaroni. Chinese low quality tubing.

(I think this is why the fiber failed, rubbing on a groove wall..) We have some similar chinese silicone tubing that just falls apart if you stretch it.

Is it possible the fiber for laser is only two layer? Or is there a super thin cladding layer?

I would like to find some scrap/surplus fiber to practice fusion welding on. Is any 125um fiber good enough? I can find lots of telecom 9um core/125um clad/250um buffer fiber. Is that good enough for practice welding?

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Is the fiber in a fiber laser multi-mode, with a larger diameter core (like 62.5um)? That is what it looks like under magnification Cladding diameter measures 125um.

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Any chance at getting some laser output specifications other than 20W? Is it pulsed or cw? This will assist in understanding what the fiber is. Fiber laser resonators are almost always start single mode, ~10um core. A larger core output fiber then can be bonded on if that’s what the intended use needs. It’s also important to know what the fiber is that failed. Is it clearly the output fiber or does it connect between internal pieces?
Buffer is a hard polymer coating over the clad layer, (like shellac on a transformer winding). The 125um figure sounds to me like that includes the buffer. The 250um must be some jacket material. The jacket may be any old tubing if it’s just protecting the fiber inside the laser package. One of the areas that require practice is the safe stripping of the buffer layer. Kits generally provide a tool but a pocket knife can work just fine. The telecom fiber you mention will get you started. The bond quality is then qualified by some bend and tension tests. We can talk about this when you get a little further along.
 
fiber laser 5/32" 7018 @ 200A

Pretty sure it is pulsed. Chinese fiber engraver, MaxPhotonics source, (Or Raycus, Or IPG) They are all pretty similar.

See the attached photo of the fiber comparison. Upper Left: 125um clad/9.5um core (I think the core is the tiny off-center line). Right: Laser fiber segment, ~62.5um core? You can see the core on the scarf-cut end. Lower left is also the same fiber as upper left, but I can't get a good focus on it. It also looks like the actual laser fiber has a thicker cladding layer so the diameter in slightly more than 125um, maybe why the stripping tool is not working?

The broken section is very near the output, maybe 1 meter or more? I think the cavity is behind a cover that the broken fiber exits from. I have not pulled the cover because the broken fiber is so fragile at times... I can handle it just fine, but then it just snaps at other times. I am VERY concerned about stripping the buffer off. It is a very poor quality chinese silicone and is only 250um in diameter. Yesterday I tried stripping buffer with a stripping tool that is set for 125um, and it snapped the fiber. I am getting good at stripping the single-core telecom fiber I have.

Any chance at getting some laser output specifications other than 20W? Is it pulsed or cw? This will assist in understanding what the fiber is. Fiber laser resonators are almost always start single mode, ~10um core. A larger core output fiber then can be bonded on if that’s what the intended use needs. It’s also important to know what the fiber is that failed. Is it clearly the output fiber or does it connect between internal pieces?
Buffer is a hard polymer coating over the clad layer, (like shellac on a transformer winding). The 125um figure sounds to me like that includes the buffer. The 250um must be some jacket material. The jacket may be any old tubing if it’s just protecting the fiber inside the laser package. One of the areas that require practice is the safe stripping of the buffer layer. Kits generally provide a tool but a pocket knife can work just fine. The telecom fiber you mention will get you started. The bond quality is then qualified by some bend and tension tests. We can talk about this when you get a little further along.
 

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Optical fiber is like fishing line. I mean cut your fingers strong if you try to break it. Yours being fragile says that its optical properties are gone also. No telling how much of your laser is the same. My take is that you should find something else to work on.
 








 
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