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Thread: Learning about lasers over fiber

  1. #1
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    Default Learning about lasers over fiber

    Hi Everyone,

    Decided to turn this into a thread so whatever information is linked/shared/etc that others can benefit too.
    Long story short: I never delved too deep into shooting lasers over fiber as I never had a real need so there was no incentive to learn. I have only 1 laser with an SMA fiber attachment (a cheap necsel I got over a year ago) but no fiber or anything. Seeing even some dpss builds using a fiber to combine a lot of IR laser sources and more eventually caught my interest and due to covid time is more abudant.. so time to learn I'd say.

    So here are some of my questions:

    - What is a good way of learning to launch a laser over fiber? Is there an affordable (used?) set that is being sold to launch a laser over a fiber? I assume parts needed are: A coupler with a focus to narrow the beam to the fiber, the fiber and a coupler to focus back onto the fiber to get the beam back?

    - Other then the losses caused by diffraction what is the disadvantage of fiber launching a laser diode?
    - When is a multimode fiber used other then a single mode fiber for launching lasers? (or is it always single mode?)
    - How do you determine the width of the fiber? I assume you would want the smallest possible to get the most narrow ending beam?
    - I see some ir diode blocks sometimes using a fiber to pull multiple sources closer together to provide a strong pump source for laser.. can I just focus in multiple lasers coming in from different angles at a narrow fiber to bring beams really close? can this process be done for multiple wavelengths at once into one fiber even when they come in at other angles??

    To me this was a good indicator of what components are used to do the job: https://www.dragonlasers.com/xc_old/...ment_Guide.pdf
    Last edited by masterpj; 08-17-2020 at 09:03.

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    ... I've started with the NIR-pumping diodes, salvaged from broken fiber-lasers -- here it's mostly combining several 9W or 10W diodes in a housing into a 105µm-multimode-fiber, as shown in the attached image (25W-diode from IPG) ...

    *** EDIT *** -- here you can find some more fiber-coupled diodes: https://reprap.org/wiki/Laser_Cutter_Notes

    Viktor
    Attached Thumbnails Attached Thumbnails 25Watt-fiber-coupling.jpg  

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    Quote Originally Posted by VDX View Post
    ... I've started with the NIR-pumping diodes, salvaged from broken fiber-lasers -- here it's mostly combining several 9W or 10W diodes in a housing into a 105µm-multimode-fiber, as shown in the attached image (25W-diode from IPG) ...

    *** EDIT *** -- here you can find some more fiber-coupled diodes: https://reprap.org/wiki/Laser_Cutter_Notes

    Viktor


    I'll shoot you some pics tonight. What we use in the field is a bit different then the cutting industry uses. Basically ruggedized version of the scientific lab 3 axis launcher stuff.

    Steve
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    ... I too have some 2/3/4-axis adjustable fiber-couplers for fibers and other laser-related stuff from older scientific or show-laser gears ... but this are pretty "individual" sets, some "one off" and only built for a single/specific project ...

    Viktor
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    Quote Originally Posted by VDX View Post
    ... I've started with the NIR-pumping diodes, salvaged from broken fiber-lasers -- here it's mostly combining several 9W or 10W diodes in a housing into a 105µm-multimode-fiber, as shown in the attached image (25W-diode from IPG) ...

    *** EDIT *** -- here you can find some more fiber-coupled diodes: https://reprap.org/wiki/Laser_Cutter_Notes

    Viktor
    This looks super cool! Would it all be single mode fibers here?
    I know in fiber optic data pulls a multi mode fiber can handle much more then single mode in terms of transmission speed/capacity but actually as in putting a diode array over a fiber or so I don't understand what is required!

    I'll see if I can purchase some broken fiber lasers to learn it a bit more by taking things apart.

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    ... no singlemodes! (maybe the small 1Watt-NIR-diode with a 50µm fiber - first in the collection images) -- normally all diodes above 1Watt power and fiber diameters at and above 105µm are multimode ...

    Viktor
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    Quote Originally Posted by VDX View Post
    ... no singlemodes! (maybe the small 1Watt-NIR-diode with a 50µm fiber - first in the collection images) -- normally all diodes above 1Watt power and fiber diameters at and above 105µm are multimode ...

    Viktor
    roger so mostly multimode! So how do you determine the diameter of your fiber when you start working? Say you want to fire multiple beams down a fiber.

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    ... in the image of the 25W-diode 3 "beams" of 9W-diodes are collimated to "flat lines", stacked together to a "quadrate" and focussed/injected into the 105µm fiber.

    The same is done with the 200Watt-diode, attached here (where the B-card accidentally caught fire) -- except, here there are 35(!) beams, precollimated to 7 "5x-lines", and then "stacked" to a 6x6mm quadrate, what's scattred across some mirrors and last focussed/injected into a 0,2mm fiber

    Viktor
    Attached Thumbnails Attached Thumbnails Rofin-200W-Dioden - 3A-Karte.jpg  

    Rofin-200W-Dioden - 7A-Karte.jpg  

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    ... here some images showing other collimated (or expanded) beam structures of such "stacked" beams -- in the middle the "35-beams" from the 200W-diode and a "macro" methode, focussing 6x blue diodes onto a 0,3mm spot, what could be directly "injected" into a 0,3 or 0,4mm fiber.

    The 2 last "red" images shows fiber-bundles, as they are commonly used in FSMA-connectors with a 0,4mm or 0,8mm output diameter, what's then transmitted by 0,4mm, 0,6mm or 0,8mm fibers ...

    Viktor
    Attached Thumbnails Attached Thumbnails 5Watt-Diode-Fernbild3.jpg  

    Diodenmodul 61x.jpg  

    8A-unfokussiert.jpg  

    500W-Diode offen.jpg  

    Ohne Beam-Guide2.jpg  

    6xKopf1.jpg  

    Last edited by VDX; 08-17-2020 at 13:55.
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    This is awsome! Really admire this kind of stuff. I really want to learn this to perhaps learn to tame a necsel or sorts using a fiber to bring the array together.. I noticed with those 808nm (i assume they are 808nm) arrays that you are using what appears to be regullar mirrors or even dichroics where you shine one beam off one side but another beam passes through as well rather then going past it (which I think is maybe the drawing not being accurate before? I assume its all knife edging here then somehow bringing it down to a fiber end?.. (I never really delved into fiber so this is a new area for me).

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