Looking to repair a fiber optic cable on a MPS-8033

With the proper equipment (fusion splicer, some experience) this shouldn't be difficult.

However, when you say "kinked 180 degrees", are you sure it's really broken internally? That's the only way it would fail. How tight is the kink? And how did it get kinked? A dead laser would produce the same symptoms, right?

Will also post to sci.optics .

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Neither of which I have... :) ($18K USD. Ouch!)

Well, this instrument was originally missing it's key. An overzealous "tech" [cough, cough] figured he/she could replace the keyswitch, and dis-assembled and removed the front panel of the equipment. In order to do this, they pulled the nicely looped fiber optic cable hard against two of the ties holding the loop against the solder side of the lower circuit board. Now it's come to MY bench for repair... I don't know how I can be sure that it's broken internally, but it is severely deformed and stretched looking. If one were to take a piece of really thin fiber and pull it tight around the radius of a pin's diameter, that would pretty much describe the cable - kinks are in two places about two inches apart. Using an optical power meter tuned to 1550nm I was unable to get any reading, no matter how I tried to straighten the kinks.

Yeah, that's always a possibility. I'd use a scope to check the laser drive, but I've no idea what it would look like as this is my first experience with this type of stuff. The laser does get comfortably warm to the touch after a few minutes and seems to vary thermally depending on the output power I dial in, so I'm ASSuming and hoping that it's still functioning. ;) Given those conditions, would the laser appear to be working?

I don't think that Lucent is making these devices anymore, but the laser looks similar to the device on this website:

Thanks Sam.

Well, maybe $2-3K on eBay. :) At the bottom of the dot.bomb, they were going for under $1K. The experience might cost more though. :)

Doesn't sound good. Especially the stretched part. Fibers will bend around a small radius without breaking, but not a pin diameter.

Likely working but no guarantee.

Someone should be able to point you to a place that has a fusion splicer.

But to do a one-off repair at a reasonable price, may take a friend of a friend....

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Sam Goldwasser wrote in news: snipped-for-privacy@minus.seas.upenn.edu:

At risk of going beyond my ground.....

That laser seems to be accepting a drive correctly, but the output might do one of two things, either it will have died by retroreflection from a large return of light from the damaged point in the fibre, or it will be active, because energy can get out (as heat) without returning to kill the diode.

If this laser is powerful enough, you might be able to detect heat at the damaged point in the fibre. Try taping it to a small Peltier (that has lots of couples in it) and seeing if you see a few millivolts on the Peltier wires when you switch on the laser. Even a 5 mW laser ought to read something consistent if you control for ambient heat and watch a few switching transitions.

The one thing the Peltier test can't tell you is if the laser is low power, and the fibre is reflecting energy back to the diode, it can't tell you if the diode is dead or not, but for power greater than around 50 mW it should be a reliable test.

Sam Goldwasser schrieb:

If you look at the fiber with an infrared viewer and it is the fiber that is is broken and not the laser, you should see a lot of scattered light that emanates from the fiber core at the breaking point.

Cheers, Jürgen

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Might want to try finding the laser diode inside on ebay. I've seen a lot of DFB diodes in that range on there. Other than that you're only option is to get the fiber spliced. It's really not that difficult if you cleanly cleave it and use a fusion splicer. The part that sucks is that one of the pezio positioners on my splicer is fried.

Hopefully, the latter is the case. I had no idea that the light could reflect back into the diode and destroy it... As a side note, the folks at ILX refused to do the splice work, and would only replace the entire laser assembly at a cost of minimum cost of $1500. Nice support!

At this point, I'm a bit hesitant to power up the instrument again. I received a response by email, and may have a contact who can do the work for me, he's stated that if the cable is single mode fiber, it shouldn't be a difficult operation. I'll follow up when it's done and report the outcome for any who are interested. Thanks to everyone who took the time to respond!

I had a broken-fiber problem before on another type of laser (SM fiber). And we had it spliced. Using a fiber fault finder, the engineer located the fault within 2mm. Not bad at all. The resulting fiber is 1" shorter with a little power drop (never calibrated it carefully) from the laser. It costed us only $50.

Out of curiosity (and future reference), where did you have the work done?

Hi Sam,

what has happend with alt.lasers?!!

A. Roithner

"Sam Goldwasser" schrieb im Newsbeitrag news: snipped-for-privacy@m>

beyond

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Nothing. :)

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It failed to lase, you have to adjust the cavity.