Laser Troubleshooting

Industry Best-Practices for Fiber Cleaning and Inspection

A fiber wash cleaning technique or a wet IPA-based fiber wipe process is recommended over a dry cleaning technique (cassette style).

Axsun follows IEC 61300-3-35 for fiber end face cleanliness and geometry. Refer to the below table for more details abotu each zone on the fiber end face.

Zone	Diameter	Allowable non removable defects	Scratches
core	< 8 um	none	none
zone A critical area	< 25 um	none	none
zone B	25-120 um	< 2 um allowed	none > 5 um
		total of 5 sized < 5 um allowed	any
zone C epoxy	120-125 um	any	any
zone D contact area	130-250 um	none > 10 um	none > 10 um
zone E ferrule diameter	250-400 um	none > 30 um	any

OCT Host Helps

Review the information in the following OCT Host tabs: Voltages, Engine TEC, and Errors

No Optical Output

If you are not seeing any beam on an infrared target from the laser output fiber or if you do not measure any optical power using an integrating sphere, please check that the interlock is connected and review the interlock operation.

Incorrect Clock Trace

Please check the oscilloscope settings that are being used to acquire the clock signal. The sampling frequency needs to be at least twice higher than the max frequency of the clock reported on the laser report. The bandwidth of the oscilloscope also needs to be higher than the max clock frequency.

OCT Host Fails to Launch

If OCT Host fails to launch, check that the AxsunOCTControl.dll and and LibUsbDotNet.dll files are present in the same directory as the OCTHost.exe application. If these libraries were inadvertently moved or deleted, reinstall OCT Host.

Poor OCT Image Resolution

This issue can be due to one or more of the following:

• mismatched S/R lengths by an integer multiple of the laser cavity length (send your serial number to Axsun Tech Support to learn about your laser cavity length) resulting in a coherence repeat signal. There will be an infinite number of coherence revivals, but higher order ones in each direction from the zeroth-order (∆z = 0) will become so dispersed that they will eventually fade into the noise. You should be able to identify which is the zeroth-order one by translating your reference arm to the -1st and 1st ones, as they will be noticeably degraded in terms of PSF dispersion and signal level.

• mismatched dispersion (usually a bigger issue for 1060nm versus 1310nm). If you have Integrated engine and are using Hardware Control Tool, refer to the dispersion compensation section for more details. For 1310nm, if the tightest PSF occurs at much higher values of the a2 coefficient (>20), it’s probably likely that you’re not on the zeroth-order coherence revival. At 1310nm, the dispersion compensation coefficients should be near zero for the 0th order.
• mismatch between the total optical length in your OCT interferometer compared to the K-clock interferometer. If this is the case, the signal would get noticeably worse at deeper depths and look nice and narrow at shallow depths. Refer to setting the kclock delay section.