5.5 Supplemental Testing: The Second Vibration Test Using the Thin Bracket

The second vibration test was run to see if any catastrophic failures would occur due to a less than stable mounting bracket. It was run in exactly the same way as the first test except that the original bracket, described in the test plan (Figure 10), was used. Figure 19 shows the vibration profile extended to the bracket when using the same test conditions as those used in the first vibration test. The resonant peaks and resulting increase in total force extended to the connector resulted from the physical design of the bracket; namely the thin sides, the height and the lack of side support. The total force of this test was 37.66 Grms.

Figure 19. Vibration Profile for the Thin Bracket

No trigger events were found during the first five runs (X1, X2, Y1, Y2, Z1). During the last z-axis test (Z2), several trigger events (momentary loss in excess of 0.5 dB) occurred for channel 43 during the first minute of the six minute test. Data for the second vibration test is provide in appendix A. No backing-off from the connector or backshell was noted and there was no disruption to the torque striping.

Figure 20 compares optical power throughput measurements taken before and after the second vibration test (-11.5 dBm represents the maximum loss rating and -7.95 dBm the launch power). Channel 43 experienced the most degradation (1.2 dB) due to the second vibration test. Figure 20 data was taken before the termini were visually examined and cleaned.

Figure 20

After the second vibration test, the termini were removed and photographed at 255X magnification before and after cleaning. Table 6 lists the results of visual observations incuding contamination found before the termini were cleaned compared to the post Vibration (1) photographs.

Although some contamination was observed on most of the fiber end faces, the amount and particle sizes were significantly smaller than noted after the first vibration test. With the exception of the rough spots noted on the channel 42 pin and socket, no new features evolved. No large contamination or defect was found on either the pin or socket of channel 43 that could explain the trigger events noted during the last vibration run or the increase in loss (1.2 dB) measured after the test.

Table 6. Visual Observations Following the Second Vibration Test

Terminus   Contamination Noted Before Cleaning   	New Features Found After Cleaning  

   41P    none                                  	none                                

   41R    residue smear (material unknown)      	four large scratches                

   42P    very small amount of particulate      	large rough area at cladding/core   
          contamination (may be metal)          	interface (half the total core size)                               

   42R    large amount of small metal           	large rough area at cladding/core   
          particles in the range of 4 m         	interface (half the total core      
          square, most much smaller             	size)                               

   43P    very small particles (may be metal)   	none                                

   43R    residue smear (material unknown)      	none                                

   44P    small amount of smear material        	none                                

   44R    very small particles (may be metal)   	none