# Presentation: 406703

## 5A AOE-0588 SSQ 21654 Fiber Optic Cable Anomaly - Risk Assessment Model

**Boeing - HB**

**January 18, 2000**

**Pete Mueggler**
**(714) 896-4977**

**Notes:**
This template is intended to provide guidance for preparing to present information to ISSP control panels and control boards pertaining to solutions to problems that may exist in the program.
The format is structured to present:
a clear definition of the problem, 
who/what is impacted by the problem, 
options to resolve the problem, 
how implementing the options will improve the situation, 
and what is expected from the control panel or board.

## OBJECTIVES:  Quantify the risk for the ISS Applications

***FIBER OPTICS CABLE ANALYSIS***

- PROBLEM:  **SSQ 21654 Fiber Optic Cable has been found to contain anomalies **
**not previously identified.  No test other than “normal” ISS acceptance testing has **
**been performed on many installed ISS cables.**

- OBJECTIVES:  Quantify the risk for the ISS Applications

##    ‘As installed’ fiber optics cables

***FIBER OPTICS CABLE ANALYSIS***

-    ‘As installed’ fiber optics cables
-    System
-    Functions

- SYSTEM DESCRIPTION

## ANALYSIS

***FIBER OPTICS CABLE ANALYSIS***

- Assumptions
- Probability Model
- Probability Analysis Method
- Hardware Tested
- Defects
-     Data
-     Defect rates analysis
- Detection
-     Strength data
-     Strength distribution / percentiles
- Transmission loss
-     Transmission loss data
-     Transmission loss distribution / percentiles
- Other potential failure causes
- Results
- Conclusions & Recommendations

## ASSUMPTIONS / GROUNDRULES

***FIBER OPTICS CABLE ANALYSIS***

- DEFECTS
-   Defects are randomly distributed along cable length
-   Defect rate is constant for each lot
- INSTALLATION & CHECKOUT
-   At least 0.5 lbs of tension is applied during installation of each cable
-   Defects with strength < 0.5 lbs are detected
- OPTICAL PERFORMANCE
-   Transmission loss of < 1.5 dB per defect is acceptable performance

## PROBABILITY MODEL

***FIBER OPTICS CABLE ANALYSIS***

## Prd (L)  =  Probability of a defect in a cable of length L

***FIBER OPTICS CABLE ANALYSIS***

- PROBABILITY ANALYSIS METHOD

- Pr*d *(L)  =  Probability of a defect in a cable of length L
-    For  *d*  = constant, follows Exponential probability density function
-    Pr*d *(L)  =  1  -  exp [ - *d* * L ]

*d*  =  defect rate = constant
-    calculated from defect data based on the Chi-Square Pdf

*d*  =    { ****; 2(r+1)  }  /  2L

- L  =  total cable length tested
- r   =  number of defects found
-   =  level of significance  ( = 1 - confidence level)

## HARDWARE TESTED

***FIBER OPTICS CABLE ANALYSIS***

## DEFECT RATE ANALYSIS

***FIBER OPTICS CABLE ANALYSIS***

## DEFECT DETECTION:  STRENGTH DATA

***FIBER OPTICS CABLE ANALYSIS***

## DEFECT DETECTION:  STRENGTH DISTRIBUTION

***FIBER OPTICS CABLE ANALYSIS***

-   Distribution is linear in strength region of interest
-   30% of defects have strength < 0.5 lbs

## TRANSMISSION LOSS DATA

***FIBER OPTICS CABLE ANALYSIS***

## TRANSMISSION LOSS DISTRIBUTION

***FIBER OPTICS CABLE ANALYSIS***

-   Distribution is linear in optical loss region of interest
-   38% of defects have transmission loss < 1.5 dB

## OTHER POTENTIAL FAILURE CAUSES

***FIBER OPTICS CABLE ANALYSIS***

## RESULTS

***FIBER OPTICS CABLE ANALYSIS***

- For Lot A  (Fall / winter ‘96 vintage cables)

## CONCLUSIONS 

***FIBER OPTICS CABLE ANALYSIS***

- CONCLUSIONS

- RECOMMENDATIONS